JPH11206407A - Molded foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniform the formed state of a raw material elastomer and to reduce deterioration in tearing strength at the time of adding a large quantity of filler by compounding the pulverized powder of a sponge elastomer with a raw material elastomer and also cross-linking the raw material elastomer with a filler. SOLUTION: Since a boundary between the filler 1 of the sponge elastomer and the crosslinked sponge 2 of the raw material elastomer is erosslinked, the both of them 1 and 2 are firmly adhered by an anchor effect owing to the complicated projections/recessions of the interface 3, the occurrence of an interfacial peeling is eliminated because the area of the interface 3 for the adhesion of the members is drastically large. Moreover, a configuration and a structure are made uniform since the sponges are fixed and stress concentration does not occur so that tearing strength, etc., is not deteriorated and also resistance to repeated stress is increased. The addition quantity of filler to the raw material elastomer is preferably 0.5-50 wt.% and, more preferably, 5.0-20 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded foam used mainly for shoe soles.

[0002]

2. Description of the Related Art In a shoe sole such as a sports shoe, a molded foam of a closed cell made of resin or rubber is used as an impact buffer. Molded foams for shoe soles are generally processed into a predetermined shape by buffing, and so-called buffing powder (polishing powder) is generated during such buffing. Since the buff powder is discarded as industrial waste, it is not preferable from the viewpoint of effective use of resources and environmental conservation, and the cost for disposal is increased, so that the production cost is increased.

The following techniques have been proposed as techniques for using resin sponge and sponge rubber waste, but each has a drawback and has not yet been put to practical use.

[0004] For example, a shoe sole molding method in which a crushed piece of a scrap plate of a shoe sole plate is mixed with a raw material elastomer to obtain a foam (JP-B-56-15241, JP-A-52-116343)
In this case, the crushed pieces to be mixed have a large particle size, and since the compounded elastomer is heated and poured into a mold, a predetermined strength cannot be obtained.

[0005] Also, a method of manufacturing shoe soles using buff powder having a small particle size instead of the crushed pieces has been disclosed (Japanese Patent Application Laid-Open No. 5-154004). Since they are fixed to each other, a predetermined strength cannot be obtained. Further, the processing steps are complicated, and the production cost is greatly increased.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a molded foam having a predetermined strength, which can effectively reduce waste by effectively using sponge waste such as shoe soles.

[0007]

In order to achieve the above object, a molded foam of the present invention comprises a foamed elastomer obtained by foaming a crosslinked elastomer obtained by adding a crosslinking agent and a foaming agent to a raw elastomer, and crosslinking the foamed elastomer. A cross-linked sponge elastomer polishing powder is added to the raw material elastomer, and a cross-link is formed between the polishing powder and the cross-linked sponge of the raw material elastomer.

According to the present invention, the crosslinked sponge elastomer polishing powder (hereinafter simply referred to as “polishing powder”) is used.
By cross-linking with a new cross-linked sponge generated at the time of cross-linking of the raw material elastomer, the interface between the abrasive powder and the new cross-linked sponge is firmly fixed.

In the present invention, as shown in FIG. 1, since the interface 3 between the abrasive powder 1 of the sponge elastomer and the crosslinked sponge 2 of the raw elastomer is cross-linked, the anchor 3 due to the complex unevenness of the interface 3 is formed. Depending on the effect, both 1, 2
Are strongly bonded, and the area of the interface 3 with respect to the density of the member is extremely large. Therefore, there is no possibility that interface peeling will occur.

[0010] Further, since the sponges are fixed to each other,
Since the composition and the structure are uniform, there is no possibility that stress concentration occurs, so that the tear strength and the like are hardly reduced, and it is also resistant to repeated stress.

In the present invention, the "polishing powder" is not crushed pieces, but is produced by polishing or grinding with a polishing machine such as a buff, and the particle size is preferably 5.0 mm or less. If the particle size is larger than 5.0 mm, the foaming state is not uniform, air holes are easily generated, and a good molded product cannot be obtained. From this viewpoint, the particle size of the polishing powder is more preferably about 2 mm or less. Here, “approximately 2 mm or less” means that the mesh has passed through a sieve of 2 mm or less.

The amount of the abrasive powder added to the raw material elastomer is preferably 0.5 to 50% by weight, more preferably 5.0 to 30% by weight, and even more preferably 5.0 to 20% by weight. If the amount of the abrasive powder is too small, there is no point in adding the abrasive powder. On the other hand, if the amount of the abrasive powder is too large, the tear strength decreases. In particular, if the added amount of the abrasive powder exceeds 50% by weight, the workability of the roll is extremely reduced, for example, the roll kneading becomes difficult, and the occurrence of air holes increases rapidly, so that industrial production cannot be performed.

