JPH06346037A - Acrylic pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain an acrylic pressure-sensitive adhesive composition capable of satisfying demanded performance of cohesion and adhesion, etc., and excellent in both of adhesion at normal temperature and that at high temperature. CONSTITUTION:This solvent type acrylic pressure-sensitive adhesive composition contains an acrylic polymer and a tackiness-providing resin. In the composition, the tackiness-providing resin is a resin acid ester obtained by reacting a resin acid containing a resin acid dimer with a polyhydric alcohol where the resin acid ester has a softening point of > 150 deg.C and <=185 deg.C.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an acrylic pressure-sensitive adhesive composition. More particularly, the adhesive strength at room temperature and high temperature (generally 50-100), especially for polyolefins.
The present invention relates to a solvent-based acrylic pressure-sensitive adhesive composition having excellent adhesive strength at about (° C.).

[0002]

2. Description of the Related Art Pressure-sensitive adhesive compositions used for labels, adhesive tapes, double-sided adhesive tapes, etc. have a tackiness, a cohesive force, etc. Performance such as color tone and transparency is required. Therefore, as the pressure-sensitive adhesive composition, an acrylic pressure-sensitive adhesive composition containing an acrylic polymer as a main component has been conventionally favored.

When the acrylic pressure-sensitive adhesive composition is used at room temperature, a sufficient adhesive force can be obtained by simply using an acrylic polymer. However, when the acrylic pressure-sensitive adhesive composition is used for applications exposed to high temperatures such as automobile engine parts, weak electricity, car body, etc., the adhesive strength remarkably decreases with increasing temperature. Therefore, it is difficult to use the acrylic polymer alone.

Therefore, a tackifying resin such as a rosin ester, a C9 petroleum resin, or a terpene resin is generally added to the acrylic pressure-sensitive adhesive composition in order to improve the adhesive strength. However, the acrylic pressure-sensitive adhesive composition containing the tackifying resin has an improved adhesive force at room temperature, but on the other hand, at a high temperature of about 50 to 100 ° C., the adhesive force remarkably decreases with an increase in temperature. There is a drawback, and the tackifying resin is a factor that rather lowers the adhesive strength at high temperatures.

Further, in order to increase the adhesive strength at high temperature, the amount of the crosslinkable monomer or the amount of the crosslinker used is increased to increase the crosslink density of the acrylic polymer, and to increase the crosslink density of the stannous laurate and the like. Attempts have been made to add an organometallic compound, but all of them increase the adhesive strength at high temperature, but on the contrary, there is a drawback that the adhesive strength at normal temperature decreases.

As described above, at present, an acrylic pressure-sensitive adhesive composition excellent in both adhesive strength at room temperature and adhesive strength at high temperature has not yet been obtained.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides an acrylic pressure-sensitive adhesive composition excellent in both adhesive strength at room temperature and adhesive strength at high temperature without impairing tackiness, cohesive strength and other adhesive properties. The purpose is to provide.

[0008]

[Means for Solving the Problems] The inventors of the present invention have conducted intensive studies focusing on tackifying resins blended in an acrylic copolymer to solve the above problems, and as a result, have found that a specific high softening point The inventors have found that the problems of the above-mentioned prior art can be solved by using a tackifying resin, and have completed the present invention.

That is, the present invention relates to an acrylic pressure-sensitive adhesive composition containing an acrylic polymer and a tackifying resin, wherein the tackifying resin contains a resin acid dimer and a polyhydric acid. The present invention relates to an acrylic pressure-sensitive adhesive composition, which is a resin acid ester obtained by reacting alcohol and having a softening point of more than 150 ° C. and 185 ° C. or less.

In the acrylic pressure-sensitive adhesive composition of the present invention, an acrylic polymer is used as a base polymer. The composition of the acrylic polymer is not particularly limited, and various known homopolymers or copolymers can be used as they are. As the monomer used for the acrylic polymer, various acrylic acid esters and / or methacrylic acid esters (hereinafter, abbreviated as (meth) acrylic acid ester) can be used. Specific examples of such (meth) acrylic acid ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylate.
Butyl acrylate, 2-ethylhexyl (meth) acrylate and the like can be exemplified, and these can be used alone or in combination. In addition, a small amount of (meth) acrylic acid may be used instead of a part of the (meth) acrylic acid ester in order to impart polarity to the obtained acrylic polymer.
Further, as a crosslinkable monomer, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-
Methylol (meth) acrylamide etc. may be used together. Furthermore, if desired, other copolymerizable monomers such as vinyl acetate and styrene may be used in combination to the extent that the adhesive property of the (meth) acrylic acid ester polymer is not impaired.

