Title:
Sizing compositions
United States Patent 2393179
Abstract:
This invention relates to paper sizing compositions, and in particular concerns rosin size dispersions in which substantially all of the rosin is in free form. It also concerns rosin size dispersions of this type stabilized against coagulation upon freezing. Although the Paper-making art has...


Inventors:
Mashburn, Robert T.
Application Number:
US42252041A
Publication Date:
01/15/1946
Filing Date:
12/11/1941
Assignee:
HERCULES POWDER CO LTD
Primary Class:
Other Classes:
106/147.1, 106/220, 106/238
International Classes:
D21H17/62
View Patent Images:
Description:

This invention relates to paper sizing compositions, and in particular concerns rosin size dispersions in which substantially all of the rosin is in free form. It also concerns rosin size dispersions of this type stabilized against coagulation upon freezing.

Although the Paper-making art has for many years in the past employed aqueous solutions or dispersions of saponified rosin almost exclusively for sizing purposes, in recent years it has been realized that improved sizing efficiency and substantial manufacturing economies could be obtained by the use of rosin size dispersions in which practically aL cf the rosin is present in free, i. e., unsaponified, form. Accordingly, a number of 16 sizing complositions of this general type have been proposed, and while several of such compositions have enjoyed moderate commercial usage, they have certain disadvantages which prevent their general acceptance throughout the sizing art. For example, in U. S. Patent No. 2,116,768 it has been proposed to prepare high free rosin size dispersions by treating an aqueous solution of saponified rosin with a protein, e. g., milk casein or soya bean protein, which hydrolyzes the saponified rosin to form an emulsion or suspension comprising free rosin and an anlkali proteinate. The suspension is then treated with an acid or acid salt, such as boric acid, aluminum sulphate, acetic acid, mono-sodium phosphate, etc., to extend the hydrolysis reaction and to neutralize the alkali proteinate. Such sizes, however, seldom contain more than 70 per cent of the rosin in free form, and, as a result of an acid or acid salt having been used to extend the hydrolysis reaction and to neutralize the alkali protenate, contain considerable amounts of neutral inorganic salts, e. g., sodium borate, sodium sulphate, sodium phosphate, etc., which detract from sizing efficiency.

Similarly it has been proposed in U. S. Patent No. 1,882,680 to agitate molten rosin with an aqueous alkaline solution of a protective colloid such as casein, whereby there is formed a high free rosin paste size which may be diluted to the usual sizing concentration. This size likewise has the disadvantage in that not all of the rosin is in free form and that it contains substantial amounts of alkali which must be neutralized before the size can be precipitated on the paper fibers.

It is accordingly an object of this invention to provide non-alkaline aqueous rosin sizing compositions in which substantially all of the rosin is present in free form.

A further object is to provide aqueous rosin sizing compositions which permit maximum sizing efficiency with minimum consumption of papermaker's alum or other coagulant.

A further object is to provide aqueous rosin siz. ing compositions which are substantially free from neutral inorganic salts.

A still further object is to provide non-alkaline aqueous dispersions of free rosin which do not coagulate upon repeated freezing.

Other objects will be apparent from the followI ing detailed description of the invention and various advantages not specifically referred to herein will occur to those skilled in the art upon employment of the invention in practice.

In accordance with the above objects, I have found that free rosin may be dispersed in water with non-alkaline dispersing agents and that the dispersions so formed may be rendered stable by means of non-alkaline protective colloids. Inasmuch as both the dispersing and stabilizing agents are non-alkaline, i. e., neutral or slightly acid, it is manifest that practically all of the rosin will be present in free form and that a minimum amount of paper-maker's alum or other acid coagulant will be required to precipitate the size on the paper fibers. Accordingly, the rosin size dispersions provided by the present invention are entirely free from the disadvantages associated with the free rosin size dispersions heretofore known, and in many instances provide a degree of sizing considerably better than that provided by such prior art sizes. They are further characterized by excellent stability to floccing upon dilution with hard water.

