阅读说明：本技术 树脂成型体和鞋底用构件的制造方法 (Resin molded body and method for producing member for shoe sole ) 是由 立石纯一郎 山出贵士 泽田大辅 大崎隆 原野健一 于 2018-01-31 设计创作，主要内容包括：一种树脂成型体的制造方法,其包含：导入工序,其中,将多个树脂发泡颗粒与加热介质化物质一同导入成型模具内；成型工序,其中,在上述导入工序之后,将上述成型模具加热至上述加热介质化物质能够汽化的温度,由此,得到包含上述多个树脂发泡颗粒的树脂成型体。(A method for producing a resin molded body, comprising: an introduction step of introducing the plurality of resin foamed particles into a molding die together with a heating medium substance; and a molding step of heating the mold to a temperature at which the heating medium substance can be vaporized after the introducing step, thereby obtaining a resin molded body including the plurality of resin expanded particles.)

1. A method for producing a resin molded body, comprising:

an introduction step of introducing the plurality of resin foamed particles into a molding die together with a heating medium substance;

and a molding step of heating the molding die to a temperature at which the heating medium substance can be vaporized after the introducing step, thereby obtaining a resin molded body including the plurality of resin expanded particles.

2. The method for producing a resin molded body according to claim 1, wherein,

the heating mediator is water.

3. The method for producing a resin molded body according to claim 1 or 2, wherein,

in the introducing step, a thermoplastic resin composition is further introduced into the molding die.

4. The method for producing a resin molded body according to claim 3,

the thermoplastic resin composition contains a polyolefin resin or a polystyrene resin, and the plurality of resin expanded particles are composed of a resin composition containing a polyolefin resin.

5. The method for producing a resin molded body according to claim 3,

the thermoplastic resin composition contains a polyurethane resin, and the plurality of resin foamed particles are composed of a resin composition containing a polyurethane resin.

6. A method for manufacturing a member for a shoe sole, characterized by comprising the method according to any one of claims 1 to 5.

Technical Field

The present invention relates to a method for producing a resin molded article and a member for a shoe sole, and more particularly, to a method for producing a resin molded article containing a plurality of resin foamed particles and a method for producing a member for a shoe sole including the method for producing a resin molded article.

Background

Conventionally, as a resin molded article, a resin foam formed by welding a plurality of resin foamed particles made of polystyrene, polyurethane, or the like has been known. Such a resin foam is excellent in impact absorption, heat insulation, and sound absorption, and therefore, is used in various applications requiring these properties.

For example, patent documents 1 to 3 disclose a sole member provided with a resin foam. The member for a shoe sole is required to have excellent cushioning properties, and therefore, in the member for a shoe sole using the resin foam, the cushioning properties of the member for a shoe sole can be effectively improved.

Generally, the resin foam is produced by introducing a plurality of resin foamed particles into a molding die, and heating and welding the plurality of resin foamed particles in the molding die.

Here, as one of the methods of heating the plurality of resin expanded beads in the mold, a method of heating the mold and transferring heat to the plurality of resin expanded beads through the mold may be considered. However, the resin expanded particles have a feature of high heat insulation, in other words, difficulty in transferring heat, and therefore, in the case of using this method, there is a problem that heat is difficult to transmit to the resin expanded particles in a portion of the molding die which is located away from the surface of the molding die.

In order to avoid such a problem, as a method of heating a plurality of resin expanded beads in a molding die, as described in patent documents 1 to 3, a method of feeding high-temperature steam from the outside into the molding die and heating the plurality of resin expanded beads by the steam is known.

However, this method requires additional equipment for feeding steam from the outside into the molding die, and therefore has a problem of an increase in the production cost of the resin foam. Further, since it is necessary to provide a steam inlet for introducing steam from the outside to the molding die into which the plurality of resin composite materials are introduced, there is also a problem that the degree of freedom in designing the molding die is lowered. Further, since the resin composition constituting the resin expanded beads may intrude into the steam inlet due to the pressure generated in the molding die during molding, there is also a problem that a projection corresponding to the steam inlet is formed on the surface of the produced resin foam.

