JP2001064444A - Copolymer latex for coating of moisture-proof paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a moisture-proof coated paper excellent in moisture-proofing property and defibrability and a copolymer latex used in production of the coated paper and a composition for coating for moisture-proof paper including the copolymer latex and a pigment. SOLUTION: In the production of the coated paper a copolymer latex obtained by polymerizing monomers comprising 25-70 wt.% of an aliphatic conjugated diene monomer, 20-70 wt.% of an aromatic vinyl monomer, 1-35 wt.% of an ethylenically unsaturated acid monomer and 0-50 wt.% of an ethylenically unsaturated monomer copolymerizable with these monomers in an aqueous medium and the copolymer has tetrahydrofuran insoluble part >=60 wt.%, glass transition temperature of -10 to 50 deg.C and the particle size of the latex of 50 to 300 nm and film formed from the latex has weight loss rate <=5%, is used. A composition for coating for moisture-proof paper including the copolymer latex and a pigment, and a moisture-proof paper obtained by coating the composition for coating for moisture-proof paper are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a moisture-proof paper coating copolymer latex, a moisture-proof paper coating composition using the same, and a moisture-proof paper coating composition. It relates to a moisture-proof coated paper. More specifically, a moisture-proof paper coating copolymer latex having a high balance of moisture-proof properties and easy disaggregation properties, a moisture-proof paper coating composition and a moisture-proof paper coating composition using the same. The present invention relates to a moisture-proof coated paper that has been engineered.

[0002]

2. Description of the Related Art Newspaper base paper, copy paper, and the like tend to absorb external moisture, thereby deteriorating the quality of products. To prevent this, wrapping paper is used. When a normal coated paper is used as the wrapping paper, the moisture inside the wrapper passes through, so that the product in the wrapping absorbs moisture and sags.
When printing or copying is performed using the newspaper base paper or the copy paper, a printing trouble or a reduction in product appearance is caused. Therefore,
Usually, moisture-proof paper is used for the purpose of shielding the internal product from external moisture. The moisture-proof paper can be obtained by applying a moisture-proof agent comprising a wax having a high moisture-proof property and a copolymer latex as a binder to the base paper surface. The degree of moisture resistance is determined by the type and amount of wax used. However, if the amount of wax used is increased to improve the moisture resistance, the problem of turbulence when winding the coated paper and the slipping of the product roll and loading during the loading and unloading of the coated paper often occur. Causes collapse problems. for that reason,
For the problem of turbulence at the time of winding the coated paper, for example, to provide a non-slip layer on the back surface not coated with a moisture barrier,
A method such as winding in a roll with a specific winding pressure is performed. In addition, to prevent slippage or collapse of the product roll when loading and unloading the rolled coated paper, a method of fixing the roll so that it does not move with a wire and moving it carefully over time is also required. Is being done. However, even if winding, carrying in and carrying out of the moisture-proof paper are performed using these methods, a sufficient effect has not been obtained.

[0003] Furthermore, moisture-proof paper coated with a moisture-proofing agent containing a large amount of wax has a problem that it is difficult to disintegrate when it is collected as used paper and subjected to a disintegration process. This occurs because wax in the desiccant prevents water from penetrating into the moisture-proof paper. If water is prevented from penetrating into the moisture-proof paper, the bonding strength between the fibers of the base paper does not decrease and the entanglement of single fibers is not eliminated. As a result, the moisture-proof paper coated with a moisture-proofing agent containing a large amount of wax does not easily disintegrate in the disintegration step, but exists in a large sheet form in the disintegration liquid. Therefore, only recycled paper containing many undisintegrated substances can be obtained. For this reason, moisture-proof paper is considered to be unsuitable as a raw material for recycled paper, and even when collected, it is often used as it is as industrial waste and is often incinerated.

However, in recent years, problems of resource saving, environmental pollution, and reduction of industrial waste have been taken up, and it has become necessary to reuse moisture-proof paper that has been conventionally discarded or incinerated. Along with this, improvement in the disintegration of moisture-proof paper has been required. In response to this demand for improved disintegration,
A method using a wax having an excellent disintegration property and a method using a moisture-proof material other than the wax are being studied.