The rosin employed in preparing my new sizing compositions may be any of the grades of refined wood or gum rosin, or it may be a mixture of gum and wood rosins. Alternatively, it may be a rosin which has been subjected to heat-treatment to reduce its tendency to crystallize and form acid abietate salts, but insufficient to reduce its tendency to crystallize, or it may be rosin which has been hydrogenated to render it stable to discoloration and oxidation in the air.

Any non-alkaline orgflanic dispersing agent may be employed to maintain the rosin in aqueous dispersion, although it will generally be found preferable to employ a sulphonated fat or oil, such as sulphonated castor oil, sulphonated stearin, sulphonated linseed oil, sulphonated fish oil, etc. However, other neutral dispersing agents, such as triethanolamine oleate, alkylaryl sulphonic acid salts, sulphonated higher fatty alcohols, etc., may be employed if desired. The proportion of the dispersing agent required for dispersing the rosin depends somewhat upon the 2 2,898, particular agent employed, but will usually be between about 2 and about 10 per cent by weight of the rosin.

The protective colloids employed as stabilizing agents for the aqueous rosin dispersions are preferably substantially neutral proteinaceous materials, such as milk casein, egg albumin, soya bean protein, etc., although other colloidal substances, e. g., gum arabic, starch, water-soluble methyl cellulose, etc., may be employed if desired. The proportion of the protective colloid required to stabilize the dispersion is somewhat dependent on the proportion of dispersing agent employed as well as upon the degree of stability desired. Ordinarily, however, it will be found satisfactory to employ the protective colloid in an amount between about 1 and about 25, preferably between about 5 and about 20, per cent by weight of the rosin and in the form of a relatively concentrated, e. g., 15-20 per cent by weight, aqueous dispersion.

According to a preferred mode of preparing the sizing compositions provided by the invention, the rosin is melted and the desired amount of the dispersing agent is added with sufficient agitation to form a homogeneous molten mass. A substantially neutral or slightly acid aqueous solution or disperzion of the protective colloid is then added gradually with rapid stirring, whereby there is produced a high solids paste-type dispersion which can readily be diluted with water to a solids concentration between about 40 and about 60 per cent by weight.

The following examples will illustrate several ways in which the principle of the invention has been applied, but are not to be construed as limiting the same.

EXAMPLE 1 Approximately 800 parts by weight of G gum rosin was melted by heating to a temperature of about 100* C., after which 40 parts by weight of 75% sulphonated castor oil was gradually added with stirring. Stirring was continued for several minutes to insure uniform dispersion of the sulphonated castor oil in the molten rosin, during " which time the temperature of the mixture was maintained at about 100' C. Approximately 192 parts by weight of an aqueous casein solution having a pH of about 6.7 and containing 16.7% by weight of casein was then gradually added with 5U rapid stirring to the molten mixture of rosin and sulphonated castor oil, after which the mixture was diluted with 400 parts of water. The composition so obtained was a stable, substantially neutral rosin dispersion containing about 60% by 5i weight of solids. A particle size determination showed that 40% of the dispersed particles were were heated to a temperature of about 100° C., and 22.5 pounds of 75% sulphonated castor oil were added with stirring. When the sulphonated castor oil had become uniformly dispersed throughout the molten rosin, 15 pounds of casein in the form of a neutral 15% by weight aqueous suspension were gradually added with vigorous agitation, after which the resulting paste was diluted with 242 pounds of water. Approximately 20 pounds of the size dispersion so prepared (equivalent to 9 pounds of rosin) were employed to size a paper furnish consisting of 350 pounds of unbleached sulphite pulp and 1,000 pounds of old paper stock. The paper prepared from the sized furnish had a basis weight (500 24 x 36 sheets) of 41.5 pounds, a Gurley densometer porosity value of 113 sees., a sugar dye water penetration value of about 10 sees., and an ink flotation value of 20 sees. In contrast, a paper prepared from a similar furnish which had been sized with 12.7 pounds of a 12% free rosin paste size (equivalent to 12 pounds of rosin) had a basis weight of only 40.5 pounds, a Gurley densometer porosity value of 122 secs., a water penetration value of about 11 sees., and an ink flotation value of 28 sees.

