KR20140132843A - Latex for coating paper and paper coating liquid composition - Google Patents

Abstract

The present invention relates to latex for coating paper and a paper coating solution composition. According to the present invention, provided are latex for coating paper having an excellent stability and flow property by controlling the composition of monomers used in manufacturing latex, and a paper coating solution composition including the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a latex and paper coating liquid composition for paper coating,

TECHNICAL FIELD The present invention relates to a latex and a paper coating composition for paper coating, and more specifically, to a latex for paper coating having excellent stability and flow characteristics by specifying the composition of monomers used in latex production, and a paper coating solution composition containing the same .

In general, the coated paper is produced by coating an inorganic pigment such as clay, calcium carbonate, aluminum hydroxide (Al (OH) ₃ ) or titanium oxide (TiO ₂ ) on paper with a natural binder such as casein, starch, And synthetic binders such as styrene-butadiene latex, polyvinyl alcohol, and acrylic latex are used as adhesives. In addition, various additives such as a dispersing agent, a thickener, and a water-proofing agent are used together. However, the largest proportion is also inorganic pigments and binders, which should be selected in the direction of obtaining a balanced coating material properties.

The most commonly used inorganic pigments are clay and calcium carbonate. The clay has a disadvantage of high flatness and print gloss as a plate-like structure, but has a disadvantage of low fluidity and a large amount of binder required. In the case of calcium carbonate, it has drawbacks such as fluidity, adhesion, ink repellency, paper brightness, opacity While the chemical stability of the coating solution for the calcium cation is more required.

Recently, the concentration of the solid content of the coating liquid has been increased for the purpose of improving the productivity and reducing the drying energy after coating. In this high concentration, the viscosity of the composition for paper coating becomes high, and the fluidity is deteriorated.

In addition, as the paper production speed gradually increases, there is also a move to increase the productivity and to cope with the supply of printed materials by increasing the coating speed. Recently, the coating speed has reached as high as 1000 ~ 1500 m / min. When the coating speed is increased, the shear force at coating becomes higher, so the high shear flowability becomes more important. In this case, 'high-shear' refers to shear rate of several thousand sec ^-1 or more. Low shear flow affects the transport and coating of the coating solution, where the term 'low shear' usually refers to a shear rate of several hundreds sec ^-1 or more.

As described above, the increase in the concentration of the coating liquid and the increase in the coating speed have a problem in that the low shear / high shear fluidity of the coating liquid must be determined. As a related countermeasure, there is a method of replacing a natural water-soluble binder such as starch or casein having a large viscosity action with an artificial binder and a method of increasing the use ratio of heavy calcium carbonate having fine fluidity on the pigment surface. In recent years, the use of calcium carbonate has gradually increased in place of clay. However, the advantages of such a method have been pointed out, and the physical properties of the coated surface such as white glossy, printing gloss and smoothness are lowered, Disadvantages, and the like.

In addition, there is a method of improving the low shear / high shear flowability of the coating liquid by using a latex having excellent fluidity, and in fact, the latex occupies a very large portion in the fluidity of the coating liquid. This method is the most realistic and safe method to improve the fluidity of the coating liquid, and a growing number of papers demanding a latex having an excellent fluidity.

Another problem in increasing the concentration of the coating solution and increasing the coating speed is securing the stability of the coating solution. For reference, in the conventional method of coating a coating composition, the coating liquid is transferred from an applicator-roll to a paper surface, and is removed by using a blade or an air-knife during over-coating, The mechanical stability of the coating liquid becomes very important. For reference, if the stability of the coating solution is destroyed under high pressure, the coating solution may gumming up at the edge of the applicator-roll, causing problems such as streak, fish-eyes or blade contamination It can lead to catastrophic loss.

The stability of these coating solutions is liable to be influenced by the latex, and the stability of the latex is maintained by the carboxyl group and the emulsifier. The carboxyl group can be obtained by using an ethylenically unsaturated carboxylic acid as a copolymerizable monomer. In particular, the carboxyl group can be fixed on the latex surface to improve stability, but generally the pH of the coating solution is 8 to 11, many.

The emulsifier may be an anionic emulsifier such as a sulfate or a sulfonate, or an ethylene oxide nonionic emulsifier. However, since the emulsion is adsorbed without being fixed to the latex, it is desorbed when mechanical shear force is applied, There is a drawback to this.

