JPS6268870A - Acrylic pressure-sensitive adhesive dispersed in water - Google Patents

Abstract

PURPOSE:To obtain the titled adhesive having improved adhesivity and cohe sivity, by adding fine powder of silica, antimony oxide, alumina or carbon black to an acrylic adhesive. CONSTITUTION:The objective pressure-sensitive adhesive contains one or more kinds of fine powder of silica, antimony oxide, alumina or carbon black (preferably silica having particle diameter of preferably <=100nm) preferably in the form of an aqueous dispersion. The amount of the fine powder to be added to the adhesive is preferably 0.5-50pts.(wt.) based on 100pts. of the acrylic base polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a water-dispersed acrylic adhesive whose adhesive strength and cohesive strength are improved by fine powder selected from silica, antimony oxide, alumina, and carpump hook. It is.

Conventional techniques and problems Conventionally, water containing an acrylic polymer as a main component obtained by radical polymerization of a radically reactive monomer mainly composed of esters of acrylic acid or methacrylic acid in the presence of a water dispersant such as a surfactant has been used. In dispersed acrylic adhesives,
The balance between adhesive force and cohesive force, which are important for adhesive properties, can be adjusted by changing the combination of component monomers, using intraparticle crosslinking agents, and introducing carboxyl, hydroxyl, or aldehyde groups into the acrylic polymer main chain. This has been done by crosslinking particles between particles via functional groups such as melamine compounds, polyvalent metal compounds, etc.

However, with these conventional adjustment methods, it is difficult to achieve both adhesive force and cohesive force and to control the balance thereof, resulting in the problem that it is difficult to obtain a product with satisfactory adhesive properties.

Means and Action for Solving the Problems The present inventor has overcome the above-mentioned problems in order to develop a water-dispersed acrylic pressure-sensitive adhesive that has both adhesion and cohesive force, or whose balance can be properly controlled. As a result of extensive research, it was discovered that this objective could be achieved by adding a certain type of fine powder. The present invention has been made based on this new knowledge.

That is, the present invention provides a water-dispersible acrylic pressure-sensitive adhesive to which fine powder made of one or two glazes selected from the group consisting of silica, antimony oxide, alumina, and carbon black is added. .

By adding the above-mentioned fine powder, the adhesive force and cohesive force of the obtained adhesive are improved and both of these are achieved, and the contribution to the improvement of the adhesive force and cohesive force is different depending on the amount of the fine powder added. Control of the balance is achieved by this.

The fine powder used in the present invention is one or more of the group consisting of silica, antimony oxide, alumina, and carbon black. In particular, the stability of the system, such as the ability to maintain the mixed state of the system and the non-gelling property, in other words, the lack of settling of fine powder, which causes variations in the quality of the resulting adhesive, and the adhesive strength and cohesive strength. In particular, the contribution to the improvement of adhesive strength is large, so the effect is great even with a small amount used, the gelation of the mixture is difficult to occur, and the functionalities such as carboxyl groups in the acrylic base polymer. The acrylic paste polymer can be used in a wide range of applications, such as being less likely to cause base-salt crosslinking (reducing the contribution to improving adhesive strength), and can be used in a wide pH range without destroying the acrylic paste polymer. Silica is preferably used because it can be used.

The above-mentioned fine powder is preferably used in the form of an aqueous dispersion from the viewpoint of dispersibility in the system. The aqueous dispersion may be prepared physically using a surfactant or the like, but it is preferably prepared by a chemical method. Examples of commercially available shells include silica-based products such as Snowtex J (WR product name, manufactured by Nichiryo Kagaku Kogyo Co., Ltd.) and Applied.
(trade name, manufactured by Kadenka Kogyo Co., Ltd.), and other examples include "alumina sol" and "antimony oxide sol" (trade name, manufactured by Nichiryo Kagaku Kogyo Co., Ltd.).

The particle size of the fine powder is 1100 nm or less in primary particles, that is, particles before dispersion or in a water-dispersed state, particularly 10 to
100 nm is suitable. If the particle size exceeds 1100 nm, the effect of the addition will be reduced and it will be difficult to control the balance between adhesive force and cohesive force, which is not preferable.

The amount of fine powder added depends on the softness of the acrylic base polymer,
It is determined as appropriate depending on conditions such as the presence or absence of additives such as softeners and tackifier resins, their types, and their blending amounts. Generally, the amount added is 0.5 to 50 parts by weight, preferably 1 to 20 parts by weight, based on the solid content of the fine powder, per 100 parts of the acrylic base polymer. The amount added is 0
If the amount is less than 5 parts by weight, the resulting adhesive may have poor cohesive force, and if it exceeds 50 parts by weight, the degree of improvement in the adhesive strength of the resulting adhesive may be reduced.

