JPH0535746B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel adhesive composition containing as a main component a vinyl aromatic compound-conjugated diene compound block copolymer having improved adhesive properties, and more specifically, it relates to a novel adhesive composition containing a vinyl aromatic compound-conjugated diene compound block copolymer having improved adhesive properties, and more specifically, The present invention relates to a novel hot-melt pressure-sensitive adhesive composition containing as a main component a mixture of two vinyl aromatic compound-conjugated diene compound block copolymers having a specific structure in a specific ratio. [Prior Art] Conventionally, hot melt adhesives have been disclosed, for example, in Japanese Patent Publication No. 56-50758 or Japanese Unexamined Patent Application Publication No. 53-1989.
The one described in Publication No. 102938 is known. In recent years, in the field of hot-melt adhesives, there has been an increasing demand for adhesives having excellent properties that combine low-temperature initial adhesive strength and high-temperature holding power. [Problems to be Solved by the Invention] However, the above-mentioned conventional pressure-sensitive adhesives simultaneously satisfy all of the important properties required for the pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet, such as low-temperature initial adhesive strength and high-temperature holding power. isn't it. The present invention was made against the background of the above-mentioned conventional technical problems, and an object of the present invention is to provide an adhesive having both low-temperature initial adhesive strength and high-temperature retention strength. [Means for Solving the Problems] That is, the present invention provides (a) a compound obtained from a vinyl aromatic compound and a conjugated diene compound and having a weight average molecular weight of
70,000 to 500,000 and a vinyl aromatic compound component content of 5 to 40% by weight, a linear block copolymer A optionally end-grouped with an isocyanate compound or an isothiocyanate compound. , obtained from a vinyl aromatic compound and a conjugated diene compound, and has a weight average molecular weight of 3000 to 50000.
and the content ratio of the vinyl aromatic compound component is 3
-50% by weight of isocyanate compound or isothiocyanate compound-terminated linear block copolymer B;
Copolymer mixture 100 in proportions from 10 to 50
(b) 20 to 200 parts by weight of a tackifier, and (c) 0 to 100 parts by weight of a softener. The copolymer mixture (a) in the present invention is a mixture of the above-mentioned block copolymer A and block copolymer B. Here, the block copolymer A is a direct polymer obtained by copolymerizing a vinyl aromatic compound and a conjugated diene compound, or by further terminal-grouping with an isocyanate compound or an isothiocyanate compound as necessary. A chain block copolymer having a weight average molecular weight of 70,000 to 500,000, preferably 100,000 to 300,000, and a vinyl aromatic compound component content of 5 to 40% by weight, preferably 10 to 30% by weight. %. The weight average molecular weight of block copolymer A is
If it is less than 70,000, the high temperature holding power of the composition of the present invention will be insufficient, while if it exceeds 500,000, the low temperature initial adhesive strength of the composition of the present invention will be insufficient. Furthermore, if the content of the vinyl aromatic compound component in the block copolymer A is less than 5% by weight, the high temperature holding power of the composition of the present invention will be insufficient, while if it exceeds 40% by weight, the low temperature holding power of the composition of the present invention will be insufficient. Initial adhesive strength becomes insufficient. Furthermore, by end-grouping the block copolymer A with an isocyanate compound or an isothiocyanate compound, it is expected that the high-temperature holding power of the resulting composition will be improved. On the other hand, block copolymer B is a linear block copolymer obtained by copolymerizing a vinyl aromatic compound and a conjugated diene compound, and further adding a terminal group with an isocyanate compound or an isothiocyanate compound. The weight average molecular weight is 3000 to 50000, preferably 5000 to 40000, and the content of the vinyl aromatic compound component is 3 to 50% by weight, preferably 5 to 30% by weight. The weight average molecular weight of block copolymer B is 50000
