Title:
COATED YARNS
United States Patent 3739567
Abstract:
Coated yarns suitable for use in woven piled fabrics comprising a synthetic organic polymeric base yarn, such as polyolefin, polyamide or polyester yarns, coated with a hot-melt synthetic resin adhesive composition comprising copolymers of ethylene with a vinyl ester of a carboxylic acid or with an alkyl acrylate or methacrylate, and wax. Process for the preparation of and woven piled fabrics made of such coated yarns are also provided.
US Patent References:
Fabrics
Stoll et al. - July 1964 - 3142109
Production of non-woven fiber webs stable to water
Jorder - November 1966 - 3288631
BONDED AND DYED FIBROUS SUBSTRATES AND PROCESSES
Anspon et al. - December 1969 - 3486929
Fabrics
Stoll et al. - July 1964 - 3142109
Production of non-woven fiber webs stable to water
Jorder - November 1966 - 3288631
BONDED AND DYED FIBROUS SUBSTRATES AND PROCESSES
Anspon et al. - December 1969 - 3486929
Application Number:
05/107839
Publication Date:
06/19/1973
Filing Date:
01/19/1971
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
428/395, 428/96, 428/394, 427/398.300, 57/907, 428/401, 427/358
International Classes:
D02G3/40; D06M13/02; D06M15/21; D06M15/267; D02G3/22; D06M13/00; D02G3/36
Field of Search:
28/73,75 57/14C,153,154,164,165 117/161UC,161UT,138.8E,138.8F,138.8N
Primary Examiner:
Schroeder, Werner H.
Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows
1. A yarn suitable for use in the production of woven piled fabrics comprising a synthetic base yarn coated with a hot-melt synthetic resin adhesive composition having a softening point substantially below that of said base yarn, said hot-melt synthetic resin adhesive composition comprising
2. The coated yarn of claim 1 wherein said base yarn is selected from the group consisting of polyolefin, polyamide and polyester yarns.
3. The coated yarn of claim 2 wherein said base yarn is polypropylene yarn.
4. The coated yarn of claim 2 wherein said base yarn is high density polyethylene.
5. The coated yarn of claim 2 wherein said base yarn is a multifilament yarn.
6. The coated yarn of claim 2 wherein said base yarn is a fibrillated high density polypropylene yarn.
7. The coated yarn of claim 6 wherein said base yarn has a density of from 0.88 to 0.92 g/cm3.
8. The coated yarn of claim 7 wherein the density is about 0.9 g/cm3.
9. The coated yarn of claim 2 wherein said base yarn has a denier of from 500 to 5000.
10. The coated yarn of claim 9 wherein the denier is from 1000 to 2500.
11. The coated yarn of claim 2 wherein said vinyl ester is vinyl acetate.
12. The coated yarn of claim 2 wherein said vinyl ester is selected from the group consisting of vinyl formate, vinyl propionate or vinyl butyrate.
13. The coated yarn of claim 2 wherein said acrylate or methacrylate is selected from the group consisting of ethyl acrylate, isobutyl acrylate or methyl methacrylate.
14. The coated yarn of claim 2 wherein said copolymer contains about 65-75 percent by weight of units derived from ethylene, about 25- 35 percent by weight of units derived from a vinyl ester or a C1 --C6 alkyl acrylate or methacrylate and a maximum of about 3 percent by weight of units derived from said further copolymerizable monomer.
15. The coated yarn of claim 2 wherein said copolymer has an inherent viscosity of about 0.45- 1.50.
16. The coated yarn of claim 2 wherein said composition contains about 40- 60 percent by weight of copolymer.
17. The coated yarn of claim 2 wherein said composition contains minor amounts of an adhesion improving thermoplastic resin other than an ethylene copolymer.
18. The coated yarn of claim 17 wherein said adhesion improving thermoplastic resin is selected from the group consisting of highly stabilized ester resins, polyterpene resins or rosin resins.
19. The coated yarn of claim 2 wherein said composition contains at least one additive selected from the group consisting of pigments, plasticizers, about 0.5 - 2 percent by weight of slip agent, about 0.0025 - 0.5 percent by weight of stabilizer, and a maximum of about 30 percent by weight of filler.
20. A process for the production of a yarn suitable for use in the production of woven piled fabrics which process comprises applying a coating of a hot-melt synthetic resin adhesive composition on to a synthetic organic polymeric yarn by passing a base yarn selected from the group consisting of polyolefin, polyamide and polyester yarns through a melt of an adhesive composition comprising
21. The process of claim 10 wherein about 350- 400 percent by weight of coating is applied to the base yarn and wherein excess adhesive composition is removed by passing the coated yarn through a die orifice and the coated yarn is cooled by passage through a water bath.
22. A woven piled fabric comprising a backing and a pile wherein at least one of the threads selected from the group consisting of warp, weft or stuffer threads is provided at least in part by a coated yarn as defined in claim 2.
23. The fabric of claim 22 wherein the pile is selected from the group consisting of wool, mixed wool and polyamide, polyester, acrylic, mixed wool and viscose rayon, polyamide, viscose rayon or polypropylene yarn.
24. The fabric of claim 23 wherein the adhesive composition on the coated yarn has been reactivated by heat.
25. The fabric of claim 24 in the form of a carpet.
26. The fabric of claim 24 in the form of a heavy-duty upholstery fabric.
1. A yarn suitable for use in the production of woven piled fabrics comprising a synthetic base yarn coated with a hot-melt synthetic resin adhesive composition having a softening point substantially below that of said base yarn, said hot-melt synthetic resin adhesive composition comprising
2. The coated yarn of claim 1 wherein said base yarn is selected from the group consisting of polyolefin, polyamide and polyester yarns.
3. The coated yarn of claim 2 wherein said base yarn is polypropylene yarn.
4. The coated yarn of claim 2 wherein said base yarn is high density polyethylene.
5. The coated yarn of claim 2 wherein said base yarn is a multifilament yarn.
6. The coated yarn of claim 2 wherein said base yarn is a fibrillated high density polypropylene yarn.
7. The coated yarn of claim 6 wherein said base yarn has a density of from 0.88 to 0.92 g/cm3.
8. The coated yarn of claim 7 wherein the density is about 0.9 g/cm3.
9. The coated yarn of claim 2 wherein said base yarn has a denier of from 500 to 5000.
10. The coated yarn of claim 9 wherein the denier is from 1000 to 2500.
11. The coated yarn of claim 2 wherein said vinyl ester is vinyl acetate.
12. The coated yarn of claim 2 wherein said vinyl ester is selected from the group consisting of vinyl formate, vinyl propionate or vinyl butyrate.
13. The coated yarn of claim 2 wherein said acrylate or methacrylate is selected from the group consisting of ethyl acrylate, isobutyl acrylate or methyl methacrylate.
14. The coated yarn of claim 2 wherein said copolymer contains about 65-75 percent by weight of units derived from ethylene, about 25- 35 percent by weight of units derived from a vinyl ester or a C1 --C6 alkyl acrylate or methacrylate and a maximum of about 3 percent by weight of units derived from said further copolymerizable monomer.
15. The coated yarn of claim 2 wherein said copolymer has an inherent viscosity of about 0.45- 1.50.
16. The coated yarn of claim 2 wherein said composition contains about 40- 60 percent by weight of copolymer.
17. The coated yarn of claim 2 wherein said composition contains minor amounts of an adhesion improving thermoplastic resin other than an ethylene copolymer.
18. The coated yarn of claim 17 wherein said adhesion improving thermoplastic resin is selected from the group consisting of highly stabilized ester resins, polyterpene resins or rosin resins.
19. The coated yarn of claim 2 wherein said composition contains at least one additive selected from the group consisting of pigments, plasticizers, about 0.5 - 2 percent by weight of slip agent, about 0.0025 - 0.5 percent by weight of stabilizer, and a maximum of about 30 percent by weight of filler.
20. A process for the production of a yarn suitable for use in the production of woven piled fabrics which process comprises applying a coating of a hot-melt synthetic resin adhesive composition on to a synthetic organic polymeric yarn by passing a base yarn selected from the group consisting of polyolefin, polyamide and polyester yarns through a melt of an adhesive composition comprising
21. The process of claim 10 wherein about 350- 400 percent by weight of coating is applied to the base yarn and wherein excess adhesive composition is removed by passing the coated yarn through a die orifice and the coated yarn is cooled by passage through a water bath.
