JP2816845B2 - Surface sizing composition for papermaking and surface sizing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surface sizing composition for papermaking and a surface sizing method, and more particularly, to a high-concentration and storage stability, mechanical stability, heat and The present invention relates to a ketene dimer-based surface sizing composition for papermaking having excellent mechanical stability, low foaming properties of a coating solution, and excellent sizing effect, and a surface sizing method using the same.

2. Description of the Related Art Conventionally, sizing has been performed in ordinary paper and paperboard papermaking methods in order to provide these papers with functions such as size, waterproofness, and water resistance. The sizing method includes a so-called internal sizing method in which an internal sizing agent is added to a stock before forming a paper layer in a paper or paperboard manufacturing process, and a surface sizing agent is applied to the paper surface after forming a paper layer. Alternatively, there is a so-called surface sizing method for impregnation.

In recent years, in the papermaking industry, closed use of papermaking water has been advanced due to problems such as restrictions on the intake of industrial water and restrictions on the total amount of wastewater. This closed papermaking water deteriorates the quality of the water and further raises the water temperature.

In such a situation, the internal sizing method is disadvantageous in that it is easily affected by the water quality and temperature of the paper making water and cannot exert a sufficient size effect as the water use is closed.

On the other hand, the surface sizing method is not easily affected not only by the quality and temperature of the papermaking water but also by the papermaking pH,
There is an advantage that the yield of chemicals is high and the process control is easy.

As surface sizing agents, starch derivatives such as oxidized starch and phosphated starch, and anionic water-soluble polymer substances such as carboxymethylcellulose, polyvinyl alcohol, anionic acrylamide-based polymers and anionic styrene-based polymers are used. When these anionic water-soluble polymer substances are applied to acidic paper using a sulfate band, they react with aluminum ions of the sulfate band,
Hydrophobized to exhibit size. However, these neutral anionic water-soluble polymer substances do not exhibit sizing properties in neutral paper using no or only a small amount of the sulfate band.

As a commercially available neutral surface sizing agent, an aqueous dispersion of a ketene dimer compound is known as a surface sizing agent that exhibits excellent sizing properties not only on neutral paper but also on acidic paper.

Problems to be Solved by the Invention Conventionally, ketene dimer compounds are commercially available and used as an aqueous dispersion in which an aqueous continuous phase containing starch, particularly a cationized starch, is dispersed. However, ketene dimer-based compounds inherently easily react with water, and it is difficult to obtain a stable aqueous dispersion. For example, during storage, the dispersion loses uniformity and gels or precipitates. Further, there is a problem that effects such as size and waterproofness are reduced. In particular, it is more difficult to obtain an aqueous dispersion having a high concentration and excellent storage stability and mechanical stability.

In particular, in the surface sizing method, the medicine is mixed under heating to form a coating liquid, and since this coating liquid is used in circulation,
Since thermal and mechanical shocks are applied to the coating liquid, the surface sizing agent is required to have stability against these shocks.
Further, when the coating liquid is used in circulation, it is necessary that the foaming of the coating liquid is low.

In addition, the surface sizing method may include, in addition to imparting sizing to the paper, imparting functions such as surface strength and printability to the paper. The anionic water-soluble polymer substance is used to provide these functions. The surface sizing agent also needs to have good compatibility with the anionic water-soluble polymer substance.

In order to stabilize an aqueous dispersion of a ketene dimer compound, JP-A-60-258244 discloses a method of dispersing a ketene dimer compound in an aqueous continuous phase containing an acrylamide polymer having a cationic group. However, the surface sizing agent obtained by this method has a problem in compatibility with the anionic water-soluble polymer substance.

An object of the present invention is to provide a ketene dimer-based surface sizing composition for papermaking at a high concentration and improved storage stability, mechanical stability and sizing effect, and further excellent compatibility with anionic water-soluble polymer substances. An object of the present invention is to provide a surface sizing composition for papermaking and a surface sizing method using the same.