On the other hand, as a method for improving the adhesion of the latex, the latex is hardened. However, as the solid content of the latex is increased during the production, the viscosity of the latex rapidly increases during the polymerization, which may lower the fluidity. This can cause problems in the reactor heat during production and increase the non-uniformity of latex physical properties during continuous production. In addition, there is a fine coagulum on the suspension, which also tends to increase as the latex hardens. In this case, the time and cost of the screening process after the completion of the polymerization and the preparation of the coating liquid may be excessively consumed, which may result in difficulty in product management and cause serious problems such as streaks on the surface of the paper during coating, Can be reduced. Accordingly, the polymerization stability of the latex becomes very important as the latex hardens and the concentration of the solid increases, and securing the polymerization stability of the latex not only improves the quality through the hardening of the latex but also increases the productivity , The nonuniformity of physical properties during continuous production can be greatly reduced, which will greatly contribute to the improvement of the relative quality.

For reference, as an important printing suitability, an adhesive force (dry strength, dry pick resistance) due to tendency toward high-speed printing of offset printing can be mentioned. That is, it should exhibit a clear print appearance without peeling off of the pigment and peeling from the coating layer against the strong mechanical force against the pigment coated paper surface at the time of printing.

The physical properties of the latex for paper coating on the adhesive strength of coated paper are various such as glass transition temperature, particle size, gel content, and monomer composition.

The ink drying rate of the coating liquid may also be important. In the case of multicolor printing, generally, overprinting is performed by four colors such as blue, black, red, and yellow. As the printing speed is increased, the time interval until printing of the next color is shortened, . If the ink is not sufficiently dried and you move on to the next step, print mottle or back hiding may appear. The relationship between the gel content and the ink drying rate is expressed not only in the film forming ability difference according to the gel content but also in the swelling index difference which is the amount of the solvent that latex particles can contain.

In addition, there is a gloss with important physical property that can enhance the commercialization of the printing paper and to seek a high quality. The gloss can be divided into the white glossy of the coated paper and the print glossy after printing, both of which show a more elegant appearance.

Generally, in order to increase the gloss of white paper, a method of increasing the particle size of the latex or lowering the latex content in the coating liquid may be used, but in this case, the adhesive strength is lowered.

In order to increase the print gloss, it is necessary to lower the permeability to have a solvent on the surface until a stable arrangement is obtained after printing. In order to do this, the ink drying rate must be appropriately lowered.

The important printability in offset printing is water resistance. In offset printing, wetting water is used during printing. When water resistance (wet strength) is low, peeling of the pigment may occur due to strong physical force applied at the time of printing.

The relationship between water resistance and gel content also shows the strongest water resistance at any suitable gel content, as well as adhesion. However, in general, the gel content at which the adhesive strength becomes the maximum and the gel content at which the water resistance becomes the maximum are not coincident with each other.

Another printing property required in offset printing is ink fountain property. As described above, in the offset printing, since the wetting water is used, if the coated paper does not effectively absorb water, ink which is not compatible with water is not likely to be adhered to the coated paper, resulting in lower printing degree. In general, the ink-fusing property and the water-resistance are in a relationship of opposite properties, and it is difficult to increase them at the same time.

As such, it is very difficult to produce latex that can provide excellent coated paper for each printing aptitude, and coating and printing conditions are becoming more difficult. In addition, in order to obtain excellent physical properties, the monomer composition, gel content, and particle size must be adjusted to severe conditions, so that the stability of the polymerization is greatly deteriorated. Also, it is very difficult to improve the physical properties at the same time, and there is a limit to the composition of the existing monomers.

It is an object of the present invention to provide a paper coating latex having excellent stability and flow characteristics by applying a specific composition of a monomer used in emulsion polymerization and a paper coating liquid composition containing the same.

The present invention provides a latex for paper coating obtained by emulsion-polymerizing a mixture of a styrene-based monomer, an acrylate-based monomer, an ethylenically unsaturated acid monomer, a crosslinking monomer, and an unsaturated alkyl derivative having a sulfonic acid group.

The present invention also provides a paper coating liquid composition comprising an inorganic pigment, a natural binder and a synthetic binder, wherein the latex for paper coating is used as the synthetic binder.

