JPH0784579B2 - Acrylic pressure sensitive adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an acrylic pressure-sensitive adhesive composition, and more particularly to an acrylic pressure-sensitive adhesive composition having excellent adhesive properties to polyolefin.

Conventional technology Pressure-sensitive adhesive compositions applied to labels, adhesive tapes, double-sided adhesive tapes, etc. are required to have excellent colorlessness, transparency, weather resistance, etc. in consideration of their use environment. It Therefore, a pressure-sensitive adhesive composition containing an acrylic polymer excellent in the required performance as a base polymer component has been conventionally awarded.

The tackifying resin to be blended in the acrylic pressure-sensitive adhesive composition is a rosin ester, C9 petroleum resin, or the like, or a so-called pure monomer resin typified by a styrene copolymer (usually used monomer purity Is high and the color tone of the produced resin is colorless).

The acrylic pressure-sensitive adhesive composition using a rosin ester among the above-mentioned known tackifying resins exhibits relatively excellent adhesive force to polyolefin, that is, peeling strength from an adherend, but on the other hand, it has an acrylic feel. It has the disadvantage of reducing the colorlessness and weather resistance that are characteristic of pressure-sensitive adhesive compositions. Also,
When a C9 petroleum resin is used, there is a problem that the colorlessness and weather resistance are not sufficient and the peel strength with respect to polyolefin is poor. Further, even when a pure monomer resin is used, there is a problem that the peel strength to polyolefin is insufficient.

Problems to be Solved by the Invention The present invention is intended to solve the above-mentioned conventional problems. That is, the present invention not only satisfies the required performances such as colorlessness, transparency, and weather resistance, but also has a peel strength for adherends such as polyolefin, which has been a drawback of acrylic pressure-sensitive adhesives. An object of the present invention is to provide a significantly improved acrylic pressure-sensitive adhesive composition.

Means for Solving the Problems In order to achieve the above-mentioned object, the inventors of the present invention have made earnest studies on a tackifying resin to be blended with an acrylic base polymer. As a result, hydrogenated petroleum resins and hydrogenated terpene resins used as tackifying resins for hot-melt adhesives have poor compatibility with acrylic base polymers due to the low polarity of these resins. Therefore, a composition with excellent transparency could not be obtained at all, and despite the conventional wisdom that it was not suitable for acrylic pressure-sensitive adhesives, these hydrogenated compounds were used as tackifying resins for acrylic base polymers. When a resin and a styrene-based resin, which is a pure monomer resin, are used in combination, the surprising fact that the above-mentioned problems can be solved while maintaining excellent transparency was discovered. The present invention has been completed based on this unique finding.

That is, the present invention relates to an acrylic pressure-sensitive adhesive composition prepared by blending an acrylic polymer with a tackifying resin, wherein the tackifying resin is (a) 100 to 70% by weight of styrene and a fatty acid having 5 or more carbon atoms. A styrene-based polymer having a monomer composition of 0 to 30% by weight of a group monoolefin, and (b) at least one resin selected from hydrogenated petroleum resins and hydrogenated terpene resins. The present invention relates to an acrylic pressure-sensitive adhesive composition.

In the composition of the present invention, an acrylic polymer is used as a base polymer. The polymer is not particularly limited, and various known homopolymers or copolymers conventionally known for pressure-sensitive adhesive compositions of this type can be used as they are. As the monomer, various acrylic acid esters and / or methacrylic acid esters (hereinafter abbreviated as (meth) acrylic acid ester) can be used, and specifically (meth)
Examples thereof include methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate. They may be used alone or in combination. Further, in order to impart polarity to the obtained polymer, a small amount of (meth) acrylic acid can be used instead of part of the (meth) acrylic acid ester. Furthermore, if desired, a copolymerizable monomer such as vinyl acetate or styrene may be used in combination to the extent that the adhesive property of the (meth) acrylic acid ester polymer is not impaired. Further, in order to impart cross-linking reactivity to the acrylic polymer, (meth) acrylic acid glycidyl ester, N-methylol (meth) acrylamide and the like may be used in combination. The glass transition temperature of the polymer containing these acrylic acid ester and methacrylic acid ester as a main component is not particularly limited, but is usually -70 ° C to 0 ° C, preferably -60 to-
It is recommended that the temperature range be 10 ° C. If it exceeds 0 ° C, the tack is remarkably lowered, which is not preferable. When the cross-linking reactive acrylic polymer is used, various known ones such as polyamine, polyisocyanate, melamine resin, urea resin, epoxy resin and polyvalent metal salt can be appropriately used as the cross-linking agent.

