JPH0414130B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a low-resilience rubber foam having an impact resilience of 0 to 35%, and more specifically, it is capable of absorbing strong impacts generated during walking, running, etc., and protects the nervous system and joint system of the foot. The present invention relates to a low-resilience rubber foam that can be particularly suitably used as a material for shoes. Generally, when walking or running, an impact force of about 2.7 times the body weight is applied to the feet, and this impact force causes damage to the joint systems such as heels and knees, and the nervous system. Therefore, one of the important roles of shoes is to alleviate and absorb the above-mentioned impact force. This impact-reducing or impact-absorbing property is considered to be important for shoes in general, but is particularly necessary for sports shoes used during strenuous exercise and medical shoes used by rheumatoid arthritis patients. Conventionally, a method of increasing the shock absorption properties of shoes has been to use low-hardness materials in the heel of the shoe, and such low-hardness materials include natural rubber or materials with a glass transition temperature of -20°C or lower. Synthetic rubber foam is used. However, if this type of low-hardness material is thin, it not only does not provide sufficient impact absorption performance, but also bottoms out when the impact force is large, and it no longer functions as a shock absorber. Furthermore, if the hardness of the low-hardness material is increased in order to avoid bottoming out, the shock absorption performance will be extremely reduced.
For this reason, the material has conventionally been used in a relatively thick manner. However, in order to obtain sufficient shock absorption performance with this material, it needs to be quite thick, which results in heavy shoes, and the recent general trend in shoes is to make them lighter. On the contrary, it is not desirable. Moreover, if a material with low hardness is used thickly, the material itself will shift inside the shoe, making the shoe extremely uncomfortable to wear and making the foot unstable when running. For this reason, there is a need for a material that has lower impact resilience than before, has excellent shock absorption, has high strength, low hardness, low compression set, and is lightweight, and can be suitably used as a material for shoes. Recently, ethylene-
The use of high-loss materials such as vinyl acetate copolymers and polyurethane foams has been proposed, but these do not have sufficient shock absorption performance, and when used as materials for shoes or shoe components, they do not adequately protect feet. It is far from possible. Incidentally, weight reduction is currently considered to be an important issue as a general trend in rubber products, and there is a strong desire for weight reduction in low rebound elastic rubber as well in order to further increase added value. However, if a normal low resilience rubber composition is foamed as is using an organic foaming agent, the impact resilience will increase due to the influence of the introduced air bubbles. In view of the above circumstances, the present inventors have conducted extensive research and have previously discovered and proposed a rubber composition and foam thereof that exhibit low resilience in a wide temperature range of -10°C to 50°C, but further research is required. As a result, fillers, plasticizers, By adding a foaming agent in a specific amount, adding a vulcanizing agent and a vulcanization accelerator, heating, foaming, and curing,
The inventors discovered that it is possible to obtain a lightweight rubber foam that exhibits a low rebound resilience of 0 to 35% at a wide temperature range of -10 to 50°C, has excellent shock absorption properties, and has led to the present invention. . The low-resilience rubber foam of the present invention has excellent shock absorption properties as described above and is lightweight, so it can be suitably used as a material for shoes as described later, but it can also be used for other purposes, such as Suitable for acoustic components such as turntable rubber sheets, vibration damping materials, shock absorbers, damping agents, vibration isolators, sound insulation materials, various grips, table tennis racket weight materials, baseball gloves, gloves, protectors, helmets, etc. Can be used. The present invention will be explained in more detail below. The low-resilience rubber foam of the present invention comprises: (a) A: A high styrene-content styrene-butadiene copolymer whose styrene content is adjusted to 53 to 75% by weight through the polymerization process or blending B: Based on the total amount of mixed rubber Mixed rubber of a high styrene content styrene-butadiene copolymer and a general purpose rubber (b) 30 to 300 parts by weight of filler per 100 parts by weight of the mixed rubber. (c) 5 to 60 parts by weight of a plasticizer per 100 parts by weight of mixed rubber; (d) a blowing agent of 0.5 to 50 parts by weight per 100 parts by weight of mixed rubber; and (e) a vulcanizing agent by heating the mixture. It is obtained by foaming and curing, and has a rebound resilience in the range of 0 to 35%. As mentioned above, the high styrene content styrene-butadiene copolymer (a) of component (a) (mixed rubber) needs to have a styrene content of 53 to 75% (wt%, the same applies hereinafter). However, it is particularly preferably 56 to 65%. In addition, when the above-mentioned high styrene content styrene-butadiene copolymer is obtained by blending, it can be obtained by blending styrene and butadiene copolymers having various different styrene contents.
It can be suitably obtained by blending a styrene-butadiene copolymer in a range of 75%. Of the above component (a) (mixed rubber), (a) general-purpose rubbers include natural rubber, isoprene rubber, and styrene rubber.
Rubbers having a glass transition temperature of -20° C. or lower, such as butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, and ethylene-propylene rubber, are preferably used. This general-purpose rubber is mixed with the above-mentioned styrene-butadiene copolymer in an amount of 40% or less, more preferably 10 to 40%, based on the total mixed rubber. As mentioned above, the component (b) (filler) needs to be blended in an amount of 30 to 300 parts by weight per 100 parts by weight of the mixed rubber, but especially in an amount of 150 to 200 parts by weight. It is preferable that Ingredients (b) include calcium carbonate, barium sulfate, magnesium carbonate, dolomite, kaolin clay, calcined clay, hard clay, sericite, talc, talc, wollastonite, bentonite, muscovite, aluminum hydroxide, zinc white, Fillers selected from non-reinforcing or weakly reinforcing fillers such as activated clay, hallosite, titanium oxide, gypsum, light ash, heavy ash, barium carbonate, strontium carbonate, diatomaceous earth, shirasu, shirasu balloon, calcium sulfate, etc. It is preferable to use As mentioned above, the component (c) (plasticizer) needs to be blended in an amount of 5 to 60 parts by weight per 100 parts by weight of the mixed rubber, but in particular, it is preferably 20 to 40 parts by weight. preferable. Component (c) includes aroma oil, naphthenic oil, spindle oil, dioctyl phthalate, polybutene, phosphoric acid derivatives such as tricresyl phosphate, fatty acid derivatives,
