US2352922A - Paper manufacture - Google Patents

Description

Patented Jul 4,1944

UNITED 'si'Ar raraa mnprsoruaa Joseph J. Thomas, Springfield, Mass, Robert A.

Diehm, Appleton, Wis, andlan 0. Somerville. Philadelphia, Pa., asoignors to Riihm & Haas Company, Philadelphia, Pa.

No Drawing. Application ottoms, 1939,

I Serial No. 298,240 7 60bit!!!- Thisinvention relates to improved methods in the manufacture of paper, whereby the retention of filler is increased, sizing is improved. and sheets of improved uniformity and texture and of'high wet strength are obtained. In particular it deals with the precipitation and dispersion of sizes, particularly of protein sizes,

among paper fibers by a procedure involving the use of syntans.

Glue and casein are often used for the tub sizing and coating of paper, but their use as sizing materials in the-beater for treating pulp which is to be formed into paper sheets has not been practical. The agents for precipitating proteins, previously available, have not been applied successfully for sizing in the beater. While the hardening of glue applied in a tub-sizing operation has been accomplished by formaldehyde, it has not been practical or economical to mix glue and formaldehyde with pulp. When formaldehyde is added tothe beater, it appears While aluminum salts are successfully.

v (cue- 21) stuff and its'fixation. It is a further. object to utilize protein sizing along with other sizing, such as rosin, improving the dispersion of the rosin, and ensuring even distribution of the rosin throughout the fibers and at the same time eliminate difllculties due to the presence of natural resins or pitch in the fibers vor in the water.

These objects are accomplished by the application of a syntan along with a water-soluble protein in the treatment of cellulose fibers before they are formed into a paper sheet.

In preparing paper of superior properties by the use of a water-soluble or lyophilic protein and a syntan, these materials are mixed with cellulose fibers or pulp in water, usually in the beater. Rosin, color, and fillers may be added before or after the protein and syntan. When the stock has been worked to" a satisfactory degree of freeness or the added materials thorthe suspension is adjusted so that it is at about,

-or below, the isoelectric point of the lyophilic available for fixing glue and other proteins have the agents mentioned have been found useful in been ineffective in warm or hot solutions. While some particular phase of paper-making, they have not beenof more general application and have not permitted the improvements which have now been found possible.

'An'object of this invention is to provide a method for preparing paper of improved wet strength. It is also an object to utilize in an improved manner proteins, particularly glues, for

blueprint paper. It is also an object to prepare .sized papers of improved properties, as. shown by ink penetration and writing tests. It is a still further object to produce better formed sheets with increased utilization of fine fibers and better retention of solids, including fillers.

protein which is used. The most commonly used material for lowering the pH to about the isoelectric point is alum. When the proper pH is reached, the protein is precipitated on the fibers, which are then formed into a sheet, which is, in turn, finished in the usual way for the particular type of paper at hand.

The orderof addition of the various materials, pulp, protein, rosin, syntan, coloring material, filler, etc., may be widely varied. If the furnish stock is neutral or slightly alkaline, it may be adjusted to a slightly acid condition by theme of an acid syntan, other-acid such as sulfuric acid, or alum. 11 pH of about 6 is entirely satis-' factory for preventing foam when glue, gelatin,

or other protein is used with a syntan. The

amount of protein added may be varied from 0.2% to 5% of the dry weight of the furnish stock. The quantity of syntan used may be varied from 10% to of the weight of the protein taken. It is preferred to dissolve the protein and the syntan separately and add the solution of each to the suspension of furnish stock, although the syntan and protein can be mixed in solution if the pH of the mixture is kept above the isoelectric point of the protein. Indeed, in the case of rag content papers where better sizing is needed, particularly during hot weather, it, is preferable to mix the syntan and protein before dumping into the beater; or, if the beater has already been I dropped, the glue-syntan can be added to the It is also a further objectto improvethe dyeing of paper, including the dispersion of the -dve-.

machine chest in order to restore sizing to the sheet. ,Starch or rosin sizemay be added and beaten into the mix. Color and filler may also beadded. Thesyntansactasagents for these materials and ensure \miform and even distribution of them throughout the pulp. The syntans also dispersepitch-whlchmay be present, particularly inmechanlcalorunbleached pulps, or gummy substances occurring in the water. If desired. the syntan, in whole or in part, may be added with the rosin size to help insure even distribution of the size and to prevent accumulation of size on the sides of the,

beater, in the valves, or in the pipe lines.

The pH of the mixture of pulp, size, illler, etc.

is preferably adjusted to about the isoelectric' point of the protein just before the nun ns n is to be formed into a sheet. This operation is best accomplished in the beater just before the charge is dropped to'the chest. In the case of animal glues, usually from hoof, hide, or bone,

the desired pH lies between 4.2 and 5.0, with a maximum of eifectiveness at about 4.7.

There may be used in theplace of animal glue any water-soluble, lyophilic, protein colloid such as albumen, gelatin, or even casein. The latter material, however, is somewhat more diilicult to handlethan the others since it must usually be dispersed with alkali and is less eilective.

- Assyntans theremaybeused thewide variety of synthetic materials which have been developed and recognizedintheleatherindustryforthe fixation of hide substance. Typical examples are added, fully acid materials may also be used, at

least to some extent.