[0005] As a method of producing using a wax having a good disintegration property, for example, a method of applying an emulsion containing a paraffin wax having a specific composition onto base paper (Japanese Patent Laid-Open No.
0-36611). However, with this method, although the disintegration property is better than before, it has not been sufficient yet. Furthermore, the moisture resistance is inferior to the conventional one, and a method such as increasing the amount of paraffin wax is required.

On the other hand, as a method of using a substance having a moisture-proof property other than wax, for example, a method of using a propylene-based polymer having a specific structure (JP-A-6-33049)
No. 7) and a method using a stearic acid ester (Japanese Patent Application Laid-Open No. 8-144192). However, even with these methods, the disintegration property is still insufficient, and many undisintegrated substances are present in the recycled paper. Furthermore, the moisture resistance is inferior to the conventional one, and the use ratio of substances having moisture resistance is increased,
It is necessary to use a method such as increasing the amount of application.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a moisture-proof coated paper having excellent moisture-proof and pulverizing properties, a copolymer latex for coating a moisture-proof paper used in the production of such a coated paper, and a copolymer latex thereof. An object of the present invention is to provide a moisture-proof paper coating composition containing a polymer latex and a pigment.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have found that the above object can be achieved by using a specific copolymer latex. Based on this finding, the present invention has been completed.

Thus, according to the present invention, 25 to 70% by weight of an aliphatic conjugated diene monomer, 15 to 70% by weight of an aromatic vinyl monomer, and 1 to 35% of an ethylenically unsaturated acid monomer.
Latex of a copolymer obtained by polymerizing a monomer consisting of 0 to 50% by weight and other ethylenically unsaturated monomers copolymerizable therewith in an aqueous medium,
The copolymer has a tetrahydrofuran insoluble content of 60% by weight or more, a glass transition temperature of -10 to 50 ° C, a particle size of the copolymer latex of 50 to 300 nm, and a weight loss rate of a film on which the latex is formed. Is less than or equal to 5% by weight.

Further, according to the present invention, there is provided a moisture-proof paper coating composition containing a copolymer latex for coating a moisture-proof paper and a pigment, and a moisture-proof paper coated with the composition. Is done.

Hereinafter, the present invention will be described in detail. The copolymer latex of the present invention comprises 25 to 70% by weight of an aliphatic conjugated diene monomer and 15 to 70% by weight of an aromatic vinyl monomer.
% By weight, a monomer comprising 1 to 35% by weight of an ethylenically unsaturated acid monomer and 0 to 50% by weight of another ethylenically unsaturated monomer copolymerizable therewith is polymerized in an aqueous medium. A latex of the copolymer obtained by the method, wherein the tetrahydrofuran-insoluble content of the copolymer is 60% by weight or more, the glass transition temperature is -10 to 50 ° C, and the particle size of the copolymer latex is 50 to 300 nm; Further, the film on which the latex is formed has a weight loss rate of 5% by weight or less.

The aliphatic conjugated diene monomer used in the production of the copolymer latex of the present invention is not particularly limited.
For example, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, chloroprene, and the like can be given. These can be used alone or in combination of two or more. Among these aliphatic conjugated diene monomers, 1,3-butadiene is preferred.

The amount of the aliphatic conjugated diene monomer used is 25 to 70% by weight, preferably 25 to 65% by weight of the total monomers. If the content is less than 25% by weight, the resulting copolymer latex becomes difficult to form a film, and the moisture-proof property is reduced. If it exceeds 70% by weight, the coating film of the copolymer becomes soft, and the adhesive strength becomes too strong, so that the disintegration of the coated paper decreases.

The aromatic vinyl monomer used in the production of the copolymer latex of the present invention is not particularly limited, and examples thereof include styrene, methylstyrene, vinyltoluene, chlorostyrene, hydroxymethylstyrene and the like. . These can be used alone or in combination of two or more. Of these aromatic vinyl monomers, styrene is preferred.

