JPH0781126B2 - Adhesive composition - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a linear A-B-X-B-A block copolymer comprising a polymer block A of an aromatic vinyl compound and a polymer block B of a conjugated diene monomer. (Wherein X represents a coupling agent residue).

[0002]

2. Description of the Related Art The performance required for an adhesive is the initial adhesive strength,
That the adhesion and holding power are well balanced,
Furthermore, how to improve the holding power among these characteristics is an issue. In order to solve this problem, various attempts have been made to improve linear or branched block copolymers such as polystyrene-polyisoprene-polystyrene that have been widely used for adhesives. Using the bifunctional or more coupling agents as one method, the rubbery teleblock copolymer represented the molecular weight distribution of the polystyrene block was wider than the molecular weight distribution of the total block copolymer in (S-D) _N -Y Polymer (wherein S represents a block of a monovinyl-substituted aromatic hydrocarbon polymer, D represents a block of a conjugated diene polymer, N represents an integer of at least 2, and Y represents a residue of a polyfunctional coupling agent). However, it is difficult to say that sufficient improvement can be obtained.

[0003]

DISCLOSURE OF THE INVENTION As a result of intensive investigations by the present inventors to improve the balance and holding power of respective properties of a pressure-sensitive adhesive using a block copolymer by using a method other than the above It was found that the above-mentioned problems can be solved by using a coupling agent, and a linear block copolymer in which the polymer block of the aromatic vinyl compound has a specific molecular weight distribution, and based on this finding To complete the present invention.

[0004]

That is, the present invention relates to the general formula A-B-X-B-A (where A is a polymer block of an aromatic vinyl compound and B is a conjugated diene-based monomer). The polymer block is represented by the following formula (X represents the residue of an ester of a monovalent aliphatic carboxylic acid and a monovalent alcohol as a coupling agent), and the weight ratio of A to B in the formula is 5 ~ 4
0: 95-60, the ratio (M _W / M _N ) of the weight average molecular weight (M _W ) and the number average molecular weight (M _N ) measured by gel permeation chromatography of Block A is 1.2 or less, and the polymer the weight average molecular weight of (M _W) is 50,000
The present invention provides a pressure-sensitive adhesive composition containing a linear block copolymer of 500,000.

The linear block copolymer used in the present invention is represented by the general formula A-B-X-B-A (where A is a polymer block of an aromatic vinyl compound and B is a conjugated diene monomer). Is a linear block copolymer represented by the formula (1), X represents a residue of an ester of a monovalent aliphatic carboxylic acid and a monovalent alcohol as a coupling agent) Using the above specific bifunctional compound as an agent, and measuring the weight average molecular weight (M _W ) and the number average molecular weight (M _N ) of the polymer block A of the aromatic vinyl compound measured by gel permeation chromatography. Ratio (M _W / M _N ) is 1.2 or less. The (M _W / M _N ) of the polymer block A affects the holding power of the pressure-sensitive adhesive, and if this value exceeds 1.2, the holding power will decrease. The preferable range of this value is 1.1 or less. The weight average molecular weight of the linear block copolymer used in the present invention (M
_W ) is 50,000 to 500,000, preferably 10
The range is from 50,000 to 400,000 and 50,000
If it is less than 0, the holding power when it is used as an adhesive is not sufficient.
If it exceeds 0,000, the preparation operation (workability) of the pressure-sensitive adhesive becomes difficult.

The linear block copolymer used in the present invention can be produced by the following method. That is, (1) First, an aromatic vinyl compound is polymerized with a monolithium initiator in a mixed solvent containing a polar compound. Although the polymerization mode is not particularly limited, for example, a batch-type polymerization method in which the aromatic vinyl compound and the initiator are charged into a batch polymerization system to carry out a polymerization reaction; the aromatic vinyl compound and the initiator are continuously polymerized A continuous polymerization method in which the aromatic vinyl compound and a part of the initiator are polymerized to a predetermined conversion rate and then the rest is added to continue the polymerization. Is mentioned. Polymerization depolymerization temperature is usually 0 ° C to 90 ° C, preferably 2 ° C.
It is in the range of 0 ° C to 70 ° C. When it is difficult to control the reaction temperature, it is preferable to control the temperature by reflux cooling using a reaction vessel equipped with a reflux condenser.

