US2116768A - Sizing paper - Google Patents

Description

Patented May 10, 193

UNITED srA'r stituteo! Paper corporation of NoDrawing. Application December 7, 1934,

Serial No. 756.533

s Claims. ((21. 134-450) peanuts, etc., as well as the leguminous flour itself ;-I may also use other proteins which ifunc- My invention relates to the sizing of paper andhus to do more particularly with an improvement in so-calledengine sizing, wherein rosin and a setting agent are commonly used. 4 The-paper art has for many years been familiar with this type of sizing. which is used particularly in the manuiacture of printing'papers and the like. As usually practiced, this process consists in adding to the'pulp in the hollander or beater a solution of mixed sodium resinate and free rosin resulting from a partial neutralization of rosin ,by alkali (prepared by boiling rosin with soda ash) and, after the beating operation, adding a substantial quantity of a solution of aluminum sulphate or paper-maker's alum. According to the generally accepted theory, the ensuing reaction results inth'e precipitation of free rosin. which, with some alumina, becomes attached to the fibers and forms a varnish-like coating on .the sheet after it is passed between the hot calender rolls.

It has been supposedwithin recent years that the eiiectivenessoi sizing or this type depends to a large extent upon the smallness or the particles of resin deposited upon the fiber; that is to say that, generally speaking, the smaller the par- -.ticles the more eflective the sizing. In accordance with this theory, it has been proposed that the resin .be dispersed by means of mill 30 without the use of. a1kali, and it has also been proposed (Wieger United States Patent No. 1,882,680, October 18, 1932) to prepare the sining solution by heating the resin in the neighborqhood of. its melting point in the presence of an alkaline solution containing a protective colloid, such a casein. All or these prior-art proposals have been and are subject to serious objections. It will be seen that in these methods an attempt" is made physically to subdivide the resin to obtain particles of colloidal size.

In accordance vnth my invention there is produced a size of colloidal resin by the method of molecular condensation or aggregation, with numerous advantages which will become appar- 45 cut.

Iv have found that protein matter suspended in the presence of alkali resinates, functions si-' .flciently as an alkali binder, i. e., to abstract the alkali and thus ireethe resin in form ofan emulsion or suspension, from which it can be deposited on the fiber in particles of colloidal dimension. As examples o! proteins which'I have ioundsatisiactory; I mention the "casein" extracted from soy bean hour as well as that ob- 55 tained from other leguminous materials, such as as I . srzmc rsran Ben W. Rowland, Appleton, Wis.,-aesignor toInmilk casein, glue, etc. to the action here described by the electrolytic 5 myself to any theory of operation.

cent of the dry weight of the stock;

solution of sodium resinate of a strength of, say

exces's oi 'free rosin but containing no alum, is addedaproteinous. material as'described above.

. partially or wholly, depending upon the condi tions. This will be" indicated by increasing and extended by heating to temperatures gen- -mixtures, such as have the property of lowering PATENT owes r1, Appleton, Win. a

tion as hydrophilic emulsoid colloids, such as For convenience I reier term of hydrolysis", although I do not restrict Example The following is a preferred example of my invention, it being'understood that the same is merely illustrative and not in any sense limiting. The heater is furnished with stock in the usual way except that no alum or white water containing the same is introduced. After the beat- 5 ing operation-is substantially completed, my improved sizing material is added. The quantity of size may, of course, vary within wide limits, depending l n'the nature of .the pulp and the quality of the paper intended to be, produced Roughly, the amount of dry size in the sizing solution may usually represent from 1 to 2 per to. improved sizing material justreierred to may be prepared as follows: To an aqueous.

2 per cent and preferably containing a slight for example, soy bean casein. The proportion oi protein added may vary considerably, and I have found that my process may be practiced satisiactorily with from .10 to 50 per cent or more or less of dry; protein based on the weight of dry sodium 'resinate, although I preier to operate within the range just specified." The mixture is allowed to stand until the protein has become 1 dispersed and the resin soap has been hydroliaed turbidity of. the liquid. The reaction may be improved by moderate stirring and also hastened erally not-exceeding approximately ao-c., but in some cases up to the-boiling point.