Disclosure of Invention

Problems to be solved by the invention

In view of the above problems, an object of the present invention is to provide a method for producing a resin molded article in which heat can be transferred relatively uniformly into a mold by a simple method when a resin molded article including a plurality of resin expanded particles is molded, and a method for producing a sole member including the method for producing a resin molded article.

Technical scheme for solving problems

The present inventors have found that the above-mentioned problems can be solved by introducing a substance that forms a heat medium by vaporization by heating into a molding die in advance when a resin molded article containing a plurality of resin expanded particles is subjected to heat molding.

That is, the method for producing a resin molded article according to the present invention includes: an introduction step of introducing the plurality of resin foamed particles into a molding die together with a heating medium substance; and a molding step of heating the mold to a temperature at which the heating medium substance can be vaporized after the introducing step, thereby obtaining a resin molded body including the plurality of resin expanded particles.

In the method for producing a resin molded article according to the present invention, the heating medium substance is preferably water.

In one embodiment of the method for producing a resin molded article according to the present invention, the thermoplastic resin composition is further introduced into a molding die in the introducing step.

In the above aspect of the method for producing a resin molded article according to the present invention, for example, the thermoplastic resin composition contains a polyolefin resin or a polystyrene resin, and the plurality of resin expanded particles are composed of a resin composition containing a polyolefin resin.

In the above aspect of the method for producing a resin molded article according to the present invention, for example, the thermoplastic resin composition contains a polyolefin resin or a polystyrene resin, and the plurality of resin expanded particles are composed of a resin composition containing a polyolefin resin.

The method for manufacturing a sole member according to the present invention includes the method for manufacturing the resin molded body.

Drawings

Fig. 1 is a photograph showing a cross section of a resin composite produced by the method of the comparative example.

Detailed Description

Embodiments of the method for producing the resin molded article and the footwear member according to the present invention will be described below. However, the following embodiments are merely examples. The present invention is not limited to the following embodiments.

(first embodiment)

A method for producing a resin molded body according to a first embodiment of the present invention includes:

an introduction step of introducing the plurality of resin foamed particles into a molding die together with a heating medium substance;

and a molding step of heating the mold to a temperature at which the heating medium substance can be vaporized after the introducing step, thereby obtaining a resin molded body including the plurality of resin expanded particles.

In the present embodiment, prior to the introduction step, a plurality of resin expanded beads are first prepared. In the present specification, the resin expanded particles mean expanded particles composed of a resin composition and having a plurality of pores in the resin composition.

The plurality of resin expanded particles may be formed of any resin composition that can be formed into resin expanded particles. For example, the resin composition may contain resins such as polyolefin (e.g., Polyethylene (PE) and polypropylene (PP)), Thermoplastic Polyurethane (TPU), Polystyrene (PS), ethylene-propylene rubber (EPDM), polyether block amide (PEBA), Polyester (PEs), ethylene-vinyl acetate (EVA), and Polyamide (PA).

The resin composition may preferably contain a thermoplastic resin such as a polyolefin resin, a polystyrene resin, or a thermoplastic polyurethane resin.

When the resin composition is a polyolefin resin, the polyolefin resin may be, for example, low-density polyethylene, medium-density polyethylene, an ethylene- α -olefin copolymer, an ethylene-propylene rubber, polypropylene, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, or the like, and is preferably an elastomer having an ethylene crystal phase as a hard segment. More specifically, the polyolefin-based resin is preferably an elastomer having an ethylene crystal phase at one or both ends of a polymer chain, or a block copolymer having ethylene crystal phases alternating with ethylene- α -olefin copolymerization portions.

