JP2008231299A - Copolymer latex, paper coating agent and method for producing copolymer latex - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copolymer latex which can be used for preparing a paper coating agent exhibiting good balance of dry pick strength with the wet pick strength. <P>SOLUTION: The invention relates to the copolymer latex prepared by the emulsion polymerization of a polymerization stock liquid containing, as raw material monomers, component (a): aliphatic conjugated diene based monomer, component (b): ethylene based unsaturated carboxylic acid monomer, and component (c): a vinyl cyanide based monomer, and another monomer copolymerizable with the component (a), (b) or (c), and satisfying the formula (1): A/B≤0.8 (1). In the formula (1), A is a dissolving fraction (%) to water, of the fused body of the copolymer latex dried at 130°C, and B is a dissolving fraction (%) to water, of a fused material from the copolymer latex dried at 23°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a copolymer latex that can realize a paper coating agent having a good balance between dry pick strength and wet pick strength.

  A binder for paper coating that provides offset printing paper with excellent mixing stability as a binder, high-speed coating suitability and ink inking properties, as well as a balance between printing strength and blister resistance and excellent printing gloss, It is described in Patent Document 1. Further, Patent Document 2 discloses a paper coating binder that exhibits excellent effects on the water resistance and wetness of coated paper when ink is applied, as well as surface strength and printing gloss. Furthermore, Patent Document 3 discloses a binder for paper coating that can obtain a coated paper having excellent printability such as coating operability, surface strength, printing gloss, and ink drying property. .

JP 2001-192997 A Japanese Patent Laid-Open No. 08-034879 JP 2006-052365 A

  However, the binder for paper coating described in any of the above Patent Documents 1 to 3 still has room for improvement from the viewpoint of achieving various physical properties required for the coated paper in a balanced manner. .

  This invention is made | formed in view of the said situation, and makes it a subject to provide copolymer latex etc. which can implement | achieve the paper coating agent with the favorable balance of dry pick strength and wet pick strength.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have reduced the water soluble fraction of the copolymer latex in comparison with the water soluble fraction of the non-heated dry body. Such a copolymer latex has been found to be suitable for the purpose, and the present invention has been made based on this finding.

That is, the present invention provides the following copolymer latex and the like.
[1] As a raw material monomer,
(A) component: an aliphatic conjugated diene monomer,
(B) component: an ethylenically unsaturated carboxylic acid monomer;
(C) component: vinyl cyanide monomer,
Component (d): obtained by emulsion polymerization of a polymerization stock solution containing the above-described component (a), (b), or other monomer copolymerizable with component (c), and satisfies the following formula (1) Copolymer latex characterized by that.
A / B ≦ 0.8 (1)
(In the formula (1), A means the percentage dissolved in water (%) of the fused copolymer latex obtained by drying at 130 ° C., and B is dried at 23 ° C. (This is the percentage dissolved in water (%) of the fused copolymer latex obtained in this way.)
[2] The polymerization stock solution
(E) Component: The copolymer latex as described in [1] containing an amine compound.
[3] The copolymer latex according to [1] or [2], wherein the toluene insoluble fraction is 70% by mass or more.
[4] The copolymer latex according to [1], [2] or [3], which has a volume average particle diameter of 400 nm or less.
[5] A paper coating agent comprising the copolymer latex according to any one of [1] to [4].
[6] As a raw material monomer,
(A) component: an aliphatic conjugated diene monomer,
(B) component: an ethylenically unsaturated carboxylic acid monomer;
(C) component: vinyl cyanide monomer,
(D) component: In addition to (a), (b), or (c) other monomer copolymerizable with the component,
(E) Component: A method for producing a copolymer latex, wherein emulsion polymerization is carried out using a polymerization stock solution containing an amine compound.
[7] The production method according to [6], wherein the component (e) is blended in the course of the emulsion polymerization.
[8] A paper coating agent containing a copolymer latex obtained by the production method according to [6] or [7].

  The copolymer latex of the present invention can realize a paper coating agent having a good balance between dry pick strength and wet pick strength.

The best mode for carrying out the present invention (hereinafter, an embodiment of the present invention) will be described in detail below. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.
The copolymer latex in the present embodiment is suitably used as a pigment binder for coated paper and coated paperboard.

  Copolymer latex in the present embodiment is a fusion product obtained by drying the fusion product obtained by drying under a heating condition (130 ° C.) with a soluble fraction in water (ratio of soluble components). (Hereinafter, sometimes abbreviated as “heat-fused body”) and a fusion body obtained by drying under substantially non-heated conditions (23 ° C.) (hereinafter, abbreviated as “non-heat-fused body”). Is different). That is, in the copolymer latex of the present embodiment, a component that dissolves in water when a non-heated fused body is formed and does not dissolve in water when a heated fused body is formed. included.

That is, the copolymer latex of the present embodiment satisfies the following formula (1).
A / B ≦ 0.8 (1)
(In the formula (1), A means the percentage dissolved in water (%) of the fused copolymer latex obtained by drying at 130 ° C., and B is dried at 23 ° C. (This is the percentage dissolved in water (%) of the fused copolymer latex obtained in this way.)

Here, said A and B can be described using the following formulas (2) and (3).
A [%] = {(S1-W1) / S1} × 100 (2)
B [%] = {(S2-W2) / S2} × 100 (3)
(In the formulas (2) and (3), W1 means the water-insoluble weight [g] of the heat-bonded copolymer latex, and W2 is the water-insoluble content of the non-heated melt of the copolymer latex. In addition, S1 means the collected weight [g] of the heat-bonded copolymer latex, and S2 means the collected weight [g] of the non-heated melt of the copolymer latex. means.)