The present invention also provides a paper obtained by calendering the above-mentioned paper coating liquid composition.

Hereinafter, the present invention will be described in detail.

First, the latex for paper coating according to the present invention is characterized by being obtained by emulsion polymerization of a mixture of a styrenic monomer, an acrylate monomer, an ethylenically unsaturated acid monomer, a crosslinking monomer and an unsaturated alkyl derivative having a sulfonic acid group.

According to the monomer composition, a latex having excellent stability and excellent printing properties can be provided.

As another example, the latex may include one to three layers of the shell obtained by emulsion-polymerizing the mixture under an emulsifier, a pH adjuster and a polymerization initiator.

The mixture contains 15 to 80 parts by weight of a styrene monomer, 20 to 80 parts by weight of an acrylate monomer, 1 to 10 parts by weight of an ethylenically unsaturated acid monomer, 1 to 10 parts by weight of a crosslinking monomer, And 0.1 to 5 parts by weight of an unsaturated alkyl derivative having a group (s).

For example, in the present invention, the unsaturated alkyl derivative having a sulfonic acid group has an effect on the interfacial energy of the latex, thereby improving the surface properties. Thus, the ink drying speed, water resistance, Can play a role.

Further, the emulsifier may be added during the polymerization reaction or after the reaction to impart stability to the latex, and various kinds of anionic emulsifiers and nonionic emulsifiers may be used. Examples of the anionic emulsifier include alkylbenzenesulfonates, alcohol sulfates, alcohol ether sulfonates, alkylphenol ether sulfonates, alpha olefin sulfonates, paraffin sulfonates, ester sulfosuccinates, phosphate esters, Examples of the emulsifying agent include alkylphenol ethoxylate, petianamine epoxylate, fatty acid ethoxylate, and alkanoamide.

In the present invention, the unsaturated alkyl derivative having a sulfonic acid group can be used by controlling and mixing the emulsifiers with the above-mentioned emulsifiers. As a specific example, the unsaturated alkyl derivative having a sulfonic acid group and the emulsifier may be 0.1 to 2 parts by weight, or 0.5 to 2 parts by weight based on 100 parts by weight of the mixture.

Within the above range, physical properties such as polymerization stability and printing properties can be excellent.

The unsaturated alkyl derivative having a sulfonic acid group may be, for example, an alkyl group having a sulfonic acid group and containing a carbon-carbon double bond, a carbon number of 2 to 20, or a derivative having a carbon number of 3 to 10.

In another example, the unsaturated alkyl derivative having a sulfonic acid group may be an alkali metal salt or an alkaline earth metal salt.

As another example, the unsaturated alkylsulfonic acid metal salt may be sodium methallylsulfonate, sodium metalylsulfonate, sodium vinylsulfonate Or more.

The crosslinking monomer may be used in an amount of 0.1 to 5 parts by weight, or 0.5 to 3 parts by weight based on 100 parts by weight of the mixture.

The crosslinking monomer may improve the stability of latex particles and improve the strength and adhesion of the copolymer. For example, allyl acrylate, allyl methacrylate, glycidyl acrylate, glycidyl methacrylate Propyleneglycol diacrylate, tripropylene glycol diacrylate, ethylene glycol diacrylate, neopentyl glycol diacrylate, trimethylene propyl acrylate, trimethylol propyl acrylate, Triacrylate, propoxylated glycerol triacrylate; And a silane coupling agent represented by the formula R-Si≡ (X) ₃ or R-Si≡ (R ') (X) ₃ wherein R is a vinyl, epoxy, or a free radical having a substituted or unsubstituted amino or mercapto group , R 'is an alkyl group having 4 or less carbon atoms, and X is methoxy, ethoxy or chlorine.

The mixture may further include at least one copolymerizable vinyl monomer selected from an unsaturated carboxylic acid alkyl ester, an unsaturated carboxylic acid hydroxyalkyl ester, a carboxylic acid amide, a carboxylic acid amide derivative and an aromatic vinyl monomer.

The styrenic monomer may serve to impart a suitable hardness to the copolymer. For example, the styrenic monomer may be at least one selected from styrene,? -Methylstyrene,? -Ethylstyrene, p-methylstyrene and vinyltoluene.

The specific amount may be 15 to 80 parts by weight, 17 to 78 parts by weight, 20 to 55 parts by weight, 20 to 44 parts by weight or 22 to 35 parts by weight. In this range, the adhesive force and the film forming ability can be improved.

