JPH0715089B2 - Block copolymer composition for pressure-sensitive adhesive and pressure-sensitive adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a block copolymer composition and a pressure-sensitive adhesive composition suitable for pressure-sensitive adhesive use, and more specifically, initial adhesive strength, holding power and flexibility. , A block copolymer composition which is excellent in processability and thermal stability and is composed of a tri-branched block copolymer having a specific composition and a linear diblock copolymer, and a pressure-sensitive adhesive composition obtained by using the block copolymer composition Regarding

(Prior Art) Various block copolymers such as polystyrene / polyisoprene block copolymers have been conventionally used as base polymers for pressure-sensitive adhesive compositions. Although it has excellent adhesive strength but poor holding power, the radial block copolymer alone has excellent holding power, but the initial adhesive strength is insufficient, so radial block copolymers and linear block copolymers are used in combination. (For example, JP-A-51-26938,
JP-A-61-26647). However, there has not yet been obtained a material that can simultaneously satisfy the requirements for properties other than the initial adhesive strength and holding power required for the pressure-sensitive adhesive, that is, various properties such as flexibility, processability, and thermal stability.

(Problems to be Solved by the Invention) An object of the present invention is to obtain a pressure-sensitive adhesive having an excellent balance of the above properties and a block copolymer composition for obtaining the same. As a result of earnest studies to achieve the above-mentioned objects, the present inventors have made a good leap in initial adhesive strength, holding power, flexibility, processability and thermal stability by using a block copolymer composition having a specific composition. Find that it can be improved
The present invention has been completed based on this finding.

(Means for Solving the Problems) Thus, according to the present invention, the general formula (I) (AB) ₃ X
(In the formula, A is a polymer block of an aromatic vinyl monomer,
B represents a polymer block of a conjugated diene-based monomer, and X represents a residue of a silane-based trifunctional or tetrafunctional coupling agent). 50 to 95% by weight of a three-branched block copolymer having a weight ratio of 10/90 to 30/70 and a general formula (II) CI (wherein
C is a polymer block of an aromatic vinyl monomer, and I is an isoprene polymer block), and the weight ratio of the polymer block C to the polymer block I is 5/95 to 30/70.
And 50 to 5% by weight of the linear block copolymer, 100 parts by weight of the block copolymer composition for pressure-sensitive adhesive, and tackifying resin 10 A pressure-sensitive adhesive composition comprising about 150 parts by weight is provided.

The tri-branched block copolymer, which is the first component of the block copolymer composition of the present invention, comprises a polymer block A of an aromatic vinyl monomer and a polymer of a conjugated diene monomer having a polymerization active terminal. It is a tri-branched block copolymer having a structure in which an AB block copolymer consisting of a united block B is coupled with a silane-based trifunctional or tetrafunctional coupling agent.

The aromatic vinyl monomer used in the three-branched block copolymer used in the present invention is not particularly limited, and specific examples thereof include styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene and the like. Among them, styrene is preferable.

The conjugated diene-based monomer used in the tri-branched block copolymer used in the present invention is not particularly limited, and specific examples thereof include 1,3-butadiene, isoprene and 2,3-dimethyl-1. , 3-butadiene, piperylene,
2,4-hexadiene and the like can be mentioned, among which
1,3-Butadiene and isoprene are preferred.

The ratio of the polymer block A of the aromatic vinyl monomer in the three-branched block copolymer used in the present invention is 10 to 30% by weight, preferably 12 to 22% by weight. If this proportion is less than 10% by weight, the holding power of the obtained block copolymer will decrease, and if this proportion exceeds 30% by weight, the initial adhesion and flexibility of the obtained block copolymer will decrease.

The polystyrene-converted weight average molecular weight of the tri-branched block copolymer used in the present invention is 125,000 to 400,000.
Is. When the molecular weight is below the lower limit, the retentivity of the obtained block copolymer will be insufficient, and above the upper limit, the processability of the obtained block copolymer will be unsatisfactory.