In addition, as a specific method of measuring the above A, a method of measuring through the following steps (p) to (u) can be employed.
(P) Process: The copolymer latex dispersion adjusted so that the solid content concentration in a dispersion medium (for example, water) may be about 45 mass% to 55 mass% is adjusted to pH8. The copolymer latex dispersion is dropped onto a Teflon (registered trademark) sheet using a dropper to form a droplet having a diameter of about 3 mm.
Step (q): The droplets produced in the step (p) are dried in a hot air drier at 130 ° C. for 30 minutes to produce a dried film (heated fusion product).
(R) Step: About 0.5 g is collected from the heat-fused body prepared in the step (q) and precisely weighed (measurement of S1).
Step (s): The heat-fused body precisely weighed in the step (r) is placed in a sample bottle of about 50 ml, 30 ml of distilled water is added thereto, and the mixture is shaken with a shaker for 3 hours.
(T) Process: The content liquid of the sample bottle shaken for 3 hours at the said (s) process is filtered with a 325 mesh stainless steel sieve, and a water-insoluble content and water are isolate | separated.
Step (u): The water-insoluble matter separated in the step (t) is dried in a hot air dryer at 130 ° C. for 1 hour, and the water-insoluble matter weight (W1) of the heat-fused product is precisely weighed. The dissolved fraction (A [%]) of the heat-fused body in water is obtained from the above equation (2).

  As a specific method for measuring B, the same method as A can be used. In this case, instead of “drying in a hot air dryer at 130 ° C. for 30 minutes” in the step (q), “drying for 48 hours in a constant temperature and humidity environment of 23 ° C. and 50% RH” is performed as an unheated fusion body. Should be created. Thereafter, S2 and W2 are measured in the same manner as described above, and the water-insoluble weight (W2) of the non-heated fusion product is precisely weighed. The dissolution fraction (B [%]) of the non-heated fusion product in water is obtained from the above equation (3).

In the present embodiment, the A / B value is 0.8 or less, preferably 0.75 or less, preferably 0.01 or more, more preferably 0.1 or more. A copolymer latex having such an A / B value can realize a paper coating agent having excellent white paper gloss, printing gloss, dry pick strength, or wet pick strength. Further, such a paper coating agent can be a good paper coating agent with respect to water retention as a coating material and high-speed coating suitability when producing coated paper and coated paperboard.
The A / B value can be adjusted by methods such as adjustment of the monomer composition, adjustment of the molecular weight / toluene insoluble content, adjustment by a polymerization method, and the like.

About the copolymer latex of this Embodiment, as a toluene insoluble fraction, Preferably it is 70 mass% or more, More preferably, it is 80 mass% or more, Preferably it is 99 mass% or less, More preferably, it is 98 mass% or less. It is. By adjusting the toluene insoluble content in such a range, a copolymer latex excellent in dry pick strength and wet pick strength can be realized.
As a method for measuring the toluene-insoluble fraction, first, a heat-fused body is prepared in the same manner as in the steps (p) and (q). Next, this heat-fused body (about 0.5 g: precisely weighed) is put into toluene (30 ml), shaken for 3 hours, and then filtered through a 325 mesh wire mesh. Thereafter, in the same manner as in the above step (u), the weight of toluene-insoluble matter in the heat-fused product is precisely weighed, and the mass% with respect to the weight of the latex dry film collected first is obtained.
Toluene-insoluble fraction (%) = {(Toluene-insoluble fraction weight) / (Collected weight of heat-fused product)} × 100
As a method for adjusting the toluene insoluble fraction, a method for increasing or decreasing the amount of the chain transfer agent used during the polymerization, a method for adjusting the reaction rate during the polymerization, and the like can be adopted.

Moreover, about the copolymer latex of this Embodiment, As the volume average particle diameter, Preferably it is 40-400 nm, More preferably, it is 50-200 nm, More preferably, it is 50-110 nm. By adjusting the volume average particle diameter to such a range, a copolymer latex excellent in dry pick strength, wet pick strength, and water retention of paint can be realized. In particular, when the volume average particle diameter is 110 nm or less, these characteristics are remarkably improved.
Examples of the method for measuring the volume average particle diameter include a method of measuring using MICROTRAC UPA150 manufactured by MOUNTECH.
In addition, about the method of adjusting a volume average particle diameter, the method of adjusting the quantity of an emulsifier, the method of adjusting superposition | polymerization solid content, the method of adjusting the initial usage-amount of a polymerization initiator, etc. can be employ | adopted.

The copolymer latex of the present embodiment is a raw material monomer,
(A) component: an aliphatic conjugated diene monomer,
(B) component: an ethylenically unsaturated carboxylic acid monomer;
(C) component: vinyl cyanide monomer,
Component (d): A copolymer latex obtained by emulsion polymerization of a polymerization stock solution containing the monomer (a), (b), or other monomer copolymerizable with the component (c).

The component (a) is an important component from the viewpoint of imparting flexibility to the resulting copolymer latex and imparting adhesive strength and impact absorption.
The proportion of the component (a) in the total amount of all raw material monomers used throughout this embodiment (hereinafter sometimes abbreviated as “total raw material monomer amount”) is usually 10 to 10. 60% by mass, preferably 25 to 50% by mass. By setting the ratio to 10% by mass or more, it is possible to reduce the risk that the copolymer becomes hard and brittle and the adhesive strength is reduced. On the other hand, by setting the amount to 60% by mass or less, it is possible to reduce the possibility that the copolymer becomes too soft and the adhesive strength and stickiness resistance are lowered.
Specific examples of the component (a) include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene and the like. These can be used alone or in combination of two or more.

