JPH06136339A - Acrylic pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To provide an acrylic pressure-sensitive adhesive particularly an ion- cross-linked acrylic pressure-sensitive adhesive excellent in pressure-sensitive adhesiveness. CONSTITUTION:An acrylic copolymer comprising a major amount of a (meth) acrylic ester and an alpha,beta-unsaturated carboxylic acid is mixed with at least two metal compounds in which the metals are selected from a combination of a group I or II element. with a group III, IV or VIII element in the short- form periodic table, and subjected to ion cross-linking. The obtained acrylic pressure-sensitive adhesive is excellent in long-time sealing properties for a rough surface and other pressure-sensitive adhesive properties and is very useful for a pressure-sensitive adhesive tape for a rough-surfaced adherend such as crepe paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic pressure-sensitive adhesive, and more particularly to an ion-crosslinking acrylic pressure-sensitive adhesive having excellent adhesive properties.

[0002]

2. Description of the Related Art As a pressure-sensitive adhesive for a pressure-sensitive adhesive tape or a pressure-sensitive adhesive sheet, an acrylic pressure-sensitive adhesive composed of a copolymer containing (meth) acrylic acid ester as a main component is widely used.

[0003]

Such an acrylic pressure-sensitive adhesive is excellent in weather resistance, heat resistance and transparency as compared with a normal natural rubber-based pressure-sensitive adhesive, but it has a roughened surface. When used as an adhesive for adhesive tape for sealing such as crepe paper, it has poor initial adhesiveness to the adherend, or when it is held for a long time, it is difficult to open the sealed part, so-called long-term sealing property There was a problem that it was inferior to.

[0004]

DISCLOSURE OF THE INVENTION The present invention has found an ionic cross-linking type acrylic pressure-sensitive adhesive which can solve the above-mentioned problems, and the gist thereof is to contain an α, β unsaturated carboxylic acid. However, for the acrylic copolymer containing (meth) acrylic acid ester as the main component, the metal is added to the (group I or group II element) and (III
An acrylic pressure-sensitive adhesive characterized in that it is obtained by adding two or more kinds of metal compounds in combination with a group, a group IV or a group VIII element and ion-crosslinking them.

The present invention will be described in more detail below. The acrylic copolymer used in the present invention has a (meth) acrylic acid ester as a main component, and the alcohol component constituting the ester is, for example, butyl alcohol,
Octyl alcohol, 2-ethylhexyl alcohol,
Primary alcohols such as lauryl alcohol can usually be used, and two or more kinds of acrylic acid esters composed of these alcohol components may be combined.

Further, the acrylic copolymer must contain α, β unsaturated carboxylic acid, and as the α, β unsaturated carboxylic acid, acrylic acid, (meth) acrylic acid, itaconic acid, maleic acid, etc. Can be used. The content of the α, β unsaturated carboxylic acid relative to the total amount of the copolymer components is 0.1 to
It may be used in the range of 10% by weight, preferably 0.3 to 5% by weight. If the content is less than 0.1% by weight, the cohesive strength becomes insufficient, and if it exceeds 10% by weight, the tack becomes insufficient. Prone.

In addition to the above components, the acrylic copolymer of the present invention can appropriately use a copolymerizable vinyl monomer such as vinyl acetate or styrene as a copolymerization component.

As the pressure-sensitive adhesive of the present invention, it is necessary to add two or more kinds of metal compounds of a specific combination to the above acrylic copolymer and ionically crosslink the metal compounds. (I in the periodic table
Group (or group II element) and (group III, group IV or group VIII element) must be combined.

Other than this combination, there is a problem that it is difficult to improve the physical properties of the obtained pressure-sensitive adhesive.
A combination of metal compounds using only Group III or Group II elements has excellent long-term sealing property on rough surfaces, but poor initial adhesion, and metal compounds containing only Group III elements are used. The combination has a problem that the initial adhesiveness to the rough surface is excellent, but the long-term sealing property is poor.

In the combination of metals, in particular Group II elements such as Ca, Mg, Zn and Group III and IV elements such as A
A combination with l, Ti, Zr or the like is preferable because the physical properties of the obtained pressure-sensitive adhesive are easily improved.

The metal compound is a metal compound which can be ionized in an acrylic pressure-sensitive adhesive, and examples thereof include metal chelate compounds, rosin metal salts, carboxylic acid metal salts, metal hydroxides and metal oxides.

Examples of the metal chelate compound include chelate compounds of various metals with chelators such as acetylacetone, malonic acid diesters, ketone alcohols and amino alcohols. Examples of the rosin metal salt include calcium-cured rosin and zinc-cured rosin.

Although the cohesive force of the pressure-sensitive adhesive improves as the amount of the metal compound added increases, the adhesive properties such as tack decrease, so the amount of the metal compound added is the carboxyl group and the acyl group in the above-mentioned acrylic copolymer. It is preferable that the total amount is 0.1 to 5.0 equivalents with respect to the oxide.

Next, in the pressure-sensitive adhesive of the present invention, it is necessary to mix the above-mentioned acrylic copolymer and a metal compound to ionically crosslink, and as a method therefor, a solvent is used for uniform mixing or a solvent-free method. Known means such as heat mixing and reaction can be applied.

