JPH11349717A - Damping resin foam and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject foam excellent in weather and water resistances, elongation and flexibility and useful as a flooring material, etc. by mixing a triblock copolymer with a polyethylene-based resin and thermally expanding the resultant mixture. SOLUTION: This foam is produced by adding a foaming agent (e.g. azodicarbonamide) and a cross-linking agent (e.g. dicumyl peroxide) to a mixture of (A) 70-95 pts.wt. of a triblock copolymer in which (i) polystyrene is bound to (ii) a vinyl-polyisoprene with (B) 30-5 pts.wt. of a polyethylene-based resin, kneading the resultant mixture, filling the kneaded mixture in a closed type metal mold, heating the filled mixture under a pressure, then decompressing and expanding the mixture. The heating is preferably carried out, e.g. at 130-170 deg.C for about 10-50 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock-absorbing vibration-damping resin foam used for flooring materials, athletic shoes, sports equipment pads, and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Vibration damping foams are soft and have a large vibration damping ability, so that sporting goods such as athletic shoes and pads, flooring materials, Sunday goods, etc. are used for shock absorption and vibration absorption. Used to The vibration damping property of the polymer is based on the phenomenon that the polymer exhibits a viscoelastic behavior near the glass transition temperature or a secondary transition temperature lower than the glass transition temperature, the internal friction is large, and the vibration damping ability is large. Conventionally, a polyurethane foam damping material has been used. For example, a damping material used for a ceiling, a floor, and the like having both a damping performance and a sound absorbing performance by using a specific amount of a foam stabilizer when producing a flexible polyurethane foam. (Japanese Patent Publication No. 5-8209), a soundproofing / damping foam obtained by foaming an organic polyisocyanate and a specific polyol in the presence of a foaming agent, a catalyst, a foam stabilizer and a fluid having a plasticizing effect. (Tokuhei 7-25
No. 863) has been proposed. These vibration damping materials of urethane foam have excellent vibration damping properties, but have disadvantages in that they are inferior in weather resistance and water resistance. In addition, rubber-based damping foams have been proposed, for example, 1.2-polybutadiene foam having excellent damping performance, a low restoration speed, excellent shock absorption, and good compatibility with a thermoplastic resin. Production method (JP-A-7-62130), cross-linked foaming of a molded article of a mixture of 1,2-polybutadiene having damping properties and a vinyl bond-polyisoprene-polystyrene block copolymer having damping properties A vibration damping resin foam (Japanese Patent Application Laid-Open No. 8-208869) has been proposed.

[0003]

However, the above-mentioned prior art 1,2-polybutadiene-based foam is not suitable for 1,2-polybutadiene foam.
Polybutadiene has double bond carbon of vinyl group in the side chain, so it is easy to crosslink by bonding between side chains or between side chain and main chain, thereby hardening rapidly, resulting in insufficient elongation and flexibility That was a drawback. Accordingly, it is an object of the present invention to provide a vibration-damping resin foam excellent in weather resistance, water resistance, elongation and flexibility, and a method for producing the same, which overcomes the drawbacks of the prior art.

[0004]

