JPH03279492A - Resin composition for moisture-resistant and waterproofing coating of paper - Google Patents

Abstract

PURPOSE:To obtain the title composition to be readily defibrated, reusable without separating old paper, having high moisture-resisting and waterproofing effects, hardly causing blocking phenomena, by blending an aqueous dispersion of specific synthetic resin with a wax-based emulsion in a specific ratio. CONSTITUTION:(A) An aqueous dispersion of synthetic resin obtained by subjecting a monomer mixture consisting of (i) 70-98wt.% hydrophobic alpha,beta- monoethylenic unsaturated monomer selected from an acrylic alkyl ester, a methacrylic alkyl ester and an aromatic unsaturated monomer and (ii) 2-30wt.% acrylamide and/or methacrylamide to emulsion polymerization is blended with (B) 20-200 pts.wt. solid content based on 100 pts.wt. solid content of the component A of a wax-based emulsion to give the objective composition.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an aqueous coating resin composition for coating paper to impart moisture resistance and waterproof properties.

BACKGROUND OF THE INVENTION Conventionally, paper has been widely treated to make it moisture-proof and waterproof by laminating it with a synthetic resin film such as polyethylene. However, when this type of paper is collected and used as waste paper, the laminate film poses a problem as undisintegrated resin, so it has been necessary to separate it from the waste paper and remove it.

Therefore, as a moisture-proof and waterproof treatment that can be used as waste paper,
Products using wax emulsions are known (Special Publication No. 63-39022, Japanese Patent Publication No. 63-39023).
number, etc.).

Problems to be Solved by the Invention However, when a wax-based emulsion is used, the processed paper is slippery, the moisture resistance may decrease when it is dried at high temperatures during use, and the coated surface may be susceptible to mechanical damage. This caused many problems, such as the tendency for problems to occur, and it could not necessarily be said that it was an excellent process.

In order to solve this problem, a wax emulsion was mixed with a synthetic rubber latex and used (Special Publication Publication No. 55
-22597) has also been carried out, but although this method provides considerably high moisture resistance, it is still not sufficient, and it is necessary to increase the amount of coating on the paper. As a result, many new problems have arisen, such as processed paper becoming more slippery, more susceptible to mechanical damage, and more likely to cause blocking.

Furthermore, it is also used by mixing with other water-based synthetic resins (Japanese Patent Publication No. 62-28826), but depending on the type of synthetic resin, water repellency can be obtained, but when mixed with synthetic rubber latex, Also, types with a large amount of soft acrylic acid alkyl ester or those with a large coating amount tend to cause blocking of processed paper.

The present invention has been developed in view of the above circumstances, and even with a relatively small amount of coating at a low concentration, it has sufficient moisture-proofing and waterproofing effects, is resistant to mechanical damage, and does not cause the blocking phenomenon. The object of the present invention is to provide a resin composition for coating paper that is hard to coat.

As a means to solve the problems, the present invention provides a hydrophobic α/β monoethylenically unsaturated monomer selected from the group consisting of an acrylic acid alkyl ester, a methacrylic acid algyl ester, and an aromatic unsaturated monomer. Aqueous content of synthetic resin obtained by emulsion copolymerization of a monomer mixture consisting of 70 to 98% by weight of 0° and 2 to 30% by weight of acrylamide and/or methacrylamide￥LT
h, the aqueous synthetic resin dispersion is blended with 100 parts by weight of the solid content, and 20 to 200 parts by weight of the wax emulsion is blended with the solid content.

Hydrophobic α which is the raw material monomer of the aqueous dispersion in the present invention
- Acrylic acid alkyl esters and methacrylic acid alkyl esters as β monoethylenically unsaturated monomers include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate,
2-ethylhexyl acrylate, methyl methacrylate,
Ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-methacrylate
Ethylhexyl and other esters of alkyl groups having 10 to 18 carbon atoms of acrylic acid or methacrylic acid are used.

Further, examples of the aromatic unsaturated monomer include styrene, α-methylstyrene, vinyltoluene, and the like.

As for the hydrophobic α/β monoethylenically unsaturated monomer, the various monomers mentioned above can be used alone or in combination of two or more types, but they have different properties in terms of coverage on paper, wax emulsion and From the miscibility of acrylic acid alkyl ester or methacrylic acid alkyl ester 35 to 88% by weight,
It is preferable to use 10 to 40% by weight of an aromatic unsaturated monomer in combination.

