JPH06207151A - Acrylic pressure-sensitive adhesive composition an double-coated tape - Google Patents

Abstract

PURPOSE:To obtain an acrylic pressure-sensitive adhesive composition having excellent tack characteristics to a low-polarity material to be bonded, having excellent cohesive force at high temperature by blending a (meth)acrylic copolymer comprising a specific (meth)acrylic acid alkyl ester as a main component with a tackifier resin. CONSTITUTION:(A) A (meth)acrylic copolymer consisting essentially of a 2-15C alkyl-containing (meth)acrylic acid alkyl ester comprising >=30wt.% of a >=8C alkyl-containing (meth)acrylic acid alkyl ester is blended with (B) a tackifier resin composed of (i) rosin or its derivative and (ii) a hydrogenated petroleum resin in the blending ratio of 10<=(component (ii)X100)/(components (i+ii))<=40% to give the objective composition. For example, ethyl (meth)acrylate is preferable as the composition A and hydrogenated rosin as the component B. A double coated tape can be produced by using the composition.

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 composition and a double-sided tape using the pressure-sensitive adhesive composition. The present invention relates to an acrylic pressure-sensitive adhesive composition that is excellent and can exhibit sufficient adhesive properties even at high temperatures, and a double-sided tape using the pressure-sensitive adhesive composition.

[0002]

2. Description of the Related Art In recent years, applications of pressure-sensitive adhesive (hereinafter referred to as pressure-sensitive adhesive) compositions have been widespread, and the properties required thereof have tended to become more sophisticated. Acrylic pressure-sensitive adhesives have been developed and used for various purposes as pressure-sensitive adhesives having higher cohesive strength, weather resistance, and solvent resistance than rubber-based pressure-sensitive adhesives.

An acrylic copolymer has a tackiness by itself and can be used as an adhesive without adding a tackifying resin. However, for an adherend having a low polar surface such as polyethylene or polypropylene, It was difficult for the acrylic copolymer alone to exhibit good adhesive properties. In particular, if the copolymerization amount of the carboxyl group-containing monomer in the acrylic copolymer is increased for the purpose of improving the adhesive property to the polar surface of a metal plate or the like, the adhesiveness to polyethylene and polypropylene is practically acceptable. It is acknowledged that it will be lowered beyond what is possible. Therefore, as with other pressure-sensitive adhesives, a tackifying resin is usually added to improve the adhesion to a low-polar adherend.

For example, in JP-A-64-60677, a styrene-based polymer and a hydrogenated petroleum resin are used as a tackifying resin to be added to an acrylic copolymer, but the adhesiveness to polyolefin is still low. Not improved enough.

[0005]

In particular, when such a tackifying resin is added, the temperature dependence of the adhesive strength becomes large, and at high temperature, the adhesive strength and cohesive strength are rather higher than those of the acrylic copolymer alone. There were times when it fell. Therefore,
Conventional acrylic pressure-sensitive adhesive compositions are superior in adhesive properties at high temperatures as compared with rubber-based ones, but they exhibit sufficient adhesive properties even at high temperatures after ensuring adhesive strength at room temperature. I was not satisfied in terms.

The object of the present invention is to solve the above-mentioned conventional problems and to provide an acrylic pressure-sensitive adhesive which has excellent adhesive properties to an adherend having a low polarity surface and can exhibit sufficient adhesive properties even at high temperatures. A double-sided tape using the composition and the pressure-sensitive adhesive composition.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present inventor has made extensive studies as to a tackifying resin to be blended with an acrylic copolymer, and as a result, conventionally, it was caused by the low polarity of the resin itself. Since the compatibility with the acrylic copolymer is poor, hydrogenated petroleum resin, which was considered unsuitable for acrylic pressure-sensitive adhesives, and rosin or a derivative thereof were used in combination as a tackifying resin. We have found a surprising fact that conventional problems can be solved. The present invention is
It was completed based on such new knowledge.

That is, according to the present invention, a tackifying resin is blended with a (meth) acrylic copolymer containing a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 15 carbon atoms as a main component. An acrylic pressure-sensitive adhesive composition, wherein among (meth) acrylic acid alkyl esters,
The proportion of the (meth) acrylic acid alkyl ester having an alkyl group having 8 or more carbon atoms is 30% by weight or more, and the tackifying resin comprises rosin or its derivative (a) and hydrogenated petroleum resin (b). Therefore, the compounding ratio of rosin or its derivative (a) and hydrogenated petroleum resin (b) is 1
0 ≦ ((b) × 100) / ((a) + (b)) ≦ 40
(% By weight). In the present specification, (meth) acrylic means acrylic and methacrylic.

