JP3339172B2 - Method for producing block copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a novel block copolymer, and more particularly to a method for producing a base polymer of a hot-melt type pressure-sensitive adhesive composition, which has a small change in melt viscosity with time. The present invention relates to a method for producing a block copolymer.

[0002]

2. Description of the Related Art Conventionally, styrene-isoprene-styrene (SIS) block copolymers and styrene-butadiene-based copolymers have been used as base polymers for pressure-sensitive adhesives (adhesives) and hot-melt adhesives (hot-melt adhesives). Styrene (SB
S) A pressure-sensitive adhesive composition using a thermoplastic elastomer such as a block copolymer and using both a SIS block copolymer and an SBS block copolymer as a base polymer is also known (Japanese Patent Publication No. 53-42345
issue). However, conventionally known block copolymer-based thermoplastic elastomers have poor thermal stability.
In the case of an IS type block copolymer, the viscosity of the melt is rapidly reduced due to thermal degradation during melt processing. On the other hand, in the case of an SBS type block copolymer, the melt is cross-linked during melt processing to form a melt. Viscosity rises sharply. In addition, even in the case of a blend of these two, the melt viscosity during heating shows a sharp 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.

[0003] In order to satisfy such required performance, the applicant has previously disclosed an SIBS type block copolymer which has an isoprene polymer block and a butadiene polymer block, has little change in melt viscosity with time, and has excellent heat stability. Filed an application (Japanese Patent Application No. 4-262807). In the method for producing the block copolymer, an aromatic vinyl compound, isoprene, butadiene and an aromatic vinyl compound are sequentially added to carry out polymerization. However, the pressure-sensitive adhesive composition comprising the block copolymer obtained by this method as a base polymer generally still has insufficient holding power of the pressure-sensitive adhesive properties, and improvement thereof is desired.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel (S-I) which has properties as a thermoplastic elastomer, has little change in melt viscosity with time during heat melting processing, and has excellent heat stability. It is an object of the present invention to provide a method for efficiently producing a (-BS) type block copolymer. The present inventors have conducted intensive studies to overcome the problems of the prior art, and as a result, when producing a (S-I-BS-) type block copolymer, the residual concentration of unreacted butadiene and By controlling the time of addition of polystyrene to be polymerized last,
It has been found that the pressure-sensitive adhesive composition using the obtained block copolymer has a difference in pressure-sensitive adhesive properties, and has been completed based on this finding.

[0005]

Thus, according to the present invention, an aromatic vinyl compound is polymerized using an organolithium initiator, isoprene is polymerized, then butadiene is polymerized, and unreacted butadiene is further polymerized. Has a residual concentration of 50
After reaching 0 ppm or less, an aromatic vinyl compound is added for polymerization.
A method for producing the block copolymer represented by S) is provided. (In the formula, S is a polymer block of an aromatic vinyl compound. I is an isoprene polymer block. B is a butadiene polymer block.)

[0006] The block copolymer produced in the present invention has a structure represented by the general formula (SIBS). In the formula, S is a polymer block of an aromatic vinyl compound, I is an isoprene polymer block, and B is a butadiene polymer block.

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.

In the block copolymer produced in the present invention, the ratio of the bound aromatic vinyl compound is 10 to 5 in total.
0% by weight, the proportion of bound butadiene is 10 to 60% by weight, and the proportion of bound isoprene is 10 to 60% by weight. The weight ratio of bound butadiene to bound isoprene is usually 15/85 to 85/15, preferably 20/85.
/ 80 to 80/20.

When the proportion of the bound aromatic vinyl compound is less than 10% by weight, when the block copolymer is used as the base polymer of the pressure-sensitive adhesive, the holding power is reduced. Tackiness (adhesion) decreases. When the content of bound butadiene is less than 10% by weight, the melt viscosity of the block copolymer decreases with time, and the holding power decreases. On the other hand, when the content exceeds 60% by weight, the melt viscosity increases with time. Is not preferred. If the proportion of bound isoprene is less than 10% by weight, the melt viscosity of the block copolymer will increase with the passage of time. Conversely, if it exceeds 60% by weight, the melt viscosity will decrease with the passage of time. By the ratio of bound styrene, bound isoprene and bound butadiene being within the above range,
When the obtained block copolymer is used as a base polymer of the pressure-sensitive adhesive, a pressure-sensitive adhesive having good tackiness, adhesive strength and holding power, and excellent in low-temperature properties can be obtained. Further, when the ratio of the bound isoprene and the bound butadiene is within the above range, a block copolymer having excellent heat resistance and a small change in melt viscosity during melt processing can be obtained.

The block copolymer produced in the present invention has a weight average molecular weight (in terms of polystyrene) of 1 as measured by gel permeation chromatography (GPC).
0000 to 500,000, preferably 50,000
３００300,000. Weight average molecular weight is 1
If it is less than 000, the holding power is reduced, while
If it exceeds 000, tackiness will decrease and
Coatability and workability deteriorate.