The component (b) is an important component from the viewpoint of imparting dispersion stability to the obtained copolymer latex and enhancing the adhesive force.
The proportion of the component (b) in the total amount of raw material monomers is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass. By setting the ratio to 0.5% by mass or more, the dispersion stability necessary for the copolymer latex can be provided. If the dispersion stability is low, various problems may occur when mixing the pigment and in the coating process. On the other hand, by setting it as 10 mass% or less, the possibility that the viscosity of the copolymer may become too high or the water resistance may be reduced can be reduced.
Specific examples of the component (b) include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and the like. These can be used alone or in combination of two or more.

The component (c) is an important component from the viewpoint of imparting polarity to the copolymer latex, increasing the adhesive strength, and controlling the water-insoluble content.
The proportion of the component (c) in the total amount of raw material monomers is preferably 8 to 35% by mass, more preferably 12 to 30% by mass, and still more preferably 15 to 28% by mass. By making the said ratio 8 masses or more, the fall of dry pick strength and wet pick strength can be prevented. On the other hand, by setting it as 35 mass% or less, the fall of dry pick strength and wet pick strength, and the fall of polymerization stability can be prevented.
Specific examples of the component (c) include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and the like. These can be used alone or in combination of two or more.

The component (d) can impart various properties to the resulting copolymer latex.
Specific examples of the component (d) include aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and p-methylstyrene;
(Meth) acrylic acid alkyl ester monomers such as methyl methacrylate (methyl methacrylate), butyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate;
(Meth) acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl acrylate (hydroxyethyl acrylate) and 2-hydroxyethyl methacrylate;
Aminoalkyl acrylates such as aminoethyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate;
(Meth) acrylic acid glycidyl esters such as glycidyl acrylate and glycidyl methacrylate;
Amides such as acrylamide, methacrylamide, N-methylolacrylamide, N-methylacrylamide, N-methylmethacrylamide, glycidylmethacrylamide, N, N-butoxymethylacrylamide;
Pyridines such as 2-vinylpyridine and 4-vinylpyridine;
Carboxylic acid vinyl esters such as vinyl acetate;
Vinyl halides such as vinyl chloride;
Etc. These can be used alone or in combination of two or more.

The polymerization stock solution further comprises:
(E) Component: An amine compound can be included. Use of such a component (e) is particularly suitable as a method for producing the copolymer latex of the present embodiment having the A / B value described above.

  Here, as a compounding quantity of the said (e) component, Preferably it is 0.1-1.0 mass part as a compounding quantity with respect to 100 mass parts of said raw material monomer total amount, More preferably, it is 0.2-0.7. Part by mass. By making the said compounding quantity 0.1 mass part or more, the effect of invention can be expressed more largely. On the other hand, by setting the amount to 1.0 part by mass or less, it is possible to prevent problems such as insufficient polymerization stability or excessive increase in paint viscosity.

Specific examples of the component (e) include ammonium hydroxide;
A primary amine compound represented by R—NH ₂ (where R is a C1-C21 alkyl or alkenyl group);
A secondary amine compound represented by R—NH—R ′ (wherein R and R ′ are each a C1-C21 alkyl or alkenyl group);
A tertiary amine compound represented by R—NR′—R ″ (R, R ′, R ″ are C1 to C21 alkyl or alkenyl groups);
An amine compound having a plurality of primary to tertiary amino groups in one molecule;
An amine polymer or an amine oligomer produced by polymerizing an amine monomer;
Etc. These can be used alone or in combination of two or more.

Examples of the primary amine compound include methylamine, ethylamine, isopropylamine, t-butylamine, propylamine, butylamine, cyclohexylamine, n-hexylamine, t-dodecylamine and the like.
Examples of the secondary amine compound include dimethylamine, diethylamine, diisopropylamine, di-t-butylamine, dipropylamine, dibutylamine, dicyclohexylamine, di-n-hexylamine, di-t-dodecylamine and the like.
Examples of the tertiary amine compound include trimethylamine, triethylamine, triisopropylamine, tri-t-butylamine, tripropylamine, tributylamine, tricyclohexylamine, tri-n-hexylamine, tri-t-dodecylamine and the like.

Examples of amine compounds having a plurality of amino groups in one molecule include 3-aminomethyl-3,5,5-trimethylcyclohexylamine, ethylenediamine, diethylenetriamine, triethylenetetraamine, and the like.
In the present embodiment, an amine compound having a plurality of primary to tertiary amino groups in one molecule, particularly 3-aminomethyl-3, 5,5-trimethylcyclohexylamine is preferably used.

  In the present embodiment, when the component (e) is blended, it may be blended with various monomers before the emulsion polymerization is started, or polymerization of various monomers. May be blended in a polymerization reaction system formed by starting or after the polymerization reaction is completed. Especially, it is suitable from a viewpoint of the production | generation control of the water-soluble component in superposition | polymerization to mix | blend the said (e) component in the middle of progress of emulsion polymerization (it mix | blends with a polymerization reaction system).

Here, when the component (e) is blended during the emulsion polymerization, it is preferable to add the component (e) together with the component (b) to the polymerization reaction system.
Conventionally, when a copolymer latex is produced by emulsion polymerization using water as a polymerization medium, an ethylenically unsaturated carboxylic acid is often used as a part of the raw material monomer. Here, when such a carboxylic acid and an amine compound coexist, the reaction of the carboxylic acid is usually delayed and the polymerization stability is lowered. When producing a copolymer latex, it is desirable to carry out the polymerization without using a substance that raises the pH of the polymerization system from the viewpoint of obtaining a stable copolymer latex. That is, using water as a polymerization medium and using the component (e) in combination with a polymerization reaction system containing an ethylenically unsaturated carboxylic acid in the raw material monomer has been an obstacle for those skilled in the art. .
However, in the present embodiment, in addition to the components (a) to (d) as raw material monomers, the component (e) is blended as an additive. By doing so, it is possible to satisfactorily produce a copolymer latex that satisfies the above formula (1), and thus, for example, a balance of printing gloss, white paper gloss, dry pick strength, wet pick strength, water retention, and high-speed coating suitability. Can realize a good paper coating agent.