The (meth) acrylic copolymer used in the present invention has an alkyl group having 2 to 15 carbon atoms, and the proportion of those having an alkyl group having 8 or more carbon atoms is 30% by weight or more. A certain (meth) acrylic acid alkyl ester is used as the main component. Therefore, these (meth) acrylic copolymers can be obtained by polymerizing or copolymerizing these esters alone or in combination with a monomer copolymerizable therewith. As the polymerization method, known methods such as bulk polymerization, solution polymerization, dispersion polymerization and emulsion polymerization can be adopted. As a method for initiating the polymerization, a known method can also be adopted, for example, a method using a thermal polymerization initiator such as benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, benzoin, benzoin methyl ether, benzophenone, etc. It is possible to arbitrarily select a starting method by ultraviolet irradiation using the above photopolymerization initiator, a method by electron beam irradiation, or the like. The weight average molecular weight of the obtained acrylic copolymer is preferably 200,000 or more.

Examples of the (meth) acrylic acid alkyl ester as the main component include ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, sec. -Butyl (meth) acrylate, t-butyl (meth) acrylate, n-octyl (meth) acrylate, iso-octyl (meth) acrylate, 2
-Ethylhexyl (meth) acrylate, nonyl (meth) acrylate, dodecyl (meth) acrylate, etc. are used alone or in combination of two or more. When the number of carbon atoms of the alkyl group is out of the range of 2 to 15, the characteristics of the pressure-sensitive adhesive are impaired, which is not preferable.

The proportion of the (meth) acrylic acid ester having an alkyl group having 8 or more carbon atoms in the (meth) acrylic acid alkyl ester is 30% by weight or more. If it is less than 30% by weight, the polarity of the acrylic copolymer itself becomes too high, the compatibility with the hydrogenated petroleum resin becomes poor, and the tack at room temperature becomes insufficient, which is not suitable.

The monomer copolymerizable with the above-mentioned main component (meth) acrylic acid alkyl ester is (meth)
Unsaturated acids such as acrylic acid, itaconic acid, 2- (meth) acrylic acid propane sulfonic acid, (meth) acryloxyethyl phosphate, and 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, etc. Examples include polar monomers such as hydroxyl group-containing monomers. These polar monomers are effective as a component that enhances the cohesive force of the pressure-sensitive adhesive.

In addition to the above polar monomers, methyl (meth)
It is also possible to use a monomer such as acrylate, styrene, vinyl acetate, (meth) acrylonitrile, or (meth) acrylamide that gives a polymer having a high glass transition point.

Among the rosin and its derivative (a) used as the tackifying resin in the present invention, as the rosin derivative, a partially disproportionated or disproportionated rosin, a hydrogenated rosin, a maleic acid-modified rosin, a polymerized rosin, In addition to formaldehyde-modified rosin, these metal salts and other esters with diethylene glycol, glycerin, pentaerythritol and the like are included.

The hydrogenated petroleum resin (b) used as a tackifying resin in the present invention is a hydrogenated C9 petroleum resin obtained by cationically polymerizing a C9 fraction obtained by cracking naphtha. Or a hydrogenated petroleum resin obtained by thermal polymerization of a C5 fraction mainly containing cyclopentadiene or dicyclopentadiene derived from the C5 fraction, and means an alicyclic petroleum resin. Specifically, for example, the product name “Arcon” series manufactured by Arakawa Chemical Co., Ltd. may be mentioned.

The acrylic pressure-sensitive adhesive composition of the present invention comprises the above-mentioned acrylic copolymer compounded with rosin or its derivative (a) and hydrogenated petroleum resin (b).
The blending amount is 100% acrylic copolymer in terms of solid content.
It is preferably 5 to 40 parts by weight with respect to parts by weight.
If the amount is less than 5 parts by weight, the effect of improving the peel strength may be insufficient. If it exceeds 40 parts by weight, the cohesive force, tack, etc. may decrease.

Further, the compounding ratio of rosin or its derivative (a) and hydrogenated petroleum resin (b) is 10≤ in terms of solid content.
((B) × 100) / ((a) + (b)) ≦ 40 (wt%). If the compounding ratio is less than 10% by weight,
Adhesive properties to adherends having a low polarity surface, especially peel strength, are hardly improved. On the other hand, if it exceeds 40% by weight, the compatibility with the acrylic copolymer is lowered, so that the tack at room temperature and the adhesive property are extremely deteriorated.

