Russell, Gordon D. (Chateauguay, CA)
Roy, Rabindranath (Montreal, CA)

05/433625

09/23/1975

01/16/1974

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Johnson & Johnson (New Brunswick, NJ)

428/198

427/412, 427/411, 427/288, 427/265

D04H1/66; D04H1/64; B05D1/34; B05D1/36; D04H1/66; B05D1/28

161/148,88,170 117/45,76T,76FB,14A,76P,38

3753826	METHODS OF MAKING NONWOVEN TEXTILE FABRICS	August 1973	Plummer
3778341		December 1973	Plummer et al.

Lesmes, George F.

Cannon J.

What is claimed is

1. A strong, absorbent, abrasion-resistant, bonded nonwoven fabric comprising a fibrous layer containing staple length textile fibers and short fibers having less than textile staple length wherein the staple length fibers comprise up to 75% by weight of the fiber weight of the fibrous layer and the balance of the fiber weight in said layer is provided by the less than textile staple length fibers said fibrous layer being bonded by: (1) primary, intermittently-spaced, print pattern binder sites extending substantially from one surface of said fibrous layer to the other surface of said fibrous layer, said primary binder sites being spaced apart a distance less than the average length of staple length textile fibers but greater than the average length of short textile fibers; and (2) secondary, intermittently-spaced print pattern binder sites positioned predominantly on the surface of said fibrous layer and located between the intermittently-spaced binder sites of primary print pattern binder.

2. A strong, absorbent, abrasion-resistant, bonded nonwoven fabric as defined in claim 1 wherein the add-on of the primary binder is in the range of from about 6 by weight to about 30% by weight on a dry weight basis, based on the dry weight of the bonded nonwoven fabric.

3. A strong, absorbent, abrasion-resistant, bonded nonwoven fabric as defined in claim 1 wherein the add-on of the secondary binder for each surface bonded thereby is in the range of from about 2 by weight to about 10% by weight on a dry weight basis, based on the dry weight of the bonded nonwoven fabric.

4. A strong, absorbent, abrasion-resistant, bonded nonwoven fabric as defined in claim 1 wherein the short fibers are wood pulp fibers.

5. A strong, absorbent, abrasion-resistant, bonded nonwoven fabric as defined in claim 1 wherein the short fibers are cotton linters.

6. A strong, absorbent, abrasion-resistant bonded nonwoven fabric as defined in claim 1 wherein the textile length staple fibers are nylon fibers.

7. A strong, absorbent, abrasion-resistant bonded nonwoven fabric as defined in claim 1 wherein the textile length staple fibers are polyester fibers.

8. A strong, absorbent, abrasion-resistant, bonded nonwoven fabric as defined in claim 1 wherein the textile length staple fibers are rayon.

9. A method of making a strong, absorbent, abrasion-resistant, bonded nonwoven fabric comprising: forming a fibrous layer from staple length textile fibers and short fibers having less than textile staple length to provide a fibrous layer wherein the staple length fibers comprise up to 75% by weight of the fiber weight of the fibrous layer and the balance of fiber weight in said layer is provided by the less than textile staple length fibers; and bonding said fibrous layer with (1) primary, intermittently-spaced, print pattern binder sites extending substantially from one surface of said fibrous layer to the other surface of said fibrous layer, said primary binder sites being spaced apart a distance less than the average length of staple length textile fibers but greater than the average length of short textile fibers; and (2) secondary, intermittently-spaced, print pattern binder sites positioned predominantly on the surface of said fibrous layer and located between the intermittently-spaced binder sites of said primary print pattern binder.

10. A method of making a strong, absorbent, abrasion-resistant, bonded nonwoven fabric as defined in claim 9 wherein the application of the primary bonding and the two secondary bondings takes place in three separate steps.

