JPS6219471B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pressure-sensitive adhesive composition, and particularly to a pressure-sensitive adhesive composition with excellent adhesive properties, which contains as main components a rubber containing a vinyl aromatic compound-conjugated diene compound block copolymer, a tackifier, and a softener. Traditionally, natural rubber has been used as a rubber-based adhesive substance.
Adhesive formulations containing recycled rubber, styrene-butadiene rubber, styrene-butadiene block copolymer rubber, etc. are known. Among these, in particular, vinyl aromatic compound-conjugated diene compound block copolymer elastomers have a high peel strength and can be applied by hot melt, so they are being used in various fields. There are disadvantages when using it: (1) If adhered to rough surfaces such as paper or wood, it will self-peel after about a week. (2) Adhesives are usually used at temperatures between -10 and 60°C, but the adhesion and tack are insufficient for an adhesive to be effective at low temperatures, and the holding power is insufficient for an adhesive to be effective at high temperatures. is in short supply. As a means to improve these drawbacks, there is a method of adding aromatic oil for (1) above, but using this is not preferable as it reduces high temperature holding power, and adding a resin with a high melting point also reduces low temperature retention. Tatsuk becomes low. Regarding (2) above, there is a method to improve the temperature range by reducing the amount of resin as a tackifier and using a large amount of naphthenic oil that is compatible with the rubber layer, but this method does not improve the high temperature rupture strength. However, a portion of the naphthenic oil migrates to the adherend and the peeling force and holding force decrease, so these problems cannot be solved. Generally, the pressure-sensitive adhesive composition must satisfy the following conditions within the temperature range in which it is used. (1) The adhesive composition itself has a high adhesive strength to the adherend, (2) the adhesive composition itself has a low modulus, and (3) the adhesive composition itself has a high adhesive strength to the adherend surface. (4) The pressure-sensitive adhesive composition itself should not cause a certain degree of permanent deformation on rough surfaces, thereby preventing self-peeling due to the memory effect of the pressure-sensitive adhesive. It has a breaking strength that is sufficiently stronger than the adhesive strength and does not cause cohesive failure when peeled off. However, something that satisfies these conditions,
There is no such thing, and its development is requested. The present invention provides a pressure-sensitive adhesive composition that solves these problems, and in particular contains a vinyl aromatic compound-conjugated diene compound block copolymer that has specific bulk properties, resulting in high adhesive strength and low modulus. The present invention provides an adhesive composition that does not cause self-peeling or cohesive failure during peeling. That is, the present invention provides a vinyl aromatic compound-conjugated diene compound block copolymer elastomer having a random or tapered copolymer portion between a block mainly consisting of a vinyl aromatic compound and a block mainly consisting of a conjugated diene compound. containing rubber, tackifier, and softener, and has a breaking strength of 7 to 50 kg/cm ² at room temperature.
An adhesive that has a hardness at room temperature of 10 or less, a hardness of 3 or less after 30 seconds, a hardness of 35 or less at -10°C, and a hardness of 10 or less after 30 seconds when measured with a spring-type hardness meter. It is a composition. First, the vinyl aromatic compound-conjugated diene compound block copolymer elastomer (hereinafter referred to as block copolymer) in the present invention will be explained. Various types of block copolymers can be used, and examples of their structures include the following. (1) A-C-B-C-A (2) A-C-B-A (3) A-C-B-C-A-C-B-C-A (4) (A-C- B) - _o Represents a combined block. Note that X in structure (4) is a coupling agent that couples the A-C-B- block,
n is 3-20. (A-C-B) _-oX is a star block copolymer. Vinyl aromatic compounds used as the main element constituting A include styrene, α-methylstyrene, and vinyltoluene, and conjugated diene compounds used as the main element constituting B include butadiene, isoprene, etc. . The preferred molecular weight range is 30,000 to 200,000 for linear block copolymers, and 25,000 to 150,000 for star block copolymers as the branch molecular weight. The proportion of the vinyl aromatic compound in the block copolymer used in the present invention is preferably 20 to 55%, and the solubility parameter that governs the compatibility between the vinyl aromatic compound and the conjugated diene compound, and the type and amount of the compound. It can be determined as appropriate. The rubber contained in the adhesive composition of the present invention may be a vinyl aromatic compound-conjugated diene compound block copolymer elastomer alone, or a combination of a small amount of other block polymers, natural rubber, styrene-butadiene rubber, and various other synthetic rubbers. It is a blend and has a bulk physical property of breaking strength of 80Kg/cm ²
It is preferable that it is above. If it is less than 80 kg/cm ² , the breaking strength of the composition is low, and cohesive failure is likely to occur in the adhesive layer, and the holding power particularly at high temperatures is likely to decrease.
Therefore, A-C-B-A-C with B at the end of the molecule
A block copolymer having a structure like -B is not necessarily suitable for the purpose of the present invention. Examples of the tackifier resin include commonly used rosin resins, polyterpene resins, C ₅ petroleum resins, C ₉ petroleum resins, dicyclopentadiene petroleum resins, coumaron-indene resins, and the like. Although the tackifier resin may vary slightly depending on the type of resin and the molecular weight, it is usually 20 parts per 100 parts of the block copolymer or the total rubber component containing it.
Parts to 200 parts are used. If the amount is less than 20 parts, the tackifying effect will be small, and if it is more than 200 parts, the hardness will increase and the tackiness will decrease. Particularly preferred range is 60~