The glass transition temperature of the polymer containing acrylic acid ester or methacrylic acid ester as a main component is not particularly limited, but is usually about -90 to 0 ° C, preferably -80 to -10 ° C. Is good. If the glass transition temperature is higher than 0 ° C, the tack tends to decrease, and if the glass transition temperature is lower than -90 ° C, the adhesive force tends to decrease.

The method for producing the acrylic polymer is as follows:
Various known methods may be adopted, and for example, a radical polymerization method such as a bulk polymerization method, a solution polymerization method or a suspension polymerization method can be appropriately selected. As the radical polymerization initiator, various known azo and peroxide type initiators can be used, and the reaction temperature is usually about 50 to 85 ° C. and the reaction time is about 1 to 8 hours. A polar solvent such as ethyl acetate is generally used as the solvent for the acrylic polymer, and the solution concentration is usually 40 to
It is set to about 60% by weight.

The tackifying resin of the acrylic pressure-sensitive adhesive composition of the present invention is obtained by reacting a resin acid containing a resin acid dimer and a polyhydric alcohol, and has a softening point of more than 150 ° C. It is essential to use a resin acid ester having a temperature of 185 ° C. or lower. The softening point is preferably 155 to 165 ° C. Softening point is 150 ° C
In the following cases, the high-temperature adhesive strength of the acrylic pressure-sensitive adhesive composition tends to decrease, and when the softening point exceeds 185 ° C., the tackiness of the acrylic pressure-sensitive adhesive composition at room temperature, the acrylic Compatibility with the system polymer tends to decrease.

The resin acid dimer is usually referred to as a polymerized rosin, and includes mainly dimerized resin acid monomers such as gum rosin, wood rosin and tall oil rosin. The method for producing the resin acid dimer is not particularly limited, and a known method can be adopted. For example, a resin acid monomer such as rosin contains a catalyst such as sulfuric acid, hydrogen fluoride, aluminum chloride, or titanium tetrachloride. Examples include a method of reacting in a solvent such as toluene or xylene at a temperature of about 40 to 160 ° C. for about 1 to 5 hours. The ratio of the resin acid dimer in the obtained reaction product varies depending on the reaction temperature, the reaction time, etc., and when the resin acid dimer alone obtained by completely dimerizing the resin acid monomer is obtained, unreacted resin acid A mixture of a monomer and a resin acid dimer may be obtained in some cases, but in the present invention, a resin acid containing a resin acid dimer can be used in any of the above cases. Further, since the resin acid containing the resin acid dimer of the present invention is reacted with a polyhydric alcohol to form a tackifier resin having a high softening point, the content of the resin acid dimer in the reaction product is 60. It is preferably at least wt%.

Specific examples of the resin acid containing such a resin acid dimer include tall oil-based polymerized rosin (trade name "SilvaTac 140", manufactured by Arizona Chemical Co., Ltd.), wood-based polymerized rosin (product name "Dimalex"). , Manufactured by Hercules Co., Ltd., and gum-based polymerized rosin.

In preparing the resin acid containing the resin acid dimer to be reacted with the polyhydric alcohol of the present invention, the resin acid dimer alone as the reaction product, or the unreacted resin acid monomer and the resin are used. A mixture with an acid dimer can be used as it is, or a resin acid monomer can be further added to these reaction products to prepare a resin acid containing the resin acid dimer of the present invention. The proportion of the resin acid dimer is preferably 60% by weight or more.

The polyhydric alcohol may be appropriately selected in consideration of the molecular weight and softening point of the resin acid ester which is a tackifier resin having a high softening point to be obtained, and examples thereof include ethylene glycol, diethylene glycol and triethylene glycol. Examples thereof include dihydric alcohols, trihydric alcohols such as glycerin, and tetrahydric or higher alcohols such as pentaerythritol, dipentaerythritol, and polyglycerin, and these can be used alone or in combination of two or more.

