JP2003268160A - Latex composition and composition for paper coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the wet tackiness of a latex composition, which serves as an index of backing roll contamination characteristics, without deteriorating such physical properties of coated paper as dry pick strength and wet pick strength. <P>SOLUTION: The latex composition contains a polyethylene glycol in an amount of 0.1-5 wt.% based on 100 pts.wt. (in terms of solid content) of a copolymer latex obtained by subjecting a monomer mixture of 20-70 wt.% of a conjugated diene monomer and 30-80 wt.% of other monomer copolymerizable therewith no emulsion polymerization. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a latex composition and a composition for paper coating using the same, and more specifically, it is used for coated paper or coated paperboard for offset printing, gravure printing and the like. The present invention relates to a high-performance copolymer latex composition suitable as a binder for paper coating, and a paper coating composition using the same.

[0002]

2. Description of the Related Art Conventionally, synthetic copolymer latex has been widely used as, for example, a binder for paper coating, a binder for carpet back sizing, a binder for fiber bonding such as non-woven fabric or artificial leather, or an adhesive for various materials. It is used. Coated paper is used for the purpose of improving the printability of paper and improving optical properties such as gloss, and the pigments such as kaolin clay, calcium carbonate, satin white, talc, and titanium oxide, and their binders are formed on the surface of the raw paper that has been produced. Is coated with a copolymer latex as the above and a paper coating composition containing starch, polyvinyl alcohol, carboxymethyl cellulose and other water-soluble polymers as main constituents as a viscosity modifier or an auxiliary binder.

Here, as a copolymer latex as a binder, a styrene-butadiene copolymer latex emulsion-polymerized by using styrene and butadiene as main monomer components, so-called SB latex, has been generally used. . In recent years, as the demand for color printed magazines, pamphlets, and advertisements has increased, the printing speed has been increased, and the required standard for coated papers and pigment binders has become more sophisticated. Among them, there is a strong demand for improvement in ink pick resistance, that is, so-called pick strength. At the same time, in recent years, there is an increasing demand for reducing the amount of added latex for the purpose of cost reduction, and a latex having a sufficient pick strength even with a small addition amount is required.

On the other hand, in order to improve the production capacity of coated paper, in recent years, high-speed coating has been advanced, and the coating operability has been improved due to the increase in speed, and in particular the backing roll stain resistance, which is a major obstacle, has been improved. Improvement is required. In order to eliminate dirt on the backing roll, it is possible to install a flow clean doctor, which is a roll cleaning device, in which cleaning water is applied to the back side of the backing roll that contacts the paper, and the blade cleans the dirt and cleaning water on the backing roll surface. However, it has not been completely resolved.

To improve the stain resistance of the backing roll, it is effective to reduce the tackiness of the coated paper surface in contact with the backing roll, that is, the tackiness of the copolymer latex. In case of wearing, since the cleaning water is attached even after scraping with the blade, it is effective to reduce the tackiness of the coated paper surface in the wet state, that is, the tackiness of the copolymer latex in the wet state. Is. In order to improve the pick strength described above, for example, a method of adjusting the gel content of the copolymer or an improved method of adjusting the copolymer composition has been proposed, but the improvement of the pick strength and the reduction of the tackiness are opposite. It often correlates and it is very difficult to improve both.

For example, in order to improve the pick strength, a method of increasing the amount of the conjugated diene monomer added is known, but this method is not preferable because the tackiness increases. Further, although the pick strength is improved by the method of using a large amount of the monomer having a functional group, the workability is remarkably lowered because the viscosity of the latex and the coating color becomes abnormally high. in this way,
The conventional technology cannot cope with further speeding up of printing and coated paper production, and the appearance of copolymer latex as a binder that enhances productivity and enables the production of high-quality coated paper is strong. The current situation is what is being sought.