The coupling agent used in the three-branched block copolymer used in the present invention is a silane-based trifunctional or tetrafunctional coupling agent. Even if a coupling agent other than the above is used, the object of the present invention to obtain a pressure-sensitive adhesive composition having an excellent balance of initial adhesive strength, holding power, flexibility, processability and thermal stability cannot be achieved.

Specific examples of the silane-based trifunctional coupling agent include:
Methyltrichlorosilane, phenyltrichlorosilane,
Ethyltrichlorosilane, tertiary butyltrichlorosilane, methyltribromosilane and the like, and specific examples of the silane-based tetrafunctional coupling agent include silicon tetrachloride, silicon tetrabromide and tetramethoxysilane. However, the coupling agent is not limited to these, as long as it is a trifunctional or tetrafunctional coupling agent having a silicon atom.

Next, the linear diblock copolymer represented by the general formula (II) CI, which is the second component of the block copolymer composition of the present invention, blocks an aromatic vinyl monomer and isoprene. Obtained by copolymerization.

In the present invention, it is important to use isoprene for the synthesis of the linear diblock copolymer, and
Even if a 1,3-conjugated diene-based monomer such as butadiene or piperylene is used, the effect of the present invention cannot be obtained.

The aromatic vinyl monomer used in the synthesis of the linear diblock copolymer used in the present invention is not particularly limited, and specific examples thereof include styrene, α-methylstyrene, vinyltoluene and vinyl. Although naphthalene etc. are mentioned, styrene is especially preferable.

The ratio of the polymer block C of the aromatic vinyl monomer in the linear diblock copolymer used in the present invention is
It is 5 to 30% by weight, preferably 10 to 25% by weight. If this proportion is less than 5% by weight, the holding power of the obtained linear diblock copolymer will decrease, and if this proportion exceeds 30% by weight, the initial adhesive strength of the obtained linear diblock copolymer will decrease. To do.

The linear diblock copolymer used in the present invention has a polystyrene reduced weight average molecular weight of 50,000 to 150,000. If the molecular weight is less than the lower limit, the retentivity of the obtained block copolymer will be insufficient, and if the molecular weight is more than the upper limit, the processability of the obtained block copolymer will be unsatisfactory.

In the block copolymer composition of the present invention, the weight ratio of the first component (three-branched block copolymer) and the second component (linear diblock copolymer) is 50 to 95/50 to 5, preferably Is 50-90 / 5-10. If the amount is out of this range, the retentivity of the resulting block copolymer composition will decrease, and if the proportion of the tri-branched block copolymer exceeds 95% by weight, the processability will be unsatisfactory. In addition, 5% by weight or less of the block copolymer composition can be replaced with a block copolymer other than the tri-branched block copolymer and the linear diblock copolymer within a range not impairing the effects of the present invention.

In the block copolymer composition of the present invention, the three-branched block copolymer and the linear diblock copolymer are separately synthesized, and then these are mixed in the above weight ratio by an arbitrary method. Can be obtained by Also,
As will be described later, the polymer block B of the conjugated diene-based monomer having a polymerization active terminal is coupled with the AB block copolymer in which the polymer block A of the aromatic vinyl monomer is directly bonded to form three branches. Block copolymer composition comprising the tri-branched block copolymer and the linear diblock copolymer in the above weight ratio by controlling the amount of the coupling agent when obtaining the block copolymer. Can be obtained at one time.

The method for synthesizing the tri-branched block copolymer used in the present invention is not particularly limited, but it can be produced, for example, according to the following processes (a) to (d). That is, (a) First, an aromatic vinyl monomer is polymerized with a monolithium initiator in a solvent containing a polar compound.

As the monolithium initiator, known ones capable of initiating polymerization of an aromatic vinyl monomer and a conjugated diene monomer can be used, and methyllithium, n-propyllithium, n-
Butyl lithium, sec-butyl lithium and the like are shown as typical examples, but n-butyl lithium is particularly preferable. The amount of the monolithium initiator used can be calculated by a method well known to those skilled in the art according to the molecular weight of the desired polymer.

