JPH0674290B2 - Carboxy modified block copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel carboxy-modified block copolymer, particularly a block copolymer obtained by copolymerizing a vinyl aromatic compound and a conjugated diene compound and further carboxy-modifying the copolymer. A polymer having a non-elastomeric vinyl aromatic compound block in its molecule and a vinyl aromatic compound elastomeric copolymer block mainly containing a conjugated diene compound, having a carboxyl group at either end It relates to a block copolymer having a group.

Recently, in the field of hot-melt pressure-sensitive adhesives, demands for thermoplastic elastomers having excellent properties such as initial adhesive strength, peel strength and die-cutting property are increasing.

A linear block copolymer obtained from a vinyl aromatic compound and a conjugated diene compound is known in the technical field of anionic polymerization, and is disclosed, for example, in JP-B-40-23798 and JP-B-46-32415. Has been done. However, the block copolymers obtained by these methods have a poor balance between initial adhesive strength, peel strength and die-cutting property when they are used as a component of a pressure-sensitive adhesive, and are not yet sufficiently satisfactory.

Therefore, the present inventors have arrived at the present invention as a result of extensive studies to obtain a block copolymer having excellent initial adhesive strength, peel strength and die-cutting property when used as a component of an adhesive. That is, the present invention is obtained by block-copolymerizing a vinyl aromatic compound and a conjugated diene compound using an organic lithium compound as an initiator in a hydrocarbon solvent and then performing carboxy modification, and the content of the vinyl aromatic compound is 5% by weight. The carboxy-modified block copolymer is 40% by weight or more, and further satisfies the following conditions (a) and (b).

Condition (a) General formula AB-COOH or general formula B-A-COOH (In the formula, A is a block of a vinyl aromatic compound polymer and contains 50 to 97% by weight of all vinyl aromatic compounds, B is a block of a copolymer mainly composed of a conjugated diene compound with a vinyl aromatic compound, and has a taper block in which the proportion of the vinyl aromatic compound gradually increases.).

Condition (b) Among vinyl aromatic compounds, the ratio of vinyl aromatic compounds constituting a chain of 4 or less monomer units to all vinyl aromatic compounds is 5 to 30% by weight.

The content ratio of the vinyl aromatic compound in the block copolymer of the present invention is 5% by weight or more and 40% by weight or less, preferably 7% by weight or more and 30% by weight or less. If the content is less than 5% by weight, the peel strength and die-cutting property when used as an adhesive is poor, while if it exceeds 40% by weight, the initial adhesive strength is insufficient.

Here, the die-cutting property means that at the time of production of an adhesive label, the adhesive base material of the adhesive sheet attached to the peeling paper is die-cut into a desired label shape with a die, and unnecessary portions are removed from the peeling paper. If the die-cutting property is poor, the adhesive base material adheres to the die, and even the part required as an adhesive label tends to peel off from the peeling paper. This poor die-cutting property is the most serious drawback when applying a heat-melting type pressure-sensitive adhesive using a thermoplastic block copolymer to the use of pressure-sensitive adhesive labels.

The block copolymer of the present invention is characterized by the general formula AB-CO
OH or B-A-COOH in which the A portion contains 50 to 97% by weight of the total vinyl aromatic compound, the B portion has a taper block, and the specific proportion of the total vinyl aromatic compound is a monomer unit. It is contained in a state that constitutes a specific number of chains. Due to these characteristics, when the block copolymer of the present invention is used as an adhesive, initial adhesive strength, peeling strength and die-cutting property are remarkably improved. And, those represented by the general formula AB-COOH are particularly preferable.

The ratio of the vinyl aromatic compound in the A portion of the block copolymer of the present invention to the total vinyl aromatic compound is 50 to 97% by weight.
And preferably 70 to 96% by weight. If this ratio is less than 50% by weight, the peel strength and holding power when used as an adhesive will be poor, and conversely if it exceeds 97% by weight, the die-cutting property will be poor. On the other hand, the portion B contains a taper block in which the vinyl aromatic compound gradually increases, and the number of the taper block is 1 or more, preferably 2 to 10, and more preferably 3 to.
7 is good. When the number of taper blocks is less than 2, the die-cutting property tends to be poor when used as an adhesive,
If it exceeds 10, the peel strength when used as an adhesive is poor.

