EP0151994B1

EP0151994B1 - Method of preparing an improved sizing agent and novel paper sizing method

Info

Publication number: EP0151994B1
Application number: EP19850100782
Authority: EP
Inventors: Dominic S. Rende; Michael D. Breslin
Original assignee: Nalco Chemical Co
Current assignee: ChampionX LLC
Priority date: 1984-01-27
Filing date: 1985-01-25
Publication date: 1991-08-07
Anticipated expiration: 2005-01-25
Also published as: PL251704A1; EP0151994B2; BR8500339A; PL148735B1; DK34085A; MX166763B; NZ210958A; FI850296L; FI850296A0; CS264115B2; FI81860B; AU3800485A; EP0151994A3; AU577735B2; DK172016B1; DK34085D0; ES539847A0; FI81860C; EP0151994A2; ES8609428A1

Description

Alkenyl succinic anhydrides (ASA) useful in the sizing of cellulosic materials have gained considerable commercial success. These materials were first fully disclosed in U.S. patent 3,102,064. This patent discloses a certain class of chemical materials generally having the structural formula
wherein R represents a dimethylene or trimethylene radical, and wherein R¹ is a hydrophobic group containing more than 5 carbon atoms which may be selected from the group consisting of alkyl, alkenyl, aralkyl or aralkenyl groups. For effective utilization, the sizing agents must be used in conjunction with a material which is either cationic in nature or is capable of ionizing or disassociating in such a manner to produce one or more cations or other positively charged groups. The cationic agents are disclosed as "alum, aluminum chloride, long chain fatty amines, sodium aluminate, polyacrylamide, chromic sulfate, animal glue, cationic thermosetting resins, and polyamide polymers". Preferred cationic agents are the various cationic starch derivates including primary, secondary, tertiary, or quaternary amine starch derivates and other cationic nitrogen substituted starch derivates, as well as cationic sulfonium and phosphonium starch derivatives. Such derivatives may be prepared from all types of starches including corn, tapioca and potato. A similar paper sizing composition is the subject matter of the EP-A 122 617. This composition contains two different ASA compounds and a dispersing agent which may be selected from the group consisting of cationized starch, gelatine, polyvinyl alcohol, cationic polyacrylamide and polyethyleneimine.
With the growing commercial use of sizes of the type above described, serious problems have remained in the application of the sizes to paper stock or pulp prior to its formation into sheet or other useful forms. Part of the problem has been that the ASA sizing materials are not water soluble, and must, accordingly, be uniformly suspended in the pulp so that the size can make adequate contact with the cellulosic fibers and thus create the desired effect of the final product.
In the EP-A 85 330 sizing agents are disclosed which comprise 1 - 60 parts by weight of a sizing accelerating agent per 10 parts by weight of a hydrophobic sizing such as ketene dimers. Useful accelerators are polymers containing primary, secondary or tertiary amino and/or quaternary ammonium groups directly bonded or present as pendant groups, such as a quaternized terpolymer which contain N,N-dimethylaminoethyl methacrylate, styrene and methyl methacrylate, acrylonitrile or n-butylacrylate units. ASA sizings are not exemplified or tested. Although the molecular weight of these polymers is not specificly investigated it seems that the tested sizing accelerators are high molecular weight water-soluble polymers.
The US patent 36 66 512 discloses an aqueous sizing dispersion consisting of hydrophobic paper- sizing carboxylic acid anhydride particles and a latent catalyst therefor which is a water-soluble salt of a cationic polyamine having a molecular weight of more than 1,000. Thus a distearic acid anhydride sizing is catalyzed with the polyamine salt of cationic starch.
The method of US patent 4 040 900 for sizing paper products utilizes a sizing emulsion consisting of 80-97 parts of substituted cyclic dicarboxylic anhydride such as ASA and 3-20 parts of a polyoxyalkylene alkyl or alkylaryl ether or the corresponding mono or diester. In the paper stock a cationic retention agent can be dispersed.
In the JP-A 58-45730 a papermaking sizing agent is disclosed which consists of an aqueous dispersion of substituted succinic anhydrides wherein the aqueous medium also contains an ampholytic acrylamide type polymer. Preferably this ampholytic polymer is an acrylamide type polymer having 3-50 mol% of cationic groups and 5-15 mol% of anionic groups. The cationic groups can be the result of a Mannich reaction. The term "ampholytic" does not include the cationic or cationically modified vinyl addition polymers used in the present invention.
The EPA 141 641 (post-published) discloses aqueous sizing dispersions prepared by dilution of anhydrous concentrates comprising a reactive size such as ketene dimer or alkenyl succinic anhydride and a polyelectrolyte which can be cationic, anionic or non-ionic. Copolymers of aerylamide with quaternized dimethylaminoethyl acrylate or methacrylate can be used as cationic polyelectrolyte. An advantage is that the polyelectrolyte can have a higher molecular weight. Tested compositions contain polyelectrolytes which have a molecular weight in the order above 10⁶.
While the cationic agents disclosed in U.S. patent 3,103,061 have met with success, there has been a need within the paper industry to provide a more effective "cationic agent" for ASA sizes. In addition, such cationic agent should preferably aid in the retention of the size on the fiber, and should increase, where desired, the wet and/or dry strength of the final sheet material.
It is an object of this invention to provide an emulsified sizing agent containing an additive which will serve to emulsify or disperse the ASA size in the pulp and allow for retention of the size onto the fiber, without impairing the runnability of the paper machinery.
The present invention provides a method for preparing an emulsified sizing agent useful in the preparation of sized paper products, such emulsion containing water, a cyclic dicarboxylic acid anhydride having the following structural formula:
wherein R represents a dimethylene or trimethylene radical, and wherein R¹ is a hydrophobic group containing more than 5 carbon atoms which may be selected from the group consisting of alkyl, alkenyl, aralkyl or aralkenyl groups, and a water soluble cationic vinyl addition polymer, characterized in that the cationic vinyl addition polymer has a molecular weight of between 20.000 and 750.000 and is made of at least 10 weight-% and up to 100 weight-% of the mer content of the polymer from one or more cationic or cationically modified vinyl addition monomers selected from the group consisting of