When the resin composition is a polystyrene-based resin, the polystyrene-based resin may be, for example, a styrene-ethylene/butylene-styrene block copolymer (SEBS), a styrene-butadiene-butylene-styrene block copolymer (SBBS), a hydrogenated polystyrene-poly (styrene/butadiene) -polystyrene (SSEBS), a styrene-butylene-styrene block copolymer (SBS), a styrene-isoprene block copolymer (SIS), a styrene-ethylene-propylene-styrene block copolymer (SEPS), or the like, and SEBS, SSEBS, SIS are more preferable.

When the resin composition is a thermoplastic polyurethane resin, the thermoplastic polyurethane resin may be, for example, polyether polyurethane, polyester polyurethane, or the like, and polyether polyurethane is more preferable.

The resin composition may contain a thermoplastic polyamide resin. The polyamide resin may preferably be polyether block amide (PEBA) composed of a hard segment containing a polyamide unit and a soft segment containing a polyether unit.

The polyamide unit constituting the hard segment may be, for example, polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, or the like, and is preferably polyamide 11 or polyamide 12. These polyamide units may be used alone or in combination of two or more.

The polyether unit constituting the soft segment may be, for example, a polyvinyl ether glycol, a polypropylene ether glycol, a polytetramethylene ether glycol, a polyhexamethylene ether glycol, or the like, and more preferably a polytetramethylene ether glycol. These polyether units may be used alone or in combination of two or more.

The resin composition may be a thermosetting resin. The thermosetting resin is not particularly limited, and for example, a thermosetting polyurethane elastomer, an acrylic elastomer, a crosslinked rubber, a silicone elastomer, or a fluorine elastomer can be used, and a polyurethane elastomer is preferable.

These resins may be used alone or in combination of two or more.

The elastic modulus of the resin composition is not particularly limited, and for example, the initial elastic modulus at 23 ℃ may be 10MPa or more and 400MPa or less.

In the present specification, the elastic modulus (young's modulus) of various materials and members such as the resin composition means the compressive modulus of elasticity at 23 ℃. The measurement of the compression modulus of elasticity can be performed, for example, by the method described in the examples described later.

As the value of the elastic modulus, those based on JIS K7244-4: 1999 (same as ISO 6721-4: 1994), the value of storage modulus at 23 ℃ measured at a frequency of 10Hz in the measurement mode "sine wave distorted tension mode". For example, the storage elastic modulus can be measured under the following conditions using a dynamic viscoelasticity measuring apparatus "Rheogel-E4000" manufactured by UBM (strain) as a measuring apparatus.

Measurement mode: stretching mode of sine wave distortion

Frequency: 10Hz

Distance between chucks: 20mm

Loading: automatic static load

Dynamic strain: 5 μm

Temperature rise rate: 2 ℃/min

Test piece: long strip with length of 33 plus or minus 3mm, width of 5 plus or minus 1mm and thickness of 2 plus or minus 1mm

The resin composition may contain other optional components, and may further contain chemicals such as a pigment, an antioxidant, and an ultraviolet absorber.

The plurality of resin expanded particles can be produced from the resin composition by a conventionally known method. Specifically, the resin expanded beads constituting the resin expanded beads may be produced, for example, by an impregnation method in which resin beads containing no foaming agent are produced and then impregnated with a foaming agent, or by an extrusion method in which the resin composition containing a foaming agent is extruded into cooling water and granulated.

In the impregnation method, first, the resin composition is molded to produce resin particles. Next, the resin particles, the foaming agent, and the aqueous dispersant are introduced into an autoclave, and stirred with heat and pressure applied thereto, whereby the foaming agent is impregnated into the resin particles. The resin foamed particles can be obtained by foaming the impregnated foaming agent.

In the extrusion method, for example, the resin composition and the blowing agent are added to an extruder having a die provided with a plurality of small holes at the tip thereof, and melt-kneaded. The melt-kneaded product was extruded into a strand shape from the die, and immediately introduced into cooling water to be solidified. The resin expanded beads can be obtained by cutting the cured product thus obtained into a predetermined length.