Any compound that can be used for rubber, such as sulfonic acid derivatives, can be used. As mentioned above, the component (d) (foaming agent) needs to be blended in an amount of 0.5 to 50 parts by weight per 100 parts by weight of the mixed rubber, but in particular, it is preferably 2 to 20 parts by weight. preferable. Component (c) includes organic compounds such as dinitrosopentamethylenetetramine (DPT), azodicarbonamide (AZC), p-toluenesulfonyl hydrazide (TSH), and 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH). Any foaming agent that can be used for foaming rubber can be used, such as foaming agents and inorganic foaming agents such as sodium hydrogen carbonate. The low resilience rubber foam of the present invention has the above-mentioned (a) to (d)
It can be obtained by adding the vulcanizing agent (e) to a mixture consisting of the four components, and heating and foaming the mixture. In this case, the vulcanizing agent is organic peroxide, sulfur,
Known organic sulfur compounds such as tetramethylthiuram disulfide can be used. The vulcanizing agent is usually used in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the mixed rubber. In addition, a vulcanization accelerator can be added if necessary. In this case, the vulcanization accelerators include aldehyde-amines, aldehyde-ammonias, dithiocarbamates, guanidines, thiurams, sulfenamides, thiazoles,
Known ones such as thioureas can be used. The amount of vulcanization accelerator is usually 0.5 to 100 parts by weight of mixed rubber.
10 parts by weight may be used. Furthermore, in addition to the above-mentioned components, optional components such as reinforcing agents such as carbon black and silica, waxes for preventing deterioration, and anti-aging agents can be added to the low-resilience rubber foam of the present invention. . The low rebound rubber foam of the present invention can be mixed and cured by conventional methods. In this case, the curing temperature is preferably 110 to 180°C. If the curing temperature is below 110°C, it will take a long time to cure and the blowing agent may not decompose sufficiently, and if it is above 180°C, the physical properties of the rubber foam will deteriorate and a stable rubber foam will not be obtained. A situation may arise. The low-resilience rubber foam of the present invention is -10 to 50℃
It exhibits a low impact resilience of 35% or less over a wide temperature range, and has excellent shock absorption properties. Further, the low resilience rubber foam of the present invention usually has a specific gravity of 0.7 or less and is extremely lightweight. Furthermore, the low resilience rubber foam of the present invention is
It usually has a compression set of 5 to 50% and has excellent restorability. The low-resilience rubber foam of the present invention has excellent properties as described above and can be used for various purposes, but it has hardness, strength, and compression set that are particularly suitable as shoe materials. Therefore, it can be suitably used as a material for shoes such as sports shoes and medical shoes that protect the nervous system and joint system of the feet by absorbing the strong impact generated when walking or running.
In this case, for example, as shown in FIG. It can be suitably used as a manufacturing material for members, and its shock absorbing performance is particularly effective when used for the insole 1, insole 2, midsole 3, and midsole 4. Note that when producing insole etc. of shoes, good performance can of course be obtained by using the rubber foam of the present invention alone, but if the rubber foam of the present invention is used in addition to other rubber materials, Even better performance can be obtained by laminating the bodies. For example, as shown in FIGS. 2 to 4, for the layer 11 of the rubber foam of the present invention, a rubber composition using ethylene-vinyl acetate copolymer, polyurethane foam, various foam rubber compositions, or general-purpose rubber may be used. By laminating the layers 12, an insole etc. with even better shock absorption and cushioning properties can be obtained. Here, the general-purpose rubber mentioned above is one with a glass transition temperature of -20°C or lower from among natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, ethylene-propylene rubber, etc. It is preferable to select and use them. Note that the above-mentioned foamed rubber composition refers to both rubber made by adding an organic or inorganic foaming agent and vulcanized and foamed, and foam rubber made from latex. In addition,
In FIGS. 2-4, reference numeral 13 designates a fabric covering the upper surface of layer 12. As described above, when the rubber foam of the present invention is used as a material for shoes and shoe components, since the rubber foam of the present invention has excellent shock absorbing properties, it can absorb shocks generated during walking and running. Since it is possible to obtain a shoe that provides cushioning and is lightweight, it is useful for reducing the weight of the shoe. In this case, since the rubber foam of the present invention exhibits sufficient shock absorbing properties even in a small amount, it is possible to prevent the material from shifting or increasing in weight due to use in a large amount. Further, it is preferable that the inner surface of the shoe deforms to some extent to fit the user's foot, but the rubber foam of the present invention has a compression set of 5 to 5.
50%, the shoes made of the rubber foam of the present invention conform well to the user's feet. In other words, if the compression set is less than 5%, the foot will not deform into the shape of the foot, and no good fit will be obtained, and if it is larger than 50%, a sagging phenomenon will occur, and therefore the compression set will be 5 to 50%. Good fitting properties can be obtained only in this case. EXAMPLES The present invention will be specifically explained below with reference to Examples. [Examples 1 to 4, Comparative Examples 1 to 5] The raw materials of Examples 1 to 4 having the formulation shown in Table 1 were kneaded for 30 minutes with a roll having a surface temperature of 70°C to form a sheet. After that, this was filled into a 25 x 30 x 1.5 cm mold, and the pressure was 90 Kg/cm ² , the temperature was 140°C, and the heating time was 25.
After pressurizing and heating under conditions of 10 minutes, the mold was demolded. In addition,
In Table 1, calcium carbonate was used as the filler and aromatic oil was used as the plasticizer. Further, in Table 1, parts are parts by weight, and % is weight %. Next, various physical properties of the rubber foams of Examples 1 to 4 were measured. For comparison, natural rubber foam (Comparative Example 1), EVA foam (Comparative Example 2), RB foam (Comparative Example 3), chloroprene foam (Comparative Example 4), and special urethane foam (trade name: Solbutan ) (Comparative Example 5) were measured in the same manner. The results are shown in Table 2. The hardness in Table 2 was measured using a type A hardness tester specified in JIS6301.
Measurements were made at 20°C, compression set was measured at 70°C for 48 hours, and 75% compression, and rebound resilience was measured using a Dunlop tripsometer.

