US2399748A - Sizing composition for use in papermaking - Google Patents

Description

Patented May 7, 1946 SIZING COMPOSITION FOR USE IN PAPERMAKING Andrew J. Luettge'n, Saring Grove, Pm, assignor,

by mesne syl asllgnmen to P. H. Glaitelter Company, Spring Grove, Pa, a corporation of Penn- No Drawing. Application March 9, 1943, 1 Serial No. 478,527

3 Claims. (Cl. 106-144) This invention relates to sizing compositions for use in Paper making. It provides a sizing material which is relatively low in cost, may be made from readily available materials, is, particularly adapted for long storage or shipment prior to'use. and forms a paper of high-quality.

The sizing of paper is effected either by addin a sizing composition to the paper pulp in. the beater before the pulp is formed into paper or by passing formed paper through a bath of sizingmaterial. The latter operation is generally known as "tub-sizing or calender-sizing." The present invention is herein particularly described as applied to sizes intended for addition to the beater, but in certain circumstances it may be. applicable to tub or calender-sizing as well.

Various materials for the sizin of paper have heretofore been proposed. Generally speaking, paper sizes intended for use in the beater are added thereto in the Iormof emulsions and the sizing element is caused to deposit on the fiber by adding paper-makers alum to the. beater. The cost of the size and the cost of the alum both bulk large in the manufacturing expense.

Sizes have been proposed involving the use of clay and wax, and others have been proposed using rosin and clay; U. S. Patent to Walpuski, No. 313,263, U. S. Patent to Manson, No. 1,990,457. It has also been proposed to use a protective colloid, such as casein, in a size containing, e. 'g., rosin and clay; U. S. Patent to Grasshof et al.. No. 2,271,691. These andlike proposals havehad for manufacture in a Bewoi .found to be quite satisfactory for the purpose.

very stable, give rise to no paper defects when intelligently used and may be made from clays less expensive and more readily available than those heretofore indicated. Moreover, my improved sizes are less expensive in themselves and may be precipitated in the beater with a small amount of alum or other acidifler, thus eil'ecting a double saving.

I give below two specific examples of the mak- I ing of ,my improved size. l miile these may be made in any suitable mixer,fthe examples here are mill, which I have Example 1.-'-Rosin size .(a) 50.1. 12 lbs. of lactic casein in 9 gals. of water at '15-80'F. forabout 5 minutes. Add 9% oz. of caustic soda dissolved in a gallonvof-water to the casein and heat the mixture to about 100 F. with direct steam. This gives a total volume of casein solution of about 10 gals.

(D) From a rosin melting tank draw the equivv alent of 430 lbs. of rosin into the mixer. Start several shortcomings. Sizes-made according to the disclosures mentioned are unstable, a large part of the solids tending to separate'out after a limited period of time, with the result that the sizes become either wholly unsatisfactory for use or else result in the production of an inferior grade of paper or are unsuited for long storage or for shipment over any considerable distance; or in their use cause rosin specks" in the paper; or require the use of specially prepared clays of a. colloidal nature; see, for example, the Manson and Grasshof et al. patents above mentioned. The Manson patent involves the use of colloidal clay. Such clays have a maximum particle size of the general order of micron. The Grasshoi et al. patent employs electro-osmotically treated clay so as to attain a particle size of a diameter much less than 1 micron. Clays of the kinds.

the high-speed agitator at 280 to 300 R. P. M. and

maintain a temperature of approximately 250 F. in the mixer.

(c) Add 6 lbs. of caustic dissolved in 1 to 1% gals.of.water, taking care to add the caustic slowly enough to avoid excess foaming and splashing.

As the causticsolution is being added to the mixer, heat the caseinsolution to approximately 150 F. and at the same time heat water in an auxiliary vessel gals. capacity is suillcient) to approximately 130 F.

((1) Add to the mixer 215 lbs. of either "Satin" or Cosmic A" grade clay (hereinafter. de-- scribed) by running the mill at high speed and adding the clay as fast as good mixing permits.

The temperature of the mix "at this point should not be above 220 F. If any difllculty is encountered in lowering the temperature to this figure. a. thin stream of cold water may be directed into the mill while the clay is being addedtherebelow. It will be found that the mix thickens and the agitation becomes diilicult. Then stir the casein solution into the mix. It-will be found that the level-of the mix will drop several inches on this addition. Now add water from the auxiliary vessel until the mix is away from the shaft and has asmooth appearance. The water should be added cautiously because better results If the size is to be stored for any considerable length of time, a suitable preservative, e. g.

formaldehyde (1 quart), should be added in the.

last stage of mixing.