a) diallyldimethyl ammonium chloride;
b) methacrylamidopropyltrimethyl ammonium chloride;
c) dimethylaminoethylmethacrylate;
d) dimethylaminoethylmethacrylate quaternaries;
e) dimethylaminoethylacrylate;
f) dimethylaminoethylacrylate quaternaries;
g) diethylaminoethylacrylate;
h) diethylaminoethylacrylate quaternaries;
i) acrylamide reacted with formaldehyde and a lower secondary amine through the Mannich reaction; and
j) manniched acrylamide quaternaries.

In addition the present invention provides a method for the sizing of paper, wherein such an emulsion of a cyclic dicarboxylic acid anhydride is applied to the paper stock and the cyclic dicarboxylic acid anhydride is emulsified by the water soluble cationic vinyl addition polymer.
Above that the present invention also provides an emulsion of a cyclic dicarboxylic acid anhyride having the following structural formula:
wherein R represents a dimethylene or trimethylene radical, and wherein R' is a hydrophobic group containing more than 5 carbon atoms which may be selected from the group consisting of alkyl, alkenyl, aralkyl or aralkenyl groups, the emulsion comprising:

a) 50 to 99.9% by weight water
b) .01 to 40 percent by weight of said cyclic dicarboxylic acid anhydride
c) .001 to 10.0 percent by weight of the water soluble cationic vinyl addition polymer.

The invention provides for utilization of certain specific cationic water soluble vinyl addition polymers having molecular weights of between 20,000 and 750,000 as additives and emulsifying agents for ASA sizes. Such cationic vinyl addition polymers serve as useful emulsifying agents for the ASA size and in addition increase the retention of the size upon the cellulosic sheet, without affecting the runnability of the paper machinery.
The ASA sizes to which this invention is applicable include those mentioned in U.S. patents 3,102,061, 4,040,900, 3,968,005, and 3,821,069.
The ASA sizes utilized in this invention are generally described by the structural formula shown above.
In a particular useful embodiment of this invention, a surfactant has also been employed in making the ASA sizes of this invention. This surfactant may be anionic, non-ionic, or cationic in nature. Surfactants employed are generally water soluble and have HLB values ranging from about 8 to about 30 or higher, and preferably from about 8-15. The surfactant is generally used to prepare the ASA size by simply mixing it with the raw ASA material. The ASA size used in this invention accordingly, and in a preferred embodiment of this invention, will generally contain 75-99.5 parts by weight of ASA and preferably 90-99 parts by weight of ASA with 0.5-25 parts, preferably .75-10 parts, and most preferably 1.0-5 parts by weight of surfactant.
The surfactants are preferably added to the ASA prior to emulsification in the aqueous medium. The surfactants can also be added to the aqueous medium prior to the addition of the ASA.
The surfactants useful in this invention are further described in U.S. patent 4,040,900 previously mentioned.
Classes of materials useful as surfactants include: ethoxylated alkyl phenols, such as nonyl phenoxy polyethoxy ethanols and octyl phenoxy polyethoxy ethanols; poly ethyleneglycols such as PEG 400 monooleate, and PEG 600 dilaurate; as well as other materials including certain ethoxylated phosphate esters.
Preferred surfactants for use are free acids of complex organic phosphate esters, commercial available as GAFAC^RRM510 and GAFAC^RRE610.

