US3795527A - Dry powder paper size having improved resistance to caking - Google Patents

Abstract

A DRY POWDER PAPER SIZING COMPOSITION HAVING RESISTANCE TO CAKING BY ATMOSPHERIC HUMIDITY COMPRISED OF A MIXTURE OF A CATIONICALLY ACTIVE MATERIAL, A FATTY ACID AND AN ALKALI HYDROXIDE IS OBTAINED BY COATING THE FATTY ACID WITH THE CATIONICALLY ACTIVE MATERIAL PRIOR TO ITS ADMIXTURE WITH THE ALKALI HYDROXIDE.

Description

United States Patent Office Patented Mar. 5, 1974 3,795,527 DRY POWDER PAPER SIZE HAVING IMPROVED RESISTANCE TO CAKING James N. Stone and James H. Wing, Augusta, and Frank B. Thomas III, Martinez, Ga., assignors to Continental Can Company, Inc., New York, N.Y. No Drawing. Filed Apr. 23, 1973, Ser. No. 353,262 Int. C1. C08]: 25/02, 27/44 US. Cl. 106-206 Claims ABSTRACT OF THE DISCLOSURE A dry powder paper sizing composition having resistance to caking by atmospheric humidity comprised of a mixture of a cationically active material, a fatty acid and an alkali hydroxide is obtained by coating the fatty acid with the cationically active material prior to its admixture with the alkali hydroxide.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to a process for manufacturing a paper sizing additive which may be incorporated in pulp stock during the manufacture of paper and more specifically to a process for obtaining a sizing additive which may be formulated as a dry powder.

(2) The prior art In US. 3,392,085 there is described a method of preparing paperboard having high chemical resistance to alkaline environments wherein a sizing additive composed of a mixture of a cationically active material and a fatty acid salt is incorporated in paper pulp adjusted to an alkaline pH prior to the formation of the pulp into paperboard. In practicing the method of US. 3,392,085, an aqueous solution of the water soluble cationically active material and the fatty acid salt is added to the aqueous fiber suspension either prior to or following the addition of a water soluble precipitating agent Which is added in sufiicient amounts to provoke the forming of water insoluble soaps of the fatty acid throughout the fiber mass.

The so-treated pulp is then processed in the conventional manner for formation into paper or paperboard. Thus, the pulp having incorporated therein the insolubilized fatty acid salt and cationically active material is passed over a moving wire, whereby part of the water drains off, leaving a mat of fibers or wet web. The wet web is passed from the moving wire to a press section where additional water is removed, thence to a drier section where heat is used to evaporate the remaining water, at which point further treatment may be applied (such as calender sizing, coating, etc.) before the continuous dry sheet is wound on a reel or cut into individual sheets.

The paper product thereby obtained exhibits superior resistance to aqueous and alkaline environments.

The sizing additive solution of cationically active material and fatty acid salt is prepared by initially stirring about 30-50 weight parts of a fatty acid such as stearic acid into a solution of 400-500 weight parts of water and 5-15 weight parts of an alkali hydroxide such as KOH and then heating the mixture for 5 minutes at 210 F.

The fatty acid salts prepared in this manner are then added to an aqueous solution of the cationically active material to prepare the sizing additive solution. The resultant sizing solution has a concentration of solid additive material of about 5%.

If concentrations of greater than 5% solids are used in preparing the additive solutions the product is extremely viscous and difficult to handle.

The handling difficulties with sizing solutions containing high solids concentrations has retarded the commercial sale and utility of the sizing additive. Thus, when 5% additive solutions are contemplated for commercial use, the high cost of shipping these dilute solutions prohibitively increases the cost of the solutions to the user. When it is attempted to ship dry powder mixtures of the cationically active material, fatty acid and alkali hygroscopic nature of the alkali hydroxide causes water to be absorbed from the air on the powder mixture. A partial reaction between the fatty acid and the alkali hydroxide occurs which results in a severe caking of the additive ingredients and in some cases the formation of a solid mass. After deliquescence, it is generally extremely difficult or substantially impossible to satisfactorily remove the additive mixture from the containers in which the mixture is stored. Also, it is extremely difficult to dilute the caked mixture with water to the proper consistency preparatory to its addition to the pulp stock.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided an additive for incorporation into pulp stock during the manufacture of paper to impart chemical resistance thereto, the additive combination having improved resistance to deliquescence of atmospheric humidity, comprising a dry mixture of (1) a cationically active material selected from the group consisting of cationically active starches and gums and hydrogen bonding starches and gums (2) an alkali hydroxide and (3) a fatty acid having 12 to 20 carbon atoms, the fatty acid being coated with a portion of the cationically active material prior to its incorporation in the additive mixture.