As the polar compound, among known polar compounds used as a vinyl content modifier or randomizer in the polymerization of a conjugated diene monomer or a vinyl aromatic compound with a lithium initiator,
Aromatic ethers and aliphatic ethers or tertiary amines having a relative dielectric constant of 2.5 to 5.0 are used. When a polar compound other than these is used, it is difficult to make the molecular weight distribution of the aromatic vinyl compound polymer block into a predetermined distribution, and further, the conjugated diene in the polymer block B in the linear block copolymer is It is not preferable because the amount of vinyl in the monomer unit is greatly increased. Examples of such polar compounds include aliphatic ethers such as diethyl ether and dibutyl ether; aromatic ethers such as diphenyl ether and anisole; tertiary monoamines such as trimethylamine, triethylamine and tripropylamine, and one or more of them. Is used. Aromatic vinyl compound polymer block with a predetermined molecular weight distribution,
The preferable amount of the polar compound used for the characteristics of the pressure-sensitive adhesive containing the obtained linear block copolymer is 0.1 to 100 mol, and more preferably 0.5 to 2 mol, per mol of the monolithium initiator.
It is in the range of 0 mol.

Aromatic vinyl compounds include styrene and α
-Methylstyrene, vinyltoluene, vinylnaphthalene, etc. are mentioned, and styrene is particularly preferable. Examples of the conjugated diene-based monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, piperylene and 2,4-hexadiene, and butadiene and isoprene are particularly preferable. The weight ratio of the aromatic vinyl compound to the conjugated diene monomer is 5 to 40:95.
-60, preferably 10-35: 90-65. When the use ratio of the aromatic vinyl compound is less than the lower limit, the holding power of the pressure-sensitive adhesive containing the block copolymer of the present invention decreases,
On the other hand, if the amount exceeds the above upper limit, the initial adhesive strength (tack) is lowered, which is not preferable.

As the monolithium initiator, known initiators which can initiate the polymerization of an aromatic vinyl compound or a conjugated diene monomer can be used, and methyllithium, n-propyllithium, n-butyllithium, sec. -Butyllithium and the like are shown as typical examples, but n is particularly preferable.
-Butyl lithium. The amount of the monolithium initiator used is usually 50 to 200 mmol per 1 g of the aromatic vinyl compound or the conjugated diene monomer.

As the polymerization solvent, a mixed solvent of a C _4-5 open chain hydrocarbon solvent and a cyclic hydrocarbon solvent which is inert to the monolithium initiator is used. As the C _4-5 open chain hydrocarbon solvent, n-butane, iso-butane, or a mixture thereof; 1-butene, isobutylene, trans-2-butene, cis-2-butene, or a mixture of two or more thereof; n -Pentane, iso-pentane, neo-pentane or a mixture of two or more thereof; 1-pentene, trans-2-pentene, cis-2-pentene or a mixture of two or more thereof. Further, examples of the cyclic hydrocarbon solvent include aromatic compounds such as benzene, tolhen, xylene, and alicyclic solvents such as cyclohexane.

The ratio of the C _4-5 open chain hydrocarbon solvent to the cyclic hydrocarbon solvent used is in the range of 5:95 to 45:55, preferably 10:90 to 40:60 in terms of polymerization ratio. Outside this range, the polymerization temperature rises, the molecular weight distribution of the aromatic vinyl compound polymer block becomes broad, and not only the polymer block having a predetermined (M _W / M _N ) ratio but also the polymerization activity is not obtained. It is not preferable because it causes deactivation of the seeds and becomes an impurity in the obtained linear block copolymer.

(2) Next, a conjugated diene monomer is added to the polymerization system in which the active aromatic vinyl compound polymer block A is present, and polymerization is carried out. The monomer is preferably continuously added to the polymerization system in order to control the reaction heat, but the method of adding the monomer is not limited to this method in the present invention. Thus, the polymer block B of the conjugated diene monomer is directly bonded to the polymer block A to form the active A
-A B block copolymer is produced. After the polymerization reaction of the conjugated diene-based monomer is substantially completed, a coupling agent is added to the polymerization system to bind the active AB block copolymer, and to obtain the desired linear AB. A -X-B-A block copolymer (wherein X represents the residue of the coupling agent) is obtained.