[0015] The amount of the aromatic vinyl monomer used is 15 to 70% by weight, preferably 15 to 60% by weight of the total monomers. When the amount is less than 15% by weight, the coating film of the copolymer becomes soft and the adhesive strength becomes too strong, and the disintegration of the coated paper is reduced. If it exceeds 70% by weight, the coating film of the copolymer hardens and becomes brittle, cracks are easily caused by a slight force, and the moisture-proof property of the moisture-proof paper decreases.

The ethylenically unsaturated acid monomer used in the production of the copolymer latex of the present invention is not particularly limited as long as it is an ethylenically unsaturated monomer having an acid group such as a carboxyl group, a sulfonic acid group and a phosphinyl group. It is not limited, and examples thereof include an ethylenically unsaturated carboxylic acid monomer, an ethylenically unsaturated sulfonic acid monomer, and an ethylenically unsaturated phosphoric acid monomer.

Examples of the ethylenically unsaturated carboxylic acid monomer include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; and unsaturated polycarboxylic acids such as fumaric acid, maleic acid, itaconic acid and butenetricarboxylic acid. Polyvalent carboxylic acids; examples include partial esterified products of ethylenically unsaturated polycarboxylic acids such as monoethyl maleate and monomethyl itaconate.

Examples of the ethylenically unsaturated sulfonic acid monomer include vinyl sulfonic acid, methyl vinyl sulfonic acid, styrene sulfonic acid, (meth) allyl sulfonic acid,
Ethyl (meth) acrylic acid-2-sulfonate, 2-acrylamide-2-hydroxypropanesulfonic acid, and the like. Examples of the ethylenically unsaturated phosphoric acid monomer include (meth) acrylic acid-3-chloro-2-propyl phosphate, (meth) acrylic acid-2-ethyl phosphate,
Allyloxy-2-hydroxypropane phosphoric acid and the like.

These ethylenically unsaturated acid monomers can be used as alkali metal salts or ammonium salts. These ethylenically unsaturated acid monomers can be used alone or in combination of two or more.

Among these ethylenically unsaturated acid monomers, ethylenically unsaturated carboxylic acids are preferred, and ethylenically unsaturated monocarboxylic acids are more preferred. Of the ethylenically unsaturated monocarboxylic acids, methacrylic acid is particularly preferred.

The amount of the ethylenically unsaturated acid monomer used is 1 to 35% by weight, preferably 5 to 30% by weight of the total monomers. If the amount is less than 1% by weight, the copolymer latex cannot form a dense coating film having sufficient moisture resistance,
The moisture resistance of the coated paper decreases. If the content exceeds 35% by weight, the coating film of the copolymer hardens and easily cracks with a slight force, and the moisture-proof paper has reduced moisture-proof properties.

In the production of the copolymer latex for coating the moisture-proof paper of the present invention, if necessary, other ethylenically unsaturated monomers copolymerizable with the above monomers may be used. Is also good.

Other copolymerizable ethylenically unsaturated monomers include, for example, crosslinkable monomers; (meth) acrylate monomers; (meth) acrylamide monomers;
Examples include an ethylenically unsaturated nitrile monomer.

Examples of the crosslinkable monomer include conjugated divinyl compounds such as divinylbenzene; di (meth) acrylates such as polyethylene glycol di (meth) acrylate and polypropylene glycol di (meth) acrylate; and trimethylolpropane tri ( And poly (meth) acrylates such as meth) acrylate and pentaerythritol tri (meth) acrylate.

Examples of (meth) acrylate monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and (meth) acrylate.
Butyl acrylate, 2-ethylhexyl (meth) acrylate, trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, dibutyl maleate, dibutyl fumarate, diethyl maleate, methoxy (meth) acrylate Examples include methyl, ethoxyethyl (meth) acrylate, methoxyethoxyethyl (meth) acrylate, cyanomethyl (meth) acrylate, 2-cyanoethyl (meth) acrylate, hydroxyethyl acrylate, and glycidyl methacrylate.

