JPH06234821A - Tacky agent composition - Google Patents

Abstract

PURPOSE:To obtain a tacky agent composition excellent in thermal stability, coating properties, fluidity, etc., and hardly causing a change in melt viscosity with time in thermal melt processing by blending a new block copolymer with a tackifier. CONSTITUTION:The composition comprises (A) 100 pts.wt. copolymer which is a block copolymer, selected from formulas I to III (S is polymer block of aromatic vinyl compound; B is butadiene polymer block,; I is isoprene polymer block; n is 2-4; X is coupling agent residue) and having 10000-500000 weight- average molecular weight, 10-50wt.% content of combined aromatic vinyl compound, 10-60wt.% respective contents of combined butadiene and combined isoprene, <=15% content of 1,2-vinyl bond in the butadiene part, <=10% content of 3,4-vinyl bond in the isoprene part, 10<6> to 3X10<8> Pa storage elastic modulus at 0-50 deg.C and one peak of loss tangent due to the blocks (B) and (I) present at -80 to +50 deg.C and (B) 20-200 pts.wt. tackifier.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an adhesive composition,
More specifically, the present invention relates to a pressure-sensitive adhesive composition containing a novel block copolymer having a small change in melt viscosity with time as a base polymer.

[0002]

2. Description of the Related Art Conventionally, for example, styrene-isoprene-styrene (SI) has been used as a base polymer for pressure-sensitive adhesives (adhesives) and hot-melt adhesives (hot-melt adhesives).
The use of thermoplastic elastomers such as S) block copolymers and styrene-butadiene-styrene (SBS) block copolymers is a well known technique. Also, a pressure-sensitive adhesive composition in which both a SIS block copolymer and an SBS block copolymer are used together as a base polymer is known (Japanese Patent Publication No. 53-42345).

By the way, the hot-melt type pressure-sensitive adhesive is characterized in that it can be handled in a molten state without using an organic solvent in its manufacturing stage and coating stage. Thermoplastic elastomers such as SIS block copolymers and SBS block copolymers are rubber-like elastic bodies at room temperature, but since they have the property of rapidly falling in viscosity at elevated temperature and entering a fluidized state, they are particularly hot. It is suitable as a base polymer for melt-type pressure-sensitive adhesives.

However, conventionally known block copolymer type thermoplastic elastomers have poor thermal stability. For example, in the case of SIS type block copolymers, the viscosity of the melt is affected by heat deterioration during melt processing. Plummeted while SB
In the case of an S-type block copolymer, the viscosity of the melt rapidly increases due to cross-linking during melt processing. 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, the hot-melt type pressure-sensitive adhesives containing these block copolymers as the base polymer are such that during hot-melt processing, the storage time of the melt until coating and the heating time during processing are shortened as much as possible. In addition, it is necessary to strictly control the melt processing temperature. Therefore, these hot-melt type pressure-sensitive adhesives have a problem of poor coating workability.

On the other hand, in the presence of an organolithium initiator, styrene is first polymerized, and then isoprene and butadiene are sequentially added to carry out polymerization, and then a polyfunctional coupling agent is introduced to perform coupling. Although a method for producing a heat-stable resinous polymer has been proposed (Japanese Patent Publication No. 53-46880), the polymer obtained by this method is a resinous resin having a styrene content of 70 to 95% by weight. However, even if it is used as a base polymer of an adhesive, good adhesive properties cannot be obtained.

[0007]

The object of the present invention is to provide a novel block copolymer 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. It is an object of the present invention to provide a pressure-sensitive adhesive composition containing as a base polymer, in particular, a hot-melt pressure-sensitive adhesive composition having excellent coatability, fluidity, and adhesive physical properties.
The inventors of the present invention have conducted extensive studies to overcome the above-mentioned problems of the prior art, and as a result, (S-B-I-S) type, (S-B-
I) _n- X type or (S-IB) _n- X type block copolymer, wherein the block copolymer having a specific proportion of a specific copolymerization component and specific physical properties is a thermoplastic elastomer. And has excellent thermal stability,
Moreover, it has been found that an adhesive using this as a base polymer exhibits excellent adhesive properties. Since the block copolymer of the present invention is excellent in thermal stability, the hot-melt pressure-sensitive adhesive composition containing the block copolymer as a base polymer has a small change in melt viscosity with time even when the melting temperature is increased, and therefore, the coating composition is Excellent workability and fluidity. The present invention has been completed based on these findings.