22. A woven piled fabric comprising a backing and a pile wherein at least one of the threads selected from the group consisting of warp, weft or stuffer threads is provided at least in part by a coated yarn as defined in claim 2.
23. The fabric of claim 22 wherein the pile is selected from the group consisting of wool, mixed wool and polyamide, polyester, acrylic, mixed wool and viscose rayon, polyamide, viscose rayon or polypropylene yarn.
24. The fabric of claim 23 wherein the adhesive composition on the coated yarn has been reactivated by heat.
25. The fabric of claim 24 in the form of a carpet.
26. The fabric of claim 24 in the form of a heavy-duty upholstery fabric.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to woven piled fabrics such as carpets, heavy-duty upholstery fabrics and the like and to yarns for use in the weaving thereof.
2. Description of the Prior Art
Woven carpets such as Axminster and Wilton carpets are well known. They consist essentially of a backing comprising warp threads, weft or filling threads and if desired, stuffer threads to increase the stiffness of the backing, and a pile comprising tufts of yarn which pass under weft threads and are thereby locked into the backing. The warp, weft and stuffer threads have hitherto commonly been provided by jute yarn. The pile may, for example, be provided by yarns of wool, wool/nylon mixtures and wool/viscose rayon (e.g. wool/Evlan) mixtures.
One important factor in assessing the quality of a woven carpet is the so-called "tuft lock" of the pile, which is a measure of the force which must be applied in order to pull a tuft of pile from the backing. The higher the tuft lock, the more securely is the pile locked into the carpet backing and the better is the quality of the carpet in this respect.
There have been a number of proposals for improving the tuft lock of both Axminster and Wilton carpets. One such proposal involves sizing the woven carpet backing with an adhesive composition in the form of a latex. The wet latex is spread on to the back side of the carpet and penetrates to the sites where pile tufts are in contact with the warp, weft and/or stuffer threads of the backing. Upon subsequent heating to dry or cure the latex, the pile tufts are bonded to the warp, weft and/or stuffer threads of the backing and this results in a substantial increase in the tuft lock. This method does, however, have various disadvantages. It requires two additional steps of coating and drying or curing after completion of weaving. The improvement in tuft lock which can be achieved is limited, particularly as the sites of contact between pile tufts and warp, weft and/or stuffer threads are on the side of the backing away from the backing surface on to which the latex must be applied and the penetration of latex to these sites is as a result restricted. Also the application of an overall latex coating on to the backing forms an impervious layer which prevents the carpet breathing and consequently reduces the wearing quality of the carpet.
An alternative proposal involves coating the yarn which is to provide the weft thread of the carpet before weaving by immersing the yarn in a latex solution on its passage to the loom (see British Pat. No. 1,107,171). The latex is of such a consistency that setting does not take place until the completion of the weaving operation. The weft threads are selected for coating because it is these which principally are in intimate contact with the pile tufts in the woven carpet. A disadvantage of this process is, however, that it requires modification of the conventional machinery by incorporating means for immersing the yarn in a latex solution between the weft supply and the loom. The method is moreover difficult to operate satisfactorily in continuous production, and this has restricted its commercial success.
Heavy duty upholstery fabrics are also well known. Such fabrics generally consist of a backing comprising warp threads and weft threads and a pile comprising tufts of yarn which pass under weft threads and which are thereby locked into the backing. The pile may, for example, be provided by yarns of wool, wool/nylon mixtures and wool/viscose rayon mixtures and it may be in the form of either cut or uncut loops. A typical example of such an upholstery fabric is a moquette.
As with woven carpets, the so-called "tuft lock" of the pile of upholstery fabrics, either in the form of cut or uncut loops, is desirably high in order that the loops are as secure as possible in the woven structure. Similar difficulties thus occur with heavy duty upholstery fabrics as occur with woven carpets and methods of improving "tuft lock" are therefore desirable.
SUMMARY OF THE INVENTION
According to the present invention there is provided a yarn suitable for use in the production of woven piled fabrics which comprises a synthetic organic polymeric base yarn coated with a hot-melt synthetic resin adhesive composition having a softening point at a temperature substantially below the softening point of the synthetic organic polymeric yarn.
According to a further feature of the invention there is provided a process for the production of a yarn suitable for use in the production of woven piled fabrics which comprises applying a coating of hot-melt synthetic resin adhesive composition on to a synthetic organic polymeric yarn.
According to a stiff further feature of the present invention there is provided a woven piled fabric wherein the weft or filling, warp and/or stuffer threads are provided by a yarn of the present invention.
The use of a yarn coated with a hot-melt synthetic resin adhesive composition, in the production of woven piled fabrics generally provides a means of improving tuft lock and dimensional stability in the fabrics. The coated yarns may be used as warp threads, as stuffer threads (when present) or with particular advantage as weft threads. The fabric after weaving may be heated to reactivate the hot-melt composition and thereby bond the pile tufts into the woven structure.
Woven carpets according to the present invention not only have good tuft lock and dimensional stability but also, in general, have the advantage of good "cut and lay" properties such as are normally only associated with carpets having a secondary backing, e.g., of a latex foam.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based upon the discovery that woven piled fabrics such as woven carpets and heavy-duty upholstery fabrics with good tuft lock and good dimensional stability can be produced on conventional looms using synthetic organic polymeric yarns which have been pre-coated with a hot melt synthetic resin adhesive composition having a softening point substantially below that of the yarn.
The base yarns which may be pre-coated in accordance with the present invention are synthetic organic polymeric yarns such as, for example, polyolefin, polyamide and polyester yarns. Preferably a polyolefin yarn is used, and we have found that pre-coated high density ethylene and more especially propylene homopolymers and copolymers can be used with particular advantage. It is desirable that the yarn should be capable of carrying a relatively large amount of the adhesive composition so that sufficient adhesive is released by heat activation after weaving to provide good tuft lock. Multifilamentary yarns in general will carry and release larger amounts of adhesive composition than will monofilamentary yarns, and accordingly, multifilamentary yarns are preferred for use in the present invention. The ability to carry and release adhesive composition is similarly improved by fibrillation, and high density polypropylene yarn is readily available in fibrillated form. Preferably the polypropylene used has a density of from 0.88 to 0.92 gm/cm 3 , especially about 0.9 gm/cm 3 . A yarn which provides special advantages when used in the present invention is orientated fibrillated high density polypropylene yarn, e.g., "Cournova" yarn available from British Celanese and "Fibrite" C yarn available from Plasticizers Limited of Bradford, England.
The desired diameter of the yarn prior to coating depends to some extent on whether the yarn is to provide warp or weft threads or stuffer threads, or a combination of these, in the woven carpet. In any event, yarn having a denier in the range of from 500 to 5,000, particularly from 1,000 to 2,500, denier will conveniently be used. The present invention is applied with particular advantage to weft threads which principally come into intimate contact with the tuft pile, and for weft threads the denier of the uncoated yarn is with advantage from 1,000 to 1,500 denier. Similar deniers apply with advantage to warp threads but with stuffer threads the denier may with advantage be a little higher, for example, up to 2,000 denier.
The adhesive composition with which the yarn is coated in accordance with the present invention advantageously comprises (a) a copolymer of ethylene with an ester component, which component is a lower vinyl ester, lower acrylate and/or lower methacrylate; and if desired, additionally with one or more ethylenically unsaturated copolymerizable monomers and (b) a wax.
The term "copolymer" is used herein to indicate that polymer component (a) is a polymer of at least two monomers, namely ethylene and at least one of the named ester components and is intended to include terpolymers, etc.
The compositions used in the present invention are so-called "hot melt" adhesive compositions, i.e., adhesive compositions which have melt and flow properties intermediate between those of high molecular weight thermoplastic resins and low molecular weight, low viscosity materials such as waxes.
