JP3388010B2 - Block copolymer composition and pressure-sensitive adhesive composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a block copolymer composition and a pressure-sensitive adhesive composition suitable for use as a pressure-sensitive adhesive, and more specifically, a block copolymer composition having excellent thermal stability and an initial adhesive strength. The present invention relates to a pressure-sensitive adhesive composition having little change in holding power and melt viscosity after heating at high temperature.

[0002]

2. Description of the Related Art Conventionally, styrene-isoprene-styrene (SIS) block copolymers and styrene-butadiene-styrene have been used as base polymers for pressure-sensitive adhesives (adhesives) and hot-melt adhesives (hot-melt adhesives). (SBS)
A thermoplastic elastomer such as a block copolymer is used, and an adhesive composition in which both a SIS block copolymer and an SBS block copolymer are used as a base polymer is also known (Japanese Patent Publication No. 53- 42345).

Generally, a branched block copolymer obtained by a polyfunctional coupling agent is used to increase the holding power of the pressure-sensitive adhesive composition. As a method for efficiently producing such a branched block copolymer, For example, styrene is polymerized in the presence of an organolithium initiator, then isoprene is polymerized, and then a small amount of butadiene is added to form a short butadiene block at the polymerization end of the isoprene polymer block, and then polyfunctional coupling is performed. A production method of performing a coupling reaction using an agent has been recently reported (International Publication No. WO 92/20725). However, in this case, although a branched block copolymer can be obtained with a high coupling rate, a pressure-sensitive adhesive composition containing such a block copolymer as a base polymer is inferior in initial adhesive strength and has a balance as a pressure-sensitive adhesive. It lacks.

In order to obtain a good balance as such an adhesive, it has been studied to use a branched block copolymer and a linear block copolymer in combination (see, for example, Japanese Patent Laid-Open Publication No. Sho. 51-26938, JP-A-61-26647, etc.). However, conventionally known block copolymer-based thermoplastic elastomers are
The thermal stability is poor. For example, in the case of a SIS type block copolymer, the viscosity of the melt rapidly decreases due to thermal deterioration during melt processing, while in the case of an SBS type block copolymer, the melting During processing, the viscosity of the melt rapidly rises due to cross-linking. In addition, even in a blended system of both of these, the melt viscosity shows a sharp increase due to a change with time when heated. Therefore, it is difficult for the hot-melt pressure-sensitive adhesive using these block copolymers as a base polymer to secure stable quality during processing and coating work, and further, high holding power while securing thermal stability. Is difficult to show.

[0005]

An object of the present invention is to provide a block copolymer composition having properties as a thermoplastic elastomer and excellent thermal stability. Another object of the present invention is to provide a pressure-sensitive adhesive composition that exhibits high holding power and is excellent in thermal stability. The inventors of the present invention have conducted extensive studies to overcome the above-mentioned problems of the prior art, and obtained a (SIB) ₃ -X type block copolymer synthesized using a trifunctional coupling agent. (S-I-
It was found that among the mixture with the B) type block copolymer, a block copolymer composition having a large amount of bound butadiene exhibits excellent thermal stability, and the present invention has been completed based on this finding.

[0006]

Thus, according to the present invention, the following [1] and [2] are provided. [1] The block copolymer (1) represented by the general formula (S-IB) _n- X and the general formula (S-IB) or (S-).
The block copolymer (2) represented by B-I) is contained, and the weight of (1) and (2) is (1) / (2) = 2.
0/80 to 90/10 (weight ratio), and the weight of I and B is I / B = 10/90 to 45/55 (weight ratio), a block copolymer composition characterized by the following: . (In the formula,
S is a polymer block of an aromatic vinyl compound. B is Ri butadiene polymer block der, butadiene portion
The proportion of 1,2-vinyl bonds Ru der than 15%. I is Ri isoprene polymer block der, 3 isoprene portion,
The proportion of 4-vinyl bonds Ru der than 10%. n is 3 or 4. X is a residue of a trifunctional or tetrafunctional coupling agent. [2] A pressure-sensitive adhesive composition comprising 100 parts by weight of the block copolymer composition of [1] and 50 to 300 parts by weight of a tackifier.