11. A method of making a strong, absorbent, abrasion-resistant, bonded nonwoven fabric as defined in claim 9 wherein the application of the primary bonding and one secondary bonding takes place on one surface of said bonded nonwoven fabric in one step and the application of the second secondary bonding takes place on the other surface of said bonded nonwoven fabric in a second step.

The present invention relates to strong, absorbent, abrasion-resistant, bonded nonwoven fabrics and to methods of making the same. More particularly, the present invention is concerned with strong, absorbent, abrasion-resistant, bonded nonwoven fabrics suitable for cleaning and wiping purposes and to methods of bonding the same whereby the strength, absorbency, and abrasion-resistant properties are improved over those of prior art bonded nonwoven fabrics. Even more particularly, the present invention is concerned with improved, strong, absorbent, and abrasion-resistant wiping materials for absorbing and holding oleaginous substances such as greases, oils and fats, and to novel methods of making the same.

GENERAL BACKGROUND

Bonded nonwoven fabrics have been used hitherto in many uses, such as, for example, wiping and cleaning cloths, and have been found to be generally satisfactory and commercially acceptable in industry. However, in general, there is always a desire to improve the properties and characteristics of such bonded nonwoven fabrics and, in this particular application, there has always been a desire to improve the strength, absorbency, and abrasion-resistant properties thereof without loss of other desirable properties.

Such desires are all the more needed and noted in bonded nonwoven fabrics which contain relatively short fibers such as wood pulp, cotton linters, and the like, the use of which is usually detrimental to strength and abrasion-resistance due to low surface tiedown of the short fibers, their tendency to slough off upon rubbing, and their general lack of strength due to their short length.

STATEMENT OF THE INVENTION

It has been discovered that such desires may be realized by providing a strong, absorbent, abrasion-resistant, bonded nonwoven fabric comprising a fibrous layer of: (1) from 0% by weight to about 75% by weight of textile length staple fibers; and (2) from 100% by weight to about 25% by weight of short fibers having a length less than the textile length staple fibers, the fibrous layer being bonded by: (1) primary, intermittently-spaced print pattern binder sites extending substantially from one surface of the fibrous layer to the other surface of the fibrous layer and; (2) secondary intermittently-spaced print pattern binder sites positioned predominantly on the surface of the fibrous layer and located thereon between the intermittently-spaced binder sites of the primary print pattern binder.

In the following specification and accompanying drawings, there are described and illustrated preferred embodiments of the invention but it is to be understood that the inventive concept is not to be considered limited to the preferred embodiments disclosed, except as determined by the scope of the appended claims.

GENERAL DESCRIPTION OF THE DRAWINGS

Referring to the drawings,

FIG. 1 is a simplified, diagrammatic, schematic flow chart illustrating one method embodiment of the present invention;

FIG. 2 is a simplified, diagrammatic, schematic flow chart illustrating another method embodiment of the present invention; and

FIG. 3 is an idealized, fragmentary cross-section of a bonded nonwoven fabric as made by either of the methods illustrated in FIGS. 1 and 2, with the cross-section being taken along the long or machine direction of the bonded nonwoven fabric.

PREFERRED ILLUSTRATIVE EMBODIMENT

With reference to FIG. 1, there is shown fiber-handling apparatus 10 for forming a fibrous web of overlapping, intersecting fibers. The particular type of such apparatus does not specifically relate to the essence of the present invention and may comprise carding machines, air-laying or wet-laying equipment such as garnetts, double lickerins, rando-feeders and rando-webbers, paper making machines, etc.

THE FIBERS USED

The fibers used may comprise from 0 by weight to about 75% by weight of textile length staple fibers having an average length of at least about 1/2 inch up to about 11/2 inches or even longer, say, up to 3 inches, as desired. Such fibers include natural fibers, notably cotton, and synthetic or man-made fibers such as rayon, polyamide nylon 6 and 66, polyester, polyolefinic, polyacrylic modacrylic, cellulosic derivatives, polyvinyl alcohol, and like fibers. The synthetic or man-made fibers have a denier of from about 1 to about 5, although higher deniers up to 10 or 15 are of use in special circumstances.

