JP2004225219A5 - - Google Patents

Description

[Claims]
    (1) 23 to 70 parts by weight of an aliphatic conjugated diene monomer, (b) 0.1 to 7 parts by weight of an ethylenically unsaturated carboxylic acid monomer, and (c) the above monomer A monomer comprising (a) and 23 to 76.9 parts by weight of another monomer copolymerizable with the monomer (b) (provided that (a) + (b) + (c) = 100 parts by weight) Is a copolymer latex obtained by emulsion polymerization of a polymer, and is detected in a molecular weight distribution obtained by gel permeation chromatography (GPC) earlier than an elution time corresponding to a polystyrene equivalent molecular weight of 1,000,000. (GPC measurement gel) content is 35% or more, and the weight average molecular weight of a component detected later than the elution time corresponding to 1 million in terms of polystyrene equivalent molecular weight is 40,000 to 400,000.That isFeatureFor non-contact coatingCopolymer latex.
    (2) The copolymer latex for non-contact coating according to claim 1, wherein a toluene-insoluble content is 35% by weight or more.
    (3) The copolymer latex for non-contact coating according to claim 1 or 2, wherein the weight average molecular weight is 50,000 to 200,000.
    (4) The copolymer latex for non-contact coating according to any one of claims 1 to 3, wherein the non-contact coating is curtain coating or spray coating.
    (5) The method for producing a copolymer latex for non-contact coating according to any one of claims 1 to 4, wherein the monomer (a) to (c) is used in the presence of a radical catalyst and a reducing agent. A method for producing a copolymer latex for non-contact coating, comprising subjecting a polymer to emulsion polymerization.
    6. It is characterized by comprising 100 parts by weight of a pigment and 0.5 to 100 parts by weight (in terms of solid content) of the copolymer latex for non-contact coating according to any one of claims 1 to 4. Non-contact coating composition.
    7. A coated paper obtained by applying the non-contact coating composition according to claim 6.

[0002]
[Prior art]
2. Description of the Related Art In general, coated paper coated with a composition mainly containing a white pigment such as kaolin or calcium carbonate and an aqueous binder is manufactured in order to improve the appearance and printability of paper. In recent years, the production of coated paper has greatly increased due to the increase in magazine visualization, newspaper insert advertisements, flyers, and the like. Today, these coated papers are mainly coated and manufactured by blade coaters, gate roll coaters, and metering size presses.
In producing these coated papers, it is particularly important to cover the base paper satisfactorily with a small coating amount in terms of cost. In order to improve the coating property, it is important that the color is hardly pushed into the base paper and the coating layer is made bulky. However, when the above-mentioned coater is used, the coating liquid is considerably pushed into the base paper due to its mechanism, and the coating layer is unlikely to be bulky.
On the other hand, it is known that when a coating is applied by a so-called non-contact type coating method such as curtain coating or spray coating, the coating liquid is not pushed into the base paper and the coating layer becomes bulky. . However, curtain coating and spray coating are not generally used for producing coated paper. One of the major reasons is as follows. In the case of non-contact type coating, the coating layer is certainly bulky, but the strength of the coating layer is weaker than in the case of blade coating, for example, so that a large amount of binder must be used. That is because the amount of the binder is more become costly.
In order to improve the strength of the coating layer without using too much binder, it is necessary to select or develop a copolymer latex having good adhesive strength. In order to improve the adhesive strength of the copolymer latex, for example, a method of adjusting the gel content in the copolymer latex and an improvement method of adjusting the glass transition point of the copolymer have been proposed. However, these alone do not reach a satisfactory level of adhesive strength. There is also a method for improving the adhesive strength of the copolymer latex by producing a copolymer latex using a large amount of a monomer having a functional group, but in this method, the viscosity of the coating liquid is high. Therefore, it is often not suitable for use in curtain coating or spray coating.

[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide sufficient adhesive strength in non-contact type coating such as curtain coating or spray coating, and to provide other coated paper properties such as wet strength and print gloss, and An object of the present invention is to provide a copolymer latex having excellent properties and a paper coating composition using the same.