The water soluble polymers

The water soluble polymers used as cationic agents are water soluble vinyl addition homopolymers and copolymers having molecular weights of betweeen 20,000 and 750,000 where at least 10 weight percent and up to 100 weight percent of the mer content of the polymer is a cationic monomer, or cationically modified monomer selected from the indicated group. Preferably at least 15 and up to 95 weight percent of the mer units in the polymer is provided by the cationic or cationically modified monomers. Most preferably from 20-75 percent by weight of the mer units in the polymer or copolymer are cationic or cationically modified. These polymers are not ampholytic. Most preferably, the molecular weights of the polymers employed range from 50,000 to 150,000.
Polymers which can be employed in the practice of this invention include, but are not limited to the following exemplary copolymers and homopolymers:

acrylamide-dimethylaminoethylacrylate,
acrylamide-dimethylaminoethylacrylate quaternaries,
acrylamide-diethylaminoethylacrylate,
acrylamide-diethylaminoethylacrylate quaternaries,
acrylamide-dimethylaminoethylmethacrylate,
acrylamide-dimethylaminoethylmethacrylate quaternaries,
acrylamide-diallyldimethyl ammonium chloride,
polydiallyl-dimethyl ammonium chloride,
polydimethylaminoethylmethacrylate and its quaternaries,
polymethacrylamidopropyltrimethyl ammonium chloride and,
acrylamide-methacrylamidopropyltrimethyl ammonium chloride.

Also useful are polymers and copolymers of acrylamide which have been subjected to a "Mannich" reaction with formaldehyde and a lower alkyl secondary amine. These polymers may or may not be quaternized.
As seen, all of the polymers useful in this invention are cationically charged, non-ampholytic and water-soluble.
The polymers employed may be copolymers and even terpolymers of the various vinyl addition monomers. While acrylamide is a preferred nonionic monomer for use in preparing copolymers useful in this invention, other nonionic monomers such as methacrylamide can be employed.
Polymers as used in this invention may be in the form of water-in-oil emulsions (such as those described in U.S. Re. patent 28,474 and 28,576), dry powders, or dilute aqueous solutions. Preferably the polymers form an oil-in-water emulsion of the alkenyl succinic anhydride sizing material.
In order to employ the polymers in the emulsification of ASA sizes, an aqueous solution must first be prepared of the polymer. In the case of the water-in-oil emulsions of vinyl addition polymers, the water soluble surfactants used to invert the water-in-oil emulsions have no detrimental effect on the activity of the polymer used to emulsify the ASA size. When preparing a polymer solution from a water-in-oil emulsion polymer, a useful method or device for forming the solution is exemplified in U.S. patent 4,057,223 which dicloses a mixing block.
Depending upon the molecular weight and cationic charge of the polymer, from 0.01 % to 25 %, and preferably .01-10 % by weight of the final size emulsion to be added to the pulp furnish may be polymer.
The ASA emulsions fed to the pulp slurry accordingly to this invention will generally contain:

50 - 99.9 % by weight water
.01 - 50 % by weight ASA
.001 - 25.0 % by weight (preferably .005 - 3,0 %) of the water soluble polymer

Preferably, these emulsions will contain:

60 - 99,9 % water
.01 - 40 % ASA
.010 - 10 % polymer

Most preferably the ASA emulsion contain .01 - 5.0 and generally .01 - 1.0 parts by weight of the polymer and even more preferable, .05 - .9 parts polymer for each part of ASA in the emulsion.
Most preferably the ASA emulsion contains .01 - 7.5 and generally .01 - 5.0 parts by weight of the polymer.
The polymers may be used to emulsify the ASA, or may be added to previously formed ASA emulsions. In either case, the polymer will increase the performance of the emulsion compared to emulsions not containing the polymer. When the polymer is added to an ASA emulsion that has already been formed, conventional emulsifying agents should be used in addition to the polymer. When added or used during the makeup of the ASA emulsion, no additional emulsifier need be employed.
In order to test the subject invention, the following experiments were conducted. The polymers listed below were obtained commercially or prepared in the form indicated.