Moreover, as said (b) component suitable to use together with said (e) component, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, etc. are mentioned, for example.
More preferable combinations of the component (e) and the component (b) include, for example, one or more selected from the group consisting of itaconic acid, fumaric acid, acrylic acid, and methacrylic acid, and one molecule. Examples thereof include combinations with amine compounds having a plurality of primary to tertiary amino groups. Among them, a combination of itaconic acid and fumaric acid and an amine compound having a plurality of primary to tertiary amino groups in one molecule, itaconic acid and acrylic acid and primary to tertiary amino groups in one molecule. A combination of a plurality of amine compounds, a combination of itaconic acid and methacrylic acid and an amine compound having a plurality of primary to tertiary amino groups in one molecule, or a primary combination of itaconic acid and one molecule. A combination with an amine compound having a plurality of ˜tertiary amino groups is preferred. As the amine compound having a plurality of primary to tertiary amino groups in one molecule, it is particularly preferable to use 3-aminomethyl-3,5,5-trimethylcyclohexylamine.

  As a method of emulsion polymerization in the present embodiment, a method of performing polymerization with a polymerization initiator in the presence of a surfactant in an aqueous medium can be used. In addition, it is preferable to use a multistage polymerization method and blend the carboxylic acid component in the latter half of the polymerization from the viewpoints of reducing latex viscosity, suitability for high-speed coating, and wet pick strength.

Moreover, as an emulsifier (surfactant) used in such emulsion polymerization, anionic, cationic, amphoteric and nonionic surfactants can be used.
Examples of such surfactants include aliphatic soaps, rosin acid soaps, alkyl sulfonates, dialkyl allyl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, and polyoxyethylene alkyl allyl sulfates. Anionic surfactants of
Nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethyleneoxypropylene block copolymer;
Etc. These can be used alone or in combination of two or more.

As the polymerization initiator, those that undergo radical decomposition in the presence of heat or a reducing agent to initiate addition polymerization of monomers can be used, and both inorganic initiators and organic initiators are used. It is possible.
Examples of such a polymerization initiator include peroxodisulfate, peroxide, azobis compound and the like. More specifically, for example, potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisbutyronitrile, cumene hydroperoxide , Etc.
In addition, POLYMER HANDBOOK (3rd edition), J.A. Brandrup and E.I. H. A compound described in Immersut, published by John Willy & Sons (1989) can be used as a polymerization initiator.
In addition, a so-called redox polymerization method in which a reducing agent such as acidic sodium sulfite, ascorbic acid or a salt thereof, erythorbic acid or a salt thereof or Rongalite is used in combination with a polymerization initiator can also be used.
These polymerization initiators can be used alone or in combination of two or more.

In the present embodiment, a chain transfer agent can be used when emulsion polymerization is performed.
As such a chain transfer agent, for example, α-methylstyrene dimer which is one of dimers of nucleus-substituted α-methylstyrene;
mercaptans such as n-butyl mercaptan, t-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan;
Disulfides such as tetramethylthiudium disulfide, tetraethylthiudium disulfide;
Halogenated derivatives such as carbon tetrachloride and carbon tetrabromide;
2-ethylhexyl thioglycolate, etc. are mentioned. These can be used alone or in combination of two or more.
In addition, there is no restriction | limiting in particular in the addition method of these chain transfer agents, Well-known addition methods, such as lump addition, batch addition, and continuous addition, are used.

  In the present embodiment, a so-called “seed polymerization method” can be used. A method such as an internal seed method in which the copolymer latex is polymerized in the same reaction system after the seed is produced, or an external seed method using a separately produced seed can be appropriately selected and used.

  Furthermore, in this Embodiment, various polymerization regulators can be used as needed. Examples of such polymerization regulators include pH regulators and chelating agents. Preferable examples of the pH adjuster include sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium hydrogen carbonate, disodium hydrogen phosphate, amines and the like. Preferable examples of the chelating agent include sodium ethylenediaminetetraacetate.

When the copolymer latex of the present embodiment is dispersed in a dispersion medium, the solid content concentration is not particularly limited, but is preferably 30 to 60% by mass.
Moreover, as polymerization temperature in the manufacturing method of this Embodiment, Preferably it is 5-100 degreeC, More preferably, it is 40-90 degreeC, More preferably, it is 50 degreeC-85 degreeC.
Furthermore, in the present embodiment, the effect of the invention can be expressed more greatly by keeping the temperature in the first half of the polymerization low and increasing the temperature in the second half. The polymerization temperature in the first half of the polymerization is preferably 70 ° C. or lower, more preferably 65 ° C. or lower. The polymerization temperature in the latter half of the polymerization is preferably 80 ° C. or higher, more preferably 85 ° C. or higher.
Various additives can be added to the copolymer latex of the present embodiment as necessary. Examples of such additives include dispersants, antifoaming agents, anti-aging agents, water-resistant agents, bactericides, and printability agents.

The paper coating agent of this embodiment is a paper coating agent containing a copolymer latex of this embodiment or a copolymer latex obtained by the production method of this embodiment (a coating material for paperboard coating). Included).
Here, as a method for adjusting the paper coating agent using the copolymer latex of the present embodiment as a binder, for example, in water in which a dispersant is dissolved, an inorganic pigment, an organic pigment, a water-soluble polymer, Add and mix the copolymer latex of this embodiment together with various additives such as thickeners, dyes, antifoaming agents, antiseptics, water resistance agents, lubricants, printability improvers, water retention agents, and the like. The method of using a dispersion liquid is mentioned.