As a method for producing the resin acid ester, an ordinary esterification reaction may be adopted. For example, a resin acid containing a resin acid dimer and a polyhydric alcohol may be used in the presence or absence of a solvent to give 250 It suffices to employ a method of performing a heat dehydration reaction at about 280 ° C for about 1 to 8 hours. Examples of the solvent include aromatic solvents such as benzene, toluene and xylene.

The charging ratio of the resin acid containing the resin acid dimer and the polyhydric alcohol is not particularly limited, and the acid value of the obtained resin acid ester may be adjusted to about 30 or less. Usually, it is preferable to use the polyhydric alcohol in an amount having 1 to 2 equivalents of hydroxyl groups with respect to the carboxyl group equivalent of the resin acid containing the resin acid dimer.

The composition ratio of the acrylic pressure-sensitive adhesive composition of the present invention is, in terms of solid content, about 2 to 40 parts by weight of a tackifying resin having a high softening point with respect to 100 parts by weight of an acrylic polymer. It is preferable to use it by mixing in a ratio. Particularly preferred is 7 to 15 parts by weight. When the addition amount of the tackifying resin is less than 2 parts by weight, it becomes difficult to impart a sufficient high temperature adhesive force, and when it exceeds 40 parts by weight, not only the adhesive force is lowered but also the tackiness agent becomes hard and tacky. Also decreases, which is not preferable.

The acrylic pressure-sensitive adhesive composition of the present invention further comprises a cross-linking agent such as a polyisocyanate compound, a polyamine compound, a melamine resin, a urea resin and an epoxy resin, in addition to the acrylic polymer and the tackifying resin. By adding them, the cohesive force and heat resistance can be further improved. Among these crosslinking agents, it is particularly preferable to use a polyisocyanate compound, and specific examples thereof include 1,6-hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, 4,4. -Various known compounds such as diphenylmethane diisocyanate can be used.

Further, the acrylic pressure-sensitive adhesive composition of the present invention may appropriately contain a filler, an antioxidant, an ultraviolet absorber and the like, if necessary. The acrylic pressure-sensitive adhesive composition of the present invention can also be used in combination with various known tackifying resins within the range not departing from the object of the present invention.

[0023]

According to the present invention, there is provided an acrylic pressure-sensitive adhesive composition which satisfies required properties such as cohesive strength and adhesive strength and is excellent in both adhesive strength at room temperature and adhesive strength at high temperature. Can be provided. The acrylic pressure-sensitive adhesive composition of the present invention is particularly excellent in adhesion to polyolefin at room temperature and high temperature, and is used, for example, in a place exposed to high temperatures such as an engine part of an automobile, weak electricity, and a car body of an automobile. It is preferably used for labels, sheets, adhesive tapes, double-sided adhesive tapes and the like.

[0024]

EXAMPLES The present invention will be described in more detail with reference to production examples, examples and comparative examples, but the present invention is not limited to these examples. In the examples, all parts and% are by weight unless otherwise specified.

Production Example 1 (Production Example of Acrylic Polymer) After charging 90 parts of ethyl acetate into a reactor equipped with a stirrer, a cooling pipe, a dropping funnel and a nitrogen introducing pipe, the temperature in the system was kept under a nitrogen stream. The temperature was raised to about 80 ° C. Then
Preliminarily butyl acrylate 48.5 parts, acrylic acid 2
About 28.5 parts of ethylhexyl, 3 parts of acrylic acid, 0.2 part of benzoyl peroxide, and 10 parts of ethyl acetate.
It took 4 hours to add dropwise to the system, and the temperature was kept at the same temperature for 1 hour to complete the polymerization reaction to obtain an acrylic polymer having a solid content of 50%. The glass transition temperature of the polymer was -61 ° C.

Production Example 2 (Production Example of Acrylic Polymer) Solid content was exactly the same as in Production Example 1 except that the mixing ratio of the acrylic monomer in Production Example 1 was changed to 97 parts of butyl acrylate and 3 parts of acrylic acid. 50% acrylic polymer was obtained. The glass transition temperature of the polymer was -58 ° C.

Production Example 3 (Production of tackifying resin having a high softening point) 100 parts of gum-type polymerized rosin containing 66% of resin acid dimer in a reactor equipped with a stirrer, a cooling pipe, a water divider and a nitrogen introducing pipe. (Resin acid consisting of 34 parts of gum rosin and 66 parts of resin acid dimer of gum rosin) and 14 parts of pentaerythritol were charged, and the system temperature was adjusted to 2 under nitrogen gas flow.
Heated to 50 ° C. After reacting for 2 hours at the same temperature, the temperature was further raised to 280 ° C. and reacted for 7 hours at the same temperature. Then, the low boiling fraction was removed under reduced pressure to obtain pentaerythritol ester of resin acid (tackifying resin). The softening point was 155.0 ° C., the acid value was 13.3, and the color tone (Gardner) was 11.