The block copolymer (1) used in the block copolymer composition of the present invention has the general formula (S
-IB) A block copolymer represented by _n- X, wherein
Polymer block S of aromatic vinyl compound, polymer block I of isoprene, and polymer block B of butadiene
A branched block copolymer having a structure obtained by coupling a polymerization active terminal of a (S-IB) type block copolymer consisting of and with a trifunctional or tetrafunctional coupling agent. A polymer (wherein n is 3 or 4)
Is. X is the residue of the coupling agent).

The polystyrene-equivalent weight average molecular weight of the block copolymer (1) measured by gel permeation chromatography (GPC) is 50,000 to 50.
50,000, preferably 100,000 to 400,000
It is 0. When the molecular weight is less than the lower limit, the holding power of the obtained pressure-sensitive adhesive composition becomes insufficient, and when it exceeds the upper limit, the processability of the obtained pressure-sensitive adhesive composition becomes unsatisfactory.

S, B and I in the general formula are respectively
Including the case where the polymer block is substantially an aromatic vinyl compound block, the substantially butadiene polymer block, and the substantially isoprene polymer block. Here, “substantially” means that, when the units each contain a small amount of a bonding unit derived from another copolymerization component, B or I contains a small amount of a styrene unit in a gradually increasing ratio from one end to the other end of the block. It means the case where it is a tapered block polymer contained, or the case where at least part of B or I is modified by hydrogenation.

Examples of the aromatic vinyl compound used in the block copolymer (1) include styrene and α-
Methyl styrene, p-methyl styrene, m-methyl styrene, o-methyl styrene, p-tert-butyl styrene, dimethyl styrene, vinyl naphthalene, etc. can be mentioned. Of these, styrene is particularly preferable from the viewpoints of availability, reactivity, physical properties of the block copolymer, and the like.

The block copolymer (2) used in the block copolymer composition of the present invention has the general formula (S) as described above.
-IB) or (SB-I), which is a block copolymer obtained by block copolymerizing an aromatic vinyl compound, isoprene and butadiene.

The aromatic vinyl compound used in the block copolymer (2) includes the block copolymer (2)
Compounds similar to those used in the synthesis of are used.

The polystyrene reduced weight average molecular weight of the block copolymer (2) measured by gel permeation chromatography (GPC) is 10,000 to 30.
50,000, preferably 20,000 to 250,000
Is. When the molecular weight is less than the lower limit, the holding power of the obtained pressure-sensitive adhesive composition becomes insufficient, and when it exceeds the upper limit, the processability of the obtained pressure-sensitive adhesive composition becomes unsatisfactory.

Block copolymer (1) used in the present invention
In and (2), the proportion of the bound aromatic vinyl compound is 10 to 50% by weight, preferably 15 to 45% by weight, and the proportion of the bound butadiene is 10 to 60% by weight, preferably 15 to 45%. % Of bound isoprene, preferably 25 to 5% by weight.
It is 5% by weight.

When the proportion of the bound aromatic vinyl compound is less than 10% by weight, the holding power is lowered when the block copolymer is used as the base polymer of the pressure-sensitive adhesive, and conversely, when it exceeds 50% by weight, Tackiness (tackiness) is reduced. If the proportion of bound butadiene is less than 10% by weight, the melt viscosity of the block copolymer will decrease with time and the holding power will decrease, while if it exceeds 60% by weight, the melt viscosity will increase with time. The ratio of bound isoprene is 10
If it is less than wt%, the melt viscosity of the block copolymer will increase with time, and conversely, if it exceeds 60 wt%, the melt viscosity will decrease with time and the holding power will decrease.

Further, in the present invention, the weight ratio of bound isoprene to bound butadiene is I / B = 10/90.
~ 45/55 (weight ratio), preferably 15 / 85-40
It is necessary to be / 60 (weight ratio). When the weight ratio of bound isoprene to bound butadiene is less than 10/90, the melt viscosity of the block copolymer increases with the lapse of time, and the adhesive strength and holding power decrease, and conversely, when it exceeds 45/55, melting occurs. Viscosity decreases with the lapse of time, and heat resistance decreases.