The blowing agent used in the above method is not particularly limited, and may be, for example, a chemical blowing agent or a physical blowing agent.

The chemical blowing agent is a blowing agent that generates a gas by a chemical reaction or thermal decomposition. Examples of such chemical blowing agents include inorganic chemical blowing agents such as sodium bicarbonate and ammonium carbonate, and organic chemical blowing agents such as azodicarbonamide.

The physical foaming agent is liquefied gas, supercritical fluid, etc., and is foamed by reducing pressure or heating. Examples of such physical blowing agents include aliphatic hydrocarbons such as butane, alicyclic hydrocarbons such as cyclobutane, and inorganic gases such as carbon dioxide, nitrogen, and air.

In the present embodiment, in the production of the resin expanded beads, an impregnation method in which the resin composition is expanded by a supercritical fluid is particularly preferably used. In this case, since the resin composition can be dissolved in the supercritical fluid at a relatively low temperature, a high temperature for melting the resin composition is not required. This is particularly advantageous when the resin composition contains a resin having a high melting point such as a polyamide elastomer. In addition, this method also has an advantage of suppressing generation of harmful gas from the foaming of the chemical foaming agent because the chemical foaming agent is not used.

The density and expansion ratio of the plurality of resin expanded beads are not particularly limited.

The shape and size of the plurality of resin foamed particles are not particularly limited. The shape of the resin expanded beads is preferably spherical. In this case, the volume average particle diameter D50 (median diameter) of the resin expanded particles may preferably be in the range of 1 to 20mm in diameter, and more preferably in the range of 2 to 10mm in diameter.

In the present specification, the particle diameter of the resin particles is a value obtained by measuring the major axis of the particles using a microscope.

The initial elastic modulus of the expanded beads is not particularly limited, and when the resin molded article molded in the subsequent molding step is a member for forming a member for a shoe sole, the initial elastic modulus at 23 ℃ of the expanded beads may be preferably 0.2MPa to 20MPa, and more preferably 0.3MPa to 10 MPa. In this case, the initial rigidity and the amount of strain of the resin composite can be set to values more suitable for the sole member.

The initial elastic modulus of the expanded beads contained in the resin composite can be measured, for example, by the method described in the examples described below.

Next, in the introducing step, the plurality of resin foamed particles are introduced into a molding die together with the heating medium substance.

The heating mediator is a substance that is vaporized by heating in the subsequent molding step and becomes a heating medium in a vapor state. Examples of the heating mediator include water and organic substances such as hydrocarbon materials. Among them, water is preferable as the heating medium, and water is easily vaporized by heating molding, has little adverse effect on the resin expanded beads, and has little effect on the human body and the environment.

The heating medium material may be a material having a boiling point or sublimation point not higher than the heating temperature in the subsequent molding step, and may be a liquid or solid at the temperature of the introduction step (for example, normal temperature).

In the introduction step of the present embodiment, a binder may be used as appropriate in addition to the plurality of resin expanded beads and the heat transfer material in order to integrate the plurality of resin expanded beads in the subsequent molding step.

Examples of the binder include a surface modifier, a binder other than the resin composition constituting the resin expanded beads such as urethane, and the like. These binders may be used alone or in combination of two or more.

After the introducing step, in the molding step, the molding die into which the plurality of resin foam particles and the heating medium substance are introduced is heated to a temperature at which the heating medium substance can be vaporized. Thus, in the present embodiment, the plurality of foamed resin particles are integrated by being thermally melted with each other, and a foamed resin body in which the plurality of foamed resin particles are integrated can be obtained as a resin molded body.

In the molding step of the present embodiment, when the plurality of resin foamed particles are heated to be integrated, the heating medium substance is vaporized in the molding die, and thus the vapor of the heated heating medium substance spreads throughout the entire molding die. Accordingly, heat can be transferred relatively uniformly to all of the plurality of resin foamed particles (that is, not only to the resin foamed particles located in the vicinity of the inner surface of the molding die but also to the resin foamed particles located in the vicinity of the center of the molding die away from the inner surface of the molding die) in the molding die via the vaporized heat medium material.

