JP2671049B2 - Two-component acrylic emulsion adhesive - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive for electrostatic flocking.

More specifically, it is an adhesive for electrostatic flocking of automotive interior, light electrical, and office equipment components, while maintaining leakage, adhesion, heat resistance, boiling resistance, etc. to the base material,
The present invention relates to a two-component acrylic emulsion-based adhesive that significantly reduces the effects on the human body such as skin disorders (fog).

(Prior Art) Conventionally, a console box as an automobile interior member,
Glove boxes, pillars, rear corners, air conditioner loopers (wind direction adjusting plates) as light electric materials, and feed rolls as office equipment (copying machines) are made of gold side plates, painted steel plates, plastic plates or molded products as base materials. ,
A one-pack type acrylic emulsion or an acrylic-modified vinyl acetate emulsion adhesive was mainly used, and fine fiber yarns (pile) of nylon, polyester, acrylic, etc. were subjected to electrostatic flocking.

(Problems to be solved by the invention) A problem with electrostatic flocking products using these adhesives is that they sometimes have a poor leak property with respect to a coated steel plate or a plastic substrate, that is, a cissing phenomenon occurs. However, there is a problem in that the adhesive strength is low, and the heat resistance, boiling resistance, and abrasion resistance are significantly reduced.

As means for solving these problems, a two-part adhesive based on an aqueous emulsion has been developed in consideration of pollution, fire, and adverse effects on the human body.

That is, an amino group, a methylolamide group, a hydroxyl group, a carboxyl group, a so-called synthetic rubber latex into which a functional group monomer such as epoxy is introduced using an aqueous emulsion as a base (a main agent), an acrylic emulsion, and a vinyl acetate emulsion are used. , As a curing agent
Numerous methods for combining urea resins, melamine resins, phenol resins, epoxy resins, isocyanate resins, metal salts, and the like have been proposed.

Such a two-part adhesive has a stability after the two-part compounding, that is, a workability problem that the pot life is short or the viscosity is remarkably changed. There was a practical problem with the adhesive performance such as strength, heat resistance and boiling resistance.

As a two-component acrylic emulsion-based adhesive for solving these problems, the present inventors, as described in the specification of Japanese Patent Application No. 63-033875 and Japanese Patent Application No. 63-126911, an epoxy-modified acrylic emulsion, We proposed a method of blending an aqueous emulsion of a modified aliphatic polyamine or a mixture of a water-soluble amine, a modified polyamide resin, a polyhydric alcohol derivative and water as a curing agent.

However, in recent years, in automobile interiors and office equipment, demands for safety of the adhesive to the human body and storage stability have been increasing more and more, and it is necessary to more fully meet these demands.

(Means for Solving the Problems) The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, use an epoxy-modified acrylic emulsion as a main component and a high-purity, high-boiling point imidazole epoxy as a curing agent. Adhesive strength, heat resistance, boiling resistance, abrasion resistance, and other adhesive properties are obtained by using a mixture of a curing agent, which is mainly composed of a curing agent, a thickener, a lower alcohol such as methyl alcohol, and water. Therefore, the present invention was completed, and it was found that it is extremely effective in preventing cissing, skin damage (fogging), and rhinitis.

That is, the present invention relates to (1) a two-component acrylic emulsion adhesive consisting of an epoxy-modified aqueous acrylic emulsion and a curing agent, wherein (A) imidazole epoxy curing agent (B) thickener (C) lower (2) a two-pack type acrylic emulsion-based adhesive characterized in that a mixture of alcohol and (D) water is blended in an amount of 5 to 30 parts by weight based on 100 parts by weight of the solid content of the epoxy-modified aqueous acrylic emulsion; ) Epoxy-modified water-based acrylic emulsion
1 part to 30 parts by weight of epoxy resin is contained in 100 parts by weight of the solid content of the epoxy-modified acrylic emulsion, and the two-component acrylic emulsion-based adhesive according to item (1), and (3) curing 20 to 50% by weight of imidazole epoxy curing agent of (A), 2 to 10% by weight of thickening agent of (B), 1 to 10% by weight of lower alcohol of (C), (D)
(2) A two-component acrylic emulsion adhesive according to item (1), which is a mixture of 40 to 80% by weight of water.

