JP6869017B2 - Urethane-based thermoplastic elastomer foamed particle molded product - Google Patents

Description

The present invention relates to a urethane-based thermoplastic elastomer foamed particle molded product.

In general, urethane-based thermoplastic elastomers are excellent in wear resistance, cold resistance, and impact resilience. In addition, urethane-based thermoplastic elastomers are positioned as engineering elastomers because of their high mechanical strength, and are used in various applications such as daily necessities, electrical appliances parts, sporting goods, automobile parts, and anti-vibration materials in the field of construction and civil engineering. Is beginning to be done.

This urethane-based thermoplastic elastomer foam molded product has excellent properties such as abrasion resistance and impact resilience, can be made lighter and more flexible, and satisfies the basic physical properties required for a foam molded product. Therefore, further development of applications in sports equipment, automobile parts, etc. is expected in the future. In-mold molding of foamed particles can produce foamed particle molded products of various shapes according to the shape of the mold. Therefore, in recent years, urethane-based thermoplastic elastomers have also been molded in-mold for urethane-based thermoplastic elastomers. It is required to produce a foamed particle molded product of.

A foamed particle molded product of a urethane-based thermoplastic elastomer is disclosed in, for example, Patent Document 1.

U.S. Patent Application Publication No. 2012/0329892

Urethane-based thermoplastic elastomer foam particles have a strong repulsive force, but it is difficult to control the secondary foamability during in-mold molding, and the physical properties are likely to deteriorate due to heating. Therefore, in-mold molding of urethane-based thermoplastic elastomer foamed particles has been difficult.
Further, in recent years, with the development of applications of foamed particle molded products for soles and the like, there has been a demand for molded products having excellent surface smoothness and designability and having a good appearance. However, since the conventional urethane-based thermoplastic elastomer foamed particle molded product is difficult to mold in-mold as described above, the surface of the molded product has a three-dimensional uneven shape (turtle shell pattern) due to the shape of the foamed particles. In addition, fine voids generated between the foamed particles may appear, leaving room for improvement in the appearance.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a urethane-based thermoplastic elastomer foamed particle molded product having a good appearance without impairing the physical characteristics of the molded product.

That is, the present invention provides the following [1] to [10].
[1] An in-mold molded body of urethane-based thermoplastic elastomer foamed particles, wherein a melt-cured layer in which the foamed particles are melted and cured is formed on at least a part of the surface of the molded body. A urethane-based thermoplastic elastomer foamed particle molded product, characterized in that the average thickness of the cured layer is 0.05 mm or more and 0.4 mm or less.
[2] The urethane-based thermoplastic elastomer foamed particle molded product according to [1], wherein the apparent density of the molded product is 100 g / L or more and 350 g / L or less.
[3] The foamed particles constituting the molded product are foamed particles based on a urethane-based thermoplastic elastomer having a type A durometer hardness of 95 or less, according to [1] or [2]. The urethane-based thermoplastic elastomer foamed particle molded product described.
[4] The urethane-based thermoplastic elastomer foamed particle molded product according to any one of [1] to [3], wherein the coefficient of variation of the thickness of the melt-cured layer is 30% or less.
[5] The urethane-based thermoplastic elastomer foamed particle molded product according to any one of [1] to [4], wherein the melt-cured layer is formed on at least one surface of the molded product.
[6] The urethane-based thermoplastic elastomer foamed particle molded product according to any one of [1] to [5], wherein the molded product contains a colorant.
[7] The urethane-based thermoplastic elastomer foamed particle molding according to any one of [1] to [6], wherein a decorative surface having an uneven pattern is formed on the surface of the melt-cured layer. body.
[8] The urethane-based thermoplastic elastomer foamed particle molded product according to any one of [1] to [6], wherein a smooth surface is formed on the surface of the melt-cured layer.
[9] A sole using the urethane-based thermoplastic elastomer foamed particle molded product according to any one of [1] to [8].
[10] The sole according to [9], wherein the melt-cured layer is formed on at least a side surface of the sole.

According to the urethane-based thermoplastic elastomer foamed particle molded product of the present invention, by forming a melt-cured layer having a specific thickness on the surface of the molded product, urethane-based thermoplastic molding having a good appearance without impairing the physical properties of the molded product. An elastomer foamed particle molded product can be obtained.

The urethane-based thermoplastic elastomer foamed particle molded product of the present invention (hereinafter, also simply referred to as “foamed particle molded product” or “molded product”) is obtained by in-mold molding of urethane-based thermoplastic elastomer foamed particles. In addition, foamed particles are melted on at least a part of the surface of the molded product, and a cured melt-cured layer is formed with a specific average thickness.

The average thickness of the melt-cured layer formed on the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is 0.05 mm or more and 0.4 mm or less. By setting the average thickness of the melt-cured layer within the above range, three-dimensional uneven shapes and fine voids due to the shape of the foamed particles are generated on the surface of the molded body while maintaining the fused state inside the molded body. It is possible to obtain a molded product having a good appearance. Further, by setting the average thickness of the melt-cured layer in the above range, the mechanical properties such as the compressed physical properties do not change significantly as compared with the molded product in which the melt-cured layer is not formed. It is possible to obtain a molded product having.
From the viewpoint of suppressing the generation of three-dimensional uneven shape and fine voids, the average thickness of the melt-cured layer is preferably 0.07 mm or more, more preferably 0.10 mm or more, still more preferably 0.12 mm or more. Particularly preferably, it is 0.15 mm or more. Further, from the viewpoint of controlling the mechanical properties of the molded product, the average thickness of the melt-cured layer is preferably 0.35 mm or less, more preferably 0.32 mm or less, and particularly preferably less than 0.30 mm.

Further, the coefficient of variation of the thickness of the melt-cured layer in the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 30% or less, more preferably 25% or less, and more preferably 20% or less. Is even more preferable. Within the above range, the melt-cured layer becomes homogeneous, and the surface properties and design properties of the molded product can be further improved.

The average thickness of the melt-cured layer of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is a value measured as follows. First, the foamed particle molded body is cut substantially perpendicular to the surface on which the melt-cured layer is formed so as to pass through the melt-cured layer, and an enlarged photograph of the cut surface is taken. Next, in the cut surface photograph, the air bubbles located from the outermost surface of the foamed particle molded body to the outermost part of the molded body (however, the bubble diameter in the direction perpendicular to the surface on which the melt-cured layer is formed are the average of the molded body. Bubbles with a diameter of 1/10 or less of the bubble diameter shall be ignored.) The length in the direction perpendicular to the surface on which the melt-cured layer is formed (thickness of the melt-cured layer) is 10 at equal intervals. Measure above the point. The thickness of the melt-cured layer is measured on enlarged photographs of five or more different cut surfaces, and the average thickness of the melt-cured layer is calculated by arithmetically averaging the thickness values of 50 or more points in total. Is required.
The coefficient of variation of the thickness of the melt-cured layer is a value measured as follows. First, the measured standard deviation of the thickness of the melt-cured layer is obtained, the standard deviation is divided by the average thickness of the melt-cured layer, and further multiplied by 100 to obtain the coefficient of variation (%) of the thickness of the melt-cured layer. Desired.
The standard deviation V of the thickness is calculated by the following formula.
_{V = {Σ (T i -T} av) 2 / (n-1)} 1/2 (1)
(1) a T _i measured values of the individual thickness of at least the 50 points in the formula, T _av is the average thickness of the melted and cured layer, n represents the number of measurements, respectively, sigma is calculated for individual measurements was the _{(T i -T} ^{av) 2} shows that addition all.

