JPS61261310A - Linear block copolymer, its production and self-adhesive composition - Google Patents

Abstract

PURPOSE:To obtain a linear block copolymer excellent in balance among initial tack, adhesive force and holding power and suitable as a self-adhesive, by coupling an aromatic vinyl polymer block with a conjugated diene polymer block with a coupling agent. CONSTITUTION:A polymer block A is formed by polymerizing 5-40pts.wt. aromatic vinyl compound (e.g., styrene) with the aid of a monolithium initiator in the presence of a polar compound of a specific dielectric constant of 2.5-5, such as an aromatic or aliphatic ether or a tert. monoamine, in a solvent mixture comprising 5-50wt% 4-5C acyclic hydrocarbon solvent and 95-50wt% cyclic hydrocarbon solvent. 95-60pts.wt. conjugated diene monomer is added to the reaction system to form a polymer block B of this conjugated monomer at one terminal of block A. An ester of a monobasic aliphatic carboxylic acid as a coupling agent is added to couple the polymer block A with the polymer block B.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a linear A-B consisting of a polymer block (A) of an aromatic vinyl compound and a polymer block (B) of a conjugated diene monomer. The present invention relates to a -XB-A block copolymer (in the formula, X represents a coupling agent residue), a method for producing the same, and an adhesive composition containing this block copolymer.

(Prior Art and Problems to be Solved by the Invention) Linear or branched block copolymers such as polystyrene-polyisoprene-polystyrene have been widely used for adhesives.

The performance required for pressure-sensitive adhesives is a well-balanced initial adhesive strength, adhesion strength, and holding power, and a further challenge is how to improve the holding power among these properties.

One method is to use a bifunctional or higher-functionality coupling agent to make the molecular weight distribution of the polystyrene block wider than that of the whole block copolymer (rubber-like teleblock copolymer (S-11NM)). In the formula, Japanese represents a block of a monovinyl-substituted aromatic hydrocarbon polymer, D represents a block of a conjugated diene polymer, (f) represents an integer of at least 2, and Y represents a residue of a polyfunctional coupling agent.) Although it is described in Japanese Patent Publication No. 55-41686, it cannot be said that a sufficient improvement can be obtained.

(Means for Solving the Problems) The present invention has been made as a result of intensive studies to improve the balance of properties and retention of adhesives using block copolymers using methods other than those described above. If a linear block copolymer in which aromatic vinyl polymer blocks have a specific molecular weight distribution is used using a coupling agent, the above problems can be solved, and the heat resistance of the block copolymer can also be improved. They have found that this can be improved, and have completed the present invention based on this knowledge.

That is, the present invention is based on (1) the general formula A-B-X-B-A (in the formula, the person represents a polymer block of an aromatic vinyl compound, B represents a polymer block of a conjugated diene monomer, and X represents a polymer block of a conjugated diene monomer; represents the residue of an ester of a monohydric aliphatic carboxylic acid and a monohydric alcohol as a coupling agent, respectively, and A vs. B in the formula
The weight ratio of 5 to 40:95 to 60, the ratio of the weight average molecular weight ([v) to the number average molecular weight (伽) (Rv
/Mi) is 1.2 or less, the weight average molecular weight of the polymer ($(
linear block copolymers whose W
Using a mixed solvent consisting of 31% by weight and 95 to 50% by weight of a cyclic hydrocarbon solvent, the ratio i! ! The aromatic vinyl compound is activated by polymerizing it using an organolithium initiator in the presence of a polar compound selected from aromatic ethers and aliphatic ethers or tertiary amines having a ratio of 2.5 to 5.0. A conjugated diene monomer is then added to form a polymer block B of the active monomer at the end of the polymer block A, and then a monovalent monovalent monomer is added as a coupling agent. The linear A-B-A type block according to item (1), characterized in that an ester of an aliphatic carboxylic acid and a monohydric alcohol is added to bond the active A-B block polymer. A method for producing a copolymer, and (3) using an ester of a monohydric aliphatic carboxylic acid and a monohydric alcohol as a coupling agent, producing a polymer block A of an aromatic vinyl compound versus a conjugated diene-based Si form. The polymer block BONii ratio is 5-40:95-60, and the ratio of weight average molecular weight (VW) to number average molecular weight (UN) (j2v/My) measured by gel permeation chromatography of block A is 1.2 or less, weight average molecular weight iW) of the weight body is 50,000 to 500,
000, having the general formula A-B-X-B-A (wherein or the above-mentioned adhesive composition is provided).