The polymerization solvent is not particularly limited as long as it is inert to the monolithium initiator, and for example, an open chain hydrocarbon solvent, a cyclic hydrocarbon solvent or a mixed solvent thereof is used. As the open chain hydrocarbon solvent, n-butane, isobutane, or a mixture thereof; 1-butene, isobutylene, trans-2-butene, cis-2-butene, or a mixture thereof, 1-pentene, trans-2-pentene, Cis-2-pentene or a mixture thereof; n-
Examples include open-chain alkanes and alkenes having 4 to 5 carbon atoms such as pentane, isopentane, neo-pentane or a mixture thereof; 1-pentene, trans-2-pentene, cis-2-pentene or a mixture thereof. Specific examples of the cyclic hydrocarbon solvent include aromatic compounds such as benzene, toluene and xylene; and alicyclic hydrocarbons such as cyclohexane.
From the viewpoint of controlling the polymerization temperature and controlling the molecular weight distribution of the polymer block of the aromatic vinyl monomer, the weight ratio of the open chain hydrocarbon solvent having 4 to 5 carbon atoms to the cyclic hydrocarbon solvent is 5:95 to 50. :Five
It is preferably used as a mixed solvent having a range of 0, preferably 10:90 to 40:60.

Further, it is not essential to use a polar compound, but by using it, the polymerization initiation rate is adjusted, the vinyl content of the polymer of the conjugated diene monomer is adjusted, and the polymer block of the aromatic vinyl monomer is used. The molecular weight distribution of can be adjusted. As the polar compound, in a copolymerization of a conjugated diene monomer or an aromatic vinyl monomer with a monolithium initiator, among known polar compounds used as a vinyl content modifier or a randomizer,
Aromatic or aliphatic ethers or tertiary amines having a relative dielectric constant of 2.5 to 5.0 can be used. Specific examples of such polar compounds include aromatic ethers such as diphenyl ether and anisole; aliphatic ethers such as diethyl ether and dibutyl ether; tertiary monoamines such as trimethylamine, triethylamine and tripropylamine. One or more of are used. In order to make the molecular weight distribution of the polymer block of the aromatic vinyl monomer to be a predetermined one, and to improve the properties of the pressure-sensitive adhesive containing the obtained block copolymer, the preferable amount of the polar compound used is The amount is in the range of 0.1 to 100 mol, preferably 0.5 to 20 mol, per mol of the monolithium initiator.

In the present invention, the polymerization method of the aromatic vinyl monomer is not particularly limited, batch polymerization in which the total amount of the aromatic vinyl monomer and the total amount of the initiator are charged in a batch polymerization system and reacted, and these are continuously Continuous polymerization in which the reaction is performed while being supplied to the polymerization system,
Any of commonly used methods, such as a method in which polymerization is performed to a predetermined conversion rate using a part of the monomer and the initiator and then the remaining monomer and the initiator are converted to continue the polymerization, You may use. Polymerization is usually 0 ° C to 90 ° C, preferably 20 ° C.
It is carried out in the range of ~ 70 ° C. When it is difficult to control the reaction temperature, it is preferable to control the temperature by reflux cooling using a reaction vessel equipped with a reflux condenser.

(B) Next, the conjugated diene-based monomer is added to the polymerization system in which the polymer block A of the aromatic vinyl monomer having a polymerization active terminal is present to carry out polymerization. The conjugated diene-based monomer is preferably added continuously in order to control the reaction heat, but an addition method other than this may be adopted. Thus, an AB block copolymer in which the polymer block B of the conjugated diene-based monomer having a polymerization active terminal is directly bonded to the polymer block A of the aromatic vinyl monomer is produced.

(C) After the completion of the polymerization reaction of the conjugated diene-based monomer, a coupling agent is added to the polymerization system to bond the AB block copolymer having an active terminal to the target general formula ( I) (AB) ₃ X (wherein A is a polymer block of an aromatic vinyl monomer, B is a polymer block of a conjugated diene-based monomer, and X is a silane-based trifunctional or A tri-branched block copolymer represented by (representing the residue of a tetrafunctional coupling agent) is obtained. At this time, a compound that promotes the coupling reaction can be added.