The ratio of the surface area of the melt-cured layer to the total surface area of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 10% or more from the viewpoint of further improving the surface area and design of the molded product. % Or more is more preferable. Further, from the same viewpoint, it is preferable that the melt-cured layer is formed on at least one surface of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention. In addition, one surface means substantially the entire surface of a certain plane in an arbitrary elevation view or plan view of a molded product.

Further, on the surface of the melt-cured layer of the urethane-based thermoplastic elastomer foam particle molded product of the present invention, a decorative surface having a fine uneven pattern such as a grain pattern can be provided. By providing the decorative surface, the design of the surface of the molded body can be further improved. Further, by providing the decorative surface, it is possible to make it more difficult for the three-dimensional uneven shape due to the shape of the foamed particles to appear on the surface.

Further, by making the surface of the melt-cured layer of the urethane-based thermoplastic elastomer foamed particle molded product a smooth surface, the design of the molded product surface can be enhanced. When the surface of the melt-cured layer is made smooth, the area ratio of the surface voids in the melt-cured layer is preferably about 15% or less, more preferably 12% or less, still more preferably 10% or less. Is.

The area ratio of surface voids can be measured as follows. First, a 3D shape measuring machine (for example, manufactured by KEYENCE CORPORATION, model number: VR-3200) is used to determine the surface shape of a certain range (for example, 24 mm × 18 mm) of the surface on which the melt-cured layer of the foamed particle molded product is formed. Measure using. The surface shape in the above range is randomly measured at 5 or more points on the surface on which the melt-cured layer is formed. For each measured range, the portion lower than the average height of the melt-cured layer surface of the foamed particle molded product by 0.1 mm or more is determined as a void, and the total number of voids existing in the measurement range is determined. Calculate each area. The area ratio (%) of surface voids is obtained by dividing ^{the arithmetic mean value [mm 2} ] of the total area of voids at five or more measurement points by the measurement area. The smaller the area ratio of the surface voids, the smaller the voids (gap between the foamed particles) in the melt-cured layer of the foamed particle molded product, and the smoother the surface appearance of the foamed particle molded product. It will be.

The urethane-based thermoplastic elastomer foamed particle molded product of the present invention can contain a colorant such as a pigment or a dye. In this case, a molded product having a more excellent design can be obtained. In particular, when the coefficient of variation of the thickness of the melt-cured layer is small and the melt-cured layer is uniformly formed, color unevenness on the surface is reduced, and a molded product having a better appearance can be obtained. Further, by forming a decorative surface with an uneven pattern on the melt-cured layer, it is possible to impart a high degree of design to the molded product.
When a colorant is used, the content of the colorant in the molded product depends on the colorant used and the like, but is approximately 0.1 part by mass with respect to 100 parts by mass of the urethane-based thermoplastic elastomer constituting the molded product. It is preferably 5 parts by mass or less, and more preferably 0.5 parts by mass or more and 3 parts by mass or less.
For example, a urethane-based thermoplastic elastomer containing a colorant is produced by adding and kneading a colorant together with a urethane-based thermoplastic elastomer in an extruder, and the foamed particles produced using this are molded in a mold. Therefore, a molded product containing a colorant can be obtained.

The apparent density of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 100 g / L or more and 350 g / L or less, more preferably 125 g / L or more and 320 g / L or less, and further preferably 150 g. It is / L or more and 300 g / L or less, and particularly preferably 150 g / L or more and 250 g / L or less. By setting the apparent density of the molded product within the above range, the lightness, flexibility and resilience of the foamed particle molded product produced by in-mold molding of the foamed particles can be further improved.
The apparent density (g / L) of the foamed particle molded body is obtained by dividing the mass W (g) of the molded body by the volume V (L) (W / V). Further, the volume V of the foamed particle molded product can be measured by a submersion method.

Further, from the viewpoint of mechanical properties such as compression characteristics, the closed cell ratio of the foamed particle molded product is preferably 60% or more, more preferably 70% or more, still more preferably 75% or more. ..
The closed cell ratio of the foamed particle compact can be measured by an air comparative hydrometer 930 manufactured by Toshiba Beckman Co., Ltd. according to the procedure C described in ASTM-D2856-70.

The average cell diameter of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 50 μm or more and 300 μm or less. Within the above range, a good molded product having excellent physical properties such as a rebound resilience can be obtained. In addition, a molded product having a good appearance can be obtained.
From the above viewpoint, the average cell diameter of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 60 μm or more and 280 μm or less, and more preferably 70 μm or more and 250 μm or less.
The average cell diameter of the molded product is a value measured as follows in accordance with ASTM D3576-77. First, the foamed particle molded body is cut to form a cut surface. On one cut surface, draw a line segment of 30 mm in any direction. The number of bubbles intersecting the line segment is measured, and the length of the line segment is divided by the number of bubbles intersecting the line segment to obtain the average chord length of the bubbles, which is further divided by 0.616 to foam. Obtain the average cell diameter of the particle compact.

From the viewpoint of the fusion property between the foamed particles, the maximum tensile stress of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 0.70 MPa or more, more preferably 0.75 MPa or more. It is more preferably 0.80 MPa or more. The upper limit of the maximum tensile stress is not particularly limited, but is approximately 1 MPa. Further, the tensile fracture elongation of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 80% or more, more preferably 100% or more, still more preferably 150% or more. When the tensile fracture elongation is in the above range, the tensile properties are excellent and therefore suitable for the above applications.

The maximum tensile stress and tensile fracture elongation of the foamed particle molded product can be obtained as follows based on JIS K6767: 1999. First, using a vertical slicer, the foamed particle molded product is cut into 120 mm × 25 mm × 10 mm so that all the surfaces are cut out surfaces, and a cutout piece is prepared. Next, the cut-out piece is cut into a dumbbell-shaped No. 1 shape (measurement portion length 40 mm × width 10 mm × thickness 10 mm) using a jigsaw to obtain a test piece. A tensile test is performed on the test piece at a test speed of 500 mm / min, and the maximum tensile stress and tensile fracture elongation during tension are measured. For the tensile fracture elongation, the value of the length L [mm] of the test piece at the time of tensile fracture is obtained by the following equation (2).
Tensile fracture elongation [%] = L / 40 × 100 (2)

The compressive stress of the foamed particle molded product at 50% strain is preferably 700 kPa or less, more preferably 600 kPa or less, and further preferably 550 kPa or less. By setting the compressive stress within the above range, a foamed particle molded product suitable for applications such as seat cushion materials, sports pad materials, and sole materials can be obtained. The measurement of the compressive stress at the time of 50% strain of the foamed particle molded product is based on JISK6767: 1999, and the thickness of the foamed particle molded product is less than 25 mm (however, the thickness of the foamed particle molded product is less than 25 mm). In this case, a plurality of sheets are laminated to have a thickness of 25 mm.) A rectangular test piece having a melt-cured layer is cut out, and the compression rate is set to 10 mm / min in an environment of a temperature of 23 ° C. and a relative humidity of 50%. % Calculate the load at the time of strain and divide it by the pressure receiving area of the test piece.