As the main component of the polymer of the present invention, that is, the following resin or rubber can be used as the main component of the raw material elastomer and the polymer of the abrasive powder, the same or similar material or interface is used. It is necessary to select materials capable of co-crosslinking (having good compatibility).
This is because if the same or similar materials or materials that can be co-crosslinked at the interface are not the same, the interface between the crosslinked sponge of the raw elastomer and the abrasive powder will not be crosslinked, so that sufficient tear strength cannot be obtained.

The main components of the raw material elastomer and the polymer of the abrasive powder are one or two of ethylene-vinyl acetate copolymer (EVA), polyethylene or syndiotactic 1,2-polybutadiene (RB), respectively.
More than one species can be selected and used. The main components of the polymer include natural rubber, SBR, BR, IR,
Diene rubber such as NBR, chloroprene rubber or E
One or more of the PDMs can be selected and used.

As a crosslinking agent, an organic peroxide such as dicumyl peroxide or 1,1-di- (t-butylperoxy) -3,3,5-trimethylcyclohexane can be used. Further, as the foaming agent, an organic foaming agent such as azodicarbonamide or dinitrosopentamethylenetetramine can be used. As a compounding agent, a filler, a softener, a plasticizer, an activator, a colorant, and other additives can be appropriately mixed. Further, in addition to the main component polymer, a natural rubber, a synthetic rubber, a thermoplastic elastomer, and the like can be appropriately mixed. Provided, however, that
The crushed debris of the non-crosslinked molded product of No. 6-15241 is not added because it cannot be made into fine particles.

As the polishing powder of the present invention, buff powder generated when a thermoplastic elastomer foam of resin or rubber such as EVA or RB is polished with a buff such as a grindstone or a wire brush can be used. The buff powder removes foreign substances and buff powder having a large particle size by using a mesh sieve having a predetermined size, thereby obtaining a molded product (molded foam) having good strength and finish.

The polishing powder is added at the time of a mixing step such as kneading and stirring of the base elastomer raw material dough. For example, to obtain a molded foam of EVA, EVA
After kneading the compounding agent with the resin, the abrasive powder is added, and then foamed by a method such as press molding or injection molding. Of course, abrasive powder may be added to a compounded elastomer obtained by kneading a compounding agent with a raw material elastomer as a base material (base polymer).

[0018]

EXAMPLES Examples and comparative examples will be described below to clarify the effects of the present invention. Comparative Example 10, Examples 11 to 18: As shown in Table 1 of FIG. 2 (a), after adding a compounding agent and EVA buff powder to a raw material elastomer composed of 90 parts by weight of EVA and 10 parts by weight of IR, press molding was performed. Thus, a molded foam was obtained. The EVA buff powder was passed through a 1 mm mesh sieve to reduce the particle size to about 1 mm or less, and the amount added was changed. As shown in FIG. 2 (b), the molded foam thus obtained generally has a slightly lower tear strength than Comparative Example 10 in which the EVA buff powder is not added, but does not hinder practical use. Absent.

The molded foam according to the present invention had a finish which was indistinguishable in appearance from the molded foam of Comparative Example 10. Therefore, it is generally difficult to visually determine whether the product is the molded foam according to the present invention or not. However, as described below, whether or not the product is the molded foam according to the present invention is determined by an electron micrograph. Can be determined.

FIG. 3A is a photomicrograph (magnification: 50 ×) of a cross section of the molded foam of Example 14 to which 10% by weight of buff powder was added, while FIG. It is a microscope picture of comparative example 10 which does not add. Paying attention to the cell walls in these photographs, it can be seen that the shape of the cell walls of the molded foam of Example 14 is slightly collapsed. In other words, it can be seen that the molded foam of Comparative Example 10 has a more uniform and beautiful cell wall shape. Therefore, by observing through a micrograph, it can be determined whether or not the product of the present invention.

Examples 21 to 24: As shown in Table 2 of FIG. 4 (a), a compounding agent and EVA buff powder were added to a raw material elastomer composed of 90 parts by weight of EVA and 10 parts by weight of IR, followed by press molding. A molded foam was obtained. EVA buff powder having a particle size of about 2 mm or less or about 4 mm or less passed through a 2 mm or 4 mm mesh sieve was used. The amount of the buff powder was 5 parts by weight or 20 parts by weight.

FIG. 4 (b) shows the measurement results of the tear strength of the molded foams of Examples 21 to 24, Comparative Example 10 and Examples 13 and 15 obtained as described above. As can be seen from the measurement results, when the particle size of the buff powder exceeds 2 mm, the tear strength is slightly reduced, but is in a range that does not hinder practical use.