【table】

[Table] From the results in Table 2, it is recognized that the rubber foam of the present invention has a lower impact resilience over a wider temperature range than the rubber foam of the comparative example. Next, using the rubber foams of Example 1 and Comparative Examples 1, 2, and 5, their impact absorption performance was measured.
In this case, the shock absorption performance was determined by measuring the maximum acceleration using a falling weight impact tester under the conditions of a weight of 5 kg, a falling height of 10 cm, and an area of 9 cm ² of the contact surface of the weight with the sample.
Evaluation was made based on this. The results are shown in Table 3.

[Table] From the results in Table 3, it is recognized that the rubber foam of the present invention has significantly better shock absorption properties than the rubber foam of the comparative example.

[Brief explanation of drawings]

FIG. 1 is a partially sectional side view of a shoe using the rubber foam of the present invention, and FIGS. 2, 3, and 4 are sectional views of a laminate used as an insole of the shoe, respectively.

Claims (1)

[Scope of Claims] 1 (a) A: High styrene content styrene-butadiene copolymer whose styrene content is adjusted to 53 to 75% by weight through polymerization process or blending B: 40% by weight based on the total amount of mixed rubber A mixed rubber consisting of a high styrene content styrene-butadiene copolymer and a general-purpose rubber consisting of the following general-purpose rubbers (b) 30 to 300 parts by weight of filler per 100 parts by weight of mixed rubber (c) 100 parts by weight of mixed rubber 5 to 60 parts by weight of plasticizer (d) 0.5 to 50 parts by weight of blowing agent to 100 parts by weight of mixed rubber (e) A mixture containing (a) to (e) of vulcanizing agent is heated and foamed. A low-resilience rubber foam that has an impact resilience of 0 to 35% when cured.