JPS5854803B2 - Manufacturing method for semi-transparent rubber foam for shoe soles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a semi-transparent shoe sole with a beautiful velor effect, a structurally non-slip effect, and a foam cross section oriented in a certain direction with good adhesion. Method for producing rubber low foam;
More specifically, by uniformly mixing and molding natural rubber, (and) synthetic rubber, or their blended rubber compound with fiber flock, rosin resin, petroleum resin, or a mixture thereof, and a foaming agent, and heating, the box can be made into a uniform and dense product. In addition to exhibiting a beautiful velor effect, the fiber flock and foaming effect make it structurally extremely slip resistant.The fiber flock is oriented in a certain direction on the cross section, making it translucent, and has strong adhesion. The present invention relates to a method for obtaining a low-foamed rubber material for shoe soles having properties.

Sole crepe, a type of natural rubber, has recently been widely used as a material for shoe soles. Sole crepe is a natural crepe for shoe soles that is made by layering thin crepe sheets made of coagulated natural latex and pressing them.

This crepe is light, flexible, and translucent, making it easy to wear as the sole of shoes, and has features such as being resistant to snow.

However, since it is layered in cross section, interlayer delamination is likely to occur, and a special bonding method is required.

Additionally, since it is an unvulcanized sheet, it is sensitive to heat and oil and easily deforms.

Furthermore, it has disadvantages such as being sticky, easily oxidized, brownish in color, and having inconsistent performance.

Yet another serious drawback is that natural sole crepe contains water, so in winter, the water freezes and the entire crepe hardens and cracks, making it unusable as a shoe sole.

Conventionally, the method for manufacturing translucent rubber foams involves adding a blowing agent and a natural rubber or (and) a synthetic rubber or a blend thereof, which is a uniform mixture of a vulcanizing agent, a vulcanization accelerator, a reinforcing agent, and a lubricant. The foaming aid is uniformly mixed and molded, a predetermined amount is filled into a mold, heated to decompose the foaming agent, and after vulcanization for a certain period of time, the foam is removed from the mold.

In this case, the shape and appearance of natural sole crepe cannot be obtained because the product is simply a foam both in the case and in cross section.

Also, a manufacturing method in which fiber flock is mixed into rubber foam has been adopted, but short fiber flock of 3 mm or less is often used for fiber flock such as cotton, human silk, nylon, or vinylon because the dispersion is generally poor. ing.

In a low-foamed material obtained using short fiber flocks, the fiber flocks are not oriented in a fixed direction, and no velor effect on the wave surface can be expected.

Moreover, its cross section is not similar to natural sole crepe.

Translucent or transparent rubber foams are available on the market for use in shoe soles, but their adhesive strength is extremely poor, and commonly used adhesive methods or adhesives cannot provide the necessary adhesive strength for shoe soles. It has disadvantages that cannot be obtained,
It is generally accepted that translucent or transparent rubber or its foam has extremely low adhesive strength.

In general, rubber has greater frictional resistance than plastics, and this feature is used to make the soles of shoes.

However, it is known that even smooth rubber and rubber foam can be slippery on smooth floors or wet roads.

For this reason, the current practice is to create a textured pattern on the mold to improve its slip resistance.

Therefore, the production cost of the mold is high, and the production time is also long.

The present inventors investigated various drawbacks of natural sole crepe and investigated conventional methods of manufacturing translucent rubber low-foam products. and) synthetic rubber or their blend rubber, rosin resin, petroleum resin, or mixture,
By uniformly mixing three types of ingredients, fiber flock and a foaming agent, and heating and molding, a beautiful velor product with long fiber flocks uniformly and densely arranged between the foamed cells on the smooth wave surface of the vulcanized product is created. I was able to find an effect.

In addition, since the wave surface with a velor effect has a structure as shown in Figure 2 consisting of air bubbles and fiber flocks, when the sole of the shoe comes into contact with the road, the frictional resistance is large and the effect of preventing slipping is effectively exhibited. We have found that it has the advantage of being non-slip, especially on wet road surfaces.

They also found that the cross-sectional structure differs from that of ordinary foams, with long fiber flocks oriented in a certain direction, resembling natural sole crepe.

