JP4001266B2 - Manufacturing method of foamed resin boots - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a foamed resin boot formed by injection molding.
[0002]
[Prior art]
Conventionally, boots by injection molding are composed entirely of solid synthetic resin, so they are heavier than ordinary shoes, etc., and users tend to get tired when used for long-time work. It was a thing. Therefore, in order to reduce the weight, the main body of the entire boot excluding the bottom part is injection-molded, and only the bottom part of the boot body is manufactured using another lightweight material such as EVA. The bottom was bonded and integrated. However, a material produced by bonding another member in this way has been reduced in weight only at the bottom, and is insufficient in terms of weight reduction. In addition, when the used boots are discarded and recycled as a resin material, it is necessary to separate the main body and the bottom, which are separate materials.
Accordingly, the present inventors have proposed an injection molding technique suitable for manufacturing a lightweight boot such as Japanese Patent Application No. 2000-156647 in order to further reduce the weight of the injection molded boot. In general, in injection-molded boots, the last mold, which is a male mold, is inside, the side mold, which is a female mold, is external, and a synthetic resin is injected into the gap portion. Generally, it is provided on the bottom surface of the design surface. For this reason, since the resin is thicker in the bottom part than in the other body parts, it is necessary to make the filling pressure larger than that of general injection-molded shoes in order to completely fill the whole part. Even when a foaming agent was added to the synthetic resin and foamed, the foaming agent did not sufficiently foam and weight reduction could not be achieved. Further, when the boot main body portion is made thinner for weight reduction, the filling pressure becomes larger and the resin is hardly foamed.
Therefore, in this technology, by providing an injection hole in the main body part that is thinner than the bottom, the filling pressure is kept low, the foaming agent is sufficiently foamed, and the boot can be made thinner. It is what.
[0003]
[Problems to be solved by the invention]
By the way, when manufacturing boots by applying the above-described technique, it is possible to manufacture extremely lightweight boots that are foamed entirely including the thin-walled portion of the main body. In some cases, the sole part becomes too soft or the sole of the shoe tends to wear out and the durability may be inferior depending on the use of the boot. There was a problem.
[0004]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent a problem that a sole portion is too soft or a shoe sole is easily worn when manufacturing a thin and light foamed resin boot by injection molding.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a foamed resin boot in which a boot body is formed by injection molding , and a solid bottom part is integrated into at least a heel part and a stepping part of a sole part of the boot body. As a manufacturing method, the boot body is composed of a cylindrical thin-walled molded part and a thick-walled molded part that forms a sole part continuous with the thin-walled molded part, and a foam molding material using a thermal expansion type microcapsule, The boot body was foamed as a whole by injection from the thin molded portion at the top of the boot body toward the thick molded portion.
[0006]
Here, the solid part is a material part filled with non-foamed contents, and while trying to reduce the weight by foaming the boot body, the sole part gives hardness to the sole part, Abrasion resistance can be improved. In addition, the bottom part is provided on the heel part and the stepping part that are frequently contacted with the floor surface or the like in the sole part, but may be provided on the entire sole part.
For example, soft polyvinyl chloride (PVC) resin is suitable as the resin material for the boot body. Also, as the bottom part, it can be integrated with the boot body. A material excellent in properties such as a rubber material such as polyvinyl chloride resin, natural rubber, and synthetic rubber is suitable. Note that it is preferable that the boot body and the bottom part are made of the same synthetic resin because recyclability is improved.
[0007]
In the present invention, as the main bottom part , a press-molded part is integrated with the boot body at the time of injection molding of the boot body .
[0008]
Thus, if the bottom part is integrated during the injection molding of the boot body, it can be manufactured efficiently.
Here, as a method of integrating the bottom part at the time of injection molding of the boot body, for example, a so-called two-color molding in which after molding the bottom part using a dummy mold, the mold is reassembled and the boot body is injection molded. Alternatively, it is possible to apply a method such as injection molding of the boot body by positioning the press-formed main bottom part at a predetermined position in the cavity. At this time, the thickness of the bottom part can be appropriately determined depending on the use of the boot, etc., but the base thickness excluding the design portion is about 1.0 to 3.0 mm in terms of weight reduction and water resistance. It is desirable to make it.
[0009]
In the present invention, when the foamed resin boot body is foamed, thermal expansion type microcapsules are used for foaming . On the other hand, for example, a thermal decomposition type foaming agent is used. When foamed, an unfoamed skin layer is formed at the part in contact with the mold, so the thinned part has a very narrow foaming area, limiting the weight reduction, and secondary foaming tends to continue. Need a long time.
