US3186900A - Sizing paper under substantially neutral conditions with a preblend of rosin and cationic polyamide-epichlorohydrin resin - Google Patents

Description

United States This invention relates to the rosin sizing of paper and more particularly to the rosin sizing of paper at substantially neutral or slightly acid pHs.

In the seizing of paper by the usual rosin size-alum process wherein rosin size is first added to an aqueous suspension of paper pulp and papermakers alum (aluminum sulfate) is then added to precipitae the sizing agent onto the fibers, it has generally been found diificult, if not impossible, to develop satisfactory sizing with most pulps unless the pH of the papermaking system is maintained in the range from about 4.0 to about 5.5. Even under these conditions, some pulps are not readily sized and are, therefore, designated as hard-to-size pulps. Moreover, not only does an acidic system cause corrosion of papermaking equipment, but also it has been demonstrated that paper made under acidic conditions develops less dry strength and has less strength permanence over a period of years. Thus, the discovery of a method whereby a relatively inexpensive sizing agent, such as rosin, could be efiectively applied, particularly to hard-to-size pulps, under neutral or slightly acidic pi-is should prove highly beneficial.

A principal object of the invention, therefore, is the provision of a process for the rosin sizing of paper which is efiective under neutral or slightly acidic conditions.

Another object of the invention is the development of better rosin sizing in paper made from pulps which are hard to size in the conventional rosin size-alum system.

Auxiliary objects of the invention are to improve wet and dry strengths as Well as strength permanence of paper and reduce corrosion of paper-making equipment.

In accordance with the invention, the above and other objects are accomplished by adding a relatively small amount of alum and a preblend of rosin size and a cationic polyamide-epichlorohydrin resin to an aqueous pulp suspension, maintaining the aqueous pulp suspension at a pH from about 6.0 to about 7.5, and sheeting and drying the pulp in the usual manner. The process of the invention has been found to be particularly effective in the sizing of hard-to-size pulps such as southern bleached kraft pulp.

Having described the invention generally, the following examples are given to illustrate specific embodiments thereof. Parts are by weight unless otherwise specified. The rosin size utilized in Examples l-4 and 7-17 was a 3% aqueous emulsion derived from a 70% solids paste tall oil rosin size having an acid number of 23 (dry basis). The rosin size utilized in Examples 5, 6 and -23 was a completely saponified wood rosin size in the form of a 3% aqueous emulsion derived from a 70% solids paste size having an acid number of 24.

The cationic polyarnide-epichlorohydrin resin utilized in the examples was prepared as follows:

Two hundred twenty-five parts of diethylenetriamine and 108 parts of water were placed in a reaction vessel and agitated. To this was added 327 parts of adipic acid.

'ice

After the acid had dissolved in the amine, the solution was heated to 165-470 C. and held there until the reaction was completed. Then 503 parts of Water was added. The resulting poly amide solution contained from 50.0% to 52.0% solids and had an intrinsic viscosity at 25 C. from about 0.115 to about 0.125.

The 100 parts of this polyamide solution was added about 395 parts of Water. This solution was heated to 50 C. and 25.5 parts of epichlorohydrin was added. The mixture was then heated at about C. until it had attained a Gardner viscosity of DE. Then 181.8 parts of water was added to the product, it was cooled to 25 C. to 30 C., and suliicient 10% E01 added to adjust the pH to about 5.0. The product contained about 10% solids and had a Gardner viscosity of C-D.

EXAMPLES 1-6 Various pulps were beaten in demineralized water, with either a Noble and Wood cycle heater or a Valley heater, to a Schopper-Reigier freeness of approximately 750 ml. Pulp slurries were diluted to 2.5 consistency with demineralized water and then were adjusted to a pH of 6.87.2 with H or NaOH.