The pressure-sensitive adhesive composition of the present invention has the above (meth)
An acrylic copolymer and a tackifying resin are contained as essential components, but a crosslinking agent can be contained in order to improve cohesive force. As such a cross-linking agent, a conventionally known one can be used, for example, an isocyanate cross-linking agent,
Examples thereof include a melamine-based crosslinking agent, an epoxy-based crosslinking agent, and a peroxide-based crosslinking agent. Further, the pressure-sensitive adhesive composition of the present invention,
If necessary, various conventionally known additives such as plasticizers, softeners, fillers, pigments, dyes and the like can be added.

[0019]

In the present invention, the (meth) acrylic copolymer is
By blending a tackifying resin comprising a rosin or its derivative (a) and a hydrogenated petroleum resin (b), the adhesive property to an adherend having a low polar surface at room temperature is excellent, and the physical properties are lowered even at high temperature. The amount of the adhesive composition is small. Conventionally, it has been said that a tackifying resin having excellent compatibility with a (meth) acrylic copolymer is preferable, but in the case of this kind of a pressure-sensitive adhesive composition, a crosslinking treatment is performed in a film forming process or the like. Is common. At this time, a crosslinked portion and an uncrosslinked portion are usually formed because the (meth) acrylic copolymer has a molecular weight distribution and the high molecular weight polymer is more easily crosslinked. Here, when the conventional tackifying resin having excellent compatibility is used, the tackifying resin and the (meth) acrylic copolymer are uniformly mixed,
Since the tackifying resin is uniformly present in the crosslinked portion and the non-crosslinked portion, under high temperature, all the portions including the crosslinked portion tend to be plasticized uniformly, and this plasticization softens the whole. , Which in turn causes a decrease in cohesive strength,
As a result, it is considered that the adhesive properties deteriorate at high temperatures.

On the other hand, in the present invention, hydrogenated petroleum resin, which has been considered to have poor compatibility with the acrylic copolymer due to the low polarity of the resin itself, is used as the tackifying resin. . Such hydrogenated petroleum resin is used in combination with the rosin or the derivative (a) to make it compatible with the acrylic copolymer. Since this tackifier resin lacks uniform mixing properties with the (meth) acrylic copolymer, it is considered that the tackifier resin is less likely to enter the crosslinked portion. As a result, it is considered that even under high temperature, plasticization at the crosslinked portion is less likely to occur, and the deterioration of the adhesive property is lessened.

[0021]

Example 1 In a separable flask equipped with a cooling tube, a stirrer and a thermometer, 97 parts by weight of 2-ethylhexyl acrylate and 3 parts by weight of acrylic acid were added, and the total amount of monomers was in a weight ratio to ethyl acetate. , 55/45 to dissolve in ethyl acetate, and 0.062 parts by weight of benzoyl peroxide as a polymerization initiator was added to the resulting solution. This mixture was stirred and polymerized at 80 ° C. for 8 hours under a nitrogen atmosphere to obtain an adhesive solution, that is, an acrylic copolymer resin solution.

To this acrylic copolymer resin solution, N, N'-hexamethylene-1,6-bis (1
-Aziridinecarboxamide) (HDU) 0.10
In addition to blending parts by weight, the tackifying resin shown in Table 1 is
The adhesive composition of Example 1 was prepared by blending in the predetermined ratio shown in.

The pressure-sensitive adhesive composition obtained as described above was coated on a release paper so that the thickness after drying was 75 μm, and then dried at a temperature of 110 ° C. for 5 minutes. Then, the pressure-sensitive adhesive composition on the release paper was placed on a non-woven fabric and pressure-bonded with a roll. This operation was also performed on the other side of the nonwoven fabric to obtain a nonwoven fabric-based double-sided tape.

Examples 2 and 3 Nonwoven fabric-based double-sided tapes were obtained in the same manner as in Example 1 except that the kind and amount of tackifying resin were changed as shown in Table 1.

Example 4 Both sides of the non-woven fabric base material obtained in the same manner as in Example 1 except that the monomer composition of the acrylic copolymer was n-butyl acrylate / 2-ethylhexyl acrylate / acrylic acid = 57/40/3. Got the tape.