The block copolymer produced in the present invention usually has a butadiene moiety having a 1,2-vinyl bond ratio of 15 or less.
% Or less, and the proportion of 3,4-vinyl bonds in the isoprene moiety is 10% or less. Further, the block copolymer produced in the present invention has a storage elastic modulus (G ′) in viscoelasticity measurement.
Is 10 ^{5 to} 3 × 10 ⁸ in the range of 0 ° C. to 50 ° C.
There is only one peak at Pa and a loss tangent (tan δ) due to the butadiene polymer block and the isoprene polymer block in the range of −80 ° C. to −50 ° C. For example, when the SIS type block copolymer and the SBS type block copolymer are blended, the loss tangent (tan δ) of each of the butadiene polymer block and the isoprene polymer block is calculated. Two peaks appear in the range of -80C to -50C. 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. Conversely, when the block copolymer exceeds 3 × 10 ⁸ Pa, the low-temperature tackiness (adhesion) is reduced. Sex) is reduced.

The method for producing a (S-I-B-S) type block copolymer according to the present invention uses a conventionally known organolithium compound as a polymerization initiator and comprises the steps of:
First, an aromatic vinyl compound is polymerized, then isoprene is polymerized, and then butadiene is polymerized. The residual concentration of unreacted butadiene is 500 ppm or less, preferably 100 ppm.
After the amount becomes less than ppm, an aromatic vinyl compound is added, and finally, the aromatic vinyl compound is polymerized. At this time, the residual concentration of unreacted butadiene was 500 p
pm or less, the addition of the aromatic vinyl compound
An aromatic vinyl compound polymer block containing a large amount of a part where butadiene and an aromatic vinyl compound are randomly copolymerized is generated, and therefore, a pressure-sensitive adhesive composition containing such a block copolymer as a base polymer In this case, the holding power of the adhesive properties is extremely reduced.

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. .

The organic lithium compound used as the polymerization initiator includes, for example, n-butyllithium, sec.
-Butyllithium, tert-butyllithium, n-hexyllithium, iso-hexyllithium, phenyllithium, naphthyllithium and the like, and are usually used in the range of 0.01 to 1 part by weight per 100 parts by weight of the monomer.

The block copolymer produced in the present invention can be used as a base polymer of a pressure-sensitive adhesive. In particular, it utilizes the properties and heat stability of a thermoplastic elastomer to obtain a hot-melt pressure-sensitive adhesive. It can be suitably used as a base polymer of the composition. Such a pressure-sensitive adhesive composition contains 100 parts by weight of the block copolymer and 50 to 300 parts by weight of a tackifier. Also, if the softener is 0 to
You may mix | blend in the ratio of 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.

Among the tackifiers, those which are particularly compatible with the butadiene polymer block or the isoprene polymer block of the block copolymer are preferable, and examples thereof include polyterpene resins, aliphatic petroleum resins, and aromatic petroleum resins. Hydrides 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 30 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. In the pressure-sensitive adhesive composition, other rubber components may be blended as long as the object of the present invention is not hindered, and further, if desired, an antioxidant,
Additives such as pigments and fillers can be appropriately compounded.

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 tarton kneader, or the like, a melting pot equipped with a stirrer, or a single-shaft or twin-shaft. 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.

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

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 utilizing its features, 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.

[0023]

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 isoprene, and bound butadiene> Measured by NMR (nuclear magnetic resonance absorption) method (unit:% by weight). <Residual butadiene concentration> Measured by gas chromatography (unit: ppm) <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 ). <Measurement of Viscoelasticity> The measurement conditions for G ′ (storage modulus), 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: 42 mm long x 12.5 mm wide x 2 m thick
m strip test piece Frequency: 6.28 rad / sec Measurement temperature range: -100 ° C to 120 ° C

<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 to a paste thickness of 25 μm to prepare an adhesive tape. The tackiness, adhesion and holding power of the tape were measured. (1) Tackiness shall be 2 in accordance with JIS Z-0237.
At 3 ° C. and 5 ° C., an adhesive tape having a length of 10 cm is stuck on a slope on a stainless steel plate having an inclination angle of 30 degrees with the adhesive face up, and a diameter of 3 / cm is measured from a position 10 cm above the slope.
30 types of steel balls from 32 inches to 32/32 inches were rolled at an initial speed of 0 and displayed as the size of the ball with the largest diameter stopping on the adhesive tape (average value of 5 ball numbers) ). (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 and 2) Under 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, and styrene (ST ), Isoprene (IP) and butadiene (BD) are sequentially added and polymerized, and when the residual concentration of unreacted butadiene is 400 ppm and 20 ppm, styrene is added and polymerized, respectively, whereby two types of (S- An IBS) type block copolymer was produced. The composition of the block copolymer is as follows: ST: IP: BD: ST = 20: 35: 25:
20. The total weight of ST, IP and BD used was 400 g. The weight average molecular weight of each of the block copolymers is 80,000. From the viscoelasticity measurement results of the obtained four types of block copolymers, the peaks of the loss tangent (tan δ) due to the butadiene polymer block and the isoprene polymer block were all -62.
There was only one at ° C. Next, a pressure-sensitive adhesive composition was prepared using the above four types of block copolymers according to the following formulation (the same applies to the following examples), and pressure-sensitive adhesive properties were measured. Specifically, each component is kneaded with a Dalton kneader according to the following formulation, and the resulting composition is dissolved in toluene (concentration of nonvolatile components: 50%).
An adhesive tape was prepared by applying the adhesive on a thick polyester film so as to have a paste thickness of 25 μm. Table 1 summarizes the results
Shown in [Blending of adhesive composition] Block copolymer 100 parts Tackifier (hydrogenated aromatic petroleum resin) 170 parts Softener (paraffinic process oil) 65 parts Antioxidant 1 part