The physical properties of this low foam rubber material were found to be superior to those of natural rubber crepe.

Table 1 shows a comparison of the physical properties of a typical low-foam rubber foam made by the inventor and natural sole crepe.

Note: Aging condition: Near 0°C x 96 hours The present invention is not made by layering sheets like natural sole crepe, but by molding them to a certain thickness and heating them, so delamination may occur. However, as shown in Table 1, it is recognized that it has excellent properties in terms of strength, aging resistance, oil resistance, tear strength, cold resistance, adhesive strength, and density.

Secondly, since it contains fiber flock and petroleum resin or rosin resin, it has a high adhesive strength as a shoe sole, and the bonding method is conventional and conventional, using a single component adhesive such as a chloroprene adhesive. It was also recognized that the law was sufficient.

Shoe soles made of translucent or transparent rubber have had the disadvantage of low adhesive strength, but it can be said that the present invention has made a significant improvement.

Comparative data on the adhesive strength of one of the resins and a rubber foam containing no resin is shown in Example Table 3.

A major feature of this low foam rubber material is that it has a non-slip effect as a shoe sole.

As shown in Figure 1, this foam has fine air bubbles and long fiber flocs dispersed uniformly and densely, and when this is filtered with a sieving machine, the fiber flocs are arranged in a fixed direction as shown in Figure 2. A fine uneven structure made of air bubbles and fiber flock appears, and when worn as shoes, the unevenness makes the shoes less slippery.

In the drawings, 1 is a foamed cell, 2 is a fiber flock, and 3 is a box.

The main point of the invention is as explained above, by combining three types of compounding agents: fiber flock, resin, and foaming agent with a translucent rubber compound and heat-molding it, it becomes translucent with 0.6
A low-foam rubber material with a density of ~0.9 is obtained, which has three features: a beautiful velor effect, a non-slip effect, a translucent appearance, and an excellent adhesive force.

In order to obtain transparency in the latter half of thermoforming according to the invention, additives having a transparency effect, such as hydrous silicic acid, magnesium carbonate or silicates, should be used as reinforcing agents or fillers.

Furthermore, there is no problem in using inorganic pigments or organic dyes as long as translucency is not lost.

The "velor effect" used in the present invention means the following.

That is, by uniformly mixing and molding long fibers in the range of 3 to 25 mm and a foaming agent into a rubber compound, and heating and foaming, the resulting rubber low-foamed material is sieved to a certain thickness to form a fiber flock. A smooth surface that is uniformly dense and oriented in a certain direction is obtained.

This side is a nice brushed surface with a velvety feel and appearance.

This is a raised effect in which these fiber flocks stand out between fine air bubbles and are oriented in a certain direction.

The fiber flock used in the present invention refers to natural fibers such as cotton and wool, chemical fibers such as soft cotton and human silk, and synthetic fibers such as polyamide fibers, vinylon fibers, and polyester fibers, cut into 3 to 25 pieces. It is processed flock.

In the case of natural fibers such as linters, there is no need to cut them within the length range.

The appropriate length of this flock is within the range of 3 to 25 mm; fiber flocks shorter than this length are close to powder-like and have good dispersibility, but the velor effect described above It is not possible to achieve this effect, and there is no effect of orienting the fibers in a certain direction.

Next, if long fibers of 25 mm or more are used, they cannot be used because they result in poor dispersion during mixing with the rubber and compounding agents.

Further, even if the fiber flock is within the above range of 3 to 25 degrees, if the amount used is less than 0.1 part, the velor effect and the anti-slip effect cannot be exhibited.

The resin used in the present invention has a softening point of 125 to 135.
℃, rosin resin with acid value 25-30 and softening point 120-
It is a petroleum resin with an acid value of 0 to 0.5 at 130°C, and is a special resin that has not been used as a conventional rubber compounding agent due to its high softening point.

In other words, common rosin is modified to increase its softening point and its acid value to 25%.
It is a modified resin with a degree of unsaturation of ~30, which is about 1/6 that of rosin.

It has been found that the addition of this resin to rubber has the dual effect of strengthening the rubber foam, which is physically weaker than solid rubber, and enhancing the foaming effect as a foaming aid.