EXAMPLE 3 Approximately 150 parts by weight of K wood rosin, which had previously been heat-treated at a temperature of about 300° C. for a length of time sufficient to reduce its tendency to form acid abietate salts but insufficient to reduce its crystallizability, i. e., until its solid optical rotation was raised to a value of about +15, was melted by heating to a temperature of about 105° C. Approximately 10 parts by weight of sulfonated castor oil were then gradually stirred into the molten rosin, after which 45 parts by Sweight of a 16.7 per cent aqueous dispersion of casein were added rapidly with vigorous agitation. The resulting mixture was then mixed with 125 parts by weight of cold water to obtain a paste size which could readily be diluted to ordiSnary sizing concentrations simply by the addition of cold water.

The following Table I presents data illustrative of the sizing efficiency of a size dispersion prepared as described in Example 1, as compared to that of several commercial sizes. In each experiment, 100 per cent bleached sulphite pulp was beater-sized with sufficient size to provide 1 per cent rosin, based on the weight of dry pulp.

Handsheets were then run from the sized pulp, i and after drying and conditioning the sheets were subjected to the sizing tests indicated in the table.

le Basis weight, Water pene- News pene- Ferric Experment ize lbs. (500 24 tration tration chloride No. x 36 sheets) test, sees. test, sees. test, sees. 31.0 25.7 50.7 15.8 -....__....... Size prepared as in Example I-....------------------------------ 30.4 23.0 22.3 13.7 2 -----------Commercial dry size ----- - ----------------------------- 30.1 2.0 24.3 14.7 3.----.-----. . Commercial paste size containing 17.2 per cent rosin in free form. 1.1 24. 24.5 14.7 4 --........... Size prepared according to U. S. 1,882,680 ...---------------------- 3.2 18.6 ... ------5-----------------------------SiepeaeacodntoUS.21678-------------------------- 32.0 18.6------------ -------------..-........ Size prepared according to U. S. 2,116,768..... . . . -... . . . smaller than one micron, 10% were larger than While the free rosin sizing dispersions provided 3 microns, and practically none were larger than 70 by the invention have good mechanical stability five microns. After storage in glass at 80' F. for in that they do not tend to coagulate or break 4v/2 months, a second size determination showed upon long standing at room temperatures, and that little change in particle size had taken place. are stable to flocclng upon dilution with hard water, they are rather sensitive to freezing, I. e., EXAMPLE 2 they freeze and break at temperatures not far Approximately 300 pounds of G gum rosin 75 below the freezing point of water. While this characteristic is of no significance summer months or in southern parts try, in northern climates it constitute able disadvantage. I have found, hi the dispersion may be stabilized agai by the addition of a small proportio more of the materials: dried whey, syrup, glycerol, and ethylene glycol.

terials not only lower the freezing dispersion but also stabilize it against upon repeated freezing at temperat as -15° F. to -23* F. for as long Accordingly, the sizing dispersions this manner may be shipped as stored nate conditions of freezing and thawil periods of time without danger of coa Ordinarily, the above-mentioned agents are simply added to the flnishe in the form of an aqueous solution, desired they may be incorporated in sion during its preparation as herei scribed. Usually, they are employed ii representing between about 2 and ab erably about 6, per cent by weight of sion, although the exact amount will the particular stabilizing agent, the cc of the dispersion, and the degree desired.

The following Table II presents da ing the degree of stability to coagu freezing secured through the use of ce above-mentioned stabilizing agents.

periment the designated stabilizing a form of an aqueous solution was adde icated proportion to a sample of the persion prepared in Example 1. Th dispersions were then completely fro posure to temperatures within the rar -15° F. to -23° F. for 16 hours, after were allowed to return to room tempe a period of 8 hours. This treatment, in.the table as a "cycle," was repeate dispersion broke or until it resisted through ten cycles.

