JP3339170B2 - Block copolymer 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 novel block copolymer, and more particularly, to a block copolymer suitable for use as a base polymer of a pressure-sensitive adhesive composition which exhibits little change with time in melt viscosity and is particularly excellent in low-temperature properties. The present invention relates to a polymer and a pressure-sensitive adhesive composition containing the block copolymer.

[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 pressure-sensitive adhesive composition in which a thermoplastic elastomer such as a block copolymer is used and a SIS block copolymer and an SBS block copolymer are used in combination as a base polymer is also known (JP-B-53-45345). issue). However, conventionally known block copolymer-based thermoplastic elastomers have poor thermal stability. For example, in the case of SIS type block copolymers, the viscosity of the melt is rapidly reduced due to thermal degradation during melt processing, while In the case of the SBS type block copolymer, crosslinkage occurs during melt processing, and the viscosity of the melt rises sharply. In addition, even in the case of a blend system of both, the melt viscosity during heating shows a rapid rise due to a change over time. Therefore, it is difficult for a hot-melt pressure-sensitive adhesive containing such a block copolymer as a base polymer to ensure stable quality during processing and coating.

In order to satisfy the required performance, the applicant has a SBIS type or polyfunctional coupling having a butadiene polymer block and an isoprene polymer block, which has little change in melt viscosity with time and excellent heat stability. (SBI) _n -X type block copolymer (X represents a residue of a polyfunctional coupling agent) using an agent (Japanese Patent Application No. 4-262807). Although pressure-sensitive adhesives using these block copolymers as base polymers have a good balance of pressure-sensitive adhesive properties, further improvements are required in low-temperature properties required for pressure-sensitive adhesive tapes and the like used in cold regions.
Also, recently, styrene is polymerized in the presence of an organolithium initiator, and then isoprene is added and polymerized.
After adding a small amount of butadiene to form a short butadiene polymer block at the polymerization end of the isoprene polymer block, coupling is performed using a polyfunctional coupling agent to obtain a branch obtained by increasing the coupling efficiency. A SIS type block copolymer has been reported (WO 92/20725). However, in this case,
The amount of bound styrene is 25% by weight or more, and the pressure-sensitive adhesive using such a block copolymer as a base polymer has high holding power, but it is difficult to obtain a pressure-sensitive adhesive having good low-temperature characteristics.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermoplastic elastomer which has little change in melt viscosity with time during heat melting processing, has excellent heat stability, and has excellent low temperature properties. An object of the present invention is to provide a novel block copolymer. Another object of the present invention is to provide a pressure-sensitive adhesive composition having excellent low-temperature properties and a good balance of adhesive properties such as holding power. We have:
As a result of intensive studies to overcome the problems of the prior art, (S-B-I-S) type, (S-B-I) _n X-type, or (S-I-B) _n X-type were investigated. A block copolymer, which is a block copolymer having a specific copolymer component ratio and specific physical properties, has properties as a thermoplastic elastomer and exhibits excellent thermal stability, and furthermore, this is referred to as a base polymer. Pressure sensitive adhesives have been found to exhibit excellent low temperature properties. Since the block copolymer of the present invention has excellent thermal stability, a hot-melt pressure-sensitive adhesive composition using the same as a base polymer has a small change with time in the melt viscosity even when the melting temperature is increased. A pressure-sensitive adhesive tape having excellent workability and fluidity and excellent low-temperature properties can be obtained by using the pressure-sensitive adhesive composition. The present invention has been completed based on these findings.

[0005]

According to the present invention, the following (1) and (2) are provided. (1) (a) The following general formula [1], [2] or [3]
A block copolymer having a structure represented by the formula: (S-B-I-S) [1] (S-B-I) _n -X [2] (S-I-B) _n -X [ 3] (where S is a polymer block of an aromatic vinyl compound; B is a butadiene polymer block; I is an isoprene polymer block; n is an integer of 2 to 4).
X is the residue of a coupling agent. ) (B) the proportion of bound aromatic vinyl compound is 5 to 20% by weight, (c) the proportion of bound butadiene is 10 to 60% by weight, (d) the proportion of bound isoprene is 10 to 80% by weight, (e) storage modulus at elasticity measurement (G ') is, in the range of 0 ° C. to 50 ° C., 10 ⁵ is less than 10 ⁶ Pa or more Pa, block copolymer, characterized in that. (2) An adhesive composition comprising 100 parts by weight of the block copolymer of (1) and 50 to 300 parts by weight of a tackifier.