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems. As a result, (a) a ketene dimer compound represented by the following general formula (I): (In the formula, R ₁ and R ₂ represent the same or different hydrocarbon groups having 8 to 30 carbon atoms.) (B) A vinyl monomer is polymerized or copolymerized in the presence of an alkyl mercaptan having 6 to 22 carbon atoms. (B) based on 100 parts by weight of the compound of (a)
A surface sizing composition for papermaking, characterized by containing 2 to 100 parts by weight of a hydrophilic polymer of the formula (1), and a surface sizing method characterized by using the surface sizing composition for papermaking. In this case, it is preferable that the alkyl mercaptan having 6 to 22 carbon atoms in (b) is present in an amount of 0.01 to 10 mol% based on the vinyl monomer.
Further, it is preferable that the hydrophilic polymer composed of the vinyl monomer is a polymer of acrylamide, a copolymer of acrylamide and an anionic vinyl monomer, or a copolymer of acrylamide, an anionic vinyl monomer and a cationic vinyl monomer. . In particular, the hydrophilic polymer (b) is a hydrophilic polymer obtained by copolymerizing acrylamide, an anionic vinyl monomer and a cationic vinyl monomer, and the cationic polymer is added to one equivalent of the anionic group in the hydrophilic polymer. It is preferable that the number of the functional groups be 0.6 equivalent or less.

 Next, the present invention will be described in detail.

As the ketene dimer compound used in the present invention,
It is a compound represented by the general formula (I), and any of various known ketene dimer compounds can be used.

In the general formula (I), R ₁ and R ₂ represent the same or different hydrocarbon groups having 8 to 30 carbon atoms. Examples of the hydrocarbon groups include decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, and eicosyl. Alkyl groups such as tetradecenyl, hexadecenyl, octadecenyl, etc .; alkyl-substituted phenyl groups such as octylphenyl and nonylphenyl; alkyl-substituted cycloalkyl groups such as nonylcyclohexyl; and aralkyl groups such as phenylethyl. Of these, an alkyl group is preferred. These ketene dimer compounds may be used alone or in combination.
Used as a mixture of more than one species.

Further, the hydrophilic polymer (b) of the present invention has 6 carbon atoms.
Obtained by polymerizing or copolymerizing a vinyl monomer in the presence of an alkyl mercaptan having a carbon number of
The alkyl group of to 22 may be linear or branched,
The raw material for the alkyl group may be any of natural ones or artificially produced ones such as cracking of low-polymerized paraffins such as ethylene and propylene. For example, normal octyl mercaptan, normal dodecyl mercaptan, tertiary decyl mercaptan, hexadecyl mercaptan, octadecyl mercaptan and the like can be mentioned, and these can be used alone or as a mixture of two or more. Of these, normal octyl mercaptan and normal dodecyl mercaptan are preferred.

In (b) of the present invention, the alkyl mercaptan having 6 to 22 carbon atoms is preferably used in an amount of 0.01 to 10 mol%, most preferably 0.05 to 10 mol%, based on the vinyl monomer used for polymerization or copolymerization.
~ 2 mol% is used. When the amount of the alkyl mercaptan is less than 0.01 mol%, a stable surface sizing composition for papermaking cannot be obtained, and when the amount exceeds 10 mol%, it is introduced into the polymer at the time of polymerization or copolymerization reaction. The amount of unreacted alkyl mercaptan increases, which may foul equipment used for the polymerization reaction, adversely affect storage stability and sizing effect, and increase the cost of the papermaking surface sizing composition.

Examples of the vinyl monomer as a raw material of the hydrophilic polymer (b) of the present invention include, as a cationic vinyl monomer, (mono- or di-alkyl) amino (hydroxy) alkyl (meth) acrylate, (mono- or Di-alkyl) aminoalkyl (meth) acrylamide,
Vinylpyridine, vinylimidazole, diallylamine and the like can be used, and furthermore, salts of these inorganic or organic acids, quaternary ammonium salts and the like can be used. In addition, as the nonionic vinyl monomer, (meth) acrylamide, N, N-dimethylacrylamide, hydroxypropyl (meth) acrylate, or the like can be used. Further, as anionic vinyl monomers, monomers having a carboxylic acid such as (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, crotonic acid, vinyl sulfonic acid, (meth) allyl sulfonic acid,
-Acrylamide-2-methylpropanesulfonic acid, a monomer having a sulfonic acid group such as sulfonated styrene,
Alternatively, a monomer having a phosphate ester group such as a hydroxyalkyl (meth) acrylate phosphate ester can be used. As the hydrophobic vinyl monomer, styrene or a derivative thereof, alkyl (meth) acrylate, (meth)
Vinyl esters such as acrylonitrile, vinyl acetate and vinyl propionate, and methyl vinyl ether can be used. These monomers can be used alone or in appropriate combination of two or more kinds.