For control runs, sufiicient 3% rosin size emulsion was added to a 2-liter portion of each 2.5% pulp slurry in the size crock to supply 2% of rosin size solids based on dry pulp. Papermakers alum (aluminum sulfate) was then added to reduce the slurry pH to 4.5. The treated pulp slurry was then diluted to a consistency of 0.27% in the proportioner using acid-alum demineralized water. This dilution water was prepared by reducing the pH of demineralized water to 5.0 with sulfuric acid, then adding enough alum to provide 5 ppm. soluble aluminurn. One-liter portions of the proportioner pulp slurry were then diluted further with acid-alum demineralized water to a deckle box consistency of 0.025% in order to form 40-pound basis weight (24" x 36500 sheet ream) handsheet using a Noble and Wood sheetmaking apparatus. A closed white water system was employed. Formed sheets were wet-pressed to 33% solids content and then dried to 240 F. on a steam drum drier.

For runs involving the preblend process at neutral pH, a 2-liter portion of each 2.5% pulp slurry was first diluted to 0.27% consistency in the proportioner using demineralized water. There was then added 0.2%-0.4% by weight, based on the weight of dry pulp, of alum, followed by 2% by weight, solids based on the weight of dry pulp, of a 1:1 preblend of rosin size and the abovedescribed cationic polyamide-epichlorohydrin resin. In forming the preblend, a predetermined amount of NaOH was first added to a 3% rosin size emulsion in order to maintain the eventual preblend as a clear system. The cationic resin was then blended with this alkaline size emulsion using a 3% solution of the resin. After adding the alum and preblend, the pH of the treated pulp slurry was readjusted to 6.8-7.2 with NaOH. One-liter portions of proportioner slurrry were then diluted with de mineralized water to a deckle box consistency of 0.025% and handsheets were formed, pressed and dried in the same manner as described above.

All handsheets were conditioned for two days at 72 F. and 50% relative humidity and were then tested in this environment. Resistance to penetration by Standard Feather ink was determined by use of the Hercules photometer (D. Price, R. H. Osborn and I. W. Davis, TAPPI 36, 42 (1953)). The time necessary for ink penetration to reduce light reflectance to of the 3 d sheets initial value was used to represent the degree of was produced in experiments where 01-02% alum was SlZll'lg. The sizing data are listed in Table 1. added.

T able 1 Example System Photometer No. Type of pulp Sizing process pI-I sizing (S.F.

ink, sec.)

1 27 of rosin size alum to pH 4.5 4. 5 145 g }Southern bleached kraft 1 {alum 2? M1121 x i i 259 2 o rosin size a um to V .5 260 g i bleached io z aium 2%+oi11:1 peb]ei{1d4 7. 0 219 2 0 rosinsize aurn op ..5- 4.5 263 s iwestem bleached {0.5% alum 2% of 1:1 preblend 7. 0 280 The results indicate that the preblend sizing system at Table 3 neutral pH produced substantially better sizing for paper made from hard-to-size southern bleached kraft pulp Proportiona pH than was obtained using the conventional rosin size-alum Example fgj g fi system at a pH of 4.5. The sizing produced at neutral pH added After After After 333 lit, with the preblend for the western bleached sulfite and I alum pmblelld lggg 566-) easy-to-size western bleached kraft sheets was somewhat 1 better f4 5 than obtalned by the conventional system at a pH None 69 fig 99 o 0.1 65 7.0 7.0 254.

One of the chief benefits of the preblend technlque, as Q2 5 9 257 shown by the above data, is the ability of this system to impart good sizing to a hard-to-size pulp (southern bleached kraft). Another benefit conferred involves the development of good sizing with rosin size in a neutral papermaking system, whereas paper made from most pulps will develop essentially no sizing if treated in the conventional manner in a neutral system.

EXAMPLES 7-13 Sized handsheets were prepared by treating beaten southern bleached kraft pulp in neutral, demineralized water with preblends containing various ratios of rosin size and the polyamide-epichlorohydrin resin described above, after the addition of 0.2% alum. The various blends were prepared by adding the resin to the size emulsion very slowly and adding NaOH when necessary to maintain a clearsystem. Chemical additions were made to a neutral, 0.27% slurry in the proportioner in the manner described in Examples 16, and handsheets were formed in the usual way.