Short fibers such as wood pulp, cotton linters, and the like, or synthetic or man-made fibers in short lengths less than about 1/2 inch, or 1/4 inch, may also be included in amounts of from about 25 by weight to 100% by weight. Such fibers have average lengths of less than about 1/2 of an inch and normally less than about 1/4 of an inch, and may average as low as about 1/64 of an inch, or even less.

As used herein, the word "fiber" is used in its normal technical or dictionary sense, such as is defined in ASTM Designation D 123-72. A fiber is a generic term for the various types of matter (natural or man-made) which form the basic elements of textile fabrics and other textile structures. More specifically, a fiber is a unit of matter characterized by having a length at least about 100 times its diameter or width, and quite often greater than about 160 times its diameter or width.

THE PRIMARY BONDING

The fibrous web W, after being formed in the former 10, is forwarded, if desired, to wetting-out or moisture-control apparatus 12 to adjust the moisture content thereof to a desired range. The fibrous web with the moisture content controlled therein is then forwarded to conventional nonwoven fabric bonding apparatus 14 capable of applying a primary, intermittently-spaced print pattern binder B to the fibrous web W in the form of discrete binder sites or areas 16 (see FIG. 3). Examples of such primary, intermittently-spaced print pattern binder sites or areas are cross-hatch patterns (U.S. Pat. No. 2,705,687), dot or annuli patterns (U.S. Pat. No. 2,705,688), diamond patterns (FIG. 3, U.S. Pat. No. 2,705,498), torpedo patterns (U.S. Pat. No. 3,009,823), etc.

As noted in FIG. 3, the primary binder B is so applied under controlled nip pressure and other print roll conditions as well as from relatively deep engraved recesses on the print roll whereby relatively larger amounts of binder are picked up for application to the fibrous web that it ideally penetrates directly and completely through the fibrous web W from one surface to the other surface and bonds the longer textile length staple fibers together to provide coherency and strength to the finished nonwoven fabric without undesirably affecting the softness, hand or drape thereof. The surface coverage of such primary binders, as initially applied, is in the range of from about 5 to about 50% of the total surface of the fibrous web with from about 10 to about 35% being preferred.

THE BINDERS USED

The binder resins used for the primary binder and other binders to be disclosed hereinafter may be selected from a relatively large group of resins, particularly of synthetic origin and are usually in the form of aqueous dispersions, and may be polymers and copolymers of polyvinyl ethers, polyvinyl halides such as plasticized and unplasticized polyvinyl chloride, polyvinyl chloride and other plastisols, polyvinyl esters such as plasticized and unplasticized polyvinyl acetate, polyacrylic resins such as polyethyl acrylate and polybutyl acrylate, polymethacrylic resins, polyolefinic resins, such as ethylene-vinyl acetate and ethylenevinyl chloride, polyamide resins, synthetic rubber resins such as styrene-butadiene, polyvinyl alcohol and other aqueous solutions, etc. Of particular advantageous use are the migration control resin binders having low migration tendencies. Examples of such resins are noted in U.S. Pat. No. 3,706,595.

The amount of primary binder add-on is in the range of from about 1 or 2% but normally about 6 by weight to about 30% by weight and preferably from about 7 by weight to about 15% by weight on a dry weight basis, based on the dry weight of the bonded nonwoven fabric.

As noted in FIG. 3, there are discrete bonded sites or areas 16, intermittently-spaced by areas 18 which are not contacted and bonded by the primary binder. In these areas 18, there are relatively large numbers of short fibers having a length less than the distance between adjacent bonded areas 16 which, if left unbonded and not tied down, tend to slough off and be lost during use and particularly during rubbing or the application of abrasive forces.