The chain distribution of the vinyl aromatic compound in the B portion of the block copolymer is such that the amount of the chain of the vinyl aromatic compound having 1 to 4 monomer units is 5 to 30% by weight of the total vinyl aromatic compound, It is preferably 15 to 30% by weight. When the amount of the chain-like compound of 4 or less is less than 5% by weight, the peel strength when used as a pressure-sensitive adhesive is poor, while when it exceeds 30% by weight, the initial adhesive strength and die-cutting property when used as a pressure-sensitive adhesive are poor.

Further, the block copolymer of the present invention is one in which the end of the B portion or the A portion is modified with a carboxyl group, but when it is not carboxy modified, the peel strength and holding power are poor.

The block copolymer of the present invention can be produced by the following method.

That is, when a compound represented by the general formula AB-COOH is produced, an ether or a tertiary amine is added to a hydrocarbon solvent and an organolithium compound is used as an initiator. After 3 to 39% by weight, preferably 9 to 19% by weight, of the total amount of the compound used, is polymerized alone to substantially complete the polymerization reaction, (2) the conjugated diene compound is 85 to 99% by weight and the vinyl aromatic compound. A mixture with 1 to 15% by weight of the compound is added, for example, in 3 to 10 divided steps to successively polymerize, and if necessary, butadiene is added once to polymerize, and (3) to finally carboxylate Carbon dioxide gas is blown into the system, and then anhydrous hydrogen chloride is reacted.

On the other hand, when producing the compound represented by the general formula B-A-COOH, the steps (1) and (2) may be reversed.

In the step (2) of adding the mixture of the conjugated diene compound and the vinyl aromatic compound and polymerizing, the number of addition is 2
In the above case, it is preferable that the amount of the monomer used in each time is approximately the same, and it is desirable that the polymerization is performed at almost 100% in each time. As a method of adding the monomer mixture, a method of adding a previously prepared monomer mixture, a method of simultaneously adding a conjugated diene compound and a vinyl aromatic compound, or the like is used.

The number of times the monomer mixture is added in the above polymerization step (2) is the number of taper blocks. That is, when the monomer mixture is added to the system, the conjugated diene compound is preferentially polymerized, and then the polymerization reaction is gradually promoted so that the proportion of the vinyl aromatic compound involved in the polymerization is increased, and the monomer units are chained. As the number of vinyl aromatic compound chains increases, the number of chains increases as the polymerization proceeds.

The copolymer of a vinyl aromatic compound and a conjugated diene compound having a preferable chain distribution of vinyl aromatic compound can be obtained by adding ether or tertiary amine to a hydrocarbon solvent and polymerizing. When ether or tertiary amine is added, the amount of vinyl aromatic compounds having a chain number of 1 to 4 increases, but the ratio of the chain aromatic compounds having a chain number of 1 to 4 to all vinyl aromatic compounds is 5 to 30% by weight. Is preferable, and more preferably 15 to 30% by weight.

From the viewpoint of controlling the chain distribution of the vinyl aromatic compound, the amount of ether or tertiary amine used is preferably 0.005 to 5 parts by weight, more preferably 0.05 parts by weight, per 100 parts by weight of the monomer.
05 to 0.5 parts by weight.

The vinyl aromatic compound used to obtain the block copolymer of the present invention includes styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, o-methylstyrene, p-tert-butylstyrene, Dimethyl styrene, vinyl naphthalene, etc. can be used. Of these, styrene is preferred. As the conjugated diene compound, butadiene, isoprene, piperylene, etc. can be used.
Of these, isoprene is preferred.

The weight average molecular weight of the block copolymer of the present invention is preferably 10,000 to 500,000, more preferably 50,000 to 300,000. The weight average molecular weight of part A is 3,000 to 100,0
The weight average molecular weights of the 00 and B parts are preferably 47,000 to 200,000.

Block copolymerization of a vinyl aromatic compound and a conjugated diene compound may be carried out by either an isothermal polymerization method or an adiabatic polymerization method, and a preferable polymerization temperature range is 10 to 120 ° C.
Is.

Examples of the hydrocarbon solvent used for the above block copolymerization reaction include cyclopentane, cyclohexane, benzene, ethylbenzene, xylene, and mixtures thereof with pentane, hexane, heptane, butane, and the like.

Examples of the organic lithium compound include n-butyl lithium, sec-butyl lithium, tert-butyl lithium, n
-Hexyl lithium, iso-hexyl lithium, phenyl lithium, naphthyl lithium, etc.
It is used in a proportion of 0.04 to 1.0 part by weight per 0 part by weight.