The etfect of the size/resin ratio on development of sizing in the paper is shown by the results in Table 2. A 1:1 preblend ratio gave the best sizing, although ratios of 2:1 and 1:2 also produced good sizing. Still higher ratios of size/resin produced mediocre sizing, while preblends containing very little size led to little or no sizing development.

Table 2 Preblend composition Photometer Example sizing No. Percent (SF. ink,

Percent polyamide- Ratio, sec.) rosin size epichiorohysize/resin drin resin EXAMPLES l4-16 SiZed handsheets using varying amounts of alum and 2% of ,a 1:1 preblend of rosin size and the above-described polyamide-epichlorohydrin resin were prepared from beaten southern bleached kraft pulp in a neutral papermaking system as described in Examples l-6. Results listed in Table 3 demonstrate the effect of the alum furnish on the sizing efliciency of the preblend. When no alunfwas added, poor sizing was obtained. Good sizing EXAMPLES 17-19 Southern bleached kraft pulp was sized in the manner described in Examples 1-6 using 0.2% alum and 2% of 1:1 preblends containing the above-described polyamideepichlorohydrin resin and various rosin sizing agents. The experiments involved regular rosin size, as utilized in Examples 1-4 and 7-16, fortified rosin size, and high free rosin emulsion. All preblends were adjusted to a pH of 11.2-11.8 with NaOI-I.

The sizing results are listed in Table 4. They show that the neutral pH, preblend sizing system is quite eifective with all three types of rosin size.

Table 4 Preblend composition Photometer Example Polyamidesizing No. epichloro- .F.

Sizing agent hydrin ink, resin, sec.) percent 1.0% rosin size 1. 0 261 1.0% fortified rosin size 1. 0 236 1.0% high free rosin emulsion 1.0 235 EXAMPLES 20-23 These experiments involved southern bleached kraft, beaten and used in a distilled Water system, and western bleached kraft, beaten and used in tap water (mild alkalinity and hardness). Both systems were adjusted to a pH of 6 with acid or alkali. Treatment of southern bleached kraft involved 0.5% alum, 1% rosin size (completely saponified) and 0.5 of the above-described 'polyamide-epichlorohydrin resin. The size and resin were added (1) as a preblend to the crock before the alum and (2) as a preblend after alum at the proportioner.

Treatment of :western bleached kraft involved 0.5% 'alum,'1% rosin size, and 0.5% of the above-described 'polyamide-epichlorohydrin resin added in the same two .ways described above. Aside from method and point of addition, the sizing and sheetmaking procedures were es sentially the same as described in Examples 1-6.

The results listed in Table 5 show that preblend addition at the proportioner is the most eitective sizing procedure where southern bleached kraft is concerned, whereas addition to the size crock is the most eff ctive sizing procedure where western bleached krait is concerned.

mole, per mole of rosin, of an acidic compound containing the group including a,B-unsaturated monobasic and polybasic organic acids and acid anhydrides such as acrylic, maleic, fumaric, itaconic and c-itraconic acids and their anhy- Tuba: 5

Chemical additions Handshect properties Ex. Pho- No. Basis tometer To size crock To proportioner weight sizing (lb/R.) (S.F. ink, 1 sec.) I