The ethylene copolymers discovered to be most useful in the present invention are ethylene copolymers with vinyl esters of lower (i.e., 1 to 6 carbon) carboxylic acids. Such ethylene/lower vinyl ester copolymers can be prepared by known techniques such as described, for example, in British Pat. Nos. 879,959, issued Jan. 31, 1962 and 911,527, issued Mar. 20, 1963. While an ethylene/vinyl acetate copolymer is preferred, other ethylene/lower vinyl ester copolymers such as those of vinyl formate, vinyl propionate and vinyl butyrate may be used. Additionally, ethylene copolymers with lower alkyl i.e., 1 to 6 carbon alkyl) esters of acrylic and methacrylic acid are also useful. Such lower acrylates and methacrylates include, e.g., ethyl acrylate, isobutyl acrylate and methyl methacrylate.
The ethylene copolymer conveniently contains from 60 to 85 percent by weight of units derived from ethylene and at least 15 percent by weight of units derived from vinyl acetate and/or other ester comonomers. Preferably the copolymer contains from 65 to 75 percent of ethylene units and from 35 to 25 percent by weight of vinyl acetate and/or other ester comonomer units, all percentages being based on the weight of the copolymer. The ethylene copolymer can, if desired, contain not more than 10 percent, advantageously not more than 3 percent, by weight of units derived from a further copolymerizable monomer such as acrylic acid, methacrylic acid, itaconic acid, acrylamide, β-dimethylamino-ethyl methacrylate, β-hydroxyethyl acrylate, diallyl maleate, diallyl phthalate, diallyl ether or ethylene glycol dimethacrylate. The inclusion of a further copolymerizable monomer such as one of those above improves adhesion of the adhesive composition to the base yarn.
An ethylene copolymer having an inherent viscosity of about 0.45 to 1.50 is usually preferred, the value being measured from a 0.25 percent solution of the copolymer in toluene at 86° F.
By variation in the copolymer component of the adhesive composition, the properties of the adhesive composition such as specific adhesion, flexibility and cohesion may be varied as desired. For example, in ethylene/vinyl acetate copolymers as the vinyl acetate content of the resin increases the specific adhesion and flexibility likewise increase. Compatibility with aliphatic hydrocarbons, however, decreases, and where, for example, the composition is to contain petroleum waxes this results in an optimum level for the vinyl acetate content. Mixtures of polymers, e.g., of ethylene/vinyl acetate copolymers can be used to advantage. For example, as shown in Example 1 hereinafter, a mixture of a high molecular weight grade copolymer having a high vinyl acetate content (which contributes good specific adhesion to the yarn and pile tufts) and a low molecular weight grade copolymer having a lower vinyl acetate content (which does not increase the viscosity of the composition to an unworkable extent) has been found to be especially suitable for use in the present invention.
The wax component of the adhesive compositions is selected to provide a composition having a suitable melting point for its intended use. Preferred waxes having a melting point of 120°- 220° F. include Fisher-Tropsch waxes and the hydrocarbon waxes obtained by the distillation of petroleum ("petroleum waxes") such as paraffin waxes (e.g., with melting points from 120° to 170° F.) and microcrystalline waxes. Candelilla and carnauba are also useful waxes, especially when they make up a minor proportion of the wax component.
If desired, the wax component can be a blend of high melting point petroleum waxes and low molecular weight polyolefin waxes wherein the polyolefin wax can, for example, be 5 to 25 percent or so percent by weight of the wax blend. Preferred low molecular weight polyolefin waxes are polyethylene waxes having a molecular weight of less than about 5,000 and melting points of 220° F. -250° F. Examples of polyethylene waxes which may be used are Polyethylene AC-8 (available from Allied Chemical Corporation, USA) and Polyethylene A 616 (available from Veba Chemie, Germany).
The proportional amounts of the ethylene copolymer and the wax present in the adhesive compositions are of importance. In general, the ethylene copolymer and the wax are present in amounts of from 10-90 percent and 90-10 percent respectively by weight of the composition. Preferably the composition will contain at least 20 percent, advantageously at least 30 percent, by weight of the ethylene copolymer with proportions of from 40 to 60 percent by weight being particularly desirable. Likewise the composition will preferably contain at least 20 percent, advantageously at least 30 percent, by weight of wax with proportions of from 40 to 60 percent again being particularly desirable.
The adhesive compositions according to the invention can, if desired, include components other than the ethylene copolymer and the wax although the ethylene copolymer and the wax together should desirably always provide the major proportion of the composition. For example, the composition may, if desired, contain a minor proportion of a thermoplastic resin other than the ethylene copolymer to improve the adhesive characteristics of the composition and to modify its mechanical properties. This further resin should have a melting point such that the adhesive composition as a whole has a suitable melting point for the desired purpose. Useful additional resins include, for example, highly stabilized ester resins (e.g., "Foral" 85 available from Hercules, Inc., USA) and the polyterpene resins obtained by distillation of conifers, e.g., "Piccolyte" S-85 available from Pennsylvania Industrial Chemical Corp., USA). The rosin family of resins (rosin and solid rosin derivatives) constitute a particularly useful class of resins, including such derivatives as esters of rosin and glycerol, esters of rosin and pentaerythritol, hydrogenated rosin, and esters of hydrogenated rosin and glycerol (e.g., "Staybelite" Ester 10 available from Hercules, Inc., USA) and pentaerythritol. Also useful are various coumarone-indene resins, permanently fusible phenolic resins, and petroleum hydrocarbon resins formed from dienes and reactive olefins via the deep cracking of petroleum. Typical useful petroleum hydrocarbon resins are "Piccopale" 85 and "Piccopale" 100 S both available from Pennsylvania Industrial Chemical Corporation, USA.
The composition with advantage will also contain a slip agent. In the weaving process, it is important that the pre-coated yarn according to the present invention should have the correct frictional properties, and these can be obtained by including slip agents in appropriate quantities depending upon the other components in the composition and the requirements of the particular weaving process to be used. Slip agents will generally be employed in amounts of about 0.5 to 2 percent by weight of the adhesive composition. Examples of suitable slip agents are "Armid" 0 (a long chain aliphatic amide available from Armour Chemicals Limited, England) and N,N'-dioleylethylenediamine (available as Carlisle 240 Wax from Carlisle Chemical Works Inc., USA).
A stabilizer can with advantage be incorporated into the composition to enhance its pot-life in molten form. Typical useful stabilizers or antitoxidants for the adhesive compositions include 2,4,6-trialkylated monohydroxy phenols, e.g., 2,4,6-tritertiarybutyl phenol and 2,6-di-tertiarybutyl-4-methyl phenol available from Shell Chemical under the trade mark "Ionox;" 4,4'-thio-bis (6-tertiary butyl m-cresol) available from Monsanto as "Santowhite" crystals; butylated hydroxytoluene (available under the trade mark "Tenox" from Eastman Chemical Co., USA and under the trade name "Dalpac" from Hercules Inc., USA) and butylated hydroxy-anisole. Effective proportions of stabilizer are generally in the range of from 25 parts per million to about 0.5 part per hundred parts by weight of the adhesive composition, preferably about 0.1 to 0.4 part per hundred parts by weight.
The adhesive composition may also, if desired, contain a filler in the form of a finely divided material that does not melt or decompose at the temperature of the molten adhesive. Suitable fillers include, for example, barium sulphate, calcium carbonate, talc, clay and silica. Fillers where present will, however, desirably only be used in small quantities, e.g., not more than 30 percent and preferably less than about 10 percent, by weight of the adhesive composition, as otherwise they may unduly reduce the bond strength and increase the viscosity of the compositions.
Other optional additives for the adhesive compositions include pigments and plasticizers.
In a convenient method for preparing the adhesive compositions, the lowest melting point component (usually the wax component) is melted in a suitable, uniformly heated mixing vessel followed by addition of the ethylene copolymer and stirring until the copolymer is thoroughly dispersed to provide a uniform homogeneous molten blend. Any other components of the composition are then added followed by further agitation to form a homogeneous mass.
After blending, the composition may, if desired, be fed to an intermediate heated storage tank where it can be maintained in molten from until required for use. Alternatively, it may be fed directly to coating apparatus for application on to the yarn. A further possibility is to allow the composition after blending to cool and solidify, and in this case the composition will have to be re-melted prior to use.