The block copolymer of the present invention has a structure represented by the following general formula [1], [2] or [3]. (S-B-I-S) [1] (S-B-I) _n -X [2] (S-I-B) _n -X [3] In these formulas, S is an aromatic vinyl compound. B is a butadiene polymer block, and I is
It is an isoprene polymer block. n is an integer of 2 to 4. X is the residue of the coupling agent. S, B and I each include the case where they are substantially a polymer block of an aromatic vinyl compound, substantially a butadiene polymer block, and substantially a isoprene polymer block. Here, the term “substantially” means B or I in the case where a binding unit derived from a small amount of another copolymer component is contained.
Is a tapered block polymer containing a small amount of a styrene unit in a gradually increasing ratio from one end to the other end of the block, or a case where at least a part of B or I is modified by hydrogenation.

The aromatic vinyl compound used in the present invention includes, for example, styrene, α-methylstyrene,
Examples thereof include p-methylstyrene, m-methylstyrene, o-methylstyrene, p-tert-butylstyrene, dimethylstyrene, and vinylnaphthalene. Among these, styrene is particularly preferable from the viewpoints of availability, reactivity, and physical properties of the block copolymer. Butadiene and isoprene are used as the conjugated diene compound.

The block copolymers [1] and [2] of the present invention
And in [3], the proportion of the bound aromatic vinyl compound is 5 to 20% by weight in total, preferably 10 to 20% by weight, and the proportion of the bound butadiene is 10 to 60% by weight.
Preferably, it is 15-45% by weight and the proportion of bound isoprene is 10-80% by weight, preferably 20-70% by weight.

The proportion of the bound aromatic vinyl compound is 5% by weight.
If the amount is less than the above, when the block copolymer is used as the base polymer of the pressure-sensitive adhesive, the holding power is reduced, and conversely, 20% by weight.
If it exceeds, the tackiness (adhesiveness) decreases. When the ratio of the bound butadiene is less than 10% by weight, the melt viscosity of the block copolymer decreases with time, and
If the holding power decreases, and if it exceeds 60% by weight, the melt viscosity increases with the lapse of time. When the ratio of the bound isoprene is less than 10% by weight, the melt viscosity of the block copolymer increases with the lapse of time. Conversely, when it exceeds 80% by weight, the melt viscosity decreases with the lapse of time, and the holding power decreases. descend. When the ratio of the bound styrene, the bound butadiene and the bound isoprene is within the above range, when the obtained block copolymer is used as a base polymer of the pressure-sensitive adhesive, both tackiness, adhesive strength and holding power are good, In addition, an adhesive having excellent low-temperature characteristics can be obtained. Further, when the ratio of the bound butadiene and the bound isoprene is within the above range, it is possible to obtain a block copolymer having excellent heat resistance and a small change in melt viscosity during melt processing.

Each of the block copolymers of the present invention has a weight average molecular weight (in terms of polystyrene) of 10,000 as measured by gel permeation chromatography (GPC).
0 to 500,000, preferably 50,000 to 30
It is in the range of 000. Weight average molecular weight of 10,000
If it is less than 0, the holding power decreases, while 500,00
If it exceeds 0, the tackiness is reduced and the coatability and workability are deteriorated.