(Southern bleached Matt-distilled water system at pH=6) 20.... Size-resin preb1end 0.5% alum 4... 1 202 21.. 0.5% alum pr 40. 7 356 (Western bleached kraittap Water system at pH=6) 22.... Size-resin preblend 0.5% alum 40. 3 618 23. 0.5% alum sizeresin preblend 39. 2 315 In accordance with the invention, a small amount of alum and a preblend of rosin size and cationic polyamideepichlorohydrin resin in a Weight ratio of rosin size to resin of from about 2:1 to about 122 are added to a dilute slurry of paper pulp in a substantially neutral papermaking system. In the case of a hard-to-size pulp, and where the alum is added before the resin size-resin preblend, this treatment develops better sizing than can be obtained for this type of pulp by the conventional rosin size-alum system at any pH. In the case of an easy-tosize pulp, such as Western bleached kraft, better sizing is Y obtained by adding the preblend and then the alum to the size crock than is obtained by adding these in the reverse order to the proportioner. While the alum and the preblend can thus be added in any desired order, including simultaneously, optimum results in the case of hard-tosize pulps, to which the process of the invention is particularly applicable, are obtained if the alum is added first. This, therefore, is the preferred procedure.

The pH of the papermaking system should be maintained within the range from about 6.0 to about 7.5 in order to realize the advantages of the invention. However, the preterred pH range is from about 6.8 to about 7.2. The amount of preblend added can be varied from about 0.5% to about 5% or more by weight, based on the Weight of dry pulp. The amount of alum added to the system can range from about 0.1% to 0.5% or even more, say up to about 2%, as long as the system is adjusted to, and maintained at, a pH from about 6.0 to about 7.5.

The term hard to size, as utilized herein, means pulps which are generally difiicu-lt to size by the conventional rosin size-alurn process. In general, highly purified (e.g., high tx-CfilllllOSB) pulps such as southern bleached kraft, certain types of bleached sulfite, cotton linters, and rag fibers are hard to size.

The term rosin size, as used herein, means any of the rosin sizes known to the art and includes sizes made from wood rosin, gum rosin, and tall oil rosin in crude or refined state and/ or after treatment of various kinds to increase its effectiveness for the intended purpose. it also includes sizes made from modified rosins, such as partially or substantialiy completely hydrogenated rosins and polymerized rosins, as well as rosins which have been heat treated, reacted with formaldehyde, or otherwise treated to inhibit crystallization of the rosin or sizes preprepar'ed therefrom.

Sizes prepared from rosins containing or which have been admixed with various fortifying agents can also be used. Rosin compositions of this type are desirably prepared by reacting rosin with from one-twentieth to one drides. Products of this type and methods of preparing and using same are well known as shown, for example, in US. 2,628,918 and US. 2,684,300.

The invention also contemplates the use of sizes prepared from rosins or rosin compositions, such as that described above, containing varying amounts of fatty acids or fatty acid mixtures. For example, there can be used a tall oil rosin fraction obtained by the fractional distillation of tall oil and containing up to several percent of a tall oil fatty acid mixture.

In the preparation of these sizes, e.g., sizes containing from about 50% to about 86% or more total solids, the rosin is warmed to about -150 C., preferably (3., and aqueous alkali, i.e., aqueous alkali metal hydroxide or carbonate, is added. During this addition, the temperature gradually reduces and heat is applied, as required, until the reaction is substantially complete. Sufficient water can be added in the aqueous alkali to provide the desired total solids in the paste, or, alternatively, water may be added or removed during or after the reaction to obtain the desired solids. The amount of alkali used will depend on the degree of saponification or neutralization desired. Generally, a partial neutralization of the rosin acids to the extent of from about 7( to about 95% is desirable unless the paste is to be converted to a dry size, in which event substantially complete neutralization is preferred.

The cationic polyamide-epichlorohydrin resins contemplated for use herein are Water-soluble polymeric condensation products of epichlorohydrin and a polyamide derived from a polyalkylene polyamine and an aliphatic dicarboxylic acid. In the preparation of these products, the dicarboxylic acid is first reacted with a polyalkylene polyarnine under conditions such as to produce a waters-oluble polyamide containing the recurring groups where n and are each two or more and R is the divalent hydrocarbon radical of the dicarboxylic acid. This watersoluble polyarnide is then reacted with epichlorohydrin to form a Water-soluble cationic thermosetting resin.