The heating temperature in the molding step is not particularly limited as long as the material of the heating medium can be vaporized.

However, the heating temperature is most preferably a temperature at which the plurality of resin foamed particles can be chemically stable while maintaining the shape. That is, the heating temperature is preferably in the range of-60 ℃ to +40 ℃ as compared with the melting point or softening point of the resin composition constituting the plurality of resin expanded particles.

The heating temperature may be appropriately adjusted depending on the heating medium and the type of the resin composition constituting the plurality of resin expanded beads. For example, in the case where the heating medium is water and the resin composition contains a polyolefin resin, the heating temperature may be in the range of 100 to 160 ℃. In addition, when the heating medium is water and the resin composition contains PEBA, the heating temperature may be in the range of 100 to 180 ℃.

In the molding step, pressure may be appropriately applied to the mold in addition to heating. For example, in the molding step, a pressure of 1 to 30MPa may be applied.

According to the method of the present embodiment, the resin foam obtained by integrating the plurality of resin foamed particles can be produced as the resin molded article by a simple method by heating the plurality of resin foamed particles together with the heating medium substance.

In this method, the entire plurality of resin foamed particles are heated relatively uniformly, and therefore, the resin foamed body in which the resin particles are bonded to each other relatively firmly from the surface to the inside of the obtained resin foamed body can be obtained.

The resin foam (resin molded article) produced by the method of the present embodiment is excellent in impact absorption, heat insulation, sound absorption, and the like, and therefore can be used in various applications requiring these properties. For example, the resin foam can be used for a part or all of a member for a shoe sole, a container, a cushioning material, a heat insulating material, and a sound absorbing material.

The resin foam can be preferably used as a member forming a part or all of the sole member. The sole member may be, for example, a member forming a part or all of an insole, a midsole, or an outsole. The resin foam may be more preferably a member that forms a part or all of a midsole that is a member for a sole.

The method of the present embodiment may be included in a method for producing a member for such applications, for example, a method for producing a member for a shoe sole. In this case, in the molding step, the member entirely formed of the resin foam may be directly produced using a molding die having an internal shape corresponding to the shape of the member (for example, a member for a shoe sole).

In the present embodiment, when a plurality of types of resin expanded beads having different particle diameters and rigidities are introduced into a molding die in the introduction step, the positions of the resin expanded beads can be determined in different regions in the molding die according to the particle diameters and rigidities. For example, in the case where the resin foam is a member for a shoe sole, the resin foam particles having a small particle diameter may be disposed at a position on the inner side of the foot after being molded in the mold, or the resin foam particles having a large particle diameter may be disposed at a position on the inner side of the foot after being molded in the mold. The resin expanded beads thus arranged in the introduction step are integrated in the molding step described later to form a resin foam capable of adjusting the arrangement of the resin expanded beads in the resin foam.

In this manner, by adjusting the arrangement within the resin foam body in accordance with the particle diameter and rigidity of the resin foam particles, it is possible to form a resin foam body having different rigidities depending on the region.

(second embodiment)

Next, a second embodiment of the present invention will be explained.

The method for producing a resin composite according to a second embodiment of the present invention is the same as the first embodiment except that in the introducing step of the first embodiment, a thermoplastic resin composition is introduced into a molding die in addition to the plurality of resin foamed particles and the heating medium substance.

The thermoplastic resin composition is not particularly limited, and includes, for example, a polystyrene resin, a polyolefin resin, or a thermoplastic polyurethane resin. These resin components may be selected from, for example, the polystyrene resin, the polyolefin resin, or the thermoplastic polyurethane resin that can be used as the plurality of resin foamed particles.

These resin components may be used alone or in combination of two or more.