The novel linear block copolymer of the present invention has the general formula AB-
X-B-A (in the formula, the person represents a polymer block of an aromatic vinyl compound, B represents a polymer block of a conjugated diene monomer,
or a residue of an ester of a monohydric aliphatic carboxylic acid and a monohydric alcohol as a coupling agent), and the above-mentioned specific two as a coupling agent. It was measured by gel permeation chromatography of polymer block A of aromatic vinyl compound and the use of a functional compound! ;! W
/ Nυ ratio is 1.2 or less.

The Uv/IZM of polymer block A affects the holding power of the adhesive, and when the ratio exceeds 1.2, the holding power decreases.

Preferably it is 1.1 or less.

The in average molecular weight (VW) of the block copolymer of the present invention ranges from so, ooo to soo, ooo;
If it is less than oo, the holding power will not be sufficient, and if it exceeds son, ooo, the preparation operation (processability) of the adhesive will become difficult. Preferably it is 100,000 to 40 G,000.

The linear block copolymer having these characteristics of the present invention is produced by the following method.

The aromatic vinyl compounds used in the present invention are styrene, α
- Typical compounds include methylstyrene, vinyltoluene, and vinylnaphthalene, with styrene being particularly preferred. The conjugated diene monomers used in the present invention are 1,5-butadiene, isoprene, 2,3-dimethyl-
Representative examples include 1,3-butadiene, piperylene, and 2,4-hexashev, with butadiene and isoprene being particularly preferred.

The ratio of the aromatic vinyl compound to the conjugated diene monomer is 5 to 40:95 to 60 in terms of polymerization ratio. If the proportion of the aromatic vinyl compound used is less than the above-mentioned lower limit, the holding power of the pressure-sensitive adhesive containing the block copolymer of the present invention will be reduced, and if it exceeds the above-mentioned upper limit, the initial adhesive strength (tack) will be reduced. Preferably the ratio is 10-35:90-65.

As the monolithium initiator of the present invention, known initiators capable of initiating polymerization of aromatic vinyl compounds and conjugated diene monomers can be used, such as methyllithium, ro-probyl lithium, 8θC- Typical examples include butyllithium, but dibutyllithium is particularly preferred. The amount of monolithium initiator used is usually 50 to 200 mmol per gram of monomer.

In the present invention, 04~! is used as a polymerization solvent! A mixed solvent of an open chain hydrocarbon solvent and a cyclic hydrocarbon solvent is used.

04~. Examples of open-chain hydrocarbon solvents include lubutane, IB-butane, or a mixture thereof: 1-butene, isobutylene, trans-2-butene, cis-2-butene, or a mixture of two or more of these; lupentane, 1s
O-pentane, neo-pentane or a mixture of two or more thereof; selected from C4~, open-chain alkanes, and alkenes such as 1-pentene, trans-2-pentene, cis-2-pentene, or a mixture of two or more thereof; at least one solvent that is inert to the monolithic initiator.

The cyclic hydrocarbon solvent is selected from aromatic compounds such as benzene, toluene, and xylene, and alicyclic solvents such as cyclohexane.

04~. The ratio of open chain hydrocarbon solvent to cyclic hydrocarbon solvent used is in the polymerization ratio of 5:95 to 50:50, preferably 10:90 to 40:60. If it is outside this range, the polymerization temperature will rise, the molecular weight distribution of the aromatic vinyl compound polymer will become wider, and the predetermined Xrv/UM
Not only is it not possible to obtain the polymer having the desired ratio, but the active polymerization volume is deactivated, resulting in impurities in the obtained block copolymer, which is undesirable.