The yarn is conveniently coated with the adhesive composition by passage through a bath containing the composition in molten form followed by metering, e.g., by passage through a restricted die orifice in the base of the vessel containing the bath, cooling and rewinding of the coated yarn. The yarn to be coated can be fed from a conventional package (e.g., a "cheese") downwards through a bath of the molten adhesive composition. The molten adhesive composition in the bath through which the yarn passes should be maintained at as uniform a temperature as possible in order that the viscosity of the composition in the bath is maintained reasonably constant. If the viscosity varies significantly, this can effect the uniformity in the coating weight applied to the yarn. The molten adhesive composition can thus, for example, advantageously be contained in a heat jacketed tank. It has been found preferable to use a tank containing a depth of from 3 to 9 ins. of molten adhesive composition. The yarn can be drawn through the bath by a winding unit which should provide a reasonably constant linear yarn speed in order that a reasonably uniform coating weight can be applied on to the yarn for any given combination of die orifice and yarn diameter. A convenient yarn speed through the bath has been found to be about 600 ft. per minute, although the speed, if desired, can be reduced to almost zero or increased up to 1,200 ft. per minute or even higher.
The temperature of the molten adhesive composition which is conveniently used for coating depends upon the yarn to be coated and the ingredients of the adhesive composition. The melting point of polypropylene is about 150° C., and therefore, when polypropylene yarn is to be coated the temperature of the bath must be substantially below this temperature. Indeed, it has been found that the use of temperatures above about 130° C. causes difficulties due to shrinkage of the polypropylene yarn. Theoretically, high temperatures above about 130° C. could be utilized by passing the yarn rapidly through the bath so that its temperature never reaches the temperature of the bath. However, this creates difficulty in practice particularly where for some reason a stoppage occurs leaving yarn stationary in the bath. When coating polypropylene, bath temperatures not in excess of 130° C. are thus desirably used.
The minimum desired coating temperature depends upon the ingredients and particularly upon the softening point of the adhesive composition. If the coating temperature is too low and is thus too near to the softening point of the particular adhesive composition in use, the flow of the melt will be inadequate and this can result in a lumpy coating and reduced adhesion. Conveniently the ingredients of the adhesive composition are selected to provide a softening point in the range of 50°-100° C., preferably 65°-90° C. Advantageously the softening point is about 85° C. Using adhesive compositions of this sort to coat polypropylene yarn, bath temperatures of 110° to 120° C. are particularly suitable.
The yarn conveniently passes downwards through the bath of molten adhesive composition and out at the bottom of the bath through a die which, as above described, meters the quantity of composition applied. The metering die thus ensures a coated yarn of smooth and uniform cross-section.
The yarn is next cooled, e.g., by passage through a water bath. The water in the bath can conveniently be at ambient temperatures, and the purpose of the water bath is to solidify the adhesive composition. After passage through the bath excess water can be removed, for example, by withdrawing the yarn from the bath at a sharp angle to throw off excess water, by wiping and/or by a blast of compressed air. The coated thread is then wound on to packages, and in one convenient arrangement the package winder serves also to draw the yarn through the coating unit.
The amount of adhesive composition applied to the yarn is conveniently in the range of from 150 to 1000 percent by weight of the uncoated yarn. The lower limit is provided by the need for there to be sufficient adhesive composition carried on the yarn after weaving and reactivation to firmly bond the tuft pile. The upper limit is determined principally by the need for a suitable degree of yarn flexibility and a suitable overall yarn diameter in the subsequent weaving operations. Preferably the amount of adhesive composition applied is from 250 to 750 percent by weight, and advantageously from 350 to 400 percent by weight, of the uncoated yarn.
The essential weaving technology remains unchanged with substitution of the yarns according to the invention for the jute yarns which have hitherto commonly been used as warp threads, weft threads and stuffer threads. The yarns according to the present invention can be used with particular advantage as weft threads, if desired in combination with jute warp and stuffer threads. Alternatively, if desired, the warp and/or stuffer threads as well as the weft threads can be provided with coatings according to the invention. Although no modification of weaving looms is required, a degree of tuning of the loom may be necessary to accommodate the changed frictional and elastic properties of the yarns according to the invention as compared with conventional jute yarns. The physical dimensions and surface frictional properties of yarns are important and can affect weaving at tension points and points where the thread is required to run evenly through the mechanism. The diameter of yarns according to the invention can be controlled by selecting yarn of an appropriate denier and controlling the amount of adhesive composition applied as indicated above. The frictional properties of the yarn can be controlled by incorporation of slip agents, again as described above, to help prevent them from being tacky.
The yarns according to the invention can be used with any convenient pile fibers. They are, for example, suitable for use with pile fibers of wool, mixtures of wool and polyamide, e.g., nylon, polyester, acrylic, mixtures of wool and viscose rayon, e.g., Evlan, pure polyamide, e.g., nylon, pure viscose rayon, e.g., Evlan and polypropylene.
After weaving, the adhesive composition is reactivated by heat. The heating may be effected in any convenient way, for example, using reactivating ovens, radiant heaters and hot air blowers as the heat source. The heating is preferably effected after removal of the woven fabric from the loom. It is also possible, though less advantageous, to use, for example, radiant bars or hot air blowers in association with the loom whereby woven areas of the fabric are heated to reactivate the adhesive composition before removal of the carpet from the loom.
As in the process for coating the yarn, the temperatures used for reactivation will depend upon the yarns in the woven fabric and the ingredients of the adhesive composition. With coated polypropylene yarns, the temperature of the yarn should not be raised above about 130° C. On the other hand, the temperature must be raised sufficiently to cause adequate flow of the adhesive composition to bind the pile tufts. Preferably heating will be effected to raise the temperature of the adhesive composition to from 100° to 120° C. where polypropylene yarns coated with a composition having a softening point of from 65° to 85° C. have been used.
The length of time for which heating is effected may also be of importance. If heating is continued for too long, excessive migration of the adhesive composition from the yarn threads into the pile fibers may occur and this can result in reduced adhesion and also excessive stiffness of the woven fabric. Using a reactivation oven at 120°C., a residence time of about 5 minutes has been found to be adequate with adhesive compositions having a softening point of about 85° C. With radiant heating, e.g., using infra-red heaters, longer heating may be necessary particularly with thick carpets where the heat can take longer to penetrate. For this reason, infra-red heaters are not ideal for thick carpets. Better penetration will be obtained using hot air blowers.
The following Examples illustrate the production of yarns in accordance with the present invention. In these Examples the following ethylene copolymers are used:
Copolymer "A" -- Ethylene/vinyl acetate copolymer (by weight 67:33 ethylene:vinyl acetate) having a melt index of 25 (g/10 min ASTM D-1238 modified), an inherent viscosity of 0.78 (0.25 percent in toluene at 30° C.), and a softening point of 240° F. (ring and ball)
Copolymer "B" -- Ethylene/vinyl acetate copolymer (by weight 72:28 ethylene:vinyl acetate) having a melt index of 400, an inherent viscosity of 0.59 and a softening point of 180° F.
Copolymer "C" -- Ethylene/vinyl acetate/methacrylic acid terpolymer (by weight 71:28:1 ethylene:vinyl acetate:methacrylic acid) having an acid number of 6 (mg potassium hydroxide per gram polymer), a melt index of 6, an inherent viscosity of 0.87, and a softening point of 316° F.
Copolymer "D" -- Ethylene/vinyl acetate/methacrylic acid terpolymer (by weight 74:25:1 ethylene:vinyl acetate:methacrylic acid) having an acid number of 6, a melt index of 150, an inherent viscosity of 0.77 and a softening point of 195° F.
Copolymer "E" -- Ethylene/vinyl acetate copolymer (by weight 72:28 ethylene:vinyl acetate: having a melt index of 6, an inherent viscosity of 0.94 and a softening point of 310° F.
EXAMPLE 1
Adhesive Composition % by weight Copolymer "A" 20.0 Copolymer "B" 35.0 Microcrystalline wax (M.pt. 180°F.) 33.9 Paraffin wax (M.pt. 160°F.) 10.0 "Armid" O Slip Agent 1.0 "Tenox" BHT Antioxidant 0.1 100.0
Blending of Ingredients
The waxes are melted in a heated blending tank, and the BHT antioxidant is added. The mixture is then heated to 160° C. with stirring to form a homogeneous mass. The A and B copolymers and slip agent are then added with vigorous stirring and stirring is continued first at high speed and then at lower speeds until a homogenous composition is obtained.