The process of forming paper from fibers with the addition .of protein 'anda syntan results in many advantages. There is a high retention oi! flne celluloseilbers. The white water is clearer than in other processes. The syntans'psoperly applied reduce greatlyany dimculties dueto foam. Thesheetisbetterformedandmoreuniformly iormed. probably due to a better filtering medium onthewire. Insomecaseaithasbecnnoted- .thatthe'syntan sivesanartincialslownsastotbe stock which undoubtedly helps account for more even distribution. The better formation of sheets tends to enhance most or the P perties of the paper. l'br example. the paper exhibits increased toughnessthroughout the sheet as shown, for instance. by improved erasing qualities of drawingandledgerpaper. Thewetstrengthofayntanmparedpaperis improved. Rosinusedasasise, is more uniformly and evenly distributed and deposited. Othersislngmateriakarealaomore uniformly and eflectively used when syntans are employed. The improvement in sizing is particularly noticeable in ink penetration and writing The following examples are typical of proce'- dures for improving the preparation of paper.

sample 1.To approximately 40,000 lbs.of

water in the beater are added 2,000 lbs. of cellulose fibers (half sulflte pulp and half ground wood). -The pulp is beaten to the desired freeness and alum carefully added until the pH of the suspension is 6. There is then added a solution containing 10lbs. of hide glue,v followed by the addition of two pounds of the neutral'sodium salt of th formaldehyde condensate of naphthalene sulfonic acid. After mixing has continued for a short time, a rosin emulsion equivalent to 40 lbs. of resin is added followed by mineral filler to the extent of 100 lbs. When these. materials have been well worked in, alum is added until a pH of 4.! is reached. The beater is then dropped to the machine chest, water is added, and the suspension used for making paper in the usual way.

Example 2.About 2500 lbs. of kratt pulp are beaten to the desired degree of freeness in approximately 50.000 lbs. of water. About 5 lbs. of

- the formaldehyde condensateof 4,4-dihydroxy.-

diphenyl sultonesulfonate are added and 15 lbs. of animal glue which has been thoroughly soaked out and taken up in water. color are then. added and another pound of the syntan followed by suillcient alum to bring the followedby30lbs.ofrosinsoapand75lbs.of

clay. After the-mixture is well beaten, about 30 lbs. of alum are added to bring the pH to about 4.6 and paper is formed in the usual way. Over 90% of the glue from the gummed tapeis retained in the Paper.

Example 4.About 1500 pounds of rag stock (properly prepared by cooking, washing, etc.) are "mixed in a beater with'about 80,000 lbs. of water.

tests. Fillers arewell disperaed,evenb distributed and well retainedinthe presenceof syntans. when dyesareu'sed, theyarelikewise-dispersed andmoreeilicieutly utilised. Basicdyesappearto rs andmixingcontinued. I'lnall'yalumtoapliof- 4.5isaddedandthestockdroppedtothechest from which it is, ilowedto' the paper making machine. Improved writing qualities result from mum-lament.

Filler, rosin, and

i 7 2,352,922 an amount between about 10% and about 100% of the weight of said'protein, incorporating filler in the resulting mixture,'adiusting the pH thereof until it is lowered at least to about the isoelectric oint of said protein, forming the mixture into a paper sheet, and drying said sheet.

2. The process of improving the uniformity, texture, and wet strength of paper and increasing the retention of filler therein, which comprises mixing with paper pulp in aqueous suspension animal glue in an amount between 0.2% and about 5% of the dry weight of the paper pulp and asynthetic sulfonated aromatic compound,

having tanning properties, in an amount be-' and a synthetic sulfonated aromatic compound having tanning properties, in an amount between about 10% and about 100% of the weight of the glue, incorporating filler with the pulp, adding alum to the resulting mixture until the pH thereof is brought at least to about the isoelectric point of the. glue, forming the mixture into a paper sheet, and drying said sheet.

4. The process of improving theuniformity. 4

texture, and wet strength of paper and increasing the retention of filler therein, which comprises mixing with paper pulp in aqueous suspension about 5% of the dry weight of the paper pulp and a water-soluble salt of a condensate of naphthalene sulfonic acid and formaldehyde in an amount between about 10% and about 100% of the weight of the glue, incorporating filler with v the pulp, adding alum to the resulting-mixture until the pH thereof is brought at least to about the isoelectric point or the glue, forming the mixture into a. paper sheet, and drying said sheet.

5. In the process of making paper of high wet strength, the improvements which comprise mixing with an aqueous suspension oi-paper fibers animal glue in an amount between about 0.2%

and about 5% of the dry weight of the paper fibers and the sodium salt of naphthalene sulfonic acid condensed with formaldehyd in an amount between about 10% and about 00% of the weight oi! the glue, and subsequently adding alum to the aqueous suspension containing paper fibers, glue, and said sodium salt until the pH of said suspension is brought at least to about the isoelectric point of the glue.

6. In the processoi making paper of high wet strength the improvements which comprise mixing with an aqueous suspension of paper fibers a water-soluble protein in an amount between 0.2% and about 6% or the weight of the paper fibers and a synthetic sulfonated aromatic compound having tanning properties in an amount between about 10% and about 100% of the weight of said protein, and subsequently ad- ,iusting the pH of said suspension at least to about the isoelectric point or the protein.

JOSEPH J. THOMAS. ROBERT A. DIEHM. IAN C. BOMERVIU-E.

' animal glue in an amount between 0.2% and.