As the inorganic pigment, for example, kaolin clay, calcium carbonate, titanium dioxide, aluminum hydroxide, satin white, talc and the like can be used. In addition, as the organic pigment, a plastic pigment, a binder pigment, or the like can be used. Furthermore, as the water-soluble polymer, starch, casein, polyvinyl alcohol, carboxymethyl cellulose and the like can be used.
In addition, the blending ratio of the pigment and the copolymer latex of the present embodiment can be appropriately determined depending on the purpose of use of the paper coating agent. In addition, as a compounding quantity of copolymer latex with respect to 100 mass parts of pigments, Preferably it is 3-30 mass parts.

  Such a paper coating agent 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. The coating form can also be applied to one side of the base paper, or both sides of the front and back, and the number of times of coating per side is so-called single coating that is one time, and so-called two coating steps. It can also be used for double coating. In this case, the copolymer latex of the present invention can be used for both the undercoat pigment composition (undercoat paper coating agent) and the overcoat pigment composition (overcoat paper coating agent).

  The paper coating agent using the copolymer latex of the present embodiment can be used for pigment coating of various paperboards such as coated paper, coated white balls, special paperboard, and high-quality paperboard. The coated paper coated with these paper coating agents is preferably used for various printing such as offset sheet-fed printing, gravure printing, letterpress printing, and UV printing.

  Next, the present embodiment will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to the following examples unless it exceeds the gist. In addition, about the physical property of copolymer latex, and the measurement and evaluation of the physical property of a paper coating agent using the same, it performed by the following method.

[Example 1]
A pressure-resistant reaction vessel equipped with a stirrer and a temperature control jacket was charged with 100 parts by mass of water, 0.3 parts by mass of sodium dodecylbenzenesulfonate and 0.45 parts by mass of sodium dodecyldiphenyl ether disulfonate, and the internal temperature was set to 65 ° C. The temperature rose. Subsequently, the mixed monomer composition (first-stage composition) of the first-stage monomer and chain transfer agent shown in Table 1 was added at a constant flow rate over 3 hours and 30 minutes. Ten minutes after the start of the first stage composition addition, a 30% aqueous solution of sodium peroxodisulfate (0.15 parts by mass) was added.
After the addition of the first-stage composition, a mixed monomer composition (second-stage composition) containing the second-stage monomer (excluding itaconic acid), a chain transfer agent, and an additive shown in Table 1 The product was added at a constant flow rate over 2 hours. Simultaneously with the start of the second stage composition addition, an initiator aqueous solution composed of 30 parts by mass of water and 0.6 parts by mass of sodium peroxodisulfate was added at a constant flow rate over 2 hours. Further, 30 minutes after the start of the second stage composition addition, a 15% aqueous solution of itaconic acid (2.5 parts by mass) shown in Table 1 was added at a constant flow rate over 1 hour. Regarding the polymerization temperature, the temperature was raised to 85 ° C. over 45 minutes simultaneously with the start of the second stage composition addition. Thereafter, the temperature was maintained at 85 ° C. for 1 hour and 15 minutes, and the temperature was raised to 95 ° C. at the same time as the addition of the second-stage composition was completed. The temperature was maintained for 1 hour and then cooled to complete the reaction.
Next, sodium hydroxide was added to the produced copolymer latex to adjust the pH to 8, unreacted monomers were removed by a steam stripping method, and the mixture was filtered through a 200 mesh wire net. This copolymer latex was finally adjusted to a solid content concentration of 50 mass% and pH 8. The copolymer latex thus obtained was designated as copolymer latex L-1.

[Example 2]
A copolymer latex L-2 was obtained in the same manner as in Example 1 except that the temperature increase temperature (85 ° C.) at the second stage in Example 1 was changed to 90 ° C.

[Example 3]
A copolymer latex L-3 was obtained in the same manner as in Example 1 except that the temperature increase temperature (85 ° C.) at the second stage in Example 1 was changed to 95 ° C.

[Example 4]
A pressure-resistant reaction vessel equipped with a stirrer and a temperature control jacket was charged with 115 parts by mass of water, 0.3 parts by mass of sodium dodecylbenzenesulfonate, and 0.45 parts by mass of sodium dodecyldiphenyl ether disulfonate, and the internal temperature was 65 ° C. The temperature rose. Subsequently, the mixed monomer composition (first-stage composition) of the first-stage monomer and chain transfer agent shown in Table 1 was added at a constant flow rate over 3 hours and 30 minutes. Ten minutes after the start of the first stage composition addition, a 30% aqueous solution of sodium peroxodisulfate (0.15 parts by mass) was added.
After the addition of the first-stage composition, the mixed monomer composition (second-stage composition) containing the second-stage monomer, chain transfer agent, and additive shown in Table 1 is taken for 2 hours. At a constant flow rate. After the addition of the second-stage composition, the third-stage monomer shown in Table 1 (itaconic acid was a 15% aqueous solution) was added at a constant rate over 1 hour. Simultaneously with the start of the third-stage monomer addition, an initiator aqueous solution composed of 15 parts by mass of water and 0.6 parts by mass of sodium peroxodisulfate was added at a constant flow rate over 1 hour. Regarding the polymerization temperature, the temperature was raised to 85 ° C. over 45 minutes from 1 hour and 15 minutes after the start of addition of the second-stage composition. Thereafter, the temperature was maintained at 85 ° C. for 1 hour, and then the temperature was raised to 95 ° C., and the temperature was maintained for 1 hour, followed by cooling to complete the reaction.
Next, sodium hydroxide was added to the produced copolymer latex to adjust the pH to 8, unreacted monomers were removed by a steam stripping method, and the mixture was filtered through a 200 mesh wire net. This copolymer latex was finally adjusted to a solid content concentration of 50 mass% and pH 8. The copolymer latex thus obtained was designated as copolymer latex L-4.