Therefore, by using a thermal expansion type microcapsule and foaming, unlike the thermal decomposition type foaming or the like, without forming a skin layer on the surface part, foaming to the part in contact with the mold for further weight reduction. In addition to being able to achieve foaming, it is possible to foam more uniformly and to suppress secondary foaming that continues foaming after injection molding and to shorten the cooling time after molding.
Although the durability and water resistance of the outsole are reduced by the weight reduction by foaming of the thermal expansion type microcapsule, a good foamed resin boot can be obtained by using the outsole part of the present invention. it can.
[0010]
Here, as the thermal expansion type microcapsule, for example, an expansion agent such as propane, butane, pentane, or isopentane is encapsulated inside a spherical resin shell, and is preferably expanded several times to several tens of times by heat. is there.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the accompanying drawings.
Here, FIG. 1 is an explanatory view showing an example of a foamed resin boot according to the present invention, FIG. 2 shows a bottom part, (a) is a side view, (b) is a bottom view, and FIG. 3 is an injection molding mold. Explanatory drawing and FIG. 4 are explanatory drawings of the state which clamped the injection mold.
[0012]
The foamed resin boot 1 according to the present invention can prevent a problem that a sole portion is too soft or a shoe sole is easily worn when a thin and light boot is produced by injection molding. As shown in FIG. 1, a solid bottom part 3 is integrated with the sole part of the boot body 2 made of foamed resin so that the sole part is hardened and the wear resistance is improved. I am doing so.
[0013]
Here, the boot body 2 made of foamed resin is suitable if applied to the boot body 2 in the case of being molded by the injection mold 4 as proposed by the applicant in Japanese Patent Application No. 2000-156647, for example. It can be molded lightweight. First, the injection mold 4 will be described.
[0014]
As shown in FIG. 3A, the injection mold 4 includes a last mold 5 having a foot shape, a pair of left and right side molds 6 surrounding the side of the last mold 5, and a periphery of the lower surface of the last mold 5. A surrounding bottom mold 7 is provided, and a cavity space C as shown in FIG. 4 is defined in a clamped state.
[0015]
A material injection path 8a (FIG. 4) extending in the vertical direction is formed in an intermediate portion of the bottom mold 7, and a groove 8b (FIG. 3) communicating with the material injection path 8a is formed on the upper surface of the bottom mold 7. ) Is engraved toward the toe side.
[0016]
The left and right side molds 6 are formed with a groove 8c that can be connected to the toe-side extending end of the groove 8b facing upward, and the extending end of the groove 8c is connected to the gate groove 8g. Yes.
When the left and right side molds 6 are clamped, the grooves 8c and the gate grooves 8g of the left and right side molds 6 are overlapped to form a flow path and a gate for the molding material. It is made to open toward the thin width part.
[0017]
For this reason, when the foam molding material is injected from the material injection path 8a in the mold clamping state, the molding material is directed from the thin molded portion of the boot to the thick molded portion of the boot via the grooves 8b and 8c and the gate groove 8g. The cavity space C is filled, and even when a thin and lightweight boot is formed by reducing the gap width of the cavity space C as a whole, it can be uniformly foamed with a low filling pressure. become.
[0018]
A method for manufacturing the foamed resin boot 1 using the injection mold 4 as described above will be described.
First, the bottom part 3 as shown in FIG. 2 is formed. Here, as the bottom part 3, a solid material such as soft polyvinyl chloride resin or rubber (not foamed and filled) can be applied. In this embodiment, soft vinyl chloride is used. The resin is molded by press molding, and as shown in FIG. 2, the form covers the entire boot bottom from the toe portion to the heel portion.
Here, the form of the bottom part 3 can adopt any form as long as it includes a stepping part and a buttocks that often contact the floor surface during walking or the like. It may be divided into two parts, and a part that covers each part locally.
The molding method may be molding by injection molding instead of press molding.
[0019]
Further, the bottom side design of the bottom part 3 is the same as the boot bottom design of the bottom mold 7, and the bottom part 3 is positioned on the bottom mold 7 and the boot body 2 is positioned as described below. When performing injection molding, the bottom part 3 is prevented from being displaced.
[0020]
Further, the thickness t of the base portion other than the design convex portion of the bottom part 3 is set to about 1.5 mm in the range of 1.0 to 3.0 mm. This is because if the thickness t is less than 1.0 mm, the durability becomes inferior due to wear or the like, and if it exceeds 3.0 mm, the weight tends to increase or the flexibility tends to decrease.