The (meth) acrylamide monomer includes:
For example, (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide and the like can be mentioned. Examples of the ethylenically unsaturated nitrile monomer include (meth) acrylonitrile, fumaronitrile, α-chloroacrylonitrile, α-cyanoethylacrylonitrile, and the like. Two or more of these other copolymerizable ethylenically unsaturated monomers may be used in combination.

The copolymer latex for coating a moisture-proof paper of the present invention has a tetrahydrofuran-insoluble content (hereinafter referred to as "THF-insoluble content") of the copolymer constituting the latex of 60% by weight or more, preferably 60% by weight or more. 70 to 95% by weight. If the amount is less than 60% by weight, the coating film of the copolymer becomes dense, so that the disintegration property decreases.

The copolymer latex for coating the moisture-proof paper of the present invention has a glass transition temperature (hereinafter referred to as "Tg") of the copolymer constituting the copolymer latex of -10 to 50 ° C, preferably-. 10 to 40 ° C. If the temperature is lower than -10 ° C,
Since the coating film of the copolymer becomes a soft and dense coating film, the disintegration of the coated paper decreases. When the temperature exceeds 50 ° C., the coating film of the copolymer becomes very brittle, so that the coating film is easily cracked by applying a slight force, and the moisture-proof property of the coated paper decreases.

The copolymer latex for coating a moisture-proof paper of the present invention has a particle size of 50 to 300 nm, preferably 70 to 300 nm.
250 nm. If it is less than 50 nm, the viscosity after adjusting the latex is high, handling becomes difficult, and even if handling is possible, the stability when formed into a coating composition is low. And drying becomes difficult when preparing coated paper. When it is larger than 300 nm, the copolymer latex cannot form a dense coating film having a sufficient moisture-proof property, so that the moisture-proof property of the coated paper decreases.

The copolymer latex for moisture-proof paper of the present invention has a weight loss rate of 5% by weight or less, preferably 3% by weight, when the formed latex film is immersed in distilled water at 40 ° C. for 3 hours. % Or less. If it exceeds 5% by weight, pinholes are formed in the film, and the moisture-proof property of the coated paper is reduced.

The method for producing the copolymer latex for coating the moisture-proof paper of the present invention is not particularly limited, but usually emulsion polymerization is used. The emulsion polymerization and its conditions are not particularly limited, and various known methods can be employed.

The monomers used for the polymerization may be added to the reaction vessel after mixing the various monomers to be used, or may be separately added to the reaction vessel. Examples of the method of adding the monomer include, for example, a method in which a monomer to be used is added all at once to a reaction vessel, a method in which the monomer is added continuously or intermittently according to the progress of polymerization, and a part of the monomer. , And the reaction is continued until a specific conversion rate is reached, and then the remaining monomer is added continuously or intermittently to carry out polymerization. Either method may be employed. When the monomers are mixed and added continuously or intermittently, the composition of the mixture may be constant or may vary.

In the polymerization, a seed polymerization method may be employed. When the seed polymerization method is employed, the composition of the seed latex is not particularly limited, and may be the same as or different from the composition of the monomer mixture used for producing the copolymer latex. Further, the particle size and the amount of the seed latex used are not particularly limited. The polymerization temperature is not particularly limited, but is usually 5 to 90 ° C.

For the production of the copolymer latex for coating a moisture-proof paper of the present invention, commonly used emulsifiers, polymerization initiators, molecular weight regulators and the like can be used. The method for adding these polymerization auxiliary materials is not particularly limited, and any method such as an initial batch addition method, a divided addition method, and a continuous addition method can be employed.

The emulsifier used in the production of the copolymer latex for coating the moisture-proof paper of the present invention is not particularly limited, and examples thereof include anionic salts such as alkylbenzene sulfonates, aliphatic sulfonates, and sulfates of higher alcohols. Nonionic emulsifiers such as polyethylene glycol alkyl ether type, polyethylene glycol alkyl ester type and polyethylene glycol alkyl phenyl ether type; carboxylate, sulfate, sulfonate, phosphate or phosphate as anion moiety And amphoteric surfactants having an amine salt or a quaternary ammonium salt as a cation moiety.