The epoxy-modified acrylic emulsion used in the present invention is an acrylic emulsion containing an epoxy resin, for example, an epoxy resin acrylic emulsion obtained by reacting an epoxy resin dissolved in monomers during emulsion polymerization of an aqueous acrylic emulsion. There is a composite emulsion that measures alloying within particles.

The acrylic emulsion used here is a copolymer emulsion of the following hard monomer, soft monomer and functional group monomer.

Specifically, examples of the hard monomer include one or more of styrene, methyl methacrylate, acrylonitrile, and vinyl acetate.

Examples of the soft monomer include one or more of methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate.

As the functional monomer, as those having a carboxy group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, etc., as those having an amide group,
Examples of those having a hydroxyl group such as acrylamide, methacrylamide, and maleamide include hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl acrylate, and those having an N-methylolamide group include N-methylolacrylamide.

The epoxy resin is a bisphenol A-epiclorhydrin resin, for example, an epoxy equivalent of 180 to 27.
An epoxy resin having a viscosity of 5 to 150 poise (25 ° C.) can be used.

A preferable composition ratio of these is 30 as a hard monomer.
〜60 parts by weight, soft monomer toshite 20-50 parts by weight, functional group monomer 1-10 parts by weight, epoxy resin 1-
It is in the range of 30 parts by weight. However, the sum of these four is 10
0 parts by weight.

When the proportion of the hard monomer is less than 30 parts by weight, problems occur in the adhesive strength, heat resistance and boiling resistance. When the proportion is more than 60 parts by weight, the film-forming properties of the emulsion are impaired, and the adhesive strength is reduced.

When the proportion of the soft monomer is less than 20 parts by weight, the film-forming property is impaired, and the adhesive strength is reduced. When the proportion is more than 50 parts by weight, problems are caused in the adhesive strength, heat resistance and boiling resistance.

When the proportion of the functional monomer is less than 1 part by weight, there is a problem in the stability at the time of emulsion polymerization and mechanical stability when applied to a coating machine, and when the proportion is more than 10 parts by weight, depending on the functional group monomer used, In addition to impairing the polymerization stability, the viscosity increase with an adhesive, and the storage stability, they are expensive compared to general monomers and cause economical problems.

When the proportion of the epoxy resin is less than 1 part by weight, the adhesive strength, heat resistance and boiling resistance are not significantly improved, and when the proportion is more than 30 parts by weight, it acts as a kind of polymer plasticizer and exhibits tackiness and polymerization. Stability is greatly reduced, causing problems in emulsion polymerization, and lacks practicality.

Among them, preferred combinations and ratios are styrene 35 to 55 parts by weight, butyl acrylate 35 to 45 parts by weight, or styrene 45 to 55 parts by weight, and 2-ethylhexyl acrylate 30 to 40 parts by weight as a main component. , 1 to 3 parts by weight of hydroxyethyl acrylate, 1 to 1 of methacrylic acid
3 parts by weight, acrylamide 1-3 parts by weight, epoxy resin
The composition ratio is 10 to 20 parts by weight.

A typical method for producing the epoxy-modified acrylic emulsion of the present invention is as follows.

First, the monomers and epoxy resin mixed and dissolved in advance are added to distilled water containing an emulsifier while stirring,
These monomers and the like are emulsified.

On the other hand, in the same manner as in a normal emulsion polymerization method, distilled water and an emulsifier are charged into a flask, stirred under a nitrogen seal, heated to 60 to 80 ° C., and a polymerization initiator is administered.