The acrylate-based monomer may serve to impart flexibility to the copolymer. For example, the acrylate monomer may be an acrylate having an alkyl group having 1 to 20 carbon atoms. Specific examples thereof include acrylates having an alkyl group having 1 to 6 carbon atoms Lt; / RTI >

The acrylate monomer may be used in an amount of 20 to 80 parts by weight, 30 to 70 parts by weight or 40 to 60 parts by weight. Within this range, the copolymer can be prevented from being too hard or too sticky, and the printing gloss and adhesion can be improved.

The ethylenic unsaturated acid monomer may serve to improve the adhesion of the copolymer and improve the stability of the latex particles. Specific examples thereof include unsaturated carboxylates such as methacrylic acid, acrylic acid, itaconic acid, crotonic acid, fumaric acid, Unsaturated polycarboxylic acid alkyl esters having at least one carboxyl group such as acid and itaconic acid monoethyl ester, fumaric acid monobutyl ester or maleic acid monobutyl ester, and the like.

The specific amount may be 1 to 10 parts by weight or 1 to 5 parts by weight. Within the above range, polymerization stability and the like may be appropriate.

Further, it may further comprise at least one vinyl cyanide monomer selected from acrylonitrile, methacrylonitrile and etaacrylonitrile to improve printing gloss. The specific amount may be 0.01 to 10 parts by weight or 1 to 5 parts by weight.

Further, it may further comprise a mercaptan-based molecular weight modifier such as n-dodecyl mercaptan or t-dodecyl mercaptan to control the molecular weight, gel content and gel structure of the copolymer. The specific content may be 0.01 to 3 parts by weight, or 0.05 to 1 part by weight.

If necessary, a monomer capable of copolymerizing with the above monomers may be used. Specific examples include unsaturated carboxylic acid alkyl esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl methacrylate and the like; unsaturated carboxylic acid hydroxyalkyl esters such as? -hydroxyethyl acrylate,? -hydroxypropyl acrylate and? -hydroxyethyl methacrylate; Carboxylic acid amides and derivatives thereof such as acrylamide, methacrylamide, itaconamide, maleamic acid amoamide and the like; and aromatic vinyl monomers such as? -methylstyrene, vinyltoluene, p-methylstyrene, and the like.

In this case, the unsaturated carboxylic acid alkyl ester can play a role of imparting appropriate hardness to the copolymer and improving film forming ability. The specific amount may be 1 to 10 parts by weight, or 1 to 5 parts by weight.

On the other hand, the unsaturated carboxylic acid amide and its derivatives can improve the chemical stability, mechanical stability and water resistance of the copolymer latex, and the specific amount of the unsaturated carboxylic acid amide and the derivative thereof may be 1 to 10 parts by weight or 1 to 5 parts by weight.

The latex can be produced in one step or two or more stages, and can be polymerized by coating seeds with latex and then coating one to three layers of shells. Other reaction conditions such as a polymerization initiator, a pH adjuster, and an electrolyte which are not specifically shown are the same as those of emulsion polymerization.

As a specific example, the latex is obtained by emulsion-polymerizing a styrene-based monomer, an acrylate-based monomer, an ethylenically unsaturated acid monomer, a vinyl cyanide-based monomer, and a crosslinked monomer in an emulsion, a pH adjuster, Seeds. ≪ / RTI >

Specifically, the styrene-based monomer, the acrylate-based monomer, the ethylenically unsaturated acid monomer, the vinyl-based monomer, and the crosslinking monomer are contained in an amount of 60 to 85 parts by weight based on 100 parts by weight of the styrene-based monomer, To 15 parts by weight, 1 to 10 parts by weight of an ethylenic unsaturated acid monomer, and 0.1 to 5 parts by weight of a crosslinking monomer.

As another example, the styrene-based monomer, the acrylate-based monomer, the ethylenically unsaturated acid monomer, the vinyl-based monomer, and the crosslinking monomer may be used in an amount of 70 to 80 parts by weight based on 100 parts by weight of the sum of the styrenic monomer, 2 to 7 parts by weight of an ethylenic unsaturated acid monomer, 10 parts by weight or less of a vinyl cyanide monomer, and 0.5 to 3 parts by weight of a crosslinking monomer.