There are 130 copies. Examples of the softener include various commonly used naphthenic and aromatic process oils, as well as liquid oligomer resins such as butadiene oligomers, isoprene oligomers, and liquid tackifier resins. The softener is usually used in an amount of 10 to 150 parts per 100 parts of the block copolymer or the total rubber component containing it, although it varies slightly depending on the type of softener, molecular weight, etc. If it is less than 10 parts, the adhesiveness will be insufficient, or
If it exceeds 150 parts, the holding power tends to decrease. A particularly preferred range is 30 to 80 parts. As a result of various studies, it has been found that an adhesive composition containing such a rubber, a tackifier resin, and a softener must have the following physical properties. (1) Breaking strength of the blend: The breaking strength of the blend is 7 Kg/cm ² or more, preferably 15 Kg/cm ² to 50 Kg/cm ² at 25°C. If the breaking strength is low, the holding force will be reduced. Also, the higher the breaking strength, the better, but usually
If the weight exceeds 50Kg/ ^cm2 , the modulus will increase accordingly, resulting in a lack of tack. (2) Modulus and ice strain of a compound: The modulus of a compound can be easily measured by hardness. JIS K-6301 spring type A hardness at 20℃, instantaneous value of 10 or less, preferably 5 or less, which indicates 3 or less after 30 seconds, and JIS K-6301 at -10℃
Spring type A type hardness is 35 or less and the value after 30 seconds is
Those showing a value of 10 or less are preferred. The instantaneous value (initial value) of hardness has a great influence on the wetting characteristics for rough surfaces, and a low value is desirable. When measuring the stress-strain of a JIS K-6301 spring type A compound with a hardness of 35 or more, the yield point is indicated by a small amount of strain. Such materials are difficult to adhere to rough surfaces such as cardboard with normal back pressure (such as finger pressure). Furthermore, the difference between the value after 30 seconds and the instantaneous value represents the permanent strain, and the higher the modulus, the greater the permanent strain is required. In other words, the power to recover memory is stronger as the modulus is larger, and if the modulus is low from the beginning, even if the permanent distortion is not so large, memory recovery will be less. Therefore, the value after 30 seconds at 20°C is less than 3 and 10 at -10°C.
The following are desirable. (3) Peeling force: Peeling force often depends on the characteristics of the adherend, and is not the purpose of the present invention;
Of course, it is necessary to have a value that is at least suitable for the intended use, and sufficient care must be taken to prevent the peel strength from decreasing due to bleeding of low-molecular substances from the compound. The breaking strength and curing of the formulation are measured by molding the adhesive composition and removing the tack by dusting with flour to make it easier to handle. Example 1 In a glass autoclave under a nitrogen atmosphere, 1.
70 g of 3-butane diene and 30 g of styrene were dissolved in 1 cyclohexane, and 3.3 x 10 ^-3 atomic equivalents of a butadiene oligomer dilithium catalyst was added as active lithium, followed by polymerization at a temperature of 60°C. After color development with styryl anions, 16.7 g of styrene was further added and polymerized at the same temperature for 1 hour. After the polymerization was completed, the mixture was deactivated with a small amount of water, and 1 g of 2,6-ditertiarybutyl-4-methylphenol was added as a stabilizer. This liquid was steam-stripped and dried to obtain an A-C-B-C-A type block copolymer having a styrene content of 40% by weight. The thus obtained block copolymer (breaking strength 190 kg/cm ² ) was kneaded with the tackifier and process oil shown in Table 1 in a kneader heated to 160°C. The resulting adhesive composition was applied to a 25μ polyester film to a thickness of 50μ to make an adhesive tape, and ball tack, peel strength, and holding power were measured, as well as a low temperature adhesion test and a practical test using a cardboard box. In addition, tensile strength and hardness were measured as mechanical properties of the adhesive composition. The results are shown in Table 2. The ball tack is based on the inclined ball tack measurement method (equipment, manufactured by Uejima Seisakusho), in which a 10cm adhesive tape surface is fixed on a 30° slope in a thermostatic room at 20°C and 65% humidity, and a run-up distance of 10cm is measured from 1/32 inch. 1
Stainless steel balls of 32 different sizes up to inches were rolled and the ball with the largest diameter stopped on adhesive tape. Peel force is 5.7 of JIS Z-1522
Measurements were made on stainless steel and cardboard (K liner) as test plates according to . The holding force was measured by attaching the test piece to the test plate in an area of 25 mm x 25 mm, and bending the inner surface of the unattached test piece inward and attaching it. Press the test piece back and forth once on top of the test piece at 60±2℃.
After leaving it for 60 minutes, fix one end of the test plate with a clamp at the same temperature so that the test piece hangs vertically.
Apply a load of 1000 ± 10g uniformly to the loose part of the tape and measure the time it takes for the load to fall, or remove the load after 60 minutes and comply with JIS B-7507 (calipers).
The length of the deviation was measured using a 0.05 mm scale. The test plate is a stainless steel plate (JIS Z-1522 5
-7 test plate) and cardboard (K-liner), three points each were measured, and the average value of the three points was determined. Low-temperature adhesion test was performed using adhesive tape 25 in a -10°C constant temperature room.
The sample was attached to a cardboard box (K-liner) with a fixed mm width and reciprocatingly pressed onto the test piece using a roller covered with a 2000±50 g rubber layer. Then, one end of the adhesive tape was gently pulled off by hand and its adhesiveness was observed. In a practical test using a cardboard box, a cardboard box (20cm x 11cm x 11cm) filled with crumpled newspaper was fixed with adhesive tape cut to a width of 25cm20.
The adhesive tape was left in a constant temperature room at 65% humidity and the adhesive tape peeled off after 7 days was expressed as a percentage. The mechanical properties of the adhesive composition were determined by pressing it to a thickness of 2 mm at 160°C, removing the tack with powder, and measuring the tensile strength by punching out a JIS K63013 dumbbell shape at a tensile speed of 300 mm/min. Four 2 mm sheets were stacked together and measured using a JIS K-6301 spring type A type measuring device.