As the ether or tertiary amine, for example, an ether compound such as tetrahydrofuran, diethyl ether, anisole, dimethoxybenzene, ethylene glycol dimethyl ether, triethylamine, N-dimethylaniline, pyridine, or the like, and a tertiary amine compound are used.

For the carboxy modification of the terminal of the block copolymer, for example, the following method is used. That is, under a pressure of 1 to 10 kg / cm ² (gauge pressure), dry carbon dioxide is introduced into the polymerization reaction system in an amount of 2 to 50 times the stoichiometrically required amount. The reaction temperature is 0 to 50 ° C. Anhydrous hydrogen chloride is then added in an excess of about 20% of the stoichiometrically required amount. The reaction time is 10 to 60 minutes and the reaction temperature is 0.
~ 50 ℃ Then, the obtained modified block copolymer is washed with a large amount of water to remove excess hydrogen chloride.

The modified block copolymer of the present invention is particularly suitable for use as a hot melt adhesive. In this case, the modified block copolymer of the present invention can be used alone or in combination with other block copolymers. Here, as the other block copolymer, one represented by the general formula A (BA) _n or the general formula (AB) _n (where A and B are as defined above, n is Represents an integer from 1 to 10.)
Can be preferably used. Of course, in order to actually obtain the pressure-sensitive adhesive, other components are added as necessary.

In addition, the modified block copolymer of the present invention can be used in a wide range of areas, and if it is shown as an example, it may be injection-molded products such as footwear and containers, flow-molded products such as toys and household products, packing, sheets and plates. It can be suitably used for pressed molded products and the like. Further, the block copolymer of the present invention can be used in a material whose physical properties are modified by mixing it with other rubber such as SBR or NBR, or plastic such as polystyrene. For example, for rubber use, crepe-like sponge,
Used as a plasticizer for improving impact resistance of general-purpose polystyrene. Further, the block copolymer of the present invention can be used in admixture with asphalt to improve the cold resistance of asphalt.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited as long as the gist of the present invention is not exceeded.

Various measurements were made by the following methods.

The initial adhesive strength was measured by the tilt type ball tack measurement method (tilt angle 30 °, measurement temperature 25 ° C).

The peel strength complies with JIS Z 1522 (180 ° constant speed peel strength test, measurement temperature 25 ° C).

The holding power complies with JIS Z 1524. However, the pasting area was 15 × 10 m / m, and the time until a 1 kg weight fell was measured (measurement temperature 25 ° C.).

The quality of the die-cutting property was judged by the following method. That is, an adhesive is hot-melt coated to a predetermined thickness on a high-quality paper, and after sticking this on a peeling paper, 20
Cut into a size of cm x 4 cm. Next, with a punching blade measuring 1.5 cm × 1.5 cm, only fine paper is cut
10 pieces in 2 rows, 20 pieces in total are punched out, and then, when the excess part is peeled off by hand from the Kurigami, when the number of adhesive labels peeled off is 0 to 1, 2 or 3 pieces In the case of, the Δ mark was added, and in the case of more than 4 sheets, the X mark was added, and the quality of the die-cutting property was judged.

The proportion of styrene chains having a number n of 1 to 4 was based on the method developed by Professor Tanaka of the University of Agriculture and Technology (Proceedings of the Polymer Society of Japan, Vol. 29, No. 7, p. 2055).

The total styrene content was determined by the infrared method. The weight% of the carboxyl group was determined by performing a neutralization titration using a 1/10 normal standard aqueous solution of potassium hydroxide.

Example 1 (1) 4500 g of cyclohexane in a nitrogen atmosphere in an autoclave equipped with a washed and dried stirrer and a jacket,
After charging 1 g of tetrahydrofuran, the internal temperature was set to 50 ° C.

Next, a hexane solution containing 0.4 g of n-butyllithium was added, and then 100 g of styrene was added and polymerization was carried out for 60 minutes.
The polymerization conversion rate of styrene here was 100%.
Then, a mixture of 10 g of styrene and 160 g of isoprene was added and polymerization was carried out for 60 minutes. The polymerization conversion rate of styrene and isoprene here was 100%. Further, this operation was repeated twice. Next, 160 g of isoprene was added and polymerization was carried out until the polymerization conversion rate became 100%. Then, dry carbon dioxide gas was introduced at 3 kg / cm ₂ (gauge pressure) for 60 minutes. Further, 0.27 g of anhydrous hydrochloric acid was added and reacted for 60 minutes.
Then, 10 water was added and the mixture was washed with water for 60 minutes to remove excess hydrochloric acid, and then the water was drained off. Finally add 2,6 to the polymer solution.
After adding -di-tert-butyl-p-cresol, cyclohexane was removed by heating to obtain a block copolymer.