As another example, it is possible to use at least 90 wt% of the styrene-based monomer and not use the acrylic monomer, or 20 wt% or less of the styrene-based monomer.

The seed may be used in an amount of 5 to 20 parts by weight, or 8 to 15 parts by weight, based on the solid content.

The glass transition temperature of the latex according to the present invention should be about -30 to 70 ° C, -30 to 50 ° C, or -20 to 40 ° C, for example.

The particle size of the latex should be about 50 to 300 nm, 70 to 250 nm, or 80 to 200 nm, for example. If the particle diameter is less than 50 nm, the low shear flow property is increased, and the white luster, the ink drying speed and the ink fusing property are poor. When the particle diameter is larger than 300 nm, the high shear flow property is increased and the printing gloss, adhesive strength and water resistance are lowered.

The gel content of the latex is suitably 30 to 95%, 50 to 95% or 70 to 95%, for example.

The present invention also provides a paper coating composition comprising an inorganic pigment, a natural binder and a synthetic binder, wherein the latex for paper coating is included as the synthetic binder.

The latex for paper coating may contain 5 to 30 parts by weight, or 5 to 20 parts by weight, based on 100 parts by weight of the pigment and calcium carbonate.

Further, the present invention can provide a paper obtained by calendering a paper coating liquid composition such as supercalenders.

According to the present invention, it is possible to stabilize the surface of the latex during the polymerization reaction and lower the viscosity of the latex during polymerization to give stable fluidity and to greatly improve the problem of solidification. Particularly, it is possible to provide a great effect in securing the stability of the latex having a small particle size.

Hereinafter, the embodiments of the present invention are specifically disclosed, and the present invention is not limited to the following embodiments.

Example  One

A 10 l high-pressure reactor equipped with a stirrer, a thermometer, a condenser, a nitrogen gas inlet, a monomer, an emulsifier and a polymerization initiator was continuously purged with nitrogen and heated to 80 ° C. 33 parts by weight of styrene, 5 parts by weight of methyl methacrylate, 5 parts by weight of acrylonitrile, 2 parts by weight of itaconic acid, 3 parts by weight of acrylic acid, 1 part by weight of allyl methacrylate, 1 part by weight of sodium dodecyl dibenzenesulfonate 1 part by weight of sodium methallylsulfonate, 0.4 part by weight of sodium bicarbonate, 79 parts by weight of ion-exchanged water and 1 part by weight of potassium persulfate were continuously introduced for 250 minutes. After all of the above components were added, the mixture was further stirred for 180 minutes to complete the polymerization.

The latex thus completed with shell polymerization had an average particle size of 130 to 140 nm, a conversion of 97 to 99%, a gel content of 80 to 90%, and a glass transition temperature (Tg) of 8 to 11 ° C.

Example  2

Prior to carrying out Example 1, the 10 l high pressure reactor was replaced with nitrogen, and then 10 parts by weight of 2-ethylhexyl acrylate, 75 parts by weight of styrene, 5 parts by weight of methyl methacrylate, 5 parts by weight of acrylonitrile , 2 parts by weight of itaconic acid, 3 parts by weight of acrylic acid, 7 parts by weight of sodium dodecyldibenzenesulfonate, 0.15 part by weight of t-dodecyl mercaptan, 0.5 part by weight of sodium bicarbonate and 420 parts by weight of ion- Respectively.

1 part by weight of calcium persulfate was added thereto, followed by stirring for about 300 minutes to complete the seed polymerization. At this time, the average particle diameter of the obtained seed was 58 nm, and the conversion was 99%.

Then, the reactor was filled with 8 parts by weight of seed latex (solid basis content) and the temperature was raised to 80 DEG C, 1.5 parts by weight of sodium dodecyldibenzenesulfonate in Example 1 and 0.5 parts by weight of sodium methallyl sulfonate The same procedure as in Example 1 was repeated except that the catalyst was used.

The latex thus completed with shell polymerization had an average particle size of 130 to 140 nm, a conversion of 97 to 99%, a gel content of 80 to 90%, and a glass transition temperature (Tg) of 8 to 11 ° C.

Example  3

Except that 8 parts by weight of seed latex in Example 2 was used and the temperature was raised to 80 캜 and 0.5 part by weight of sodium dodecyldimethylbenzenesulfonate and 1.5 parts by weight of sodium methallylsulfonate were used in Example 2 The same process as in Example 2 was repeated.