The elastic modulus of the foamed particle molded product is preferably 50% or more, more preferably 55% or more, and further preferably 60% or more. On the other hand, the upper limit is about 90%. Since the rebound resilience is excellent when the rebound resilience is in the above range, it can be suitably used for applications such as seat cushion materials, sports pad materials, and sole materials. The elastic modulus of the foamed particle molded product is 50 mm in length × 50 mm in width × 40 mm in thickness (however, if the thickness of the foamed particle molded product is less than 40 mm, a plurality of sheets are laminated to increase the thickness to 40 mm. The test piece of (1) is cut out so as to have a skin surface on at least one surface of a flat surface (50 mm × 50 mm) and at least a part having a melt-cured layer, and the skin surface of the test piece is on the flat surface. A 254.6 g iron ball was dropped from a height of 600 mm to perform a ball drop test, and the bounce height H [mm] of the iron ball bounced off the test piece was measured and calculated according to the following equation (3). The repulsive elastic modulus is obtained. The skin surface that receives the iron ball may be the surface on which the melt-cured layer is formed.
Elastic modulus [%] = H / 600 × 100 (3)

Further, since the urethane-based thermoplastic elastomer molded product of the present invention has excellent physical properties such as a repulsive elastic modulus, it can be preferably used for sole applications. In particular, by forming the melt-cured layer on the side surface of the sole using the molded body, the sole has excellent physical properties and an excellent appearance.

Next, the urethane-based thermoplastic elastomer foamed particles used in the production of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention will be described.
The urethane-based thermoplastic elastomer foam particles used in the foamed particle molded product of the present invention supply the urethane-based thermoplastic elastomer to the extruder and knead it together with the foaming agent and the bubble modifier in the extruder to obtain a foamable melt. , A method of obtaining foamed particles by cutting a foamed strand obtained by extruding the melt from a strand die, or supplying a urethane-based thermoplastic elastomer to an extruder and kneading it together with a bubble modifier in the extruder to melt the melt. The melt is extruded from a strand die to produce urethane-based thermoplastic elastomer particles by a strand cut method or an underwater cut method, and the elastomer particles are foamed using a pressure-resistant container or the like. be able to.

The urethane-based thermoplastic elastomer used as the base material of the foamed particles in the foamed particle molded product of the present invention includes a soft segment made of a flexible polymer containing an ether group, an ester group, a carbonate group and the like, and a short chain glycol. The hard segment formed by urethane-bonding the chain extender and the diisocyanate has a block-copolymerized structure, and there are mainly ester-based and ether-based types. As the urethane-based thermoplastic elastomer, an ether-based one or an ester-based one can be appropriately selected depending on the physical characteristics required for the obtained foamed particle molded product. Ester-based products are preferable because they have higher mechanical strength and are also excellent in adhesiveness to other resin materials during in-mold molding. Further, the ester-based material is preferable from the viewpoint that it has a good affinity with carbon dioxide, which is preferably used as a foaming agent, and the foaming ratio of the foamed particles can be easily increased.

The melt flow rate of the urethane-based thermoplastic elastomer which is the base material of the foamed particles used in the foamed particle molded product of the present invention is preferably 40 g / 10 minutes or less, more preferably 0.1 g / 10 minutes or more. It is 30 g / 10 minutes or less, more preferably 0.3 g / 10 minutes or more and 20 g / 10 minutes or less. If the melt flow rate is too low, the meltability of the foamed particles during in-mold molding may be low. On the other hand, if the melt flow rate is too high, the recoverability of the foamed particle molded product obtained by in-mold molding of the foamed particles may decrease. This melt flow rate is a value measured under the conditions of a temperature of 190 ° C. and a load of 10 kg in accordance with JIS K7210-1: 2014.

The type A durometer hardness of the urethane-based thermoplastic elastomer is preferably 95 or less, more preferably 65 or more and 90 or less, further preferably 75 or more and 90 or less, and 85 or more and 90 or less. It is particularly preferable to have. If the hardness of the Type A durometer is too low, the foamed particles may shrink, or the foamed particle molded product obtained by molding the foamed particles in the mold may have poor recoverability, and the desired physical properties may not be obtained. There is. On the other hand, if the hardness of the Type A durometer is too high, the flexibility of the foamed particle molded product may deteriorate and the desired physical properties may not be obtained. The type A durometer hardness is a value measured based on ASTM D2240. Specifically, it is a value measured on the flat surface of the test piece under the conditions of a temperature of 23 ° C. and a relative humidity of 50% using a commercially available shore hardness tester such as a digital hardness tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.). is there.

The density of the urethane-based thermoplastic elastomer is preferably 1000 g / L or more and 1300 g / L or less, and more preferably 1050 g / L or more and 1250 g / L or less. The density is a value based on ASTM D792.
The melting point of the elastomer is preferably 130 ° C. or higher and 190 ° C. or lower, more preferably 140 ° C. or higher and 180 ° C. or lower, and further preferably 150 ° C. or higher and 170 ° C. or lower. The melting point is set at 10 ° C. after raising the temperature from 30 ° C. to 200 ° C. at a heating rate of 10 ° C./min based on the heat flux differential scanning calorimetry method described in JIS K7121 (1987). It can be obtained from the peak temperature of the heat absorption peak determined by the DSC curve obtained when the temperature is lowered to 30 ° C. at a cooling rate of / min and then raised again from 30 ° C. to 200 ° C. at a heating rate of 10 ° C./min. When a plurality of endothermic peaks appear in the second DSC curve, the apex temperature of the endothermic peak having the largest area is set as the melting point.

Additives other than the colorant can be added to the urethane-based thermoplastic elastomer, which is the base material of the foamed particles, as long as the objective effect of the present invention is not impaired. Examples of the additive include a bubble modifier, an antioxidant, an ultraviolet inhibitor, an antistatic agent, a flame retardant, a flame retardant aid, a metal deactivator, a conductive filler and the like. Specific examples of the bubble conditioner include inorganic powders such as zinc borate, talc, calcium carbonate, boric acid, aluminum hydroxide, silica, zeolite, and carbon, phosphoric acid-based nucleating agents, phenol-based nucleating agents, and amine-based agents. Examples thereof include organic powders such as nucleating agents and polyfluoroethylene resin powders. A preferred bubble conditioner is talc. The total amount of these additives is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the olefin-based thermoplastic elastomer. In addition, these additives are usually used in the minimum necessary amount. Further, these additives can be contained, for example, by adding and kneading them together with the urethane-based thermoplastic elastomer in the extruder.

A suitable production example of the urethane-based thermoplastic elastomer foamed particles used for producing the urethane-based thermoplastic elastomer foamed particle molded product of the present invention will be described. E. The foamed particles can be produced, for example, by a method including the steps (A), steps (B), steps (C) and steps (D) described below. The urethane-based thermoplastic elastomer foamed particles used for producing the urethane-based thermoplastic elastomer foamed particle molded product of the present invention are not limited to those obtained by the following production methods.

(Step (A))
In the step (A), urethane-based thermoplastic elastomer particles (hereinafter, also referred to as polymer particles) are dispersed in a dispersion medium in a pressure-resistant container.

The polymer particles are made into a size suitable for supplying a thermoplastic elastomer to an extruder and kneading it into a melt-kneaded product, extruding the melt-kneaded product into a strand shape from the extruder, and making the strand into a foamed particle. It can be produced by a known granulation method such as a cutting method. For example, in the above-mentioned method, polymer particles can be obtained by water-cooling a molded product obtained by extruding a melt-kneaded product into a strand shape and then cutting it to a predetermined length. When cutting to a predetermined length, for example, a strand cut method can be adopted. In addition, polymer particles can be obtained by a hot-cut method in which the melt-kneaded product is extruded immediately after extrusion, an underwater-cut method in which the melt-kneaded product is cut in water, or the like.

The average mass per polymer particle is usually preferably 0.01 mg or more and 15 mg or less, and more preferably 0.1 mg or more and 10 mg or less. The average mass of the polymer particles is a value obtained by dividing the mass (mg) of 100 randomly selected polymer particles by 100.

The dispersion medium used in the step (A) is not particularly limited as long as it is a dispersion medium that does not dissolve the polymer particles. Examples of the dispersion medium include water, ethylene glycol, glycerin, methanol, ethanol and the like. The preferred dispersion medium is water.