The coupling agent used here is an ester of a monovalent aliphatic carboxylic acid and a monovalent alcohol, and the use of this coupling agent makes the linear block copolymer used in the present invention resistant to heat. Sex is given. Examples of such a coupling agent include esters of an aliphatic monocarboxylic acid and an aliphatic monohydric alcohol or an aromatic monohydric alcohol. As the aliphatic monocarboxylic acid, acetic acid, formic acid, propionic acid, butyric acid, valeric acid, trimethylacetic acid, caproic acid, etc .; as the aliphatic monohydric alcohol,
Methyl alcohol, regular butyl alcohol, regular propyl alcohol, isopropyl alcohol, amyl alcohol and the like; examples of aromatic monohydric alcohols include aliphatic monocarboxylic phenol, cresol and naphthol. The amount of coupling agent used is 0.2 to 3 times the amount of monolithium initiator normally used. If it deviates from this range, the coupling rate will decrease, which is not preferable. 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 is usually in the range of several seconds to 1 hour.

(3) After completion of the coupling reaction, if necessary, water, alcohol, acid or the like is added to deactivate the active species, an antioxidant is added, and then the polymer is separated and dried by a known method. To obtain the linear block copolymer used in the present invention.

The pressure-sensitive adhesive composition of the present invention is mainly composed of the linear block copolymer obtained as described above and a tackifying resin (tackfire). As the tacky fire used in the present invention, a conventionally known tacky fired used for an adhesive using a conventional block copolymer similar to the linear block copolymer used in the present invention can be used. Specifically, rosin; disproportionated rosin,
Modified rosins such as dimerized rosins; Esterification products of glycol, glycerin, pentaerythritol, etc. with rosins or modified rosins; Terpene resins; Aliphatic, aromatic or alicyclic or aliphatic-aromatic co-polymers Polymerization type hydrocarbon resins or their hydrides; phenol resins; coumarone-indene resins and the like. Particularly preferred tackifiers are aliphatic hydrocarbon resins and aliphatic-aromatic copolymer hydrocarbon resins which are compatible with the linear block copolymer used in the present invention. The amount of Tatsuki Fire is usually 10 to 100 parts by weight of the block copolymer.
It is 150 parts by weight.

If necessary, other compounding agents such as a softening agent (plasticizer) and an antioxidant can be added to the pressure-sensitive adhesive composition of the present invention. As the softening agent, conventionally known aromatic, paraffinic or naphthene-based extender oils (extender oils), liquid polymers such as polybutene and polyisobutylene, which are used in adhesives, can be used. The amount used is usually 100 parts by weight or less per 100 parts by weight of the linear block copolymer. 2,6-di-t- as antioxidant
Butyl-p-cresol, di-t-butyl-4-methyl-phenol and other hindered phenolic compounds, dilauryl thiopropionate and other thiodicarboxylate esters, tris (nonylphenyl) phosphite and other sub-substances Phosphates and the like are used alone or as a mixture.

The pressure-sensitive adhesive composition of the present invention is dissolved in n-hexane, cyclohexane, benzene, toluene or the like as a solution-type pressure-sensitive adhesive, or as an emulsion-type pressure-sensitive adhesive dispersed in water using an emulsifier, or without. It can be used as a solvent hot-melt type pressure-sensitive adhesive. Particularly suitable are hot melt adhesives.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following examples. In the examples, comparative examples and reference examples, the number of parts and% are based on weight unless otherwise specified.