The dicarboxylic acids contemplated for use in preparing these resins are diglycolic acid and saturated aliphatic dicarboxylic acids preferably containing from 3 to 8 carbon atoms such as succinic, glutaric, adipic and the like. Of these, diglycolic acid and the saturated aliphatic dicanboxylic acids having from 4 to 6 carbon atoms in the molecule, namely, succinic, glutaric and adipic, are most preferred. Blends of two or more of these dicarboxylic acids may also be used, as well as blends of one or more of these with higher saturated aliphatic dicarboxylic acids such as azelaic and sebacic as long as the resulting longchain polyamide is water soluble.

A variety of polyalkylene polyamines including polyethylene polyamines, polypropylene polyamines, polybutylene polyamines and so on may be employed herein of which the polyethylene polyamines represent an economically preferred class. More specifically, the polyalkylene polyamines contemplated for use herein are polyamines containing two primary amine groups and at least one secondary amine group in which the nitrogen atoms are linked together by groups of the formula -C,,H where n is a small integer greater than unity and the number of such groups in the molecule ranges from two up to about eight, and preferably up to about four. The nitrogen atoms may be attached to adjacent carbon atoms in the group C,,H or to carbon atoms further apart, but not to the same carbon atom. This invention contemplates not only the use of such polyamines as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, and the like, which can be obtained in reasonably pure form, but also mixtures and various crude polyamine materials. For example, the mixture of polyethylene polyamines obtained by the reaction of ammonia and ethylene dichloride, refined only to the extent of removal of chlorides, water, excess ammonia, and ethylenediamine, is a very satisfactory starting material. Most preferred are the polyethylene polyamines containing from two to four ethylene groups, two primary amine groups,

and from one to three secondary amine groups.

The term polyalkylene polyamine employed in the claims, therefore, refers to and includes any of the polyalkylene polyamines referred to above or to a mixture of such polyalkylene polyamines.

It is desirable, in some cases, to increase the spacing of secondary amine groups on the polyamide molecule in order to change the reactivity of the polyamide-epichlorohydrin complex. This can be accomplished by substituting an aliphatic diamine such as ethylenediamine, propylenediamine, hexamethylenediamine or a heterocyclic diamine such as piperazine or the like for a portion of the polyalkylene polyamine. For this purpose, up to about 60% of the polyalkylene polyamine may be replaced by a molecularly equivalent amount of the diamine. Usually, a replacement of about 30% or less will serve the purpose.

The temperatures employed for carrying out the reaction between the dicarboxylic acid and the polyalkylene polyamine may vary from about 110 C. to about 250 C. or higher at atmospheric pressure. For most purposes, however, temperatures between about 160 C. and 210 C. have been found satisfactory and are preferred. Where reduced pressures are employed, somewhat lower temperatures may be utilized. The time of reaction depends on the temperatures and pressures utilized and will ordinarily vary from about /2 to 2 hours, although shorter or longer reaction times may be utilized depending on reaction conditions. In any event, the reaction is desirably continued to substantial completion for best results.

In carrying out the reaction, it is preferred to use an amount of dicarboxylic acid sufiicient to react substantially completely with the primary amine groups of the polyalkylene polyamine but insufficient to react with the secondary amine groups to any substantial extent. This will usually require a mole ratio of polyalkylene polyamine to dicarboxylic acid of from about 0.9:1 to about 1.221, and preferably from about 0.92:1 to 1.14:1. However, mole ratios of from about 0.811 to about 1.421 may be used with quite satisfactory results. Mole ratios outside of these ranges are generally unsatisfactory. Thus,

" mole ratios below about 0811 result in a gelled product or one having a pronounced tendency to gel, While mole ratios above 1.4:1 result in low molecular weight polyamides.- Such products do not produce efficient resins for'the purpose herein described when reacted with epichlorohydrin.