The method for producing the acrylic polymer is not particularly limited,
Various known methods can be adopted. For example, bulk polymerization method,
It can be easily produced by appropriately selecting a radical polymerization method such as a solution polymerization method or a suspension polymerization method. As the radical polymerization initiator, various known azo type and peroxide type initiators can be used, and ordinary reaction conditions can be adopted.

In the composition of the present invention, as a tackifying resin, (a) a styrene-based polymer composed of 100 to 70% by weight of styrene and a monomer composition of 0 to 30% by weight of an aliphatic monoolefin having 5 or more carbon atoms (hereinafter, (Simply called styrene polymer),
(B) It is essential to use together with at least one resin selected from hydrogenated petroleum resin and hydrogenated terpene resin (hereinafter, simply referred to as hydrogenated resin). This achieves the object of the present invention.

Examples of styrenes that are the constituent monomers of the styrene-based polymer include styrene, α-methylstyrene, dimethylstyrene, vinyltoluene, and the like. Also,
The aliphatic monoolefin copolymerized with styrenes has 5 or more carbon atoms, preferably 8 to 15 carbon atoms. Specific examples of the olefin include diisobutylene,
Examples include triisobutylene, nonene, decene, polybutene, and the like, and these can be used alone or in combination. As the olefin, diisobutylene is preferable, and as the diisobutylene, an industrial product that is usually easily available 2,4,
A mixture of 4-trimethylpentene-1 and 2,2,4-trimethylpentene-2 can be preferably used. As the styrene-based polymer, any of a homopolymer of styrenes, a copolymer of styrenes and a copolymer of styrenes and the olefin can be used. When the olefin is copolymerized, the amount used is up to about 30% by weight in the used monomers. The preferred monomer composition of the copolymer of styrene and the olefin is 95 to 70% by weight of styrene and 5 to 30% by weight of the olefin. When the amount of the olefin used is more than 30% by weight, the softening point of the obtained copolymer is lowered, which tends to lower the cohesive force of the adhesive, which is not preferable.

The styrene polymer is produced, for example, as follows. That is, styrene or an olefin and an aliphatic monoolefin are charged at a predetermined ratio, and the polymerization reaction is performed in the presence of a cationic polymerization catalyst such as titanium tetrachloride, tin tetrachloride, aluminum tetrachloride, boron trifluoride, activated clay and the like. It can be easily obtained. The reaction temperature is usually 30 to 100 ° C.
The reaction time is about 1 to 8 hours. The polymerization reaction may be carried out without a solvent, but may be carried out using a solvent such as an aromatic hydrocarbon. However, by adopting the above conditions, normally, it is colorless and transparent and the number average molecular weight is
Amorphous resin of 300 to 2000 can be obtained, but especially in the present invention, 3
Those of 50 to 1500 are preferable.

Among the hydrogenated resins, hydrogenated petroleum resin and hydrogenated C9 petroleum resin obtained by cationic polymerization of C9 fraction obtained by cracking naphtha, or C5 fraction mainly composed of cyclopentadiene or It is a hydrogenated petroleum resin obtained by thermal polymerization of dicyclopentadiene derived from the C5 fraction, and means an alicyclic hydrogenated petroleum resin. Here, in the C9 fraction, α-methylstyrene, vinyltoluene, vinylxylene, propenylbenzene, indene, methylindene, etc. are contained as polymerizable components,
Usually, the C9 fraction is available as a mixture of the polymerizable components.
The hydrogenation conditions for these petroleum resins are usually nickel,
A metal such as palladium, cobalt, ruthenium, platinum, rhodium, or an oxide thereof is used as a hydrogenation catalyst, and the conditions of a temperature of 200 to 300 ° C. and a pressure of 10 to 300 kg / cm ² are usually adopted.

Further, the hydrogenated terpene resin, α-pinene, β-pinene, terpene fractions such as dipentene aluminum chloride,
Hydrogenated terpene resin obtained by cationic polymerization using a Friedel-Crafts catalyst such as boron trifluoride,
Alternatively, it means a hydrogenated copolymer of a terpene fraction and styrene. As the hydrogenation conditions, the conditions of the petroleum resin can be adopted as they are.

Such hydrogenated resin is excellent in colorlessness, transparency, and weather resistance, and is used for hot melt adhesives and rubber-based pressure-sensitive adhesives, but as a tackifying resin for acrylic pressure-sensitive adhesives,
Never used before. This is because the transparency of the adhesive is significantly impaired due to its poor compatibility with the acrylic polymer as the base polymer. However, the present invention, by intentionally using a hydrogenated resin having such a defect in combination with a styrene resin which is a pure monomer resin, does not lower compatibility at all and therefore does not impair transparency, and polyolefin It is very specific in that it succeeded in significantly improving the peel strength against.