As the resin component contained in the thermoplastic resin composition, a polystyrene-based elastomer is preferably selected. In this case, the initial elastic modulus of the above elastomer can be adjusted to an appropriate value by appropriately adjusting the content of the styrene component (styrene content) contained in the polystyrene-based elastomer. Thus, the initial rigidity and the amount of strain of the sole member can be adjusted to appropriate values.

The thermoplastic resin composition may further comprise a plasticizer. In this case, the thermoplastic resin composition may be a polymer gel obtained by gelling a resin. Examples of the plasticizer include paraffins, naphthenes, aromatics, and olefins, and paraffins are more preferable.

When the thermoplastic resin composition contains a plasticizer, the content of the plasticizer contained in the thermoplastic resin composition is preferably 10 to 300% by weight of the entire thermoplastic resin composition.

The thermoplastic resin composition preferably contains a resin component containing a resin component having high weldability with the plurality of resin foamed particles. In this case, the thermoplastic resin composition and the resin foamed particles can be firmly bonded without using bonding elements such as a binder in the subsequent molding step.

For example, in the case where the resin foamed particles are composed of a polyolefin resin, the thermoplastic resin composition may contain a polyolefin elastomer or a polystyrene elastomer. When the resin foamed particles are made of a polyurethane resin, the thermoplastic resin composition may contain a polyurethane elastomer.

The thermoplastic resin composition is preferably a thermoplastic resin composition having sufficient fluidity at a temperature at which the resin composition constituting the plurality of resin foamed particles is chemically stable while maintaining its shape. In this case, the plurality of resin expanded particles may be dispersed in the thermoplastic resin composition in a subsequent molding step.

For example, when the resin composition constituting the plurality of resin foamed particles also contains a thermoplastic resin, the thermoplastic resin composition is preferably a thermoplastic resin composition having sufficient fluidity at a temperature lower than the melting point or softening point of the resin composition constituting the plurality of resin foamed particles. Specifically, the thermoplastic resin composition preferably has a complex viscosity of 0.1MPa/s or less at the above temperature.

When the thermoplastic resin composition is a polyolefin elastomer, the polyolefin elastomer preferably has a complex viscosity of 0.05MPa/s or less at 100 ℃.

In the present specification, the complex viscosity of the resin composition means a value based on JIS K7244-4: 1999 (same as ISO 6721-4: 1994) measured at a frequency of 10Hz in the measurement mode "sine wave distorted stretching mode".

For example, the complex viscosity of the resin composition can be measured under the same conditions as those used in the method for measuring the storage elastic modulus.

The thermoplastic resin composition may contain other optional components, and may further contain chemicals such as a pigment, an antioxidant, and an ultraviolet absorber.

The initial elastic modulus of the thermoplastic resin composition is not particularly limited, and when the resin molded article molded in the subsequent molding step is a member forming a member for a shoe sole, the initial elastic modulus at 23 ℃ may be preferably 0.1MPa or more and 5MPa or less, more preferably 0.2MPa or more and 3MPa or less, and still more preferably 3MPa or less. In this case, the initial rigidity and the amount of strain of the resin composite can be set to values more suitable for the sole member. If the initial elastic modulus at 23 ℃ of the elastomer is less than 0.1MPa, the durability and mechanical strength of the sole member may be insufficient.

In the introduction step of the present embodiment, the thermoplastic resin composition is mixed with the plurality of resin foamed particles and introduced into the molding die. Preferably, the thermoplastic resin composition can be molded into a pellet by a conventionally known method and then mixed with the plurality of resin foamed particles. The shape and size of the thermoplastic resin composition molded into a pellet shape are not particularly limited.

However, the method for mixing the thermoplastic resin composition with the plurality of resin foamed particles is not particularly limited, and the thermoplastic resin composition may be mixed with the plurality of resin foamed particles by any method.