【table】

[Table] The following was found from Example 1. A-C-B-
Even if a C-AA type block primer was used, the composition containing 120 ^PHR of process oil as in Comparative Experiment 1,
Bleed development appears, peel strength of tape physical properties,
It impairs the holding power and practical physical properties of the cardboard box. Further, as in Comparative Experiment 2, the composition to which 120 ^PHR of the tackifier was added significantly increased the hardness at low temperatures, deteriorated the low-temperature adhesion, and at the same time decreased the holding power. It can be seen that a formulation having the tensile strength and hardness of the pressure-sensitive adhesive composition as shown in Experiment Nos. 1, 2 and 3 of the present invention is required. Also, even if a softening agent is used only in liquid polybutadiene instead of the normally used process oil, the A-C-B-C-A type block copolymer having a tapered copolymer can be heated at 20°C. Greatly improves low-temperature adhesion without damaging adhesive tape physical properties. Example 2 Adding 1.65×10 ^-3 atomic equivalent of Sec-butyllithium as active lithium to 1 cyclohexane
19 g of styrene was added and polymerized at 60°C. After polymerization is almost complete, 69 g of 1,3-butadiene and 27 g of styrene are added.
g of the mixture was added and the polymerization continued. After the polymerization was completed, the same treatment as in Example 1 was carried out to obtain an A-C-B-A type block copolymer having a styrene content of 40% by weight. The block copolymers thus obtained were mixed in the same manner as in Example 1 in the following proportions to prepare a pressure-sensitive adhesive composition. Table 3 shows the results of an adhesive property test on this product. Compounding recipe (parts by weight) A-C-B-A type block copolymer 100 _C9 Petroleum resin 80 Rosin acid ester resin 20 Process oil 60 Stabilizer 4

[Table] Comparative example 1 Cyclohexane 1 as a comparison of Examples 1 and 2
Add 1.65 x 10 ^-3 atomic equivalents of Sec-butyllithium as active lithium into the styrene 23 at 60°C.
After almost all of the monomers were polymerized, 69 g of 1,3-butadiene and 23 g of styrene were sequentially added and polymerized in the same manner as in Example 1 to obtain A-B with a styrene content of 40% by weight. -A type A block copolymer was obtained. The thus obtained block copolymer was mixed in the formulation shown in Table 4 in the same manner as in Example 1 to obtain the physical properties shown in Table 5.