By the practice of the present invention, a homogenous blend of a dry powder sizing additive is prepared which is substantially immune to deliquescense and will not agglomerate or cake after extended storage periods. The dry powder when dissolved in water performs equally as well, as will hereinafter be illustrated, as the aqueous additive solutions of 11.8. 3,392,085.

PREFERRED EMBODIMENTS The cationically active materials used in the practice of the present invention are cationically modified starches or gums and hydrogen-bonding starches and gums. The latter, while not technically classified as cationic materials, behave in a very similar manner, and are equivalent in function to the cationically modified starches and gums used to prepare the sizing additives of the present invention.

A wide diversity of cationically active materials are available to the art and disclosure of those more useful in the practice of the present invention may be found in US. 3,392,085, the disclosure of which is incorporated herein by reference.

Cationically modified starches and gums are obtained by modifying naturally occurring starches and gums so that they exhibit a cationic charge, i.e., a positive charge, when dissolved in aqueous medium. cationically modified starches and gums are conveniently obtained by the reaction of naturally occurring starches such as corn starch and potato starch with an etherification agent such as dialkyl aminoalkyl epoxides or dialkyl aminoalkyl halides following the procedures of US. 2,813,093 and 2,917,- 506, or epichlorohydrin and a tertiary amine following the procedure of US. 2,876,217.

Many cationically modified starches and gums which may be employed for use in the present invention are available commercially.

A cationic corn starch is sold by National Starch and Chemical Corp. under the trademark Cato 8. A cationic potato starch is sold by A. M. Menickle and Sons, under the trademark Epic-N.

The cationically modified gums which may be employed in the present invention are extracts from vegetable saps, seeds and seaweed synthetically modified. according to the same procedures used to render starches cationically active. Illustrative of such gums are locust bean gums, guar gums, kararya gums, agar and alginates.

A cationically modified galactomannan gur gum is sold by Stein, Hall and Company, Inc., under the trademark Draybond II.

Hydrogen bonding starches and gums may be extracted from their respective vegetable origins and used directly in the practice of the present invention and other nonhydrogen-bonding gums may be rendered so active by chemical treatment.

The naturally occurring hydrogen bonding starches and gums are characterized in that there are numerous hydroxyl groups on the monosaccharide units and these are sterically arranged so that hydrogen-bonding occurs between the chains. Such. hydrogen-bonding is generally attributed to the presence and behavior of these hydroxyl groups.

Tamarand seed flour is an example of hydrogen-bonding gum having cationic-type propertes and is composed of glactose, xylose and glucose units in the approximate molar ratio of 1:2:3, and is sold by Dycol Chemicals, Inc., under trademark Dycol D-16.

Another hydrogen-bonding gum is that obtained by extraction from the guar plant. While this guar gum may be employed in the present invention as the cationic material, it may also be chemically treated to attain a cationic charge such as by the etherification processes used for the starches.

Guar gums in unmodified form, as well as those in cationic form, are marketed by Stein, Hall and Company, Inc., under the trademark Jaguar.

Locust bean gum may also be employed as a hydrogen bonding, naturally occurring galactomannan.

The fatty acid employed in preparing the additive compositions of the present invention may be any one or a mixture of a saturated fatty acids having from 12 to 20 carbon atoms. Illustrative saturated fatty acids include lauric-Ciz, tridecylic-C myristic-C pentadecylic-C palmitic-C margariC-C stearic-C nondecylic-C and arachidic-C Various mixtures of these fatty acids may be commercially obtained and the commercial products usually contain some proportion of unsaturated fatty acids. For best results, the amount of unsaturated fatty acid component should not exceed 30% by 'weight of the fatty acid and preferably the fatty acid should not contain greater than 7% unsaturated fatty acids. Various commercially obtainable fatty acid mixtures which may be employed in the additive compositions of the present invention are sold by Armour Industrial Chemical Company under trade names: Neo-Fat 18s, Neo-Fat 58-59; and Darling and Company under trade names: Dar-Hy, Dar-C and Dar-S77. These commercial mixtures are generally low in unsaturated fatty acid content and contain greater than 80% of at least one or a mixture of stearic, palmitic, margaric and myristic acids.