EXAMPLE 1

Solution acrylamide copolymers of types DMAEM-MeCI Quat, MAPTAC, and polyDADMAC of molecular weights ranging from 10,000 to 400,000 were evaluated as ASA emulsification and retention aids. These novel sizing compositions were compared in terms of ASA particle size, physical emulsion stability and sizing performance to conventional ASA emulsions in water or cationic starch. Description of these polymers are given in Table I.
ASA emulsions in water were prepared by combining 95 parts of distilled water and 5 parts of ASA in an Eberbach semi-microemulsion cup. The mixture was dispersed for 3 minutes at high speed. The emulsion formed was diluted with distilled water to 0.50 percent ASA solids basis and used in Example 1. ASA emulsions in cationic starch were prepared by first hydrating 5 parts of a pregelatinized cationic potato starch in 95 parts of water and agitating for 30 minutes. Size emulsions were then prepared by combining 75 parts of the starch solution with 25 parts of ASA in the emulsion cup and dispersing for 20 seconds. This emulsion was diluted to 0.50 percent ASA solids basis and used in Example 2. Lastly, ASA emulsions in vinyl addition polymers were prepared by dispersing ASA in polymer solutions at a ratio of 5:1 dry solids basis. These emulsions were diluted to 0.50 percent ASA solids basis by the method described above. Examples 3-8 illustrate the novel use of these addition polymers.
The ASA emulsions were tested separately in a paper slurry of composition 50 percent recycled corrugated boxboard, 50 percent recycled newsprint. Other slurry parameters were 0.5 percent consistency, 400 Canadian Standard Freeness, pH 7.5, and 25 degrees Celsius to which was added 12.5 parts per million of hydrated aluminum sulfate. Handsheets of basis weight 22,7kg (50 pounds) per 306,9m² (3300 square feet) were prepared in accordance with TAPPI T-205 procedures. The sizing compositions listed above were added to the paper slurry shortly before wet-web formation at dosages of 0.10 and 0.15 percent on paper solids. Handsheets were immediately dried on rotary drum to 98 percent solids basis. Results are shown on Table I.

EXAMPLE 2

Vinyl addition polymers, such as copolymers of acrylamide with DMAEM-MeCI quat or MAPTAC, and polyDADMAC, were further evaluated as ASA emulsification and retention aids. These novel sizing compositions were compared in terms of ASA emulsion particle size, physical emulsion stability with aging, and sizing performance to conventional ASA emulsions in water or cationic starch. The molecular weight of these polymers ranged from 10,000 to 400,000. A description of these polymers is shown in Table II.
ASA emulsions in water were prepared by combining 95 parts of distilled water and 5 parts of ASA in a laboratory 8 ounce Osterizer cup. The mixture was dispersed at high speed for 3 minutes. The emulsion formed was diluted with distilled water to 0.50 percent ASA solids basis and used in Example 9. ASA emulsions in cationic starch solutions were prepared by first hydrating 5 parts of a pregelatinized cationic potato starch in 95 parts of water and agitating for 30 minutes. Size emulsions were then prepared by combining 95 parts of the starch solution with 5 parts of ASA in the Osterizer cup and dispersing the size for 25 seconds. This emulsion was diluted to 0.50 percent ASA solids basis and used in Example 10. ASA emulsions in vinyl addition polymers were prepared by dispersing ASA in the polymer solutions at a ratio of 1:1 ASA to polymer solids in the Osterizer cup for 5 to 30 seconds.
These emulsions are then diluted to 0.50 percent ASA solids as described above. Examples 11-16 illustrate the novel use of these vinyl addition polymers.
Each ASA emulsion was tested separately in a paper slurry of composition 50 percent bleached softwood kraft and 50 percent bleached hardwood kraft pulps. The other slurry parameters were 0.5 percent consistency, 330 Canadian Standard Freeness, pH 7.3, and 27 degrees Celsius. Handsheets of basis weight 22,7kg (50 pounds) per 306,9m² (3300 square feet) were prepared in accordance with TAPPI T-205 procedures. The sizing compositions listed below were added to the paper slurry shortly before wet web formation at the dosage of 0.20 percent ASA solids on paper solids. Handsheets were immediately pressed to approximately 50 percent residual moisture and dried on a rotary drum dryer to 98 percent paper solids basis. Results are shown in the attached Table II.