The latex thus completed with shell polymerization had an average particle size of 130 to 140 nm, a conversion of 97 to 99%, a gel content of 80 to 90%, and a glass transition temperature (Tg) of 8 to 11 ° C.

Example  4

Except that 8 parts by weight of seed latex in Example 2 was used and the temperature was raised to 80 DEG C and then 2 parts by weight of acrylic acid and 2 parts by weight of sodium methallyl sulfonate were used in Example 2. [ .

The latex thus completed with shell polymerization had an average particle size of 130 to 140 nm, a conversion of 97 to 99%, a gel content of 80 to 90%, and a glass transition temperature (Tg) of 8 to 11 ° C.

Example  5

2-ethylhexyl acrylate used in the preparation of the seed latex in Example 2 was replaced by butyl acrylate, 8 parts by weight of the seed latex in Example 2 was filled, and the temperature was raised to 80 ° C. -Ethylhexyl acrylate was replaced by 60 parts by weight of butyl acrylate and 22 parts by weight of styrene was used, the same processes as in Example 2 were repeated.

The average particle size of the obtained seed was 60 nm and the polymerization conversion rate was 99%. The latex having undergone shell polymerization in the second step had a particle size of 110 to 120 nm, a conversion rate of 97 to 99%, and a gel content of 80 to 90% , And the glass transition temperature (Tg) was 8 to 11 deg.

Example  6

The same procedure as in Example 5 was repeated except that 8 parts by weight of seed latex in Example 5 was used and the temperature was raised to 80 ° C and then 0.5 part by weight of sodium methallylsulfonate in Example 5 was used.

The thus obtained latex had a particle diameter of 110 to 120 nm, a conversion of 97 to 99%, a gel content of 80 to 90%, and a glass transition temperature (Tg) of 8 to 11 ° C.

Example  7

8 parts by weight of the seed latex in Example 5 was filled and the temperature was raised to 80 ° C. Then, 1 part by weight of itaconic acid in Example 5 and 2 parts by weight of sodium methallylsulfonate were used. The process was repeated.

The average particle diameter of the latex thus completed in the shell polymerization was 110 to 120 nm, the conversion rate was 97 to 99%, the gel content was 80 to 90%, and the glass transition temperature (Tg) was 8 to 11 ° C.

Comparative Example  One

The same procedure as in Example 2 was repeated except that 4 parts by weight of acrylic acid and 2 parts by weight of sodium dodecyldibenzenesulfonate were used in Example 2 and sodium methallylsulfonate was not used.

The thus obtained latex had a particle diameter of 130 to 140 nm, a conversion of 97 to 99%, a gel content of 80 to 90%, and a glass transition temperature (Tg) of 8 to 11 ° C.

Comparative Example  2

The same procedure as in Example 5 was repeated except that 4 parts by weight of itaconic acid and 2 parts by weight of sodium dodecyldibenzenesulfonate were used in Example 5 and sodium methallylsulfonate was not used.

The thus-obtained latex had a shell transition temperature of 110 to 120 nm, a conversion rate of 97 to 99%, a gel content of 80 to 90%, and a glass transition temperature (Tg) of 8 to 11 ° C.

[Test Example]

In order to measure the polymerization stability of the latex obtained in each of Examples 1 to 7 and Comparative Examples 1 and 2, the amount of the impurities was measured at 150, 200, and 325 mesh, The following is displayed.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 150mesh 17 54 22 38 12 37 8 159 321 200mesh 10 30 12 9 4 15 8 89 236 325mesh 9 17 18 12 8 20 5 92 271

As shown in Table 1, the latex for paper coating of Examples 1-7 satisfying the specific composition of the present invention had a small amount of impurities after completion of polymerization compared with the paper coating latexes of Comparative Examples 1 and 2 which did not satisfy the specific composition , And it was confirmed that the polymerization stability was excellent.

In addition, the physical properties of each latex were determined in the following manner.

* Particle size: Measured using a Laser Scattering Analyzer (NiComp).

