JPH04314776A - Pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To provide a pressure-sensitive adhesive which can be satisfactorily applied to a vulcanized rubber molding even when the molding is not subjected to conventional treatment such as buffing or priming. CONSTITUTION:This adhesive is prepared by combining at least two block copolymers each comprising styrene polymer blocks and isoprene polymer blocks and mixing the obtained mixed block copolymer as a base polymer with a tackifying resin.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive used for bonding vulcanized rubber molded products made of natural rubber, chloroprene rubber, EPT (ethylene-propylene-terpolymer) rubber, or the like.

0002

BACKGROUND OF THE INVENTION Vulcanized rubber molded products of this type are widely used as parts for automobiles, home appliances, OA equipment, and various industrial products.

However, these rubber molded products contain a large number of adhesion inhibiting substances such as various fillers, vulcanizing agents, and oil components as a compound, and in the process of vulcanizing the rubber molded products, the mold from the press mold is removed. Because a mold release agent such as silicone oil is used to improve separation, the adhesiveness of the molded product surface is poor.

Moreover, these vulcanized rubber molded products have high elasticity, so when they are attached to a curved surface, they are adhesively fixed under stress due to the elastic action. Due to this and the poor adhesiveness of the surface of the molded product, there was a problem that the molded product easily peeled off after being adhesively fixed.

For this reason, in the past, the surface of the vulcanized rubber molded product was first buffed, then washed with a solvent and coated with a primer, and then a film-like pressure-sensitive adhesive was bonded thereon. Therefore, methods such as adhesive fixation to other adherends have been adopted.

[0006]

[Problems to be Solved by the Invention] However, the above-mentioned processes such as buffing and primer application require a lot of man-hours, and there is a risk that the buffing powder and solvent will scatter, worsening the working environment. However, there was a problem in that the degree of buffing tends to vary, and this also causes variations in adhesive strength.

In view of the above-mentioned circumstances, the present invention has developed a pressure-sensitive material that can obtain sufficient adhesive strength without performing conventional treatments such as buffing and primer coating on vulcanized rubber molded products. The purpose is to provide adhesives.

[0008]

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the present inventors have found that by using a specific polymer as the main component of the adhesive, vulcanized rubber molded products can be made from conventional ones. The present invention was completed based on the knowledge that sufficient adhesion can be achieved without the need for such treatments as buffing or primer application.

That is, the present invention provides a) S1-I1-S
Type 2 block copolymer (S1 and S2 are styrene polymer blocks, I1 is isoprene polymerized blocks, S1 and S
The number average molecular weight of 2 is 8000 or more) 10
~60% by weight; b) S3-I2-S4 type block copolymer (S3,S4
is a styrene polymer block, I2 is an isoprene polymer block, S3 has a number average molecular weight of 8000 or more, and S4 has a number average molecular weight of 5000 or less) and/or S
5-I3 type block copolymer (S5 is a styrene polymer block, I3 is an isoprene polymer block, and the number average molecular weight of S5 is 8000 or more) is mainly a mixed block copolymer consisting of 90-40% by weight. As a component, 5 parts of tackifying resin per 100 parts by weight of this mixed block copolymer.
The present invention relates to a pressure-sensitive adhesive characterized by using a rubber-based pressure-sensitive adhesive composition containing 0 to 200 parts by weight.

0010

Structure and operation of the invention The mixed block copolymer of the present invention is composed of a mixture of the above-mentioned components a and b, which have a high affinity with vulcanized rubber molded products. These two components are used in combination because they provide a large cohesive force that can withstand repulsive forces, and component b provides fluidity that eliminates adhesion inhibitors on the vulcanized rubber surface layer and exhibits selective wettability. By doing so, sufficient adhesive strength can be obtained without subjecting the vulcanized rubber molded product to conventional treatments such as buffing and primer coating.