[0004]
[Means for Solving the Problems]
Non-contact coating latex of the present invention,
(A) 23 to 70 parts by weight of an aliphatic conjugated diene monomer,
(B) 0.1 to 7 parts by weight of an ethylenically unsaturated carboxylic acid monomer, and (c) other monomers 23 to 23 copolymerizable with the above monomers (a) and (b). This is a copolymer latex obtained by emulsion polymerization of a monomer consisting of 76.9 parts by weight. In the molecular weight distribution obtained by gel permeation chromatography (GPC), the molecular weight corresponds to 1,000,000 in terms of polystyrene. The content of the component (GPC measurement gel) detected earlier than the elution time is 35% or more, and the weight average molecular weight of the component detected later than the elution time corresponding to 1,000,000 in terms of polystyrene equivalent molecular weight is 40,000 to 400, is 000.
The copolymer latex for non-contact coating of the present invention has a high molecular weight copolymer or a crosslinked gel component thereof when the GPC measurement gel content is 35% or more in the molecular weight distribution obtained by GPC measurement. Includes a large amount and increases the polymer strength. Since the weight average molecular weight of the component detected later than the elution time corresponding to 1,000,000 in terms of the molecular weight in terms of polystyrene is 40,000 to 400,000, the adhesive strength is strong, and the low molecular weight component is small. Low tackiness and good mechanical stability. Therefore, operability is improved. The operability mentioned here is based on the basic performance requirement that the lip, which is the discharge port of paint, must not be closed in curtain coating and the nozzle must not be clogged in spray coating. It is.
In addition to the above, when the toluene-insoluble content is 35% by weight or more , the adhesiveness is further reduced, the mechanical stability is improved, and the operability in the coating method is not anxious. The solvent resistance is also improved, and the printing gloss is improved.
The copolymer latex for non-contact coating of the present invention is obtained by emulsion polymerization in the presence of a radical catalyst and a reducing agent, and has excellent adhesive strength and other coated paper properties, and good operability. Is expressed.
Further, the composition for non-contact coating of the present invention is a composition for curtain coating and spray coating containing the copolymer latex and the pigment of the present invention as main components, by using this, A coated paper having excellent adhesive strength, good water resistance and good print gloss can be obtained. Particularly suitable for offset printing paper, it can also be used for various printing papers such as gravure printing paper.

[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the non-contact coating latex of the present invention and the non-contact coating composition using the non-contact coating latex of the present invention will be described in detail.
(Composition and properties of copolymer latex)
<Composition of monomer>
The (a) aliphatic conjugated diene monomer used in the production of the copolymer latex of the present invention is a component for imparting appropriate flexibility and elongation to the obtained polymer and imparting impact resistance. .
(A) Specific examples of the aliphatic conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl - 1,3-butadiene, 2-ethyl-1,3-butadiene, and 2-methyl Examples thereof include -1,3-butadiene, 1,3-pentadiene, chloroprene, 2- chloro -1,3-butadiene, and cyclopentadiene. These can be used alone or in combination of two or more. Of these, butadiene is particularly preferred.
(A) The amount of the aliphatic conjugated diene-based monomer used is selected from the range of 23 to 70 parts by weight, preferably 30 to 60 parts by weight, based on 100 parts by weight of all the monomers. If the amount is less than 23 parts by weight, sufficient adhesive strength cannot be obtained, while if it exceeds 70 parts by weight , the adhesive strength decreases.

(C) Other monomers copolymerizable with (a) the aliphatic conjugated diene monomer and (b) the ethylenically unsaturated carboxylic acid monomer which can be used in the production of the copolymer latex of the present invention. As the monomer (hereinafter, also referred to as “(c) another monomer”), a compound having one or more polymerizable unsaturated bonds in a molecule can be used.
(C) Other monomers include, for example, (a) an aromatic vinyl compound, (b) an acrylic acid ester and a methacrylic acid ester, (c) an unsaturated dibasic acid alkyl ester, and (ho) a vinyl cyanide compound. , (F) acrylamide and methacrylamide, (g) vinyl ester, (h) vinyl ether, (li) vinyl halide, (nu) basic monomer having an amino group, (l) vinylpyridine, (ヲ) olefin , (A) silicon-containing α, β-ethylenically unsaturated monomers, and (f) allyl compounds. These can be used alone or in combination of two or more.

