JPH0330631B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pressure-sensitive adhesive composition with improved initial adhesive strength, and more specifically, the present invention relates to a pressure-sensitive adhesive composition with improved initial adhesive strength, and more particularly, a copolymer resin of isoprene, aromatic monoolefin, and aliphatic monoolefin is blended with a conjugated diene rubber as a tackifier. The present invention relates to a novel pressure-sensitive adhesive composition comprising: Adhesives whose basic components are a rubber component and a tackifier are widely used in the fields of adhesive tapes such as cellophane tape and kraft tape, and adhesive labels such as price display labels. Conventionally, conjugated diene rubbers such as natural rubber, synthetic polyisoprene rubber, and styrene-butadiene rubber (hereinafter abbreviated as SBR) have been used as rubber components, and polyterpene resins and tackifiers have been used as tackifiers.
Natural resins such as rosin ester and petroleum-based hydrocarbon resins are used, but using petroleum-based hydrocarbon resins as tackifying resins, which are relatively cheap and easily available, is more effective than using natural resins. A major problem was that they generally had poor performance, particularly poor initial adhesive strength. This tendency is particularly pronounced when SBR is used as the base elastomer, making it virtually impossible to use it as a tackifier for SBR-based adhesives. The inventors of the present invention conducted studies to solve the drawbacks of the prior art, and as a result found that it is effective to use a specific hydrocarbon resin, and completed the present invention. An object of the present invention is to provide a pressure-sensitive adhesive composition with excellent initial adhesive strength, and another object of the present invention is to provide a pressure-sensitive adhesive composition with an excellent balance of initial adhesive strength, adhesive strength, and holding power. . These objects of the present invention are as follows: (A) conjugated diene rubber as a tackifier (B) 25 to 70% by weight of isoprene;
Blending a hydrocarbon resin obtained by cationically polymerizing a monomer mixture consisting of 25 to 70% by weight of aromatic monoolefin and 5 to 40% by weight of aliphatic monoolefin in the presence of an aluminum halide catalyst, This is achieved by forming an adhesive composition. In the present invention, 25 to 70% by weight of isoprene,
Preferably 30 to 65% by weight, aromatic monoolefin 25 to 70% by weight, preferably 30 to 65% by weight, aliphatic monoolefin 5 to 40% by weight, preferably 10
Solid hydrocarbon resin obtained by cationic polymerization of a monomer mixture consisting of ~30% by weight in the presence of an aluminum halide catalyst, preferably with a softening point of ~50
A hydrocarbon resin at 120°C is used as a tackifier. The usage ratio of isoprene is as mentioned above,
If the ratio exceeds 70% by weight, high molecular weight polymers are likely to be produced that have a negative impact on compatibility with the conjugated diene rubber, and if this ratio is less than 25% by weight, a large amount of liquid low molecular weight polymer will be produced during the polymerization reaction. as a by-product, and the softening point of the resin drops significantly. On the other hand, examples of aromatic monoolefins include styrene, α-methylstyrene, vinyltoluene, and isopropenyltoluene, among which those having 10 or less carbon atoms are preferred. The proportion of the aromatic monoolefin in the monomer mixture is as described above, and outside this range, the compatibility with the conjugated diene rubber, particularly SBR, decreases. In addition, examples of aliphatic monoolefin include isobutylene, butene-1, cis-butene-2, trans-butene-2, pentene-1, cis-pentene-2, trans-pentene-2, 2-methyl-butene-1 , 2-methyl-butene-2, diisobutylene, cyclopentene, cyclohexene, etc., and those having 4 to 8 carbon atoms are particularly preferred. By using such aliphatic monoolefin, the compatibility with the conjugated diene rubber is improved and the initial adhesion strength is also improved, but the ratio is 40% by weight.
If it exceeds this, the resin yield will decrease, a large amount of liquid low molecular weight polymer will be produced as a by-product, and the softening point of the resin will drop significantly. Furthermore, other polymerizable components such as 1.3-butadiene, 1.3-pentadiene, cyclopentadiene, dicyclopentadiene, methylcyclopentadiene, indene, and methylindene may be included as long as they do not essentially impede the effects of the present invention. However, it is desirable that the content thereof be as small as possible. The hydrocarbon resin used in the present invention can be obtained by cationically polymerizing such a monomer mixture in the presence of an aluminum halide catalyst according to a conventional method. Examples of catalysts used include aluminum halides such as aluminum chloride, aluminum bromide, etc., together with hydrochloric acid,
Examples include complexes comprising halogenated hydrocarbons, aromatic hydrocarbons, and other ligands. In the present invention, it is an essential requirement to use such an aluminum halide catalyst, and the effects of the present invention can also be obtained even if a boron halide catalyst, which is commonly used in the production of aromatic petroleum resins, is used. I can't. Further, as the diluent, any of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons can be effectively used, but aromatic hydrocarbons are particularly preferred. This solvent is usually used in an amount of 20 to 1000 parts by weight, preferably 50 to 500 parts by weight, per 100 parts by weight of monomer. Polymerization is usually carried out at a temperature of 0 to 120°C, preferably 20 to 100°C, and the pressure of the reaction system may be above or below atmospheric pressure. Reaction times generally can vary from a few seconds to 12 hours or more. After the polymerization is completed, the desired hydrocarbon resin is obtained by processing and drying according to a conventional method. Examples of the conjugated diene rubber that is the base polymer of the composition of the present invention include natural rubber, SBR, synthetic polyisobutylene rubber, and polybutadiene rubber, and those having a Mooney viscosity of 20 to 100, preferably 30 to 80 are usually used. It will be done. Among these, natural rubber and SBR are preferred, and in the case of SBR, the amount of bound styrene is usually 15 to 55%, preferably 20%.
A random copolymer having a number average molecular weight of 100,000 to 1,000,000, preferably 200,000 to 500,000 is used. The blending ratio of the base elastomer and hydrocarbon resin can vary depending on the desired use of the adhesive, but generally 30 to 250 parts by weight, preferably 40 to 150 parts by weight of the hydrocarbon resin is blended to 100 parts by weight of the base elastomer. be done. Furthermore, in the present invention, in addition to the conjugated diene rubber and the hydrocarbon resin, other base elastomers and tackifier resins can be used in combination as long as they do not essentially impede the effects of the present invention. It is also possible to add softeners, antioxidants, fillers, etc. The compositions of the invention are manufactured according to any method. For example, a pressure-sensitive adhesive solution can be prepared by stirring and mixing each component in the presence of a solvent such as toluene, or a pressure-sensitive adhesive emulsion can be prepared by stirring and mixing a hydrocarbon resin that has been previously emulsified with rubber latex. These adhesive solutions or adhesive emulsions are usually uniformly applied to the desired substrate using a coating machine, dried in an oven, and then rolled up to produce various adhesive tapes or adhesive label products. be done. The present invention will be explained in more detail with reference to Examples below. Note that all parts and percentages in Reference Examples and Examples are based on weight. Reference Example 1 After charging 100 parts of benzene and 1.2 parts of aluminum chloride or 2.0 parts of boron trifluoride diethyl etherate, gradually add 100 parts of a monomer mixture having the composition shown in Table 1 and copolymerize at 65°C. Various hydrocarbon resins were produced by this process. The softening point was measured according to the ring and ball method specified in JIS K-2531, and the hue was measured according to Gardner chromaticity specified in ASTM D1544-63T. Results first
Shown in the table.