THE SECONDARY BONDING

The fibrous web with the primary binder theron is forwarded to a conventional nonwoven fabric bonding apparatus 20 capable of applying a secondary intermittently-closely-spaced print pattern binder B' to the fibrous web. Examples of such secondary intermittently-closely-spaced print pattern binder areas are diamond patterns (FIG. 3, U.S. Pat. No. 2,705,498) and diagonal and wavy line patterns (FIGS. 1-4, U.S. Pat. No. 3,009,822). Fine or miniature dot patterns as applied by gravure shape cells are also of use.

As noted in FIG. 3, the secondary binder B' is so applied under controlled nip pressure and other print roll conditions as well as from shallow engraved recesses on the print roll whereby relatively smaller amounts of binder are picked up for application to the fibrous web that it does not penetrate materially into the fibrous web but basically lies primarily and predominantly on the surface thereof. In this way, it ties down the surface fibers, and particularly the short fibers in the areas 18 which have not been contacted by the primary binder.

Such tying-down of the surface fibers by the secondary binder prevents sloughing off and loss of the surface fibers and increases the resistance to rubbing and abrasion. Naturally, the secondary binder does not add materially to the strength of the finished nonwoven fabric or detract materially from the softness, hand or drape thereof. The total surface coverage of such secondary binders as initially applied, is the range of from about 40 to about 90% of the total surface of the fibrous web. The add-on of the secondary binder, considering one side only, is in the very low range of from about 0.2% but normally about 2 to about 10% by weight on a dry weight basis, as determined in the finished dry nonwoven fabric. It is to be noted in passing that the secondary binder is applied not only to the areas between the primary binder sites, but also to the primary binder sites themselves.

The fibrous web with the primary binder and secondary binder on one side only may then be forwarded to moisture control apparatus 22 such as a heated oven or heated drying cans and brought to a desired moisture content, if desired or required.

The fibrous web is then guided around rotatable, directional guide rolls 24 and 26 and is passed through conventional nonwoven fabric bonding apparatus 28 which is substantially identical to secondary nonwoven fabric bonding apparatus 20 except that a binder B' is applied to the other side of the fibrous web. The binder patterns, surface coverage, dry add-on of binder, etc., are of the shape and form and in the range described previously with respect to the secondary binder B'.

The fibrous web is then passed through conventional drying means 30 such as a heated oven or heated drying cans at an elevated temperature to dry the fibrous web and to dry and cure, if necessary, the applied binders.

The dried, bonded nonwoven fabric is then forwarded to rewind apparatus to be formed into a finished roll 32.

THE MODIFICATION OF FIG. 2

A modification of the inventive concept is illustrated in FIG. 2, wherein reference characters and legends of elements corresponding to elements of FIG. 1 are given the same reference number followed by the letter a. In FIG. 2, there is shown fiber handling apparatus 10a for forming a fibrous web Wa, basically similar to that disclosed in FIG. 1.

The fibrous web Wa is then forwaded to wetting-out or moisture-control apparatus 12a whereat the moisture content is adjusted to a desired range. The wet fibrous web is then forwarded to conventional nonwoven fabric bonding apparatus 14a, 20a, capable of substantially simultaneously applying: (1) a relatively deep primary intermittently-spaced print pattern binder to the fibrous web in the form of discrete binder sites or areas as well as (2) a relatively shallow secondary intermittently-closely-spaced print pattern binder to the areas located between the primary intermittently-spaced binder areas. These print pattern binders and binder sites and area are as described previously with reference to FIG. 1.

In FIG. 2, the engraved printing roll which dips into the binder dispersion and picks up binder and applies it to the bottom surface of the fibrous web possesses engravings thereon of a relatively deep nature and of a relatively shallow nature suitable for receiving larger and smaller amounts of binder and for respectively applying deep penetrating primary binders to the fibrous web as well as shallow, low-penetrating binders to the fibrous web.