In each block copolymer of the present invention, the ratio of 1,2-vinyl bonds in the butadiene portion is 15% or less, and the ratio of 3,4-vinyl bonds in the isoprene portion is 10% or less. Each of the block copolymers of the present invention has a storage elastic modulus (G ') in viscoelasticity measurement of not less than 10 ⁵ Pa and less than 10 ⁶ P in a range of 0 ° C. to 50 ° C., and a butadiene polymer block and isoprene. The peak of the loss tangent (tan δ) due to the polymer block is -80 ° C to-
Only one exists in the range of 50 ° C. For example, S
When the -IS type block copolymer and the SBS type block copolymer are blended, the peak of the loss tangent (tan δ) caused by each of the butadiene polymer block and the isoprene polymer block is as follows: -80 ° C to -5
Two appear in the range of 0 ° C. When a block copolymer having a storage modulus (G ') of less than 10 ⁵ Pa is used as the base polymer of the pressure-sensitive adhesive, the holding power is reduced, and conversely, 10 ⁶ P
If it exceeds a, the low-temperature tackiness (adhesiveness) will decrease.

Examples of the coupling agent include dichlorotin, monomethyldichlorotin, dimethyldichlorotin, monoethyldichlorotin, diethyldichlorotin,
Tin-based coupling agents such as methyltrichlorotin, monobutyldichlorotin, dibutyldibromotin, monohexyldichlorotin, and tetrachlorotin; for example, dichlorosilane, monomethyldichlorosilane, dimethyldichlorosilane, monoethyldichlorosilane, diethyldichlorosilane Silicon halide coupling agents such as, monobutyldichlorosilane, dibutyldichlorosilane, monohexyldichlorosilane, dihexyldichlorosilane, cybromosilane, monomethyldibromosilane, dimethyldibromosilane, silicon tetrachloride, and tetrabromosilicon;
Alkoxysilanes such as tetramethoxysilane; divinyl aromatic compounds such as divinylbenzene and divinylnaphthalene; halogens such as dichloroethane, dibromoethane, methylene chloride, dibromomethane, dichloropropane, dibromopropane, chloroform, trichloroethane, trichloropropane, and tribromopropane Alkane; halogenated aromatic compounds such as dibromobenzene; benzoate, CO, 2-chloropropene, 1
Other coupling agents such as -chloro-1,3-butadiene; Among these, dibromobenzene and tetramethoxysilane are preferred.

(Production Method of Block Copolymer) The block copolymers [1], [2] and [3] of the present invention can be prepared by subjecting an organic lithium compound to a polymerization initiator in a hydrocarbon solvent by a conventionally known method. And can be produced by sequentially polymerizing each polymer block. However,
Each of the block copolymers represented by the general formulas [2] and [3] is obtained by sequentially polymerizing each polymer block of SBI or SIB, and then using an active terminal to form a cup. It can be obtained by performing a coupling reaction with a ring agent. Examples of the hydrocarbon solvent used for producing the block copolymer include cyclopentane, cyclohexane, benzene, ethylbenzene, xylene, and a mixed solvent thereof with pentane, hexane, heptane, butane and the like. Examples of the organic lithium compound used as the polymerization initiator include, for example, n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, iso-hexyllithium, phenyllithium, naphthyllithium, and the like. , 0.01 to 1 per 100 parts by weight of monomer
Used in parts by weight.

The block copolymer represented by the general formula [1] is obtained by (1) first polymerizing an aromatic vinyl compound in a hydrocarbon solvent using an organolithium compound as a polymerization initiator,
Next, (2) polymerization of butadiene, (3) polymerization of isoprene, and (4) polymerization of an aromatic vinyl compound can be obtained by sequentially performing the polymerization. Although the order of polymerization of isoprene and polymerization of butadiene may be reversed, it is preferable to polymerize isoprene after polymerizing butadiene from the viewpoint of productivity. The block copolymer represented by the general formula [2] is obtained by (1) first polymerizing an aromatic vinyl compound in a hydrocarbon solvent using an organic lithium compound as a polymerization initiator, and then (2) polymerizing butadiene. And (3) isoprene can be obtained by sequentially polymerizing, followed by adding a coupling agent and performing a coupling reaction using an active terminal. The block copolymer represented by the general formula [3] is obtained by (1) polymerizing an aromatic vinyl compound in a hydrocarbon solvent using an organic lithium compound as a polymerization initiator, and then (2) polymerizing isoprene. And (3) butadiene can be obtained by successively polymerizing butadiene, followed by adding a coupling agent and performing a coupling reaction using an active terminal. In the coupling reaction, n is preferably 2 or 3.