The proportion of the emulsifier used is based on all monomers.
Usually, it is 0.05 to 2% by weight, preferably 0.05 to 1% by weight.

The polymerization initiator used for producing the copolymer latex for coating a moisture-proof paper of the present invention is not particularly limited.
For example, inorganic initiators such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; t-butyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide,
Di-t-butyl peroxide, t-butyl cumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, t-butyl peroxide Organic peroxides such as isobutyrate; and azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, and the like. These inorganic initiators and organic initiators can be used alone or in combination of two or more. The inorganic initiator and the organic initiator can be used as a redox polymerization initiator in combination with a reducing agent such as sodium bisulfite.

The proportion of the polymerization initiator to be used is usually 0.1 to 5% by weight, preferably 0.5 to 5% by weight, based on all monomers.
3% by weight.

The molecular weight modifier used in the production of the copolymer latex for coating on the moisture-proof paper of the present invention is not particularly limited. For example, α-methylstyrene dimer; t-dodecyl mercaptan, n-dodecyl mercaptan, octyl mercaptan Mercaptans; halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, and methylene bromide; and sulfur-containing compounds such as tetraethylthiuram disulfide, dipentamethylenethiuram disulfide, and diisopropylxanthogen disulfide. These can be used alone or in combination of two or more.

Further, as necessary, polymerization auxiliary materials such as a chelating agent, a dispersing agent, a pH adjuster, and a preservative can be used, and these are not particularly limited in kind or amount.

The moisture-proof paper coating composition of the present invention is characterized by containing the copolymer latex for moisture-proof paper coating of the present invention and a pigment.

The pigment used in the moisture-proof paper coating composition of the present invention is not particularly limited, and examples thereof include inorganic materials such as clay, calcium carbonate, titanium oxide, aluminum hydroxide, satin white, silica, talc and barium sulfate. Pigments; organic pigments such as plastic pigments and binder pigments. These can be used alone or in combination of two or more.

The amount of the pigment used is usually 10 parts by weight based on 100 parts by weight of the solid content of the copolymer latex for coating the moisture-proof paper.
５００500 parts by weight.

A wax can be added to the moisture-proof paper coating composition of the present invention, if necessary.

The wax that can be used in the present invention is:
Although not particularly limited, for example, paraffin wax, candelilla wax, carnauba wax, rice wax, ceresin wax, petrolactam, Fischer
Tribush wax, polyethylene wax, montan wax and its derivatives, microcrystalline wax and its derivatives, hydrogenated castor oil, liquid paraffin,
And stearic acid amide. Of these, paraffin wax is preferred. These waxes are 2
Mixtures of more than one type can also be used.

The amount of the wax used is usually 5 to 100 parts by weight of the solid content of the copolymer latex for moisture-proof paper coating.
0 parts by weight or less. When the use amount of the wax exceeds 50 parts by weight, the disintegration of the moisture-proof coated paper decreases.

The solid content of the moisture-proof paper coating composition of the present invention is not particularly limited, but is usually 30 to 70% by weight.
Preferably it is 40 to 70% by weight.

The moisture-proof coated paper of the present invention can be obtained by applying the above-mentioned moisture-proof paper coating composition onto base paper.

The base paper used for the moisture-proof coated paper of the present invention is not particularly limited, and base paper made of pulp such as mechanical pulp, chemical pulp and waste paper pulp can be used. The basis weight of the base paper is not particularly limited, and is usually 40 to 220 g / m.
^Two things are used.

The method of applying the moisture-proof paper coating composition of the present invention is not particularly limited, and examples thereof include a blade coater,
This is performed using a roll coater, brush coater, air knife coater, curtain coater, bar coater, gravure coater, short dwell coater, or the like. After coating, by drying, a coating film of the copolymer is formed on the base paper to obtain a moisture-proof coated paper. The drying temperature is usually 5
0 ° C. or higher.