[0007]

As described above, the conventional binder for paper coating is improved in the pick strength of the coated paper using the binder and in the wet tackiness which is an index of the stain resistance property of the backing roll. Could not be satisfied at the same time. Under such circumstances, an object of the present invention is to provide a high-performance latex composition which is excellent in pick strength and backing roll stain resistance in coated paper.

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies in view of the problems of the prior art as described above, and as a result, have found that a latex composition containing polyethylene glycol achieves the object. Heading out, the present invention has been completed. That is, the first aspect of the present invention is obtained by emulsion-polymerizing a monomer composed of 20 to 70% by weight of a conjugated diene monomer and 30 to 80% by weight of another monomer copolymerizable therewith. A latex composition comprising 0.1 to 5% by weight of polyethylene glycol based on 100 parts by weight of a copolymer latex (solid content).

The second aspect of the invention is that, with respect to 100 parts by weight of the pigment,
It is a composition for paper coating using 3 to 30 parts by weight of the latex composition described in the first aspect of the invention. The present invention will be described in more detail below. Examples of the conjugated diene-based monomer used in the present invention include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2-methyl-1, Although 3-butadiene, 1,3-pentadiene, chloroprene, 2-chloro-1,3-butadiene, cyclopentadiene, etc. can be mentioned, 1,3-butadiene is preferable. These conjugated diene monomers are used alone or in combination of two or more.

The amount of the conjugated diene monomer used is preferably 20 to 70% by weight, more preferably 30 to 6% by weight.
It is 0% by weight. If the amount used is less than 20% by weight, the resulting polymer becomes brittle and the pick strength of coated paper cannot be obtained sufficiently. On the other hand, if it exceeds 70% by weight, the stickiness resistance of the copolymer latex, which is an index of the backing roll stain resistance property in paper coating, becomes insufficient, and the object of the present invention cannot be sufficiently achieved.

Other monomers copolymerizable with the conjugated diene monomer used in the present invention include vinyl cyanide monomer, aromatic vinyl monomer and ethylenically unsaturated carboxylic acid. Monomers, (meth) acrylic acid alkyl ester monomers, (meth) acrylamide-based monomers, carboxylic acid vinyl esters such as vinyl acetate, vinyl halides such as vinyl chloride, aminoethyl acrylate, dimethylaminoethyl Examples thereof include amino group-containing ethylenic monomers such as acrylate and sodium styrenesulfonate. These copolymerizable monomers are 1
They may be used alone or in combination of two or more.

Examples of the vinyl cyanide-based monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and the like, and acrylonitrile is particularly preferable. These vinyl cyanide-based monomers may be used alone or in combination of two or more, and the preferable amount thereof is less than 70% by weight, more preferably less than 50% by weight. 70% by weight
The above is not preferable because the pick strength of the coated paper cannot be obtained.

Examples of aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, vinylxylene, bromostyrene and vinylbenzyl. Examples thereof include chloride, p-t-butylstyrene, chlorostyrene, alkylstyrene, divinylbenzene and trivinylbenzene, with styrene being particularly preferred. Examples of the ethylenically unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and crotonic acid. These ethylenically unsaturated carboxylic acid monomers are 1
One kind or a combination of two or more kinds may be used, and the preferable amount thereof is selected in the range of 0.5 to 10 parts by weight, more preferably 1 to 7 parts by weight based on the weight of all the monomers.
If this amount is less than 0.5 parts by weight, the dispersion stability of the latex is not sufficient, various problems occur during coating solution preparation and coating, and the pick strength is low. If it exceeds 10 parts by weight, the viscosity of the latex or the coating liquid becomes too high, and
The wet pick strength tends to decrease, which is not preferable.