The acrylic pressure-sensitive adhesive composition of the present invention is obtained by blending the acrylic polymer with a styrene polymer and a hydrogenated resin, and the blending ratio of each component is not particularly limited. Usually, it is appropriately determined depending on the application in consideration of the transparency of the composition. That is, it is preferable that the tackifying resin, which is the total of the styrene polymer and the hydrogenated resin, is usually about 5 to 20 parts by weight based on 100 parts by weight of the acrylic polymer in terms of solid content. If the amount is less than 5 parts by weight, the effect of improving the peel strength will be insufficient, and if it exceeds 20 parts by weight, the cohesive force and the tack will be decreased, which is not preferable. Further, the compounding ratio of the styrene polymer and the hydrogenated resin is
In terms of solid content, the former: the latter is about 95: 5 to 10:90, preferably 95: 5 to 70:30. When the ratio of the former is less than 10, because the compatibility with the acrylic polymer decreases.
On the other hand, if the amount exceeds 95 parts by weight, the peel strength to polyolefin is hardly improved and neither is preferable.

The acrylic pressure-sensitive adhesive composition of the present invention does not have a cross-linking agent such as polyamine, polyisocyanate, melamine resin, urea resin, epoxy resin, polyvalent metal salt as an essential component, By doing so, it can be used for the purpose of further improving the cohesive force and heat resistance. The amount used is usually about 0.01 to 0.5% by weight based on the acrylic polymer. Further, as the cross-linking agent, a polyisocyanate compound is preferable because of its high reactivity, and specifically, 1,6-hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, 4 Various known compounds such as 4,4-diphenylmethane diisocyanate can be used. Further, in the acrylic pressure-sensitive adhesive composition of the present invention, a filler, an antioxidant, an ultraviolet absorber and the like can be appropriately used if necessary.

EFFECT OF THE INVENTION The acrylic pressure-sensitive adhesive composition of the present invention sufficiently satisfies the required performances such as colorlessness, transparency, and weather resistance, and further, the peel strength for adherends such as polyolefin is remarkably improved. There is. Therefore, a label, an adhesive tape, a double-sided adhesive tape, etc. to which this is applied can be suitably used for a wide range of adherends including polyolefin.

EXAMPLES Hereinafter, the present invention will be described more specifically 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 of Acrylic Polymer) After charging 100 parts of ethyl acetate into a reactor equipped with a stirrer, a cooling pipe, a dropping funnel and a nitrogen introducing pipe, the temperature inside the system was raised to about 80 ° C. did. Then, from a dropping funnel charged with a mixed solution consisting of 97 parts of butyl acrylate, 3 parts of acrylic acid and 0.2 part of benzoyl peroxide in advance, the mixed solution was dropped into the system under a nitrogen stream for about 3 hours. ,
Keep the temperature at the same temperature for an additional 1 hour to complete the polymerization reaction.
50% acrylic polymer was obtained with a yield of 99%. The glass transition temperature of the polymer was -36 ° C.

Production Example 2 (Production of Styrene Polymer) After charging 285 parts of styrene, 15 parts of diisobutylene and 260 parts of toluene into the same reactor as in Production Example 1, 0.6 parts while keeping the temperature at 30 ° C. under nitrogen stream. Of anhydrous aluminum chloride was added portionwise, and the mixture was polymerized at the same temperature for 2 hours. The temperature was further raised to 80 ° C. and the temperature was kept for 1 hour to complete the reaction. Then, the reaction solution was neutralized and the solvent was distilled off under reduced pressure to obtain a colorless and transparent styrene-diisobutylene copolymer with a yield of 96%.

The polymer had a number average molecular weight of 800 and a softening point of 80 ° C. The molecular weight was measured by GPC based on the polystyrene conversion method, and the softening point was measured by the ring and ball method.

Production Example 3 (Production of Styrene Polymer) After charging 300 parts of toluene into the same reactor as in Production Example 1, 300 parts of dimethylstyrene and 1.8 parts of boron trifluoride-etherate were separately charged from separate dropping funnels. Then, under a nitrogen stream, the mixture was added dropwise at the same temperature while maintaining the temperature at 0 ° C., and polymerization was carried out at the same temperature for 2 hours. Then, the reaction solution was neutralized and the solvent was distilled off under reduced pressure to obtain a colorless transparent dimethylstyrene polymer in a yield of 95%.

The polymer had a number average molecular weight of 400 and a softening point of 83 ° C.