In the introduction step of the present embodiment, the blending ratio of the thermoplastic resin composition to the resin expanded beads is appropriately adjusted according to the physical properties (for example, initial rigidity and amount of strain) required for the resin molded article to be produced, whereby various resin composites having a wide range of physical properties can be produced in the subsequent molding step.

For example, the amount of the thermoplastic resin composition to be introduced may be 5 to 90% (by volume) relative to the total amount of the thermoplastic resin composition and the resin expanded beads. In this case, the resin composite can be appropriately reduced in weight, and the elastic recovery of the resin composite can be appropriately improved.

In the next molding step of the present embodiment, the molding die is heated to a temperature at which the material of the heating medium can be vaporized, as in the first embodiment.

In the present embodiment, in the molding step, the heating medium is heated to a temperature at which the substance of the heating medium can be vaporized and the thermoplastic resin composition exhibits sufficient fluidity, whereby a resin composite in which the plurality of resin expanded particles are dispersed in a matrix composed of the thermoplastic resin composition can be obtained as a resin molded body.

The heating temperature is preferably a temperature at which the complex viscosity of the thermoplastic resin composition is 0.1MPa/s or less, in addition to the heating temperature which is preferable in the molding step of the first embodiment. For example, when the heating medium is water and both the thermoplastic resin composition and the resin composition constituting the plurality of resin foamed particles contain a polyolefin resin, the heating temperature may be in the range of 100 to 160 ℃.

According to the method of the present embodiment, since the entire inside of the molded body is heated relatively uniformly, the thermoplastic resin composition having improved fluidity by heating can sufficiently flow in the molded body, and the thermoplastic resin composition can flow between the plurality of resin expanded particles. Thus, according to the method of the present embodiment, a resin composite in which the thermoplastic resin composition is impregnated between the plurality of resin expanded particles can be produced as a resin molded article by a simple method.

The resin composite (resin molded article) produced by the method of the present embodiment is composed of two or more resin compositions including a resin composition constituting resin expanded particles and the thermoplastic resin composition.

The resin composite of the present embodiment may have a region composed of the thermoplastic resin composition in the matrix composed of the resin expanded particles, or may have a region composed of one or more resin expanded particles in the matrix composed of the thermoplastic resin composition. That is, the resin composite of the present embodiment may be a resin foam in which a plurality of the resin foamed particles are directly bonded and integrated with each other, and a resin composite in which a plurality of pores formed in the resin foam are filled with the thermoplastic resin composition, or a resin composite in which a plurality of the resin foamed particles are bonded and integrated with each other via the thermoplastic resin composition.

The resin composite produced by the method of the present embodiment can also be used for various applications. For example, the resin composite can be used for a part or all of a member for a shoe sole, a sound absorbing material, a cushioning material, a vibration isolating material, or a damping material.

The resin composite is preferably used as a member forming part or all of a member for a sole such as an insole, a midsole, or an outsole, and more preferably as a member forming part or all of a midsole. The member for a sole formed of the resin composite has a smaller initial rigidity, a larger amount of strain in normal use, and a smaller amount of strain under a high load, as compared with a conventional member for a sole formed of a resin foam, and is sufficiently lightweight as a member for a sole and has a high elastic recovery property. Therefore, the shoe provided with the sole member exhibits a soft feeling of treading, has sufficient lightweight, can suppress excessive deformation, can exert high cushioning properties, and has excellent durability. The term "under high load" as used herein means that the sole member is subjected to a stress of approximately 0.6 to 1.0 MPa.

The method of the present embodiment may also be applied to a method for manufacturing a sole member or the like.

In the present embodiment, the resin composite can be produced by adjusting the blending ratio of the plurality of resin expanded particles to the thermoplastic resin composition for each predetermined region in advance in accordance with the physical properties (for example, initial rigidity and amount of strain) required for the resin composite in the introduction step, and integrating them in the subsequent molding step.