Table II Experiment No.

----------„--S.---... ........ .. 3---.............

34-........-. .. 51-..-... .....- . 6----...--..-...-7 ......--- ....

8 ..----------....

9 .................

10 .----------....

11 - --------.12---...........13...--------........

14---......- --. . Stabilizing agent Name Amount 1 None...----Dried whey.

---- dAo ----..do---..

Sugar....

....-do.---. -----do -- --.....do ....Corn syrup..--- do ---. .... do ------- do ------do.--during the This application is a continuation-in-part of of the coun- my co-pending application Serial No. 282,201, filed s a consider- June 30, 1939.

owever, that What I claim and desire to protect by Letters inst freezing 5 Patent is: »n of one or 1. A stable nonalkaline paper sizing composisugar, corn tion consisting essentially of a dispersion of free These ma- rosin and a nonalkaline organic dispersing agent point of the for the rosin in an amount sufficient for disperscoagulation 10 ing the rosin, in a nonalkaline aqueous medium ;ures as low comprising water and a protective colloid in an as 16 hours, amount sufficient to stabilize the dispersion, said stabilized in sizing composition being substantially free of rosin under alter- soap.

ng over long 15 2. A stable nonalkaline paper sizing composigulation. tion consisting essentially of a dispersion of free stabilizing rosin and between about 2 and about 10% of a d dispersion nonalkaline organic dispersing agent for the rosin, although if based on the weight of the rosin, in a nonalkaline the disper- 20 aqueous medium comprising water and between nbefore de- about 1 and about 25% of a protective colloid, n an amount based on the weight of the rosin, said sizing comout 10, pref- position being substantially free of rosin soap. the disper- 3. A stable nonalkaline paper sizing composilepend upon 25 tion consisting essentially of a dispersion of free ncentration rosin and between about 2 and about 10% of a of stability nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonta illustrat- alkaline aqueous medium comprising water and lation upon 30 between about 1 and about 25% of a protective *rtain of the colloid, based on the weight of the rosin, said In each ex- sizing composition being substantially free of rosin Lgent in the soap and containing between about 40 and about Id in the in- 60% by weight of solids. e sizing dis- 35 4. A stable nonalkaline paper sizing composite stabilized tion consisting essentially of a dispersion of free ozen by ex- rosin and between about 2 and about 10% of a ige of about nonalkaline sulfonated glyceride oil in a nonwhich they alkaline aqueous medium comprising water and erature over 40 between about 1 and about 25% of a protective referred to colloid, based on the weight of the rosin, said ed until the sizing composition being substantially free of coagulation rosin soap.

5. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glyceride oil in a nonalkaStability line aqueous medium comprising water and between about 1 and about 25% of a protective colloid, based on the weight of the rosin, said sizing :e on 1st cycle, composition being substantially free of rosin soap Do. and containing between about 40 and about 60% e to 130 cycle. by weight of solids.

Donstcycle 6. A stable nonalkaline paper sizing composite on 2nd cycle. 55 tion consisting essentially of a dispersion of free le to 10 cycles, rosin and a nonalkaline organic dispersing agent Do.

e on Ist cycle, for the rosin in an amount sufficient for disperse on 2nd cycle. ing the rosin, in a nonalkaline aqueous medium 3o. comprising water and between about 1 and about Do. 60 25% of a proteinaceous protective colloid, based on the weight of the rosin, said sizing composition being substantially free of rosin soap.

ble that al- 7. A stable nonalkaline paper sizing composieaks on the tion consisting essentially of a dispersion of free unts of the 65 rosin and between about 2 and about 10% of a to coagu- nonalkaline sulfonated glyceride oil in a nonalkach a degree line aqueous medium comprising water and bed the most tween about 1 and about 25% of casein, based rsion might on the weight of the rosin, said sizing composition ge prior to 70 being substantially free of rosin soap. agent in no 8. A stable nonalkaline paper sizing composind the sta- tion consisting essentially of a dispersion of free ereinbefore rosin and between about 2 and about 10% of a tics of the nonalkaline sulfonated glyceride oil in a nonal75 kaline aqueous medium comprising water and beBrok Brok Stab Brok Brok Stab Brok Brok Stab ' Per cent by weight of dispersion.