When the ratio of the bound styrene, the bound isoprene and the bound butadiene is within the above range, when the resulting block copolymer is used as a base polymer of a pressure-sensitive adhesive, the initial adhesive force, the adhesive force and the holding force are improved. In any case, an excellent pressure sensitive adhesive can be obtained. When the ratio of bound butadiene and bound isoprene is within the above range, a block copolymer having excellent heat resistance and having little change in melt viscosity during melt processing can be obtained.

Block copolymer (1) used in the present invention
In and (2), the proportion of 1,2-vinyl bonds in the butadiene portion is usually 15% or less and 3,4 in the isoprene portion is usually used.
-The proportion of vinyl bonds is 10% or less. Further, the block copolymers (1) and (2) used in the present invention usually have a storage elastic modulus (G ′) in viscoelasticity measurement of 0 ° C. to
In the range of 50 ° C., the peak of loss tangent (tan δ) at 10 ^{5 to} 3 × 10 ⁸ Pa and due to the butadiene polymer block and the isoprene polymer block is
There is only one in the range -80 ° C to -50 ° C. For example, S-I-S type block copolymer and S-B-
When the S-type block copolymer is blended, the peak of loss tangent (tan δ) due to each of the butadiene polymer block and the isoprene polymer block is
Two appear in the range of -80 ° C to -50 ° C. When the composition comprising the block copolymers (1) and (2) having a storage elastic modulus (G ') of less than 10 ⁵ Pa is used as the base polymer of the pressure-sensitive adhesive, the holding power is lowered and, conversely, 3 ×. 10
^If it exceeds ⁸ Pa, the tackiness decreases, which is not preferable.

Block copolymer used in the present invention (1)
The trifunctional or tetrafunctional coupling agent used for synthesizing is not particularly limited, and examples of the coupling agent include, for example, tin-based coupling agents such as methyltrichlorotin and tetrachlorotin; tetrachloride. Examples thereof include silicon halide-based coupling agents such as silicon and tetrabromosilicon; alkoxysilanes such as tetramethoxysilane; halogenated alkanes such as chloroform, trichloroethane, trichloropropane and tribromopropane. Among these, tetramethoxysilane and the like are preferable.

Block copolymer (1) used in the present invention
And (2) can be produced by a conventionally known method by using an organolithium compound as a polymerization initiator in a hydrocarbon solvent and sequentially polymerizing each polymer block. However, in each block copolymer represented by the general formula (1), after sequentially polymerizing a polymer block of S-IB, a coupling reaction is performed with a coupling agent using an active terminal. Can be obtained.

The block copolymer represented by the general formula (1) is prepared by first polymerizing an aromatic vinyl compound in a hydrocarbon solvent using an organic lithium compound as a polymerization initiator, and then polymerizing isoprene and butadiene. Can be obtained by sequentially performing the polymerization of, then adding a trifunctional or tetrafunctional coupling agent, and performing a coupling reaction utilizing the active terminal.

Further, the block copolymer represented by the general formula (2) is obtained by first polymerizing an aromatic vinyl compound in a hydrocarbon solvent using an organic lithium compound as a polymerization initiator, and then polymerizing isoprene and butadiene. It can be obtained by sequentially performing the polymerization of. The order of the polymerization of isoprene and the polymerization of butadiene may be reversed.

The hydrocarbon solvent used for producing the block copolymer includes, for example, cyclopentane, cyclohexane, benzene, ethylbenzene, xylene, and a mixed solvent thereof with pentane, hexane, heptane, butane, and the like. .

Examples of the organolithium compound used as the polymerization initiator include n-butyllithium and sec.
-Butyllithium, tert-butyllithium, n-hexyllithium, iso-hexyllithium, phenyllithium, naphthyllithium and the like can be mentioned, and usually used in the range of 0.01 to 1 part by weight per 100 parts by weight of the monomer.

The block copolymer composition of the present invention is obtained by separately synthesizing the block copolymers (1) and (2) and then mixing them in the above weight ratio by an arbitrary method. The type and amount of a trifunctional or tetrafunctional coupling agent when coupling a (S-I-B) type block copolymer having a polymerization active end of a polymer block of butadiene. It is also possible to obtain the block copolymer composition of the present invention at one time by controlling the above, and if necessary, by using a known coupling accelerator together.