The surface sizing composition for papermaking, in addition to imparting sizing to the paper as described above, may also include imparting functions such as surface strength and printability to the paper, in order to impart these functions For example, oxidized starch, starch derivatives such as phosphorylated ester, carboxymethylcellulose, polyvinyl alcohol and anionic acrylamide-based polymer when anionic water-soluble polymer materials such as co-used with poor compatibility with these when used in combination. The following substances are preferred as the hydrophilic polymer (b) because the coating liquid may generate residue or the coating liquid may thicken to deteriorate operability and paper quality.

That is, a hydrophilic polymer obtained by polymerizing or copolymerizing acrylamide alone or acrylamide and an anionic vinyl monomer, more preferably a hydrophilic polymer obtained by copolymerizing acrylamide, a cationic vinyl monomer and an anionic vinyl monomer. Further, a hydrophilic polymer in which the cationic group is 0.6 equivalent or less per equivalent of the anionic group in these hydrophilic polymers is preferable. The surface sizing composition for paper making using such a hydrophilic polymer has excellent compatibility with the anionic water-soluble polymer.

In order to synthesize the hydrophilic polymer (b), a conventionally known method can be applied. For example, in the presence of an alkyl mercaptan having 6 to 22 carbon atoms, the vinyl monomer is polymerized by a radical polymerization catalyst in a lower alcohol such as methanol, ethanol or isopropyl alcohol, or in a mixed solution of these lower alcohols and water, It is obtained by distilling off the lower alcohol after completion of the polymerization. Examples of the radical polymerization catalyst include persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate, redox polymerization catalysts obtained by combining these persulfates and a reducing agent, and 2,2′-azobis- (2-amidinopropane). And azo catalysts such as dihydrochloride and 2,2'-azobisisobutyronitrile. Also,
If necessary, a known chain transfer agent may be appropriately used in combination.

The viscosity of the hydrophilic polymer solution (b) thus obtained is 10 to 5000 centipoise in a 20% by weight aqueous solution (however, measured at 25 ° C. at 60 rpm per minute by a Brookfield viscometer). The viscosity is preferably 50 to 1000 centipoise. When this viscosity is lower than 10 centipoise or higher than 5,000 centipoise, when this is used as the component (b) of the present invention, the storage stability and mechanical stability are those using the above viscosity range. In comparison, they tend to be inferior.

The hydrophilic polymer (b) is used in an amount of 2 to 100 parts by weight based on the ketene dimer compound represented by the general formula (I).
It is preferable to use parts by weight, preferably 5 to 50 parts by weight. 2
If it is less than 10 parts by weight, the emulsifiability is inferior, the storage stability of the paper-making surface sizing composition loses its mechanical stability, and if it exceeds 100 parts by weight, not only is it economically disadvantageous, but also Adversely affect.

In the present invention, further, a cationized starch having 6 carbon atoms is used.
Polymeric colloids such as cationic, anionic or amphoteric acrylamide-based polymers obtained by polymerization in the absence of alkyl mercaptans of from 22 to 22; anionic dispersions such as lignin sulfonate and naphthalene sulfonate-formaldehyde condensate A nonionic dispersant such as a dispersant or a sorbitan ester can also be used to the extent that the stability of the papermaking surface sizing composition is not impaired.

The paper-making surface sizing composition of the present invention can be produced by a conventionally known method. For example, the ketene dimer compound and the hydrophilic polymer of (b) and, if necessary, the protective colloid or dispersant may be mixed with an aqueous solvent at a temperature not lower than the melting point of the ketene dimer compound represented by the general formula (I). It is obtained by mixing into a well-known emulsifier such as a homomixer, a high-pressure discharge homogenizer, and an ultrasonic emulsifier.