Comparative Example 30, Examples 31 to 33: FIG.
As shown in Table 3 of (a), 70 parts by weight of RB and IR30
A raw material elastomer consisting of parts by weight, a compounding agent and EV
After adding the A buff powder, press molding was performed to obtain a foam. The EVA buff powder was passed through a 4 mm mesh sieve to reduce the particle size to about 4 mm or less, and the amount added was changed. It can be seen that the molded foams of Examples 31 to 33 thus obtained have a sufficient tear strength as shown in FIG. This is presumed to be because the interface between the newly generated RB sponge and the EVA buff powder was co-crosslinked.

Comparative Example 40, Examples 41 and 42: FIG.
As shown in Table 4 of (a), 50 parts by weight of SBR, IR1
After adding a compounding agent and rubber buff powder to a raw material elastomer composed of 5 parts by weight and 35 parts by weight of a high styrene resin, a foam was obtained by press molding. The rubber buff powder is obtained by polishing a general shoe sole material mainly composed of a diene rubber (a blend of natural rubber, SBR and BR) having good compatibility with the raw material elastomer, and sieving a 4 mm mesh sieve. The particle size was reduced to about 4 mm or less by passing through, and the amount of addition was changed. It can be seen that the molded foams of Examples 41 and 42 thus obtained have a sufficient tear strength, as shown in FIG. This is presumed to be due to co-crosslinking of the interface between the newly generated sponge and the rubber buff powder.

Comparative Examples 40 to 43: As shown in Table 5 of FIG. 7 (a), a compounding agent and EVA buff powder were added to a raw material elastomer comprising 50 parts by weight of solution-polymerized SBR, 15 parts by weight of IR and 35 parts by weight of a high styrene resin. After the addition, press molding was performed to obtain a foam. The EVA buff powder was passed through a 4 mm mesh sieve to reduce the particle size to about 4 mm or less, and the amount added was changed. As shown in FIG. 7B, the molded foams of Comparative Examples 41 to 43 obtained as described above showed that
It can be seen that the tear strength is significantly reduced. This is presumably because the interface between the crosslinked sponge of the raw elastomer and the buff powder was not co-crosslinked.

[0026]

As described above, according to the present invention,
A sponge elastomer polishing powder with a small particle size is added (blended) to the raw material elastomer instead of the crushed pieces obtained by crushing the sponge waste plate. Since the raw material elastomer and the abrasive powder are cross-linked and fixed, even if a large amount of the abrasive powder is added, the tear strength does not decrease so much. Accordingly, it is possible to effectively use waste materials of sponges such as shoe soles to protect the environment, and to obtain a molded foam having sufficient strength while reducing costs.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an enlarged cross section of a molded foam of the present invention.

FIG. 2 (a) is a chart showing the materials used in the test, and FIG. 2 (b)
Is a graph showing the measurement results of tear strength.

FIG. 3 is an electron micrograph showing a molded foam.

FIG. 4 (a) is a chart showing the materials used in the test, and FIG. 4 (b)
Is a graph showing the measurement results of tear strength.

FIG. 5 (a) is a chart showing the materials used in the test, and (b)
Is a graph showing the measurement results of tear strength.

FIG. 6 (a) is a chart showing the materials used in the test, and FIG. 6 (b)
Is a graph showing the measurement results of tear strength.

FIG. 7 (a) is a chart showing materials used in the test, and FIG.
Is a graph showing the measurement results of tear strength.

Claims (5)

[Claims] 1. A foam obtained by foaming and cross-linking a compounded elastomer obtained by adding a cross-linking agent and a foaming agent to a raw material elastomer, wherein a cross-linked sponge elastomer polishing powder is added to the raw material elastomer, and A molded foam, wherein a portion between the abrasive powder and the crosslinked sponge of the raw material elastomer is crosslinked. 2. The molded foam according to claim 1, wherein the particle size of the polishing powder is 5 mm or less. 3. The method according to claim 2, wherein the amount of the abrasive powder is 0.5 to 0.5% with respect to the raw material elastomer.
Molded foam set to 50% by weight or less. 4. The raw material elastomer and the polymer of the polishing powder according to claim 1, wherein the main component of the polymer is one of ethylene-vinyl acetate copolymer, polyethylene or syndiotactic 1,2-polybutadiene. Molded foam consisting of seeds or two or more kinds. 5. The rubber composition according to claim 1, wherein the main components of the raw material elastomer and the polymer of the polishing powder are diene rubber, chloroprene rubber or EP.
A molded foam comprising one or more of DM.