In the present invention, the aromatic vinyl compound polymer UvZMN
Another requirement for bringing the ratio within a certain range is the presence of a polar compound in the polymerization system. The polar compound used in the present invention is a polar compound known as a vinyl content regulator or randomizer in the polymerization of a conjugated diene monomer or an aromatic vinyl compound using a lithium-based initiator, and has a dielectric constant of 2.5. ~5.0 aromatic and aliphatic ethers or tertiary amines are used. When using polar compounds other than these, it is difficult to achieve a desired molecular weight distribution for the aromatic vinyl compound polymer.
Furthermore, the amount of vinyl in the conjugated diene unit in the polymer increases significantly, which is not preferable. Such polar compounds include aliphatic ethers such as diethyl ether and diethyl ether:
Examples include aromatic ethers such as diphenyl ether and anisole; and tertiary monoamines such as trimethylamine, triethylamine and tripropylamine, and one or more of these may be used.

When the molecular weight distribution of the aromatic vinyl compound polymer is set to a predetermined value, the amount of polar compound used is preferably Q per mol of monolithic initiator, from 1 to 100 mol, and Preferably it is in the range of 0.5 to 20 mol.

In the present invention, an aromatic vinyl compound is first polymerized using a monolithic initiator in a mixed solvent containing a polar compound. Polymerization includes batch polymerization in which the entire amount of the core compound and the initiator are charged into a polymerization system and reacted, continuous polymerization in which the core compound and the initiator are reacted while being continuously supplied to the polymerization system, and a part of the core compound and the initiator are used in the polymerization. A method may be used in which the polymerization is carried out to a predetermined conversion rate and then the remainder is added to continue the polymerization, but the polymerization mode is not particularly limited in the present invention.

Polymerization is usually carried out in the range of OC to 90C1, preferably 20C to 70C. If it is difficult to control the reaction temperature, use the reflux type! It is preferable to control the temperature by reflux cooling using a reaction vessel equipped with a condenser.

Next, a conjugated diene monomer is added to the polymerization system in which the active aromatic vinyl compound polymer (4) is present, and polymerization is carried out. Although it is preferable to add the monomer continuously to the polymerization system in order to control the reaction heat, the method of adding the monomer is not limited to this method in the present invention. In this way, an active AB block copolymer in which the polymer (B) of the conjugated diene monomer is directly bonded to the above-mentioned A is produced. After the polymerization reaction is completed, a coupling agent is added to the polymerization system to bond the active block copolymer and form the desired linear A-B-X-B.
-A block copolymer (in the formula, X represents a residue of a coupling agent) is obtained.

The coupling agent used in the present invention is an ester of a monovalent aliphatic carboxylic acid and a monohydric alcohol, and the use of this coupling agent imparts heat resistance to the block copolymer of the present invention.

Such coupling agents include aliphatic monocarboxylic acids such as acetic acid, formic acid, propionic acid, butyric acid, valeric acid, trimethylacetic acid, and caproic acid, and methyl alcohol, orthophthyl alcohol, orthoclobyl alcohol, isopropyl alcohol, or amyl alcohol. Examples include esters with aliphatic monohydric alcohols such as alcohols or aromatic monohydric alcohols such as phenol, cresol, and naphthol.

The amount of coupling agent used is usually 0.2 to 3 times the amount of monolithic initiator used. Outside this range, the coupling rate decreases. Preferably it is 0.5 to 3 times. Although the temperature of the coupling reaction can be varied over a wide range, it is usually carried out at the polymerization temperature. Since the reaction proceeds rapidly, the reaction time usually ranges from a few seconds to an hour.

After the coupling reaction is completed, water, alcohol,
After adding an acid or the like to deactivate the active species and adding an anti-aging agent, the block copolymer is separated by a known polymer separation method such as steam stripping.

The desired block copolymer is obtained through a drying process.

The adhesive composition of the present invention mainly consists of the block copolymer of the present invention and a tackifying resin (plating fire).