In the present invention, the amount of coupling agent used is important. In order to obtain the tri-branched block copolymer used in the present invention, the amount of the silane coupling agent used is 1 / mol of the silane coupling agent based on 1 mol of the monolithium initiator used for the polymerization. It is best to use 3 moles.

When the amount of the coupling agent is increased, it means one having a structure of a bi-branched block copolymer ((AB) ₂ X.
A, B, X are the same as above) or a linear block copolymer having the structure of A-B-X having a residue of a coupling agent at the terminal (provided that A, B and X are the same as above). A large amount will be a byproduct.

It is also possible to obtain a tri-branched block copolymer and a linear diblock copolymer at the same time, and for this purpose, 1/3 mol of monolithium initiator used for the polymerization is more than 1/3 mol. A small amount of trifunctional coupling agent is used. This amount can be calculated according to the composition of the target block copolymer composition, but in practice, there are problems such as deactivation of the monolithium initiator or the coupling agent, so preliminary experiments It is better to obtain the optimum value by performing.

(D) After completion of the coupling reaction, if necessary, water, alcohol, acid, etc. are added to inactivate the polymerization active species, and an antioxidant is added, and then a known polymer separation method (for example, steam stripping, etc.). The polymer is separated by), and the desired three-branched block copolymer or a mixture of this and a linear diblock copolymer is obtained through a drying step.

The linear diblock copolymer used in the present invention is
Synthesis process of the above 3-branched block copolymer (a)
In the same manner as in (b) to (b), after obtaining a linear C-I block copolymer in which a polymer block I of isoprene having a polymerization active terminal is directly bonded to a polymer block C of an aromatic vinyl monomer, It can be obtained by deactivating the polymerization active species and adding the antioxidant after the process (d), followed by separation and drying steps without the coupling reaction.

The pressure-sensitive adhesive composition of the present invention mainly comprises the block copolymer composition of the present invention and a tackifying resin.

The block copolymer composition used in the pressure-sensitive adhesive composition of the present invention can be partially replaced with other polymers such as natural rubber, butadiene rubber, and isoprene rubber, as long as the effects of the present invention are not impaired.

As the tackifying resin used in the present invention, a conventionally known tackifying resin used in a pressure-sensitive adhesive using a conventional block copolymer similar to the block copolymer used in the present invention can be used. Specifically, rosins; modified rosins such as disproportionated rosins and dimerized rosins; esterified products of polyhydric alcohols such as glycol, glycerin and pentaerythritol with rosins or modified rosins; terpene resins; aliphatic resins , Aromatic, alicyclic or aliphatic-aromatic copolymer hydrocarbon resins or hydrides thereof; phenol resins; chroman-indene resins and the like. A particularly preferred tackifying resin is an aliphatic or aliphatic-aromatic copolymer hydrocarbon resin which has good compatibility with the block copolymer composition of the present invention. The amount of tackifying resin used is 10 to 150 per 100 parts by weight of the block copolymer composition.
Parts by weight.

If necessary, a softening agent (plasticizer), an antioxidant, a heat stabilizer, an ultraviolet absorber, a filler and other compounding agents can be added to the pressure-sensitive adhesive composition of the present invention.

As the softening agent, conventionally known aromatic, paraffinic or naphthene-based extender oils (extender oils), which are used in pressure-sensitive adhesives, liquid polymers such as polybutene and polyisobutylene can be used. The amount of the softening agent used is usually 100 parts by weight or less per 100 parts by weight of the block copolymer composition.

Antioxidants include hindered phenol compounds such as 2,6-di-tert-butyl-p-cresol and di-tert-butyl-4-methylphenol; thiodicarboxylates such as dilaurylthiopropionate. Esters; phosphites such as tris (nonylphenyl) phosphite are used alone or in combination.