The polymer particles are dispersed in the above dispersion medium. For example, a stirrer is used to disperse the polymer particles in the dispersion medium.

In the step (A), the dispersant may be further added to the dispersion medium. Examples of the dispersant include organic dispersants such as polyvinyl alcohol, polyvinylpyrrolidone and methylcellulose, and sparingly soluble inorganic salts such as aluminum oxide, zinc oxide, kaolin, mica, magnesium phosphate and tricalcium phosphate. The preferred dispersant is kaolin. Further, the surfactant can be further added to the dispersion medium. Examples of the surfactant include sodium alkylbenzene sulfonate such as sodium oleate and sodium dodecylbenzene sulfonate, other anionic surfactants generally used in suspension polymerization, nonionic surfactants and the like. .. A preferred surfactant is sodium alkylbenzene sulfonate.

The pressure-resistant container used in the step (A) is not particularly limited as long as it is a pressure-resistant container that can be sealed. Since the polymer particles are heated in the step (B) described later and the pressure inside the pressure-resistant container rises, the pressure-resistant container needs to be able to withstand the rise in pressure in the step (B). The pressure-resistant container is, for example, an autoclave.

(Step (B))
In the step (B), the thermoplastic elastomer of the polymer particles dispersed in the dispersion medium in the step (A) is softened and heated to a temperature at which it does not condense in the closed container. The heating temperature is, for example, in the range of 100 ° C. or higher and 170 ° C. or lower.

(Step (C))
In the step (C), after the step (B) or at the same time as the step (B), a foaming agent for foaming the polymer particles is added to the dispersion medium in the pressure-resistant container, and the foaming agent is added to the softened polymer particles. Impregnate. The temperature at which the foaming agent is impregnated is not particularly limited as long as the polymer particles are in a softened state without condensing, but is, for example, in the range of 100 ° C. or higher and 170 ° C. or lower.

The foaming agent used in the step (C) is not particularly limited as long as it foams the crosslinked particles. Examples of the foaming agent include inorganic physical foaming agents such as air, nitrogen, carbon dioxide, argon, helium, oxygen and neon, aliphatic hydrocarbons such as propane, normal butane, isopentane, normal pentane, isopentane and normal hexane, and cyclohexane. , Cyclopentane and other alicyclic hydrocarbons, 1,3,3,3-tetrafluoropropene, 1-chloro-3,3,3-trifluoropropene and other halogenated hydrocarbons, dimethyl ether, diethyl ether, methyl ethyl Examples thereof include organic physical foaming agents such as dialkyl ethers such as ethers. Among these, an inorganic physical foaming agent is preferable from the viewpoint of safety and the like, nitrogen, air and carbon dioxide are more preferable, and carbon dioxide is particularly preferable. These can be used alone or in combination of two or more. The blending amount of the foaming agent is determined in consideration of the apparent density of the target foamed particles, the type of thermoplastic elastomer, the type of foaming agent, etc., but is usually organically physically foamed with respect to 100 parts by mass of the elastomer. The agent is preferably 5 parts by mass or more and 50 parts by mass or less, and the inorganic physical foaming agent is preferably 0.5 parts by mass or more and 30 parts by mass or less.

(Step (D))
In the step (D), the foaming agent is impregnated in the step (C), and the softened foamable polymer particles are released into an atmosphere having a pressure lower than the pressure in the pressure-resistant container to produce foamed particles. Specifically, while maintaining the pressure inside the pressure-resistant container at a pressure equal to or higher than the vapor pressure of the foaming agent, one end below the water surface inside the pressure-resistant container is opened, and the foamable polymer particles containing the foaming agent are mixed with the dispersion medium. Foamed particles are produced by releasing the foamable polymer particles from the pressure-resistant container in an atmosphere lower than the pressure in the pressure-resistant container, usually under atmospheric pressure, to foam the foamable polymer particles. The impregnation step (step (C)) and foaming step (step (D)) are preferably performed as a series of steps in a single pressure-resistant container.

As a method for producing urethane-based thermoplastic elastomer foamed particles used for producing the urethane-based thermoplastic elastomer foamed particle molded product of the present invention, a method for producing the urethane-based thermoplastic elastomer foamed particles has been described as described above. It is not limited to the above manufacturing method. For example, a thermoplastic elastomer, a foaming agent, or the like is supplied to an extruder to be melted, the thermoplastic elastomer is contained with a foaming agent, and then a softened foamable thermoplastic elastomer is stranded from a die attached to the tip of the extruder. A method for producing foamed particles by extruding and foaming into a shape, or after steps (A) to (C), the inside of the pressure-resistant container is decompressed and deheated, and then the foaming agent-containing polymer particles are put into the container. A method of producing foamed particles by taking out from the inside, dehydrating and drying, and then heating the foaming agent-containing polymer particles with a heating medium such as steam to foam them may be used.

The average particle size of the foamed particles used in the production of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 0.5 mm or more and 10 mm or less, more preferably 1 mm or more and 8 mm or less, and further preferably 2 mm. It is 5 mm or more and 5 mm or less. When the average particle size of the foamed particles is in the above range, the foamed particles can be easily produced, and when the foamed particles are molded in the mold, the foamed particles can be easily filled in the mold. The average particle size of the foamed particles can be controlled by adjusting, for example, the amount of the foaming agent, the foaming conditions, the particle size of the polymer particles, and the like.

The average cell diameter of the foamed particles used in the production of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 50 μm or more and 300 μm or less. Within the above range, a good molded product having excellent physical properties such as a rebound resilience can be obtained. From the above viewpoint, the average bubble diameter of the foamed particles is preferably 60 μm or more and 280 μm or less, and more preferably 70 μm or more and 250 μm or less.
The average bubble diameter of the foamed particles is a value measured as follows according to ASTM D3576-77. First, 50 or more foamed particles are randomly selected from the foamed particle group. The foamed particles are cut so as to pass through the center thereof and divided into two. In one cross section of each of the cut foam particles, four line segments are drawn at an equal angle from the outermost surface of the foamed particles to the opposite outermost surface through the central portion. Measure the number of bubbles that intersect each line segment, divide the total length of the four line segments by the total number of cells that intersect the line segment to obtain the average chord length of the bubbles, and further divide by 0.616. By doing so, the average cell diameter of the foamed particles is obtained.

The average surface film thickness of the foamed particles used in the production of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably about 10 to 50 μm, more preferably 10 to 45 μm. By setting the average surface film thickness of the foamed particles in the above range, it is possible to improve the fusion property between the foamed particles at the time of in-mold molding and to suppress the foaming of bubbles near the surface of the foamed particles. , A good molded product can be stably obtained.

The average surface film thickness of the foamed particles is measured as follows. At least 50 foamed particles are randomly selected from the foamed particle group. The foamed particles are cut so as to pass through the central portion thereof and divided into two, and an enlarged photograph of one cross section is taken. In each cross-sectional photograph, four line segments are drawn at equal angles from the outermost surface of the foamed particles to the outermost surface on the opposite side through the central portion. By measuring the length (surface layer film thickness) from the outermost surface of the foamed particles to the bubbles located on the outermost side of the foamed particles on the line segment and arithmetically averaging those values, the average surface layer film of each foamed particle. Find the thickness. Then, the average surface film thickness of the foamed particles is obtained by arithmetically averaging these values.

The bulk density of the foamed particles used in the production of the urethane-based thermoplastic elastomer foamed particle molded product of the present invention is preferably 30 to 200 g / L, more preferably 30 to 180 g / L, and further preferably 35 to 35. It is 160 g / L, and particularly preferably 50 to 150 g / L. By setting the bulk density of the foamed particles in the above range, the lightness, flexibility and resilience of the foamed particle molded product produced by in-mold molding of the foamed particles can be further improved. Further, a good melt-cured layer can be formed by indirect heating in the in-mold molding step described later.