The tackifier used in the present invention includes conventionally known tackifiers used in adhesives using conventional block copolymers similar to the block copolymer of the present invention.
can be used. Specifically, rosin: modified rosins such as disproportionated rosin and dimerized rosin; glycol, glycerin,
Esterified product of pentaerythritol etc. and rosin or modified rosin; Terpene resin: aliphatic, aromatic, alicyclic or aliphatic-aromatic copolymerized hydrocarbon resin or hydride thereof; phenol Resin; Examples include coumaron-indene resin. Particularly preferred plating fires are aliphatic hydrocarbon resins and aliphatic-aromatic copolymer hydrocarbon resins that are highly compatible with the block copolymer of the present invention.

The amount of tackifier used is usually block copolymer 10
The amount is 10 to 150 parts by weight per 0 parts by weight.

The adhesive composition of the present invention may contain a softener (plasticizer) if necessary.
, other compounding agents such as antioxidants can be added.

As the softening agent, conventionally known aromatic, paraffinic or naphthenic extender oils used in adhesives, liquid polymers such as polybutene, polyisobutylene, etc. can be used.

The amount used is usually 100 parts per 100 parts by weight of the block copolymer.
Parts by weight or less. 2.6-Gt as an antioxidant
-Hindered phenol compounds such as butyl-p-cresol and di-7-butyl-4-methyl-phenol;
Thiodicarboxylate esters such as dilaurylthiopropionate, phosphites such as tris(nonylphenyl)phosphite, and the like are used alone or in combination.

The adhesive composition of the present invention can be used as a solution type adhesive by dissolving it in roohexane, cyclohexane, benzene, toluene, etc., as an emulsion type adhesive by dispersing it in water using an emulsifier, or as a solvent-free hot adhesive. It can be used as a melt-type adhesive. Particularly suitable are hot melt adhesives.

The present invention will be explained in more detail with reference to Examples below. In addition, the parts and ratios in Examples and Comparative Examples are based on weight unless otherwise specified.

Example 1 50I! Using a pressure-resistant reactor, in the presence of 18.75 mmol of a mixed solvent of 30/70 lupusane/cyclohexane, 200 mmol of dibutyl ether, and 100 mmol of rubyl lithium as an initiator, 1.1251 mmol of styrene was heated at 30 C for 1 hour. was polymerized, followed by isoprene &87
511 was added, and polymerization was carried out for about 1.5 hours while controlling the reaction temperature by reflux cooling so that the reaction temperature was between 500 and 60C. Subsequently, 50 mmol of ethyl acetate was added to carry out a coupling reaction. 50 g of methanol was added to the reaction mixture as a polymerization terminator, and 4-methyl-2,
After adding 409 g of 6-di-t-butylphenol, this mixed solution was dropped little by little into water heated to 85 to 95 C to volatilize the solvent. Grind the obtained polymer,
It was dried with hot air at 85C (polymer ■). In the above production example, as polar compounds/coupling agents, triethylamine/butyl acetate (polymer ■); diptyl ether/isopropyl acetate (polymer ■); triethylamine/butyl butyrate (polymer ■); dibutyl ether/phenyl acetate (polymer ■); A block copolymer was produced in the same manner except that polymer ①) was used. Also, except for using a ratio of styrene to isoprene of 20280, polymer ■
Polymer (■) was obtained in the same manner as above. Next, a block copolymer was produced in the same manner as in the production of Polymer 1 except that cyclohexane was used alone as the polymerization solvent (Polymer (2)).
.

Also, as a bath agent, Looptan/Cyclohexane = 50750
(Polymer ■) except that diglyme/butyl acetate (Polymer (p)); triethylamine/phenyl benzoate (Polymer @) were used as polar compounds/coupling agents, respectively. A block copolymer was obtained in the same manner as Polymer ①. Also, as a solvent, butane/cyclohexane (so/s
Polymer (2) was obtained in the same manner as Polymer (2) except that o) was used. Table 1 shows the properties of each block copolymer thus obtained.