' The reaction may be improved and extended by the addition of very small quantities of dilute acidic materials, and preferably by the 1 addition of butler mixtures,:such as boric acidalkali monoand di-basic phosphate the alkalinity of the sodium resinate solution without overstepping into a zone of acid precipitation. The final pH value should not be below about I pH. to

As stated above, I prefer to use at least 10 per cent or more of protein material based on the weight of sodium resinate, but my invention is not limited to this minimum. In fact, I have found that my process will operate with much smaller quantities of protein, say, froml to 5' ing within the spirit of my invention as set forth per cent.

In the use of my improved size described above, the liquid is introduced into the beater or hollander, as stated above, preferably after most of the beating operation has been completed. will be desirable at this point to add suflicient acid-reacting material to render the stock neutral (pH 7.0) or slightly acid, preferably of a pH between 6.0 to 6.8. Usually this will require the addition of only atrace of acid, and care should be taken to avoid too high an acidity. If the stock is alkaline, excessive foaming is likely to occur and also the sizing efiect is greatly reduced, while, if the acidity is too high, the size tends to precipitate in large flocks, and thus the deposit of colloidal particles as contemplated by my invention is not obtained. Forproducing this change in acidity, I prefer, for purposes-of convenience and economy, to use paper-maker's alum, although I may also use practically any acid, such as acetic, hydrochloric, etc., or any acid salt, as well as alum, such as aluminum chloride.

Sizing in accordance with my invention presents many advantages. Thus, I am able to produce a size effect against water penetration offrom 200 to 300 per cent better than that obtained from ordinary rosin size. The process is easy to carry out inasmuch as no special equipment is required either for the preparation of the size orfor its application to the stock. Furthermore, the composition of the size can be accurately adjusted to meet the furnish conditions, which is a very great advantage, since various pulps require different amounts of free rosin in order to be properly sized.

A further advantage accrues from the fact that my improved size gives the best results at the neutral or very slightly acidconditions of the furnish, thereby insuring a lower acidity in the sheet than is customary with the usual rosin sizing. This results in greater permanence of the sheet as well as in less damage to equipment than occurs under the strongly acid conditions of ordinary sizing.

Various other advantages resulting from myinvention will be apparent to those skilled i the art.

Numerous variations and modifications comabove will no doubt suggest themselves to those skilled in the art. Hence, I do not wish to be limited to the specific embodiments or details herein given but intend thatthe scope of my invention is to be limited only by the appended claims, which are to be interpreted as broadly as ,will be permitted by the state of the art.

While I refer specifically herein to rosin sizl5 solution containing acid 'precipitable colloidal particles of rosin which comprises adding to a dilute aqueous solution of alkali resinate about 10 to 50 per cent soya bean-casein based on the weight of the alkali resinate, allowing-the mixture to stand until the casein has become dispersed and the alkali resinate has become at least partially hydrolyzed as indicated by the increasing turbidity of the solution.

2. A method of preparing a paper pulp sizing solution containing acid precipitable colloidal particles-of rosin which comprises adding to a dilute aqueous solution of sodium resinate' containing a slight proportion of free rosin about 10 to 50 per cent soya bean casein based on the weightof the sodium resinate, stirring themixture until the casein has been dispersed and the sodium resinate has become partially hydrolyzed as indicated by the increasing turbidity of the solution, and finally adjusting the solution to a pH value of about '1 by the addition oia small .40

quantity of weakly acidic buffer material;

3. A paper pulp sizing solution having a pH value of about 7 and containing acid precipitable I colloidal particles of rosin, comprising, the reaction product of a dilute aqueous alkali resinate 5 solution with about 10'to per cent casein protein based, on the weight of the alkali resinate.

BEN ROWLAND.