【table】

[Table] When an A-B-A type block copolymer containing no tapered copolymer portion is used in an adhesive formulation, the hardness of the adhesive composition is high as shown in Table 5, and the physical properties of the adhesive tape are similar to that of cardboard. Peel force is small. The holding power also peels off at the cardboard interface and falls off immediately. In addition, practical tests using cardboard boxes peeled off in one or two days.
A-C-B- containing a tapered copolymerized portion shown in
The physical properties of the adhesive tape are very inferior to those of the C-A type block copolymer blend. Example 3 70 g of 1,3-butadiene and 30 g of styrene were dissolved in 1 part of cyclohexane, and the butadiene oligomer dilithium catalyst was used as active lithium at 4 x 10 ^-3
Atom equivalents were added and polymerization was carried out at 60°C. After color was developed by styryl anion, another 40 g was added to continue polymerization. After the polymerization was almost completed, the same treatment as in Example 1 was carried out to obtain an A-C-B-C-A type block copolymer having a styrene content of 50% by weight. For comparison, Sec−
Butyllithium as active lithium 2×10 ^-3
Atomic equivalent, cyclohexane 1 plus styrene 35
After almost all of the monomers had been polymerized, 70 g of 1,3-butadiene and 35 g of styrene were sequentially added to obtain an A-B-A type block copolymer having a styrene content of 50% by weight. Thus obtained A-C-B-C-A
The type and A-B-A type block copolymers were mixed as shown in Example 1 in the formulation system shown in Table 6 to obtain the physical properties shown in Table 7.

【table】

[Table] Comparative experiment 6 in which an A-B-A type block copolymer containing no tapered copolymer portion was used in the formulation.
is A-C-B-C- containing a tapered copolymer
Experiment No. of the present invention containing A-type block copolymer.
Compared to No. 5, the hardness of the adhesive composition is higher, and the adhesive tape properties are lower in peel strength, particularly poor peel strength and holding strength against cardboard. In addition, in a practical test using a cardboard box, most of the material came off within one day and self-peeling occurred, making it unusable. Example 4 3.4 x 10 ^-3 atomic equivalents of a butadiene oligomer dillium catalyst as active lithium were added to a solution of 1 cyclohexane containing 79 g of isoprene and polymerized at 60°C for 1.5 hours. Next, 17g of isoprene and 6g of styrene.
g of the mixture was added to continue the polymerization. After color development with styryl anions, 18 g of styrene was further added for polymerization. By the same treatment as in Example 1, an A-C-B-C-A block copolymer having a styrene content of 20% by weight was obtained. For comparison (comparative experiment 7) 1.7×10 ^-3 atomic equivalent of Sec-butylium catalyst as active lithium was added to cyclohexane 1 and styrene 12
g, 96 g of isoprene, and 12 g of styrene were added sequentially at 60°C after the polymerization of each monomer was almost complete to obtain a styrene content of 20 g.
A ABA type block copolymer of % by weight was obtained.
Furthermore, as a comparison (comparative experiment 8), 1.7×10 ^-3 atomic equivalent of Sec-butyllithium catalyst as active lithium was added to cyclohexane 1, and 9 g of styrene was added.
102 g of isoprene and 9 g of styrene were added sequentially at 60°C after the polymerization of each monomer was almost complete, resulting in a styrene content of 15
A ABA type block copolymer of % by weight was obtained. The thus obtained block copolymer was prepared in Example 1.
Mix as shown in Table 8 in the same manner as Table 9.
The physical properties shown in the table were obtained. The terpene resin used as the tackifier is "YS Resin PX-1150" manufactured by Yasushi Oil Co., Ltd.
As the chroman-indene resin, the product name "Kumaron AH" manufactured by Ouchi Shinko Co., Ltd. was used.

【table】

[Table] The A-B-A type block copolymer compositions of Comparative Experiments 7 and 8 had better adhesive tape physical properties than the A-C-B-C-A type block copolymer composition of Experiment 6 of the present invention. The tapered copolymer of the present invention was clearly effective in a practical test using a cardboard box.

Claims (1)

[Claims] 1 Rubber containing a vinyl aromatic compound-conjugated diene compound block copolymer elastomer having a random or tapered copolymer block between a block mainly composed of a vinyl aromatic compound and a block mainly composed of a conjugated diene compound. , containing a tackifier and a softener,
Moreover, the breaking strength at room temperature is 7 to 50Kg/ ^cm2 ,
An adhesive composition having a room temperature hardness of 10 or less, a hardness after 30 seconds of 3 or less, a hardness of 35 or less at -10°C, and a hardness of 10 or less after 30 seconds, as measured with a spring-type hardness meter.