The weight average molecular weight (u'') and number average molecular weight ←-) were determined in terms of polystyrene by gel permeation chromatography (using Toyo Soda Kogyo Co., Ltd. I (LC-802A), solvent tetrahydrofuran, measurement temperature 4 oro) according to a conventional method. It was determined as the molecular weight.Also, the 3.4-
The amount of binding was determined by infrared spectroscopy.

Example 2 A-B-A type block copolymer 10 obtained in Example 1
0 parts, 100 parts of tackifier resin, 30 parts of naphthenic process oil (Shell Flex 371, manufactured by Shell Chemical Co., Ltd.), and 1 part of antioxidant were dissolved and mixed in toluene to prepare an adhesive solution with a nonvolatile content concentration of 40%. . Next, add this solution to 2
An adhesive tape was prepared by applying the paste to a 25 μm thick polyester film on a 5 μm thick polyester film, and its initial adhesive strength, adhesion strength, and holding power were measured.

In addition, the initial adhesive strength is 25C according to Z-0237 from J.
A length of 1 is attached to the slope on a stainless steel plate with an inclination angle of 50 degrees.
Attach a 0α adhesive tape with the adhesive side facing up, and roll steel balls of 30 different sizes from 3732 inches in diameter to 1 inch from a position 101 above the slope at an initial speed of 0 and stop on the adhesive tape. Displayed as the size of the largest diameter sphere,
The adhesive strength is based on JIS Z-0237, and adhesive tape is attached to a stainless steel plate polished with No. 280 water-resistant abrasive paper, with a width of 10 mm and a length of 100 mm, and the adhesive tape is 200 mm wide at 25C.
The adhesive tape was measured by peeling it in a direction of 180 degrees at a speed of 1/min, and the holding force was determined according to J Engineering 5Z-025'7. A load of 1- was applied at 50c, and the time required for the adhesive tape to fall off the stainless steel plate was measured.

The block copolymer used was extruded using an extruder at a temperature of about 180C and pelletized.

The above results are shown in Table 1.

From the results shown in Table 1, it can be seen that the block copolymer of the present invention having a predetermined Tlv/ViN ratio has a balanced adhesive property and a high holding power.

In addition, the decoupling rate of the block copolymer after pelletization was measured, and almost no decoupling occurred when the coupling agent of the present invention was used. In Comparative Example), about 25% uncoupling was observed. As described above, the block copolymer of the present invention also has excellent heat resistance.

Claims (3)

[Claims] (1) General formula A-B-X-B-A (where A is a polymer block of an aromatic vinyl compound, B is a polymer block of a conjugated diene monomer, and X is a coupling agent) (representing residues of esters of monohydric aliphatic carboxylic acid and monohydric alcohol, respectively), and the weight ratio of A to B in the formula is 5 to 40:95 to 60, and the gel par of block A is The ratio of the weight average molecular weight (@M@_w) and number average molecular weight (@M@_N) measured by migration chromatography (
@M@_W/@M@_M) is 1.2 or less, and the weight average molecular weight of the polymer (@M@_W) is 50,000 to 500,0.
00 linear block copolymer. (2) Using a mixed solvent consisting of 5-50% by weight of an open-chain hydrocarbon solvent of C_4_-_5 and 95-50% by weight of a cyclic hydrocarbon solvent, 5-40% by weight of an aromatic vinyl compound and 95% of a conjugated diene monomer. ~60% by weight of a monolithium initiator in the presence of a polar compound selected from aromatic ethers and aliphatic ethers or tertiary monoamines having a dielectric constant of 2.5 to 5.0. to polymerize an aromatic vinyl compound to form an active polymer block A, and then add a conjugated diene monomer to form a polymer block B of the active monomer at the end of the polymer block A. After forming the active A-B block polymer, an ester of a monohydric aliphatic carboxylic acid and a monohydric alcohol is added as a coupling agent to bond the active A-B block polymer. 2. A method for producing a linear block copolymer according to item 1. (3) An adhesive composition containing the linear block copolymer according to claim 1.