Emulsified liquids such as the above monomers were continuously administered to this over several hours, after treatment with residual monomers, cooled, alkali neutralized, and thickened with polyacrylic acid or water-soluble polymer as necessary. It is manufactured by

Examples of the imidazole epoxy curing agent of the component (A) in the curing agent used in the present invention include 2-methylimidazole,
2-ethyl-4-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2,4-dimethylimidazole and the like can be mentioned. Among these, from the viewpoint of solubility in water, stability of the dissolved product, pot life when compounded in the main agent, and economical efficiency, melting point 137-145 ° C, boiling point
2-Methylimidazole which is a pale yellow powder at 177-178 ° C is preferred.

The thickener of the component (B) is used for the purpose of preventing a decrease in viscosity when a curing agent is blended with an epoxy-modified acrylic emulsion as a main component whose viscosity has been adjusted for various coating machines. The thickener used in the present invention, polyvinyl alcohol, methyl cellulose, ethyl cellulose,
Examples include thickeners such as carboxymethyl cellulose, methyl vinyl ether / maleic anhydride copolymer, polyacrylic acid, polyacrylic acid salt, and nonionic surfactant type.

Among these, nonionic surfactants are preferable, and urethane-modified polyether type thickeners are particularly preferable, from the viewpoints of the stability of the curing agent mixture and the viscosity change when compounded in the main agent.

As the lower alcohol as the component (C), there are methyl alcohol, ethyl alcohol and the like, and methyl alcohol is particularly preferable. Also, it may be either industrial or reagent grade,
It is used together with water to dissolve the nonionic surfactant thickener.

The water of the component (D) is used for dissolving the imidazole-based epoxy curing agent and the nonionic surfactant-based thickener, and may be distilled water, ion-exchanged water, or optionally city water.

The mixing ratio in the curing agent is 20 to 50% by weight, preferably 25 to 35% by weight, for the imidazole epoxy curing agent as the component (A). When the amount is less than 20% by weight, the curing of the adhesive is insufficient, and the adhesive strength, heat resistance and boiling resistance are poor. When the amount is more than 50% by weight, the solubility of water is hindered.

The thickener as the component (B) is in the range of 2 to 10% by weight, preferably 3 to 5% by weight. Thickener or 2% by weight
When the amount is less than the above, when compounded in an epoxy-modified acrylic emulsion, the yearly decrease of the compound is remarkable, and when it exceeds 10% by weight, on the contrary, there is a significant increase in viscosity and there is a practical problem.

The lower alcohol as the component (C) is in the range of 1 to 10% by weight, preferably 3 to 8% by weight. If the lower alcohol content is less than 1% by weight, uniform dilution and dissolution of the thickener will be hindered. If it is more than 10% by weight, there is a risk that aggregates will be generated when blended into the epoxy-modified acrylic emulsion.

The component (D) water is in the range of 40 to 80% by weight, preferably 50 to 70% by weight. When the amount of water is less than 40% by weight, dissolution of the imidazole-based epoxy curing agent and the thickener is hindered, and when more than 80% by weight, a large amount is required to obtain sufficient curability when compounded in the epoxy-modified acrylic emulsion. It is indispensable to mix it, leading to a decrease in solid content and a decrease in viscosity, resulting in an inadequate formation of an adhesive layer having a certain thickness on the electrostatic flocking substrate, and depending on the shape of the substrate, sagging occurs and flocking occurs. It causes unevenness and becomes a quality problem.

The mixing ratio of the curing agent of the present invention with respect to 100 parts by weight of the solid content of the epoxy-modified acrylic emulsion is in the range of 5 to 30 parts by weight, preferably 10 to 15 parts by weight.

If the blending ratio of the curing agent is less than 5 parts by weight, the adhesive will be insufficiently cured, and the adhesive strength, heat resistance and boiling resistance will be lacking. As a result, the quality of the electrostatic flocking processed product is reduced, resulting in quality problems and lack of practicality.

As described above, the two-component acrylic emulsion-based adhesive of the present invention uses an epoxy-modified acrylic emulsion as a base (main component), while the component as a curing agent has a high boiling point as compared with other amine-based and polyamide-based adhesives. Therefore, since it has very little volatility, the risk of affecting the substance, that is, the risk of causing skin damage (irritation), rhinitis, etc. is extremely low, and the risk of odor pollution is also extremely low.