The concentrated size may be added directly to the beater, or it may be extended with cold water before use. I have found it convenient to extend the size so that it can be metered through a gasoline measuring pump. .This can be done with size previously made up, or it may be done as a final step of the manufacture. In this latter case, following step (1) above, I shift. the Bewoid mill to slow speed and then start adding water at a slow rate and at a temperature of about 85 F. The use of the slow speed avoids spilling over'as this water is added. After about 8 gals. I

of water have been added, the rate at which it is added may be materially increased. The addition of water is continued until the desired percentage of solids has been added. I find that a size containing about 50% solids may be readily handled in a gasoline measuring pump.

Example 2.Wa:r size (a) Heat 210 lbs. of ordinary scale wax" .(unrefined paraflln of low melting point) to 200 1". in the mill and start the agitator at high speed. Add 105 lbs. of clay, such as Satin" or Cosmic A," and mix it thoroughly. The temperature at this point should be between 190 and 200 F.

(D) Add 25 lbs. of Ammonia Soap C (from Harshaw Chemical Company of Cleveland, Ohio) and continue the mixing.

In the meantime, allow 25 lbs. of lactic casein to swell in water and cut with 1% lbs. of caustic soda at 120 to 140 F. Before adding the cut casein to the mix, heat the casein solution to 160-170 F. Add it rapidly to the mix, using high-speed agitation. The temperature atthis point should be about 175 F.

(d) Add water at a temperature of 170 to 175 F. with high-speed mixing. The precise amolmt is gauged by appearance, water being added until the mix smooths out. This will ordinarily require from 2% to 6 gals. As soon as the-mix has smoothed out, stop adding water. Continue the high-speed agitation for about minutes.

Ii the size is to be stored for a considerable manufacture of the size to form an admixture of the fusible binding agent and the clay with a compatible soap prior to the addition of the protective colloid. The mixing of the binding agent, the clay and the soap is effected at a temperature above the fusing point of the binding agent. Preferably, the protective colloid is added when the mix is at a temperature below that at which the major portion of the mixing is done. The procedure Just outlined improves the quality of the size and, where saponiflcation of rosin is effected in the mill, minimizes the possibility of impairment of the protective colloid, e. g., by hydrolysis.

Factors of my invention requiring detailed discussion are particle size and quantity of clay employed, concentration of the size and ratio between the amount of protective colloid used and the amount of alkali employed to cut it. By giving due regard to these factors, a size which remains stable over a long period of time and will yet go into solution readily, which is low in cost and which gives a high quality of paper may be 7 obtained.

Particle size and quantity of clay employed.- The fact that the clays employed need not have particles of such minute dimensions as heretofore found necessary is a commercial important aspect of my invention. I have successfully used Georgia clays from the McIntyre district, produced by Edgar Brothers Company of Metuchen, New Jersey, and known commercially as their Satin" and Cosmic A" grades. Satin" has particles as large as about 4 microns, some 5% of the clay by weight ranging down to 2 microns. Cosmic A is finer, but has particles as large as about 2.5 or 3 microns, some 8-10% of the clay by weight ranging down to 1 micron. These and similar clays are readily available in quantity in the United States, whereas, so far as I am aware. electro-osmotically separated clays are not available in this country, except possibly on a laboratoryscale, and, if obtainable at all, are prohibitive in'price.

My invention not only permits of using lessexpensive clays, but also of using a relatively period before using, add a preservative, e. g. a

lquart of formaldehyde, in the last stage of mix- In lieu of rosin or parailln wax, other fusible binding agents such as other natural and synthetic resins and waxes other than parailln may be used. This is a feature of importance because it permits of using materials most readily available at any particular time. Bituminous or petroleum distillate materials are generally unsuitable. Among other limitations. they are usually so strongly colored that they make the final paper color unsuitable for most purposes. 4

The initial addition of caustic in the rosin size (step b of Example 1 above) results in a saponiflcation of a part of the rosin. Instead of proceeding in this fashion, it is permissible to retofore. The clays which I amable to employ cost considerably less per ton. than the fusible binding agents employed and it is therefore commercially advantageous to use a high percentage of clay in the size. My invention makes it possible to use clay in the amount of 50% of the weight of the binding agent, or even more provided that a sufficiently rugged mixer is avail able.

A size made according to my invention and Indeed, it should not be permitted even to have,

in the fluid state, an unduly high concentration.

The maximum permissible concentration is about 70% solids and for most purposes I prefer a concentration of about 65% solids. In concentrations greater than 70% the size proves exceedingly difficult to handle, particularly in cold weather, and if brought to the solid state it is very resistant to going into uniform suspension in water of any temperature sufflciently low, to inhibit coalescence of the, rosin.

I do nothazard any theory which would account for this difference between my size and those heretofore proposed. It may be due to the fact that I use coarser clays or to the difference in the order of manufacturing steps. At any rate, it indicates a marked difference in the character of the products.