Orientated fibrillated high density polypropylene yarn (1,000 denier "Cournova" of British Celanese) is coated with 350- 400 percent by weight (based on the weight of uncoated yarn) of the adhesive composition to provide a yarn in accordance with the present invention.
EXAMPLE 2
Adhesive Composition % by weight Copolymer "C" 15.0 Copolymer "D" 35.0 Paraffin wax (M.pt. 135°F.) 44.9 Polyethylene A 616 (low molecular weight polyethylene of Veba Chemie, Germany) 4.0 "Armid" O Slip Agent 1.0 "Tenox" BHT Antioxidant 0.1 100.0
The ingredients are blended as described in Example 1.
1,000 Denier "Cournova" yarn is coated with 350- 400 percent by weight (based on the weight of uncoated yarn) of the above composition to provide a yarn in accordance with the present invention.
EXAMPLE 3
Adhesive Composition % by weight Copolymer "A" 25.0 Copolymer "B" 25.0 Microcrystalline wax (M.pt. 180°F.) 30.0 "Foral" 85 (highly stabilized ester resin of Hercules Inc., USA) 18.4 "Armid" O Slip Agent 1.5 "Tenox" BHT Antioxidant 0.1 100.0
The ingredients are blended as described in Example 1.
1,000 Denier "Cournova" yarn is coated with 350- 400 percent by weight (based on the weight of uncoated yarn) of the above composition to provide a yarn in accordance with the present invention.
EXAMPLE 4
Adhesive Composition % by weight Copolymer "E" 30.0 Piccolyte S-85 (Polyterpene resin of Pennsylvania Industrial Chemical Corp., USA) 20.0 Microcrystalline wax (M.pt. 180°F.) 30.0 Paraffin wax (M.pt. 160°F.) 18.4 "Armid" O Slip Agent 1.5 "Tenox" BHT Antioxidant 0.1 100.0
The ingredients are blended as described in Example 1.
1,000 Denier "Cournova" yarn is coated with 350- 400 percent by weight (based on the weight of uncoated yarn) of the above composition to provide a yarn in accordance with the present invention.
EXAMPLE 5
The yarns of Examples 1 to 4 are used as weft threads in the weaving of Axminster and Wilton carpets on conventional looms and after reactivation of the adhesive by heating in a reactivation oven at 120° C. for 5 minutes provide carpets having excellent physical properties. The carpets in particular have good tuft lock and dimensional stability, and also have the additional advantage that there is a reduced tendency to fray at the edges.
Comparative experiments have been carried out to illustrate the good tuft lock obtainable in carpets made of all wool pile fibers using yarns according to the present invention as weft threads. A yarn produced in accordance with Example 1 was woven as weft thread together with jute warp and without stuffer threads into an Axminster carpet (6 shots per inch) and the adhesive composition then reactivated by heating in a reactivation oven at 120° C. for 5 minutes. The tuft lock (measured by means of the Wool Industry Research Association Tuft Pull Tester) was 1950 grams. Similarly, using yarn coated with 475° percent weight (based on the uncoated weight of the yarn) of adhesive composition as described in Example 1 except for a reduction to 0.25 percent in the amount of slip agent, the following results for tuft lock were obtained with various residence times in a reactivation oven at 110° C.
residence time in min. Tuft lock in grams 5 940 7 1866 9 1874 11 2300
By comparison, Axminster carpets of the same type but incorporating jute weft threads and back-sized with a typical latex composition, after weaving showed an average tuft lock of 624 gms (range of 600- 700 grams).
Similar experiments have been carried out using 1,000 denier "Cournova" yarn coated with the adhesive composition of Example 2 at different coating weights. The results were as follows:
a. An Axminster carpet produced using yarn coated with 500- 550 percent by weight of the adhesive composition of Example 2 as weft thread and reactivated for about 5 minutes at about 120° C. had an average tuft lock of about 2490 grams.
b. A Wilton carpet produced using yarn coated with 910 percent by weight of the adhesive composition of Example 2 as weft thread and reactivated for about 5 minutes at about 120° C. had an average tuft lock of about 665 grams.
Similar results are obtainable with the coated yarns of Examples 3 and 4.
By comparison, a Wilton carpet incorporating jute weft threads and back-sized with a typical latex composition after weaving commonly has a tuft lock of less than 400 grams (usually about 250 grams). A Wilton carpet with no latex back-sizing commonly has a tuft lock of less than about 200 grams.
1. Field of the Invention
This invention relates to woven piled fabrics such as carpets, heavy-duty upholstery fabrics and the like and to yarns for use in the weaving thereof.
2. Description of the Prior Art
Woven carpets such as Axminster and Wilton carpets are well known. They consist essentially of a backing comprising warp threads, weft or filling threads and if desired, stuffer threads to increase the stiffness of the backing, and a pile comprising tufts of yarn which pass under weft threads and are thereby locked into the backing. The warp, weft and stuffer threads have hitherto commonly been provided by jute yarn. The pile may, for example, be provided by yarns of wool, wool/nylon mixtures and wool/viscose rayon (e.g. wool/Evlan) mixtures.
One important factor in assessing the quality of a woven carpet is the so-called "tuft lock" of the pile, which is a measure of the force which must be applied in order to pull a tuft of pile from the backing. The higher the tuft lock, the more securely is the pile locked into the carpet backing and the better is the quality of the carpet in this respect.
There have been a number of proposals for improving the tuft lock of both Axminster and Wilton carpets. One such proposal involves sizing the woven carpet backing with an adhesive composition in the form of a latex. The wet latex is spread on to the back side of the carpet and penetrates to the sites where pile tufts are in contact with the warp, weft and/or stuffer threads of the backing. Upon subsequent heating to dry or cure the latex, the pile tufts are bonded to the warp, weft and/or stuffer threads of the backing and this results in a substantial increase in the tuft lock. This method does, however, have various disadvantages. It requires two additional steps of coating and drying or curing after completion of weaving. The improvement in tuft lock which can be achieved is limited, particularly as the sites of contact between pile tufts and warp, weft and/or stuffer threads are on the side of the backing away from the backing surface on to which the latex must be applied and the penetration of latex to these sites is as a result restricted. Also the application of an overall latex coating on to the backing forms an impervious layer which prevents the carpet breathing and consequently reduces the wearing quality of the carpet.
An alternative proposal involves coating the yarn which is to provide the weft thread of the carpet before weaving by immersing the yarn in a latex solution on its passage to the loom (see British Pat. No. 1,107,171). The latex is of such a consistency that setting does not take place until the completion of the weaving operation. The weft threads are selected for coating because it is these which principally are in intimate contact with the pile tufts in the woven carpet. A disadvantage of this process is, however, that it requires modification of the conventional machinery by incorporating means for immersing the yarn in a latex solution between the weft supply and the loom. The method is moreover difficult to operate satisfactorily in continuous production, and this has restricted its commercial success.
Heavy duty upholstery fabrics are also well known. Such fabrics generally consist of a backing comprising warp threads and weft threads and a pile comprising tufts of yarn which pass under weft threads and which are thereby locked into the backing. The pile may, for example, be provided by yarns of wool, wool/nylon mixtures and wool/viscose rayon mixtures and it may be in the form of either cut or uncut loops. A typical example of such an upholstery fabric is a moquette.
As with woven carpets, the so-called "tuft lock" of the pile of upholstery fabrics, either in the form of cut or uncut loops, is desirably high in order that the loops are as secure as possible in the woven structure. Similar difficulties thus occur with heavy duty upholstery fabrics as occur with woven carpets and methods of improving "tuft lock" are therefore desirable.
SUMMARY OF THE INVENTION
According to the present invention there is provided a yarn suitable for use in the production of woven piled fabrics which comprises a synthetic organic polymeric base yarn coated with a hot-melt synthetic resin adhesive composition having a softening point at a temperature substantially below the softening point of the synthetic organic polymeric yarn.
According to a further feature of the invention there is provided a process for the production of a yarn suitable for use in the production of woven piled fabrics which comprises applying a coating of hot-melt synthetic resin adhesive composition on to a synthetic organic polymeric yarn.