* Chemical Stability: 0.06 ml of latex is dropped in 4 ml of CaCl ₂ solution having different concentration, and after 15 seconds, it is shaken for 5 seconds, and the cohesion state of latex is visually confirmed. The concentration of the CaCl ₂ solution in which the latex is not agglomerated means chemical stability, and the unit is%. The larger the value, the better the chemical stability.

When dropping the latex in the CaCl ₂ solution in order to compare a specific chemical stability of each example and comparative example latex compared to determine the CaCl ₂ concentration of the latex is agglomerated after 20 seconds as follows.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Latex
Coherent
CaCl ₂ solution (%) 0.35 0.32 0.43 0.45 0.35 0.3 0 0.44 0.1 0.08

As shown in Table 2, the latex for paper coating of Examples 1-7 satisfying the specific composition of the present invention had a chemical (relative to divalent cation) latex of Comparative Examples 1 and 2 And the stability was confirmed to be excellent.

* Gel content: After adjusting the pH of the polymerized latex to 6 ~ 8, it is dried at room temperature for over 24 hours. When the film is sufficiently formed, it is cut into a suitable size and placed in a 200-mesh screen and dissolved in excess acetone for 14 hours, and the content of insoluble matter is expressed as a percentage.

The coating solution was prepared according to the following formulation with each latex, and the physical properties were further measured.

Formulation of paper coating liquid: First grade clay 20 parts by weight, calcium carbonate 80 parts by weight, each latex 10.5 parts by weight, oxidized starch 1.3 parts by weight.

Distilled water: The coating liquid was added so that the solid content was 67%.

* Low Shear Viscosity: The viscosity of the coating liquid is measured using a BF type viscometer with a rotor number 3 measured at 60 rpm for 1 minute (unit: cP).

* High shear viscosity: The measured value at 4400 rpm (unit: cP) using a Hercules Viscometer (KRK type, model KC-801C).

* Stability: After preparing the coating solution, stir for 10 minutes using Maron Tester at 70 ° C, and measure the coagulated product by # 325 mesh. The unit is ppm, and a larger value indicates that the stability is poor.

The results of the physical properties measurement are summarized in the following table.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Example 5 Example 6 Example 7 Comparative Example 2 Low shear
Viscosity (cp) 718 790 753 802 855 818 796 783 958 Classical stage
Viscosity (cp) 25.3 26.5 26.1 26.8 27.5 24.2 25.9 24.0 26.2 stability
(ppm) 280 320 115 120 530 255 230 190 935

As shown in Table 3, the paper coating liquid prepared from the paper coating latex of Examples 1-7 satisfying the specific composition of the present invention was prepared using the paper coating latex of Comparative Examples 1 and 2 which did not satisfy the specific composition It was confirmed that the low shear viscosity and high shear viscosity of the paper coating liquid were low and the stability was also excellent.

The prepared paper coating solution was coated according to a calender technique under the following conditions to obtain a coated paper.

Coating: Rod Manual Coating (Rod Coating, No. 6)

Drying oven, 105 ℃, 30 seconds

Calendars Super Calendars, 80 ℃, 100kg / cm, 4m / min, 2 passes

Origin: Commercial land (72gsm basis)

* Adhesion: After printing several times on an RI press, the degree of the scoring was judged by naked eyes and evaluated by the 5-point method. The higher the score, the better the adhesion. The average values were obtained by measuring the tack values of 10, 12 and 13, respectively.

* Water resistance: Wet water is added by using a Morton roll in an RI printing machine and printed, and the degree of the peeling is measured in the same manner as the above adhesion. And printing was performed once using ink of Tack Value 10 and then measured.

* Ink Drying Rate: After printing on an RI press, the degree of ink smearing over time was measured by a 5-point method. The higher the score, the faster the ink drying rate.

* Adherence: After adding wetted water in an RI press, print the ink and measure the degree of ink transfer. The low tack value ink is used to prevent tearing, and the higher the score, the higher the tackling ability.

* Blank Gloss: The average value of various parts of the coated paper was measured using Optical Gloss Meter (HUNTER type, 75 ° ~ 75 °).

* Print gloss: After 24 hours of printing on an RI press, measure in the same manner as white glossy.