Examples of (b) acrylates and methacrylates include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, 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, hydroxyethyl (meth) acrylate, hydroxypropyl Meth) acrylate, hydroxycyclohexyl (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, triethylene glycol Di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, penta Risritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, allyl (meth) acrylate, bis (4-acryloxypolyethoxyphenyl) propane, methoxypolyethylene glycol (meth) ) Acrylate, β- (meth) acryloyloxyethyl hydrogen phthalate, β- (meth) acryloyloxyethyl hydrogen succinate, 3-chloro-2-hydroxypropyl (meth) acrylate, stearyl (meth) acrylate, phenoxyethyl ( (Meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, 2-hydroxy-1,3-di (meth) acryloxypropane, 2,2-bis [4-((meth) acryl (Xyethoxy) phenyl] propane, 2,2-bis [4-((meth) acryloxydiethoxy) phenyl] propane, 2,2-bis [4-((meth) acryloxypolyethoxy) phenyl] propane, isobornyl (meth) Acrylate and the like.

<Properties of latex polymer>
Copolymer latex of the present invention is the content of GPC measurement gel 35% or more and a weight average molecular weight of the component to be detected later than the elution time corresponding to 1 million molecular weight in terms of polystyrene is 40, 000 Must be 400,000.
The GPC measurement gel content is defined as follows. In the molecular weight distribution obtained from the GPC measurement, the components detected earlier than the elution time corresponding to 1,000,000 in terms of the molecular weight in terms of polystyrene are the detection amount on the vertical axis and the elution time on the horizontal axis, as shown in FIG. In the elution curve 1 taken, assuming that the area surrounded by the elution curve 1 and the horizontal axis is the total area S (S = S1 + S2), the component is detected earlier than the elution time T1 corresponding to 1,000,000 in terms of polystyrene equivalent molecular weight. (S1). The component detected later than the elution time T1 corresponding to 1,000,000 in terms of the molecular weight in terms of polystyrene is the component (S2) detected later than the time T1 in which the polymer having the molecular weight of 1,000,000 is detected in FIG. Say. The content (%) of the GPC measurement gel obtained as described above is determined by the following equation.
GPC measurement Gel content (%) = S1 / (S1 + S2) × 100
The copolymer latex for non-contact coating of the present invention has a gel content measured by GPC as defined above of 35% or more. When the content of the gel measured by GPC is 35% or more, a large amount of a high molecular weight copolymer or a crosslinked gel component thereof is contained. For this reason, the polymer strength is increased, which contributes to the improvement of the adhesive strength. The content of the gel for GPC measurement is more preferably from 35 to 90%, further preferably from 41 to 90%, particularly preferably from 51 to 90%. If the GPC measurement gel content is less than 35%, good adhesive strength cannot be obtained.

Then, the non-contact coating for copolymer latex of the present invention, co in the polymer molecular weight distribution obtained from the measurement of GPC of Ingredients detected later than the elution time corresponding to 1 million molecular weight in terms of polystyrene Has a weight average molecular weight of 40,000 to 400,000. Therefore, it has excellent adhesive strength and good operability.
The weight average molecular weight of the component detected later than the elution time corresponding to 1,000,000 in terms of the molecular weight in terms of polystyrene is more preferably from 50,000 to 200,000, and if it is less than 40,000, good adhesive strength On the other hand, when the weight average molecular weight of such a component is greater than 400,000, good adhesion strength is obtained , but the viscosity of the obtained latex becomes too high, and the handling becomes difficult. And the practicality is reduced.
On the other hand, since the low molecular weight component is small, the mechanical stability is good, and the operability is improved because the tackiness is low. That is, in the case of curtain coating, the lip which is a discharge port of the coating material must not be closed, and in spray coating, the nozzle must not be clogged.

The copolymer latex for non-contact coating of the present invention has a toluene insoluble content of 35% by weight or more. It contributes to good dry strength and mechanical stability and low adhesiveness, and also has good solvent resistance, and therefore has good print gloss. The toluene-insoluble content is preferably from 35 to 95% by weight, more preferably from 60 to 95% by weight. If the toluene-insoluble content is less than 35% by weight , the dry strength decreases, the mechanical stability decreases, and the tackiness increases.
The content of the gel measured by GPC, the weight-average molecular weight of the above-mentioned components, and the toluene-insoluble content can be controlled by a polymerization temperature, a molecular weight regulator, and the polymerization recipe such as the amount and type of the initiator.