According to a stiff further feature of the present invention there is provided a woven piled fabric wherein the weft or filling, warp and/or stuffer threads are provided by a yarn of the present invention.
The use of a yarn coated with a hot-melt synthetic resin adhesive composition, in the production of woven piled fabrics generally provides a means of improving tuft lock and dimensional stability in the fabrics. The coated yarns may be used as warp threads, as stuffer threads (when present) or with particular advantage as weft threads. The fabric after weaving may be heated to reactivate the hot-melt composition and thereby bond the pile tufts into the woven structure.
Woven carpets according to the present invention not only have good tuft lock and dimensional stability but also, in general, have the advantage of good "cut and lay" properties such as are normally only associated with carpets having a secondary backing, e.g., of a latex foam.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based upon the discovery that woven piled fabrics such as woven carpets and heavy-duty upholstery fabrics with good tuft lock and good dimensional stability can be produced on conventional looms using synthetic organic polymeric yarns which have been pre-coated with a hot melt synthetic resin adhesive composition having a softening point substantially below that of the yarn.
The base yarns which may be pre-coated in accordance with the present invention are synthetic organic polymeric yarns such as, for example, polyolefin, polyamide and polyester yarns. Preferably a polyolefin yarn is used, and we have found that pre-coated high density ethylene and more especially propylene homopolymers and copolymers can be used with particular advantage. It is desirable that the yarn should be capable of carrying a relatively large amount of the adhesive composition so that sufficient adhesive is released by heat activation after weaving to provide good tuft lock. Multifilamentary yarns in general will carry and release larger amounts of adhesive composition than will monofilamentary yarns, and accordingly, multifilamentary yarns are preferred for use in the present invention. The ability to carry and release adhesive composition is similarly improved by fibrillation, and high density polypropylene yarn is readily available in fibrillated form. Preferably the polypropylene used has a density of from 0.88 to 0.92 gm/cm 3 , especially about 0.9 gm/cm 3 . A yarn which provides special advantages when used in the present invention is orientated fibrillated high density polypropylene yarn, e.g., "Cournova" yarn available from British Celanese and "Fibrite" C yarn available from Plasticizers Limited of Bradford, England.
The desired diameter of the yarn prior to coating depends to some extent on whether the yarn is to provide warp or weft threads or stuffer threads, or a combination of these, in the woven carpet. In any event, yarn having a denier in the range of from 500 to 5,000, particularly from 1,000 to 2,500, denier will conveniently be used. The present invention is applied with particular advantage to weft threads which principally come into intimate contact with the tuft pile, and for weft threads the denier of the uncoated yarn is with advantage from 1,000 to 1,500 denier. Similar deniers apply with advantage to warp threads but with stuffer threads the denier may with advantage be a little higher, for example, up to 2,000 denier.
The adhesive composition with which the yarn is coated in accordance with the present invention advantageously comprises (a) a copolymer of ethylene with an ester component, which component is a lower vinyl ester, lower acrylate and/or lower methacrylate; and if desired, additionally with one or more ethylenically unsaturated copolymerizable monomers and (b) a wax.
The term "copolymer" is used herein to indicate that polymer component (a) is a polymer of at least two monomers, namely ethylene and at least one of the named ester components and is intended to include terpolymers, etc.
The compositions used in the present invention are so-called "hot melt" adhesive compositions, i.e., adhesive compositions which have melt and flow properties intermediate between those of high molecular weight thermoplastic resins and low molecular weight, low viscosity materials such as waxes.
The ethylene copolymers discovered to be most useful in the present invention are ethylene copolymers with vinyl esters of lower (i.e., 1 to 6 carbon) carboxylic acids. Such ethylene/lower vinyl ester copolymers can be prepared by known techniques such as described, for example, in British Pat. Nos. 879,959, issued Jan. 31, 1962 and 911,527, issued Mar. 20, 1963. While an ethylene/vinyl acetate copolymer is preferred, other ethylene/lower vinyl ester copolymers such as those of vinyl formate, vinyl propionate and vinyl butyrate may be used. Additionally, ethylene copolymers with lower alkyl i.e., 1 to 6 carbon alkyl) esters of acrylic and methacrylic acid are also useful. Such lower acrylates and methacrylates include, e.g., ethyl acrylate, isobutyl acrylate and methyl methacrylate.
The ethylene copolymer conveniently contains from 60 to 85 percent by weight of units derived from ethylene and at least 15 percent by weight of units derived from vinyl acetate and/or other ester comonomers. Preferably the copolymer contains from 65 to 75 percent of ethylene units and from 35 to 25 percent by weight of vinyl acetate and/or other ester comonomer units, all percentages being based on the weight of the copolymer. The ethylene copolymer can, if desired, contain not more than 10 percent, advantageously not more than 3 percent, by weight of units derived from a further copolymerizable monomer such as acrylic acid, methacrylic acid, itaconic acid, acrylamide, β-dimethylamino-ethyl methacrylate, β-hydroxyethyl acrylate, diallyl maleate, diallyl phthalate, diallyl ether or ethylene glycol dimethacrylate. The inclusion of a further copolymerizable monomer such as one of those above improves adhesion of the adhesive composition to the base yarn.
An ethylene copolymer having an inherent viscosity of about 0.45 to 1.50 is usually preferred, the value being measured from a 0.25 percent solution of the copolymer in toluene at 86° F.
By variation in the copolymer component of the adhesive composition, the properties of the adhesive composition such as specific adhesion, flexibility and cohesion may be varied as desired. For example, in ethylene/vinyl acetate copolymers as the vinyl acetate content of the resin increases the specific adhesion and flexibility likewise increase. Compatibility with aliphatic hydrocarbons, however, decreases, and where, for example, the composition is to contain petroleum waxes this results in an optimum level for the vinyl acetate content. Mixtures of polymers, e.g., of ethylene/vinyl acetate copolymers can be used to advantage. For example, as shown in Example 1 hereinafter, a mixture of a high molecular weight grade copolymer having a high vinyl acetate content (which contributes good specific adhesion to the yarn and pile tufts) and a low molecular weight grade copolymer having a lower vinyl acetate content (which does not increase the viscosity of the composition to an unworkable extent) has been found to be especially suitable for use in the present invention.
The wax component of the adhesive compositions is selected to provide a composition having a suitable melting point for its intended use. Preferred waxes having a melting point of 120°- 220° F. include Fisher-Tropsch waxes and the hydrocarbon waxes obtained by the distillation of petroleum ("petroleum waxes") such as paraffin waxes (e.g., with melting points from 120° to 170° F.) and microcrystalline waxes. Candelilla and carnauba are also useful waxes, especially when they make up a minor proportion of the wax component.
If desired, the wax component can be a blend of high melting point petroleum waxes and low molecular weight polyolefin waxes wherein the polyolefin wax can, for example, be 5 to 25 percent or so percent by weight of the wax blend. Preferred low molecular weight polyolefin waxes are polyethylene waxes having a molecular weight of less than about 5,000 and melting points of 220° F. -250° F. Examples of polyethylene waxes which may be used are Polyethylene AC-8 (available from Allied Chemical Corporation, USA) and Polyethylene A 616 (available from Veba Chemie, Germany).
The proportional amounts of the ethylene copolymer and the wax present in the adhesive compositions are of importance. In general, the ethylene copolymer and the wax are present in amounts of from 10-90 percent and 90-10 percent respectively by weight of the composition. Preferably the composition will contain at least 20 percent, advantageously at least 30 percent, by weight of the ethylene copolymer with proportions of from 40 to 60 percent by weight being particularly desirable. Likewise the composition will preferably contain at least 20 percent, advantageously at least 30 percent, by weight of wax with proportions of from 40 to 60 percent again being particularly desirable.