The average particle size and bulk density of the foamed particles can be measured as follows. First, the foamed particle group is left to stand for 48 hours under the conditions of a relative humidity of 50% and a temperature of 23 ° C. and 1 atm. Next, a graduated cylinder containing water having a temperature of 23 ° C. was prepared, and an arbitrary amount of foamed particle group (mass W1 of the foamed particle group) left for 48 hours was placed in water in the graduated cylinder using a tool such as a wire mesh. And sink. Then, in consideration of the volume of a tool such as a wire mesh, the volume V1 [L] of the foamed particle group read from the rising water level is measured. The average volume per foamed particle is calculated by dividing this volume V1 by the number of foamed particles (N) placed in the graduated cylinder (V1 / N). Then, the diameter of the virtual true sphere having the same volume as the obtained average volume is defined as the average particle diameter [mm] of the foamed particles. As for the bulk density of the foamed particles, the foamed particles are left to stand for 48 hours under the conditions of a relative humidity of 50% and a temperature of 23 ° C. and 1 atm. Next, an empty graduated cylinder is prepared, an arbitrary amount of foamed particle group (mass W2 of the foamed particle group) left for 48 hours is placed in the graduated cylinder, and the floor surface is tapped several times with the bottom surface of the graduated cylinder. Stabilizes the filling height of the foamed particles in the cylinder. Then, the volume V2 [L] of the foamed particle group indicated by the scale of the measuring cylinder is measured. The bulk density of the foamed particles can be obtained by dividing the mass W2 (g) of the foamed particles placed in the graduated cylinder by the volume V2 (W2 / V2).

Next, an example of the method for producing the urethane-based thermoplastic elastomer foamed particle molded product of the present invention will be described.
By adopting the manufacturing method described later, a melt-cured layer having a specific thickness can be formed on the molded body, whereby a three-dimensional uneven shape and fine voids due to the shape of the foamed particles are formed on the surface of the molded body. It disappears and the appearance of the molded product can be improved. Further, since the melt-cured layer can be formed without lowering the internal fusion state of the molded product, it is possible to obtain a molded product having excellent mechanical properties such as tensile stress. In addition, since the mechanical properties such as compressed physical properties do not change significantly as compared with the molded body in which the melt-cured layer is not formed, a molded product having desired physical properties can be obtained.

The urethane-based thermoplastic elastomer foamed particle molded product of the present invention can be produced, for example, by the following method. First, the foamed particles are filled in a mold cavity for a known thermoplastic resin foamed particle molded product that can be heated and cooled, opened and closed, and sealed. At this time, at least one mold is provided with a mechanism capable of heating the surface of the mold on the cavity side by circulating steam or the like in the mold (hereinafter, also referred to as an indirect heating mold). .. From the viewpoint of improving the appearance of the surface of the molded product, it is preferable that the indirect heating mold does not have steam supply holes. Further, when a decorative surface having a concavo-convex pattern is provided on the surface of the molded body, an indirect heating mold having a decorative surface for transfer that can transfer the decorative surface of the concavo-convex pattern to the surface of the molded body can be used.

Next, saturated steam is supplied, the foamed particles are heated and expanded in the mold cavity, and the foamed particles are fused to each other to form a foamed particle molded product, and the molded product is formed by a heated indirect heating mold. Melt the foamed particles on the surface. After that, the mold is cooled, the molded product is cooled, and the foamed particles on the surface of the molten molded product are cured and then taken out from the mold, whereby a molded product having a melt-cured layer on the surface can be obtained. ..

As described above, the molded product of the present invention is a urethane-based thermoplastic elastomer filled in a highly compressed state in a mold having a decorative decorative surface for transfer having no steam supply holes in at least a part of the mold. It is preferable to obtain the foamed particles by in-mold molding. As a method of filling the foamed particles in a molding mold such as a mold cavity in a highly compressed state to improve the secondary foamability of the foamed particles, for example, the foamed particles are pressurized in a state of being compressed with a pressurized gas. The mold is filled in the mold and then the pressure in the mold is released (compression filling method), or the mold is opened in advance to expand the molding space before filling the foam particles in the mold, and the mold is closed after filling. Therefore, a method of mechanically compressing the foamed particles (cracking filling method) or the like can be adopted.

As described above, the urethane-based thermoplastic elastomer foamed particles have a strong repulsive force of the foamed particles, but it is difficult to control the secondary foamability during in-mold molding, and the physical properties are likely to deteriorate due to heating. Due to this, in-mold molding is difficult. Therefore, when producing the urethane-based thermoplastic elastomer foamed particle molded product of the present invention, it is preferable to adopt a compression filling method or a cracking filling method as a method for filling the foamed particles into the mold cavity, and in particular, compression filling. It is preferable to adopt the method. When the compression filling method is adopted, the foamed particles can be uniformly compressed in the mold in the three-dimensional direction, so that the restoring force of the filled foam particles in the direction perpendicular to the moving direction of the mold is obtained. And secondary foaming power can be increased. Therefore, it is difficult to press the foamed particles by the cracking filling method, and the foamed particles can be sufficiently pressed against the inner surface of the mold which is in a positional relationship parallel to the moving direction of the mold. Therefore, the foamed particles are molded by the compression filling method. A good melt-cured layer can also be formed on the side surface of the body (the surface formed by the inner surface of the mold which is in a positional relationship parallel to the moving direction of the mold).
When these methods are adopted, the foamed particles are filled in the mold in a highly compressed state in which the filling amount of the foamed particles in the cavity: M (g) satisfies the following equations (4) and (5). The desired foamed particle molded product can be obtained by in-mold molding.
0.9 ・ V ・ Bd ≦ M (4)
1.6 ≤ IP + M / (V · Bd) ≤ 3.0 (5)
(However, V is the volume (L) of the cavity after molding, Bd is the bulk density (g / L) of the foamed particles after curing for 48 hours under the conditions of 23 ° C., relative humidity 50%, and normal pressure, IP. Is the internal pressure of the foamed particles filled into the cavity [10 ^-1 MPa (G)])

As the foamed particles, the foamed particle internal pressure IP is preferably ^{0 to 1.2 [10 -1} MPa (G)] (including 0), preferably 0 to 0.5 [10 ^-1 MPa (G)] (0). ), More preferably ^{0 to 0.2 [10 -1} MPa (G)] (including 0).
In the present invention, the foamed particles having an internal pressure IP of ^{0 to 1.2 [10 -1} MPa (G)] (including 0) are the gas pressure inside the foamed particles before the foamed particles are molded in the mold. The operation of increasing the expansion force of the foamed particles when the foamed particles are heated, that is, the so-called internal pressure applying operation to the foamed particles is not performed on the foamed particles, and the operation is performed to foam the foamed particles. It means that the upper limit when the internal pressure is applied to the foamed particles is preferably 1.2 [10 ^-1 MPa (G)], including those in which the internal pressure of the particles is increased. The operation of applying internal pressure to the foamed particles can be expected to have an effect of improving the expansion force when the foamed particles are heated, and generally improves the in-mold molding performance. On the other hand, the urethane-based thermoplastic elastomer foamed particles used in the present invention are excellent. Since it is an elastic body, if the expansion force becomes too high, it may prevent the heating medium such as steam from spreading to every corner of the foamed particle group in the mold during in-mold molding. The dimensional stability and appearance of the foamed particle molded product obtained by internal molding may deteriorate. From the above viewpoint, it is preferable to use foamed particles in which the internal pressure applying operation is not performed or foamed particles in which the internal pressure is hardly applied. Further, the compression filling molding method or the like is performed using the foamed particles having ^{an IP of 0 to 0.2 [10 -1} MPa (G)] (including 0), which is the category of the internal pressure of the foamed particles in this case. Therefore, the molding cycle at the time of in-mold molding can be shortened.
In the present specification, "normal pressure" is synonymous with 0 [MPa (G)] in gauge pressure, but means about 1 atm in absolute pressure.