Reference Example Using a pressure resistant reactor of 50 liters, 18.75 kg of a mixed solvent of n-butane / cyclohexane = 30/70, 200 mmol of dibutyl ether, and 100 mmol of n-butyllithium initiator were present. First, 1.125 kg of styrene was first polymerized at 30 ° C. for 1 hour, 6.875 kg of isoprene was subsequently added, and the temperature was controlled by reflux cooling for about 1 hour so that the reaction temperature was between 50 ° C. and 60 ° C. Half polymerized. Subsequently, 50 mmol of ethyl acetate was added to carry out a coupling reaction. 50m of methanol as a polymerization terminator in the reaction mixture
1, 40 g of 4-methyl-2,6-di-t-butylphenol as an oxidation stabilizer was added, and the mixed solution was added little by little to water heated to 85 ° C. to 95 ° C. to volatilize the solvent. The obtained polymer was pulverized and dried with hot air at 85 ° C. (Polymer 1). In the above production example, triethylamine / butyl acetate (polymer 2); dibutyl ether / isopropyl acetate (polymer 3); triethylamine / butyl acetate (polymer 4); dibutyl ether / phenyl acetate (polymer) as the polar compound / coupling agent, respectively. A linear block copolymer was produced in the same manner except that 5) was used. A polymer 6 was obtained in the same manner as the polymer 1 except that the ratio of styrene to isoprene used was 20:80. 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 7). Also as a solvent n
-Butane / cyclohexane = 50/50 in the same manner as in the preparation of polymer a (Polymer 8), polar compound / diglyme / butyl acetate (polymer 9) as coupling agent; triethylamine / phenyl benzoate (polymer), respectively. Polymer 1 except that 10) is used
A linear block copolymer was obtained in the same manner as in. A polymer 11 was obtained in the same manner as the polymer 6 except that n-butane / cyclohexane (50/50) was used as the solvent.
The properties of each linear block copolymer thus obtained are shown in Tables 1 and 2. The weight average molecular weight (M _W ) and number average molecular weight (M _N ) were determined by gel permeation chromatography according to a conventional method (HLC-manufactured by Toyo Soda Kogyo Co., Ltd.).
Use 802A. Solvent tetrahydrofuran, measuring temperature 4
0 ° C. ) The molecular weight was calculated as polystyrene. The 3,4-bond content of the isoprene unit was determined by infrared spectroscopy.

(Example 1) A-B-X obtained in Reference Example
-B-A type linear block copolymer 100 parts, tackifying resin 100 parts, naphthene-based process oil (Shellex 371, Shell Chemical Co., Ltd.) 30 parts and antioxidant 1
Parts were dissolved and mixed in toluene to prepare a pressure-sensitive adhesive solution having a nonvolatile content of 40%. Next, this solution was applied onto a polyester film having a thickness of 25 μm so as to have a glue thickness of 25 μm to prepare an adhesive tape, and its initial adhesive force, adhesive force and holding force were measured. The initial adhesive strength is JIS Z-0237.
According to the above, a 10 cm long adhesive tape was attached to the slope of a stainless steel plate having an inclination angle of 30 degrees at 23 ° C. with the adhesive surface facing upward, and the diameter was 3/32 from the position 10 cm above the slope.
Steel balls of 30 sizes from 1 inch to 1 inch are displayed at the maximum diameter of a ball that rolls at an initial speed of 0 and stops on an adhesive tape. Adhesive strength is 280 according to JIS Z-0237. Adhesive tape having a width of 10 mm and a length of 100 mm was affixed to a stainless steel plate polished with the water-resistant polishing paper, and peeled in a direction of 180 degrees at a speed of 200 mm / min at 23 ° C. to measure, and a holding force is JIS Z-0237.
25 mm x 10 on a stainless steel plate treated in the same manner according to
Stick the adhesive tape so that the area of
A load of 1 kg was applied at 0 ° C., and the time required for the adhesive tape to fall off the stainless steel plate was measured. The linear block copolymer was extruded at a temperature of about 180 ° C. using an extruder and pelletized. The above results are shown in Tables 1 and 2.

[0021]

[Table 1]

[0022]

[Table 2]

From the results shown in Tables 1 and 2, it can be seen that the pressure-sensitive adhesive composition of the present invention has a good balance of pressure-sensitive adhesive properties and a high holding power.

[0024]

As described above, according to the present invention, a pressure-sensitive adhesive composition having an excellent balance of pressure-sensitive adhesive properties can be obtained.

Claims (1)

[Claims] 1. A general formula A-B-X-B-A (wherein 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. Represents a residue of an ester of a monohydric aliphatic carboxylic acid and a monohydric alcohol, respectively, and A in the formula
The weight ratio of B to B is 5 to 40:95 to 60, and the ratio of the weight average molecular weight (M _W ) and the number average molecular weight (M _N ) measured by gel permeation chromatography of block A (M
A pressure-sensitive adhesive composition containing a linear block copolymer having a _W / M _N of 1.2 or less and a polymer weight average molecular weight (M _W ) of 50,000 to 500,000 and a tackifying resin .