(Adhesive Composition) The block copolymers [1], [2] and [3] of the present invention can be used as a base polymer of an adhesive, and particularly have properties as a thermoplastic elastomer. Utilizing thermal stability, it can be suitably used as a base polymer of a hot-melt pressure-sensitive adhesive composition. Such a pressure-sensitive adhesive composition comprises 100 parts by weight of at least one block copolymer selected from the group consisting of the block copolymers [1], [2] and [3];
Contains 50 to 300 parts by weight of a tackifier. Moreover, you may mix | blend a softener in the ratio of 0-100 weight part.

The tackifier has a number average molecular weight of 30.
A low molecular weight resin having a softening point of 60 to 130 ° C based on the ring and ball method specified in JIS K-2207 can be preferably used. Specific examples include, for example, rosin and rosin derivatives, polyterpene resins, aromatic modified terpene resins and their hydrides, terpene phenol resins, cumarone-indene resins, aliphatic petroleum resins, aromatic petroleum resins and hydrides thereof And 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, hydrides of polyterpene resin, aliphatic petroleum resin and aromatic petroleum resin are preferable. 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 | blend with the tackifier which melt | dissolves.

Examples of the softener include petroleum-based process oils such as paraffin-based process oils, naphthene-based process oils, and aromatic-based process oils; 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 them, if paraffin-based process oil or liquid polybutene is used,
An adhesive which is particularly stable to heat and ultraviolet rays and has an excellent color tone can be obtained.

In the pressure-sensitive adhesive composition, the use ratio of the tackifier is from 50 to 100 parts by weight based on 100 parts by weight of the block copolymer.
It is 300 parts by weight, preferably 80 to 180 parts by weight.
When the proportion of the tackifier is less than 50 parts by weight, the tackiness decreases, and when it exceeds 300 parts by weight, the holding power decreases. The use ratio of the softener is 0 to 100 parts by weight, preferably 5 to 150 parts by weight, more preferably 10 to 13 parts by weight.
0 parts by weight. If the ratio is outside this range, it is difficult to obtain balanced physical properties as an adhesive.

The pressure-sensitive adhesive composition may contain other rubber components as long as the object of the present invention is not impaired. Further, if necessary, additives such as antioxidants, pigments and fillers may be added. They can be appropriately blended.

The method for producing the pressure-sensitive adhesive composition is not particularly limited, and may be a mechanical mixing method using a roll, a Banbury mixer, a Talton kneader, or the like, a melting pot equipped with a stirrer, or a uniaxial or biaxial. Any method such as a hot melt method characterized by heating and mixing using an extruder, and a solvent method of adding a compounding component to an appropriate solvent and stirring the mixture to obtain a uniform solution of the pressure-sensitive adhesive composition. Can also be used. The pressure-sensitive adhesive composition, without solvent, or a solution thereof, paper, uniformly coated on a support such as a plastic film using a suitable coating machine, and dried if necessary, various adhesive tapes and An adhesive sheet can be manufactured.

Each of the block copolymers of the present invention is excellent in thermal stability and has little change with time in melt viscosity during heating and melting. It can be suitably used as a mold adhesive composition. The hot-melt pressure-sensitive adhesive composition of the present invention,
Even if the melting temperature is increased, the change in the melt viscosity with time is small,
By melting, it can be coated on a support with good fluidity even without solvent. Also, the pressure-sensitive adhesive composition can be used as an adhesive or a sealant by fluidizing it by a method such as melting it with heat or dissolving it in an appropriate solvent without applying it to a support.