[0008]

Thus, according to the present invention, (a) a block copolymer having a structure represented by the following general formula [1], [2] or [3]: -B-I-S) [1] (S-B-I) _n- X [2] (S-IB) _n- X [3] (In the formula, S is a polymer of an aromatic vinyl compound. A block, B is a butadiene polymer block, and I is
It is an isoprene polymer block. n is an integer of 2-4. X is the residue of the coupling agent. ) (B) Weight average molecular weight of 10,000 to 500,000
0, (c) the proportion of bound aromatic vinyl compound is 10 to 50% by weight, (d) the proportion of bound butadiene is 10 to 60% by weight, (e) the proportion of bound isoprene is 10 to 60% by weight, (f) The ratio of 1,2-vinyl bonds in the butadiene portion is 1
5% or less, (g) the ratio of 3,4-vinyl bonds in the isoprene portion is 1
0% or less, (h) Storage elastic modulus (G ′) in viscoelasticity measurement is 0 ° C.
In the range of up to 50 ° C., 10 ^{6 to} 3 × 10 ⁸ Pa, (i) the peak of loss tangent (tan δ) due to the butadiene polymer block and the isoprene polymer block,
At least one block copolymer 10 selected from the group consisting of only one block copolymer [1], [2] and [3] in the range of -80 ° C to -50 ° C.
There is provided a pressure-sensitive adhesive composition containing 0 part by weight and 20 to 200 parts by weight of a tackifier.

The present invention will be described in detail below. (Block Copolymer) The block copolymer used in 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 aroma. Polymer block of group vinyl compound, B is butadiene polymer block, and I is
It is an isoprene polymer block. n is an integer of 2-4. X is the residue of the coupling agent.

S, B and I include the case where they are substantially a polymer block of an aromatic vinyl compound, a substantially butadiene polymer block and a substantially isoprene polymer block, respectively. 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 present invention include 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, physical properties of the block copolymer, and the like. Butadiene and isoprene are used as the conjugated diene compound.

In the block copolymers [1], [2] and [3] used in the present invention, the total proportion of the bound aromatic vinyl compound is 10 to 50% by weight, preferably 15 to 45% by weight. The total proportion of bound butadiene is 10 to 60% by weight, preferably 15 to 45% by weight, and the proportion of bound isoprene is 10 to 6% in total.
It is 0% by weight, preferably 25 to 55% 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, at the same time, the holding power will decrease. On the contrary, if it exceeds 60% by weight, the melt viscosity will change with time. Increase. If the proportion of bound isoprene is less than 10% by weight, the melt viscosity of the block copolymer will increase with time, and if it exceeds 60% by weight, the melt viscosity will decrease with time and the holding power will decrease. To do. When the ratio of bound styrene, bound butadiene and bound isoprene is within the above range, when the resulting block copolymer is used as a base polymer of a pressure-sensitive adhesive, all of tack, adhesive strength and holding power are good. An adhesive can be obtained. Further, 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.

Each block copolymer used in the present invention is
Weight average molecular weight (in terms of polystyrene) measured by gel permeation chromatography (GPC) is 1
50,000 to 500,000, preferably 50,000
˜200,000. Weight average molecular weight is 1
If it is less than 10,000, the holding power will be reduced, while on the other hand, it will be 50
When it exceeds 50,000, tackiness decreases and
The coatability and workability are poor.