Examples 2 to 8 and Comparative Examples 1 to 8 Polymerization was carried out according to the same formulation as in Example 1 using the predetermined amounts of styrene, isoprene, tetrahydrofuran, carbon dioxide, hydrogen chloride and the like shown in Table 1.

Examples 2,3: 91 parts by weight of bound styrene in part A and 6% respectively.
Example in which the amount of monomer added to the A portion was 7 times Example 5.6: Example in which the total bound styrene was changed to 12% by weight and 22% by weight, respectively. Example 7: Para in place of styrene Example using methyl styrene Comparative Examples 1,2: Examples in which total bound styrene was 4% by weight and 47% by weight, respectively. Comparative Examples 3,4: Without addition of tetrahydrofuran and in large excess (6.5 g / 100 g monomer). Comparative Example 5: Example in which the number of times of addition of the monomer in the B portion was 20 times. Comparative Example 6.7: 40% by weight and 9% of the bound styrene in the A portion, respectively.
Example of 9 wt% Comparative Example 8: Example without Carbon Dioxide Gas and Hydrogen Chloride Treatment Table 2 shows the structures of the block copolymers obtained in each Example and Comparative Example.

Each of the block copolymers thus obtained was 100
Parts and tackifier synthetic polyterpene resin "Quinton D-10
0 "(manufactured by Zeon Corporation), 20 parts softener naphthenic process oil" Diana Process Oil NM-280 "(manufactured by Idemitsu Kosan Co., Ltd.) and phenol anti-aging agent" Nokurac NS-6 ". 3 parts (manufactured by Ouchi Shinko Chemical Co., Ltd.) were mixed to prepare a pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet was formed therefrom, and the items in Table 3 were examined.

As is clear from the results shown in Table 3, those of Examples 1 to 8 are superior to those of Comparative Examples 1 to 8 in terms of the balance between initial adhesive strength, peel strength and die-cutting property.

Further, FIG. 1 shows a styrene chain distribution curve of the block copolymer of Example 1 by the oxidative decomposition method using ozone by the method of Tanaka et al.

The results are shown in Table 4.

Example 9 and Comparative Example 9 28% by weight of the block copolymer of Example 8 and 72% by weight of polystyrene "Topolex 525" (manufactured by Mitsui Toatsu Co., Ltd.)
A mixed composition of and was produced to obtain a sheet having a thickness of 0.2 mm at a molding temperature of 180 ° C., and the physical properties of the sheet were examined. For comparison, the physical properties of the above polystyrene alone were examined. The results are shown in Table 5.

It is clear from Table 5 that the block copolymer according to the present invention has excellent properties as a molding resin.

[Brief description of drawings]

FIG. 1 shows the styrene chain distribution curve of the copolymer of Example 1 obtained by the oxidative decomposition method with ozone.

(72) Inventor Susumu Sugawara 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (72) Masatoshi Torii 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Japan Within Rubber Co., Ltd. (72) Inventor Mikio Takeuchi 2-11-24 Tsukiji, Chuo-ku, Tokyo Within Japan Synthetic Rubber Co., Ltd.

Claims (1)

[Claims] 1. The content of the vinyl aromatic compound is 5% by weight.
40 wt% or more and 40 wt% or less, and further satisfy the following conditions (a) to (c): carboxy-modified block copolymer: Condition (a) General formula ABCOOH or general formula B- A-COOH (In the formula, A is a block of a vinyl aromatic compound polymer and contains 50 to 97% by weight of all vinyl aromatic compounds, and B is a copolymer of a vinyl aromatic compound mainly containing a conjugated diene compound. A polymer block having a taper block in which the proportion of the vinyl aromatic compound gradually increases in the direction of the carboxy group); Condition (b) In the vinyl aromatic compound, 4 or less monomer units are included. The ratio of the vinyl aromatic compounds constituting the continuous chain to the total vinyl aromatic compounds is 5 to 30% by weight;
And Condition (c) The weight average molecular weight of the copolymer is 10,000 to 500,000.