The method of mixing the block copolymers (1) and (2) for obtaining the block copolymer composition of the present invention is not particularly limited, and a method of heating and mixing the respective components with a Brabender, a kneader or the like can be used. It can be illustrated.

The block copolymer composition of the present invention comprises: (1) between the weights of the block copolymers (1) and (2).
/ (2) = 20/80 to 90/10 (weight ratio), preferably (1) / (2) = 25/75 to 85/15 (weight ratio). (1) /
If (2) is less than 20/80 (weight ratio), the holding power as an adhesive decreases, which is not preferable. If (1) / (2) exceeds 90/10 (weight ratio), the adhesive strength, holding power, and heat resistance of the adhesive will be reduced, which is not preferable.

The block copolymer composition of the present invention can be used as a base polymer for adhesives, and in particular,
It can be suitably used as a base polymer of a hot-melt pressure-sensitive adhesive composition by utilizing the properties and thermal stability as a thermoplastic elastomer. Such an adhesive composition comprises 100 parts by weight of the block copolymer composition and a tackifier 5
It contains 0 to 300 parts by weight. In addition, the softener 0-10
You may mix | blend in the ratio of 0 weight part.

The tackifier has a number average molecular weight of 30.
A low molecular weight resin having a softening point of 0 to 3,000 and a softening point of 60 to 130 ° C. based on the ring and ball method defined in JIS K-2207 can be preferably used. Specific examples include, for example, rosin and rosin derivatives, polyterpene resins, aromatic modified terpene resins and hydrides thereof, terpene phenol resins, coumarone indene resins, aliphatic petroleum resins, aromatic petroleum resins and hydrides thereof. , Aliphatic / aromatic copolymer petroleum resins, dicyclopentadiene petroleum resins and hydrides thereof, and low molecular weight polymers of styrene or substituted styrene.

As the tackifier, those which are compatible with the butadiene polymer block or the isoprene polymer block of the block copolymer are preferable, for example, polyterpene resin, aliphatic petroleum resin, hydride of aromatic petroleum resin. Are preferred. Further, for the purpose of improving the cohesive force of the pressure-sensitive adhesive composition, a coumarone / indene resin or a low molecular weight polymer of styrene or substituted styrene compatible with the aromatic vinyl compound polymer block is mixed with the conjugated diene polymer block. You may mix with a melt | dissolving tackifier.

Examples of the softening agent include petroleum-based process oils such as paraffin-based process oil, naphthene-based process oil and aromatic process oil; castor oil,
Natural oils such as tall oil; dialkyl dibasic acids such as dibutyl phthalate, dioctyl phthalate and dibutyl adipate; low molecular weight liquid polymers such as liquid polybutene and liquid polyisoprene. Among these, if paraffinic process oil or liquid polybutene is used,
It is possible to obtain a pressure-sensitive adhesive that is particularly stable against heat and ultraviolet rays and has an excellent color tone.

In the pressure-sensitive adhesive composition, the proportion of the tackifier used is 100 parts by weight of the block copolymer composition.
The amount is 50 to 300 parts by weight, preferably 30 to 180 parts by weight. If the proportion of the tackifier is less than 50 parts by weight, the tackiness is lowered, and conversely, if it exceeds 300 parts by weight, the holding power is lowered. The softening agent is used in an amount of 0 to 100 parts by weight, preferably 5 to 150 parts by weight, more preferably 10 parts by weight.
~ 130 parts by weight. If this ratio is deviated, it is difficult to obtain balanced physical properties as an adhesive. The rubber composition may be blended with other rubber components within a range that does not impair the object of the present invention, and further, if desired, may be blended with additives such as antioxidants, pigments and fillers as appropriate. be able to.

The method for producing the pressure-sensitive adhesive composition is not particularly limited, and is a mechanical mixing method using a roll, a Banbury mixer, a tarton kneader, a melting pot equipped with a stirrer, or a uniaxial or biaxial extruder. Any method such as a hot-melt method characterized by heating and mixing using an extruder, a solvent method in which a blending component is put into a suitable solvent and a uniform solution of the pressure-sensitive adhesive composition is obtained by stirring the mixture. Can also be used. The pressure-sensitive adhesive composition is a solvent-free solution, or a solution thereof is uniformly applied to a support such as paper and a plastic film by using a suitable applicator, and if necessary, dried by various adhesive tapes or An adhesive sheet can be manufactured.