Further, a tackifying resin may be added as appropriate in order to improve the tackiness, and ordinary rosin, rosin ester, terpene resin and the like can be used.

[0016]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 With respect to 100 parts by weight of an acrylic copolymer composed of 58.0% by weight of 2-ethylhexyl acrylate, 40.0% by weight of butyl acrylate and 2.0% by weight of acrylic acid,
2 parts by weight of zinc acetylacetone salt and 0.3 parts by weight of aluminum acetylacetone salt were added, dissolved and mixed in the presence of a solvent (a mixed solution of ethyl acetate and acetylacetone), and then coated on a polyester film having a thickness of 38 μm, After drying, an adhesive tape having an adhesive thickness of 20 μm was obtained.

Example 2 To 100 parts by weight of an acrylic copolymer having the same composition as in Example 1, 2 parts by weight of calcium acetylacetone salt and 0.3 part by weight of aluminum acetylacetone salt were added.
After uniformly kneading at 0 ° C., a 38 μm polyester film was pressed by a pressing machine so that the thickness of the adhesive was 20 μm to obtain an adhesive tape.

Example 3 To 100 parts by weight of an acrylic copolymer having the same composition as in Example 1, 2.0 parts by weight of magnesium acetylacetone salt and 0.3 parts by weight of aluminum acetylacetone salt were added, and a solvent (ethyl acetate) was added. And a mixed solution of acetylacetone and ethanol), and the thickness is 38
It was coated on a polyester film having a thickness of μm and dried to obtain an adhesive tape having a thickness of 20 μm.

Comparative Example 1 An adhesive tape was obtained in the same manner as in Example 1 except that 2.0 parts by weight of zinc acetylacetone salt was used as the metal compound.

Comparative Example 2 An adhesive tape was obtained in the same manner as in Example 1 except that only 0.6 part by weight of aluminum acetylacetone salt was used as the metal compound.

Comparative Example 3 An adhesive tape was obtained in the same manner as in Example 1 except that 2.0 parts by weight of zinc acetylacetone salt and 0.3 parts by weight of calcium acetylacetone salt were used as the metal compound.

Comparative Example 4 An adhesive tape was obtained in the same manner as in Example 1 except that 0.6 part by weight of aluminum acetylacetone salt and 0.3 part by weight of titanium acetylacetone salt were used as the metal compound.

Table 1 shows the results of an adhesive property test such as long-term sealing property, initial adhesion and holding force using the adhesive tape of each of the above Examples and Comparative Examples. Here, the test method of each evaluation item is as follows.

"Long-term sealing property" As shown in the schematic view of FIG. 1, crepe paper (75 gf / m ² , 50 mm × 40 mm)
Two pieces were arranged horizontally, and the tape 3 (width P = 40 mm) was used, and each tape was moved back and forth once with a roller having a load of 250 gf so that an adhesive tape of 20 mm each was applied. Then load 30 gf around the fulcrum 2 on both ends of the crepe paper 1.
Then, the time until one of the pressure-sensitive adhesive tapes 3 was peeled from the crepe paper 1 was measured. The test atmosphere condition is 23 ° C.
× 50% relative humidity.

"Initial Adhesion" The crepe paper used in the above-mentioned sealing property evaluation test was reciprocated by a roller having a tape load of 250 gf and reciprocated one by one, and the adhesion was measured by the 180 ° tension method within 30 seconds. (Peeling speed 300 mm / min, test atmosphere 23 ° C. × 50% relative humidity) “Holding power” The displacement distance was measured according to JIS Z0237. However, the measuring temperature is 40 ° C and the bonding area of the test piece is 18
mm width × 20 mm length.

[0027]

[Table 1] It can be seen from Table 1 that Examples 1 to 3 using the pressure-sensitive adhesive of the present invention are excellent in long-term sealing property with respect to the rough surface of the crepe paper, initial adhesiveness and holding power. On the other hand, in Comparative Example 1 and Comparative Example 2 in which only one type of metal compound was used, the long-term sealing property or the initial adhesiveness was inferior, and even when two types of metal compounds were used, elements of the same group It is understood that Comparative Example 3 and Comparative Example 4 in which the above are combined are inferior in long-term sealing property or initial adhesive property as in Comparative Examples 1 and 2.

[0028]

As described above, the acrylic pressure-sensitive adhesive of the present invention is superior to conventional acrylic pressure-sensitive adhesives in long-term sealing property on rough surfaces and other pressure-sensitive adhesive properties, and it is suitable for use in rough surfaces such as crepe paper. It is highly applicable as an adhesive tape for surface-attached objects.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a measuring device for measuring rough surface adhesiveness.

[Explanation of symbols]

 1 crepe paper 2 fulcrum 3 adhesive tape W load

Claims (1)

[Claims] 1. An acrylic copolymer containing an α, β-unsaturated carboxylic acid and having a (meth) acrylic acid ester as a main component is added with a metal in the periodic table (group I or II). Group element) and (group III, IV or VIII group element) combination of two or more metal compounds,
An acrylic pressure-sensitive adhesive characterized by being ionically crosslinked.