The coating amount of the moisture-proof coated paper of the present invention is particularly limited.
Although not specified, it is usually 10 to 40 g / side on a dry weight basis.
m^Two, Preferably 15 to 35 g / m^TwoIt is. 10g /
m^TwoIf the value is less than 1, the coating film of the copolymer becomes thin and
Water vapor easily passes from the feet. Enough for this
It is not possible to obtain a good moisture-proof effect. On the other hand, 40 g / m ^Two
If it exceeds, the moisture-proof paper cannot be finely disintegrated.
Disintegration is reduced.

[0052]

The present invention will be described in more detail with reference to the following examples. The parts and percentages in the examples and comparative examples are on a weight basis, and the weight of the copolymer latex is in terms of solid content. [Evaluation Method of Copolymer Latex] Methods for measuring the THF insoluble content, Tg, latex particle size and weight loss ratio of the copolymer are as follows.

(THF-insoluble content) A glass plate held horizontally was dried so that the thickness of the film after drying was about 2 mm.
A copolymer latex having a pH of 7 was cast at a temperature of 23 ° C.
Dry naturally for 48 hours in a constant temperature and humidity room maintained at a relative humidity of 65%. The obtained film was cut into 2 mm × 2 mm, and about 0.3 g of the film was cut into a box-shaped 80 mesh wire mesh (weight:
Ag) and weighed (weight: Bg). This is put in a glass beaker, 100 ml of tetrahydrofuran is poured, and the mixture is left at room temperature for 48 hours. After standing for 48 hours, the wire net is pulled out, placed on an aluminum plate (weight: Cg) weighed in advance, and left in a fume hood for 4 hours. Thereafter, the entire aluminum plate is dried in a dryer at 105 ° C. for 3 hours, and the dry weight (weight: Dg) of the entire aluminum plate is measured. The THF insoluble content is calculated by the following equation. THF-insoluble content (%) = (D-C-A) × 100 / B

(Tg) A glass plate held horizontally was adjusted to a pH of 7 so that the film thickness after drying was about 2 mm.
Is cast and air-dried for 48 hours in a thermo-hygrostat maintained at a temperature of 23 ° C. and a relative humidity of 65%. The obtained film is cut into a size of 2 mm × 2 mm, and about 10 mg (9.5 to 10.5 mg, since the response to the temperature is reduced if the amount charged is large),
Differential scanning calorimeter (Seiko Electronics Co., Ltd., model RDC22
Put in the glass transition temperature measurement container of 0) and cover it. This was set in the above differential scanning calorimeter, and the initial temperature was -10.
The measurement is performed under the conditions of 0 ° C., end temperature of 150 ° C., and heating rate of 10 ° C./min.

(Particle Size) The copolymer latex after polymerization is
Using a transmission electron microscope (H7500, manufactured by Hitachi, Ltd.), the particle size of 20 latex particles was measured, and the average value was determined.

(Weight loss rate) The prepared latex was put on a PET film at 110 ° C. for 6 hours using an applicator bar.
Coating was performed so that the thickness after drying for 0 second was 80 μm to obtain a latex film. This was cut into a size of 3 × 5 cm, peeled off from the PET film, and the dry weight (Xg) of the latex film was measured. 4
The film was immersed in 300 ml of distilled water heated to 0 ° C for 3 hours, and the film was taken out. The film was dried with a dryer at 105 ° C for 2 hours, and the weight (Yg) was measured. The weight loss rate was calculated from the following equation. Weight loss rate (%) = (XY) × 100 / X

[Method of Evaluating Coated Paper] The method of evaluating the moisture-proof property and the disintegration property of the coated papers of Examples and Comparative Examples is as follows.

(Preparation of Coated Paper) The coating composition is applied to one side of kraft paper having a basis weight of 80 g / m ² using a wire bar so that the dry weight is 30 g / m ² . After the application, it is dried in a hot air dryer at 110 ° C. for 1 minute. After drying, the coated paper is left overnight in a constant temperature and humidity room adjusted to a temperature of 23 ° C. and a relative humidity of 65% to obtain a coated paper for testing.