The block copolymer of the present invention can be used for molded articles such as sheet films, injection molded articles of various shapes, hollow molded articles, etc. by taking advantage of the characteristics thereof in addition to the use of the above-mentioned pressure-sensitive adhesive composition. , Various thermoplastic resin modifiers, footwear materials, asphalt modifiers, wire and cable materials, vulcanized rubber materials, vulcanized rubber modifiers, home appliances, automotive parts,
It can be applied to materials such as industrial parts, household goods, and toys.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following examples, parts and% are based on weight unless otherwise specified. The methods for measuring physical properties in the following examples are as follows. <Amount of bound styrene, bound butadiene, bound isoprene> Measured by NMR (nuclear magnetic resonance absorption) method (unit:% by weight). <Weight average molecular weight> The weight average molecular weight of the block copolymer was determined by high performance liquid chromatography (HCL-802A,
From the molecular weight distribution curve measured using Tosoh Corporation)
It was calculated based on a calibration curve obtained from the analysis result of standard polystyrene having a known molecular weight. For the measurement, a column G-4000H and G-5000 packed with polystyrene gel were used in combination, the column temperature was 40 ° C., the flow rate of the carrier (tetrahydrofuran) was 1.3 ml / min, and the sample concentration was 0.
It was measured under the condition of 6 g / 1 (unit: × 10 ⁴ ). <Melt Viscosity> The change with time of the melt viscosity was determined by comparing the melt viscosity of the block copolymer after 5 minutes, 10 minutes, and 15 minutes with respect to the initial melt viscosity (0 minute) measured by a flow tester at 240 ° C. Expressed as a ratio. If this value is 1.
A value closer to 0 indicates that the change with time of the melt viscosity is small and the thermal stability is excellent.

<Measurement of viscoelasticity> G '(storage elastic modulus),
The measurement conditions for G ″ (loss modulus) and tan δ (loss tangent) are as follows: Apparatus: Rheometrics Dynamic Analyzer II (RDA II) (manufactured by Rheometrics) Test method: torsion rectangular -Test specimen: length 42mm x width 12.5mm x thickness 2m
m strip test piece Frequency: 6.28 rad / sec Measurement temperature range: -100 ° C to 120 ° C The result of the viscoelasticity measurement of the block copolymer is G ′ at 25 ° C (unit: × 10 ⁵ Pa). And the peak temperature of tan δ (unit: ° C.) are shown in Table 1.

<Adhesive Properties> An adhesive solution having a nonvolatile content of 50% was prepared, and this solution was applied on a 25 μm thick polyester film so as to have an adhesive thickness of 25 μm to prepare an adhesive tape. The tackiness, adhesion and holding power of the tape were measured. (1) According to ASTM D 3121-73, the tackiness is 23 ° C. from a predetermined position on the inclined plate at 21 ° C. for 30 minutes.
And a 3/16 inch diameter steel ball was rolled at 5 ° C., and the pressure-sensitive adhesive surface was exposed upward from the lower end of the inclined plate. The ball was run on the test piece, and the distance until the steel ball stopped was measured and displayed (unit: cm). (2) The adhesive strength is 280 according to JIS Z-0237.
No. 10mm width on stainless steel plate polished with water-resistant abrasive paper
X Adhesive tape with length 100mm, 23 ℃
Was measured in a direction of 180 degrees at a speed of 200 mm × min (unit: g / cm). (3) According to JIS Z-0237, the holding force was applied to a stainless steel plate treated in the same manner as described above so that an adhesive tape of 25 mm × 10 mm was in contact with the stainless steel plate, and a load of 1 kg was applied at 23 ° C. Was measured (unit: minute).

[Examples 1 to 3] Synthesis of block copolymer Under a dry nitrogen atmosphere, a 3 liter autoclave was used.
In 1500 g of a cyclohexane solvent, 5.7 mmol of n-butyllithium was used as a polymerization initiator.
In 5 hours, styrene (ST), butadiene (BD), isoprene (IP) and styrene (ST) were sequentially added to carry out polymerization, and three types of S-B-I-S-type block copolymers shown in Table 1 were obtained. Was manufactured. The total weight of ST, BD and IP used was 400 g. Table 1 shows the measurement results of the weight average molecular weight and the viscoelasticity of each of the obtained block copolymers. Also, from the results of measuring the viscoelasticity of the block copolymer (S-BIS = 9: 25: 57: 9) obtained in Example 3, the block copolymer of the present invention (Example 3) was used.
Is the peak of the loss tangent (tan δ) due to the butadiene polymer block and the isoprene polymer block,
It can be seen that only one exists at −60 ° C.