Each block copolymer used in the present invention is
The butadiene portion has a 1,2-vinyl bond ratio of 15% or less, and the isoprene portion has a 3,4-vinyl bond ratio of 1 or less.
It is 0% or less. Each block copolymer used in the present invention has a storage elastic modulus (G ') of 0 ° C to
In the range of 50 ° C., the peak of loss tangent (tan δ) at 10 ^{6 to} 3 × 10 ⁸ Pa and due to the butadiene polymer block and the isoprene polymer block was −
There is only one in the range 80 ° C to -50 ° C.
For example, when the S-I-S type block copolymer and the S-B-S type block copolymer are blended, the loss tangent (tan δ) due to the butadiene polymer block and the isopylene polymer block, respectively. Peak is -8
Two appear in the range of 0 ° C to -50 ° C. When a block copolymer having a storage elastic modulus (G ') of less than 10 ⁶ Pa is used as the base polymer of the pressure-sensitive adhesive, the holding power decreases, and conversely, when it exceeds 3 × 10 ⁸ Pa, the tackiness (tackiness )
Is reduced.

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, diethyldi Silicon halide coupling agents such as chlorosilane, monobutyldichlorosilane, dibutyldichlorosilane, monohexyldichlorosilane, dihexyldichlorosilane, dibromosilane, monomethyldibromosilane, dimethyldibromosilane, silicon tetrachloride and tetrabromosilicon;
Alkoxysilanes such as tetramethoxysilane; Divinyl aromatic compounds such as divinylbenzene and divinylnaphthalene; Dichloroethane, dibromoethane, methylene chloride, dibromomethane, dichloropropane, dibromopropane, chloroform, trichloroethane, trichloropropane, halogens such as tribromopropane Alkanes; halogenated aromatic compounds such as dibromobenzene; benzoic acid esters, CO, 2-chloropropene, 1
-Other coupling agents such as chloro-1,3-butadiene; Among these, dibromobenzene and tetramethoxysilane are preferable.

(Method for producing block copolymer) The block copolymers [1], [2] and [3] used in the present invention.
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 the block copolymers represented by the general formulas [2] and [3], after sequentially polymerizing the respective polymer blocks of SBI or SIB, the active terminals are utilized. Can be obtained by carrying out a coupling reaction with a coupling agent.

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

The block copolymer represented by the general formula [1] is prepared by first polymerizing an aromatic vinyl compound in (1) a hydrocarbon solvent using an organic lithium compound as a polymerization initiator,
Then, it can be obtained by successively performing (2) polymerization of butadiene, (3) polymerization of isoprene, and (4) polymerization of aromatic vinyl compound. The order of isoprene polymerization and butadiene polymerization may be reversed.

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,
Then, (2) polymerization of butadiene and (3) polymerization of isoprene are sequentially carried out, and thereafter, a coupling agent is added, and a coupling reaction is carried out using an active terminal.

The block copolymer represented by the general formula [3] is obtained by (1) first polymerizing an aromatic vinyl compound in a hydrocarbon solvent using an organic lithium compound as a polymerization initiator,
Then, the polymerization of (2) isoprene and the polymerization of (3) butadiene may be sequentially carried out, and thereafter, a coupling agent may be added to carry out a coupling reaction utilizing an active terminal. In the coupling reaction, n is preferably 2 or 3.

(Adhesive Composition) The block copolymers [1], [2] and [3] can be used as a base polymer of an adhesive, and in particular, the properties and thermal stability as a thermoplastic elastomer are obtained. Can be suitably used as a base polymer of the hot-melt adhesive composition. The pressure-sensitive adhesive composition of the present invention comprises 100 parts by weight of at least one block copolymer selected from the group consisting of the block copolymers [1], [2] and [3], and a tackifier 20 to 20. It contains 200 parts by weight. Moreover, you may mix | blend a softener in the ratio of 0-100 weight part.

