JPS6327572A - High-solid adhesive - Google Patents

Abstract

PURPOSE:To obtain a stable high-solid adhesive of outstanding adhesive characteristics, by successively adding to the reaction system a pre-emulsion consisting of a blend of vinyl monomer mixture of specified composition, specific emulsifying agent and water to carry out an emulsion polymerization. CONSTITUTION:A pre-emulsion prepared by blending (A) a vinyl monomer mixture consisting of (i) an acrylic ester as chief component and (ii) 0.5-15wt% of hydrophilic monomer of formula I, II or III (R1 is H or COOH; R2 is H or CH3; R3 is H or CH2OH), (B) 2-15wt% based on the whole monomer, of an emulsifying agent, i.e., a surfactant mixture made up of (iii) nonionic surfactant and (iv) 5-40wt% based on the component (iii), of anionic surfactant and (C) water is successively added to the reaction system to carry out an emulsion polymerization in the presence of a catalyst, thus obtaining the objective adhesive consisting of a polymer emulsion with a solid content 65-75wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high solid content adhesive obtained by emulsion copolymerization of a vinyl monomer mixture containing a hydrophilic monomer.

Conventionally, methods for producing latex with high solid content are disclosed in JP-A-53-84092 and JP-A-56-141311.
Although the methods described in the above publications are known, they all employ a complicated two-step process, and the solid content of the resulting latex is less than 70% at most.

Furthermore, the reality is that latexes with high solid content that can be used as adhesives are not yet known.

On the other hand, there is a great demand from the market for latex with a high solids content from the viewpoint of saving energy for drying when applying adhesives.

The present inventors found that 65-7 is not found in conventional latex.
The present invention was completed by discovering a manufacturing method for obtaining a stable latex with a high solids content of 5% by weight in one step, and by discovering that the high solids latex obtained by this manufacturing method is particularly useful for use as an adhesive. reached.

That is, the present invention has an acrylic ester as a main component and one or more hydrophilic monomer components represented by the following general formula (A), (B), or (C) in an amount of 0.5 to 0.5 to 15% by weight
The purpose of this invention is to provide a high solid content adhesive comprising an emulsion copolymerization emulsion of a vinyl monomer mixture containing a solid content of 65 to 75% by weight. That is, the present invention has an acrylic ester as a main component and has the following general formulas (A) and (B).
In emulsion copolymerizing a vinyl monomer mixture containing 0.5 to 15% by weight of one or more hydrophilic monomer components represented by (C), anionic surfactant and A surfactant mixture consisting of a nonionic surfactant and an anionic surfactant in an amount of 5 to 40% by weight of the nonionic surfactant is used as an emulsifier in an amount of 2 to 15% by weight based on the total monomer, and A pre-emulsion prepared by pre-mixing a monomer mixture, an emulsifier, and water is sequentially added to the reaction system and emulsion copolymerized in the presence of a catalyst, resulting in a solid content of 6.
The present invention provides a high solids adhesive comprising a polymer emulsion of 5 to 75% by weight.

However, in the formula, R1 is H or C0D)l, R, is H or CH
3', R5 represents H or CH20H. - The hydrophilic monomer of the present invention represented by the above general formula (A), (B) or (C) provides polymerization stability and low viscosity latex required for obtaining a high solid content latex. Specifically, acrylic acid, methacrylic acid, fumaric acid, maleic acid, acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, acrylic acid 2-
Examples include hydroxyethyl and 2-hydroxyethyl methacrylate.

The hydrophilic monomer is used in an amount of 0.5 to 15% by weight, preferably 1 to 10% by weight, based on the total monomers.

If it is less than 0.5% by weight, a stable latex cannot be obtained, and if it exceeds 15% by weight, the resin becomes hard and good adhesion cannot be obtained.

The vinyl monomer used in the present invention is mainly composed of acrylic ester, and acrylic ester monomers include methyl acrylate, ethyl acrylate,
Propyl acrylate, butyl acrylate, acrylic acid 2
Examples include ethylhexyl, alkyl, and lylphidecyl, which are used in an amount of at least 50% by weight in the vinyl monomer mixture. Other usable vinyl monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, vinyl acetate,
Examples include styrene, ethylene, and vinyl chloride. The high solid content adhesive of the present invention is an emulsion copolymer of a monomer mainly composed of acrylic acid ester or ester consisting of one or more of these monomers and the above-mentioned hydrophilic monomer. This adhesive has a high solids content of 65 to 75% by weight. In the present invention, the solid content refers to the value calculated using the following formula after taking a sample, that is, about 1 g of the emulsion stock solution in an aluminum dish, drying it in a hot air dryer at 105° C. for 3 hours.

Next, the method for producing the high solid content adhesive of the present invention will be described in detail.