The paper-making surface sizing composition of the present invention thus obtained has a particle size of the dispersed phase of 10 μm or less, and exhibits storage stability and mechanical stability at a solid content of 15 to 30% by weight. It is extremely excellent and can exhibit an excellent size effect. Further, the coating liquid containing the paper-making surface sizing composition has excellent heat and mechanical properties, and has the advantage of low foamability.

The excellent effect of the papermaking surface sizing composition of the present invention is:
When a vinyl monomer is polymerized or copolymerized in the presence of an alkyl mercaptan having 6 to 22 carbon atoms, the used alkyl mercaptan is introduced into the terminal of the obtained hydrophilic polymer, whereby the hydrophilicity of (b) is reduced. It is considered that the polymer acts as an excellent dispersant and protective colloid of the ketene dimer compound represented by the general formula (I).

The paper-making surface sizing composition of the present invention enables the ionicity of the hydrophilic polymer (b) to be appropriately selected and adjusted according to the type and amount of ionicity of other additives used in combination. I do.

The surface sizing method of the present invention is carried out by applying or impregnating the paper sizing composition of the present invention after forming a paper layer. Specifically, the papermaking sizing composition of the present invention is applied to a surface coating solution to be coated with a size press, a gate roll coater, a bill blade coater, a calender, or the like on a paper surface in an amount of 0.005 to 0.5 g / m ² ( (Dry weight), preferably 0.01 to 0.2 g / m ² . At this time, the papermaking surface sizing composition of the present invention may be used alone, but the anionic water-soluble polymer substance,
It can also be used by mixing with a surface treating agent such as a dye in the same coating solution.

The base paper used in this surface sizing method is not particularly limited to ordinary pulp raw material or paper produced from a pipe or the like using a filler as required, and even if an internal sizing agent is contained. You don't have to. Further, various internal additives such as dyes, dry paper strength improvers, wet paper strength improvers or retention aids may or may not be contained.

As the pulp raw material, bleached or unbleached high yield pulp such as bleached or unbleached chemical pulp such as kraft pulp or sulfite pulp, groundwood pulp, mechanical pulp or thermomechanical pulp, newspaper waste paper, magazine waste paper, cardboard waste paper or Any waste paper pulp such as deinked waste paper can be used.

Examples Hereinafter, examples of the present invention will be described, but the present invention is not limited to these. In the following, in Examples and Comparative Examples,% and parts mean weight% and solid parts by weight, respectively.

In addition, the amounts of fillers and chemicals are indicated by solid% by weight based on the dry pulp weight.

Example 1 In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube, 31.1 g of 2-acrylamide-2-methylpropanesulfonic acid, 50% of acrylamide
Aqueous solution 192.0 g, ion exchange water 190.0 g, isopropyl alcohol 222.4 g and normal dodecyl mercaptan 1.52 g
And adjusted to pH 4.0 with a 20% aqueous sodium hydroxide solution. While stirring this mixture, nitrogen gas was introduced to remove oxygen, and the temperature was raised to 60 ° C. At 60 ° C., 3.42 g of a 5% aqueous solution of ammonium persulfate was added to initiate polymerization.
Thereafter, the temperature was raised to 78 ° C., and after maintaining at 78 ° C. for 1.5 hours, 1.05 g of a 5% aqueous solution of ammonium persulfate was added. After maintaining the same temperature for 1 hour, 200 g of ion-exchanged water was added, and distillation of isopropyl alcohol was started. Two hours after the start of the distillation, 285.5 g of a mixed distillate of isopropyl alcohol and water was obtained, and the distillation was completed. 85.5 g of ion-exchanged water was added to the obtained polymerization product, and the nonvolatile content was 20.3%, 25
A polymer aqueous solution P-1 having a Brookfield viscosity (hereinafter, referred to as viscosity) of 220 centipoise (hereinafter, referred to as cps) and a pH of 4.3 measured at 60 ° C. and 60 rpm was obtained.