EXAMPLE 3

The following comparative examples further illustrate the use of acrylamide copolymers of type DMAEM-MeSQ, DMAEA-MeSQ, DEAEA-MeSQ and DADMAC of molecular weights greater than 1,000,000 as emulsifiers and retention aids for alkenyl succinic anhydride sizing compositions, and conventional emulsions prepared from cationic starch.
For comparison, ASA emulsions in water were prepared by combining 95 parts of distilled water and 5 part of ASA in an Eberbach semi-microemulsion cup and dispersing the size for 60 seconds. The resulting emulsion was diluted to 0.50 percent ASA solids basis with water and used in Example 17. The ASA emulsions in cationic starch were prepared by first hydrating three parts of a pregelatinized cationic potato starch in 97 parts agitated cold water for 30 minutes. Emulsions were then prepared at two ASA to starch solid ratios of 10:1 and 3:1 by dispersing 30 parts of ASA in 70 parts of 3 percent cationic starch or 9 parts of ASA in 91 parts of 3 percent cationic starch respectively with the aid of the semi-microemulsion cup. The resulting emulsions were diluted to 0.5 percent ASA solids basis with water and used in Examples 17 and 18 accordingly.
Polymer solutions were prepared by hydrating 0.6 parts (as polymer solids) of those copolymers of acrylamide listed below in 99.4 parts of water respectively, allowing sufficient time and mixing for complete hydration. Emulsions were than prepared at two ASA to polymer solids ratios of 10:1 and 3:1 by dispersing 6 parts of ASA in 94 parts of 0.6 percent polymer solids solution or 1.8 parts of ASA in 98.2 parts of 0.6 percent polymer solids solution respectively with the aid of the semi-microemulsion cup.
A further dilution to 0.5 percent ASA solids was then taken. The following examples illustrate the advantages offered by this invention: the ability of these cationic water soluble acrylamide copolymers to initiate an ASA emulsion and to render the ASA emulsion particles cellulose substantive.
Each of the below cited ASA emulsions were separately added to a 0.5 percent consistency pulp slurry of composition 40 percent bleached hardwood sulfate pulp, 40 percent bleached softwood sulfate pulp, and 20 percent calcium carbonate of 300 Canadian Standard Freeness [pH 8.2). Handsheets of basis weight 22,7kg (50 pounds) per 306,9m² (3300 square feet) were prepared in accordance with TAPPI T-205 procedures. Emulsions of ASA were added to the pulp slurry shortly before wet-web formation at dosages of 0.250 and 2.00 percent on dry pulp solids. Handsheets were immediately dried on a rotary drum dryer to 98 percent solids basis (2 percent residual moisture). Results are shown in Table III.
This example clearly illustrates the novel use of cationic vinyl addition copolymers as ASA emulsification aids and retention aids. Improved water resistance is realized over conventional ASA in water or cationic starch emulsions. Secondly, the improved water resistance offered by this invention cannot be attributed simply to improved papermachine retention as demonstrated by separate additions of these same cationic polymers to the paper furnish.
The use of polymers in the high molecular weight range, however, can lead to the formation of tacky deposits and unstable emulsions. Further research as exemplified herein has shown that polymers having a molecular weight greater than 10,000 but lower than 1,000,000, and preferably from 20,000 to 750,000, performed essentially equivalent to polymers having higher molecular weight. In addition, the use of polymers having molecular weights in the preferred range of from 50,000 - 150,000 led to the elimination of the deposit formation noted above, and increased the stability of the ASA emulsions so prepared.