The tackifier used in the present invention has a number average molecular weight of 300 to 3,000 and JIS K-220.
The softening point based on the ring and ball method specified in 7 is 60 to 130 ° C.
The low molecular weight resin 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-based petroleum resins, dicyclopentadiene-based 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 dialkyl salts 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 of the present invention, the proportion of the tackifier used is 20 to 200 parts by weight, preferably 30 to 180 parts by weight, based on 100 parts by weight of the block copolymer. If the proportion of the tackifier is less than 20 parts by weight, the tackiness is lowered, and conversely, if it exceeds 200 parts by weight, the holding power is lowered. The usage ratio of the softening agent is 0 to 10
The amount is 0 parts by weight, preferably 5 to 150 parts by weight, and more preferably 10 to 130 parts by weight. If you deviate from this ratio,
It is difficult to obtain well-balanced physical properties as an adhesive. The pressure-sensitive adhesive composition of the present invention may be blended with other rubber components within a range not hindering the object of the present invention, and further, if desired, an additive such as an antioxidant, a pigment or a filler. It can be blended appropriately.

The method for producing the pressure-sensitive adhesive composition of the present invention is not particularly limited, and a mechanical mixing method using a roll, a Banbury mixer, a Dalton kneader, etc., a melting pot equipped with a stirrer or a uniaxial or twin screw Hot-melt method characterized by heating and mixing using a shaft extruder, solvent method in which the blended components are added to a suitable solvent and the mixture is stirred to obtain a uniform solution of the pressure-sensitive adhesive composition, etc. The method of can also be used. The pressure-sensitive adhesive composition of the present invention can be used without solvent, or by applying a solution thereof uniformly to a support such as paper or plastic film using a suitable coating machine, and drying if necessary to obtain various types of materials. An adhesive tape or an adhesive sheet can be manufactured.

Each block copolymer used in the present invention is
Since it has excellent thermal stability and little change in melt viscosity with time during heating and melting, a pressure-sensitive adhesive composition containing these as a base polymer can be particularly preferably used as a hot-melt 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. Further, the pressure-sensitive adhesive composition of the present invention can 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.

[0030]

EXAMPLES The present invention will be described in more detail below 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> It was measured by the NMR (nuclear magnetic resonance absorption) method. <Amount of vinyl bond> The microstructures of the butadiene portion and the isoprene portion were determined by the NMR method.

<Weight Average Molecular Weight> The weight average molecular weight of the block copolymer is determined by high performance liquid chromatography (HCL).
-802A, manufactured by Tosoh Corporation) was used to calculate based on a calibration curve obtained from the analysis results of standard polystyrene with a known molecular weight. For the measurement, columns G-4000H and G- packed with polystyrene gel were used.
5000 in combination, column temperature 40 ° C., carrier (tetrahydrofuran) flow rate 1.3 ml / min,
The measurement was performed under the condition that the sample concentration was 0.6 g / l.

<Melt Viscosity> The change with time of the melt viscosity is 5 with respect to the initial melt viscosity (0 minutes) of the block copolymer measured by a flow tester at 240 ° C.
It was expressed as the ratio of the melt viscosity after minutes, 10 minutes and 15 minutes.
The closer this value is to 1.0, the smaller the change in melt viscosity over time and the better the thermal stability.

<Measurement of Viscoelasticity> G '(storage elastic modulus),
The measurement conditions of G ″ (loss elastic modulus) and tan δ (loss tangent) are as follows: Device: Rheometrics Dynamic Analyzer II (RDA II) (manufactured by Rheometrics) Test method: Toussion Rectangular -Test test piece: length 42 mm x width 12.5 mm x thickness 2 mm
Strip test piece Frequency: 6.28 rad / sec Measurement temperature range: -100 ° C to 120 ° C