According to the present invention, the hydrophilic monomer is added to 0% of the total monomers.
．． A mixture of a vinyl monomer mixture containing acrylic acid ester as a main component, a surfactant, and water containing 5 to 15% by weight, that is, 5 to 30% by weight of the pre-emulsion, preferably in advance with an appropriate amount of water. It is preferable to add the emulsion copolymerization to the reaction system immediately before polymerization, and then separately add the remaining 70 to 95% by weight of the pre-emulsion and the catalyst to the reaction system at the reaction temperature to carry out emulsion copolymerization. Here, the surfactant is preferably a combination of an anionic surfactant and a nonionic surfactant, and the ratio of the anionic surfactant to the nonionic surfactant is preferably 5 to 40% by weight. Outside this range, the stability of the polymer latex decreases or the particle size becomes too small and the viscosity increases, making it difficult to obtain an adhesive with a high solids content.Also, the amount of surfactant added is 2 to 15% by weight based on the total monomers.
and preferably 3 to 10% by weight. If it is less than 2% by weight, it is difficult to obtain a stable polymer latex;
If it exceeds 5% by weight, the particle size of the latex becomes small and the viscosity increases, making it difficult to increase the solid content. The surfactants used include anionic surfactants such as various fatty acid salts, higher alcohol sulfates, alkylbenzene sulfonic acids/salts, dialkyl sulfosuccinates, polyoxyethylene alkyl ether sulfates, and polyoxyethylene alkylphenol ether sulfates. I can name the sudo. In addition, as a nonionic surfactant,
Examples include polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, sorbitan fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene sorbicun fatty acid ester, polyoxyethylene polyoxypropylene block copolymer, and the like.

The catalyst is preferably a persulfate, such as potassium persulfate or ammonium persulfate, and may be used as a redox catalyst in combination with various reducing agents. The amount of catalyst used is usually in the range of 0.1 to 1% by weight based on the monomer.

The reaction of emulsion copolymerization is usually carried out at 50 to 90°C for 5 to 10 minutes.
In the present invention, a pre-emulsion method is employed in which a mixture of a vinyl monomer containing a hydrophilic monomer, a surfactant, and water, ie, a so-called pre-emulsion, is sequentially added to the reaction system. That is, emulsion polymerization may be carried out by sequentially adding a pre-emulsion and a catalyst to a reaction system. In industrial implementation, it is usually impossible to stir the stirring blade during polymerization unless a certain amount of liquid is present at the initial stage, so it is difficult to control the polymerization heat and it is difficult to carry out smooth emulsion polymerization. Therefore, as a specific implementation method, any of the following sequential addition methods (1) to (3) can be adopted.

(1) A portion of water is first placed in a reactor, and the remainder of the water, a mixture of monomers, and an emulsifier (pre-emulsion) are sequentially added separately from the catalyst for emulsion polymerization.

(2) 5 to 30% by weight, for example, about 10% by weight of the entire water, monomer, and emulsifier mixture (pre-emulsion) is first put into the reactor, and the remaining pre-emulsion and catalyst are added separately and sequentially. do.

(3) Add a portion of water, add the remainder of the water, 5 to 30% by weight of a mixture of monomers and emulsifier (pre-emulsion) immediately before polymerization, and add the remaining 70 to 30% by weight of the mixture (pre-emulsion). 95% by weight of the preemulsion is added in each case separately from the catalyst.

The particle size of the latex is at least 0.2 microns or more, and usually 2.0 microns or less, so that the viscosity of the latex can be kept at a level that poses no practical problems. The viscosity of latex is usually 500 cps to 30.00
It is in the range of 0 cps. The resulting latex is stable and can be used as a high solids adhesive with excellent adhesive properties.

The high solid content adhesive of the present invention may contain additives such as antifoaming agents, thickeners, tackifiers, and pigments. The pressure-sensitive adhesive of the present invention can be applied to various uses that take advantage of its adhesive properties, and is particularly effective for general pressure-sensitive adhesive tapes and sheets, and is also useful as a tackifier, a sealant, and the like.

The present invention will be explained below with reference to Examples and Comparative Examples, but these examples do not limit the scope of the present invention. In the examples, parts and percentages are based on weight.

Example 1 8 parts of water was charged into a polymerization iron, and to this were added 18 parts of water, 8 parts of vinyl acetate, 30 parts of butyl acrylate, 25 parts of 2-ethylhexyl acrylate, 0.6 part of methacrylamide, 3 parts of methacrylic acid, and nonion. 4 parts of surfactant (polyoxyethylene octylphenol ether), 0 parts of anionic surfactant (sodium dodecylbenzenesulfonate)
．． Add 15% of the 9 parts mixture and warm. Emulsion copolymerization was carried out by sequentially adding the remaining 85% of the above mixture and an aqueous potassium persulfate solution at about 70° C. over 5 hours.