This single printing operation is to be compared to the two separate printing operations 14 and 20 of FIG. 1 and it is to be appreciated that the binder applying apparatus 14a, 20a of FIG. 2 substantially simultaneously performs the two functions carried out by the two individual binder applying devices 14 and 20 of FIG. 1.

The fibrous web is then advanced over rotatable directional guide rolls 24a and 26a and is then passed through conventional nonwoven fabric bonding apparatus 28a which applies a secondary intermittently-closely-spaced binder to the reverse side of the fibrous web.

The primary and the two secondary resin binders which are applied to the fibrous web are normally the same, chemically. However, it is to be appreciated that different resin binders may be used in special circumstances.

Heating, drying and curing of the fibrous web and binder thereon take place in conventional drying means 30a and then the dried bonded nonwoven fabric is forwarded to rewind apparatus and formed into a finished roll 32a.

The invention will be further illustrated in greater detail by the following specific examples. It should be understood, however, that although these examples may describe in particular detail some of the more specific features of the invention, they are given primarily for purposes of illustration and the invention in its broader aspects is not to be construed as limited thereto.

EXAMPLE I

The apparatus illustrated in FIG. 1 is used. A random, air-laid, isotropic fibrous web is prepared from 90% by weight of wood pulp fibers and 10% by weight of polyester fibers, 11/2 denier, 11/2 inch staple length. The fibrous web is passed through a fluid fiber rearranging unit such as illustrated in FIG. 7 of U.S. Pat. No. 2,862,251. The fibrous web is treated with water and is rearranged into fiber bundles and fabric openings as described in that patent.

The wet fibrous web is then passed through a primary binder-applying unit. The binder is a 20% by weight aqueous dispersion of a self-cross-linking polyethyl acrylate. The primary intermittent print pattern of binder (as applied) is a diamond pattern, 4 lines per inch, each line 0.024 inch wide.

The primary binder penetrates through the wet fibrous web and ultimately provides coherency and strength in the finished nonwoven fabric. Subsequent study reveals that the primary binder extends substantially completely through the fibrous web from one surface thereof to the other surface. The binder addon is 7.5% dry weight, based on the dry weight of the finished bonded nonwoven fabric.

The fibrous web is then passed through a pair of secondary binder-applying units which apply binder to both sides of the fibrous web in two separate steps. The binder is a 20% solids by weight aqueous dispersion of a self-cross-linking polyethyl acrylate. The secondary intermittent print pattern (as applied) is a diagonal line pattern, 23 lines per inch, each line 0.018 inch wide.

The secondary binder ties down the surface fibers of the fibrous web and prevents sloughing-off of fibers upon rubbing or abrasion. The binder add-on (each side) is 3.5% dry weight based on the dry weight of the finished bonded nonwoven fabric.

The fibrous web with the binder thereon is then processed, dried and cured and wound in a dried condition on a supply roll. It has a grain weight of 1415 grains/sq. yd. and is commercially acceptable as a wiping cloth.

EXAMPLE II

The procedures of Example I are followed substantially as set forth therein with the exception that the primary print pattern is the "cross-hatch" intermittently-spaced print pattern such as illustrated in FIG. 3 of U.S. Pat. No. 2,705,687.

The results are generally comparable to those obtained in Example I.

EXAMPLE III

The procedures of Example I are followed substantially as set forth therein with the exception that the primary print pattern is the "cross-hatch" intermittently-spaced print pattern such as illustrated in FIG. 5 of U.S. Pat. No. 2,705,687.

The results are generally comparable to those obtained in Example I.

EXAMPLE IV

The procedures of Example I are followed substantially as set forth therein with the exception that the primary print pattern is the annuli intermittently-spaced print pattern such as illustrated in FIG. 1 (code 11-C-1) of U.S. Pat. No. 2,705,688.

The results are generally comparable to those obtained in Example I.

EXAMPLE V

The procedures of Example I are followed substantially as set forth therein with the exception that the primary print pattern is the "torpedo" intermittently-spaced print pattern such as illustrated in FIG. 6 of U.S. Pat. No. 3,009,823.