<Adhesive physical properties> An adhesive solution having a non-volatile content of 50% was prepared, and this solution was applied on a polyester film having a thickness of 25 μm so that the adhesive thickness would be 25 μm to prepare an adhesive tape. The tape tackiness, adhesion and holding power were measured. (1) Tackiness is 2 according to JIS Z-0237.
At 3 ° C, a 10 cm long adhesive tape was attached to the slope on 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 32/32 inch from the position 10 cm above the slope. The steel balls of 30 different sizes were rolled at the initial speed of 0 and displayed as the size of the ball with the maximum diameter that stopped on the adhesive tape (average value of 5 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) The holding power is based on JIS Z-0237, and a pressure-sensitive adhesive tape was attached to a stainless steel plate treated in the same manner as described above so that an area of 25 mm × 10 mm was in contact, and a load of 1 kg was applied at 23 ° C. to obtain the pressure-sensitive adhesive tape. The time required for falling off the stainless steel plate was measured (unit: min).

Examples 1 to 5 Synthesis of Block Copolymer In a dry nitrogen atmosphere, in a 3 liter autoclave,
In 1500 g of cyclohexane solvent, using 5.7 mmol of n-butyllithium as a polymerization initiator,
Styrene (ST), butadiene (BD), isoprene (IP), and styrene (ST) were sequentially added in 5 hours to carry out polymerization, and 5 kinds of S-B-I-S type block copolymers shown in Table 1 were added. A coalesce was manufactured. The total weight of ST, BD and IP used was 400 g. Tables 1 and 2 show the measurement results of the weight average molecular weight, the vinyl bond amount of the conjugated diene portion, and the viscoelasticity of each of the obtained block copolymers.

The result of viscoelasticity measurement of the block copolymer (S-B-I-S = 15: 45: 25: 15) synthesized in Example 3 is shown in FIG. As is clear from FIG. 1, in the block copolymer used in the present invention (Example 3), the peak of loss tangent (tan δ) due to the butadiene polymer block and the isoprene polymer block was 1 at −71 ° C. There is only one.

Preparation of pressure-sensitive adhesive composition A pressure-sensitive adhesive composition was prepared according to the following formulation (the same applies in the following examples), and the pressure-sensitive 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%), and this solution was applied onto a 25 μm thick polyester film. To a thickness of 25 μm to prepare an adhesive tape. The results are collectively shown in Table 2. [Composition of adhesive composition] Block copolymer 100 parts Tackifier (hydrogenated aromatic petroleum resin) 170 parts Softener (paraffinic process oil) 65 parts Antioxidant 0.3 parts

Examples 6 to 7 n-butyllithium was used as a polymerization initiator in a cyclohexane solvent, and styrene (ST), butadiene (BD), and isoprene (IP) were sequentially added to carry out polymerization. Then, a coupling reaction was carried out using dibromobenzene as a coupling agent to produce (S-B-I) _n- X type block copolymers shown in Table 1. Tables 1 and 2 show the measurement results of the weight average molecular weight, the vinyl bond amount of the conjugated diene portion, and the viscoelasticity of each of the obtained block copolymers. Table 2 shows the measurement results of the adhesive physical properties of the adhesive composition prepared using these block copolymers.

[Comparative Examples 1 and 2] In the same manner as in Examples 1 to 5, those having a butadiene polymer block or isoprene polymer block ratio outside the range of the block copolymer used in the present invention were prepared. The results of measuring the physical properties of these block copolymers are shown in Tables 1 and 2. Table 2 shows the measurement results of the adhesive physical properties of the adhesive composition prepared using these block copolymers.

[Comparative Examples 3 to 4] In the same manner as in Examples 1 to 5, S-IS type and S-B-S type block copolymers were prepared. The results of measuring the physical properties of these block copolymers are shown in Tables 1 and 2. Table 2 shows the measurement results of the adhesive physical properties of the adhesive composition prepared using these block copolymers.