The block copolymer composition of the present invention is excellent in thermal stability and has little change in melt viscosity with time during heating and melting. It can be suitably used as a melt-type pressure-sensitive adhesive composition. Since the hot-melt pressure-sensitive adhesive composition of the present invention has little change in melt viscosity with time even when the melting temperature is raised, it can be coated on a support with good fluidity without solvent by melting. Alternatively, the pressure-sensitive adhesive composition may be used as an adhesive or sealant by being fluidized by a method such as melting with heat or dissolving in a suitable solvent without being applied to a support.

Further, the block copolymer composition of the present invention, in addition to the use of the above-mentioned pressure-sensitive adhesive composition, makes use of its characteristics,
For example, sheet film, injection molded products of various shapes, molded product applications such as hollow molded products, modifiers of various thermoplastic resins,
It can be applied to footwear materials, asphalt modifiers, wire cable materials, vulcanized rubber materials, vulcanized rubber modifiers, home appliances, automobile parts, industrial parts, household products, toys, etc. .

[0036]

EXAMPLES The present invention will be described more specifically below with reference to examples. The parts and% in the examples are based on weight unless otherwise specified. In addition, the measuring method of the physical property in the following examples is as follows. <Amount of bound styrene, amount of bound butadiene, amount of bound isoprene> It was measured by the NMR (nuclear magnetic resonance absorption) method (unit: wt%). <Weight Average Molecular Weight> The weight average molecular weight of the block copolymer is measured by high performance liquid chromatography (HCL-802A,
From the molecular weight distribution curve measured using
It was calculated based on a calibration curve obtained from the analysis results of standard polystyrene of known molecular weight. For the measurement, a column G-4000H and a column G-5000 filled with polystyrene gel were used in combination, the column temperature was 40 ° C., the carrier (tetrahydrofuran) flow rate was 1.3 m1 / min, and the sample concentration was 0.1.
It was measured under the condition of 6 g / 1 (unit: × 10 ⁴ ). Also,
The ratio of the block copolymer (1) to the block copolymer (2) in the block copolymer composition was determined from the peak area of each copolymer obtained by high performance liquid chromatography (unit: weight ratio ).

<Adhesive Properties> Preparation of Adhesive Composition An adhesive composition was prepared according to the following formulation and the adhesive properties were measured. Specifically, each component was kneaded with a Dalton kneader according to the following formulation, and the obtained composition was dissolved in toluene (nonvolatile content concentration 50%).
A pressure-sensitive adhesive tape was prepared by applying a paste having a thickness of 25 μm on a polyester film having a thickness of μm. The results are collectively shown in Table 1. [Composition of adhesive composition] Block copolymer composition 100 parts Tackifier (hydrogenated aromatic petroleum resin) 170 parts Softener (paraffinic process oil) 65 parts Antioxidant 1 part

(1) The initial adhesive strength is JIS Z-023.
In accordance with No. 7, at a temperature of 23 ° C. and 10 ° C., an adhesive tape having a length of 10 cm was attached to the slope of a stainless steel plate having an inclination angle of 30 degrees with the adhesive surface facing upward, and a diameter of 3/32 Steel balls of 30 sizes from inch to 32/32 inch are rolled at an initial speed of 0, and the size of the ball with the maximum diameter that stops on the adhesive tape is displayed (5
Average number of ball numbers). (2) Adhesive strength is 280 according to JIS Z-0237.
Width 10 mm on a stainless steel plate that has been polished with No. 1 water-resistant polishing paper
× Adhesive tape with a length of 100 mm is attached at 23 ° C.
Was measured by peeling in the direction of 180 degrees at a speed of 200 mm / min (unit: g / cm). (3) In accordance with JIS Z-0237, the holding power is such that an adhesive tape is attached to a stainless steel plate treated in the same manner as described above so that an area of 25 mm × 10 mm is in contact, and a load of 1 kg is applied at 50 ° C. The time required for falling off the stainless steel plate was measured (unit: min). (4) Heat resistance test (S.A.F.T .: Shear A)
dhesive Failure Template
re) A pressure-sensitive adhesive tape is attached to a stainless steel plate so that an area of 25 mm × 10 mm is in contact with it, heated at 40 ° C. for 1 hour, applied with a load of 1 kg, and heated at 0.5 ° C./minute to give The temperature when dropped was measured. The larger the value, the better the thermal stability (unit: ° C).