Preparation of pressure-sensitive adhesive composition A pressure-sensitive adhesive composition was prepared according to the following formulation (the same applies to the following examples), and the pressure-sensitive adhesive properties were measured. Specifically, after kneading each component with a Dalton kneader according to the following formulation, the obtained composition is dissolved in toluene (concentration of nonvolatile content: 50%), and this solution is placed on a 25 μm-thick polyester film. Was applied to a thickness of 25 μm to form an adhesive tape. The results are collectively shown in Table 2. [Blending of adhesive composition] Block copolymer 100 parts Tackifier (hydrogenated aromatic petroleum resin) 100 parts Softener (paraffinic process oil) 20 parts Antioxidant 1 part

[Examples 4 and 5] In a cyclohexane solvent, n-butyllithium was used as a polymerization initiator, and styrene (ST), butadiene (BD) and isoprene (IP) were sequentially added to carry out polymerization. Thereafter, a coupling reaction was carried out using dibromobenzene and tetramethoxysilane as coupling agents, and the (SBI) ₂ -X type and (SBI) ₃ -shown in Table 1 were obtained. X
A mold block copolymer was produced. Table 1 shows the measurement results of the polymerization average molecular weight and the viscoelasticity of each of the obtained block copolymers.
Shown in Table 2 shows the measurement results of the adhesive properties of the PSA compositions prepared using the block copolymers in the same manner as described above.

Comparative Examples 1 to 5 In the same manner as in Examples 1 to 5, block copolymers having a butadiene polymer block or isoprene polymer block ratio outside the range of the present invention were prepared. Table 1 shows the measurement results of the physical properties of these block copolymers. Table 2 shows the measurement results of the adhesive properties of the PSA compositions prepared using the block copolymers in the same manner as described above.

Comparative Examples 6 and 7 SIS and SBS type block copolymers were prepared in the same manner as in Examples 1 to 5. Table 1 shows the measurement results of the physical properties of these block copolymers. Table 2 shows the measurement results of the adhesive properties of the PSA compositions prepared using the block copolymers in the same manner as described above.

[Comparative Examples 8 and 9] The SIS type and SBS type block copolymers prepared in Comparative Examples 6 and 7 were blended by changing the mixing ratio. From the viscoelasticity measurement results of the blend of Comparative Example 8 (SBS / SIS = 29/71), this blend was found to have a loss tangent (t) due to a butadiene polymer block and an isoprene polymer block.
anδ), two peaks were observed at -80 ° C and -51 ° C. Table 1 shows the measurement results of physical properties of the blends of these block copolymers. Table 2 shows the measurement results of the adhesive properties of the adhesive compositions prepared in the same manner as described above using the blends of these block copolymers.

[0033]

[Table 1]

[0034]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the block copolymers of the present invention (Examples 1 to 5) show little change in the melt viscosity with time and are excellent in thermal stability. In addition, it can be seen that the pressure-sensitive adhesive tape using the block copolymer of the present invention as a base polymer has high-level physical properties in both tackiness, adhesive strength and holding power, and is excellent in low-temperature properties. In measuring the adhesive properties, an adhesive tape was prepared by a solution coating method, but of course, an adhesive tape can be directly applied to a base material by a melt processing method using an adhesive composition. it can. On the other hand, the block copolymers in which the ratio of bound styrene is out of the range specified in the present invention (Comparative Examples 1 to 3) have a small change in melt viscosity with time, but none of the pressure-sensitive adhesive compositions using these as a base polymer. The performance of tackiness is inferior, and the low-temperature characteristics are also poor. Block copolymers (Comparative Examples 4 and 5), SIS-type or SBS-type block copolymers (Comparative Examples 6 and 7), and SIS-type in which the ratio of bound butadiene and the ratio of bound isoprene are out of the ranges specified in the present invention. In each of the blends of Comparative Example 8 and 9 with the SBS block copolymer (Comparative Examples 8 and 9), the change in melt viscosity with time was large, and the thermal stability was poor. Further, the pressure-sensitive adhesive composition using the block copolymer or the blend of these comparative examples as a base polymer is inferior in the balance of tack, adhesion and holding power.