[0011] The S1-I1-S2 type block copolymer as component a is composed of styrene polymer blocks S1,
The number average molecular weight of S2 is 8,000 or more, preferably 10,000 to 30,000. here,
If either of the number average molecular weights of S1 and S2 is less than 8,000, sufficient cohesive force to withstand the repulsive force of the vulcanized rubber molded product will not be obtained. The number average molecular weight of the isoprene polymer block I1 is appropriately set within a range such that the number average molecular weight of the entire block copolymer is 50,000 to 400,000, depending on the desired properties of the adhesive.

As component b, one or both of an S3-I2-S4 type block copolymer and an S5-I3 type block copolymer are used. Of these, S3-I
In the 2-S4 type block copolymer, one of the styrene polymer blocks S3 constituting it has a number average molecular weight of 8000.
The number average molecular weight of the other styrene polymer block S4 is preferably 10,000 to 30,000, and the number average molecular weight of the other styrene polymer block S4 is 5.
000 or less, preferably 1000 to 3000.

In the above S3-I2-S4 type block copolymer, if the number average molecular weight of S3 becomes less than 8,000 or the number average molecular weight of S4 exceeds 5,000, the repulsive force of the vulcanized rubber molded product decreases. A sufficient cohesive force to withstand this may not be obtained, and the wettability to the surface of the molded article may be impaired. The number average molecular weight of isoprene polymer block I2 is:
Depending on the desired properties of the adhesive, the number average molecular weight of the block copolymer as a whole is appropriately set within a range of 50,000 to 400,000.

[0014] Furthermore, the S5-I3 type block copolymer is
The number average molecular weight of the styrene polymer block S5 constituting this is 8,000 or more, preferably 10,000 to 3,000.
0, and the number average molecular weight of S5 is 800.
If it is less than 0, it will not be possible to obtain a large cohesive force that can withstand the repulsive force of the vulcanized rubber molded product. The number average molecular weight of the isoprene polymer block I3 is appropriately set within a range such that the number average molecular weight of the entire block copolymer is from 50,000 to 400,000.

Each of the block copolymers constituting component a and component b can be obtained by a known living anionic polymerization method using a lithium-based initiator. At that time, for example, in the triblock type,
Styrene polymer block, isoprene polymer block,
It may be synthesized by sequentially reacting the styrene polymer blocks, or the styrene polymer block and the isoprene polymer block may be synthesized separately and then combined using a coupling agent to form a triblock structure. Good too.

In the mixed block copolymer of the present invention,
The mixing ratio of both components a and b is such that component a is 10 to 60% by weight and component b is 90 to 40% by weight, particularly preferably component a is 20 to 50% by weight and component b is 80 to 50% by weight.
It is preferable to set the ratio to be % by weight. If it is outside this range, the wettability to the surface of the vulcanized rubber molded product will decrease, and sufficient cohesive force to withstand the repulsive force of the vulcanized rubber molded product will not be obtained.

In the present invention, the mixed block copolymer as described above is the main component, and a tackifying resin is blended therein. As this tackifier resin, any conventionally known resin that is liquid or solid at room temperature can be used, such as terpene resin, terpene phenol resin, terpene aromatic resin, coumaron indene resin, styrene resin, Petroleum-based resins, phenol-based resins, xylene-based resins, rosin-based resins, etc. can be mentioned, and two or more of these can be used in combination as necessary.

The tackifying resin is used in an amount of 50 to 200 parts by weight, particularly preferably 70 to 130 parts by weight, based on 100 parts by weight of the mixed block copolymer. If it is less than 50 parts by weight, it is difficult to impart good adhesion to vulcanized rubber, and if it is more than 200 parts by weight, the cohesive force is poor, and in either case, good results cannot be obtained in terms of adhesion to vulcanized rubber.

The rubber-based pressure-sensitive adhesive composition of the present invention comprises:
In addition to the above-mentioned mixed block copolymer and tackifying resin as essential components, various polymer components consisting of elastomers and/or plastomers other than the above-mentioned mixed block copolymer may be included for the purpose of finely adjusting adhesive properties. Can be done.