[Example 5]
In the same manner as in Example 4, the first-stage composition was charged into a pressure resistant reactor.
After the addition of the first-stage composition, a mixed monomer composition (second-stage composition) containing the second-stage monomer, chain transfer agent, and additive shown in Table 2 is taken over 2 hours. At a constant flow rate. After the addition of the second-stage composition, the third-stage monomer shown in Table 2 (itaconic acid was added in a 15% aqueous solution and acrylonitrile was added from a separate system) was added at a constant rate over 1 hour. Simultaneously with the start of the third-stage monomer addition, an initiator aqueous solution composed of 15 parts by mass of water and 0.6 parts by mass of sodium peroxodisulfate was added at a constant flow rate over 1 hour. Regarding the polymerization temperature, the temperature was raised to 85 ° C. over 45 minutes from 1 hour and 15 minutes after the start of addition of the second-stage composition. Thereafter, the temperature was maintained at 85 ° C. for 1 hour, and then the temperature was raised to 95 ° C., and the temperature was maintained for 1 hour, followed by cooling to complete the reaction.
Next, sodium hydroxide was added to the produced copolymer latex to adjust the pH to 8, unreacted monomers were removed by a steam stripping method, and the mixture was filtered through a 200 mesh wire net. This copolymer latex was finally adjusted to a solid content concentration of 50 mass% and pH 8. The copolymer latex thus obtained was designated as copolymer latex L-5.

[Example 6]
The composition of the first stage is further mixed with 1.0 part by weight of fumaric acid, and the amount of itaconic acid (2.5 parts by weight) blended in the composition of the second stage is reduced to 1.5 parts by weight. Copolymer latex L-6 was obtained in the same manner as in Example 1.

[Example 7]
In the second stage composition, 1.0 part by mass of acrylic acid is further blended, and the amount of itaconic acid (2.5 parts by mass) blended in the second stage composition is reduced to 2.0 parts by mass, Similarly, copolymer latex L-7 was obtained in the same manner as in Example 1 except that the amount of styrene (7.3 parts by mass) blended in the second-stage composition was reduced to 6.8 parts by mass.

[Example 8]
In the second stage composition, 1.0 part by mass of methacrylic acid is blended, and the amount of itaconic acid (2.5 parts by mass) blended in the second stage composition is reduced to 2.0 parts by mass. A copolymer latex L-8 was obtained in the same manner as in Example 1 except that the amount of styrene (7.3 parts by mass) blended in the second-stage composition was reduced to 6.8 parts by mass.

[Example 9]
In the second-stage composition, 0.5 part by mass of acrylic acid and 0.5 part by mass of methacrylic acid are blended, and the amount of itaconic acid (2.5 parts by mass) blended in the second-stage composition is 2 Copolymer in the same manner as in Example 1 except that the amount of styrene (7.3 parts by mass) blended in the second-stage composition was reduced to 6.8 parts by mass. Latex L-9 was obtained.

[Comparative Example 1]
In a pressure-resistant reaction vessel equipped with a stirrer and a temperature control jacket, 100 parts by mass of water, 0.3 parts by mass of sodium dodecylbenzenesulfonate, 0.45 parts by mass of sodium dodecyl diphenyl ether disulfonate, and 2.5 parts by mass of itaconic acid. The internal temperature was raised to 65 ° C. Subsequently, the mixed monomer composition (first-stage composition) of the first-stage monomer and the chain transfer agent shown in Table 3 was added at a constant flow rate over 3 hours and 30 minutes. Ten minutes after the start of the first stage composition addition, a 30% aqueous solution of sodium peroxodisulfate (0.15 parts by mass) was added.
After the addition of the first-stage composition, the mixed monomer composition (second-stage composition) containing the second-stage monomer and the chain transfer agent shown in Table 3 was fixed over 2 hours. Added at flow rate. Simultaneously with the start of the second stage composition addition, an initiator aqueous solution composed of 30 parts by mass of water and 0.6 parts by mass of sodium peroxodisulfate was added at a constant flow rate over 2 hours. Regarding the polymerization temperature, the temperature was raised to 85 ° C. over 45 minutes simultaneously with the start of the second stage composition addition. Thereafter, the temperature was maintained at 85 ° C. for 1 hour and 15 minutes, and the temperature was raised to 95 ° C. at the same time as the addition of the second-stage composition was completed. The temperature was maintained for 1 hour and then cooled to complete the reaction.
Next, sodium hydroxide was added to the produced copolymer latex to adjust the pH to 8, unreacted monomers were removed by a steam stripping method, and the mixture was filtered through a 200 mesh wire net. This copolymer latex was finally adjusted to a solid content concentration of 50 mass% and pH 8. The copolymer latex thus obtained was designated as copolymer latex L-10.

[Comparative Example 2]
In the same manner as in Comparative Example 1, the first-stage composition was charged into a pressure resistant reactor. Ten minutes after the start of the first stage composition addition, a 30% aqueous solution of sodium peroxodisulfate (0.6 parts by mass) was added.
After the addition of the first-stage composition, the mixed monomer composition (second-stage composition) containing the second-stage monomer and the chain transfer agent shown in Table 3 was fixed over 2 hours. Added at flow rate. Simultaneously with the start of the second stage composition addition, an initiator aqueous solution composed of 30 parts by mass of water and 0.15 parts by mass of sodium peroxodisulfate was added at a constant flow rate over 2 hours. The polymerization temperature and subsequent treatment were the same as in Comparative Example 1.
The copolymer latex thus obtained was designated as copolymer latex L-11.