The solid content concentration of the obtained latex was 71.5%, and the viscosity was 7.000 cps.

Example 2 6.5 parts of water was charged into a polymerization iron, and 20 parts of water, 6 parts of vinyl acetate, 55 parts of butyl acrylate, and 2-methacrylic acid were added.
10 parts of a mixture of 1.5 parts of hydroxyethyl, 2.5 parts of methacrylic acid, 3.5 parts of a nonionic surfactant (polyoxyethylene lauryl ether), and 0.8 parts of an anionic surfactant (sodium lauryl sulfate). % and warm. Emulsion copolymerization was carried out by sequentially adding the remaining 90% of the above mixture and an aqueous ammonium persulfate solution at about 75° C. over 4 hours. The solid content concentration of the obtained latex was 68.
5%, and the viscosity was 12.000 cps.

Example 3 5 parts of water was charged into a polymerization iron, and to this were added 18 parts of water, 8B1 ethyl methacrylate, 58 parts of 2-ethylhexyl acrylate, 0 and 5 parts of acrylamide, 2 parts of methacrylic acid, and a nonionic surfactant (polymer). 20% of a mixture of 3.51 parts of oxyethylene alkylphenol ether and 0.7 parts of an anionic surfactant (polyoxyethylene alkylphenol ether) was added and heated. 80% of the above mixture
and an aqueous ammonium persulfate solution were added sequentially at about 75° C. for 5 hours to carry out emulsion copolymerization. The solid content concentration of the obtained latex was 73%, and the viscosity was 7.000 cps. - Comparative Example 1 The same raw materials as in Example 1 were used in the same amounts, but the manufacturing method was changed. That is, 26 parts of water and the entire amount of nonionic and anionic surfactants were placed in a polymerization iron, and 15% of the mixture of all monomers was added and heated. An aqueous potassium persulfate solution containing the remaining 85% of all monomers was successively added at about 70° C. over 5 hours to carry out emulsion copolymerization. The solid content concentration of the obtained latex was 70.5%, and the viscosity was 50.000 cps.

Comparative Example 2 The manufacturing method was exactly the same as in Example 3, except that 2.8 parts of methyl methacrylate was used in place of acrylamide and methacrylic acid among all the monomers, and emulsion copolymerization was carried out. The solid content concentration of the obtained latex was 71%, the viscosity was 30.000 cp
It was s. The latexes obtained were very unstable. The latexes obtained in the above examples and comparative examples were coated on release paper at a coating weight of approximately 25 g/m'' (dry) and heated at a temperature of 105°C for 30 minutes. After drying for a minute, it was transferred to a polyester film with a thickness of 25 microns.Table 1 shows the results of evaluating the adhesive strength, tank strength, and holding power of this adhesive film.

Surface (note) material: Adhesive strength is adhesive film at 20℃ x 65%RH
The sample was crimped onto a 25 mm wide stainless steel plate, and after 60 minutes, the force required to peel it off in a 180° direction at a tensile rate of 300 mm/min was measured and expressed in grams.

Zero 2; Tack is J, according to Qow method 1, 20″Cx6
A steel ball is rolled on an adhesive film of lQcm on a 30° slope at 5% I'lH and is shown as ball Nα in the maximum method when it comes to rest.

Book 3: Holding force is 25+y+m x 2 of adhesive film
A 5 mm portion was temporarily crimped with stainless steel, a 1 kg load was applied at a temperature of 40° C., and the time until the load dropped was measured and expressed in seconds.

Claims (1)

[Scope of Claims] 1 The main component is an acrylic ester and has the following general formula (
In emulsion copolymerizing a vinyl monomer mixture containing 0.5 to 15% by weight of one or more hydrophilic monomer components represented by A), (B) or (C), Composed of anionic surfactant and nonionic surfactant, anionic surfactant being 5 to 40% by weight of nonionic surfactant.
A surfactant mixture is used as an emulsifier in an amount of 2 to 15% by weight based on the total monomers, and a pre-emulsion prepared by pre-mixing the vinyl monomer mixture, emulsifier, and water is sequentially added to the reaction system to form a catalyst. A high solids adhesive comprising a polymer emulsion with a solids content of 65 to 75% by weight obtained by emulsion copolymerization in the presence of. ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (A) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (B) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (C) However, in the formula, R_1 is H or COOH, and R_2 is H or CH
_3 and R_3 represent H or CH_2OH. 2. The high solids adhesive according to claim 1, wherein the proportion of acrylic ester in the vinyl monomer mixture is at least 50% by weight. 3 Emulsion viscosity is 500 cps to 30,000
The high solid content adhesive according to claim 1 or 2, which is cps. 4. The high solid content adhesive according to claim 1, 2 or 3, wherein the emulsion has an average particle diameter of 0.2 to 2.0 microns.