The pressure-sensitive adhesive composition of the present invention is dissolved in n-hexane, cyclohexane, benzene, toluene or the like as a solution-type pressure-sensitive adhesive, as an emulsion-type pressure-sensitive adhesive dispersed in water using an emulsifier, or without solvent. It can be used as a hot-melt type pressure-sensitive adhesive. Particularly suitable are hot melt adhesives.

(Effects of the Invention) Thus, according to the present invention, a block copolymer composition for pressure-sensitive adhesive having an excellent balance of initial adhesive strength, holding power, flexibility, processability and thermal stability as compared with the prior art is provided. An excellent pressure-sensitive adhesive composition can be obtained by combining this with a tackifying resin.

(Example) Below, an Example is given and this invention is demonstrated still more concretely. In addition, parts and% in Examples, Comparative Examples and Reference Examples,
Unless stated otherwise, it is based on weight.

In this example, the molecular weight of the polymer is a polystyrene-equivalent weight average molecular weight determined by high performance liquid chromatography using tetrahydrofuran as a carrier. Furthermore, the composition of the copolymer was determined from the peak area of each copolymer obtained by high performance liquid chromatography.

Reference Example 1 Using the pressure resistant reactor of 50, 18.75 kg of a mixed solvent of n-butane / cyclohexane = 30/70, and 24 dibutyl ether.
In the presence of 0 mmol, 120 mmol of n-butyllithium initiator, 1 hour of polymerization at 30 ° C., 1.52 kg of styrene was first polymerized, and 6.48 kg of isoprene was added, and the reaction temperature was from 50 ° C. to 60 ° C.
Polymerization was carried out for about 1 hour and a half while controlling the temperature by reflux cooling so that the temperature became between 0 ° C. Then, 38 mmol of silicon tetrachloride was added as a coupling agent and a coupling reaction was carried out for 2 hours. After this, 50 ml of methanol as a polymerization terminator and 40 g of 4-methyl-di-tert-butylphenol as an antioxidant were added to the reaction mixture and mixed well, and the resulting mixed solution was heated little by little to 85 to 95 ° C. The solvent was volatilized by dropping it into warm water. The obtained polymer was pulverized and dried with hot air at 85 ° C. to obtain a block copolymer mixture (polymer). The molecular weight of the polymer is 290,000, 95% of the 3-branched block copolymer with a molecular weight of 300,000, and the molecular weight of 10
It contained 5% of all linear diblock copolymers.

Reference Example 2 A polystyrene-polyisoprene linear diblock copolymer (polymer) was obtained in the same manner as in Example 1 except that the coupling reaction with silicon tetrachloride was not carried out. The molecular weight of the polymer was 100,000.

Reference Example 3 A block copolymer mixture (polymer) was obtained in the same manner as in Reference Example 1 except that 38 mmol of phenyltrichlorosilane was used as the coupling agent and 12 mmol of tetramethylethylenediamine was used in combination. Polymer molecular weight is 29
And a tri-branched block copolymer with a molecular weight of 300,000 is 95
%, And 5% of a linear diblock copolymer having a molecular weight of 100,000 was contained.

Reference Example 4 A block copolymer mixture (polymer) was obtained in the same manner as in Reference Example 3 except that the amount of phenyltrichlorosilane was 28 mmol. The polymer had a molecular weight of 240,000, and contained 70% of a 3-branched block copolymer having a molecular weight of 300,000 and 30% of a linear diblock copolymer having a molecular weight of 100,000.

Reference Example 5 A block copolymer mixture (polymer) was obtained in the same manner as in Reference Example 1 except that the coupling agent was 39 mmol of tin tetrachloride. The molecular weight of the polymer is 300,000,
90% of 3-branched block copolymer of 300,000, 5% of 4-branched block copolymer, 2% of 2-branched block copolymer of 200,000 molecular weight, linear block copolymer of 100,000 molecular weight Is 3
% Was included.