Next, 100 parts of a ketene dimer compound (based on a mixture of 40% of palmitic acid chloride and 60% of stearic acid chloride), 123 parts of the aqueous polymer solution P-1 obtained by the polymerization and 277 parts of ion-exchanged water were added to 70 parts of ° C
After pre-dispersion with a homomixer, while maintaining the same temperature, 250 Kg / cm ²
2 passes under a shear pressure of 1 to uniformly disperse. After appropriately adding ion-exchanged water and cooling, the mixture is filtered through a 325-mesh wire gauze, and is an aqueous dispersion of a paper-making surface sizing composition E.
-1 was obtained. The obtained paper sizing agent composition E-1
Had a nonvolatile content of 20.2%, a viscosity of 12.4 cps and a pH of 3.4.

Examples 2 to 8 Polymerization was carried out in the same manner as in Example 1 except that the type of mercaptan and the composition of the vinyl monomer were changed to those shown in Table 1, to obtain polymer aqueous solutions P-2 to P-8. The amount of isopropyl alcohol for adjusting the viscosity was appropriately changed each time. Next, the same operation as in Example 1 was performed except that the mixing ratio of the ketene dimer compound / the polymer was changed as shown in Table 2, and the paper-making surface sizing composition E-
2-E-8 were obtained.

Comparative Examples 1-3 Polymerization was carried out in the same manner as in Example 1 except that the type of mercaptan and the composition of the vinyl monomer were changed as shown in Table 1, to obtain polymer aqueous solutions RP-1 to RP-3. Next, the same operation as in Example 1 was performed except that the mixing ratio of the ketene dimer compound / the polymer was changed as shown in Table 2, to obtain paper-making surface sizing compositions RE-1 to RE-3. .

Table 2 summarizes the blending and physical properties of the paper-making surface sizing compositions E-1 to E-8 and RE-1 to RE-3 of Examples 1 to 8 and Comparative Examples 1 to 3.

 In addition, the symbol in Table 1 shows the following.

M-1; n-dodecyl mercaptan M-2; n-octyl mercaptan M-3; tert-dodecyl mercaptan M-4; n-hexadecyl mercaptan M-5; n-octadecyl mercaptan M-6; n-butyl mercaptan M -7; thiophenol A-1; 2-acrylamide-2-methylpropanesulfonic acid A-2; acrylic acid A-3; itaconic acid C-1; dimethylaminopropyl acrylamide C-2; dimethylaminopropyl methacrylamide The ketene dimer compound in the table is obtained by using a mixture of palmitic acid chloride 40% and stearic acid chloride 60% as a raw material.

Next, the storage stability and the mechanical stability of the paper-making surface sizing compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were measured under the following conditions, and the results are shown in Table 3.

(Storage stability test) The value of viscosity (measured at 25 ° C, Brookfield viscometer, 60 rpm) after storage at 32 ° C for one month is measured.

(Mechanical Stability Test) 50 g of the surface sizing composition for papermaking was applied to a Marlon method stability tester under a load of 20 kg / cm ² at a rotation speed of 1000 rpm.
This is the weight of the solid component that did not pass through a 100-mesh wire net when agitated for 0 minutes. However, the test starting temperature was 25 ° C.

The higher the solid content weight, the greater the amount of cake generated, indicating poorer mechanical stability.

In addition, the results of the tests of the thermal / mechanical stability and foamability of the mixed coating liquids of the paper-making surface sizing compositions and oxidized starch of Examples 1 to 8 and Comparative Examples 1 to 3 were performed by the following methods. Are shown in Table 3.

(Thermo-mechanical stability test of coating liquid) The surface sizing composition for papermaking was 5% solids and the oxidized starch (Oji Ace A, manufactured by Oji Cornstarch) was 5% solids.
The same test as in the mechanical stability test described above was conducted except that the mixed coating aqueous solution was 50 g. However, the test starting temperature was 50 ° C.