[Table] Example 1 SBR (Nipole 1502, bound styrene content 23.5%,
Mooney viscosity 52, manufactured by Nippon Zeon Co., Ltd.) 100 parts, tackifier resin 60 parts, naphthenic process oil (Cielflex 371, manufactured by Ciel Chemical Co., Ltd.) 10 parts, and antioxidant 1 part were dissolved and mixed in toluene and non-volatile. An adhesive solution with a concentration of 20% was prepared. Next, apply this solution onto a 25μ thick polyester film with a glue thickness of 25μ.
An adhesive tape was prepared by coating the adhesive tape so that the initial adhesion strength, adhesion strength, and holding power of the adhesive tape were measured. As the tackifier, we used not only the hydrocarbon resin obtained in Reference Example 1 (the alpha abets of the tackifier in Table 2 correspond to those in Table 1), but also conventional conjugated diene resins for comparison. Various tackifier resins that are used industrially as tackifiers for pressure-sensitive adhesives using rubber as a base elastomer were simultaneously evaluated. The initial adhesive strength is based on JIS Z-0237 at 23℃.
Attach a 10 cm long adhesive tape with the adhesive side up to the slope of a stainless steel plate with a 30 degree inclination angle, and tape 30 different sizes from 3/32 inch to 1 inch in diameter from a position 10 cm above the slope. The size of the largest diameter ball that stops on the adhesive tape when rolled at an initial speed of 0 is the size of the ball, and the adhesive strength is based on JIS Z-0237. The adhesive tape was attached to a 10 mm x 100 mm length and measured by peeling it in a 180 degree direction at a speed of 200 mm/min at 23°C. Attach adhesive tape so that the area of ×10 mm touches each other, and
The time required for the adhesive tape to fall off from the stainless steel plate was measured under a load of 1 kg.
The results are shown in Table 2.

[Table] From the results, it can be seen that the pressure-sensitive adhesive of the present invention exhibits excellent initial adhesive strength and also has an excellent balance of initial adhesive strength, adhesive strength, and holding power. On the other hand, compositions obtained using ordinary aliphatic hydrocarbon resins as tackifiers show almost no performance as adhesives, and adhesive compositions obtained using polyterpene resins also have extremely low initial adhesion. It only shows force and adhesion. Although a pressure-sensitive adhesive composition obtained using a rosin ester exhibits a certain degree of initial adhesive strength, it is inferior to the pressure-sensitive adhesive composition according to the present invention in terms of the balance between holding power and adhesive strength. Example 2 SBR (Nipole) was used as the base elastomer.
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that a mixture of 50 parts of 1502) and natural rubber (Pale Clave, Mooney viscosity 60) was used, and its pressure-sensitive adhesive properties were evaluated. The results are shown in Table 3. From the results in Table 3, it can be seen that the SBR/natural rubber combination system also has excellent initial adhesion strength.
It can be seen that it also shows excellent performance in terms of holding power. Example 3 An adhesive composition was prepared in the same manner as in Example 1 except that natural rubber (Paleclave, Mooney viscosity 6) was used as the base elastomer, and its adhesive properties were evaluated. In addition, the holding power is 40
Measured at °C. The results are shown in Table 4. From the results in Table 4, it can be seen that excellent performance is also exhibited in the case of natural rubber.

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Claims (1)

[Claims] 1 (A) Conjugated diene rubber as a tackifier (B) 25-70% by weight of isoprene, aromatic monoolefin
25-70% by weight and 5-40% aliphatic monoolefin
An adhesive composition comprising a hydrocarbon resin obtained by cationically polymerizing a monomer mixture consisting of % by weight in the presence of an aluminum halide catalyst.