Reference Example: Synthesis of Block Copolymer Composition (1) In a dry nitrogen atmosphere, in a 3 liter autoclave, 5.7 mmol of n-butyllithium was used as a polymerization initiator in 1500 g of cyclohexane solvent. use,
Styrene, isoprene, and butadiene are sequentially added to perform polymerization, and thereafter, a coupling reaction is performed using tetetramethoxysilane as a coupling agent,
Ten types of block copolymer compositions comprising the (S-I-B) _3- X type block copolymer and the (S-I-B) type block copolymer shown in Table 1 (Examples 1 to 6) And used in Comparative Examples 1 to 4). In the obtained block copolymer composition, the proportion of bound styrene was 30% by weight, the proportion of bound isoprene was 24.5% by weight, and the proportion of bound butadiene was 45.5% by weight. The weight ratio of bound isoprene and bound butadiene is I / B = 35/65 (weight ratio).
(Used in Examples 1 to 3), 20/80 (weight ratio) (used in Examples 4 to 6), 30/70 (weight ratio) (Comparative Example 1,
2)), 90/10 (weight ratio) (used for Comparative Example 3)
And 5/95 (weight ratio) (used in Comparative Example 4).
The weight average molecular weight of the (SIB) ₃ -X type block copolymer was 216,000, and the weight average molecular weight of the (SIB) type block copolymer was 72,000. It was The weight average molecular weight of the block copolymer composition is shown in Table 1. (2) Next, in a dry nitrogen atmosphere, in a 3 liter autoclave, in 1500 g of cyclohexane solvent, n
-Butyllithium (5.7 mmol) was used as a polymerization initiator, and styrene, butadiene and styrene were sequentially added to carry out polymerization to produce an (S-B-S) type block copolymer. The resulting block copolymer has a bound styrene content of 40% by weight and a bound butadiene content of 60% by weight. The weight average molecular weight was 148,000. (3) Similarly, in a cyclohexane solvent, n
-Butyllithium was used as a polymerization initiator, and styrene, isoprene and styrene were sequentially added to carry out polymerization to produce a (S-I-S) type block copolymer. The bound styrene content of the obtained block copolymer composition was 1
5% by weight, the proportion of bound isoprene was 85% by weight, and the weight average molecular weight was 150,000.

(Examples 1 to 6) Of the 10 kinds of block copolymer compositions prepared in (1) in Reference Example, I / B = 35.
A pressure-sensitive adhesive composition was prepared using 6 types of / 65 and 20/80, and the physical properties of the pressure-sensitive adhesive and the thermal stability test were performed. The results are shown in Table 1.

(Comparative Examples 1 and 2) Among the block copolymer compositions produced in (1) in Reference Example, (SIB) ₃ -X type block copolymer and (SIB) were prepared. A pressure-sensitive adhesive composition was prepared using two types of block copolymer compositions whose ratio with the block copolymer was outside the range specified in the present invention, and the adhesive physical properties were measured and the thermal stability test was conducted. The results are shown in Table 1.

(Comparative Examples 3 and 4) Among the block copolymer compositions produced in (1) in Reference Example, two kinds of block copolymer compositions having I / B outside the range specified in the present invention were used. A pressure-sensitive adhesive composition was prepared by the above method, and the physical properties of the pressure-sensitive adhesive and the thermal stability test were performed. The results are shown in Table 1.

(Comparative example 5) (2) manufactured in the reference example (S)
An adhesive composition was prepared using the -BS) type block copolymer, and the adhesive physical properties were measured and the thermal stability test was performed. The results are shown in Table 1.

(Comparative Example 6) (2) manufactured in the reference example (S
50-50 of the (BS) type block copolymer and the (S-I-S) type block copolymer (3) produced in Reference Example.
An adhesive composition was prepared using the block copolymer composition mixed in (weight ratio), and the adhesive physical properties were measured and the thermal stability test was performed. The results are shown in Table 1.

