JP3546141B2 - Manufacturing method of vibration damping resin foam - Google Patents

Description

[0001]
TECHNICAL 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]
[Prior art]
Due to its softness and large vibration damping ability, the vibration damping foam is used for sports shoes such as athletic shoes, pads, flooring materials, and Sunday goods for the purpose of shock absorption and vibration absorption. . The vibration damping property of the polymer is based on the phenomenon that the polymer exhibits viscoelastic behavior near the glass transition temperature or near the secondary transition temperature lower than the glass transition temperature, the internal friction increases, and the vibration damping ability increases. Conventionally, a polyurethane foam damping material is used. For example, a damping material used for a ceiling, a floor, etc., 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. (Japanese Patent Publication No. 7-25863) and the like have been proposed. These damping materials of urethane foam have excellent damping properties, but have disadvantages in that they are inferior in weather resistance and water resistance.
[0003]
Further, rubber-based damping foams have been proposed. For example, a 1.2-polybutadiene foam having excellent damping performance, a low restoring speed, excellent shock absorption, and good compatibility with a thermoplastic resin has been proposed. Production method (Japanese Patent Application Laid-Open No. 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 Laid-Open No. 8-208869) has been proposed.
[0004]
[Problems to be solved by the invention]
However, since the 1,2-polybutadiene-based foam of the prior art has a double bond carbon of a vinyl group in a side chain of 1,2-polybutadiene, it is bonded between side chains or between a side chain and a main chain. The disadvantage is that crosslinking is likely to occur, which causes rapid curing, resulting in insufficient elongation and flexibility. Accordingly, an object of the present invention is to provide a vibration-damping resin foam excellent in weather resistance, water resistance, elongation and flexibility, which solves the disadvantages of the prior art, and a method for producing the same.
[0005]
[Means for Solving the Problems]
According to the present invention, in order to achieve the above object, the method for producing a vibration-damping resin foam of the present invention comprises a triblock copolymer in which polystyrene and hydrogenated vinyl-polyisoprene are combined with 70 to 95 parts by weight. This is a production method in which a foaming agent and a crosslinking agent are added to a mixture with 30 to 5 parts by weight of a low-density polyethylene resin, kneaded, filled in a closed mold, heated under pressure, and then depressurized to foam. In the vibration-damping resin foam of the present invention, if the triblock copolymer is less than 70 parts by weight, the vibration-damping property is insufficient, and if it exceeds 95 parts by weight, the kneading operation is difficult.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
The triblock copolymer in which polystyrene and hydrogenated vinyl-polyisoprene are used in the present invention has a glass transition temperature (absorption of Tg or tan δ) in the room temperature range, and has a high vibration suppression in this temperature range. Demonstrate performance. The low-density polyethylene used in the present invention acts as a binder for the triblock copolymer, and high-pressure low-density polyethylene can be used.
[0007]
Hereinafter, preferred embodiments 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 hydrogenated vinyl-polyisoprene, and the resulting mixture is heated to a mixing roll, a pressurized kneader, Knead with an extruder or the like.
[0008]
The cross-linking agent referred to in the present invention has a decomposition temperature of at least the flow start temperature of the resin in the resin, and is decomposed by heating to generate free radicals to form cross-links between or within the molecules. 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-butyl There are peroxyhexane, 2,5-dimethyl-2,5-ditert-butylperoxyhexyne, α, α-di-tert-butylperoxyisopropylbenzene, tert-butylperoxyketone, tert-butyloxybenzoate, etc. Optimal organic peroxide depending on the resin used at that time Must be chosen.
[0009]
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: Nitrosopentamethylenetetramine, trinitrotrimethyltriamine, etc .: p, p'-oxybisbenzenesulfonylhydrazide, etc .: p, p'-oxybisbenzenesulfonyl semicarbazide, toluenesulfonyl of sulfonyl semicarbazide compounds There are semicarbazide and the like.
[0010]
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.
[0011]
In the present invention, compounding agents (fillers) that do not significantly affect cross-linking, for example, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, silicon oxide, etc., for the purpose of reducing the physical properties or price of the composition used Metal oxides, carbonates such as magnesium carbonate and calcium carbonate, or fibrous substances such as pulp, or various dyes, pigments, fluorescent substances, and other commonly used rubber compounding agents, if necessary.
[0012]
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 160 ° C, depending on the type of the resin and the crosslinker. After heating at 10 ° C. for preferably 10 to 50 minutes, the pressure is removed to obtain a damping resin foam. Alternatively, the foaming agent is partially decomposed by heating in a closed mold under pressure and then depressurized to obtain an intermediate foam, and the obtained intermediate foam is subjected to normal pressure, for example, in a foaming machine by jacket-type heating. A conventional foaming method such as a two-stage foaming method for obtaining a final foamed body by heating in a heating medium or a heating medium bath can be applied. The heating temperature under normal pressure is set in the range of 140 to 210 ° C, preferably 150 to 190 ° C, depending on the type of the resin used. The heating time is preferably from 10 to 90 minutes, more preferably from 20 to 70 minutes.
[0013]
The resilience of the vibration-damping foam obtained in the present invention is measured by a test method specified in JIS K6401. Specifically, a 5 / 8-in parallel sphere is used, and the rebound distance when naturally dropped from a height of 460 mm is divided by a drop distance (percentage). 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 is excellent in damping properties and is particularly useful.
[0014]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples.
[0015]
Example 1
Triblock copolymer in which polystyrene and hydrogenated vinyl-polyisoprene are bonded (trade name “Hybler HVS-3”, styrene content 20%, vinyl bond 55%, glass transition temperature -19 ° C, manufactured by Kuraray Co., Ltd.) 90 parts by weight, 10 parts by weight of low-density polyethylene (trade name: Novatec YF-30, MFR 1.1 g / 10 min, density 0.920 g / cm3, manufactured by 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 were kneaded with a mixing roll at 85 ° C., and pressed at 155 ° C. The above kneaded product was filled in a mold (195 x 380 x 28 mm), 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 a rebound resilience of 6.5%, and was excellent in damping properties.
[0016]
Example 2
A vibration-damping resin foam was obtained in the same manner as in Example 1 except that azodicarbonamide was changed to 4.0 parts by weight in Example 1. The obtained foam had an apparent density of 0.089 g / cm3 and a rebound resilience of 18.5%, and was excellent in damping properties.
[0017]
Comparative Example 1
A foam was obtained in the same manner as 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. The foam obtained had an apparent density of 0.089 g / cm3 and a rebound resilience of 40%, and was inferior in vibration damping properties.
[0018]
【The invention's effect】
As described above, according to the present invention, a triblock copolymer in which polystyrene and hydrogenated vinyl-polyisoprene are combined has a glass transition temperature (Tg or tan δ absorption) in the room temperature range. Demonstrates high damping properties in this temperature range, and the resulting foam is excellent in damping properties, elongation, flexibility, weather resistance, water resistance, sound insulation, sports equipment such as athletic shoes, flooring materials, etc. Useful.

Claims (1)

A foaming agent and a crosslinking agent are added to a mixture of 70 to 95 parts by weight of a triblock copolymer in which polystyrene and hydrogenated vinyl-polyisoprene are combined and 30 to 5 parts by weight of a low-density 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.