The weight ratio of acrylamide or methacrylamide copolymerized with these α/β monoethylenically unsaturated monomers is:
It is necessary that the amount is 2 to 30% by weight. If it is less than 2% by weight, the moisture-proofing effect of the present invention cannot be obtained, and if it exceeds 30% by weight, the viscosity of the polymer increases and it tends to coagulate during polymerization, and the resulting processed paper has poor moisture-proofing and water resistance. decreases. In particular, about 5 to 20% by weight is most suitable.

In addition, other crosslinking monomers, anionic monomers, hydrophilic monomers, hydrophobic monomers, etc. may be added to this copolymer to the extent that they do not interfere with the balance between hydrophilicity and hydrophobicity of the resin. However, it is also possible to use them together in small amounts.

The copolymer dispersion in water in the present invention must be obtained by emulsion polymerization, but the emulsion polymerization method involves using a monomer mixture together with a surfactant in an aqueous system to generate radical Through a heating polymerization reaction using a polymerization initiator (persulfate, peroxy compound, azobis compound, etc.),
Or a redox polymerization initiator (persulfate or peroxy compound, sulfite, g-acid ferrous salt, Rongalite,
(combined with a reducing agent such as ascorbic acid)
Then, polymerization can be carried out in a conventional manner by increasing the amount of initiator by a little S.

In the present invention, the wax emulsion used in combination with the aqueous dispersion of synthetic resin has a melting point of 40 to 1
It is preferable to use a mixture of 00° C. wax and modified rosin or maleated petroleum resin.

Function: In the present invention, acrylamide or methacrylamide is copolymerized with the synthetic resin aqueous dispersion.

In general, acrylamide or methacrylamide is a hydrophilic monomer, and copolymerization with it is thought to worsen the water resistance of synthetic resins. However, according to research by the inventors, By copolymerizing these with a synthetic resin, the hydrophilicity and hydrophobicity of the synthetic resin are balanced, and by using this as a coating resin for paper, it actually improves the moisture resistance and water resistance of processed paper. It turns out that it does.

Furthermore, since acrylamide and methacrylamide have a high second-order transition temperature, copolymerizing them increases the second-order transition temperature of the synthetic resin and reduces the blocking property of processed paper.

Effects of the Invention Therefore, according to the present invention, it is easier to disintegrate compared to moisture-proof and waterproof paper made by laminating synthetic resin films, and it becomes possible to reuse waste paper without separating it.

In addition, compared to conventional wax-based emulsions and coating resins that mix them with other water-based synthetic resins, they have a high moisture-proofing and waterproofing effect with a small amount of coating, and are not mechanically damaged. This makes it difficult for the blocking phenomenon to occur when sheets of paper are stacked on top of each other.

Example Examples of the present invention will be described below.

Example 1 440 parts by weight of water, 5 parts by weight of sodium dodecylbenzenesulfonate, 4 parts by weight of sodium dodecylbenzenesulfonate were placed in a reaction vessel equipped with a stirrer and a thermometer.
17.5 parts by weight of a 0% acrylamide aqueous solution, 78 parts by weight of styrene, 67 parts by weight of n-butyl acrylate, and 48 parts by weight of n-butyl methacrylate are added, and the temperature is raised to 70°C. Next, 3 parts by weight of 10% ammonium persulfate was added to carry out a polymerization reaction, and the mixture was kept at 90°C for 3 hours, cooled, and neutralized with aqueous ammonia, resulting in a solid content of 3011%, p.
An aqueous synthetic resin dispersion of H8.2 was obtained.

Next, wax emulsion (manufactured by Harima Kasei Kogyo Co., Ltd., trade name Hariko) 0P-5012, solid content 3 was added to 100 parts by weight of solid content of the obtained synthetic resin aqueous dispersion.
5% by weight) with a solid content of 65 parts by weight and diluted with water to make 3
A 0% by weight coating resin dispersion was obtained.

Example 2 In a reaction vessel equipped with a stirrer and a thermometer, 280 parts by weight of water, 2 parts by weight of sodium dodecylbenzenesulfonate, 3 parts by weight of sodium alkyldiphenyl ether disulfonate, 35 parts by weight of 40% by weight aqueous acrylamide solution, and 55 parts by weight of styrene. 41 parts by weight of methyl methacrylate, 63 parts by weight of n-butyl acrylate and 28 parts by weight of 2-ethylhexyl acrylate and heated to 40°C. and 1.5 parts by weight of 10% sodium bisulfite were added to conduct a polymerization reaction, held at 90°C for 4 hours, cooled, and neutralized with aqueous ammonia to synthesize a solid content of 40% by weight and pH 3°0. An aqueous resin dispersion was obtained.