According to the present invention, in order to achieve the above object, a vibration damping resin foam of the present invention comprises a triblock copolymer in which polystyrene and vinyl-polyisoprene are bonded to a polyethylene-based resin. It is characterized in that it is mixed with a resin and heated and foamed to form a vibration-damping resin foam. In the vibration damping resin foam of the present invention, the triblock copolymer in which polystyrene and vinyl-polyisoprene are bonded is preferably 70 to 95 parts by weight, and the polyethylene resin is preferably 30 to 5 parts by weight. When the amount of the triblock copolymer is less than 70 parts by weight, the vibration damping property is insufficient, and
If the amount exceeds the weight part, the kneading work is difficult. The method for producing a vibration-damping resin foam of the present invention comprises the steps of: adding a foaming agent and a crosslinking agent to a mixture of a triblock copolymer in which polystyrene and vinyl-polyisoprene are combined with a polyethylene-based resin; kneading the mixture; It is characterized in that it is filled in a mold, heated under pressure and then depressurized to foam. In the production method of the present invention,
For the same reason as above, the triblock copolymer in which polystyrene and vinyl-polyisoprene are bonded is 70-95.
Parts by weight are preferred, and the content of the polyethylene resin is preferably 30 to 5 parts by weight.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The triblock copolymer comprising polystyrene and vinyl-polyisoprene used in the present invention has a glass transition temperature (Tg or ta) at room temperature.
nδ), and exhibits high damping performance in this temperature range. The polyethylene resin used in the present invention acts as a binder for the triblock copolymer, and includes a high-pressure low-density polyethylene, a low-pressure low-density polyethylene, a medium-density polyethylene, a high-density polyethylene, an ethylene-vinyl acetate copolymer, and a metallocene. A polyethylene resin or the like polymerized using a catalyst can be used.

Hereinafter, a preferred embodiment of the method for producing a vibration-damping resin foam according to the present invention will be specifically described. First, a foaming agent, a crosslinking agent, and, if necessary, a foaming aid, a filler, a pigment, and the like are added to a mixture of polystyrene and vinyl-polyisoprene. Knead with. The cross-linking agent referred to in the present invention is a resin having a decomposition temperature at least equal to the flow start temperature of the resin, and is decomposed by heating to generate free radicals to form cross-links between or within the molecules. An organic peroxide which is a radical generator to be generated, for example, dicumyl peroxide, 1,1-ditert-butylperoxy-
3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, 2,5-dimethyl-2,5-di-tert-butyl peroxyhexyne, α, α-di-tert-butyl There are butyl peroxyisopropylbenzene, tertiary butyl peroxyketone, tertiary butyl peroxybenzoate, and the like, but the most appropriate organic peroxide must be selected depending on the resin used at that time. The blowing agent that can be used in the present invention is a chemical blowing agent having a decomposition temperature equal to or higher than the melting temperature of the polyethylene resin. For example, azo compounds such as azodicarbonamide and barium azodicarboxylate: nitroso compounds such as dinitroso Pentamethylenetetramine, trinitrotrimethyltriamine and the like; hydrazide compounds such as p, p'-oxybisbenzenesulfonylhydrazide; and sulfonylsemicarbazide compounds such as p, p'-oxybisbenzenesulfonylsemicarbazide and toluenesulfonylsemi And carbazide. In the present invention, a foaming aid can be added according to the type of the foaming agent. Examples of the foaming aid include compounds mainly containing urea, metal oxides such as zinc oxide and lead oxide, compounds mainly containing salicylic acid, stearic acid and the like, that is, higher fatty acids and metal compounds of higher fatty acids. In the present invention, for the purpose of improving the physical properties of the composition to be used or lowering the price, a compounding agent (filler) that does not significantly affect the cross-linking, such as zinc oxide, titanium oxide, calcium oxide, magnesium oxide, oxide Metal oxides such as silicon, carbonates such as magnesium carbonate and calcium carbonate, or fibrous materials such as pulp, or various dyes, pigments and fluorescent materials, and other conventional rubber compounding agents can be added as necessary. .
The foamable crosslinkable composition obtained by kneading as described above is charged into a closed mold, and is pressurized with a press at 130 to 170 ° C, preferably 140 to 170 ° C, depending on the type of the resin and the crosslinker.
After heating at 160 ° C., preferably for 10 to 50 minutes, the pressure is released to obtain a vibration-damping resin foam. Alternatively, after heating in a closed mold under pressure to partially decompose the foaming agent and then depressurizing to obtain an intermediate foam, the obtained intermediate under normal pressure, for example,
A conventionally known foaming method such as a two-stage foaming method for obtaining a final foam by heating in a foaming machine by jacket heating or heating in a heating medium bath can be applied. The heating temperature under normal pressure is
The temperature is set in the range of 140 to 210 ° C., preferably 150 to 190 ° C., depending on the type of resin used. The heating time is
Preferably 10 to 90 minutes, more preferably 20 to 70 minutes
Minutes. The resilience of the damping foam obtained in the present invention is measured by a test method specified in JIS K6401. Specifically, using a 5 / 8-in parallel sphere, 460 m
It is expressed as a value (percentage) obtained by dividing the reaction distance at the time of natural drop from the height of m by the drop distance. In the present invention, a damping resin foam having an expansion ratio of 3 to 15 times produced by a one-stage pressure foaming method has excellent damping properties and is particularly useful.