If it exceeds 3,000, the low-temperature initial adhesive strength of the composition of the present invention will be insufficient, while if it is less than 3,000, the die-cutting properties of the composition of the present invention will be poor. Furthermore, if the content of the vinyl aromatic compound component in block copolymer B is less than 3% by weight, the high temperature holding power will be insufficient, while if it exceeds 50% by weight, the low temperature initial adhesive strength of the composition of the present invention will be insufficient. becomes. Furthermore, the molecular chain ends of block copolymer B must be end-grouped with an isocyanate compound or an isothiocyanate compound, and if such end-grouping is not performed, the resultant composition Low-temperature adhesive strength becomes inferior. The mixing ratio of block copolymer A and block copolymer B is 90-50:10-50, preferably 85-60:15-40 by weight. If the proportion of block copolymer A exceeds 90% by weight, the low temperature initial adhesive strength of the composition of the present invention will be insufficient, while if it is less than 50% by weight, the high temperature holding power of the composition of the present invention will be insufficient. The block copolymer A has a block bond type represented by any of the following general formula (1) S-I-S general formula (2) S-I general formula (3) I-S-I,
Alternatively, it is further terminated with an isocyanate compound or an isothiocyanate compound. Here, S represents a polymer block of a vinyl aromatic compound, and I represents a polymer block of a conjugated diene compound. Particularly preferred are those represented by general formula (1) or general formula (2). Block copolymer A represented by general formula (1) can be produced, for example, as follows. That is, an ether or a tertiary amine is added to a hydrocarbon solvent as necessary, and a vinyl aromatic compound is first polymerized using an organic lithium compound as a polymerization initiator. After this polymerization reaction is substantially completed, a conjugated diene compound is added and polymerized,
After this polymerization reaction is substantially completed, a vinyl compound is added and polymerized successively. Furthermore, an isocyanate compound or isothiocyanate compound may be added in an amount of 1 to 20 times the mole of the organolithium initiator to form a terminal group. In addition, block copolymer A represented by general formula (1)
Another method for producing is, for example, adding ether or tertiary amine to a hydrocarbon solvent as necessary, using an organolithium compound as a polymerization initiator, first polymerizing a vinyl aromatic compound, and starting the polymerization reaction. It is also possible to produce the polymer by adding a conjugated diene compound to polymerize the polymer after substantially completing the process, and then adding a coupling agent. Next, the block copolymer B is represented by either the general formula (4) S-I-Y general formula (5) S-I-S-Y general formula (6) I-S-I-Y. It is represented by the block connection type. Here, S and I are blocks according to the above definitions, and Y is an isocyanate compound or an isocyanate compound. The block copolymer B is preferably one represented by general formula (5) or general formula (6). The method for producing block copolymer B is similar to the method described for block copolymer A above. Examples of the vinyl aromatic compound for the above block copolymer A or block copolymer B include styrene, α-ethylstyrene, p-methylstyrene, m-methylstyrene, o-methylstyrene,
p-tert-butylstyrene, dimethylstyrene,
Vinylnaphthalene etc. can be used. this house,
Styrene is preferred. Further, as the conjugated diene compound, butadiene, isoprene, piperylene, etc. can be used.