[Comparative Example 3]
The first-stage composition was charged into a pressure resistant reactor in the same manner as in Comparative Example 1 except that itaconic acid was not used for the first-stage composition. Ten minutes after the start of the first stage composition addition, a 30% aqueous solution of sodium peroxodisulfate (0.15 parts by mass) was added.
After the addition of the first-stage composition, a mixed monomer composition (second-stage composition) containing the second-stage composition and the chain transfer agent shown in Table 3 is supplied at a constant flow rate over 2 hours. Added at. Simultaneously with the start of the second stage composition addition, an initiator aqueous solution consisting of 30 parts by mass of water and 0.6 parts by mass of sodium peroxodisulfate was added at a constant flow rate over 2 hours. Further, 30 minutes after the start of the second stage addition, a 15% aqueous solution of itaconic acid (parts by mass) shown in Table 3 was added at a constant flow rate over 1 hour. Further, 30 minutes after the start of the second stage addition, a 15% aqueous solution of itaconic acid (parts by mass) shown in Table 3 was added at a constant flow rate over 1 hour. The polymerization temperature was kept at 65 ° C. until the end of the second stage composition addition, and the temperature was raised to 95 ° C. after the end of the second stage composition addition. The temperature was maintained for 1 hour and then cooled to complete the reaction. It was. The subsequent processing was the same as in Comparative Example 1.
The copolymer latex thus obtained was designated as copolymer latex L-12.

[Comparative Example 4]
The first-stage composition was charged into a pressure resistant reactor in the same manner as in Comparative Example 1 except that itaconic acid was not used for the first-stage composition. Ten minutes after the start of the first stage composition addition, a 30% aqueous solution of sodium peroxodisulfate (0.15 parts by mass) was added.
After the addition of the first-stage composition, a mixed monomer composition (second-stage composition) containing the second-stage composition and the chain transfer agent shown in Table 3 is supplied at a constant flow rate over 2 hours. Added at. Simultaneously with the start of the second stage composition addition, an initiator aqueous solution consisting of 30 parts by mass of water and 0.6 parts by mass of sodium peroxodisulfate was added at a constant flow rate over 2 hours. Further, 30 minutes after the start of the second stage addition, a 15% aqueous solution of itaconic acid (parts by mass) shown in Table 3 was added at a constant flow rate over 1 hour. The polymerization temperature and subsequent treatment were the same as in Comparative Example 1.
The copolymer latex thus obtained was designated as copolymer latex L-13.

[Comparative Example 5]
Latex obtained in the same manner as in Example 4 except that no other additive (3-aminomethyl-3,5,5-trimethylcyclohexylamine) was used in the second stage mixed composition. Is copolymer latex L-14.

  Various physical properties of the obtained copolymer latexes L-1 to L-13 were evaluated. The results are shown in Tables 1-3.

[Volume average particle diameter]
It measured using MOUNTECH company make and MICROTRAC UPA150, and used the volume average value.

[Toluene insoluble fraction]
A copolymer latex sample (50% solid content) was adjusted to pH 8, and a latex film dried at 130 ° C. for 30 minutes was produced. This dry film (0.5 g: precise balance) was added to toluene (30 ml), shaken for 3 hours, filtered through a 325 mesh wire mesh, and the solid content remaining on the wire mesh was dried and collected first. The mass% based on the latex dry film weight was determined.
Toluene insoluble fraction (%) = {(toluene insoluble part weight) / (sample sampling weight)} × 100

[Water-soluble fraction of heat-fused product A [%]]
A method of measuring through the following steps (p) to (u) was adopted.
(P) Process: The copolymer latex dispersion adjusted so that the solid content concentration in a dispersion medium (for example, water) may be about 45 mass% to 55 mass% is adjusted to pH8. The copolymer latex dispersion is dropped onto a Teflon (registered trademark) sheet using a dropper to form a droplet having a diameter of about 3 mm.
Step (q): The droplets produced in the step (p) are dried in a hot air drier at 130 ° C. for 30 minutes to produce a dried film (heated fusion product).
(R) Step: About 0.5 g is collected from the heat-fused body prepared in the step (q) and precisely weighed (measurement of S1).
Step (s): The heat-fused body precisely weighed in the step (r) is placed in a sample bottle of about 50 ml, 30 ml of distilled water is added thereto, and the mixture is shaken with a shaker for 3 hours.
(T) Process: The content liquid of the sample bottle shaken for 3 hours at the said (s) process is filtered with a 325 mesh stainless steel sieve, and a water-insoluble content and water are isolate | separated.
Step (u): The water-insoluble matter separated in the step (t) is dried in a hot air dryer at 130 ° C. for 1 hour, and the water-insoluble matter weight (W1) of the heat-fused product is precisely weighed. The dissolved fraction (A [%]) of the heat-fused product in water is obtained from the following formula (2).
A [%] = {(S1-W1) / S1} × 100 (2)

[Water-soluble fraction of non-heated fusion product B [%]]
The same method as that for measuring A [%] was used. In this case, instead of “drying in a hot air dryer at 130 ° C. for 30 minutes” in the step (q), “drying for 48 hours in a constant temperature and humidity environment of 23 ° C. and 50% RH” is performed as an unheated fusion body. It was created. Thereafter, S2 and W2 were measured in the same manner as described above, and the fraction dissolved in water (B [%]) of the non-heated fusion product was obtained from the following formula (3).
B [%] = {(S2-W2) / S2} × 100 (3)

[Examples 10 to 18, Comparative Examples 6 to 10]
Using the copolymer latexes L-1 to L-13, paints were prepared according to the formulation shown in Table 4. Furthermore, coated paper was prepared under the conditions shown in Table 5 using the obtained paint. That is, as a coating method, a sheet-type coating machine (manufactured by SMT, trade name: sheet-type coater PM-9040MC1 type) was used, and the coating methods (bar applicator, blade scraping) shown in Table 5 were applied. The speed, drying temperature, drying air volume, and drying time were used. The coated paper after coating was left to stand in a constant temperature and humidity environment of 25 ° C./50% for 12 hours or more to adjust the humidity. After humidity control, supercalender treatment was performed under the conditions of 50 ° C., 150 kg / cm, and 10 m / min.
Various properties of the coated paper obtained were evaluated (all were evaluated in a constant temperature and humidity environment of 25 ° C./50%). The results are shown in Tables 6 and 7.