Example 1 90 parts of the acrylic polymer obtained in Production Example 1 (solid content conversion),
After sufficiently kneading 9.5 parts of the styrene polymer obtained in Production Example 2 and 0.5 part of C9 hydrogenated petroleum resin (manufactured by Arakawa Chemical Industry Co., Ltd., trade name "ALCON M-100") as a hydrogenated resin, 2.7 parts of an isocyanate compound (manufactured by Nippon Polyurethane Company, trade name "Coronate L") was added to obtain a cross-linked acrylic pressure-sensitive adhesive. The composition is shown in Table 1. The adhesive was applied to a polyethylene film having a thickness of 38 μ with a dice type applicator, and then the solvent was removed to prepare an adhesive tape having a thickness of 30 μ.

<Performance Test of Adhesive Tape> After being applied as described above and aged for 3 days, it was evaluated by the following test methods.

(1) Weather resistance test The pressure-sensitive adhesive tape obtained above was irradiated with ultraviolet rays for 24 hours at an irradiation distance of 40 cm with an ultraviolet lamp (mercury lamp for fading test manufactured by Toshiba Corporation, model H-400V) for 24 hours. The transparency was visually evaluated. The evaluation criteria are as follows.

Degree of coloring ○ …… Colorless △ …… Slightly yellow × …… Yellow transparency ○ …… Completely transparent △ …… Slightly turbid × …… Opaque (2) Peel strength (adhesive strength) Adhesive tape for various adherends Then, the 180 ° peel strength (kg / inch) at 20 ° C. was measured using a universal tensile tester.

(3) Holding power Adhesive tape is attached to a stainless steel plate (25 mm x 25 mm), 40
A load of 1 kg was applied at ℃, and the distance (mm) after 1 hour was measured.

(4) Tuck Roll a 11/32 inch diameter bearing ball from an inclined plate with an inclination angle of 22 ° with an approach distance of 15 cm, and the distance (cm) until it stops rolling on the adhesive tape placed on a flat surface in an atmosphere of 20 ° C. It was measured. The test results are shown in Table 2.

Examples 2 to 4 The same procedure as in Example 1 was carried out except that the compounding ratio of the styrene polymer and the C9 hydrogenated petroleum resin was changed as shown in Table 1. A pressure-sensitive adhesive was obtained. The adhesive was evaluated as in Example 1. The results are shown in Table 2.

Example 5 In Example 2, the hydrogenated resin “Alcon M-10” was used.
The same procedure is performed except that "0" is replaced with hydrogenated terpene resin ("Clearon M-105" manufactured by Yasuhara Yushi Kogyo Co., Ltd.),
A cross-linked acrylic pressure-sensitive adhesive was obtained. The composition is shown in Table 1. The adhesive was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Example 6 In Example 1, the styrene polymer was replaced with the dimethylstyrene polymer obtained in Production Example 3, and the compounding ratio of the polymer and the C9 hydrogenated petroleum resin was changed as shown in Table 1. In the same manner as above, various crosslinked acrylic pressure-sensitive adhesives were obtained. The adhesive was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Examples 1-2 A crosslinked acrylic pressure-sensitive adhesive was obtained in the same manner as in Example 1, except that the styrene polymer alone or the C9 hydrogenated petroleum resin alone was used as the tackifying resin. The composition is shown in Table 1. The adhesive was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Examples 3 to 4 In Example 1, instead of the C9-based hydrogenated petroleum resin "Alcon M-100", rosin ester (manufactured by Arakawa Chemical Industry Co., Ltd., trade name "Super Ester W" in turn) was used.
-100 "), C9 petroleum resin (manufactured by Nippon Petrochemical Co., Ltd., trade name" Nisseki Neopolymer L-90 "), but in the same manner as above to obtain a crosslinked acrylic pressure-sensitive adhesive. The composition is shown in Table 1. The adhesive was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 5 A crosslinked acrylic pressure-sensitive adhesive was obtained in the same manner as in Example 1, except that the tackifying resin was not used. The composition is shown in Table 1. The adhesive was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Claims (4)

[Claims] 1. An acrylic pressure-sensitive adhesive composition obtained by blending an acrylic polymer with a tackifying resin, wherein the tackifying resin comprises (a) 100 to 70% by weight of styrene and 5 carbon atoms.
A styrene-based polymer having a monomer composition of 0 to 30% by weight of the above aliphatic monoolefins, and (b) at least one resin selected from hydrogenated petroleum resins and hydrogenated terpene resins. A characteristic acrylic pressure-sensitive adhesive composition. 2. The number average molecular weight of the styrene polymer is 350 to 1.
The composition of claim 1 which is 500. 3. The composition according to claim 1 or 2, wherein the tackifying resin is compounded in an amount of 5 to 20 parts by weight based on 100 parts by weight of the acrylic polymer in terms of solid content. . 4. The compounding ratio between the polymer of (a) and the resin of (b), in terms of solid content, the former: the latter = 95: 5 to 10:90. The composition according to any of the above.