Examples of the (meth) acrylic acid alkyl ester monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate and t-butyl (meth) acrylate. , Isobutyl (meth) acrylate,
n-amyl (meth) acrylate, isoamylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, cyclohexyl (meth) acrylate , Phenyl (meth) acrylate, benzyl (meth) acrylate, 2-ethyl-hexyl (meth)
Acrylate, 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, propylene Glycol di (meth) acrylate, 1,5-pentanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, diethylene glycol ethoxy acrylate , Triethylene glycol di (meth) acrylate,
Tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate , Allyl (meta)
Acrylate, bis (4-acryloxypolyethoxyphenyl) propane, methoxypolyethylene glycol (meth) acrylate, stearyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, 2,
2-bis [4-((meth) acryloxyethoxy) phenyl] propane, 2,2-bis [4-((meth) acryloxydiethoxy) phenyl] propane, 2,2-bis [4-((meth)) Examples thereof include acryloxy / polyethoxy) phenyl] propane and isobornyl (meth) acrylate.

Examples of the (meth) acrylamide type monomer include N-monoalkyl (meth) acrylamides such as (meth) acrylamide, N-methylol (meth) acrylamide, N-methyl (meth) acrylamide, N, N-. Examples thereof include N, N-dialkyl (meth) acrylamides such as dimethyl (meth) acrylamide, glycidylmethacrylamide, N-alkoxy (meth) acrylamides, and 2-acrylamido-2-methylpropanesulfonic acid.

The polyethylene glycol used in the present invention preferably has a molecular weight of around 1000, but is not particularly limited by the molecular weight. The amount used is 0.1
˜5.0% by weight, preferably 0.5 to 3% by weight. If it is less than 0.1% by weight, the effect of improving wet tackiness will not be obtained, and if it is 5% by weight or more, the wet pick strength will decrease, which is not preferable. When emulsion-polymerizing the monomer used in the present invention, the above-mentioned monomer, a chain transfer agent and a surfactant, and a radical polymerization initiator are optionally used in an aqueous medium by a conventionally known method. A method of producing an aqueous dispersion liquid of copolymer particles, that is, a copolymer latex by polymerizing a monomer in a dispersion system containing other additive component as a basic constituent component is used. In the polymerization, a method of making the monomer composition uniform in the entire polymerization process or a method of changing the morphological composition of the latex particles to be produced by changing the composition stepwise or continuously in the polymerization process Various methods can be used as needed.

The concentration of the copolymer in this copolymer latex is selected in the range of 40 to 60% by weight, and the average particle size thereof is preferably in the range of 40 to 400 nm, more preferably 50 to 200 nm. It is preferably in the range. The average particle size can be adjusted by the use ratio of the seed latex or the surfactant, etc. Generally, the higher the use ratio, the smaller the average particle size of the produced copolymer latex. Polymerization of the seed latex may be carried out in the same reaction vessel prior to the polymerization of the latex of the present invention, or a seed latex polymerized in a different reaction vessel may be used.

The method of adding the monomer composition may be a batch addition method of the monomer composition, a method of adding a part of the monomer composition and then intermittently or continuously according to the progress of polymerization, Further, any method such as continuously adding the monomer composition may be used. Examples of the chain transfer agent include mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, n-dodecyl mercaptan and t-dodecyl mercaptan, and halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide. , Α-methylstyrene dimer and the like are used.

Examples of the surfactant include aliphatic soap, soap of rosin acid, alkyl sulfonate, dialkyl aryl sulfonate, alkyl sulfosuccinic acid, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl aryl sulfate and the like. Anionic surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, nonionic surfactant such as oxyethyleneoxypropylene block copolymer, lauryl betaine, each salt of stearyl betaine, Double-sided surfactants such as lauryl-β-alanine, each salt of lauryl di (aminoethyl) glycine, and the like can be mentioned.

Examples of the polymerization initiator include water-soluble initiators such as potassium persulfate, sodium persulfate and ammonium persulfate, redox type initiators and oil-soluble initiators such as benzoyl peroxide. The polymerization temperature in this emulsion polymerization is usually selected in the range of 40 to 100 ° C, but the polymerization may be carried out at a lower temperature by the redox polymerization method or the like. The polymerization temperature in each polymerization step may be the same or different. The polymerization time is usually 5 to 30 hours.