Reference Example 6 A block copolymer mixture (polymer) was obtained in the same manner as in Reference Example 3 except that the amount of phenyltrichlorosilane was changed to 50 mmol. The molecular weight of the polymer is 225,000, and the three-branched block copolymer with a molecular weight of 300,000 has a molecular weight of 37.5%.
50% of 200,000 2-branched block copolymer was contained, and the rest was a linear diblock copolymer having a molecular weight of 100,000 and a linear block copolymer having an A-B-X structure.

Reference Example 7 A block copolymer mixture (polymer) was obtained in the same manner as in Reference Example 3 except that the amount of phenyltrichlorosilane was 12 mmol. The polymer had a molecular weight of 160,000, and contained 30% of a tri-branched block copolymer having a molecular weight of 300,000 and 70% of a linear diblock copolymer having a molecular weight of 100,000.

Reference Example 8 A block copolymer mixture (polymer) was obtained in the same manner as in Reference Example 1 except that 50 mmol of ethylene dibromide was used as the coupling agent. The polymer had a molecular weight of 180,000, and contained 83% of a 2-branched block copolymer having a molecular weight of 200,000 and 17% of a linear diblock copolymer having a molecular weight of 100,000.

Reference Example 9 A polystyrene-polyisoprene block copolymer having a polymerization active terminal was obtained in the same manner as in Example 1 except that the amount of n-butyllithium initiator was 60 mmol and the amount of styrene was 0.76 kg. Then, 0.76 kg of polystyrene was further added and the polymerization was continued at 60 ° C. for 2 hours. Then, the polymerization was stopped in the same manner as in Example 1 to carry out AIA (however,
A linear triblock copolymer (polymer) having a structure of A and I is the same as above) was obtained. The molecular weight of the polymer is
It was 190,000.

Reference Example 10 A polystyrene-polybutadiene linear diblock copolymer (polymer) was obtained in the same manner as in Reference Example 2 except that butadiene was used instead of isoprene. The molecular weight of the polymer was 100,000.

Reference Example 11 The same as Reference Example 1 except that the charged amounts of styrene and isoprene were changed, and the weight ratio (S / I ratio) of the polystyrene block and the polyisoprene block was 5/95. A mixture (polymer) of 95% branched block copolymer and 5% linear block copolymer having a molecular weight of 100,000, and a three-branched block copolymer having a S / I ratio of 40/60 and a molecular weight of 300,000. A mixture (polymer) of 95% of the combined product and 5% of a linear diblock copolymer having a molecular weight of 100,000 was obtained.

Reference Example 12 S / I ratios were 2/98 and 40/60, respectively, in the same manner as in Reference Example 2 except that the charged amounts of styrene and isoprene were changed.
In each case, a linear diblock copolymer (polymer) having a molecular weight of 100,000 was obtained.

Reference Example 13 Molecular weight was the same as in Reference Example 1 except that the amount of the initiator was changed.
A mixture (polymer) of 95% of a tri-branched block copolymer of 110,000 and 5% of a linear block copolymer of a molecular weight of 35,000,
95% tri-branched block copolymer with a molecular weight of 510,000 and a molecular weight of 17
Mixture with 5% of 10,000 linear block copolymer (polymer), 95% of 3-branched block copolymer with a molecular weight of 270,000 and 5% of linear diblock copolymer with a molecular weight of 90,000 (polymer) Got In addition, of these block copolymers
The S / I ratio was 19/81 in all cases.

Reference Example 14 Similar to Reference Example 2 except that the amount of the initiator was changed, the molecular weights were 35,000 and 200,000, respectively, and the S / I ratio was 19/81.
To obtain a linear diblock copolymer (polymer).