Among these, isoprene is preferred. Furthermore, the isocyanate compound used in the production of copolymer B or, if necessary, copolymer A, includes, for example, phenyl isocyanate, o
-, m-, p-chlorophenyl isocyanate,
Methyl isocyanate, ethyl isocyanate,
Examples include n-propyl isocyanate, n-butyl isocyanate, octadecyl isocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and the like. Furthermore, examples of the isothiocyanate compound used in the production of copolymer B or, if necessary, copolymer A, include phenylisothiocyanate, o-, m-, p-chlorophenylisothiocyanate, Examples include tolylene diisothiocyanate, hexately diisothiocyanate, methylisothiocyanate, ethylisothiocyanate, n-propylisothiocyanate, n-butylisothiocyanate, octadecylisothiocyanate, and tolylene diisothiocyanate. On the other hand, as a polymerization method for producing the block copolymer A or B, either an isothermal polymerization method or an adiabatic polymerization method can be used. Moreover, the polymerization temperature range at this time is 30 to 120°C. Further, examples of the hydrocarbon solvent used in the production of block copolymer A or B include cyclopentane, cyclohexane, benzene, ethylbenzene, xylene, and mixed solvents thereof such as pentane, hexane, heptane, and butane. be able to. Furthermore, examples of the ether or tertiary amine added to the hydrocarbon solvent as necessary include tetrahydrofuran, diethyl ether,
Anisole, dimethoxybenzene, ethylene glycol, dimethyl ether, triethylamine,
Ether compounds and tertiary amine compounds such as N-dimethylaniline and pyridine are used. Furthermore, the block copolymer A or B may be hydrogen-converted at an appropriate ratio if necessary. Furthermore, examples of the organic lithium compound as a polymerization initiator include n-butyllithium,
sec-butyllithium, tert-butyllithium,
n-hexyllithium, iso-hexyllithium,
Phenyllithium, naphthyllithium, etc. are used. Furthermore, examples of the coupling agent used in other production methods of block copolymer A include dichlorosilane, monomethyldichlorosilane,
Dimethyldichlorosilane, monoethyldichlorosilane, monobutyldichlorosilane, dichlorotin, monomethyldichlorotin, monoethyldichlorotin, dibutyldibromtin, and the like are used. A tackifier (b) is added to the copolymer mixture (a) obtained by mixing block copolymers A and B as described above.
is blended. Such tackifiers (b) include rosin resins, polyterpene resins, synthetic polyterpene resins, alicyclic hydrocarbon resins, coumaron resins, phenol resins, terpene-phenol resins,
Aromatic hydrocarbon resins, aliphatic hydrocarbon resins, etc. are used. Among these, especially rosin resin,
Polyterpene resins and alicyclic hydrocarbon resins are preferred. These tackifiers (b) can be used alone or in combination of two or more. The amount of the tackifier (b) is 20 to 200 parts by weight, preferably 50 to 150 parts by weight, based on 100 parts by weight of the copolymer mixture (a). If the amount of the tackifier (b) is outside the above-mentioned range, there is a risk that appropriate low-temperature initial adhesive strength and high-temperature holding power will not be sufficient. The adhesive composition of the present invention may further contain a softener (c), and the softener (c) may include naphthenic, paraffinic, or aromatic process oils alone or in combination. A mixture of more than one species can be used. The blending amount of the softener (c) is 0 to 100 parts by weight, preferably 20 to 70 parts by weight, per 100 parts by weight of the copolymer mixture (a).
Parts by weight. If the amount of the softener (c) exceeds 100 parts by weight, the softener will ooze out onto the adhesive surface over time, causing undesirable effects. In addition to the above, the adhesive composition of the present invention may optionally contain stabilizers such as antioxidants and ultraviolet absorbers, and inorganic substances such as calcium carbonate, talc, clay, titanium oxide, silica, magnesium carbonate, and carbon black. Fillers, colorants, etc. may also be added. Each component of the above adhesive composition is heated in a general tank mixer, closed kneader, etc.