Examples 5 and 6 Nonwoven fabric-based double-sided tapes were obtained in the same manner as in Example 4, except that the kind and amount of tackifying resin were changed as shown in Table 1.

Comparative Examples 1 to 3 As shown in Table 1, a non-woven fabric-based double-sided tape was obtained in the same manner as in Example 1 except that the type or amount of tackifying resin was changed outside the range of the present invention. .

Comparative Example 4 By setting the composition of the acrylic copolymer monomer to n-butyl acrylate / 2-ethylhexyl acrylate / acrylic acid = 72/25/3, the composition has an alkyl group having 8 or more carbon atoms. A non-woven fabric-based double-sided tape was obtained in the same manner as in Example 1 except that the proportion of the (meth) acrylic acid ester was 25% by weight. The adhesive property of the obtained non-woven fabric-based double-sided tape was evaluated as follows.

(1) SP adhesive strength According to JIS Z1528, a tape was attached to a SUS304 plate with a width of 20 mm, left at 23 ° C. for 20 minutes, and then the 180 ° peel strength was measured. Pulling speed is 3
It was set to 00 mm / min.

(2) Adhesive strength of polypropylene (PP) According to JIS Z1528, tape 20 m on PP plate
18 m width after bonding and leaving at 23 ℃ for 20 minutes
The 0 ° peel strength was measured. Pulling speed is 300mm /
It was set to min.

(3) Holding power (80 ° C.) According to JIS Z1528, at room temperature, SUS304
Adhere tape to the board with a size of 20 × 20mm, and at 2 ℃ at 2 ℃
After leaving it for 0 minutes, leave it in the system at 80 ° C for 20 minutes, and
The load (kg) was applied, and the shift (or drop time) after 1 hour was measured.

(4) Polypropylene (PP) 90 ° constant load peeling retention force (60 ° C.) At room temperature, a tape was attached to a PP plate with a width of 20 mm,
After leaving it for 20 minutes at 23 ° C., it was allowed to stand in a system of 60 ° C. for 20 minutes, a load of 80 g was applied, and it was peeled in the direction of 90 °, and the peeling length per unit time was measured.

[0033]

[Table 1]

As is clear from Table 1, the double-sided tapes using the pressure-sensitive adhesives of Examples 1 to 6 according to the present invention are excellent in polypropylene (PP) adhesive force as well as SP adhesive force,
It also shows excellent adhesive properties for polyolefins. Also, the holding power at 80 ° C. and the PP constant load peeling holding power at 60 ° C. are superior to those of Comparative Examples 1 to 4, and it can be seen that sufficient adhesive properties are exhibited even at high temperatures.

[0035]

As described above, the pressure-sensitive adhesive composition of the present invention has a rosin or its derivative excellent in compatibility with an acrylic copolymer and an acrylic copolymer due to the low polarity of the resin itself. On the other hand, by using a hydrogenated petroleum resin with poor compatibility, it exhibits excellent adhesive properties to various adherends having a low polarity surface such as polyethylene and polypropylene at room temperature, and the conventional acrylic adhesive It exhibits a small temperature-dependent adhesive strength that is not found in. In particular, the pressure-sensitive adhesive composition has excellent cohesive strength at high temperatures.

Further, according to the present invention, the resin-incompatible portion existing in the pressure-sensitive adhesive composition serves as a nucleus, and stress relaxation can be positively promoted in the system of the pressure-sensitive adhesive composition.
Peeling resistance is dramatically improved.

The double-sided tape of the present invention is provided with an adhesive layer made of the above-mentioned adhesive composition and exhibits excellent adhesive properties to polyethylene, polypropylene and the like, and sufficient adhesive properties even at high temperatures. Can be demonstrated.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C09J 193: 04 7415-4J 157: 02) 7415-4J

Claims (2)

[Claims] 1. An acrylic pressure-sensitive material obtained by blending a tackifying resin with a (meth) acrylic copolymer using a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 15 carbon atoms as a main component. The adhesive composition, wherein the proportion of the (meth) acrylic acid alkyl ester having an alkyl group having 8 or more carbon atoms in the (meth) acrylic acid alkyl ester is 30% by weight or more,
The tackifying resin comprises rosin or its derivative (a) and hydrogenated petroleum resin (b), and the compounding ratio of the resin (a) and the resin (b) is 10 ≦ ((b) × 100) / An acrylic pressure-sensitive adhesive composition in which ((a) + (b)) ≦ 40 (wt%). 2. A double-sided tape comprising a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition according to claim 1.