Example 1 100 parts of the block copolymer composition shown in Table 1 was put into a stirring blade type kneader, and a tackifying resin (Quinton M-
100, Nippon Zeon Co., Ltd. 100 parts, naphthenic process oil (Shelflex 371, Shell Chemical Co., Ltd.) 30 parts and antioxidant (ANTAGE W-400, Kawaguchi Chemical Industry Co., Ltd.) 1 part were added. After replacing the inside of the system with nitrogen gas, the mixture was kneaded at 160 to 180 ° C. to prepare a pressure-sensitive adhesive composition.
The pressure-sensitive adhesive composition was applied onto kraft paper with a hot melt coater to a thickness of 25 μm to prepare a pressure-sensitive adhesive tape, and the initial adhesive strength and holding power of the pressure-sensitive adhesive tape were measured. The initial adhesive strength was measured according to JIS-Z0237.
That is, at a temperature of 23 ° C, a 10 cm-long adhesive tape was attached to the slope of a stainless steel plate with an inclination angle of 30 degrees, with the adhesive side facing up, and the diameter from 3/32 inch to 1 inch from the position 10 cm above the slope. Roll steel balls of various sizes at an initial speed of 0,
Size of steel ball with maximum diameter to stop on adhesive tape (number)
Display with. The holding power was measured according to JIS-Z0237. That is, 25 mm x 10 mm on a stainless steel plate treated as above
Adhere the adhesive tape so that the areas in contact with each other, apply a load of 1 kg at 50 ° C, and display the time required for the adhesive tape to fall off the stainless steel plate.

In addition, a tambell-shaped test sample (distance between the marked lines is 15 mm, the width of the parallel part is 3 m) from each block copolymer composition in Table 1.
m, thickness 2 mm) was prepared, and the tensile test was performed according to JIS-K6301, and the value of elongation at break was used as an index of flexibility.

Regarding workability, melt viscosity was measured according to the method of JIS-K7210 and used as an index.

Further, for thermal stability, pellets of the block copolymer composition in a hot air circulation type oven under a nitrogen atmosphere,
After standing at 185 ° C for 2 hours, the composition of the block copolymer composition is examined by gel permeation chromatography, and the weight ratio of the three-branched radial block copolymer is reduced to that before heating. It was measured and used as the index.

The results are shown in Table 1.

From the results shown in Table 1, the effect of the present invention can be obtained even if a block copolymer composition other than the block copolymer composition comprising the tri-branched block copolymer of the present invention and the linear diblock copolymer is used. It turns out that can't be obtained.

Example 2 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 from the block copolymer composition shown in Table 2, and the same test as in Example 1 was performed on these.

The results are shown in Table 2.

From the results shown in Table 2, it is understood that the effect of the present invention cannot be obtained when the composition of the block copolymer composition is out of the range of the present invention.

Example 3 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 from the block copolymer composition shown in Table 3, and the same tests as in Example 1 were performed on these.

The results are shown in Table 3.

From the results in Table 3, it can be seen that the effect of the present invention cannot be obtained when the weight ratio of the polystyrene block and the polyisoprene block deviates from the conditions of the present invention.

Example 4 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 from the block copolymer composition shown in Table 4, and the same test as in Example 1 was performed on these.

The results are shown in Table 4.

From the results in Table 4, it can be seen that the effect of the present invention cannot be obtained when the molecular weight of the tri-branched block copolymer or the linear diblock copolymer deviates from the conditions of the present invention.

Claims (2)

[Claims] 1. General formula (I) (AB) ₃ X (wherein A is a polymer block of an aromatic vinyl monomer, B is a polymer block of a conjugated diene monomer, X Represents a residue of a silane-based trifunctional or tetrafunctional coupling agent), and the weight ratio of the polymer block A to the polymer block B is
Tri-branched block copolymer 50-95 which is 10 / 90-30 / 70
% By weight of the general formula (II) CI (wherein C represents a polymer block of an aromatic vinyl monomer, and I represents an isoprene polymer block), and a polymer block C
A block copolymer composition for pressure-sensitive adhesives, characterized in that it comprises 50 to 5% by weight of a linear diblock copolymer in which the weight ratio of the polymer block I is 5/95 to 30/70. 2. A pressure-sensitive adhesive composition comprising 100 parts by weight of the block copolymer composition for pressure-sensitive adhesive of claim 1 and 10 to 150 parts by weight of a tackifying resin.