[0007]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples. Example 1 A triblock copolymer in which polystyrene and vinyl-polyisoprene are bonded (trade name “Hybler HVS-3”,
Styrene content 20%, vinyl bond content 55%, glass transition temperature -19 ° C, 90 parts by weight, manufactured by Kuraray Co., Ltd., low-density polyethylene (trade name “Novatech YF-30”),
MFR 1.1 g / 10 min, density 0.920 g / cm 3,
A composition comprising 10 parts by weight of Nippon Polychem Co., Ltd., 2.0 parts by weight of azodicarbonamide, 1.4 parts by weight of dicumyl peroxide, 2.0 parts by weight of zinc white and 0.5 parts by weight of zinc stearate was prepared. Kneading with a mixing roll at 85 ° C, a mold in a press heated to 155 ° C (195x
380 x 28 mm), the mixture was heated under pressure for 35 minutes, and then depressurized to obtain a vibration-damping resin foam. The obtained foam had an apparent density of 0.149 g / cm3 and an elastic modulus of 6.5%, and was excellent in vibration damping properties. Example 2 A vibration-damping resin foam was obtained in the same manner as in Example 1 except that the amount of azodicarbonamide was changed to 4.0 parts by weight. The obtained foam had an apparent density of 0.089 g / cm3 and an elastic modulus of 18.5%.
And excellent vibration damping properties. Comparative Example 1 In Example 2, except that the triblock copolymer was changed to 50 parts by weight and the low-density polyethylene was changed to 50 parts by weight.
A foam was obtained under the same composition and under the same conditions as in Example 2. The obtained foam had an apparent density of 0.089 g / cm3 and an elastic modulus of 40%, and was inferior in vibration damping properties.

[0008]

As described above, according to the present invention, since a triblock copolymer in which polystyrene and vinyl-polyisoprene are bonded is used, the glass transition temperature (T
g or tan δ), exhibiting high damping performance in this temperature range, and the resulting foam is excellent in damping properties, elongation, flexibility, weather resistance, water resistance, sound insulation, It is useful for sports equipment such as athletic shoes, flooring materials and the like.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // (C08L 53/00 23:04) B29K 96:04 105: 04 105: 24

Claims (4)

[Claims] 1. A vibration damping resin foam obtained by mixing a triblock copolymer in which polystyrene and vinyl-polyisoprene are combined with a polyethylene resin and foaming the mixture by heating. 2. The vibration damping resin foam according to claim 1, which is a mixture of 70 to 95 parts by weight of a triblock copolymer in which polystyrene and vinyl-polyisoprene are combined and 30 to 5 parts by weight of a polyethylene resin. 3. A foaming agent and a crosslinking agent are added to a mixture of a triblock copolymer in which polystyrene and vinyl-polyisoprene are combined with a polyethylene resin, kneaded, filled in a closed mold, and heated under pressure. A method for producing a vibration damping resin foam which is depressurized and then foamed. 4. A foaming agent and a cross-linking agent are added to a mixture of 70 to 95 parts by weight of a triblock copolymer in which polystyrene and vinyl-polyisoprene are combined and 30 to 5 parts by weight of a polyethylene resin, and the mixture is kneaded. A method for producing a vibration-damping resin foam which is filled in a mold, heated under pressure, and then decompressed and foamed.