EXAMPLE 4

The effect of various other polymers on the emulsification of ASA sizing materials and the results obtained using such polymers were investigated. In this group of experiments, 3 different classes of polymers were employed (see below). All of these materials were prepared as water-in-oil emulsions of the polymer. Aqueous solutions of the polymers were prepared to yield an approximate 2% product basis or approximately .6% by weight aqueous polymer solution. The polymer solution was prepared by mixing together 288 grams of deionized water, 6.0 mls. of a 2% by weight aqueous solution of an ethoxylated (9) nonyl phenol surfactant followed by adding approximately 6 cc of the water-in-oil emulsion to the stirred mixture. The aqueous solutions were then adjusted to yield 2% by weight polymer product.
The ASA chosen for this and all subsequent studies is a substituted (alkenyl) cyclic dicarboxylic acid anhydride wherein the alkenyl groups are derived from a mixture of 14-22 carbon atoms.
The ASA size measure used in these tests was prepared by mixing 196 gms. of the polymer solution with 4.0 gms. of a commercial paper grade alkenyl succinic anhydride size available from Chevron Chemical Company, containing 1.0% by weight of Gafac@ RM-510 surfactant available from GAF Corporation. The resultant mixture was then emulsified by mixing for 30 seconds in an Eberbach semi-microemulsion cup followed by a final dilution of 0.5% ASA solids. The ASA emulsions were added to a commercial, calcium carbonate filled bleached Kraft furnish dosed at 0.25 % on dry pulp solids.
The neutral ink penetration test describes the paper's resistance to aqueous fluid penetration and is a measurement of time (in seconds) for ink to penetrate paper to a predetermined degree (80 percent reflectance endpoint). The greater the time, the greater the paper's resistance to ink penetration. Those skilled in the art will readily recognize this test as the generally practiced Hercules'Size Penetration Test. Results are found in Table IV.

EXAMPLE 5

The following examples further illustrate the novel use of acrylamide copolymers of type DMAEM-MeSQ and DADMAC as emulsifiers and retention aids for alkenyl succinic anhydride sizing compositions. The ASA emulsions thus formed were compared in terms of particle size and sizing performance with respect to ASA water emulsions and conventional emulsions prepared from cationic starch.
For comparison, ASA emulsions in water were prepared by combining 95 parts of distilled water and 5 parts of ASA in an Eberbach semi-microemulsion cup and dispersing the size for 60 seconds. The resulting emulsion was diluted to 0.50 percent ASA solids basis with water and used for the two sets. The ASA emulsions in cationic starch were prepared by first hydrating three parts of a pregelatinized cationic potato starch in 97 parts agitated cold water for 30 minutes. Emulsions were then prepared at two ASA to starch solid ratios of 10:1 and 1:1 by dispersing 30 parts of ASA in 70 parts of 3 percent cationic starch or 3 parts of ASA in 97 parts of 3 percent cationic starch respectively with the aid of the semi-microemulsion cup. The resulting emulsions were diluted to 0.5 percent ASA solids basis with water and used accordingly.
Polymer solutions were prepared by hydrating 0.6 parts (as polymers) of those copolymers of acrylamide listed below in 99.4 parts of water respectively, allowing sufficient time and mixing for complete hydration. Emulsions of ASA in polymer were then prepared by dispersing 6 parts of ASA in 94 parts of 0.6 percent polymer for 60 seconds with the aid of the semi-microemulsion cup. A further dilution to 0.5 percent ASA solids was then taken. Also this example illustrates the advantages offered by this invention: the ability of these cationic water soluble acrylamide copolymers to initiate and maintain a stable ASA emulsion and to render the ASA emulsion particles cellulose substantive. Polymers tested include the following:
Each of the below cited ASA emulsions were separately added to a 0.5 percent consistency pulp slurry of compostion 40 percent bleached hardwood sulfate pulp, 40 percent bleached softwood sulfate pulp, and 20 percent calcium carbonate of 300 Canadian Standard Freeness (pH 8.2). Handsheets of basis weight 22.7kg (50 pounds) per 306.9m² (3300 square feet) were prepared in accordance with TAPPI T-205 procedures. Emulsions of ASA were added to the pulp slurry shortly before wet-web formation at dosages ranging from 0.125 to 2.00 percent. Handsheets were immediately dried on a rotary drum dryer to 98 percent solids basis (2 percent residual moisture). In another variation of this procedure, 0.025 percent of a polymer was added to the pulp slurry separately after addition of sizing emulsions. Results are shown in Table V.
This example clearly illustrates the novel use of cationic vinyl addition copolymers as ASA emulsification aids and emulsion retention aids. Improved water resistance is realized over conventional ASA in water or cationic starch emulsions. Secondly, the improved water resistance offered by this invention cannot be attributed simply to improved paper-machine retention as demonstrated by separate additions of these same cationic polymers to the paper furnish.