At concentrations of 60-70% my size is remarkably stable and despite the fact that it contains clay particles ranging up to 2.5-3 or even 4 microns, it may be shipped, handled and stored over a period of months without losing the character of a substantially uniformviscous fluid free from aggiomerations or sediment.

My size is readily receptive to the addition of a freezing-point depressant, such as ethylene glycol, which may be adde lii it is desired to protect the size against freezing in cold weather. If no depressant is added, the size will tend to sepggate if exposed to temperatures materially below Even if extended to a lesser concentration than 60-7ti%, the size remains stable for a considerable period of time. In the more dilute forms of the size there issome advantage in the use of Cosmic A clay over Satin clay. At a concentration of for extending the size in quantities for storage and U58.

none of protective colloid to alkali-The Sta bility of the size and its high quality in general will be diminished unless due precautions are taken in its manufacture to observe limiting ratios between the amount of protective colloid used and the amount of caustic employed to cut it.

The protective colloid which I prefer to use is casein, but I may use other proteins, e. g. albumen, vegetable proteins such as those derived from the soy bean, and gelatin. These proteins are effective protective colloids overa wide range of conditions, but in order to achieve my desired resuits the cutting of the colloid must be ,care- .iully controlled so that it neither forms aggregates of denatured protein or hydrolyzes. specific example, as between lactic casein and caustic soda (on an anhydrous basis), the ratio by weight should be a minimum of about 20 casein to 1 of caustic; and a maximum of about 40 casein to' 1 of caustic; that is to say. the caustic should not exceed about 5% of the weight of the By way of casein. or be less than about 2/z%; Better results will be obtained with the higher figure. It will be found that the ratio will differ with different protein protective colloids, and vary somewhat depending on the amount of acid impurities in the colloid (casein). but in each case the principles to be observed are (a) that formation of aggregates of denatured protein,- on the one hand,

tion in viscosity which I believe-to be due to hydrolysis of a substantial part of the casein.

In placeof caustic soda other alkalis, for example caustic potash, or alkaline salts, for example soda ash, may be used to cut the casein, and I comprehend these by the term "alkaline cutting agent. In any case, the rule just stated remains applicable.

My invention makes it possible, by controlling the factors of particle'size a'nd of concentration,

and by observing the principles herein stated as to the cutting of the protective colloid, to make a paper sizing composition which does not deteriorate and is remarkably stable. It is therefore in discharging it from the tank cars in which it is shipped, whereas sizes now on the market, such as rosin soap sizes, must be shipped in special cars and heated therein before it is possible to unload it. My improved size is readily mixable with water at room temperature and'no' dimculty is encountered in extending it either in the heater or preliminarily. It is thus admirably suited for quick use in the paper mill. My size is relatively low in cost. It is made from materials whichare all available in adequate quantities and in such form that the raw material cost is low. As to the several ingredients used, the higher priced ones are in minimum quantity. The manufac-' turing cost is low and the shipping and storage costs are likewise low. The emciency of the size, pound for pound, is higher than that of sizes heretofore employed so that a lesser quantity may be used. The alum. reuuirementsare correspondingly lessened, but the principal saving in alum is dueto the fact that the alum requirements per pound are markedly-low. The use of my improved size results in the production ofpaper of high quality, well sized and tree from rosin specks.

I have described two present preferred embodiments or my invention. It will be understood, howeven'that these are by way of example only and that the invention may be .otherwise embodiedwithin the scope of the following claims.

I claim:

l. A sizing composition for use in paper making, in theform of an aqueous suspension and comprising a binding agent selected from'the class consisting of the fusible resins and waxes, clay in the form oi fine particles, there being particles as large as 2.5 microns, a compatible soap and a proteinaceousprotective colloid, the colloid be ing cut with an alkaline cutting agent in the amount of 2V: to 5 per cent of the weight or the colloid so that hydrolysis of the colloid and 10mmtion of negates of denatured protein are inhibited, whereby the size of the individual par ticles in the sizing composition is uniformly small.

2. A sizing composition for use in paper making, in the form of an aqueous suspension and comprising a binding agent selected from the class consisting of the fusible resins and waxes,-clay in the form of fine particles, there being particles as large as 2.5 microns, a compatible soap and casein cut with an alkaline cutting agent in the amount of 2 /2 to 5 per cent of the weight of the casein, Y

clay in the form of fine particles, there being particles as large as 2.5 microns, a compatible soap and lactic casein out. with caustic soda in the amount of 2 /2 to 5 per cent of the weight of the casein, whereby the size of the individual particles in the sizing composition is uniformly small.

ANDREW J. LUETTGEN.