The results are generally comparable to those obtained in Example I.

EXAMPLE VI

The procedures of Example I are followed substantially as set forth therein with the exception that the secondary intermittent print pattern (as applied) is a diagonal line pattern, 16 lines per inch, each line 0.018 inch wide.

The results are generally comparable to the results noted in Example I. The resulting bonding nonwoven fabric, however, is considered slightly softer and has a better drape and hand. The abrasion resistance, however, is lowered slightly.

EXAMPLE VII

The procedures of Example I are followed substantially as set forth therein with the exception that the secondary intermittent print pattern (as applied) is a diagonal line pattern, 23 lines per inch, each line 0.018 inch wide.

The results are generally comparable to the results noted in Example I. The resulting bonded nonwoven fabric, however, is considered slightly less soft and has a slightly poorer drape and hand. The abrasion resistance, however, is better.

EXAMPLE VIII

The procedures of Example I are followed substantially as set forth therein with the exception that the fiber mix is changed to 25% by weight of wood pulp fibers and 75% by weight of rayon fibers, 11/2 denier, 11/2 inch staple length.

The results are comparable to those obtained in Example I.

EXAMPLE IX

The procedures of Example I are followed substantially as set forth therein with the exception that the fiber mix is changed to 75% by weight of wood pulp fibers and 25% by weight of rayon fibers, 11/2 denier, 11/2 inch staple length.

The results are comparable to those obtained in Example I.

EXAMPLE X

The procedures of Example I are followed substantially as set forth therein with the exception that the fiber mix is changed to 85% by weight of wood pulp fibers and 15% by weight of rayon fibers, 11/2 denier, 11/2 inch staple length.

The results are comparable to those obtained in Example I.

EXAMPLE XI

The procedures of Example I are followed substantially as set forth therein with the exception that the fiber mix is changed to 85% by weight of wood pulp fibers and 15% by weight of polyamide nylon 6/6 fibers, 11/2 denier, 11/2 inch staple length.

The results are comparable to those obtained in Example I.

EXAMPLE XII

The apparatus illustrated in the modification of FIG. 2 is used in this Example. The basic procedures of Example I are followed substantially as set forth therein with the exception that the two conventional binder applying devices (14 and 20) are replaced by a single double function dual print binder applying device (14a and 20a). As a result, a primary binder and a secondary binder are applied substantially simultaneously from the one binder applying device. The remaining portion of the method of this Example is substantially as described in Example I.

The results are comparable to those obtained in Example I and the resulting bonded nonwoven fabric is comparable to the bonded nonwoven fabric obtained in Example I. It is commercially acceptable as a wiping cloth.

EXAMPLE XIII

The procedures of Example I are followed substantially as set forth therein with the exception that the secondary intermittent print pattern (as applied) is a diagonal line pattern 36 lines per inch, each line 0.018 inch wide.

The results are generally comparable to the results noted in Example I. The resulting bonded nonwoven fabric, however, is considered less soft and has a poorer drape and hand. The abrasion resistance, however, is improved.

EXAMPLE XIV

The procedures of Example I are followed substantially as set forth therein with the exception that the resin binder used is a 55% solids aqueous latex of a copolymer of ethylene and vinyl acetate.

The results are generally comparable to the results noted in Example I.

EXAMPLE XV

The procedures of Example I are followed substantially as set forth therein with the exception that the resin binder is a 50% solids aqueous latex of a terpolymer of butadiene (46%), styrene (51%) and a,b-unsaturated carboxylic acid (2%). The results are generally comparable to those obtained in Example I.

Although several specific examples of the inventive concept have been described, the same should not be construed as limited thereby nor to the specific features mentioned therein but to include various other equivalent features as set forth in the claims appended hereto. It is understood that any suitable changes, modifications and variations may be made without departing from the spirit and scope of the invention.