In the present invention, various polymerization regulators can be added if necessary. For example, as the pH adjusting agent, it is possible to add a pH adjusting agent such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium hydrogencarbonate, sodium carbonate, disodium hydrogenphosphate, etc. It is particularly preferable in terms of enhancing the balance between strength and wet pick strength, and is suitable as a pH adjusting agent after polymerization. Also, various chelating agents such as sodium ethylenediaminetetraacetate can be added as a polymerization modifier. Further, if necessary, an alkali-sensitive latex may be added to the latex composition of the present invention.

When the latex composition of the present invention is used as a binder for a coating material for paper coating, it can be carried out in a usual manner. That is, in water in which a dispersant is dissolved, kaolin clay, calcium carbonate, titanium dioxide, aluminum hydroxide, satin white, inorganic pigments such as talc, organic pigments known as plastic pigments and binder pigments, starch, casein,
Add latex composition together with various additives such as polyvinyl alcohol, water-soluble polymer such as carboxymethyl cellulose, thickener, dye, defoaming agent, preservative, waterproofing agent, lubricant, printability improving agent, water retention agent, etc. This is a mode in which they are mixed to form a uniform dispersion liquid. The use ratio of the pigment and the latex composition of the present invention can be appropriately determined according to the purpose of use of the composition, but the latex is preferably 3 to 30 parts by weight with respect to 100 parts by weight of the pigment. The paper coating solution can be applied to the base paper by a usual method using various blade coaters, roll coaters, air knife coaters, bar coaters and the like.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Each property was determined as follows. (1) Properties of the latex composition (ii) Particle size Light scattering particle size analyzer (Model 600 manufactured by CN Wood Co.)
The average diameter of the copolymer latex particles was measured according to 0). (Ro) After applying latex to the wet adhesive Mylar film with a No. 12 wire bar, it is dried at 130 ° C. for 60 seconds. Superimpose it on a surface of a black Racha paper with its surface moistened with water, and pass it through a super calender with a temperature of 70 ° C and a linear pressure of 20 kg / cm. The black Racha paper was peeled off from the Mylar film, and the transfer of the Rasha paper fibers onto the latex film was visually observed. Evaluation is 1
The evaluation was carried out by the 0-point evaluation method, and the less the metastasis, the higher the score.

(2) Evaluation of paper coating performance (ii) Dry pick strength Using a RI printing tester (Ming Seisakusho), a backing paper (30 cm) prepared by arranging coated paper (1.5 cm × 20 cm) on the center part
cm x 25.5 cm, printing ink (manufactured by Toka Dye Company,
Product Name: SD Super Deluxe 50 Beni B (Tuck 18
0.4 cc) was printed together with the mount in a printing area of 25 cm × 21 cm and overprinted on the coated paper. The picking state that appeared on the rubber roll was lined on another mount and the state was observed. The evaluation was carried out by a 10-point evaluation method, and the smaller the picking phenomenon, the higher the score.

(Ro) Wet pick strength Using a RI printing tester (Ming Seisakusho), a coated paper (30 cm) was applied along with coated paper (1.5 cm × 20 cm) in the center.
Water is applied to the surface of the coated paper with a molton roll (m x 25.5 cm), and immediately after that, printing ink (manufactured by Toka Color Co., Ltd., trade name: SD Super Deluxe 50 Beni B (from Tack 15) 0.4 cc is 25 cm). Printing was performed once with a printing area of × 21 cm, the picking state that appeared on the rubber roll was lined on another backing sheet, and the state was observed.The evaluation was performed by a 10-point evaluation method, and the less picking phenomenon, the higher the score. And

[0026]