First grade clay: made by Thiele Kaolin, trade name: Khao Fine Heavy calcium carbonate: made by IMERYS MINALLS JAPAN, trade name: Carbital 97
Dispersant: manufactured by Toagosei Co., Ltd., trade name: Aron A-20U
Starch: Oji Cornstarch Co., Ltd., trade name: Oji Ace C

[Blank gloss]
The 75 ° -75 ° reflected light of the coated paper subjected to the supercalender treatment was measured using a Gloss SS METER MODEL GM-26D manufactured by Murakami Color Research Laboratory.

[Print gloss (single color)]
After thoroughly kneading 0.4 ml of indigo ink between rolls of an RI printing machine (Made Seisakusho Co., Ltd., trade name: RI printing machine) until uniform, it is printed (once = single color), and then 23 ° C / It was dried for 24 hours under a constant temperature and humidity condition of 50%. After drying, 60 ° -60 ° reflected light was measured using GROSS METER MODELGM-26D manufactured by Murakami Color Research Laboratory.

[Print gloss (heavy color)]
No. of RI printer No. 2 (numerical value means which color is printed on a four-color printer) and 0.4 ml of indigo ink No. 0.4 ml of red ink was kneaded with a roll No. 4 until uniform, printed in the order of indigo → red, and then dried for 24 hours under a constant temperature and humidity condition of 23 ° C./50%. After drying, 60 ° -60 ° reflected light was measured using GROSS METER MODELGM-26D manufactured by Murakami Color Research Laboratory.

[Dry pick strength]
First, 0.4 ml of special black ink (tack value 10-20, selected as appropriate) is kneaded between the rolls of the RI printer until it becomes uniform, and printing is performed several times until the coated layer of the coated paper sample picks. Repeated. After printing, the ink roll was copied onto a coated paperboard. The pick strength was visually evaluated based on the degree of white spots on the coated paperboard. In this case, the evaluation is divided into 41 steps in increments of 0.1 from 1.0 to 5.0, where 5.0 is a state where no white spots are present, and 1.0 is a case where the entire surface is white. evaluated.

[Wet pick strength]
First, the RI printer No. In 4 rolls, 0.4 ml of special ink (tack value 10 to 20; appropriately selected) is kneaded until uniform. A sleeve roll moistened with water was installed in two rolls, and the ink roll was passed after passing through the sleeve roll. The ink roll after printing was copied to a coated paperboard and evaluated by the same method as the dry strength.

[Water retention of paint]
In a constant temperature and humidity environment of 25 ° C / 50% for each paint, KALTEC SCIENTIFIC. INC. The measurement was performed using AA-GWR manufactured by the company. The measurement conditions were a 150 kPa / 30 second, 0.2 μm pore membrane filter.

[High speed coating suitability (high shear viscosity)]
Using Tani Riki Kogyo Co., Ltd./HI-SHEAR VISCOMETER / HERCULES TYPE MODEL / HR-801C, using F Bob, increasing from 0 rpm to 8800 rpm or 4400 rpm in 10 seconds, and then reducing to 0 rpm in 10 seconds Measured with a program.

  From the results in the above table, the copolymer latex of this embodiment realizes a paper coating agent with a good balance of printing gloss, white paper gloss, dry pick strength, wet pick strength, water retention, and high-speed coating suitability. Can do.

  The composition of the present invention can be suitably used in the field of paper coating.

Claims (8)

As raw material monomer,
(A) component: an aliphatic conjugated diene monomer,
(B) component: an ethylenically unsaturated carboxylic acid monomer;
(C) component: vinyl cyanide monomer,
Component (d): obtained by emulsion polymerization of a polymerization stock solution containing the above-described component (a), (b), or other monomer copolymerizable with component (c), and satisfies the following formula (1) Copolymer latex characterized by that.
A / B ≦ 0.8 (1)
(In the formula (1), A means the percentage dissolved in water (%) of the fused copolymer latex obtained by drying at 130 ° C., and B is dried at 23 ° C. (This is the percentage dissolved in water (%) of the fused copolymer latex obtained in this way.) The polymerization stock solution is
(E) Component: The copolymer latex of Claim 1 containing an amine compound.   The copolymer latex according to claim 1 or 2, wherein the toluene insoluble fraction is 70% by mass or more.   The copolymer latex according to claim 1, 2 or 3, having a volume average particle diameter of 400 nm or less.   The paper coating agent containing the copolymer latex in any one of Claims 1-4. As raw material monomer,
(A) component: an aliphatic conjugated diene monomer,
(B) component: an ethylenically unsaturated carboxylic acid monomer;
(C) component: vinyl cyanide monomer,
(D) component: In addition to (a), (b), or (c) other monomer copolymerizable with the component,
(E) Component: A method for producing a copolymer latex, wherein emulsion polymerization is carried out using a polymerization stock solution containing an amine compound.   The manufacturing method of Claim 6 with which the said (e) component is mix | blended in the progress of the said emulsion polymerization.   The paper coating agent containing the copolymer latex obtained by the manufacturing method of Claim 6 or 7.