In addition, in the present invention, the stability of the curing agent mixture is good, and the pot life when blended with the main agent is long and extremely easy to handle. Furthermore, since it does not cause cissing on painted steel sheets or plastics and has excellent adhesive strength, heat resistance, boiling resistance, abrasion resistance, etc. that should be provided as an adhesive for electrostatic flocking in automobile interiors, light electric power, office equipment, etc. The value is extremely high.

When using the present adhesive, a coloring agent, an antifoaming agent, an antioxidant, an ultraviolet absorber, a surfactant, a leveling agent, a thickener, and the like may be added as necessary.

EXAMPLES Next, the present invention will be specifically described with reference to Reference Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples.

In the following, parts or% are based on weight unless otherwise specified.

Reference Examples 1 to 3 At a mixing ratio shown in Table 1, as an imidazole-based epoxy curing agent, Curezol 2MZ (manufactured by Shikoku Kasei Co., Ltd., trade name, melting point 137 to 145 ° C., boiling point 177 to 178 ° C.) in room temperature water. A thickener obtained by dissolving and then dissolving SN Thickener A-803 (trade name, urethane-modified polyether type, manufactured by San Nopco Ltd.) as a thickener in advance with a mixed solvent of water / methanol = 1/1. Was blended to obtain a curing agent used in the present invention.

Examples 1 to 9 100 parts by weight of a mixture of a monomer and an epoxy resin shown in Table 2 and a mixed monomer of a chain transfer agent were continuously administered to distilled water and sodium dodecylbenzenesulfonate under stirring conditions to emulsify. To do.

Separately, 50 parts of distilled water and 0.2 parts of sodium dodecylbenzenesulfonate are charged into a flask, stirred under a nitrogen blanket, heated to 70 ° C., and then 0.5 parts of potassium persulfate is administered.

An emulsion of the above-mentioned monomer or the like is continuously administered to this over 4 hours, and the remaining monomers are polymerized at the same temperature for 4 hours,
Cool to 30 ° C or less, adjust to pH 7 with 14% ammonia water,
An epoxy-modified acrylic emulsion having a solid content of 50% was obtained.

The emulsion thus obtained was adjusted to a viscosity of 4000 cps using an aqueous solution of partially saponified polyvinyl alcohol in order to increase the viscosity for air spray application.
An epoxy modified acrylic emulsion adhesive was obtained.

The curing agent mixtures obtained in Reference Examples 1 to 3 were stirred and mixed with 200 parts of the emulsion at a ratio shown in Table 2 to obtain a two-component acrylic emulsion type adhesive.

Physical properties of this adhesive were evaluated by the methods described below, and the results are shown in Table 3.

1) Viscosity stability 1-1) Change in viscosity immediately after mixing two components Two minutes after mixing two components, BH-type rotational viscometer, NO4 rotor 20RPM
Then, the viscosity at 25 ° C. was measured, and based on the viscosity of the epoxy-modified acrylic emulsion of 4000 cps, the increase / decrease in viscosity was indicated as follows.

○: Viscosity change of ± 500 cps or less △: Viscosity change of ± 500-1000 cps ×: Viscosity change of ± 1000 cps or more 1-2) Viscosity change over time after mixing two liquids Viscosity change after 8 hours of mixing two liquids The measurement was performed in the same manner as in the above 1-1) and displayed in the same manner.

2) Electrostatic flocking An ABS plate and a melamine-coated steel plate are coated with 200 g / m ² of the adhesive of the present invention uniformly using air spray.

Then nylon pile (3 denier, length 0.5mm)
Is applied with a voltage of 30 KV and planted.
After drying for minutes, a flocking sample for physical property evaluation was prepared.

3) Repelling phenomenon Adhesive of the present invention is uniformly applied to melamine-coated steel sheet with remarkable repelling phenomenon by air spray at 50 g / m ^2, and the presence or absence of repelling of the coating film is visually observed and displayed as follows. did.