<Measurement of GPC>
In the present invention, GPC is measured under the following conditions.
1 . Preparation of Sample To 0.3 g of a copolymer latex having a solid content adjusted to 48% by weight, 1 g of water and about 1 g of a cation exchange resin washed and washed according to a conventional method are added to remove cations. Next, 50 ml of tetrahydrofuran is added and left to dissolve for 2 hours. Subsequently, the solution is filtered through a polytetrafluoroethylene membrane filter (pore size: 3 μm, manufactured by ADVANTEC), and the filtrate is used as a measurement sample.
2 . Apparatus and measurement conditions Measurement apparatus: HLC-8020 (manufactured by Tosoh Corporation)
Filler type, particle size: polystyrene gel 30 μm
GMH HR-H (30) (manufactured by Tosoh Corporation)
Column size: 7.8mm2D × 300mm
Solvent: tetrahydrofuran Sample concentration: 0.3% by weight
Injection volume: 30 μl
Flow rate: 1 ml / min Temperature: 40 ° C
Detector: Differential refractometer At the time of measurement, a calibration curve was prepared in advance using a polystyrene standard substance having a known molecular weight, and expressed as a polystyrene-converted molecular weight.
<Measurement of toluene insoluble content>
The toluene-insoluble content of the copolymer latex is measured as follows. After adjusting the copolymer latex to pH 8.0 and coagulating with isopropanol, the obtained solid is washed with methanol and dried. About 0.3 g of this solid content (total solid content A) was immersed in 100 ml of toluene at room temperature for 20 hours. The mixture was filtered using a bi-qualitative filter paper. A part (Cml) of the filtrate is accurately collected, evaporated and coagulated, and the obtained residual solid content (toluene soluble content B) is weighed, and the toluene insoluble content is determined by the following formula.
Toluene insolubles (% by weight) = {(AB × (100 / C)) / A} × 100 (%)

<Polymerization temperature>
The polymerization temperature range is preferably between 5 ° C and 80 ° C, more preferably between 20 ° C and 70 ° C, even more preferably between 20 ° C and 60 ° C. The copolymer latex obtained at a temperature in this range has a good balance between dry pick strength and stickiness as a binder for paper coating.

<Molecular weight regulator>
In the production process of the copolymer latex of the present invention, the molecular weight regulator used for the emulsion polymerization is not particularly limited, and specifically, n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl Mercaptans such as mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan, t-tetradecyl mercaptan, thioglycolic acid ; xanthogen disulfides such as dimethyl xanthogen disulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide ; tetramethylthiuram disulfide ; tetraethyl thiuram disulfide, thiuram sulfides such as tetrabutyl thiuram disulfide; chloroform, carbon tetrachloride, carbon tetrabromide, Ha such ethylene bromide Gen hydrocarbons; pentaphenylethane, hydrocarbons such as alpha-methylstyrene dimer; and acrolein, methacrolein, allyl alcohol, 2-ethylhexyl thioglycolate, terpinolene, alpha-Terunepin, .gamma. Terunepin, dipentene, 1 , 1-diphenylethylene and the like. These can be used alone or in combination of two or more. Of these, mercaptans, xanthogen disulfides, thiuram disulfides, 1,1-diphenylethylene, α-methylstyrene dimer and the like are more preferably used.
The amount of the molecular weight modifier to be used is preferably 0 to 20 parts by weight, more preferably 0.05 to 15 parts by weight, still more preferably 0.1 to 10 parts by weight, per 100 parts by weight of the total monomers. If the amount of the molecular weight modifier exceeds 20 parts by weight per 100 parts by weight of all monomers, the adhesive strength is undesirably reduced.
The method of adding the molecular weight modifier to the polymerization system may be any of batch addition, batch addition, continuous addition, and a combination thereof.