(Moisture Proof) Moisture Permeability Water Vapor Permeability Test Method (J
According to IS Z 0208: Cup method B method), the moisture permeability of the test coated paper is measured. The moisture permeability is 60 (g / m
^The coated paper having a length of 2/24 hours or less has excellent moisture resistance. Moisture permeability 40 (g / m ^2/24 hours) coated paper or less is excellent further moisture resistance.

(Disintegration) 5c
Make 36 coated papers of size mx 5 cm. (However, if the total weight of these coated papers is less than 10 g, further cut the coated paper and add one small piece to obtain the total weight. Is 10 g). This is poured into 500 g of tap water at 20 ° C. while keeping the above-mentioned size. This was put in a household mixer and stirred for 2 minutes.
It is hand-made to a size of mx 25 cm to obtain one pulp sheet. This sheet is placed in a hot-air circulation oven at 120 ° C. for 20 minutes and dried. The sheet is taken out, and the undisintegrated material (coated film piece, paper piece, etc.) is visually observed and evaluated. When the maximum size of the undisintegrated material is less than 2 mm square, it is indicated by ○, when it is 2 to 5 mm square, Δ, and when it exceeds 5 mm square, it is indicated by X. ○:
Excellent disintegration. Δ: Disintegration is slightly inferior. ×: Poor disintegration.

Example 1 45 parts of ion-exchanged water was charged into a polymerization vessel equipped with a temperature detection sensor and a stirrer, and the inside was replaced with nitrogen. Thereafter, the internal temperature was raised to 80 ° C. while stirring. On the other hand, 58 parts of ion-exchanged water, 0.3 part of sodium lauryl sulfate, 22 parts of styrene, 7 parts of methyl methacrylate, 12 parts of acrylonitrile, 1 part of acrylamide, 1 part of itaconic acid, 1 part of methacrylic acid were placed in a pressure vessel equipped with a stirrer. Was charged and 12 parts of t-dodecyl mercaptan was charged, and then the inside was replaced with nitrogen and 45 parts of butadiene was charged and emulsified to obtain an emulsion. Furthermore,
In a separate container, 1 part of potassium persulfate was dissolved in 19 parts of ion-exchanged water to prepare a 5% aqueous solution of potassium persulfate. 80 ℃
, The prepared emulsion and a 5% aqueous solution of potassium persulfate were added together using separate pumps over 3 hours. 5 of emulsion and potassium persulfate
After completion of the addition of the aqueous solution, the reaction was continued for another 3 hours while maintaining the temperature at 80 ° C., and then a polymerization terminator was added to terminate the polymerization. At this time, the polymerization conversion was 99%, and the particle size was 10%.
It was 0 nm. Unreacted monomers of the copolymer latex were removed, and the solid content was further concentrated to 52%. After the concentration, the pH of the copolymer latex was adjusted to 7, and ion-exchanged water was further added so that the solid content concentration was 50% and the pH was 7
Was obtained. Table 1 shows the properties of this copolymer latex.

Next, ion-exchanged water was added to 0.5 part of Alon T-40 (manufactured by Toa Gosei Chemical Co., Ltd.) and 0.2 part of ammonia in a homomixer so that the final solid concentration was 56%. While charging and stirring, 50 parts of mica A21 (manufactured by Mica Yamaguchi Kogyo Co., Ltd.) was gradually added, and the mixture was further stirred for 1 hour. 50 parts of the above latex in terms of solid content was mixed and stirred with the obtained dispersion, and the solid content concentration was adjusted to 52% with ion-exchanged water to obtain a coating composition. This composition was applied to one side of kraft paper having a basis weight of 80 g / m ² using a wire bar so that the dry weight was 30 g / m ² . After the application, the coating was dried in a hot air dryer at 110 ° C. for 1 minute, and left overnight in a constant temperature and humidity room at a temperature of 23 ° C. and a relative humidity of 65%. Table 1 shows the results of evaluating the moisture permeability and disintegration of the coated paper.