[Comparative Examples 5 to 6] The S-IS type and S-B-S type block copolymers prepared in Comparative Examples 3 to 4 were blended at different compounding ratios. Moreover, the viscoelasticity measurement result of the blend (SBS / SIS = 5/2) prepared in Comparative Example 5 is shown in FIG. As is clear from FIG. 2, in this blend, two peaks of loss tangent (tan δ) due to the butadiene polymer block and the isopylene polymer block were observed at −74 ° C. and −53 ° C. Tables 1 and 2 show the results of measuring the physical properties of the blends of these block copolymers. Table 2 shows the measurement results of the adhesive physical properties of the adhesive composition prepared using the blend of these block copolymers.

[0043]

[Table 1]

[0044]

[Table 2] (Footnote) (* 1) The block composition of these polymers is that before coupling. (* 2) There are two peak temperatures of tan δ in these blends.

As is clear from the results of Tables 1 and 2, the block copolymers (Examples 1 to 7) used in the present invention have a small change in melt viscosity with time and are excellent in thermal stability. I understand. In addition, the adhesive tape using such a block copolymer as a base polymer has high levels of physical properties in terms of tack, adhesive strength and holding power. Incidentally, in measuring the adhesive physical properties, the adhesive tape was prepared by the solution coating method, but of course, the adhesive composition of the present invention was used to directly apply the adhesive tape to the substrate by the melt processing method to prepare the adhesive tape. can do.

On the other hand, the block copolymers (Comparative Examples 1 and 2) and the SIS type or SBS type block copolymers (Comparative Examples 3 and 4) in which the proportion of bound butadiene and the proportion of bound isoprene are outside the ranges specified in the present invention. ), And blends of SIS type and SBS type block copolymers (Comparative Examples 5-6),
All of them had large changes in melt viscosity over time, and had poor thermal stability. Moreover, the pressure-sensitive adhesive composition containing the block copolymer or the blended product as a base polymer in these comparative examples is inferior in the balance of tack, adhesion and holding power.

[0047]

INDUSTRIAL APPLICABILITY According to the present invention, a novel block copolymer, which has characteristics as a thermoplastic elastomer, has little change in melt viscosity during heat-melt processing, and has excellent thermal stability, is used as a base polymer. There is provided a pressure-sensitive adhesive composition, in particular, a hot-melt pressure-sensitive adhesive composition having excellent coating workability, fluidity, adhesive properties and the like.

[Brief description of drawings]

FIG. 1 is a chart showing the viscoelasticity measurement results of the block copolymer synthesized in Example 3.

2 is a blend prepared in Comparative Example 5 (SBS / SI
It is a chart which shows the viscoelasticity measurement result of S = 5/2).

Claims (2)

[Claims] 1. (a) A block copolymer having a structure represented by the following general formula [1], [2] or [3], wherein (S-B-I-S) [1] (S -BI) _n -X [2] (SIB) _n -X [3] (In the formula, S is a polymer block of an aromatic vinyl compound. B is a butadiene polymer block. Yes, I
It is an isoprene polymer block. n is an integer of 2-4. X is the residue of the coupling agent. ) (B) Weight average molecular weight of 10,000 to 500,000
0, (c) the proportion of bound aromatic vinyl compound is 10 to 50% by weight, (d) the proportion of bound butadiene is 10 to 60% by weight, (e) the proportion of bound isoprene is 10 to 60% by weight, (f) The ratio of 1,2-vinyl bonds in the butadiene portion is 1
5% or less, (g) the ratio of 3,4-vinyl bonds in the isoprene portion is 1
0% or less, (h) Storage elastic modulus (G ′) in viscoelasticity measurement is 0 ° C.
In the range of up to 50 ° C., 10 ^{6 to} 3 × 10 ⁸ Pa, (i) the peak of loss tangent (tan δ) due to the butadiene polymer block and the isoprene polymer block,
At least one block copolymer 10 selected from the group consisting of only one block copolymer [1], [2] and [3] in the range of -80 ° C to -50 ° C.
A pressure-sensitive adhesive composition containing 0 parts by weight and 20 to 200 parts by weight of a tackifier. 2. The pressure-sensitive adhesive composition according to claim 1, which is a heat-melting type.