The adhesive compositions according to the invention can, if desired, include components other than the ethylene copolymer and the wax although the ethylene copolymer and the wax together should desirably always provide the major proportion of the composition. For example, the composition may, if desired, contain a minor proportion of a thermoplastic resin other than the ethylene copolymer to improve the adhesive characteristics of the composition and to modify its mechanical properties. This further resin should have a melting point such that the adhesive composition as a whole has a suitable melting point for the desired purpose. Useful additional resins include, for example, highly stabilized ester resins (e.g., "Foral" 85 available from Hercules, Inc., USA) and the polyterpene resins obtained by distillation of conifers, e.g., "Piccolyte" S-85 available from Pennsylvania Industrial Chemical Corp., USA). The rosin family of resins (rosin and solid rosin derivatives) constitute a particularly useful class of resins, including such derivatives as esters of rosin and glycerol, esters of rosin and pentaerythritol, hydrogenated rosin, and esters of hydrogenated rosin and glycerol (e.g., "Staybelite" Ester 10 available from Hercules, Inc., USA) and pentaerythritol. Also useful are various coumarone-indene resins, permanently fusible phenolic resins, and petroleum hydrocarbon resins formed from dienes and reactive olefins via the deep cracking of petroleum. Typical useful petroleum hydrocarbon resins are "Piccopale" 85 and "Piccopale" 100 S both available from Pennsylvania Industrial Chemical Corporation, USA.
The composition with advantage will also contain a slip agent. In the weaving process, it is important that the pre-coated yarn according to the present invention should have the correct frictional properties, and these can be obtained by including slip agents in appropriate quantities depending upon the other components in the composition and the requirements of the particular weaving process to be used. Slip agents will generally be employed in amounts of about 0.5 to 2 percent by weight of the adhesive composition. Examples of suitable slip agents are "Armid" 0 (a long chain aliphatic amide available from Armour Chemicals Limited, England) and N,N'-dioleylethylenediamine (available as Carlisle 240 Wax from Carlisle Chemical Works Inc., USA).
A stabilizer can with advantage be incorporated into the composition to enhance its pot-life in molten form. Typical useful stabilizers or antitoxidants for the adhesive compositions include 2,4,6-trialkylated monohydroxy phenols, e.g., 2,4,6-tritertiarybutyl phenol and 2,6-di-tertiarybutyl-4-methyl phenol available from Shell Chemical under the trade mark "Ionox;" 4,4'-thio-bis (6-tertiary butyl m-cresol) available from Monsanto as "Santowhite" crystals; butylated hydroxytoluene (available under the trade mark "Tenox" from Eastman Chemical Co., USA and under the trade name "Dalpac" from Hercules Inc., USA) and butylated hydroxy-anisole. Effective proportions of stabilizer are generally in the range of from 25 parts per million to about 0.5 part per hundred parts by weight of the adhesive composition, preferably about 0.1 to 0.4 part per hundred parts by weight.
The adhesive composition may also, if desired, contain a filler in the form of a finely divided material that does not melt or decompose at the temperature of the molten adhesive. Suitable fillers include, for example, barium sulphate, calcium carbonate, talc, clay and silica. Fillers where present will, however, desirably only be used in small quantities, e.g., not more than 30 percent and preferably less than about 10 percent, by weight of the adhesive composition, as otherwise they may unduly reduce the bond strength and increase the viscosity of the compositions.
Other optional additives for the adhesive compositions include pigments and plasticizers.
In a convenient method for preparing the adhesive compositions, the lowest melting point component (usually the wax component) is melted in a suitable, uniformly heated mixing vessel followed by addition of the ethylene copolymer and stirring until the copolymer is thoroughly dispersed to provide a uniform homogeneous molten blend. Any other components of the composition are then added followed by further agitation to form a homogeneous mass.
After blending, the composition may, if desired, be fed to an intermediate heated storage tank where it can be maintained in molten from until required for use. Alternatively, it may be fed directly to coating apparatus for application on to the yarn. A further possibility is to allow the composition after blending to cool and solidify, and in this case the composition will have to be re-melted prior to use.
The yarn is conveniently coated with the adhesive composition by passage through a bath containing the composition in molten form followed by metering, e.g., by passage through a restricted die orifice in the base of the vessel containing the bath, cooling and rewinding of the coated yarn. The yarn to be coated can be fed from a conventional package (e.g., a "cheese") downwards through a bath of the molten adhesive composition. The molten adhesive composition in the bath through which the yarn passes should be maintained at as uniform a temperature as possible in order that the viscosity of the composition in the bath is maintained reasonably constant. If the viscosity varies significantly, this can effect the uniformity in the coating weight applied to the yarn. The molten adhesive composition can thus, for example, advantageously be contained in a heat jacketed tank. It has been found preferable to use a tank containing a depth of from 3 to 9 ins. of molten adhesive composition. The yarn can be drawn through the bath by a winding unit which should provide a reasonably constant linear yarn speed in order that a reasonably uniform coating weight can be applied on to the yarn for any given combination of die orifice and yarn diameter. A convenient yarn speed through the bath has been found to be about 600 ft. per minute, although the speed, if desired, can be reduced to almost zero or increased up to 1,200 ft. per minute or even higher.
The temperature of the molten adhesive composition which is conveniently used for coating depends upon the yarn to be coated and the ingredients of the adhesive composition. The melting point of polypropylene is about 150° C., and therefore, when polypropylene yarn is to be coated the temperature of the bath must be substantially below this temperature. Indeed, it has been found that the use of temperatures above about 130° C. causes difficulties due to shrinkage of the polypropylene yarn. Theoretically, high temperatures above about 130° C. could be utilized by passing the yarn rapidly through the bath so that its temperature never reaches the temperature of the bath. However, this creates difficulty in practice particularly where for some reason a stoppage occurs leaving yarn stationary in the bath. When coating polypropylene, bath temperatures not in excess of 130° C. are thus desirably used.
The minimum desired coating temperature depends upon the ingredients and particularly upon the softening point of the adhesive composition. If the coating temperature is too low and is thus too near to the softening point of the particular adhesive composition in use, the flow of the melt will be inadequate and this can result in a lumpy coating and reduced adhesion. Conveniently the ingredients of the adhesive composition are selected to provide a softening point in the range of 50°-100° C., preferably 65°-90° C. Advantageously the softening point is about 85° C. Using adhesive compositions of this sort to coat polypropylene yarn, bath temperatures of 110° to 120° C. are particularly suitable.
The yarn conveniently passes downwards through the bath of molten adhesive composition and out at the bottom of the bath through a die which, as above described, meters the quantity of composition applied. The metering die thus ensures a coated yarn of smooth and uniform cross-section.
The yarn is next cooled, e.g., by passage through a water bath. The water in the bath can conveniently be at ambient temperatures, and the purpose of the water bath is to solidify the adhesive composition. After passage through the bath excess water can be removed, for example, by withdrawing the yarn from the bath at a sharp angle to throw off excess water, by wiping and/or by a blast of compressed air. The coated thread is then wound on to packages, and in one convenient arrangement the package winder serves also to draw the yarn through the coating unit.
The amount of adhesive composition applied to the yarn is conveniently in the range of from 150 to 1000 percent by weight of the uncoated yarn. The lower limit is provided by the need for there to be sufficient adhesive composition carried on the yarn after weaving and reactivation to firmly bond the tuft pile. The upper limit is determined principally by the need for a suitable degree of yarn flexibility and a suitable overall yarn diameter in the subsequent weaving operations. Preferably the amount of adhesive composition applied is from 250 to 750 percent by weight, and advantageously from 350 to 400 percent by weight, of the uncoated yarn.
The essential weaving technology remains unchanged with substitution of the yarns according to the invention for the jute yarns which have hitherto commonly been used as warp threads, weft threads and stuffer threads. The yarns according to the present invention can be used with particular advantage as weft threads, if desired in combination with jute warp and stuffer threads. Alternatively, if desired, the warp and/or stuffer threads as well as the weft threads can be provided with coatings according to the invention. Although no modification of weaving looms is required, a degree of tuning of the loom may be necessary to accommodate the changed frictional and elastic properties of the yarns according to the invention as compared with conventional jute yarns. The physical dimensions and surface frictional properties of yarns are important and can affect weaving at tension points and points where the thread is required to run evenly through the mechanism. The diameter of yarns according to the invention can be controlled by selecting yarn of an appropriate denier and controlling the amount of adhesive composition applied as indicated above. The frictional properties of the yarn can be controlled by incorporation of slip agents, again as described above, to help prevent them from being tacky.