(Comparative Examples 1 and 2) As in Example 1, 15 liters of autoclave were placed in a dry nitrogen atmosphere.
Styrene (ST), isoprene (IP), butadiene (B) were used at 60 ° C. in OO mmol of cyclohexane solvent using 5.7 mmol of n-butyllithium as a polymerization initiator.
D) were added sequentially to polymerize, and when the residual concentration of unreacted butadiene was 1200 ppm and 560 ppm, styrene was added and polymerized, respectively. -IBS) type block copolymer was produced. The composition of the block copolymer is ST: IP: BD: S
T = 20: 35: 25: 20. The used S
The total weight of T, BD and IP was 400 g. The weight average molecular weight of each of the block copolymers is 80,000. Also, from the viscoelasticity measurement results of the obtained four types of block copolymers, only one peak of loss tangent (tan δ) due to the butadiene polymer block and the isoprene polymer block exists at -62 ° C. did. Next, Example 1 was carried out using the above four types of block copolymers.
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 2 and pressure-sensitive adhesive properties were measured.
Table 1 shows the results.

[0027]

[Table 1]

From the results shown in Table 1, it was found that, by the production method of the present invention, styrene was added and polymerized after the residual concentration of unreacted butadiene became 500 ppm or less (S-
It can be seen that the pressure-sensitive adhesive tape using the (IBS) type block copolymer as a base polymer has a high level of physical properties in both tackiness, adhesive strength and holding power. On the other hand, when the block copolymer obtained by adding and polymerizing styrene before the residual concentration of unreacted butadiene becomes 500 ppm or less is used, it is understood that the holding power is extremely low.

The specific embodiments of the present invention are as follows. (1) An aromatic vinyl compound is polymerized using an organolithium-based initiator, isoprene is polymerized, butadiene is polymerized, and after the residual concentration of unreacted butadiene becomes 500 ppm or less, the aromatic compound is polymerized. General formula (S-I-B) characterized in that polymerization is carried out by adding a vinyl compound.
A method for producing a block copolymer represented by -S). (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.) (2) General formula (S-IB) -S) The method for producing a block copolymer according to (1), wherein the bound aromatic vinyl compound of the block copolymer is styrene. (3) The ratio of the bonded aromatic vinyl compound of the block copolymer represented by the general formula (SIBS) is 10 to 50.
% By weight, the proportion of bound butadiene is 10 to 60% by weight, the proportion of bound isoprene is 10 to 60% by weight, and the storage elastic modulus (G ') in viscoelasticity measurement is 10 ⁵ Pa in the range of 0 ° C to 50 ° C. is ~3 × 10 ⁸ Pa, a manufacturing method of the block copolymer (1). (4) The block copolymer represented by the general formula (S-I-B-S) has a bond aromatic bi & weight average molecular weight of 10,000.
The method for producing a block copolymer according to (1), wherein the amount is from 0 to 500,000.

[0030]

According to the present invention, a novel block copolymer having properties as a thermoplastic elastomer, having little change in melt viscosity with time during heat melting processing, and having excellent heat stability can be efficiently obtained. Is provided. Further, according to the present invention, the pressure-sensitive adhesive composition, particularly,
A novel block copolymer suitable as a base polymer for a hot-melt pressure-sensitive adhesive composition is provided. Furthermore, the pressure-sensitive adhesive composition comprising the novel block copolymer produced as a base polymer in the present invention is particularly useful as a hot-melt pressure-sensitive adhesive composition having excellent coating workability, fluidity, and low-temperature properties. is there.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-107745 (JP, A) JP-A-6-234821 (JP, A) JP-A-5-70699 (JP, A) JP-A-3-107 287652 (JP, A) Special Table Hei 6-509595 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 297/04 C09J 153/02

Claims (1)

(57) [Claims] 1. An aromatic lithium compound is polymerized using an organolithium initiator, isoprene is polymerized, and
Butadiene is polymerized, and after the residual concentration of unreacted butadiene has become 500 ppm or less, an aromatic vinyl compound is added to carry out polymerization.
A method for producing the block copolymer represented by IBS).
(In the formula, S is a polymer block of an aromatic vinyl compound. I is an isoprene polymer block. B is a butadiene polymer block.)