The above equation (4) shows the filling rate [X = M / (V · Bd)] [-] of the foamed particles filled in the cavity of the mold, and the filling rate is 0.9 [-]. The above means that the minimum required filling rate is 0.9 [−] even when the internal pressure IP is applied to the foamed particles. Since urethane-based thermoplastic elastomer foamed particles have high frictional resistance between the foamed particles and poor slipperiness, it is difficult to fill the cavity of the mold as compared with foamed particles made of general-purpose resin such as polystyrene resin. However, by adopting a filling method such as a compression filling method, the above equation (4) can be satisfied, and a target molded product can be stably obtained.
Further, in the above equation (4), for example, when the filling rate is 2.0 (-), the filling weight of the foamed particles when the ideal amount of the foamed particles that fill the cavity without being compressed is filled is approximately. This means that twice the weight of the foamed particles is compressed and filled in the cavity, and the foamed particles in the cavity are compressed and filled with approximately twice the restoring force of the amount of foamed particles that fills the cavity without being compressed. Will be granted by. Actually, the relationship between the filling rate and the ideal amount of foamed particles that can be filled in the cavity is that the volume expansion of the foamed particles when the internal pressure is applied to the foamed particles, the deterioration of the filling property due to the frictional resistance between the foamed particles, and the like. Although it is necessary to take this into consideration, by adopting a filling method such as a compression filling method, it is possible to stably fill the cavity with an ideal amount of foamed particles.

Further, the above equation (5) is ^{the sum of the foamed particle internal pressure IP [10 -1} MPa] and the filling rate X [-], that is, the foaming force by improving the internal pressure of the foamed particles and the restoring force by the compression filling method or the like. It shows the expansion force of the foamed particles generated by the resultant force, and the fact that [IP + M / (V · Bd)] is 1.6 to 3.0 means that the cavity with the internal volume V [L] is filled. It means that the foamed particles are adjusted to a state in which a volume increasing capacity of about 1.6 to 3.0 times is added by heating during appropriate in-mold molding by applying internal pressure and filling in a highly compressed state. To do.

In the above equations (4) and (5), if the filling rate is too high, the fusion of the foamed particles may deteriorate inside the foamed particle molded product, or a homogeneous melt-cured layer may not be formed. There is. On the other hand, if the filling rate is too low, the fusion of the foamed particles to each other may be deteriorated, or the obtained molded product may be deformed. In addition, dents (voids) between the foamed particles may easily occur on the surface of the molded product, and a good melt-cured layer may not be formed.
Further, in the present invention, the urethane-based thermoplastic elastomer constituting the foamed particles is, due to its flexibility, foamed particles such as polypropylene resin foamed particles and polystyrene resin foamed particles by applying internal pressure or the like. It is difficult to increase the internal pressure of. In addition, since it is difficult to control the secondary foamability of the urethane-based thermoplastic elastomer foamed particles as described above, in-mold molding of the foamed particles becomes more difficult. ), By performing the in-mold filling under the conditions satisfying the equations (5), the desired foamed particle molded product can be stably obtained by the in-mold molding.

The foamed particles used for in-mold molding have a closed cell ratio of preferably 70% or more, more preferably 80% or more, and further preferably 90% or more. Further, the bulk density (Bd) of the foamed particles used for in-mold molding is preferably 200 g / L or less.
To measure the closed cell ratio of the foamed particles, the mass W (g) of the measurement sample ^{having a bulk volume of about 20 cm 3 is measured, and the apparent volume Va (cm 3} ) of the measurement sample is measured by the submersion method. After the measurement sample is sufficiently dried, the true volume (volume of the resin constituting the foamed particles) is determined by using an air comparison hydrometer 930 (manufactured by Toshiba Beckman Co., Ltd.) according to the procedure C of ASTM D2856. And the total volume of closed cells in the foamed particles) Vx (cm ³ ) is measured. Then, the closed cell ratio (%) is calculated by the following equation (6), where the density of the thermoplastic elastomer is ρ. For the sample for measuring the closed cell ratio of the foamed particles, the foamed particles were placed in a closed container, pressurized at 30 ° C. with compressed air of 0.3 MPa (G) for 12 hours, and then released to 40 ° C. After leaving it at atmospheric pressure for 24 hours, it is left for 10 days in a thermostatic chamber at a relative humidity of 50% and 23 ° C. and cured.
Closed cell ratio (%) = {(Vx-W / ρ) / (Va-W / ρ)} x 100 (6)

By setting the closed cell ratio of the foamed particles within the above range, the recoverability of the foamed particles can be restored even when in-mold molding is performed by the high compression compression molding method under the conditions of the above formulas (4) and (5). It is possible to obtain a molded product in which a good melt-cured layer is formed, which is excellent in the fusion property between the foamed particles. Further, by setting the bulk density of the foamed particles within the above range, it is possible to stably produce a molded product even by using a compression molding method for high compression.

Since the thermoplastic elastomer foamed particles used in the present invention have high flexibility and resilience, the foamed particles can be filled in the mold in a highly compressed state. Here, by filling the mold with foamed particles having a closed cell ratio, bulk density, and foamed particle internal pressure within the above range with a filling rate within the above range, the foamed particles in the mold can be heated by a heat medium. It is possible to sufficiently develop the secondary foaming power of the foamed particles while maintaining the gaps between the foamed particles and securing the flow paths of the heating medium in every corner. In addition to this, by performing indirect heating under the conditions described later, it is possible to obtain a molded product in which the foamed particles have excellent cohesiveness to each other and a good melt-cured layer is formed.

In the compression filling method, the pressure in the mold cavity in the pressurized state is preferably about 1.2 MPa (G) or more and 0.50 MPa (G) or less. Further, the differential pressure was used to adjust the compression gas pressure in the pressure hopper to be 0.01 MPa (G) or more and 0.10 MPa (G) or less higher than the pressure in the mold cavity in the pressurized state. It is preferable from the viewpoint of filling the foamed particles into the mold.

As the gas used to pressurize the inside of the mold cavity, an inorganic gas, an organic gas, or a mixed gas thereof can be used, but from the viewpoint of safety and economy, an inorganic gas such as air, nitrogen, and carbon dioxide is used. Is preferable.

In the compression filling method, the pressure inside the mold cavity under pressure is released to increase the pressure inside the mold cavity to atmospheric pressure or substantially large while the foam particles are compression-filled in the mold cavity. The compressed foam particles are restored by setting the atmospheric pressure. After this restoration, there are still voids between the foamed particles that allow the heating medium to sufficiently pass between the foamed particles when the foamed particles are heated by the heating medium in the subsequent step.

As described above, the foamed particles filled in the mold expand by being heated by a heating medium such as steam introduced into the mold, and are fused to each other on the surface of the adjacent foamed particles. As a result, the foamed particle molded product is formed, and the foamed particles on the surface of the molded product are melted by the heated indirect heating mold. Next, the foamed particle molded product is cooled to cure the foamed particles on the surface of the molten molded product, and then the foamed particles are taken out from the mold cavity and subjected to a curing step to obtain a desired foamed particle molded product. Prior to the process of introducing a heating medium into the mold to heat and mold the foamed particles, an operation of replacing the gas existing in the voids between the foamed particles filled in the mold with steam, so-called It is preferable to carry out the exhaust process.