[0045]

[Table 1]

As is clear from the results shown in Table 1, the pressure-sensitive adhesive compositions (Examples 1 to 6) using the block copolymer composition of the present invention have a high pressure-sensitive adhesive force and a high holding power, and are thermally stable. It can be seen that the property is good. On the other hand, (S-IB)
_When a block copolymer composition in which the ratio of the _3- X type block copolymer to the (S-IB) type block copolymer is outside the range specified by the present invention is used (Comparative Examples 1 and 2). And using a block copolymer composition in which I / B is out of the range specified in the present invention (Comparative Examples 3 and 4), and
When the (S-B-S) type block copolymer or the (S-I-S) type block copolymer was used (Comparative Examples 5 and 6), the balance of the adhesive physical properties was poor and the thermal stability was poor. It turns out that is bad.

Specific embodiments of the present invention are as follows. (1) The block copolymer (1) represented by the general formula (S-IB) _n- X, and the general formula (S-IB) or (S-
The block copolymer (2) represented by B-I) is contained, and the weight of (1) and (2) is (1) / (2) = 20.
/ 80 to 90/10 (weight ratio), and the weight of I and B is I / B = 10/90 to 45/55 (weight ratio), a block copolymer composition characterized by the above-mentioned. (In the formula, S is a polymer block of an aromatic vinyl compound. B is a butadiene polymer block. I is an isoprene polymer block. N is 3 or 4. X is trifunctional or tetrafunctional. It is a residue of a coupling agent.) (2) The block copolymer composition of (1), wherein the aromatic vinyl compound is styrene. (3) The block copolymer composition according to (1), wherein the proportion of the aromatic vinyl compound is 10 to 20% by weight, the proportion of the bound butadiene is 15 to 45% by weight, and the proportion of the bound isoprene is 20 to 70% by weight. (4) The block copolymer composition of (1), wherein n is 3. (5) The weight average molecular weight of the block copolymer of the general formula (1) is 50,000 to 500,000, and the weight average molecular weight of the block copolymer of the general formula (2) is 10,0.
The block copolymer composition of (1) which is 00 to 300,000. (6) A pressure-sensitive adhesive composition obtained by mixing 100 parts by weight of the block copolymer composition of (1) and 50 to 300 parts by weight of a tackifier. (7) A pressure-sensitive adhesive composition comprising 100 parts by weight of the block copolymer composition of (1) and 80 to 180 parts by weight of a tackifier. (8) 100 parts by weight of the block copolymer composition of (1), 80 to 180 parts by weight of a tackifier, and 5 to 150 of a softening agent.
A pressure-sensitive adhesive composition containing 1 part by weight.

[0048]

According to the present invention, there is provided a novel block copolymer composition having properties as a thermoplastic elastomer and having little change in melt viscosity with time during heating and melt processing and having excellent thermal stability. To be done. Further, the pressure-sensitive adhesive composition using the block copolymer composition excellent in heat stability of the present invention as a base polymer has a particularly high adhesive strength and holding power, and is a hot-melt pressure-sensitive adhesive composition excellent in heat stability. It is useful as a thing.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-102212 (JP, A) International Publication 92/20725 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 53/00-53/02 C09J 153/02

Claims (2)

(57) [Claims] 1. A general formula (S-I-B) Bed represented by _n -X
It contains a lock copolymer (1) and a block copolymer (2) represented by the general formula (S-IB) or (SB-I), Weight is (1) / (2)
= 20/80 to 90/10 (weight ratio), and the weight of I and B is I / B = 10/90 to 45/55 (weight ratio)
And a block copolymer composition. (In the formula, S is a polymer block of an aromatic vinyl compound.
B is Ri butadiene polymer block der, butadiene part
1,2 percentage vinyl bonds Ru der than 15%. I is Ri isoprene polymer block der, isoprene portion
The proportion of 3,4-vinyl bond is Ru der than 10%. n is 3
Or 4. X is a residue of a trifunctional or tetrafunctional coupling agent. ) 2. The block copolymer composition 10 according to claim 1.
A pressure-sensitive adhesive composition comprising 0 part by weight and 50 to 300 parts by weight of a tackifier.