Then, the solid content of the aqueous synthetic resin dispersion obtained was 1.

A solid content of 65 parts by weight of Haricoat 0P-5012 (as described above) was mixed with 0ijL parts, and the mixture was diluted with water to obtain a 30% by weight coating resin dispersion.

Example 3 310 parts by weight of water, 5 parts by weight of sodium dodecylbenzenesulfonate, 4 parts by weight of sodium dodecylbenzenesulfonate were placed in a reaction vessel equipped with a stirrer and a thermometer.
751 parts of 0% acrylamide aqueous solution, 7 parts of styrene
1 part by weight, 19 parts by weight of methyl methacrylate, 63 parts by weight of n-butyl acrylate and 17 parts by weight of 2-ethylhexyl acrylate, and the temperature was raised to 40°C. A polymerization reaction was carried out by adding 10 parts by weight of 15% by weight sodium binitite, maintained at 90°C for 4 hours, cooled, and neutralized with aqueous ammonia to obtain an aqueous synthetic resin with a solid content of 35% by weight and a pH of 8.8. A dispersion was obtained.

Next, 65 parts by weight of Haricoat 0P-5012 (mentioned above) was mixed with 100 parts by weight of the solid content of the resulting synthetic resin aqueous dispersion, and diluted with water to obtain a 30% by weight coating resin dispersion. Obtained.

Comparative Example 1 In a reaction vessel equipped with a stirrer and a thermometer, 280 parts by weight of water, 5 parts by weight of sodium dodecylbenzenesulfonate, 78 parts by weight of styrene, 71 parts by weight of n-butyl acrylate,
48 parts by weight of n-butyl methacrylate and 3 parts by weight of acrylic acid were added, and the temperature was raised to 40°C. Next, 2.5 parts by weight of 10% ammonium persulfate and 1.5 parts by weight of 10% sodium binitate were added to conduct a polymerization reaction at 90°C.
After being held for 4 hours, it was cooled and neutralized with aqueous ammonia to obtain an aqueous synthetic resin dispersion with a solid content of 40% by weight and 1) 87.8%.

Next, 65 parts by weight of Haricoat 0P-5012 (mentioned above) was mixed with 100 parts by weight of the solid content of the resulting synthetic resin aqueous dispersion, and diluted with water to obtain a 30% by weight coating resin dispersion. Obtained.

Comparative Example 2 Haricoat 0P-501 was added to 100 parts by weight of solid content of styrene-butadiene latex (manufactured by Mitsui Toatsu Co., Ltd., trade name Polylux 755, solid content 50% by weight).
2 (above) was mixed with 65 parts by weight of solid content and diluted with water to obtain 3.
A 0% by weight coating resin dispersion was obtained.

Using the resin dispersions for coating obtained in Examples 1 to 3 and Comparative Examples 1 to 2, the coated resin dispersions obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were coated on double-sided kraft paper with a basis weight of 70 g/rri' using a bar coater, and then heated at 100°C for 1 hour. It was dried to obtain processed paper. The coating amount was 9 g/rIi'.

Each processed paper was tested for moisture permeability, anti-blocking properties, and disintegration properties.

Test method Moisture permeability: Measured by the cup method in accordance with JIS 20208. (Unit: g/rrl・day) Blocking resistance: The coated and non-coated surfaces of a 5 cm square sample paper were overlapped and a load of 300 (]/ca was applied, and the
After being left at 1 hour and 80°C, both were peeled off and the state of peeling on the paper surface was visually inspected.

Disintegration property = IC A sample paper of 11 squares was disintegrated at a concentration of 5% for 2 minutes, 3 minutes, and 5 minutes using a family mixer, and the presence or absence of undisintegrated portions was examined.

The test results are shown in the table below.

It can also be seen from the table test results that the coating composition of the present invention has low moisture permeability and excellent blocking resistance.

In addition, in terms of disintegration properties, results equivalent to those of the comparative example were obtained, and the results were comparable to those of conventional coating compositions.

Claims (1)

[Claims] 1 Hydrophobic α/β monoethylenically unsaturated monomers 70 to 9 selected from the group consisting of acrylic acid alkyl esters, methacrylic acid alkyl esters, and aromatic unsaturated monomers
The synthetic resin aqueous dispersion was added to an aqueous synthetic resin dispersion obtained by emulsion copolymerizing a monomer mixture consisting of 8% by weight and 2 to 30% by weight of acrylamide and/or methacrylamide. A resin composition for moisture-proofing and waterproofing coating of paper, containing 20 to 200 parts by weight of a wax emulsion as a solid content.