In the in-mold molding step, when the heating medium introduced into the mold is steam, the saturated vapor pressure thereof is preferably 0.05 MPa (G) or more and 0.8 MPa (G) or less (supplied into the mold). It is the maximum value of the saturated vapor pressure of steam), and more preferably 0.15 MPa (G) or more and 0.5 MPa (G) or less.
Further, in the indirect heating mold, it is preferable to set the temperature of the surface in contact with the foamed particles so that the foamed particles in contact with the mold can be melted. Specifically, the temperature of the surface in contact with the foamed particles is preferably about 120 ° C. or higher and 180 ° C. or lower, and more preferably 130 ° C. or higher and 160 ° C. or lower. If the heating temperature of the indirect heating mold is too low, the surface of the foamed particles may not be sufficiently melted and a good melt-cured layer may not be formed. Further, even when the surface of the foamed particles is melted, the time may be long and the molding cycle may be long. On the other hand, if the heating temperature of the indirect heating mold is too high, it is difficult to control the molten state of the surface of the foamed particles, and there is a possibility that a good melt-cured layer cannot be formed.

When the medium for heating the indirect heating mold is steam, the saturated vapor pressure is preferably about 0.1 MPa (G) or more and 0.9 MPa (G) or less (saturation of the steam supplied into the indirect heating mold). The maximum value of the vapor pressure), more preferably 0.2 MPa (G) or more and 0.8 MPa (G) or less.
Further, the heating time by the indirect heating mold is preferably about 10 seconds or more and 45 seconds or less, and more preferably 15 seconds or more and 40 seconds or less. If the heating time by the indirect heating mold is too short, the melt-cured layer may be formed inhomogeneously, or it may be difficult to form the melt-cured layer itself. Further, if the heating time is too long, the molding cycle may be lengthened, the amount of steam consumed may increase, and cavities may be formed inside the molded body, so that a good molded body may not be obtained. ..
Since the thermoplastic elastomer foamed particles are inferior in secondary foamability as described above, it is difficult to mold the foamed particles in the mold. In spite of such a situation, in the present invention, in particular, by satisfying the above equations (4) and (5) and setting the above indirect heating conditions, it is stable and excellent in internal fusion. It is possible to obtain a molded product having a melt-cured layer.

The heating procedure using a heating medium in the in-mold molding method is not particularly limited, but the following procedure is preferable for obtaining a foamed particle molded product having excellent fusion properties, appearance, physical properties, etc. between the foamed particles. ..

The mold is formed from a pair of molds of a male mold having a steam chamber and a female mold, and in the step of supplying a heating medium into the mold to heat the foamed particles, the male mold or the female mold is formed. One heating process that supplies steam to the chamber, passes through a cavity formed by combining male and female molds, and leads to the chamber of the other mold, supplies steam to the chamber of the other mold, and the cavity. The foamed particles are heat-fused by sequentially performing the reverse one-sided heating step of leading the steam to the chamber of the mold to which steam is supplied in the one-sided heating step and the main heating step of simultaneously supplying steam to the male and female mold chambers. The heating procedure for heating is preferably exemplified. In the above heating procedure, the open / closed state of the drain discharge valve of the male or female chamber may be at least closed in the chamber on the steam supply side during heating on one side and heating on the other side.
Further, from the viewpoint of preventing the formation of cavities inside the molded product, it is preferable that the heating by the indirect heating mold is set to be completed at the same time as the step of heat-sealing the foamed particles.

Here, the method of introducing a heating medium into the mold in the in-mold molding step has been described, but as another in-mold molding method, for example, the foamed particle molded product of the present invention is produced by electromagnetic waves such as microwaves. You can also do it.

Specifically, in the in-mold molding process, the foamed particles are filled in the mold together with a heating medium such as water in a highly compressed state, and then the mold is irradiated with electromagnetic waves such as microwaves to obtain the foamed particles. The foamed particles are heated by a heating medium or the like existing on the surface to cause secondary foaming, the foamed particles are heat-fused together, and the foamed particles on the surface of the molded product are melted by a heated mold. After that, the mold is cooled, the molded product is cooled, and the foamed particles on the surface of the molten molded product are cured and then taken out from the mold, whereby a molded product having a melt-cured layer on the surface can be obtained. ..

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

(Example 1)
<Preparation of urethane-based thermoplastic elastomer particles>
Density 1120 g / L, melting point 164 ° C, melt flow rate 7 g / 10 minutes (190 ° C, load 10 kg), type A durometer hardness 86 ether-based thermoplastic polyurethane (urethane-based thermoplastic elastomer) (manufactured by Cobestro, trade name) "Desmopan", model number 9385AU) 100 parts by mass, 0.10 parts by mass of talc as a bubble conditioner, pigment masterbatch as a colorant (blue coloring masterbatch): Pandex B-UN91-9127-20 (phthalocyanine) 1 part by mass of blue) was added, and melt-kneaded with a twin-screw extruder having an inner diameter of 20 mm. The kneaded product was extruded into a strand shape from the small holes of the mouthpiece attached to the tip of the extruder, cooled, and then cut to obtain 5.1 mg of resin particles.

<Preparation of urethane-based thermoplastic elastomer (TPU) foamed particles>
1 kg of the urethane-based thermoplastic elastomer particles obtained above and 3 liters of water as a dispersion medium were placed in a 5 liter pressure-resistant airtight container equipped with a stirrer, and used as a dispersant with respect to 100 parts by mass of the resin particles. 0.3 parts by mass of kaolin and 0.004 parts by mass of sodium alkylbenzene sulfonate were added as a surfactant.
While stirring the dispersion medium in the pressure-resistant airtight container, the temperature was raised to 127.5 ° C., carbon dioxide as a foaming agent was press-fitted until the pressure in the airtight container reached 4.0 MPa (G), and the mixture was held for 15 minutes. .. After that, back pressure is applied with nitrogen to adjust the pressure inside the container to 4.5 MPa (G), and the foamable resin particles impregnated with the foaming agent together with the dispersion medium are released under atmospheric pressure. Foamed particles were obtained.

The closed cell ratio, average surface film thickness, and bulk density of the obtained foamed particles were measured according to the methods described above and are shown in Table 1.

<Preparation of foamed particle molded product>
The foamed particles obtained as described above are put into a hopper, and a flat plate-shaped mold cavity having a length of 310 mm, a width of 310 mm, and a thickness of 20 mm formed from a pair of molds of a male mold and a female mold is formed from the hopper. The inside was compressed and filled so as to have the filling rate shown in Table 1. As the male mold, an indirect heating mold is used in which the decorative surface with a leather grain pattern can be transferred to the surface of the molded body and the decorative surface for transfer is provided on the surface perpendicular to the moving direction of the mold. did. Then, the inside of the mold cavity was released to release the compressed foam particles. Subsequently, steam is introduced into the cavity, and the foamed particles are directly heated to fuse the foamed particles to each other, and the surface of the foamed particle molded product is melted through a mold heated by steam. Indirect heating was performed so that the timing of starting cooling was simultaneous. As the conditions for steam heating, the steps of exhaust, one-sided heating, reverse one-sided heating, and main heating are shown in the direct heating, and the steps of exhaust and pressure-adjusting heating in indirect heating are shown in the column of molding conditions in Table 1. It was carried out sequentially by time and pressure. Next, the foamed particle molded product was cooled by cooling the mold with water, and then the foamed particle molded product was taken out from the mold. The released foamed particle molded product was heated and dried in an oven adjusted to 60 ° C. for 12 hours to obtain a foamed particle molded product. In this way, the melt-cured layer (length 310 mm × width 310 mm) is provided on one of the surfaces perpendicular to the thickness direction of the molded product, and the skin grain pattern on the decorative surface for transfer is transferred to the surface of the melt-cured layer. A foamed particle molded product was obtained.