If necessary, they are mixed in a nitrogen gas atmosphere. The pressure-sensitive adhesive composition of the present invention has the greatest economical effect when it is heated and mixed and directly applied to form a pressure-sensitive adhesive layer. However, it is also possible to apply a mixture using a conventional solvent or by forming an emulsion. The adhesive composition of the present invention obtained in this way forms an adhesive layer when applied to a base material, so it can be used for various adhesive tapes, labels, adhesives for fixing various lightweight plastic molded products, and backing adhesives for fixing carpets. It is effective as an adhesive layer forming material for frozen foods, adhesive tapes used in cold regions, and labels. [Examples] Hereinafter, the present invention will be specifically explained with reference to Examples, but the scope of the present invention is not limited by these. In addition, in the examples, parts and % are, in principle, based on weight. Reference Example Production of Block Copolymer A (1) In a washed and dried autoclave equipped with a stirrer and jacket, 5000 g of a mixed solution of cyclohexane and n-pentane were mixed at a ratio of 9:1 (weight ratio). Tetrahydrofuran 0.12g
After charging, the internal temperature was brought to 60℃. Next, a hexane solution containing 0.5 g of n-butyllithium was added, and then 120 g of styrene was added and polymerized for 60 minutes. The polymerization conversion rate of styrene here was 100%. Next, 700 g of isoprene was added and polymerized for 60 minutes. The polymerization conversion rate of isoprene here was 100%. Finally, 120 g of styrene was added and polymerized for 60 minutes. The polymerization conversion rate of styrene here is also
It was 100%. During each of the above polymerization reactions, the system temperature was maintained at 60°C. After the final polymerization process is completed, 2,6-di-tert-butyl-p-cresol is added to the polymer solution, and then the mixture of cyclohexane and n-pentane is removed by heating to form a block copolymer A1. I got it. Further, block copolymer A2 was produced in the same manner as A1 except that the amount of monomer was changed. (2) Next, a block copolymer A3 terminal-terminated with an isocyanate compound was produced by the following procedure. That is, using the same equipment as in the production of block copolymer A1, 120 g of styrene,
700 g of isoprene and 120 g of styrene were successively polymerized. Thereafter, a tetrahydrofuran solution containing 1.86 g of phenyl isocyanate was added, and then 2,6-di-tert-butyl-p-cresol was added, and the solvent was removed by heating to obtain block copolymer A3. . (3) Next, using the same equipment as in the production of block copolymer A1, 120g of styrene and
After sequentially polymerizing 450 g of isoprene, a cyclohexane solution containing 0.9 g of monomethyldichlorosilane was added, and then 2,6-di-tert-butyl-p-cresol was added, and the solvent was removed by heating to form a block copolymer. Obtained a combined A4. (4) Next, using the same equipment as in the production of block copolymer A3, except that 2.15 g of phenyl isothiocyanate was used instead of phenyl isocyanate, the block copolymer was produced in the same manner as in the production of block copolymer A3.
Got A5. (5) Next, using the same equipment as in the production of block copolymer A1 except for changing the monomer amount,
Comparative block copolymers a1 to a4 as shown in Table 1 were produced in the same manner. Production of block copolymer B (1) In a washed and dried autoclave equipped with a stirrer and a jacket, add tetrahydrochloride to 500 g of a mixture of cyclohexane and n-pentane at a ratio of 9:1 (weight ratio). Fran 0.02g
After charging, the internal temperature was brought to 60℃. Next, a hexane solution containing 0.5 g of n-butyllithium was added, and then 12 g of styrene was added and polymerized for 60 minutes. The polymerization conversion rate of styrene here was 100%. Next, 70 g of isoprene was added and polymerized for 60 minutes. The polymerization conversion rate of isoprene here was 100%. A tetrahydrofuran solution containing 1.86 g of phenyl isocyanate was then added. During each of the above polymerization reactions, maintain the system temperature at 60 to 70℃.
I kept it. After the final polymerization process, 2,6-di-tert-butyl-p-cresol was added to the polymer solution, and then cyclohexane and n
- The mixed solution with pentane was removed by heating to obtain block copolymer B1. In addition, comparative block copolymer b1 was produced in the same manner as above except that phenyl isocyanate was not added. (2) In an autoclave equipped with a washed and dried stirrer and jacket, add 0.12 g of tetrahydrofuran to 5000 g of a mixture of cyclohexane and n-pentane at a ratio of 9:1 (weight ratio).
After charging, the internal temperature was brought to 50℃. Next, a hexane solution containing 0.5 g of n-butyllithium was added, and then 30 g of styrene was added and polymerized for 60 minutes. The polymerization conversion rate of styrene here was 100%. Next, 240 g of isoprene was added and polymerized for 60 minutes. The polymerization conversion rate of isoprene here was 100%. Furthermore, 30 g of styrene was added and polymerized for 60 minutes. The addition rate of styrene was 100%. Then hexamethylene diisocyanate
A solution containing 2.65 g of tetrahydrofuran was added. During each of the above polymerization reactions, maintain the system temperature at 60 to 70℃.