Examples of such polymer components include styrene-butadiene-styrene type block copolymers, styrene-isoprene-styrene type hydrogenated block copolymers, styrene-butadiene-styrene type hydrogenated block copolymers, Butyl rubber, polyisobutylene, etc. are preferably used, but other polymers other than the rubber component such as ethylene-vinyl acetate copolymer may also be used.

The pressure-sensitive adhesive composition of the present invention further contains process oil, polyester plasticizer, polybutene,
A softening agent such as liquid rubber may be included if necessary. The amount of the softener to be used is preferably 75 parts by weight or less, usually 5 to 75 parts by weight, per 100 parts by weight of the mixed block copolymer of both components a and b.

The pressure sensitive adhesive composition of the present invention also includes:
Various additives conventionally known to be added to pressure-sensitive adhesives, such as antioxidants, ultraviolet absorbers, fillers, pigments, and extenders, can be blended. These amounts may be normal amounts.

The rubber-based pressure-sensitive adhesive composition of the present invention constructed as described above may be a solvent-free hot melt coating type or a solution type using an appropriate organic solvent such as toluene. Furthermore, it can be of an aqueous or non-aqueous emulsion type. When a solution type is used, the viscosity of the solution is lower than that of a conventional one using natural rubber or the like as a base polymer, so high solids coating is possible, which is industrially advantageous.

When using the various types of rubber-based pressure-sensitive adhesive compositions of the present invention, each type is used as a pressure-sensitive adhesive in the final form from a vulcanized rubber molded product. Although it may be applied directly to an adherend, it is usually better to use it as a film-like pressure-sensitive adhesive layered on a suitable base material.

In this case, a layer may be formed on only one side of the base material, but for the purpose of adhering the vulcanized rubber molded product to another adherend, a so-called double-sided layer is formed on both sides of the base material. It is preferable to use an adhesive sheet. When producing this double-sided adhesive sheet, for example, the above-mentioned adhesive composition may be coated and dried to form a layer on a release paper, and two sheets of this composition may be prepared, and these may be bonded to both sides of a base material.

The base material is usually a porous base material such as nonwoven fabric, woven fabric, or paper, or a plastic film such as polyester film, polyethylene film, polypropylene film, or polyvinyl chloride film, and has a thickness of 5.
A thickness of approximately 200 μm is used. If you use plastic film and leave it for a long time after using the adhesive,
Since migration of the adhesive component from one side of the film to the other side can be prevented, deterioration of adhesive strength over time is suppressed.

[0027] The adhesive layer provided on this base material, that is, the layer of the rubber-based pressure-sensitive adhesive composition, preferably has a thickness of usually about 10 to 400 μm on one side, but is not limited to this. It can be determined as appropriate depending on the purpose of use. Such an adhesive layer generally provides a large adhesive force of 800 g/20 mm width or more to molded products of vulcanized rubber such as chloroprene rubber or EPT rubber.

In addition, when obtaining a double-sided adhesive sheet, a layer of the above-mentioned rubber-based pressure-sensitive adhesive composition is provided only on one side of the base material, and another adhesive composition, especially an acrylic-based pressure-sensitive adhesive composition, is provided on the other side. Modifications may also be made, such as providing a layer of adhesive composition.

According to this embodiment, a layer of a rubber-based pressure-sensitive adhesive composition can be used for adhesion to the vulcanized rubber molded article, and the above-mentioned acrylic-based pressure-sensitive adhesive composition can be used for adhesion to other adherends. The availability of layers such as compositions may provide more desirable adhesive properties depending on the intended use.

Note that the layer of the acrylic pressure-sensitive adhesive composition described above is coated with an appropriate coloring pigment, as in the case of the layer of the rubber-based pressure-sensitive adhesive composition. The deterioration may be prevented by the above-mentioned coloring. For the same purpose, the base material itself may be colored.