The alkali hydroxides that may be used in preparing the dry additive powers of the present invention are the water soluble hydroxides namely sodium, potassium and lithium hydroxides.

In preparing the dry powders of the present invention the amounts of cationically active material and fatty acid powder required in the additive mixture are .dry blended, using a suitable blending means such as a rotary blender, for a time sufficient to cause the complete coating and encapsulation of the fatty acid by the cationically active material. Thereafter rial coated fatty acid is mixed with the alkali hydroxide to prepare the dry additive mixture of the present invention.

The dry powder additive mixture of the present invention is generally compirsed of about '65 to 75% by weight of the fatty acid, about 15 to 20% by weight of the cationically active material and about 10 to 20% by .weight of the alkali hydroxide.

In adding the additive mixture to paper pulp, the mixture prior to its addition to the pulp is dissolved in water by adding the mixture to water at a concentration of 1% to 10% by weight based on the Weight of the water and then heating the water additive combination at a temperature of 175-200 F. for 10 to 60 minutes. The fatty acid salt of the alkali hydroxide forms concomitantly with the dissolution of the dry powder mixture in the heated water. I

After dissolution and formation of the fatty acid salt, the aqueous solution containing the cationically active material and the fatty acid salt is added to the proper pulp whereupon the salt is insolubilized on the paper fibers using a precipitating agent.

The cations of the insolubilized fatty acid salts are desirably aluminum (Al ferric (-Fe and/ or chromic ions (Cr i The precipitating agent which is employed for insolubilizing the water soluble saturated fatty acid salts are water soluble inorganic metal salts of polyvalent metallic ions such as aluminum ferric and chromic. Illustrative of these salts are aluminum sulfate, aluminum chloride, potassium sulfate-aluminum sulfate salts, ferric sulfate and chromic sulfate. The aluminum sulfate and potassium sulfate-aluminum sulfate salts, normally referred to as alums, are preferred in the practice of the present invention. The alum employed may be anhydrous alum,

Al (SO paperrnakers alum, Al (SO 18H O QIMTCOIII mon alum, -K SO Al- (SO -24H 0. When the term alum" is employed in the working examples below, paper makers alum is intended. The precipitating agent is added to the pulp suspension in an amount which will create'f ance with the sizing additive of the present invention may be made up with refined fibers such as bleached-and unbleached fibers, ground wood, soda pulp fibers, semi-' chemical fibers, kraft fibers, sulphite fibers, textile and synthetic fibers, such as viscose rayon and cellulose acetate, and other cellulosic fibers. The pulp is generally re-.

fined to a Canadian Freeness value of from 400-700 milliliters before addition of the sizing additive. The pulp consistency is normally 0.3 to 3.0 percent by weight, although considerable variation is possible.

.The cationically active material is, added .to the pulp suspension at a concentration of 0.10 to 6.0%based on the weight of the solids content of the suspension and preferably 0.70 to 2.0% by weight of the solids content of the suspension. The water soluble fatty acid salt is added to the pulp suspension at a concentration of 0.10 to 10.0% based on the weight of the solids content of the pulp suspension and preferably 0.50.to 6.50%- by weight of the solids content of the suspension.

The following examples further illustrate the practice of the present invention; however theexamples are not to be construed as limiting the scope of the invention.-

EXAMPLE 1 A series of handsheets were made on a Noble and Standard Freeness of '495 milliliters, a pulp consistency of 1% and a pH of 6.85-7.05. The pH of the refined pulp was adjusted to a pH or 8.0-8.05 wartime.

In a series of tests, the sizing additive was added to the pulp suspension in amounts of 0.09% by weight (based on the weight of the solids content of the suspension) Cato 8, a cationic corn starch and 0.41% by weight (based on the weight of the solids content of the suspension) potassium stearate and the pH of the suspension was lowered to 6.0 with 0.59% by weight (based on the dry weight of the fibers) alum. This amount of alum was sufiicient to completely precipitate the stearate salt on the pulp fibers.