Known acrylic base polymers can be used in the present invention. For example, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isobutyl acrylate, isobutyl methacrylate, decyl acrylate, decyl methacrylate, etc.
Esters of about 14 alcohols and acrylic acid or methacrylic acid are used as raw monomers, and these are copolymerizable monomers containing functional groups such as acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, diethylamino methacrylate, vinyl acetate, acrylonitrile, For example, copolymers with copolymerizable monomers for modification such as styrene can be mentioned. For example, their production involves combining the above component monomers with a structural initiator such as ammonium persulfate, potassium persulfate, or hydrogen peroxide. This can be carried out by a known method of radical polymerization in water in the presence of a nonionic or anionic surfactant.

The water-dispersible acrylic adhesive of the present invention comprises the above-mentioned fine powder or its aqueous dispersion, an acrylic paste polymer aqueous dispersion, or a plasticizer such as dibutyl tucrate or dioctyl phthalate, rosin, a rosin derivative, or a terpene derivative. It can be obtained by mixing tackifier resins such as tackifier resins, pigments, fillers, and other modifiers as necessary. At that time, a pH adjuster such as aqueous ammonia or acetic acid may be used as necessary for the purpose of stabilizing the mixed system.

Effects of the Invention According to the water-dispersed Acrylic 77 adhesive of the present invention, it is possible to obtain an adhesive with excellent adhesive force and cohesive force based on the added fine powder. It is also possible to control the balance between adhesive force and cohesive force in the adhesive.

Furthermore, since there is no need to perform intraparticle crosslinking or interparticle crosslinking, there are fewer restrictions on the component monomers used, and there are also advantages such as a wide range of combinations of component monomers can be selected.

In addition, it has the advantage that a water-dispersible acrylic pressure-sensitive adhesive with excellent adhesive properties can be produced by a simple operation of simply mixing fine powders.

Examples Reference Example 1 97 parts of butyl acrylate (coulometric parts, the same applies hereinafter), 3 parts of methacrylic acid, 0.3 parts of ammonium persulfate, 0.5 parts of a nonionic emulsifier, and 100 parts of ion-exchanged water,
The reaction was carried out at 80° C. for 5 hours to obtain an aqueous dispersion of an acrylic base polymer.

Reference Example 2 To the aqueous dispersion of Reference Example 1, 20 parts of a rosin ester softener and 20 parts (solid content) of a terpene phenol resin emulsion were added per 100 parts of the acrylic base polymer to obtain a mixture.

Examples 1 to 4 0.5 parts, 1 part, and 3 parts of finely powdered silica (average particle size 10 to 20 nm) aqueous dispersion in terms of solid content per 100 parts of acrylic base polymer to the aqueous dispersion of Reference Example 1 Alternatively, 10 parts of the mixture was added and stirred to obtain a water-dispersed acrylic pressure-sensitive adhesive.

Examples 5 to 7 100 parts of the acrylic base polymer was added to the mixture of Reference Example 2, and 5 parts, 15 parts, or 30 parts of an aqueous dispersion of finely powdered silica (average particle size 10 to 20 nm) in terms of solid content were added and stirred. A water-dispersible acrylic adhesive was obtained below.

Examples 8-10 Alumina sol (average particle size 20-50 nm), antimony oxide V (average particle size 20-50 nm) or carbon black (average particle size 34-35 nm) was added to the aqueous dispersion of Reference Example 1 per 100 parts of the acrylic base polymer. ) A water-dispersed acrylic pressure-sensitive adhesive was obtained by adding 2 parts, 20 parts, or 10 parts of the aqueous dispersion in terms of solid content, respectively, and stirring.

Comparative Example The aqueous dispersion of the acrylic base polymer in Reference Example 1 was used as it was.

Evaluation test Borien Terfilm K with a thickness of 2571 m Dormitory m Example:
The water-dispersed acrylic adhesive obtained in the comparative example was applied to a film thickness of 50 parts and 1 meter, and dried at 100°C for 3 minutes to obtain an adhesive tape. Adhesive strength and cohesive strength were investigated.

〔Adhesive force〕

Adhesive strength at 180 degrees beer K was measured according to JIS Z-1528.

[Cohesive force]

Adhesive tape was pasted on the Bakelite board in an area of 10 layers x 20 m1, one end of the adhesive tape protruded from the Bakelite board as a free end, and a metal rod was attached to it via a clip, giving a total load of 500F. Hold it vertically with the

The time required for the adhesive tape to separate from the Bakelite plate and fall under a rainbow temperature atmosphere of 80° C. was measured.

The results are shown in the table below.

From the margin table below, we can see that adhesion and cohesive force can be improved by adding fine powder, that both adhesion and cohesive force can be achieved, and that by changing the amount of fine powder added, adhesive force and cohesive force can be improved. This shows that the balance of cohesive force can be controlled.

Claims (1)

[Scope of Claims] 1. A water-dispersible acrylic adhesive containing one or more fine powders selected from the group consisting of silica, antimony oxide, alumina, and carbon black. 2. The adhesive according to claim 1, which contains a fine powder added in the form of an aqueous dispersion. 3. The adhesive according to claim 1, wherein the particle size of the fine powder is 100 nm or less. 4. Claim 1, wherein the amount of fine powder added is 0.5 to 50 parts by weight per 100 parts by weight of the acrylic base polymer.
Adhesive described in section. 5. The adhesive according to claim 1, wherein the fine powder is silica.