[0063]

[Table 1]

Examples 2 to 8 and Comparative Examples 1 to 8 Copolymer latexes were obtained in the same manner as in Example 1 except that the formulations shown in Tables 1 and 2 were used. The properties of the copolymer latex were evaluated in the same manner as in Example 1, and the results are shown in Table 1. Further, coated papers were prepared in the same manner as in Example 1 using these copolymer latexes. Table 1 shows the evaluation results.

From the evaluation results of the coated paper in Table 1, the following can be understood for the coated paper of the comparative example. The coated papers of Comparative Examples 1 to 3 using the copolymer latex in which the weight loss of the copolymer latex film is larger than the range specified in the present invention have poor moisture proof properties. The coated paper of Comparative Example 4 using a copolymer latex in which the THF insoluble content of the copolymer is smaller than the range specified in the present invention is inferior in disintegration.

The coated paper of Comparative Example 5 using a copolymer latex in which the glass transition temperature of the copolymer is lower than the range specified in the present invention is inferior in disintegration. The coated paper of Comparative Example 6 using a copolymer latex in which the copolymer has a glass transition temperature higher than the range specified in the present invention has poor moisture-proof properties. In Comparative Example 7 using a copolymer latex in which the particle size of the copolymer latex was smaller than the range specified in the present invention, the viscosity of the latex was too high to be evaluated. The coated paper of Comparative Example 8 using a copolymer latex in which the particle size of the copolymer latex is larger than the range specified in the present invention is inferior in moisture-proof property.

On the other hand, it can be seen that the coated papers of Examples 1 to 8 using the copolymer latex of the present invention have excellent moisture-proof properties and disintegration properties.

[0068]

Industrial Applicability According to the present invention, a moisture-proof coated paper excellent in moisture-proof and pulverizing properties, a copolymer latex for coating a moisture-proof paper used for producing such a coated paper, and a copolymer thereof. A moisture-proof paper coating composition containing a latex and a pigment can be obtained.

[0069]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08F 236/04 C08F 236/04 F term (Reference) 4J002 AC021 AC081 DE136 DE146 DE236 DG046 DJ016 DJ036 DJ046 FD096 GK04 HA07 4J038 CA021 CC011 CG011 CG061 MA13 MA14 NA04 PC10 4J100 AB02Q AB03Q AB04Q AB07Q AB07R AB08Q AB16S AJ01R AJ02R AJ03R AJ08R AJ09R AL03S AL04S AL08R AL08S AL09S AL10S AL34S AL36R AL63S AL65S AM01S AM02S AM03S AM14R AM15S AM21S AP01R AS01P AS02P AS03P AS04P AS07P BA03Q BA03R BA03S BA05S BA06S BA08S BA40S BA56R BA58R BA64R BA67R BB01R BB01S BB10S CA05 CA06 DA25 DA40 EA07 FA03 FA20 JA13 4L055 AG63 AG70 AG71 AG72 AG76 AH02 AH23 AH37 AJ04 EA16 EA20 EA29 EA32 EA33 FA11 FA30 GA47

Claims (3)

[Claims] 1. An aliphatic conjugated diene monomer 25 to 70% by weight, an aromatic vinyl monomer 15 to 70% by weight, an ethylenically unsaturated acid monomer 1 to 35% by weight, and copolymerization therewith. 0 to 50% by weight of other possible ethylenically unsaturated monomers
Is a latex of a copolymer obtained by polymerizing a monomer composed of a copolymer in an aqueous medium, wherein the copolymer has a tetrahydrofuran-insoluble content of 60% by weight or more and a glass transition temperature of -1.
0 to 50 ° C., and the particle size of the copolymer latex is 50 to 50 ° C.
A copolymer latex for coating a moisture-proof paper, wherein the latex has a thickness of 300 nm and a weight loss rate of a film on which the latex is formed is 5% by weight or less. 2. A moisture-proof paper coating composition comprising the copolymer latex according to claim 1 and a pigment. 3. A moisture-proof paper coated with the moisture-proof paper coating composition according to claim 2.