Claims

1. A method for preparing an emulsified sizing agent useful in the preparation of sized paper products, such emulsion containing water, a cyclic dicarbocylic acid anhydride having the formula:

wherein R represents a dimethylene or trimethylene radical, and wherein ? is a hydrophobic group containing more than 5 carbon atoms which may be selected from the group consisting of alkyl, alkenyl, aralkyl or aralkenyl groups, and
a water soluble cationic vinyl addition polymer, characterized in that the cationic vinyl addition polymer has a molecular weight of between 20.000 and 750.000 and is made of at least 10 weight-% and up to 100 weight-% of the mer content of the polymer from one or more cationic or cationically modified vinyl addition monomers selected from the group consisting of

a) diallyldimethyl ammonium chloride;

b) methacrylamidopropyltrimethyl ammonium chloride;

c) dimethylaminoethylmethacrylate;

d) dimethylaminoethylmethacrylate quaternaries;

e) dimethylaminoethylacrylate;

f) dimethylaminoethylacrylate quaternaries;

g) diethylaminoethylacrylate;

h) diethylaminoethylacrylate quaternaries;

i) acrylamide reacted with formaldehyde and a lower secondary amine through the Mannich reaction; and

j) manniched acrylamide quaternaries.

2. The method according to claim 1, wherein the polymer is present in the alkenyl succinic anhydride size emulsion at a level of from 0,01 - 10,0 percent by weight polymer solids.

3. The method according to claim 2, wherein the polymer is present in the alkenyl succinic anhydride size emulsion at a level of from 0,01 - 5,0 percent by weight polymer solids.

4. The method according to one of claims 1 to 3, wherein the polymer is added to the alkenyl succinic anhydride size emulsion so as to provide from 0,05 - 0,9 part by weight polymer for each part of alkenyl succinic anhydride present in such emulsion.

5. A method for the sizing of paper, wherein an emulsion of a cyclic dicarboxylic acid anhydride having the formula:

wherein R represents a dimethylene or trimethylene radical and wherein R¹ is a hydrophobic group containing more than 5 carbon atoms which may be selected from the group consisting of alkyl, alkenyl, aralkyl or aralkenyl groups,
is applied to the paper stock, said cyclic dicarboxylic acid anhydride being emulsified by a water soluble cationic vinyl addition polymer, which has a molecular weight of between 20.000 and 750.000 and is made of at least 10 weight-% and up to 100 weight-% of the mer content of the polymer from one or more cationic or cationcally modified vinyl addition monomers selected from the group consisting of:

a) diallyldimethyl ammonium chloride;

b) methacrylaminodpropyltrimethyl ammonium chloride;

c) dimethylaminoethylmethacrylate;

d) dimethylaminoethylmethacrylate quaternaries;

e) dimethylaminoethylacrylate;

f) dimethylaminoethylacrylate quaternaries;

g) diethylaminoethylacrylate;

h) diethylaminoethylacrylate quaternaries;

j) manniched acrylamide quaternaries.

6. The method of claim 5, wherein the emulsion containing the water soluble polymer is added to the paper stock.

7. Am emulsion of a cyclic dicarboxylic acid anhydride having the formula:

wherein R represents a dimethylene or trimethylene radical and wherein R¹ is a hydrophobic group containing more than 5 carbon atoms which may be selected from the group consisting of alkyl, alkenyl, aralkyl or aralkenyl groups in water, the emulsion comprising:

a) 50 to 99,9 % by weight water

b) 0,01 to 40 % by weight of said cyclic dicarboxylic acid anhydride

c) 0,001 to 10,0 % by weight of a water soluble cationic vinyl addition polymer having a molecular weight of between 20.000 and 750.000 and being made of at least 10 weight-% and up to 100 weight-% of the mer content of the polymer from one or more cationic or cationically modified vinyl addition monomers selected from the group consisting of:

a) diallyldimethyl ammonium chloride;

b) methacrylamidopropyltrimethyl ammonium chloride;

c) dimethylaminoethylmethacrylate;

d) dimethylaminoethylmethacrylate quaternaries;

e) dimethylaminoethylacrylate;

f) dimethylaminoethylacrylate quaternaries;

g) diethylaminoethylacrylate;

h) diethylaminoethylacrylate quaternaries;

j) manniched acrylamide quaternaries.