[0031]

As described above, in the present invention, by using a specific mixed block copolymer as the main component of the adhesive, it is possible to bond vulcanized rubber molded products, especially when bonding these molded products to curved surfaces. It is possible to obtain a pressure-sensitive adhesive that exhibits sufficient adhesion strength when applied to an adherend having a bond without performing conventional treatments such as buffing or primer coating.

[0032]

[Examples] Next, examples of the present invention will be specifically explained in comparison with comparative examples. In addition, hereinafter, parts mean parts by weight. Further, block copolymers A to C used in the following Examples and Comparative Examples were synthesized by the following method.

<Block Copolymer A> 500 parts of dehydrated and purified cyclohexane and 0.03 parts of tetrahydrofuran were charged into a reaction autoclave under a nitrogen atmosphere, and the temperature of the inner bath was set at 60°C. Next, a hexane solution containing 0.02 parts of n-butyllithium was added, followed by 7.5 parts of styrene, and polymerization was carried out for 100 minutes. Then, 85 parts of isoprene was added and polymerized for 100 minutes. Finally, 7.5 parts of styrene was added and polymerized for 100 minutes.

[0034] In the polymer solution thus obtained, 2
・S1-I1-S2 type block copolymer A by adding 0.6 part of 6-di-tert-butyl-p-cresol
A solution containing was obtained. When the number average molecular weights of each block portion of this block copolymer A were measured at each polymerization stage, S1 was 21,000, I1 was 240,000, S1 was 21,000, I1 was 240,000, S
2 was 21,000.

<Block copolymer B> The above block copolymer A except that the amount of monomer and the amount of polymerization initiator were changed.
Polymerization was carried out in the same manner as above to obtain a solution containing S3-I2-S4 type block copolymer B. The number average molecular weight of each block portion of this block copolymer B is 2000 for S3.
0, I2 was 130,000, and S4 was 3,000.

<Block copolymer C> The above block copolymer A except that the amount of monomer and the amount of polymerization initiator were changed.
Polymerization was carried out in the same manner as above to obtain a solution containing S5-I3 type block copolymer C. The number average molecular weights of each block portion of this block copolymer C are 15,000 for S5 and 15,000 for I3.
was 85,000.

Example 1 30 parts of block copolymer A and 70 parts of block copolymer B were mixed, and this mixed block copolymer was further mixed with C5.
100 parts of petroleum-based tackifier resin (softening point 100°C) and 2 parts of phenolic anti-aging agent are mixed well, diluted with toluene so that the solid content is 50% by weight,
A rubber-based pressure sensitive adhesive solution was prepared.

[0038] This pressure-sensitive adhesive solution was applied to a thickness of 25 μm.
It was coated on both sides of the polyester film so that the thickness after drying was 60 μm, and then it was dried to 20 mm.
A double-sided adhesive tape was produced by cutting it into widths.

Example 2 A rubber-based sensitizer was prepared in the same manner as in Example 1, except that the amount of block copolymer A used was changed to 50 parts, and the amount of block copolymer B used was changed to 50 parts. A pressure adhesive solution was prepared, and a double-sided adhesive tape was produced in the same manner as in Example 1 using this solution.

Example 3 Block copolymer A50 was used as a mixed block copolymer.
A rubber-based pressure-sensitive adhesive solution was prepared in the same manner as in Example 1, except that 50 parts of block copolymer C and 50 parts of block copolymer C were used. Using this solution, a double-sided adhesive tape was prepared in the same manner as in Example 1. was created.

Comparative Example 1 A rubber-based pressure-sensitive adhesive solution was prepared in the same manner as in Example 1, except that the amount of block copolymer A used was changed to 100 parts, and block copolymer B was not used at all. A double-sided adhesive tape was prepared in the same manner as in Example 1 using this solution.

Comparative Example 2 A rubber-based material was prepared in the same manner as in Example 1, except that the amount of block copolymer B used was changed to 100 parts, and both block copolymer A and tackifier resin were not used at all. A pressure sensitive adhesive solution was prepared, and a double-sided adhesive tape was produced in the same manner as in Example 1 using this solution.