○: no cissing phenomenon ×: cissing phenomenon 4) Physical property evaluation method Using an air spray on the ABS plate, the adhesive of the present invention
00g / m ^{2 was} evenly applied, and cotton broad # 40 cloth was immediately adhered and dried in a hot air dryer at 70 ° C. for 45 minutes to prepare a sample for physical property evaluation.

Next, this sample was cut into a length of 100 mm and a width of 25 mm to obtain a sample for measuring an adhesive force by a Tensilon tensile tester.

4-1) Adhesive strength 200 mm / min in the above-mentioned sample 23 ± 2 ° C, RH65% constant temperature room
Peeling in the direction of an angle of 180 ° at the speed of
Displayed in g / 25 mm.

4-2) Heat resistance The same test was performed in the atmosphere of 80 ° C. as in the above-mentioned method 4-1), and the same indication was given.

4-3) Boiling resistance The sample prepared in 4) was immersed in boiling water for 30 minutes, cooled down to room temperature, leaked, and subjected to the same test as in 4-1), and displayed in the same manner.

4-5) Abrasion resistance of flocking product The sample prepared in 2) was attached to a friction element with a cotton blade # 40 cloth using a Gakushin type friction fastness tester, and a load of 500 g was applied.
At the speed of 30 times / min, rub the 30 x 200 mm flocked surface, and
The presence or absence of a change in the flocked surface after rubbing 000 times was displayed as follows.

○: No abnormality △: Partial thin hair loss ×: Approximately 50% hair loss per area 5) Confirmation of skin disorders (rash, rhinitis, odor) 10 panelists from the research company used conventional denatured aliphatic Each of the polyamine aqueous emulsion and the curing agent mixture of the present invention was blended with an epoxy-modified acrylic emulsion, spray-coated on an ABS plate, and dried at 70 ° C for 40 minutes,
The presence or absence of odor, itching of the skin, abnormality of the nose, etc. was confirmed. The results are shown in Table-3. The evaluation was carried out at intervals of one week, and when the abnormality was confirmed even by one person, it was indicated by x, and when there was no abnormality, it was indicated by o.

Comparative Examples 1 to 4 In the same manner as in Examples, using the acrylic emulsion having the invention shown in Table 2 and a composition outside the scope of the present invention, and a curing agent mixture outside the scope of the present invention, the above-mentioned execution The physical properties were evaluated in the same manner as in the example, and the results are shown in Table-3.

(Effects of the Invention) As is clear from Table 3, the two-component acrylic emulsion-based adhesive of the present invention has been conventionally used as a curing agent for an epoxy-based adhesive in the electrostatic flocking processing field. Compared to the case, the risk of causing skin disorders such as rash, rhinitis and odor is significantly reduced, and the viscosity stability during blending with the main ingredient epoxy modified acrylic emulsion and over time is excellent, and electrostatic Since it has excellent adhesive strength, heat resistance, boiling resistance, and abrasion resistance as well as leakage to a base material to be provided as a flocking adhesive, the practical value is high and its significance is great.

Claims (3)

(57) [Claims] 1. A two-component acrylic emulsion adhesive comprising an epoxy-modified aqueous acrylic emulsion and a curing agent, wherein the curing agent is (A) an imidazole epoxy curing agent (B) a thickener (C) a lower alcohol, and (D) A two-pack type acrylic emulsion adhesive, characterized in that 5 to 30 parts by weight of a mixture of water and 100 parts by weight of the solid content of the epoxy-modified aqueous acrylic emulsion is blended. 2. An epoxy-modified water-based acrylic emulsion, wherein the epoxy-modified acrylic emulsion has a solid content of 100.
The two-component acrylic emulsion-based adhesive according to claim 1, which contains 1 to 30 parts by weight of an epoxy resin in parts by weight. 3. An imidazole type epoxy curing agent having a curing agent (A) of 20 to 50% by weight, a thickening agent of (B) of 2 to 10% by weight,
1 to 10% by weight of the lower alcohol (C) and water (D)
The two-component acrylic emulsion adhesive according to claim 1, which is a mixture of 40 to 80% by weight.