Also, petroleum resins usually have a softening point of 100°C for use in general rubber.
The following substances mainly act as adhesives, softeners, plasticizers, dispersants, or organic reinforcing agents for solid rubber. It was found that it exhibits almost the same effect as resin.

The appropriate amount to use is 5 to 50 parts, but especially 1
0 to 30 parts is desirable.

The purpose of using this resin is to facilitate foaming, reduce the density of the foam, and improve adhesive strength after vulcanization.

If the amount used is 5 parts or less, the density of the foam will be 0.9 or more, which will have no effect as a foaming aid, and no effect of increasing adhesive strength after vulcanization will be obtained.

Further, if the amount exceeds 50 parts, vulcanization is inhibited and it is difficult to stabilize foaming.

The blowing agent used in the present invention is a known compound that is liquid or solid at room temperature and decomposes to generate gas when heated.

Organic blowing agents include nitroso-based, aromatic hydrazide-based,
Examples include azo-based compounds, such as azodecarbonic acid, diazoaminobenzene, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, and benzenesulfonylhydrazide.

The amount of blowing agent to be used varies depending on the formulation used, and in order to make the density of the rubber low foam material 0.6 to 0.9, a range of 0.5 to 2 parts is appropriate. .

Next, examples using the method of the present invention will be shown.

Example 1 Translucent rubber low foam compound In Table 4, A1 is an example in which no resin is used, A2 and A3 are examples of the present invention, and A4 is an example in which a resin higher than that specified in the present invention is used. .

Table 3 shows the physical properties and properties of the foam obtained using the ingredients shown in Table 2.

Adhesion strength was determined using chloroprene adhesive, bonding between leather and rubber, vulcanization conditions: 145°C x 10 minutes. According to the results in Table 3, when comparing cases with and without resin, It can be seen that there is an extremely large difference in specific gravity and a large difference in adhesive strength.

Furthermore, if the amount of resin is increased, vulcanization becomes unstable and elongation increases, making it impossible to obtain appropriate physical properties for a shoe sole.

Example 2 As a translucent rubber low foam formulation example, A1 in Table 4 is a comparative example in which no resin is used, A2 and A3 are inventive examples in which petroleum resin is used alone, and A4 is an example in which petroleum resin is used alone. A5 is a comparative example in which petroleum resin is used, and A5 is an invention example in which a mixture of rosin resin and petroleum resin is used.

Table 5 shows the physical properties and properties of the foam obtained using the ingredients shown in Table 4.

According to the results in Table 5, 1P&, 2, using resin
JFy.

Comparing No. 3 and A5 with AI that does not use resin, it is recognized that the specific gravity after heating and foaming is different and there is a large difference in adhesive strength.

And MI of box production! ? It was found that A1 did not exhibit a velor effect, and A5 did not foam uniformly and did not exhibit a velor effect.

Furthermore, when the amount of resin was increased, the addition of mud became unstable and the elongation increased, making it impossible to obtain appropriate physical properties as a shoe sole.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view showing a state in which foamed cells and fiber flocks are dispersed in a low-foam product according to the present invention, and FIG. 2 is an enlarged cross-sectional view showing the foamed product of FIG. 1 in a box. 1... Foamed bubbles, 2... Fiber flock, 3... Box production.

Claims (1)

[Claims] 1 Natural rubber or synthetic rubber or blend rubber thereof with addition of compounding agents used for translucent formulations 10
0 parts by weight to 0.1 to 5 parts by weight of fiber flock within the length range of 3 to 25 inches, 5 to 50 parts by weight of softening point 125
~135°C, a rosin resin having an acid value of 25 to 30, a petroleum resin having a softening point of 120 to 130°C, an acid value of O to 0.5, or a mixture thereof, and 0.5 to 2 parts by weight of a blowing agent are combined. By uniformly mixing them together, forming and heating them, a low-foaming state with a density of 0.6 to 0.9 is produced, which provides a beautiful velor effect in box manufacturing and a non-slip effect on the contact surface, resulting in a constant fiber flock. A method for producing a semi-transparent rubber low-foamed material for shoe soles which has a foam cross section oriented in the direction and has excellent adhesion.