It will be noted from the above tal though the unstabilized dispersion br first cycle, the use of only small amo stabilizing agents provides resistance lation through at least ten cycles. Su of resistance is sufficient to withstan severe conditions to which the disper be exposed during shipment or stora use. The presence of the stabilizing way detracts from sizing efficiency, a bllized dispersions retain all of the h mentioned advantageous characteris unstabilized dispersions.

tween about 1 and about 25% of casein, based on the weight of the rosin, said sizing composition being substantially free of rosin soap and containing between about 40 and about 60% by weight of solids.

9. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of sulfonated castor oil in a nonalkaline aqueous medium comprising water and between about 1 and about 25% of casein, based on the weight of the rosin, said sizing composition being substantially free of rosin soap.

10. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of sulfonated castor oil, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water and between about 1 and about 25% of casein, based on the weight of the rosin, said sizing composition being substantially free of rosin soap and containing between about 40 and about 60% by weight of solids.

11. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and a nonalkaline organic dispersing agent for the rosin in an amount sufficient for dispersing the rosin, in a nonalkaline aqueous medium comprising water, a protective colloid in an amount sufficient to stabilize the dispersion, and an agent selected from the group consisting of dried whey, sugar, corn syrup, glycerol, and ethylene glycol, said agent being present in an amount sufficient to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of -15' to -23° F. for 16 hours, said sizing composition being substantially free of rosin soap.

12. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 -and about 10% of a nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of a protective colloid, based on the weight of the rosin, and between about 2 and about 10% by weight of the dispersion of an agent selected from the group consisting. of dried whey, sugar, corn syrup, glycerol, and ethylene glycol, said agent rendering the dispersion stable to coagulation upon repeated freezing at temperatures in the range of -15' to -23" F. for 16 hours, said sizing composition being substantially free of rosin soap.

13. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of a protective colloid, based on the weight of the rosin, and about 6% of dried whey, based on the total weight of the rosin dispersion, said dried whey serving to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of -15° to -23° F. for 16 hours, said sizing composition being substantially free of rosin soap.

14. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and .between about 2 and about 10% of a nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of a protective colloid, based on the weight of the rosin, and about 6% of sugar, based on the total weight of the rosin dispersion, said sugar serving to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of -15" to -23* F. for 16 hours, said sizing composition being substantially free of rosin soap.

15. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline organic dispersing agent for the rosin, based on the weight of the rosin, in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of a protective colloid, based on the weight of the rosin, and about 6 % of corn syrup, based on the total weight of the rosin dispersion, said corn syrup serving to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of -15° to -23' F. for 16 hours, said sizing composition being substantially free of rosin soap.

16. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glyceride oil in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of casein, based on the weight of the rosin, and an amount of dried whey sufficient to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of -15' to -23* F. for 16 hours, said sizing composition being substantially free of rosin soap.

17. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glycerine oil in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of casein, based on the weight of the rosin, and an amount of sugar sufficient to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of -15° to -23° F. for 16 hours, said sizing composition being substantially free of rosin soap.

18. A stable nonalkaline paper sizing composition consisting essentially of a dispersion of free rosin and between about 2 and about 10% of a nonalkaline sulfonated glyceride oil in a nonalkaline aqueous medium comprising water, between about 1 and about 25% of casein, based on the weight of the rosin, and an amount of corn syrup sufficient to render the dispersion stable to coagulation upon repeated freezing at temperatures in the range of -15° to -236 F. for 16 hours, said sizing composition being substantially free of rosin soap.

ROBERT T. MASHBURN.