(Preparation of paper coating composition)
The copolymer latex of the present invention can be suitably used for a non-contact type paper coating composition.
The paper coating composition using the copolymer latex in the present invention, the inorganic latex or the organic pigment, the above copolymer latex, further optionally other
Various auxiliaries such as a binder , a water-soluble polymer and various additives are blended and used. The amount of the copolymer latex, preferably to 100 parts by weight pigment, 0.5 to 100 parts by weight (as solid content), more preferably 1 to 100 parts by weight, particularly preferably 1 to 30 parts by weight It is. When the blending amount of the copolymer latex is less than 0.5 part by weight, the adhesive strength decreases, while when it exceeds 100 parts by weight, the ink drying property decreases.
Further, as the inorganic pigment, for example, kaolin clay, barium sulfate, titanium oxide, calcium carbonate, satin white, talc, aluminum hydroxide, zinc oxide and the like can be used. Further, as the organic pigment, for example, polystyrene latex, urea formalin resin, or the like can be used. These can be used alone or in combination of two or more depending on the purpose.
As the other binder , for example, natural binders such as starch, oxidized starch, soybean protein, and casein, or synthetic latex such as polyvinyl alcohol, polyvinyl acetate latex, and acrylic latex can be used.
Further, various commonly used auxiliaries, such as dispersants (sodium pyrophosphate, sodium hexametaphosphate, etc.), defoamers (polyglycols, fatty acid esters, phosphate esters, silicone oils, etc.), leveling agents (roto oils, etc.) , Dicyanamide, urea, etc.), preservatives, water-resistant agents (formalin, hexamine, melamine resin, urea resin, glyoxal, etc.), release agents (calcium stearate, paraffin emulsion, etc.), fluorescent dyes, color retention improvers (carboxy) Methylcellulose, sodium alginate, etc.) can be added to the paper coating composition of the present invention as needed.

In the paper coating composition using the copolymer latex of the present invention, particularly the paper coating composition for offset printing paper, in addition to the above copolymer latex as a pigment adhesive, casein, casein modified , Starch, denatured starch, polyvinyl alcohol, carboxymethyl cellulose, and other water-soluble substances can be used in combination as needed.
In the paper coating composition using the copolymer latex of the present invention, various compounding agents generally used, for example, a water-resistant strength improver, a pigment dispersant, a viscosity modifier, a coloring pigment, a fluorescent dye, And a pH adjuster can be arbitrarily compounded.
Further, the copolymer latex of the present invention is suitably used as a binder for offset printing or gravure printing, but for applications other than offset printing or gravure printing, for example, various printing papers such as letterpress printing, and paper. Can be used as a coating agent.

(Examples 3 to 6)
A first-stage component shown in Table 1 was charged into a pressure-resistant reaction vessel equipped with a stirrer and a temperature controller, the inside of the polymerization system was replaced with nitrogen, and then the temperature in the polymerization system was raised to 50 ° C. 1/3 of the second-stage components and the aqueous reducing agent solution shown in Table 1 were continuously added into the polymerization system over 3 hours. Further, the third stage component shown in Table 1 and 1/3 of the aqueous reducing agent solution were continuously added into the polymerization system over 3 hours. Thereafter, in order to complete the polymerization, the remaining 1/3 amount of the aqueous reducing agent solution was continuously added over a further 5 hours to continue the polymerization. The final polymerization conversion was 98%.
About the obtained copolymer latex, pH adjustment and concentration were performed in the same manner as in Examples 1 and 2.
For each of the obtained copolymer latexes , the toluene-insoluble content, the content (%) of the gel measured by GPC described in Examples 1 and 2, and the weight average molecular weight of the component (X) were measured in the same manner as in Examples 1 and 2. I asked for it. These contents and weight average molecular weight were determined by the methods described above. Further, the particle diameter of each copolymer latex was measured in the same manner as in Examples 1 and 2. Table 3 shows the results.

(Comparative Example 1)
The first-stage components shown in Table 2 were charged into a pressure-resistant reaction vessel equipped with a stirrer and a temperature controller, the inside of the polymerization system was replaced with nitrogen, and then the temperature in the polymerization system was raised to 40 ° C. Polymerization was performed for 1 hour. Next, the second-stage components shown in Table 2 and 1/2 of the aqueous initiator solution were continuously added into the polymerization system over 7 hours. Thereafter, in order to complete the polymerization, the polymerization temperature was raised to 85 ° C., and the remaining 量 of the initiator aqueous solution was continuously added over 4 hours. The final polymerization conversion was 98%.
About the obtained copolymer latex, pH adjustment and concentration were performed in the same manner as in Examples 1 and 2.
For each of the obtained copolymer latexes , the content (%) of the toluene-insoluble component, the gel measured by GPC, and the weight average molecular weight of the component (X) were determined in the same manner as in Examples 1 and 2. These contents and weight average molecular weight were determined by the methods described above. Further, the particle diameter of each copolymer latex was measured in the same manner as in Examples 1 and 2.