(Foamability of coating liquid) 200 ml of a mixed coating aqueous solution containing 0.2% of a solid content of a surface sizing composition for papermaking and 5% of a solid content of oxidized starch (Oji Ace A, manufactured by Oji Cornstarch) at 50 ° C. Adjust, place in a 6 cm diameter cylindrical cylinder with temperature preservation function and graduation, and blow in air at 40 / hr using an air pump. The height of the foam 1 minute and 10 minutes after the start of the blowing, and the presence or absence of the residue on the liquid surface when the blowing of the air was stopped after the start of the blowing 10 were visually determined.

Next, the mixed coating solution of the paper-making surface sizing composition and the oxidized starch obtained in Examples 1 to 8 and Comparative Examples 1 to 3 was applied to a neutral paper-made weak paper by a laboratory size press ( (Kumagaya Riki Kogyo Co., Ltd.) and the size effect was examined.
Table 4 shows the results.

 The test conditions are as follows.

(Base paper) Pulp: BKP L / N = 8/2 Internal additives: Heavy calcium carbonate Base paper ash content 16.7% Harcon W (Ketene dimer system internal sizing agent manufactured by Dick Hercules) 0.05% Cationized starch 0.75% Papermaking pH : 8.0 basis weight: 60 g / m ² (coated amount) papermaking surface size composition: (manufactured by Oji Ace A Oji cornstarch Co., Ltd.) solid 0.03 g / m ² of oxidized starch solid 1.00 g / m ² (size press Machine operation conditions) Press speed: 100m / min Nip pressure: 20Kg / cm Coating liquid temperature: 50 ° C (drying condition) Drum dryer 80 ° C, 50 seconds (size effect) Stokit sizing degree according to JIS P-8122 From the test results of the above-mentioned surface sizing composition for papermaking, all of the examples were excellent in storage stability, mechanical stability, heat / mechanical stability of the coating liquid, and foaming property of the coating liquid. It can be seen that the paper obtained by the surface sizing method using the paper-making surface sizing composition of these examples has an excellent size effect.

Effect of the Invention According to the present invention, a hydrophilic polymer obtained by polymerizing or copolymerizing a vinyl monomer in the presence of an alkyl mercaptan having 6 to 22 carbon atoms is used in combination with a ketene dimer compound. The storage stability, mechanical stability, and thermo-mechanical stability of the product can be improved, and the foaming property of a coating solution containing the paper sizing composition can be reduced. In addition, since the compatibility with the anionic water-soluble polymer substance can be increased, problems such as generation of lees during use thereof can be solved. Moreover, the surface sizing method using the papermaking sizing composition of the present invention can exhibit excellent sizing properties.

────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Mayumi Narishima 17-2 Yawata Kaigandori, Ichihara City, Chiba Prefecture Inside Dick Hercules Co., Ltd. (56) References JP-A-63-42995 (JP, A) 60-258245 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) D21H 19/10 D21H 19/20

Claims (5)

(57) [Claims] (1) a ketene dimer compound represented by the following general formula (I): (In the formula, R ₁ and R ₂ represent the same or different hydrocarbon groups having 8 to 30 carbon atoms.) (B) A vinyl monomer is polymerized or copolymerized in the presence of an alkyl mercaptan having 6 to 22 carbon atoms. A surface sizing composition for papermaking, comprising: a hydrophilic polymer of (a), and 2 to 100 parts by weight of the hydrophilic polymer of (b) based on 100 parts by weight of the compound of (a). 2. The papermaking surface size according to claim 1, wherein the alkyl mercaptan having 6 to 22 carbon atoms in (b) is present in an amount of 0.01 to 10 mol% based on the vinyl monomer. Composition. 3. The hydrophilic polymer (b) is a polymer of acrylamide, a copolymer of acrylamide and an anionic vinyl monomer, or a copolymer of acrylamide, an anionic vinyl monomer and a cationic vinyl monomer. The paper-making surface sizing composition according to claim 1 or 2, characterized in that: 4. The hydrophilic polymer (b) is a hydrophilic polymer obtained by copolymerizing acrylamide, an anionic vinyl monomer and a cationic vinyl monomer,
3. The papermaking surface sizing composition according to claim 1, wherein the cationic group is 0.6 equivalent or less per 1 equivalent of the anionic group in the hydrophilic polymer. 5. A surface sizing method, comprising using the papermaking surface sizing composition according to any one of claims 1 to 4.