[Examples 1 and 2] 3.0 parts by weight of an aqueous dispersion of seed particles having an average diameter of 35 nm (seed solid content concentration 35% by weight) was placed in a pressure resistant reaction vessel equipped with a stirrer and a temperature control jacket, and water was further added. 70 parts by weight, 0.1 part by weight of sodium lauryl sulfate, 2.5 parts by weight of itaconic acid and 0.5 part by weight of fumaric acid were charged, and the internal temperature was raised to 80 ° C. Then, a monomer composition obtained by mixing the monomers shown in Table 1 with a chain transfer agent, 15 parts by weight of water, 1 part by weight of sodium peroxodisulfate, 0.1 part by weight of sodium lauryl sulfate, and 0.2 parts of sodium hydroxide. The initiator system aqueous solution consisting of parts by weight was added at a constant flow rate over 5 hours and 6 hours, respectively.
The temperature of 80 ° C. was maintained for 2 hours and then cooled. Next, sodium hydroxide was added to the produced copolymer latex to adjust the pH to 8. Next, the unreacted monomer was removed by the steam stripping method, polyethylene glycol shown in Table 1 was added, and the mixture was filtered through a 200-mesh wire net. The latex composition was finally adjusted to a solid content concentration of 50% by weight.

Next, a paper coating composition having the following composition was prepared using the obtained latex. (Compound formulation) Kaolin clay 70 parts by weight Calcium carbonate 30 parts by weight Sodium polyacrylate 0.2 parts by weight Sodium hydroxide 0.1 parts by weight Phosphoesterified starch 2.5 parts by weight Latex composition 12 parts by weight Water (total (Added so that the solid content becomes 64%)

As kaolin clay, Ultra White 90 (manufactured by ENGELHARD), as calcium carbonate, Carbital 90 (manufactured by ECC), and as sodium polyacrylate, Aron T-40 (manufactured by Toagosei Co., Ltd.), MS-46 as phosphate esterified starch
00 (manufactured by Nippon Shokuhin Kako Co., Ltd.) was used. The composition for paper coating thus obtained was coated on a base paper having a basis weight of 75 g / m ^{2 by} a double-sided blade coating so that the coating amount was 14 g / m ² on one side to obtain a coated paper. Table 1 shows the evaluation results obtained using this coated paper. As is clear from Table 1, all of the coated papers using the latex composition of the present invention as a binder are excellent in coated paper physical properties such as pick strength and wet pick strength in coated paper, and in paper coating. It can be seen that the wet tackiness, which is an index of the backing roll stain resistance property, is excellent.

[0029]

Comparative Examples 1 to 3 A latex composition was prepared in the same manner as in Example 1 except that the monomer component, chain transfer agent and polyethylene glycol shown in Table 1 were used. A coating liquid and coated paper were prepared and evaluated. Comparative Example 1 in which polyethylene glycol was not added was inferior in wet adhesion, Comparative Example 2 in which the amount of polyethylene glycol added was too large was inferior in wet pick strength, and Comparative Example 3 in which the amount of butadiene added was decreased was in dry pick strength. Is inferior.

[0030]

[Table 1]

[0031]

EFFECTS OF THE INVENTION The wet tackiness, which is an index of soiling characteristics of backing rolls, can be improved without impairing the physical properties of the coated paper such as dry pick strength and wet pick strength.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4J002 AC021 BC011 BC051 BC081                       BC091 BC111 BG011 BG041                       BG051 BG071 BG101 BG131                       BH021 BL011 BL021 CH022                       GK04 HA07                 4L055 AG11 AG12 AG27 AG48 AG63                       AG70 AG71 AG75 AG76 AG88                       AG89 AH02 AH37 AH50 AJ04                       BE08 EA32 FA13 FA30 GA19

Claims (2)

[Claims] 1. A conjugated diene monomer of 20 to 70% by weight,
And polyethylene glycol 0.1 to 100 parts by weight of a copolymer latex (solid content) obtained by emulsion polymerization of a monomer consisting of 30 to 80% by weight of another monomer copolymerizable with this. A latex composition comprising 5% by weight. 2. A paper coating composition comprising 3 to 30 parts by weight of the latex composition according to claim 1 with respect to 100 parts by weight of a pigment.