[0021]
When the bottom part 3 as described above is positioned on the sole part of the bottom mold 7 and clamped as shown in FIG. 3B, the cavity space C is formed in the state shown in FIG. . Therefore, the boot body molding material is injected into the cavity space C to form the boot body 2 and integrated with the bottom part 3.
[0022]
Here, in this example, the boot body molding material is a composition in which a thermally expandable microcapsule is blended with a resin mainly composed of soft polyvinyl chloride (PVC).
And as the thermal expansion type microcapsule, a spherical resin shell is preferably encapsulated with an expansion agent such as propane, butane, pentane, isopentane, etc., and expands several to ten times by heat, In the examples, commercially available Matsumoto Microsphere F-110D (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) or EXPANCEL 092-120 DU (manufactured by EXPANCEL Co.) encapsulating isopentane inside the shell of acrylonitrile copolymer is composed. 3 to 10 parts by weight, more preferably 6 to 8 parts by weight is added to 100 parts by weight of the total amount.
[0023]
Then, when the boot body molding material as described above is melted to, for example, 190 to 200 ° C. and injected from the material injection path 8a, the molding material passes through the grooves 8b and 8c and the gate groove 8g and enters the cavity space C. At the same time as the injection, the thermally expandable microcapsule expands and foams to produce the boot body 2, and simultaneously with the production of the boot body 2, the bottom part 3 is integrated into the boot body 2. The
And this foaming is uniformly foamed to the surface layer even in the thin part of the product, and since there is almost no secondary foaming, the cooling time is short.
If the molded product is cooled and then taken out of the mold, a foamed resin boot 1 as shown in FIG. 1 is manufactured.
[0024]
And even if the foamed resin boot 1 manufactured as described above continues to wear for a long period of time, the shoe sole is less likely to wear, durability can be improved, and the hardness of the sole portion can be increased, In addition, because it is excellent in slip resistance, it is comfortable to wear.
[0025]
In the above embodiment, in order to integrate the main bottom part 3 and the boot body 2, the press main body part 3 is positioned and set on the bottom mold 7 and the boot main body 2 is injection molded. Alternatively, after the main bottom part 3 is injection-molded using a dummy mold, the so-called two-color molding may be performed in which the boot body 2 is injection-molded by remolding.
[0026]
The present invention is not limited to the above embodiment. What has substantially the same configuration as the matters described in the claims of the present invention and exhibits the same operational effects belongs to the technical scope of the present invention.
For example, the materials, shapes, etc. of the boot body 2 and the bottom part 3 are examples.
[0027]
As described above, the method for manufacturing a foamed resin boot according to the present invention is such that at least the heel part and the stepping part are solid in the sole part of the foamed resin boot body formed by foaming the whole by injection molding. The boot body is composed of a cylindrical thin-walled molded part and a thick-walled molded part that forms a sole part continuous to the thin-walled molded part. Since the foam molding material using the capsule is filled and molded from the thin molding part to the thick molding part at the upper part of the boot body, it can be foamed up to the part in contact with the molding die for further weight reduction. At the same time, foaming can be performed more uniformly, secondary foaming can be suppressed, cooling time can be shortened, and the sole part of lightweight boots can be made harder and wear resistance can be improved. Benefit can be.
At this time, if a part that has been press-molded in advance as the bottom part is integrated with the boot body at the time of injection molding of the boot body, it can be efficiently manufactured.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an example of a foamed resin boot according to the present invention. FIG. 2 is a bottom view, (a) is a side view, and (b) is a bottom view. FIG. In the figure, (a) is the state before setting the bottom part, (b) is the state where the bottom part is set. [Fig. 4] An explanatory diagram of the state where the injection mold is clamped.
DESCRIPTION OF SYMBOLS 1 ... Foamed resin boot, 2 ... Boot body, 3 ... Outsole part, 4 ... Injection mold.

Claims (2)

A manufacturing method of a foamed resin boot having a boot body formed by injection molding and a solid bottom part integrated with at least a heel portion and a stepping portion of a sole portion of the boot body, wherein the boot body is The thin-walled molded part and the thick-walled molded part that forms the sole part continuous to the thin-walled molded part. A method for producing a foamed resin boot, characterized by molding a boot body which is injected from a molded portion toward a thick molded portion and foamed as a whole. The method for manufacturing a foamed resin boot according to claim 1, wherein the main bottom part is press-molded in advance and integrated with the boot body during injection molding of the boot body .

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