In converting the polyamide, formed as above described, to a cationic thermosetting resin, it is reacted with epichlorohydrin at a temperature from about 45 C. to about C., and preferably between about 45 C. and 70 C., until the viscosity of a 20% solids solution at 25 C. has reached about C or higher on the Gardner-Holdt scale. This reaction is preferably carried out in aqueous solution to moderate the reaction. pH adjustment is usually not necessary. However, since the pH decreases during the polymerization phase of the reaction, it may be desirable, in some cases, to add alkali to combine with at least some of the acid formed.

When the desired viscosity is reached, sufficient water is then added to adjust the solids content of the resin solution to the desired amount, the product cooled to about 25 C. and then stabilized by adding sufiicient acid to adjust the pH to about 6, and preferably to about 4 or less, e.g., from about 2 to about 4. Any suitable acid such as hydrochloric, sulfuric, nitric, formic, phosphoric, and acetic acid may be used to stabilize the product.

In the polyamide-epichlorohydrin reaction, it is preferred to use suificient epichlorohydrin to convert all secondary amine groups to tertiary amine groups and/or quarternary ammonium groups including cyclic structures. However, more or less may be added to moderate or increase reaction rates. In general, it is contemplated utilizing from about 0.5 mole to about 1.8 moles of epichlorohydrin per mole polyamide secondary amine. It is preferred to utilize from about 0.9 mole to about 1.5 moles of epichlorohydrin per mole of polyamide secondary amine group. 7

The present invention provides a number of important advantages including (1) the provision of a method for effectively sizing a hard-to-size pulp, e.g., southern bleached kraft pulp which has been bleached withchlorine dioxide, and (2) the provision of a method for effectively sizing various pulps in a neutral papermaking system, thereby avoiding or reducing the corrosion difiiculties which are encountered in an acidic papermaking system. In additon to the above, the process of the invention results ina Well-sized sheet of improved dry strength, wet strength, and strength permanence. Thus, reducing the environmental acidity contributes to both dry strength and its permanence, while the introduction of cationic polyamide-epichlorohydrin resin improves both wet and dry strength.

The present invention is particularly useful in mills where a hard-to-size pulp must be converted into a wellsized paper and in mills where a high pH paperrnaking system is required or where it is desired in order to reduce equipment corrosion. It is also useful in any mill where the fringe benefits of improved sheet wet strength, dry strength, and strength permanence are desired, together with sizing.

What I claim and desire to protect by Letters Patent is:

l. The method of sizing paper which comprises adding to an aqueous pulp suspension at a pH from about 6.0 to about 7.5 from about 0.1% to about 2% by weight, based on the dry weight of pulp, of alum and from about 0.5% to about 5.0% by weight, based on the dry weight of pulp, of a preblend of rosin size and a cationic polyamideepichlorohydrin resin in a weight ratio of rosin size to resin of from about 5:1 to about 1:2, said cationic polyamide-epichlorohydrin resin being obtained by reacting a polyalkylene polyamine with a dicarboxylic acid selected from the group consisting of diglycolic acid and C -C saturated aliphatic dicarboxylic acids. in a mole ratio of from about 0.8 to about 1.4 of the former to about 1.0 of the latter to form a long-chain polyamide, and then reacting the polyamide with epichlorohydrin in a mole ratio of epichlorohydrin to secondary amine groups of said polyamide of from about 0.511 to about 1 .821, maintaining the pH of the aqueous pulp suspension from about 6.0 to about 7.5, and forming the pulp into sheets.

2. The method of sizing paper which comprises adding to an aqueous pulp suspension at a pH from about 6.0 to about 7.5 from about 0.1% to about 0.5% by Weight, based on the dry weight of pulp, of alum, adding to the resulting suspension from about 0.5% to about by weight, based on the dry Weight of pulp, of a preblend of rosin size and a cationic polyamide-epichlorohydrin resin obtained by reacting a polyalkylene polyaminc with a dicarboxylic acid selected from the group consisting of diglycolic acid and C -C saturated aliphatic dicarboxylic acids in a mole ratio of from about 0.8 to about 1.4 of the former to about 1.0 of the latter to form a long-chain polyainide, and then reacting the polyamide with epichlorohydrin in a mole ratio of epichlorohydrin to secondary amine groups of said polyamide of from about 0.5:1 to about 1.8:1, the ratio of rosin size to resin in said preblend being from about 2:1 to about 1:2, maintaining the pH of the aqueous pulp suspension from about 6.0 to about 7.5, and forming the pulp into sheets.