The adhesive strength and curved surface adhesion properties of each of the double-sided adhesive tapes obtained in Examples 1 to 3 and Comparative Examples 1 and 2 above were measured in the following manner.

<Adhesive force> Using a vulcanized rubber plate as the adherend, the adhesive force (g/
20 mm width) was measured.

<Curved surface attachment characteristics> 10mm x 100m
A vulcanized rubber plate with a size of m is wiped dry with a rag, and one side of the double-sided adhesive tape is pasted with one reciprocation of a 2 kg roll. Next, the release paper is peeled off, and the other side is bonded to a stainless steel cylinder with a diameter of 200 mm using a 5 kg roll. After being left at 50° C. for 2 days, the height of the float from the end surface was measured.

In the above two measurement tests, the vulcanized rubber plates were a 3 mm thick chloroprene rubber plate (Neo-180 manufactured by Irumagawa Rubber Co., Ltd.) and a 3 mm thick EPT rubber plate.
A rubber plate (EP-5065 manufactured by Irumagawa Rubber) was used.

The above measurement results were as shown in Table 1 below. In addition, this Table 1 includes, as a reference example,
The adhesion strength and curved surface adhesion characteristics were investigated in the same manner as above using acrylic double-sided adhesive tape after applying a chloroprene rubber primer treatment to the vulcanized rubber plate as the adherend.The results are also listed below. .

The acrylic double-sided adhesive tape used in the above reference example was produced as follows. First, acrylic acid n
- A monomer solution of 70 parts of butyl, 27 parts of 2-ethylhexyl acrylate, 3 parts of acrylic acid, and 233 parts of ethyl acetate was subjected to radical polymerization by a conventional method to obtain a weight average molecular weight of 5.
A polymer solution containing 50,000% acrylic polymer and a solid content of 30% by weight was obtained, and to this was added 100% acrylic polymer.
of rosin-based tackifying resin (softening point 100°C)
Add 0 parts and mix. Next, the above mixed solution was applied to both sides of a polyester film with a thickness of 25 μm so that the thickness after drying would be 60 μm on each side, and dried. After that, the tape was cut into the same tape width as in Example 1. , an acrylic double-sided adhesive tape.

[0049]

[Table 1]

As is clear from the results in Table 1 above, according to the double-sided adhesive tape of the present invention, the vulcanized rubber plate does not need to be subjected to conventional treatments such as buffing or primer coating. It can be seen that very good adhesive properties can be obtained.

Claims (3)

[Claims] Claim 1: a) S1-I1-S2 type block copolymer (S1 and S2 are styrene polymer blocks, I1 is isoprene polymer block, and the number average molecular weights of S1 and S2 are both 8000 or more) 10 to 60% by weight,
b) S3-I2-S4 type block copolymer (S3, S4
is a styrene polymer block, I2 is an isoprene polymer block, S3 has a number average molecular weight of 8000 or more, and S4 has a number average molecular weight of 5000 or less) and/or S
5-I3 type block copolymer (S5 is a styrene polymer block, I3 is an isoprene polymer block, and the number average molecular weight of S5 is 8000 or more) is mainly a mixed block copolymer consisting of 90-40% by weight. As a component, 5 parts of tackifying resin per 100 parts by weight of this mixed block copolymer.
A pressure-sensitive adhesive characterized by using a rubber-based pressure-sensitive adhesive composition containing 0 to 200 parts by weight. 2. A film-like pressure-sensitive adhesive comprising a base material and a layer of the rubber-based pressure-sensitive adhesive composition according to claim 1 on both sides of the base material. 3. A layer of the rubber-based pressure-sensitive adhesive composition according to claim (1) is provided on one side of the base material, and a layer of the acrylic-based pressure-sensitive adhesive composition is provided on the other side. A film-like pressure-sensitive adhesive.