The yarns according to the invention can be used with any convenient pile fibers. They are, for example, suitable for use with pile fibers of wool, mixtures of wool and polyamide, e.g., nylon, polyester, acrylic, mixtures of wool and viscose rayon, e.g., Evlan, pure polyamide, e.g., nylon, pure viscose rayon, e.g., Evlan and polypropylene.
After weaving, the adhesive composition is reactivated by heat. The heating may be effected in any convenient way, for example, using reactivating ovens, radiant heaters and hot air blowers as the heat source. The heating is preferably effected after removal of the woven fabric from the loom. It is also possible, though less advantageous, to use, for example, radiant bars or hot air blowers in association with the loom whereby woven areas of the fabric are heated to reactivate the adhesive composition before removal of the carpet from the loom.
As in the process for coating the yarn, the temperatures used for reactivation will depend upon the yarns in the woven fabric and the ingredients of the adhesive composition. With coated polypropylene yarns, the temperature of the yarn should not be raised above about 130° C. On the other hand, the temperature must be raised sufficiently to cause adequate flow of the adhesive composition to bind the pile tufts. Preferably heating will be effected to raise the temperature of the adhesive composition to from 100° to 120° C. where polypropylene yarns coated with a composition having a softening point of from 65° to 85° C. have been used.
The length of time for which heating is effected may also be of importance. If heating is continued for too long, excessive migration of the adhesive composition from the yarn threads into the pile fibers may occur and this can result in reduced adhesion and also excessive stiffness of the woven fabric. Using a reactivation oven at 120°C., a residence time of about 5 minutes has been found to be adequate with adhesive compositions having a softening point of about 85° C. With radiant heating, e.g., using infra-red heaters, longer heating may be necessary particularly with thick carpets where the heat can take longer to penetrate. For this reason, infra-red heaters are not ideal for thick carpets. Better penetration will be obtained using hot air blowers.
The following Examples illustrate the production of yarns in accordance with the present invention. In these Examples the following ethylene copolymers are used:
Copolymer "A" -- Ethylene/vinyl acetate copolymer (by weight 67:33 ethylene:vinyl acetate) having a melt index of 25 (g/10 min ASTM D-1238 modified), an inherent viscosity of 0.78 (0.25 percent in toluene at 30° C.), and a softening point of 240° F. (ring and ball)
Copolymer "B" -- Ethylene/vinyl acetate copolymer (by weight 72:28 ethylene:vinyl acetate) having a melt index of 400, an inherent viscosity of 0.59 and a softening point of 180° F.
Copolymer "C" -- Ethylene/vinyl acetate/methacrylic acid terpolymer (by weight 71:28:1 ethylene:vinyl acetate:methacrylic acid) having an acid number of 6 (mg potassium hydroxide per gram polymer), a melt index of 6, an inherent viscosity of 0.87, and a softening point of 316° F.
Copolymer "D" -- Ethylene/vinyl acetate/methacrylic acid terpolymer (by weight 74:25:1 ethylene:vinyl acetate:methacrylic acid) having an acid number of 6, a melt index of 150, an inherent viscosity of 0.77 and a softening point of 195° F.
Copolymer "E" -- Ethylene/vinyl acetate copolymer (by weight 72:28 ethylene:vinyl acetate: having a melt index of 6, an inherent viscosity of 0.94 and a softening point of 310° F.
EXAMPLE 1
Adhesive Composition % by weight Copolymer "A" 20.0 Copolymer "B" 35.0 Microcrystalline wax (M.pt. 180°F.) 33.9 Paraffin wax (M.pt. 160°F.) 10.0 "Armid" O Slip Agent 1.0 "Tenox" BHT Antioxidant 0.1 100.0
Blending of Ingredients
The waxes are melted in a heated blending tank, and the BHT antioxidant is added. The mixture is then heated to 160° C. with stirring to form a homogeneous mass. The A and B copolymers and slip agent are then added with vigorous stirring and stirring is continued first at high speed and then at lower speeds until a homogenous composition is obtained.
Orientated fibrillated high density polypropylene yarn (1,000 denier "Cournova" of British Celanese) is coated with 350- 400 percent by weight (based on the weight of uncoated yarn) of the adhesive composition to provide a yarn in accordance with the present invention.
EXAMPLE 2
Adhesive Composition % by weight Copolymer "C" 15.0 Copolymer "D" 35.0 Paraffin wax (M.pt. 135°F.) 44.9 Polyethylene A 616 (low molecular weight polyethylene of Veba Chemie, Germany) 4.0 "Armid" O Slip Agent 1.0 "Tenox" BHT Antioxidant 0.1 100.0
The ingredients are blended as described in Example 1.
1,000 Denier "Cournova" yarn is coated with 350- 400 percent by weight (based on the weight of uncoated yarn) of the above composition to provide a yarn in accordance with the present invention.
EXAMPLE 3
Adhesive Composition % by weight Copolymer "A" 25.0 Copolymer "B" 25.0 Microcrystalline wax (M.pt. 180°F.) 30.0 "Foral" 85 (highly stabilized ester resin of Hercules Inc., USA) 18.4 "Armid" O Slip Agent 1.5 "Tenox" BHT Antioxidant 0.1 100.0
The ingredients are blended as described in Example 1.
1,000 Denier "Cournova" yarn is coated with 350- 400 percent by weight (based on the weight of uncoated yarn) of the above composition to provide a yarn in accordance with the present invention.
EXAMPLE 4
Adhesive Composition % by weight Copolymer "E" 30.0 Piccolyte S-85 (Polyterpene resin of Pennsylvania Industrial Chemical Corp., USA) 20.0 Microcrystalline wax (M.pt. 180°F.) 30.0 Paraffin wax (M.pt. 160°F.) 18.4 "Armid" O Slip Agent 1.5 "Tenox" BHT Antioxidant 0.1 100.0
The ingredients are blended as described in Example 1.
1,000 Denier "Cournova" yarn is coated with 350- 400 percent by weight (based on the weight of uncoated yarn) of the above composition to provide a yarn in accordance with the present invention.
EXAMPLE 5
The yarns of Examples 1 to 4 are used as weft threads in the weaving of Axminster and Wilton carpets on conventional looms and after reactivation of the adhesive by heating in a reactivation oven at 120° C. for 5 minutes provide carpets having excellent physical properties. The carpets in particular have good tuft lock and dimensional stability, and also have the additional advantage that there is a reduced tendency to fray at the edges.
Comparative experiments have been carried out to illustrate the good tuft lock obtainable in carpets made of all wool pile fibers using yarns according to the present invention as weft threads. A yarn produced in accordance with Example 1 was woven as weft thread together with jute warp and without stuffer threads into an Axminster carpet (6 shots per inch) and the adhesive composition then reactivated by heating in a reactivation oven at 120° C. for 5 minutes. The tuft lock (measured by means of the Wool Industry Research Association Tuft Pull Tester) was 1950 grams. Similarly, using yarn coated with 475° percent weight (based on the uncoated weight of the yarn) of adhesive composition as described in Example 1 except for a reduction to 0.25 percent in the amount of slip agent, the following results for tuft lock were obtained with various residence times in a reactivation oven at 110° C.
residence time in min. Tuft lock in grams 5 940 7 1866 9 1874 11 2300
By comparison, Axminster carpets of the same type but incorporating jute weft threads and back-sized with a typical latex composition, after weaving showed an average tuft lock of 624 gms (range of 600- 700 grams).
Similar experiments have been carried out using 1,000 denier "Cournova" yarn coated with the adhesive composition of Example 2 at different coating weights. The results were as follows:
a. An Axminster carpet produced using yarn coated with 500- 550 percent by weight of the adhesive composition of Example 2 as weft thread and reactivated for about 5 minutes at about 120° C. had an average tuft lock of about 2490 grams.
b. A Wilton carpet produced using yarn coated with 910 percent by weight of the adhesive composition of Example 2 as weft thread and reactivated for about 5 minutes at about 120° C. had an average tuft lock of about 665 grams.
Similar results are obtainable with the coated yarns of Examples 3 and 4.
By comparison, a Wilton carpet incorporating jute weft threads and back-sized with a typical latex composition after weaving commonly has a tuft lock of less than 400 grams (usually about 250 grams). A Wilton carpet with no latex back-sizing commonly has a tuft lock of less than about 200 grams.