3. The method in accordance with claim 1 wherein the rosin size is a fortified rosin size containing the reaction product of rosin with from one-twentieth to one mole, per mole of rosin, of an acidic compound containing the group.

4. The method in accordance with claim 1 in which the rosin size is prepared from a tall oil rosin fraction derived from tall oil.

10 5. The method in accordance with claim 2 wherein the rosin size is a fortified rosin size containing the reaction product of rosin with from one-twentieth to one mole, per mole of rosin, on an acidic compound containing the \C=C 0:0 l I group.

6. The method in accordance with claim 2 in which the rosin size is prepared from a tall oil rosin fraction derived from tall oil.

References fitted by the Examiner UNITED STATES PATENTS 1,840,399 1/32 Lane 162179 2,544,887 3/51 Leonard 162180 2,601,597 6/52 Daniel et al 162164 2,926,116 2/60 Keim 162-464 2,994,635 8/ 61 Reaville et a1. 162-179 3,096,231 7/63 Griggs et a1 162-179 FOREIGN PATENTS 10,760 1845 Great Britain. 461,272 2/37 Great Britain. 711,404 6/ 54 Great Britain. 790,198 9/ France.

DONALL H. SYLVESTER, Primary Examiner. MORRIS O. WOLK, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,186,900 June 1, 1965 Frederick B. De Young It is hereby certified that error a ppears in the above numbered patent requiring correction and that the sa id Letters Patent should read as corrected below.

Column 1, line 14, for "acid" read acidic line 15, for "seizing" read sizing column 2, line 7, for "The" read To Signed and sealed this 19th day of October 1965.

'SEAL) Quest:

RNEST W. SWIDER EDWARD J. BRENNER testing Officer Commissioner of Patents

Claims (1)

1. THE METHOD OF SIZING PAPER WHICH COMPRISES ADDING TO AN AQUEOUS PULP SUSPENSION AT A PH FROM ABOUT 6.0 TO ABOUT 7.5 FROM ABOUT 0.1% TO ABOUT 2% BY WEIGHT, BASED ON THE DRY WEIGHT OF PULP, OF ALUM AND FROM ABOUT 0.5% TO ABOUT 5.0% BY WEIGHT, BASED ON THE DRY WEIGHT OF PULP, OF A PREBLEND OF ROSIN SIZE AND A CATIONIC POLYAMIDEEPICHLOROHYDRIN RESIN IN A WEIGHT RATIO OF ROSIN SIZE TO RESIN OF FROM ABOUT 5:1 TO ABOUT 1:2, SAID CATIONIC POLYAMIDE-EPICHLOROHYDRIN RESIN BEING OBTAINED BY REACTING A POLYALKYLENE POLYAMINE WITH A DICARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF DIGLYCOLIC ACID AND C3-C8 SATURATED ALIPHATEIC DICARBOXYLIC ACIDS IN A MOLE RATIO OF FROM ABOUT 0.8 TO ABOUT 1.4 OF THE FORMER TO ABOUT 1.0 OF THE LATTER TO FORM A LONG-CHAIN POLYAMIDE, AND THEN REACTING THE POLYAMIDE WITH EPICHLOROHYDRIN IN A MOLE RATIO OF EPICHLOROHYDRIN TO SECONDARY AMINE GROUPS OF SAID POLYAMIDE OF FROM ABOUT 0.5:1 TO ABOUT 1.8:1, MAINTAINING THE PH OF THE AQUEOUS PULP SUSPENSION FROM ABOUT 6.0 TO ABOUT 7.5, AND FORMING THE PULP INTO SHEETS.