(Example 2)
A foamed particle molded product was obtained in the same manner as in Example 1 except that the foamed particles used, filling conditions, and molding conditions were changed as shown in Table 1.

(Comparative Examples 1 and 2)
Foaming particles are molded in the same manner as in Example 1 except that the foamed particles to be used, filling conditions, and molding conditions are changed as shown in Table 1 and an indirect heating mold is not used to form a melt-cured layer. I got a body.

(Example 3)
In Example 3, the foamed particles obtained as described above are put into a hopper, and the hopper has a length of 310 mm, a width of 310 mm, and a thickness of 20 mm formed from a pair of molds of a male mold and a female mold. A foamed particle molded product was obtained in the same manner as in Example 1 except that the mold cavity was filled in a flat plate shape, the mold was further clamped, and cracking was performed so as to obtain the filling ratio shown in Table 1. .. The "cracking amount" is the moving distance of the male mold in the female mold when the foamed particles are filled in the mold cavity and then further molded.

(Example 4)
A foamed particle molded product was obtained in the same manner as in Example 2 except that the foamed particles used, filling conditions, and molding conditions were changed as shown in Table 1.

(Comparative Examples 3 and 4)
Foaming particles are molded in the same manner as in Example 3 except that the foamed particles to be used, filling conditions, and molding conditions are changed as shown in Table 1 and an indirect heating mold is not used to form a melt-cured layer. I got a body.

[Evaluation results]
The evaluation results of the foamed particle molded products obtained in Examples 1 to 4 and Comparative Examples 1 to 4 are also shown in Table 1.

The evaluation of the foamed particle molded product in Table 1 was performed as follows.
1) Apparent density The apparent density (g / L) of the foamed particle molded product was determined by the method described above.

2) Appearance After the foamed particle molded product obtained by in-mold molding was heat-dried and cured in an oven adjusted to 60 ° C. for 12 hours, the surface of the melt-cured layer was visually observed, and the transferability of the grain pattern and the beads were observed. The presence or absence of the pattern was evaluated.
The evaluation criteria were as follows.
A: The grain pattern is beautifully transferred and there is no bead pattern.
B: The grain pattern is transferred, but the bead pattern can be confirmed faintly. C: The grain pattern is transferred, but the bead pattern can be clearly confirmed.

3) Cohesiveness (maximum tensile stress)
The maximum tensile stress of the foamed particle compact was measured based on JIS K6767: 1999. First, using a vertical slicer, the foamed particle molded product was cut into 120 mm × 25 mm × 10 mm so that all the surfaces became cut-out surfaces, and cut-out pieces were prepared. The cut-out piece was cut into a dumbbell-shaped No. 1 shape (measurement portion length 40 mm × width 10 mm × thickness 10 mm) using a jigsaw to obtain a test piece. The test piece was subjected to a tensile test at a test speed of 500 mm / min, the maximum tensile stress during tension was determined, and the test piece was evaluated according to the following criteria.
A: Maximum tensile stress is 700 kPa or more B: Maximum tensile stress is less than 700 kPa

4) Coefficient of variation of average thickness of melt-cured layer and thickness of melt-cured layer The coefficient of variation of average thickness of melt-cured layer and thickness of melt-cured layer was measured by the above-mentioned method. Specifically, first, the foamed particle molded body is cut substantially perpendicular to the surface on which the melt-cured layer is formed so as to pass through the melt-cured layer, and an enlarged photograph of the cut surface (magnification magnification 100 times). Was taken. Next, in the cut surface photograph, the length in the direction perpendicular to the surface on which the melt-cured layer is formed (thickness of the melt-cured layer) from the outermost surface of the foamed particle molded body to the bubbles located on the outermost side of the molded body. ) Was measured at 10 points at equal intervals. The thickness of the melt-cured layer was measured on enlarged photographs of five different cut surfaces, and the average thickness of the melt-cured layer was obtained by arithmetically averaging the thickness values of a total of 50 points. It was.
The coefficient of variation of the thickness of the melt-cured layer was obtained by obtaining the measured standard deviation of the thickness of the melt-cured layer, dividing the standard deviation by the average thickness of the melt-cured layer, and further multiplying by 100.

5) Compression characteristics The 50% compressive stress of the foamed particle molded product based on JIS K6767: 1999 described above was measured. In addition, the ratio of compressive stress to apparent density (compressive stress / apparent density) was determined.
The ratio of the compressive stress to the apparent density of Examples and Comparative Examples (for example, Example 1 and Comparative Example 1) corresponding to the numbers was compared and evaluated according to the following criteria.
◯: The value of the example with respect to the value of the comparative example is within ± 10% ×: The value of the example with respect to the value of the comparative example exceeds ± 10%

The above-mentioned various evaluation results for the foamed particle molded body show that the foamed particle molded body was cured under normal pressure at 40 ° C. for 24 hours and then placed in a thermostatic chamber at a relative humidity of 50% and 23 ° C. for 2 days (48 hours). ) It is a value measured for a sample that has been left to cure.

As can be seen from the comparison between Examples 1 to 4 and Comparative Examples 1 to 4, the molded product on which the melt-cured layer was formed was excellent in fusion property and also in appearance. Further, since the melt-cured layer is formed to have a specific thickness, the compressed physical properties do not change significantly as compared with the molded product in which the melt-cured layer is not formed, and a molded product having desired physical properties can be obtained.

Claims (10)

In-mold molded product of urethane-based thermoplastic elastomer foamed particles, which is formed by filling a mold with urethane-based thermoplastic elastomer foamed particles and introducing a heating medium into the mold to fuse the foamed particles to each other. And
The closed cell ratio of the molded product is 60% or more, and the molded product has a closed cell ratio of 60% or more.
The maximum tensile stress of the molded product is 0.70 MPa or more, and the molded product has a maximum tensile stress of 0.70 MPa or more.
Foamed particles are melted and a cured melt-cured layer is formed on at least a part of the surface of the molded product, and the average thickness of the melt-cured layer is 0.05 mm or more and 0.4 mm or less. Urethane-based thermoplastic elastomer foamed particle molded product. The urethane-based thermoplastic elastomer foamed particle molded product according to claim 1, wherein the apparent density of the molded product is 100 g / L or more and 350 g / L or less. The urethane-based heat according to claim 1 or 2, wherein the foamed particles constituting the molded product are foamed particles based on a urethane-based thermoplastic elastomer having a type A durometer hardness of 95 or less. Plastic elastomer foamed particle molded product. The urethane-based thermoplastic elastomer foamed particle molded product according to any one of claims 1 to 3, wherein the coefficient of variation of the thickness of the melt-cured layer is 30% or less. The urethane-based thermoplastic elastomer foamed particle molded product according to any one of claims 1 to 4, wherein the melt-cured layer is formed on at least one surface of the molded product. The urethane-based thermoplastic elastomer foamed particle molded product according to any one of claims 1 to 5, wherein the molded product contains a colorant. The urethane-based thermoplastic elastomer foamed particle molded product according to any one of claims 1 to 6, wherein a decorative surface having an uneven pattern is formed on the surface of the melt-cured layer. The urethane-based thermoplastic elastomer foamed particle molded product according to any one of claims 1 to 6, wherein a smooth surface is formed on the surface of the melt-cured layer. A sole using the urethane-based thermoplastic elastomer foamed particle molded product according to any one of claims 1 to 8. The sole according to claim 9, wherein the melt-cured layer is formed on at least a side surface of the sole.