The results of the physical properties measurement are summarized in the following table.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Example 5 Example 6 Example 7 Comparative Example 2 Adhesion 3.9 3.9 4.0 4.0 3.7 4.3 4.3 4.4 4.1 Water resistance 4.5 4.4 4.5 4.5 4.3 4.3 4.4 4.3 4.0 Ink drying rate 3.9 3.8 4.0 4.1 3.8 3.7 3.7 4.0 3.2 Development 4.1 4.2 4.1 4.0 4.3 4.4 4.5 4.4 4.4 blank
Polish 66 67 66 67 67 66 67 67 66 print
Polish 82 82 80 80 82 85 85 84 85

As shown in Table 4, the papers made from the paper coating latex of Examples 1 to 4 and 5 to 7, which satisfy the specific composition of the present invention, , It was found that the most important adhesive property was obtained in paper properties compared to the paper prepared using the ink, and the water resistance and ink drying speed were also improved. In particular, in the case of Examples 5 to 7, the best effects can be provided.

Claims (16)

A latex for paper coating obtained by emulsion polymerization of a mixture of a styrenic monomer, an acrylate monomer, an ethylenically unsaturated acid monomer, a crosslinking monomer and an unsaturated alkyl derivative having a sulfonic acid group.
The method according to claim 1,
Wherein the latex comprises one to three layers of the shell obtained by emulsion-polymerizing the mixture.
3. The method of claim 2,
Wherein the mixture contains 15 to 80 parts by weight of a styrene monomer, 20 to 80 parts by weight of an acrylate monomer, 1 to 10 parts by weight of an ethylenically unsaturated acid monomer, 0.1 to 5 parts by weight of a crosslinking monomer, And 0.1 to 2 parts by weight of an unsaturated alkyl derivative having a group represented by the following formula (1).
The method of claim 3,
Wherein the mixture further comprises at least one copolymerizable vinyl monomer selected from an unsaturated carboxylic acid alkyl ester, an unsaturated carboxylic acid hydroxyalkyl ester, a carboxylic acid amide, a carboxylic acid amide derivative and an aromatic vinyl monomer Latex for paper coating.
The method of claim 3,
Wherein the mixture further comprises at least one vinyl cyanide monomer selected from acrylonitrile, methacrylonitrile, and ethacrylonitrile.
The method according to claim 1,
Wherein the styrene-based monomer is at least one selected from the group consisting of styrene,? -Methylstyrene,? -Ethylstyrene, p-methylstyrene and vinyltoluene.
The method according to claim 1,
Wherein the acrylate monomer is an acrylate having an alkyl group having 1 to 20 carbon atoms.
8. The method of claim 7,
Wherein the acrylate-based monomer is an acrylate having an alkyl group having 1 to 6 carbon atoms.
The method according to claim 1,
Wherein the ethylenically unsaturated acid monomer is at least one selected from the group consisting of methacrylic acid, acrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid monoethyl ester, fumaric acid monobutyl ester and maleic acid monobutyl ester. For latex.
The method according to claim 1,
The crosslinking monomer may be selected from the group consisting of allyl acrylate, allyl methacrylate, glycidyl acrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, dipropyl glycol diacrylate, Tripropylene glycol diacrylate, ethylene glycol diacrylate, neopentyl glycol diacrylate, trimethylene propyl triacrylate, propoxylated glycerol triacrylate; And a silane coupling agent represented by R-Si≡ (X) ₃ or R-Si≡ (R ') (X) ₃ (wherein R includes vinyl, epoxy and a free radical having a substituted or unsubstituted amino or mercapto group , R 'is an alkyl group having 4 or less carbon atoms, and X is methoxy, ethoxy or chlorine.
The method according to claim 1,
The unsaturated alkyl derivative having a sulfonic acid group includes sodium methallylsulfonate, sodium metalylsulfonate and sodium vinylsulfonate Wherein the latex is at least one selected from the group consisting of polyvinyl alcohol and polyvinyl alcohol.
The method according to claim 1,
Wherein the latex has a gel content of 30 to 95% and a glass transition temperature of -30 to 70 ° C.
The method according to claim 1,
Wherein the latex has a particle diameter of 50 to 300 nm.
A paper coating liquid composition comprising an inorganic pigment, a natural binder and a synthetic binder, wherein the latex for paper coating according to claim 1 is contained as the synthetic binder.
15. The method of claim 14,
Wherein the artificial binder is 5 to 30 parts by weight based on 100 parts by weight of the inorganic pigment.
A paper obtained by calendering the paper coating liquid composition of claim 14.