For example, in the case where the resin composite is a sole member and the thermoplastic resin composition is made of an elastomer, the proportion of the thermoplastic resin composition may be made larger in a region where a large load is likely to be applied to the sole member, specifically, in a region of a heel region or a forefoot region, than in other regions. If the proportion of the thermoplastic resin composition in the heel part of the sole member is large, the impact-absorbing effect due to the properties of the thermoplastic resin composition can be effectively exhibited even when a large load is applied to the heel part during landing in various sports. In addition, if the blending ratio of the thermoplastic resin composition in the front foot portion of the sole member is large, excessive deformation of the sole can be suppressed during the cutting operation, and smooth weight movement can be performed.

On the other hand, in a region where a large load is not likely to be applied in the sole member, the blending ratio of the thermoplastic resin composition may be made smaller than the blending ratio of the resin composition in the other region. For example, since it is not easy to apply a large load to the midfoot portion, the midfoot portion of the sole member may have a certain degree of cushioning properties. Therefore, the blending ratio of the thermoplastic resin composition in the midfoot region can be reduced, and the sole member can be made lightweight.

As described above, by adjusting the blending ratio of the plurality of resin expanded particles to the thermoplastic resin composition for each predetermined region, a resin composite having different initial rigidity and strain amount for each region can be formed.

In addition, in the molding step, since the viscosity of the thermoplastic resin composition can be sufficiently reduced, steam may be entrained in the thermoplastic resin composition. By doing so, the thermoplastic resin composition sandwiched between the resin expanded particles in the obtained resin composite can be brought into a micro-expanded state (the volume ratio of air is lower than that in the expanded state of the resin expanded particles).

As described above, the method for producing a resin molded body according to each embodiment of the present invention includes: an introduction step of introducing the plurality of resin foamed particles into a molding die together with a heating medium substance; and a molding step of heating the mold to a temperature at which the heating medium substance can be vaporized after the introducing step, thereby obtaining a resin molded body including the plurality of resin expanded particles. Therefore, when the resin molded body is molded, heat can be transferred relatively uniformly into the molding die by a simple method. Therefore, the resin molded body can be produced by heating and molding the resin molded body uniformly from the surface to the inside of the resin molded body.

In the conventional method for producing a resin molded article, since it is necessary to use a molding die having a steam inlet for introducing steam, a resin composition or the like constituting resin expanded beads during molding enters the steam inlet due to pressure generated in the molding die, and therefore, there is a problem that protrusions corresponding to the steam inlet are easily formed on the surface of the resin molded article.

In particular, in the case where the resin molded article is a sole member such as a midsole, if the protrusions as described above are present on the adhesion surface with the outsole or the upper, it is difficult to exhibit sufficiently excellent adhesion between the both, and this problem is further serious.

In contrast, the method for producing a resin molded body according to the present embodiment has an advantage that the formation of such a protrusion can be suppressed. Therefore, this production method is particularly advantageous in producing a resin molded product for forming a sole member, because it is easy to obtain a sole member such as a midsole that exhibits excellent adhesion to an outsole, an upper, and the like.

Further, in the conventional method for producing a resin molded article, if an additional thermoplastic resin composition is introduced between the resin expanded beads and the molding step is performed at a temperature at which the thermoplastic resin composition exhibits sufficient fluidity as in the second embodiment of the present invention, there is a possibility that the thermoplastic resin having high fluidity flows out from the steam inlet.

In contrast, in the second embodiment of the present invention, since a molding die having no steam inlet is used in the molding step, the possibility of the thermoplastic resin composition flowing out from the steam inlet can be suppressed.

That is, in the present embodiment, selection of temperature conditions in the molding step is increased as compared with the case of using a molding die having a steam inlet.

In addition, the method for manufacturing a member for a sole according to each embodiment of the present invention can manufacture a member for a sole, a part or all of which is formed of the resin molded body manufactured as described above.

Further, although the above-mentioned items which are not directly described are not described in detail, the present invention can be suitably applied as the conventionally known technical items related to the sole member.