(Comparative Examples 2 to 4)
The first-stage components shown in Table 2 were charged into a pressure-resistant reaction vessel equipped with a stirrer and a temperature controller, the inside of the polymerization system was replaced with nitrogen, and then the temperature in the polymerization system was raised to 50 ° C. , The second-stage components shown in Table 2 and 1/3 of the aqueous initiator solution were continuously added into the polymerization system over 5 hours. Further, the third stage component and 1/3 amount of the aqueous initiator solution shown in Table 2 were continuously added into the polymerization system over 5 hours. Thereafter, in order to complete the polymerization, the remaining 1/3 amount of the aqueous initiator solution was continuously added over 5 hours to continue the polymerization. The final polymerization conversion was 98%.
About the obtained copolymer latex, pH adjustment and concentration were performed in the same manner as in Examples 1 and 2.
For each of the obtained copolymer latexes , the content (%) of the toluene-insoluble component, the gel measured by GPC, and the weight average molecular weight of the component (X) were determined in the same manner as in Examples 1 and 2. These contents and weight average molecular weight were determined by the methods described above. Further, the particle diameter of each copolymer latex was measured in the same manner as in Examples 1 and 2. Table 3 shows the results.

Evaluation with curtain coater (preparation of paper coating composition)
Using the copolymer latexes produced in Examples 1 to 6 and Comparative Examples 1 to 4, a paper coating composition for curtain coating and offset printing paper was prepared according to the following formulation.
Formulation;
Kaolin clay 70.0 parts Calcium carbonate 30.0 parts Dispersant 0.2 parts Sodium hydroxide 0.1 parts Starch 4.0 parts Latex (as solid content) 13.0 parts Water so that the total solid content is 45% Add an appropriate amount to (preparation and evaluation of coated paper)
This paper coating composition is coated on a base paper to be coated with a lab curtain coater so that the coating amount is 10.0 ± 0.5 g / m ^{2 on} one side, and then heated with a hot air dryer at 150 ° C. Dry for 20 seconds. The obtained coated paper was allowed to stand in a room at a constant temperature and humidity of 23 ° C. and a humidity of 50% for 24 hours, and then passed four times through a super calender under the conditions of a linear pressure of 100 kg / cm 2 and a roll temperature of 50 ° C. The performance of the obtained coated paper was evaluated by the following method.
1) Dry pick strength The degree of picking when printed by an RI printing machine was visually judged and evaluated on a five-point scale. The lower the picking phenomenon, the higher the score. The numerical values are shown as an average value of six measurements.
2) Wet pick strength Using a RI printing machine, the surface of the coated paper was moistened with a water supply roll, and then the degree of picking when printing with the RI printing machine was visually judged, and evaluated on a five-point scale. The lower the picking phenomenon, the higher the score. The numerical values are shown as an average value of six measurements.
3) Printing Gloss The ink for offset was solid-coated using a RI printer, and measured at an incident reflection angle of 60 ° -60 ° using a Murakami gloss meter.
4) Operability The coating liquid was circulated for 1 hour through the head of the lab curtain coater. When the slit was closed during the circulation, x was given, when the slit was not closed, the flow from the slit, that is, when the coating liquid curtain was disturbed, was marked with Δ, and when there was no abnormality, O was marked.

Evaluation by spray coating The coating composition prepared for the curtain coater was diluted so that the viscosity became 100 mPa · s . The composition for paper coating was applied by spraying onto a base paper for coating so that the coating amount was 10.0 ± 0.5 g / m ^{2 on} one side. Thereafter, as in the case of the curtain coater, it was dried for 20 seconds by a hot air dryer at 150 ° C. The obtained coated paper was allowed to stand in a room at a constant temperature and humidity of 23 ° C. and a humidity of 50% for 24 hours, and then passed four times through a super calender under the conditions of a linear pressure of 100 kg / cm 2 and a roll temperature of 50 ° C.
The performance evaluation of the obtained coated paper was performed in the same manner as in the case of curtain coating. However, regarding the runnability was observed whether clogging does not occur during spraying, it can successfully sprayed.

Table 3 shows the results evaluated by the above evaluation method. As is clear from these, the copolymer latex of the example achieves the object of the present invention. That is, it has high strength and wet strength, good print gloss development, low latex tackiness, and good operability.
On the other hand, in the copolymer latex of the comparative example, any one of the strength, the wet strength, the print gloss, and the operability, or a plurality of items, was bad.

[0034]
【The invention's effect】
By using the non-contact coating composition of the present invention , the strength, which is a drawback of curtain coating and spray coating, is greatly improved, and water resistance, printing gloss is good, and operability during coating is improved. Also gives excellent coated paper.