Production Examples 4 to 7 (Production of Tackifying Resin with High Softening Point) The same procedure as in Production Example 2 was repeated except that the charged amounts of the resin acid and the polyhydric alcohol were changed as shown in Table 1. The constants of the obtained tackifier resin are shown in Table 1.

[0029]

[Table 1]

Example 1 80 parts of the acrylic polymer obtained in Production Example 1 (in terms of solid content) and 20 parts of the resin acid ester (tackifying resin) obtained in Production Example 3 were sufficiently kneaded, and then polyisocyanate was used. 2.5 parts of a compound (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to obtain a cross-linked acrylic pressure-sensitive adhesive composition. The crosslinked acrylic pressure-sensitive adhesive composition obtained was applied to a polyethylene film having a thickness of 38 μm by a dice type applicator so that the dry film thickness was about 30 μm, and then the solvent in the adhesive composition was removed. Then, a tape having a paste thickness of 30 μm was prepared, and various tests were conducted by the following methods. The results of the performance test are shown in Table 3.

Examples 2 to 5 In the same manner as in Example 1, except that the compounding amounts or kinds of the acrylic polymer and the resin acid ester (tackifying resin) in Example 1 were changed as shown in Table 2. Various crosslinked acrylic pressure-sensitive adhesive compositions were obtained. Using the obtained cross-linked acrylic pressure-sensitive adhesive composition, a performance test tape was prepared in the same manner as in Example 1 and a performance test was conducted. The results of the performance test are shown in Table 3.

Comparative Examples 1 to 4 In the same manner as in Example 1, except that the amounts or kinds of the acrylic polymer and the resin acid ester (tackifying resin) were changed as shown in Table 2 in Example 1. Various crosslinked acrylic pressure-sensitive adhesive compositions were obtained. Using the obtained cross-linked acrylic pressure-sensitive adhesive composition, a performance test tape was prepared in the same manner as in Example 1 and a performance test was conducted. The results of the performance test are shown in Table 3.

[Performance Test of Tape] The tapes obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were left to stand for 7 days for aging, and the performance was evaluated by the following test methods.

(Adhesive strength at room temperature): Tape obtained (25 m
m × 100 mm) was attached to a polypropylene plate, and a 180 ° peel strength (Kg / 25 mm) was measured under the conditions of 20 ° C. and 300 mm / min using a universal tensile tester.

(High temperature adhesive strength): The obtained tape (25 m)
m × 100 mm) was attached to a polypropylene plate, and the 180 ° peel strength (Kg / 25 mm) under conditions of 80 ° C. and 300 mm / min was measured using a universal tensile tester.

(Cohesive force): Obtained tape (25 mm ×
25 mm) is attached to a stainless steel plate and 1 kg at 40 ° C.
A load was applied, and the distance (mm) after 1 hour was measured.

(High temperature cohesive strength): The obtained tape (20 m
m × 20 mm) is attached to a stainless steel plate and it is 1k at 80 ° C.
The load (g) was applied and the time (minutes) until the weight fell was measured.

(Tack): J. J. described in JIS Z 0237. It was measured by the Dow method under the conditions of an inclination angle of 30 degrees and a measurement temperature of 20 ° C. The numbers in Table 3 are the ball numbers. Indicates.

[0039]

[Table 2] In the table, "A125" is a rosin ester (trade name A-12
5 represents Arakawa Chemical Industry Co., Ltd.

[0040]

[Table 3]

Claims (2)

[Claims] 1. A solvent-type acrylic pressure-sensitive adhesive composition containing an acrylic polymer and a tackifying resin, wherein the tackifying resin comprises a resin acid dimer and a polyhydric alcohol. An acrylic pressure-sensitive adhesive composition, characterized in that it is a resin acid ester having a softening point of more than 150 ° C. and 185 ° C. or less. 2. The acrylic polymer 100 in terms of solid content.
The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the tackifying resin is blended in an amount of 2 to 40 parts by weight with respect to parts by weight.