The specific embodiments of the present invention are as follows. (1) (a) The following general formula [1], [2] or [3]
A block copolymer having a structure represented by the formula: (S-B-I-S) [1] (S-B-I) _n -X [2] (S-I-B) _n -X [ 3] (where S is a polymer block of an aromatic vinyl compound; B is a butadiene polymer block; I is an isoprene polymer block; n is an integer of 2 to 4).
X is the residue of a coupling agent. ) (B) the proportion of bound aromatic vinyl compound is 5 to 20% by weight, (c) the proportion of bound butadiene is 10 to 60% by weight, (d) the proportion of bound isoprene is 10 to 80% by weight, (e) storage modulus at elasticity measurement (G ') is, in the range of 0 ° C. to 50 ° C., 10 ⁵ is less than 10 ⁶ Pa or more Pa, block copolymer, characterized in that. (2) The block copolymer of (1), wherein the aromatic vinyl compound is styrene. (3) 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 from 20 to 70% by weight. (4) The block copolymer according to (1), wherein n is 2 or 3. (5) Weight average molecular weight of 10,000 to 500,00
The block copolymer according to (1), wherein 0 is 0. (6) An adhesive composition comprising 100 parts by weight of the block copolymer of (1) and 50 to 300 parts by weight of a tackifier. (7) An adhesive composition comprising 100 parts by weight of the block copolymer of (1) and 80 to 180 parts by weight of a tackifier. (8) An adhesive composition comprising 100 parts by weight of the block copolymer of (1), 80 to 180 parts by weight of a tackifier, and 5 to 150 parts by weight of a softener.

[0037]

According to the present invention, there is provided a novel block copolymer which has properties as a thermoplastic elastomer, has little change in melt viscosity with time during heat melting processing, and is excellent in heat stability. . Further, according to the present invention, there is provided a novel block copolymer suitable as a base polymer of a pressure-sensitive adhesive composition, particularly a hot-melt type pressure-sensitive adhesive composition. Further, the pressure-sensitive adhesive composition comprising a novel block copolymer having excellent heat stability of the present invention as a base polymer,
Particularly, it is useful as a hot-melt pressure-sensitive adhesive composition excellent in coating workability, fluidity, and low-temperature characteristics.

Continuation of front page (56) References JP-A-7-238130 (JP, A) JP-A-7-238131 (JP, A) JP-A-6-107745 (JP, A) JP-A-53-8688 (JP) , A) Table 6-509595 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) C08F 297/04 C09J 153/02

Claims (2)

(57) [Claims] (A) a block copolymer having a structure represented by the following general formula [1], [2] or [3], wherein (S-B-IS) [1] (S -BI) _n -X [2] (S-IB) _n -X [3] (wherein, S is a polymer block of an aromatic vinyl compound, and B is a butadiene polymer block. I is an isoprene polymer block, and n is an integer of 2-4.
X is the residue of a coupling agent. ) (B) the proportion of bound aromatic vinyl compound is 5 to 20% by weight, (c) the proportion of bound butadiene is 10 to 60% by weight, (d) the proportion of bound isoprene is 10 to 80% by weight, (e) storage modulus at elasticity measurement (G ') is, in the range of 0 ° C. to 50 ° C., 10 ⁵ is less than 10 ⁶ Pa or more Pa, block copolymer, characterized in that. 2. A pressure-sensitive adhesive composition comprising 100 parts by weight of the block copolymer according to claim 1 and 50 to 300 parts by weight of a tackifier.