Three Cato-S-potassium stearate sizing solutions were used in the test series. The three solutions were prepared in the following manner.

Sizing solution 1 was prepared in the following manner:

86.2 pounds of stearic acid beads and 21.5 pounds of Cato 8 powder were mixed for 30 minutes in a concrete mixer. This period of time was sufiicient to completely coat and encapsulate the stearic acid beads with the Cato 8. Thereafter 17.2 pounds of potassium hydroxide granules were added to the Cato 8 coated stearic acid and the mixing was continued for an additional 30 minutes to blend the potassium hydroxide with the Cato 8 coated stearic acid. The dry powder blend was then stored in polyethylene lined multiwall paper bags. After 4 Weeks, 2 pounds of the powder mixture were removed from the bags. It was observed that the powder had a slight yellowish tint. This dry powder additive mixture was then added to water at a concentration of 5% by weight and heated at 190-195 F. for 30 minutes before being added to the pulp suspension.

Additive solution 2 was prepared in the same manner as solution 1 with the exception that solution 2 was not stored prior to its dissolution in water.

Additive solution 3 was also a 5% solution of Cato 8 stearic acid and potassium hydroxide but was prepared by heating 26.1 grams of KOH with 130.6 grams stearic acid at 190 F. for 5 minutes and then adding thereto 32.6 grams Cato 8.

After formation in the handsheet mold, the handsheets were conditioned at 50% relative humidity at 73 F. for 24 hours prior to being subjected to physical testing. The results of these tests are recorded in Table 1 below.

Watcr drop tcst-Distilled water is dropped onto the paper from a distance of 3 inches and the time in seconds for a single drop (0.05 cc. to be completely absorbed is recorded.

2 Cobb test-Evaluated according to TAPPI Standard '1 441 05-63, felt side exposed to water.

3 Caustic drop test-A single drop (0.05 cc.) 5% N aOH is dropped onto the paper surface from a distance of 3 inches and the time {or the drop to be completely absorbed into the paper is recorded.

4 Bursting strength of paper-Evaluated by TAPPI 20 Standard T 403 ts-63, 150 clamp pressure.

The results recorded in Table I indicate that there is no significant difference in the sizing effectiveness of additive solutions prepared from a dry powder blend of the components (solutions 1 and 2) or an aqueous solution prepared-in the manner of the prior art (solution 3) nor is there any loss in size effectiveness or paper physical properties when the dry powder mixture is stored for an extended period of time (solution 1).

EXAMPLE 2 The procedure of Example 1 was repeated with the exception that the pulp used was 84% pine pulp and 16% hardwood pulp beaten to a Canadian Standard Freeness of 437 mls. and a consistency of 2%. The physical test results of the handsheets prepared in this manner were similar to those of Example 1 and are summarized in Table II below.

TABLE II Paper physical properties Solution number 1 2 3 Oven dry basis weight, 1b./m s.f 48. 8 48. 7 48. 5 Caliper, 1/1,000 inch 15. 6 15. 0 14. 9 Density lb./pt 3.13 3. 25 3. 26 Distilled water drop, seconds 3,888 4, 226 4, 202 2 minute Cobb, grams/m. 35. 6 37. 1 37. 8 Burst, p.s.i 149 176 171 What is claimed is:

1. An additive for incorporation into pulp stock during the manufacture of paper to impart chemical resistance thereto, the additive combination having improved resistance to deliquescence of atmospheric humidity, comprising a dry mixture of (1) a cationically active material selected from the group consisting of cationically active starches and gums and hydrogen bonding starches and gums, (2) an alkali hydroxide, and (3) a fatty acid having 12 to 20 carbon atoms, the fatty acid being coated with a portion of the cationically active material prior UNITED STATES PATENTS 2,129,919 9/1938 File 106--311 3,392,085 7/1968 Oliver 106-211 2,914,412 11/1959 Stephan 106211 2,239,814 4/1941 Edson 106212 653,776 7/1900 Milligau 106-212 THEODORE MORRIS, Primary Examiner US. Cl. X.R.