I kept it. After the final polymerization process, 2,6-di-tert-butyl-p-cresol was added to the polymer solution, and then cyclohexane and n
- The mixed solution with pentane was removed by heating to obtain block copolymer B2. In addition, comparative block copolymer b2 was produced in the same manner as above except that hexamethylene diisocyanate was not added. (3) 60g of styrene, 660g of isoprene, styrene
Comparative block copolymer b3 was produced in the same manner as in the production of B2, using the same equipment as in the production of B2, except that 2.65 g of hexamethylene diisocyanate was added after sequential polymerization of 60 g. Next, using the same equipment as in the production of block copolymer b3, except for changing the monomer amount,
Comparative block copolymers b4 to b6 shown in Table 1 were produced in the same manner. Details of the block copolymer obtained as described above are shown in Table 1.

[Table] Examples 1 to 5 and Comparative Examples 1 to 17 Each formulation having the composition shown in Table 2 was placed in a mixing tank heated to 160°C and stirred and mixed for 60 minutes to form a uniform and smooth product. A pressure-sensitive adhesive composition having fluidity was obtained. Each of the adhesive compositions was taken out in a molten state and coated onto a base material made of polyester film to a thickness of 30 microns using an applicator to prepare adhesive tape samples. For each of the adhesive tape samples, low-temperature initial adhesive strength, peel strength, high-temperature retention strength, and die-cutting properties were measured. The results are shown in Table 2. In addition, various measurements were based on the following methods. The initial adhesion strength at low temperature was determined by the tilted ball tack measurement method (tilt angle: 30°, measurement temperature: 5°C). Peel strength was determined in accordance with JIS Z 1522 (180° constant speed peel strength test, measurement temperature: 25°C). High temperature holding power was based on JIS Z 1524. However, the pasting area was 10 x 10 mm, and the time taken for a 1 kg weight to fall was measured (measured at a temperature of 45 mm).
℃). The quality of die-cutting was determined by the method described below. That is, a high-quality paper is hot-melt coated with an adhesive composition to a thickness at a predetermined temperature, this is pasted on release paper, and then cut into a size of 20 cm x 4 cm. Next, a punching blade with a size of 1.5 cm x 1.5 cm is used to cut the high-quality paper.
When punching out two rows of pieces, a total of 20 pieces, and then peeling off the excess from the release paper by hand, if the number of adhesive labels that were peeled off together is 0 to 1, mark ○.
The quality of the die-cutting property was determined by marking △ when the number of sheets was 2 to 3, and marking × when there were 4 or more sheets.

【table】

【table】

〔Effect of the invention〕

The adhesive composition of the present invention can provide an adhesive with excellent low-temperature initial adhesive strength and high-temperature retention strength, so when the composition is used for a tape or label, low-temperature initial adhesive strength, An adhesive tape or adhesive label having excellent properties in high temperature holding power, peel strength and die-cutting properties can be obtained.

Claims (1)

[Scope of Claims] 1 (a) Obtained from a vinyl aromatic compound and a conjugated diene compound, and has a weight average molecular weight of 70,000 to 70,000.
500,000 and a vinyl aromatic compound component content of 5 to 40% by weight, linear block copolymer A optionally end-grouped with an isocyanate compound or isothiocyanate compound, and vinyl Obtained from an aromatic compound and a conjugated diene compound, with a weight average molecular weight of 3000~
50,000 and a linear block copolymer B terminal-terminated with an isocyanate compound or an isothiocyanate compound, and the content of the vinyl aromatic compound component is 3 to 50% by weight.
Contains 100 parts by weight of a copolymer mixture in a ratio of 90 to 50:10 to 50, (b) 20 to 200 parts by weight of a tackifier, and (c) 0 to 100 parts by weight of a softener. An adhesive composition characterized by: