JP6872857B2 - Manufacturing method of foamed resin molded products and foamed resin molded products - Google Patents

Description

The present invention relates to a method for producing a foamed resin molded product and a foamed resin molded product, specifically, a method for producing a fibrous foamed resin molded product having a fibrous inside and a fibrous foamed resin molded product.

Various resin molded products are used in fields such as automobile interior parts and home appliance housings and parts. Conventionally, such resin molded products have been mainly solid inside, but recently, from the viewpoint of weight reduction of molded products and saving of raw materials consumed, foamed resin molded products having a cell structure inside have been adopted. It has been replaced.

As a method for producing a foamed resin molded product, a method based on an injection molding method is known. Specifically, a thermoplastic resin composition containing a foaming agent and a thermoplastic resin is melted and kneaded, injected into a mold composed of a fixed mold and a movable mold, and then the movable mold is core-backed to obtain the thermoplastic composition. Is molded while being foamed (Patent Documents 1 and 2).

Further, a technique is disclosed in which at least a part of the molding die is moved in a direction in which the cavity volume is reduced to compress the foamable resin in the cavity after the core back step and before the die opening (Patent Document 3). As a result, the edge portion of the foamable resin that has declined inward of the molded product is pushed out during the core back and advances to the void side, so that shape defects and deterioration of dimensional accuracy are suppressed.

On the other hand, there is disclosed a technique for further reducing the weight of a molded product and further saving raw materials by forming the molded product into fibers together with foaming (Patent Document 4).

Japanese Unexamined Patent Publication No. 2008-299201 Japanese Unexamined Patent Publication No. 2012-20544 Japanese Unexamined Patent Publication No. 2009-196284 Japanese Unexamined Patent Publication No. 2015-22381

However, with the fibrosis technique as described above, it has not been possible to obtain a foamed resin molded product having sufficiently excellent sound absorption.

An object of the present invention is to provide a foamed resin molded product having sufficiently excellent sound absorption and a method for producing the same.

The present invention
A thermoplastic resin composition containing a physical foaming agent and a thermoplastic resin is melted and kneaded, injected into a mold consisting of a fixed mold and a movable mold, and then the movable mold is cored in a direction opposite to that of the fixed mold. A method for producing a foamed resin molded product, which molds a thermoplastic resin composition while foaming and fiberizing it by backing it.
When the crystallization temperature of the thermoplastic resin composition at a cooling rate of 19 ° C./sec is Tccf (° C.), the core back is started when the temperature of the thermoplastic resin composition is Tccf-10 ° C. to Tccf + 20 ° C. The present invention relates to a method for producing a foamed resin molded product in which the movable mold is moved in the direction of the fixed mold to compress the fibrous resin in the mold, and the foamed resin molded product produced by the method.

According to the method for producing a foamed resin molded product according to the present invention, a foamed resin molded product having sufficiently excellent sound absorption can be produced.

It is the schematic which shows an example of the foam injection molding apparatus used in this invention. It is a schematic diagram for demonstrating the core back process and the compression process in the manufacturing method of the foamed resin molded article of this invention, and (A) shows the fixed type, the movable type and the melt (injection) just before the core back. It is a schematic diagram, (B) is a schematic diagram showing a fixed mold, a movable mold and a molded product after core back and immediately before compression, and (C) shows a fixed mold, a movable mold and a molded product after compression. It is a figure which shows an example of the gradient of the fiber density in the molded article. It is a figure which shows the gradient of the fiber density in an example of the molded article obtained by the manufacturing method of the foamed resin molded article of this invention. It is a figure which shows the gradient of the fiber density in an example of the molded article obtained by the manufacturing method of the foamed resin molded article of this invention. It is the schematic which shows an example of the vertical cross section with respect to the core back direction of the foamed resin molded article of this invention. It is a graph which shows the evaluation result of the sound absorption property about some examples of the foamed resin molded article obtained in an Example and a comparative example. It is a graph which shows the evaluation result of the sound absorption property about some examples of the foamed resin molded article obtained in an Example and a comparative example. A photomicrograph (SEM) of a cross section of the foamed resin molded product of Example 1A parallel to the core back direction at the T / 4 position is shown. A photomicrograph (SEM) of a cross section of the foamed resin molded product of Example 1A parallel to the core back direction at the T / 2 position is shown. A photomicrograph (SEM) of a vertical cross section of the foamed resin molded product of Example 1A with respect to the core back direction at the T / 4 position is shown. A photomicrograph (SEM) of a vertical cross section of the foamed resin molded product of Example 1A with respect to the core back direction at the T / 2 position is shown. A photomicrograph (SEM) of a cross section of the foamed resin molded product of Example 4A parallel to the core back direction at the T / 4 position is shown. A photomicrograph (SEM) of a cross section of the foamed resin molded product of Example 4A parallel to the core back direction at the T / 2 position is shown. A micrograph (SEM) of a cross section of the foamed resin molded product of Comparative Example 1 parallel to the core back direction at the T / 4 position is shown. A micrograph (SEM) of a cross section of the foamed resin molded product of Comparative Example 1 parallel to the core back direction at the T / 2 position is shown. A photomicrograph (SEM) of a vertical cross section of the foamed resin molded product of Comparative Example 1 with respect to the core back direction at the T / 4 position is shown. A photomicrograph (SEM) of a vertical cross section of the foamed resin molded product of Comparative Example 1 with respect to the core back direction at the T / 2 position is shown.

[Manufacturing method of foamed resin molded products]
A method for producing a foamed resin molded product according to the present invention will be described with reference to the drawings. It should be noted that the various elements shown in the drawings are merely schematically shown for the purpose of understanding the present invention, and the dimensional ratio, appearance, etc. may differ from the actual ones. The "vertical direction" and "horizontal direction" used directly or indirectly in the present specification correspond to the directions corresponding to the vertical direction and the horizontal direction in the drawing. Unless otherwise specified, common reference numerals shall indicate the same member, part, dimension or region in these figures.

As an example of the foam injection molding apparatus suitable for carrying out the method for producing the foamed resin molded product according to the present invention, FIG. 1 shows a schematic overall view of the configuration of the foam injection molding apparatus 1. This device 1 has a screw feeder 10 provided with a cylinder 11 and a screw shaft 12, and a hopper 13 for feeding raw materials is provided near the rear end portion (right side in FIG. 1) of the feeder 10. It has a structure. A check ring 14 and a conical head 15 are provided at the tip of the screw shaft 12, and the tip of the cylinder 11 is narrowed down to a conical shape in response to the shape of the head 15. Is provided with a nozzle 16. A high-pressure gas supply device 17 for supplying gas is provided between the hopper 13 and the nozzle 16 in the cylinder 11, so that a gaseous physical foaming agent can be supplied to the melt-kneaded product in the cylinder 11. ing.

A mold device 20 is arranged on the tip end side of the cylinder 11. The mold device 20 has a mold including a fixed mold 21 and a movable mold 22 that is movable with respect to the fixed mold 21, and a drive mechanism for driving the movable mold 22 (not shown). have. A cavity 23 that has the shape of a molded product when the mold is fastened is formed between the fixed mold 21 and the movable mold 22 of the mold device 20. The movable mold 22 is provided with a temperature / pressure sensor 24 for measuring the temperature and pressure of the thermoplastic resin composition injected into the cavity 23, a fixed mold 21 and a cooling mechanism 25 for cooling the movable mold 22. ing. The nozzle 16 is connected to the fixed mold 21, and a passage (hot runner) 21a communicating with the cavity 23 from the connecting portion of the nozzle 16 is formed.

The method for producing a foamed resin molded product according to the present invention includes a melt-kneading step, an injection step, a core back step, and a compression step.

(Melting and kneading process)
This step is a step of melting and kneading the thermoplastic resin composition containing the physical foaming agent and the thermoplastic resin. Specifically, a raw material other than the physical foaming agent, for example, a thermoplastic resin and an additive described later, is charged into the cylinder 11 from the hopper 13 of the foam injection molding apparatus 1 of FIG. 1, and is melted and kneaded while being melted and kneaded. The physical foaming agent is injected by the supply device 17.

From the viewpoint of fibrosis, the thermoplastic resin is a thermoplastic resin composition containing all the materials constituting the foamed resin molded product such as a physical foaming agent and the thermoplastic resin, and the crystallization temperature of the thermoplastic resin composition. It is preferably selected to have a storage elastic ratio of 1 × 10 ^{3 to} 5 × 10 ⁶ Pa, particularly 1 × 10 ⁴ to 1 × 10 ^{6 Pa in Tccs.}

The crystallization temperature Tccs of the thermoplastic resin composition can be measured by the following method.
The heat flow-temperature curve when the thermoplastic resin composition is heated to a temperature equal to or higher than the melting point and cooled at 10 ° C./min is determined by a differential scanning calorimeter (manufactured by PerkinElmer). The temperature at which this heat flow-temperature curve shows an endothermic peak is defined as the crystallization temperature Tccs (° C.).

The crystallization temperature Tccs of the thermoplastic resin composition is preferably 100 to 220 ° C, more preferably 100 to 210 ° C. When the thermoplastic resin is polypropylene as described later, the crystallization temperature Tccs of the thermoplastic resin composition is more preferably 100 to 155 ° C.

The storage elastic modulus of the thermoplastic resin composition at the crystallization temperature Tccs can be measured by the following method.
When the thermoplastic resin composition is heated to a temperature equal to or higher than the melting point and cooled at 2 ° C./min, the storage elastic modulus at Tccs is measured with a rotary viscometer (manufactured by Leometric).

The thermoplastic resin has a crystallization temperature of 90 to 210 ° C., preferably 90 to 200 ° C., and at the Tcps, 1 × 10 ³ to 1 × 10 ⁶ Pa, preferably 1 × 10 ^{4 to} 5 ×. preferably a polymer having a 10 5 ^Pa storage elastic modulus is used. When the thermoplastic resin is polypropylene as described later, the crystallization temperature Tcps of the thermoplastic resin is more preferably 95 to 135 ° C. If the Tcps of the thermoplastic resin is too high or the storage elastic modulus at the above temperature is too high, only a foam having a relatively large cell wall thickness between adjacent cells can be obtained, and sufficient fibrosis does not occur. .. If the Tcps of the thermoplastic resin is too low or the storage elastic modulus at the above temperature is too low, the cells will be coalesced to obtain a foam having a relatively large cell diameter, and sufficient fibrosis will occur. Absent.

The crystallization temperature Tcps of the thermoplastic resin can be measured by the same method as the crystallization temperature Tccs of the thermoplastic resin composition except that the thermoplastic resin is heated.

The storage elastic modulus of the thermoplastic resin at Tcps (° C.) is the crystallization temperature Tccs of the thermoplastic resin composition, except that the thermoplastic resin is heated and the measurement temperature of the storage elastic modulus is Tcps (° C.). It can be measured by the same method as the storage elastic modulus in.

As the thermoplastic resin, all kinds of polymers are used, for example, polyester resins such as polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polylactic acid (PLA)). Polyethylene resins (PA) such as PA6, PA66, PA11, PA12, PA6T, PA9T, MXD6, polyether resins such as polyetheretherketone (PEEK) and polyphenylene ether (PPE), and polyphenylene terephthalide (PPS) are used. To. Two or more types of thermoplastic resins having different Tcps, storage elastic modulus, composition (type), etc. may be contained, and in that case, each thermoplastic resin in the mixed resin has the above-mentioned crystallization temperature and storage elastic modulus, respectively. It is preferable to have it. Preferred thermoplastic resins are polypropylene, polyamide resins (PA), polyphenylene sulfide (PPS).

The physical foaming agent physically causes foaming in the thermoplastic resin, and examples thereof include nitrogen gas and carbon dioxide gas.

The content of the physical foaming agent is usually 0.1 to 3.0 parts by weight, preferably 0.1 to 2.0 parts by weight, based on 100 parts by weight of the thermoplastic resin.

The thermoplastic resin composition may further contain additives such as a crystal nucleating agent and reinforcing fibers. From the viewpoint of fibrosis, it is preferable to contain a crystal nucleating agent.

The crystal nucleating agent is an organic compound capable of forming a three-dimensional network structure by self-assembly by hot melting and cooling and / or by applying melt kneading and shear flow. By adding such a crystal nucleating agent to the thermoplastic resin and subjecting it to hot melting and cooling and / or melt kneading and shear flow, the growth of fine and uniform crystals of the thermoplastic resin is promoted. Along with this, the bubbles generated by crystallization are also made finer, so that the bubbles become the starting point at the time of core-back type foam injection molding, and further fine fiber formation is achieved.

As the crystal nucleating agent, any crystal nucleating agent used in the fields of automobile parts and home appliance parts can be used. As the crystal nucleating agent, an organic crystal nucleating agent is preferably used from the viewpoint of fibrosis. Specific examples of the organic crystal nucleating agent include sorbitol-based compounds, particularly aromatic ring-containing sorbitol-based compounds and aliphatic ring-containing sorbitol-based compounds. As the crystal nucleating agent, a sorbitol-based compound is preferable, and an aromatic ring-containing sorbitol-based compound is more preferable.

A preferable specific example of the aromatic ring-containing sorbitol-based compound is a sorbitol-based compound represented by the general formula (1).

In formula (1), R ¹ and R ² are independently hydrogen atoms, linear or branched alkyl groups having 1 to 4 carbon atoms, and linear or branched chain carbon atoms 1. It is an alkoxy group of ~ 4, a linear or branched-chain alkoxycarbonyl group having 1 to 4 carbon atoms, or a halogen atom. The bond positions of R ¹ and R ² on the benzene ring are not particularly limited and may be independently, for example, the ortho position, the meta position and the para position. The bond positions of R ¹ and R ^{2 on} the benzene ring are independent of each other, and when m is 1, the para position is preferable, and when m is 2, the meta position and the para position are preferable.
Preferred R ¹ and R ² are independently hydrogen atoms or linear or branched alkyl groups having 1 to 4 carbon atoms (eg, methyl group, ethyl group, propyl group, butyl group). , More preferably a linear or branched alkyl group having 1 to 4 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, a butyl group).

R ³ is a hydrogen atom, a linear or branched chain alkyl group having 1 to 4 carbon atoms, a linear or branched chain alkenyl group having 2 to 4 carbon atoms, or a linear or branched chain. It is a hydroxyalkyl group having 1 to 4 carbon atoms.
Preferred R ³ are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, a butyl group), and more preferably. Is a hydrogen atom.

m and n are independently integers of 1 to 5, preferably 1 or 2. when m is an integer of 2 or more, two R ¹ may form a tetralin ring together with a benzene ring to which they are attached. when n is an integer of 2 or more, two R ² may form a tetralin ring together with a benzene ring to which they are attached.

p is 0 or 1, preferably 1.

As an aromatic ring-containing sorbitol-based compound, commercially available gelol MD (manufactured by Shin Nihon Kagaku Co., Ltd.) (in formula (1), R ¹ = R ² = methyl group (m = n = 1 at para position), R ³ = hydrogen Atomic, p = 1), Gelol D (manufactured by Shin Nihon Kagaku Co., Ltd.) (In formula (1), R ¹ = R ² = hydrogen atom, R ³ = hydrogen atom, p = 1), Gelol DXR (Shin Nihon Kagaku Co., Ltd.) (Manufactured by) (In formula (1), R ¹ = R ² = methyl group (m = n = 2 at meta and para positions), R ³ = hydrogen atom, p = 1), gelol E-200 (Shin Nihon Kagaku) Millad NX8000 (manufactured by Milliken Chemical) (in formula (1), R ¹ = R ² = propyl group (para position at m = n = 1), R ³ = propyl group, p = 1), RiKAFAST AC (manufactured by Shin Nihon Kagaku Co., Ltd.) is available.

From the viewpoint of further improving the sound absorption property, the crystal nucleating agent is preferably used in the form of a crystal nucleating agent masterbatch (pellet) which is previously melt-kneaded, cooled and pulverized together with a thermoplastic resin. The content of the crystal nucleating agent in the crystal nucleating agent masterbatch is usually 1 to 40% by weight based on the total amount of the masterbatch.

The content of the crystal nucleating agent in the thermoplastic resin composition is usually 0.1 to 1.0 parts by weight, preferably 0.3 to 0.8 parts by weight, based on 100 parts by weight of the thermoplastic resin. is there.

The melt-kneading temperature, that is, the cylinder temperature is not particularly limited as long as the thermoplastic resin composition is sufficiently melted, and is preferably Tccf + 70 to Tccf + 130 ° C. with respect to the crystallization temperature Tccf of the thermoplastic resin composition described later. , More preferably Tccf + 80 to Tccf + 120 ° C.

(Injection process)
This step is a step of injecting the melt of the thermoplastic resin composition obtained in the melt-kneading step into the mold. Specifically, the melt is injected from the nozzle 16 of the foam injection molding apparatus 1 of FIG. 1 into the cavity 23 in the mold including the fixed mold 21 and the movable mold 22. In FIG. 1, the cavity 23 has a rectangular parallelepiped shape, but is not limited to this, and may have a desired shape based on the target molded product shape.

The mold temperature is preferably Tccf-70 to Tccf-20 ° C., more preferably Tccf-70 to Tccf-40 ° C., relative to the crystallization temperature Tccf of the thermoplastic resin composition described later.

The injection speed is not particularly limited, and is usually 20 to 200 mm / sec, preferably 30 to 150 mm / sec. The injection amount is an amount that fills the cavity 23.

The initial thickness m (maximum thickness in the thickness direction) of the cavity 23 is usually 1 to 10 mm, preferably 1 to 5 mm. The thickness direction means the moving direction of the movable type 22 in the core back process described later, that is, the direction parallel to the core back direction.

(Core back process)
This step is a step of foaming and fiberizing the melt injected in the injection step by core backing the movable mold 22. Specifically, as shown in FIG. 2 (A), after injecting the melt of the thermoplastic resin composition, the pressure is held in the mold, and as shown in FIG. 2 (B), the core back is pressed at a specific timing. Perform foaming and fibrosis. The core back means moving the movable mold 22 in the direction opposite to the direction of the fixed mold 21 in order to increase the volume of the cavity 23. This reduces the pressure in the cavity 23 and promotes the foaming of the melt, resulting in fibrosis. Filamentation means that the cell wall is stretched in the core back direction and broken in the direction perpendicular to the core back direction to form fibers. Fibrosis is achieved so that the fibers formed are oriented parallel to the core back direction. Therefore, the core back direction can be detected from the fiber orientation direction. The orientation direction of the fibers is also parallel to the thickness direction of the foamed resin molded product. In the present specification, parallel does not mean that the angle formed by the two directions must be exactly 0 °, and a range of about ± 5 ° is allowed. FIG. 2 is a schematic view for explaining a core back process and a compression process in the method for producing a foamed resin molded product of the present invention. Specifically, FIG. 2 (A) shows the fixed mold, the movable mold and the melt (injection) immediately before the core back, and FIG. 2 (B) shows the fixed mold, the movable mold and the molded product immediately after the core back and immediately before the compression. 2 (C) shows a fixed mold, a movable mold and a molded product after compression, and shows a gradient of fiber density in the molded product.

In this step, when the crystallization temperature of the thermoplastic resin composition at a cooling rate of 19 ° C./sec is Tccf (° C.), the temperature of the injected thermoplastic resin composition (melt) is Tccf. Start when the temperature is -10 to Tccf + 20 ° C., preferably Tccf-5 to Tccf + 20 ° C., preferably Tccf to Tccf + 20 ° C. By starting the core back at such a timing, it is possible to prevent the formed cells from coalescing while sufficiently forming the cells by foaming in the initial stage of the core back. Therefore, since a sufficient number of cells are finely dispersed at the initial stage of the core back, the cell wall can be stretched in the core back direction and broken in the direction perpendicular to the core back direction by the subsequent core back. .. As a result of these, it is considered that fibrosis is achieved. If the core back start temperature is too low, cells cannot be sufficiently formed at the initial stage of core back, so that only a foam having a relatively large cell wall thickness between adjacent cells can be obtained, and sufficient fibrosis does not occur. If the core back start temperature is too high, cell coalescence proceeds at the initial stage of core back, so that only a foam having a relatively large cell diameter can be obtained, and sufficient fibrosis does not occur.

In the present invention, even if the core back timing is determined based on the crystallization temperature measured at a relatively slow cooling rate, sufficient fibrosis is not achieved. The fine dispersion of a sufficient number of cells in the early stage of core back is considered to be based on the crystallization of the thermoplastic resin composition. Therefore, for example, even if the core back timing is expressed based on the crystallization temperature measured at a cooling rate of 100 ° C./min or less, the cooling rate does not match the actual situation of foam injection molding with core back at all. It is considered that crystallization does not occur sufficiently, and as a result, fibrosis is not sufficiently achieved.

The crystallization temperature Tccf of the thermoplastic resin composition can be measured by the following method.
The heat flow-temperature curve when the thermoplastic resin composition is heated to a temperature equal to or higher than the melting point and cooled at 19 ° C./sec is determined by a high-speed differential scanning calorimeter (manufactured by METTLER TOLEDO). The temperature at which this heat flow-temperature curve shows an endothermic peak is defined as the crystallization temperature Tccf (° C.).

The crystallization temperature Tccf of the thermoplastic resin composition is preferably 80 to 190 ° C, more preferably 80 to 180 ° C. When the thermoplastic resin is polypropylene, the crystallization temperature Tccf of the thermoplastic resin composition is more preferably 80 to 135 ° C.

By observing the temperature of the thermoplastic resin composition with the temperature / pressure sensor 24 at the time of holding pressure, the timing of starting core back can be measured.
The holding pressure and the holding time are not particularly limited as long as the core back can be started at the above timing. The holding pressure is usually 10 to 80 MPa, preferably 20 to 60 MPa. The holding time is usually 1 to 10 seconds, preferably 2 to 7 seconds.

At the start of core back, the cell diameter in the thermoplastic resin composition is preferably 30 μm or less, more preferably 20 μm or less, from the viewpoint of fine fiber formation.

The cell diameter in the thermoplastic resin composition at the start of the core back is determined by performing the melt-kneading step and the injection step by the same method as the method for producing the foamed resin molded product according to the present invention, except that the core back is not performed. It can be measured using a sample obtained by cooling the melt of the thermoplastic resin composition as it is in the mold. Specifically, the above sample is cut in a direction perpendicular to the core back direction, and a micrograph of the obtained cross section is taken. In the photograph, the diameter (maximum diameter) of any 100 cells is measured in a region separated from the skin layer by 500 μm or more, and the maximum value is obtained.

The distance (that is, the core back amount) k1 (see FIG. 2B) for moving the movable type 22 in the direction opposite to the direction of the fixed type 21 is relative to the final core back amount K (mm) of the movable type. It is usually 1.1 × K to 2 × K, and is preferably 1.1 × K to 1.6 × K, particularly from the viewpoint of further improving the sound absorption of high-frequency sound (frequency 1000 Hz or more and 5000 Hz or less). It is preferably 1.3 × K to 1.45 × K. From the viewpoint of further improving the sound absorption of medium frequency sound (frequency 500 Hz or more and less than 1000 Hz) and low frequency sound (frequency 200 Hz or more and less than 500 Hz), the core back amount k1 is preferably 1.3 × K to 1.6 × K. is there. From the viewpoint of further improving the sound absorption of the medium frequency sound, the core back amount k1 is preferably 1.4 × K to 1.6 × K. The final core back amount K (mm) of the movable type is the final position of the movable mold 22 after the movable mold 22 has moved in the direction of the fixed mold in the compression step described later, and the core back in this step. It is the distance from the initial position of the movable mold 22 immediately before the operation.

The time required for core back is usually 0.1 to 2 seconds, preferably 0.2 to 1 second.

In the core back process, the mold temperature is preferably maintained within the same temperature range as in the injection process.

(Compression process)
This step is a step of compressing the fibrous resin in the mold by moving the movable mold 22 in the direction of the fixed mold 21. Normally, after finishing the core back and securing a holding time for stopping the movement of the movable type 22, as shown in FIGS. 2B to 2C, the moving type 22 is moved in the direction of the fixed type 21. Move to. As a result, the contact between the fibers is promoted, and as shown in FIG. 2C, the fiber dense region 23 is formed in the parallel cross section with respect to the core back direction (hereinafter, may be simply referred to as “parallel cross section”). .. The fiber dense region is a region in which the fiber density is relatively higher than that of the surrounding fiber sparse region (adjacent fiber sparse region) 24 and the fiber orientation direction is different in the parallel cross section. In such a fiber dense region 23, the fibers have a morphology that is non-linearly oriented in a parallel cross section, and specifically, a morphology that is curved and oriented, a morphology that is randomly oriented, or a composite form thereof. Has. On the other hand, in the sparse region 24 around the dense region, the fiber density is relatively low, and the fibers are oriented in substantially one direction in the parallel cross section, and more specifically, they are oriented in a substantially linear shape, which is more specific. Is oriented parallel to the core back direction. The linear shape does not mean a strictly straight line shape, but may be a straight line as a whole. Parallel does not mean that the angle between the two directions must be exactly 0 °, but that a range of about ± 5 ° is acceptable. The fact that the fibers are oriented in substantially one direction does not mean that all the fibers must be oriented in exactly one direction, but that they are oriented in one direction as a whole. In this way, inside the foamed resin molded product, the fibrous dense region as described above is integrally formed together with the sparse region around it, and the resonator effect is exhibited at the boundary between them, so that sufficient sound absorption is obtained. It is thought that it will be done. When the compression step is not performed, a molded product having a fiber density substantially uniform over the entire length in the core back direction and a fiber orientation direction substantially uniform over the entire length in the core back direction can be obtained, and sufficient sound absorption is obtained. I can't get it.

The fiber density is the degree of density of fibers, and is determined by using the void length in a parallel cross section as an index. The larger the void length, the lower the fiber density, which means that the region is sparse. On the other hand, the smaller the void length, the higher the fiber density, which means that the region is dense.

The void length can be calculated from a micrograph (SEM) of a molded resin foam in parallel cross section. Specifically, the maximum length of each void in the core back direction is measured for any 100 voids in the photograph, and the average value thereof is obtained. The voids exist between the fibers at a relatively low brightness, and can be easily identified by the difference in brightness from the surrounding fibers (high brightness) in the photograph.

The retention time is typically 0.1-4.0 seconds, preferably 0.3-3.5 seconds.

The amount of movement (compression amount) k2 of the movable type 22 in the fixed type direction (see FIGS. 2 (B) to 2 (C)) is not limited as long as the effect of improving the sound absorption property of the present invention can be obtained, and is usually limited. The following relational expression is satisfied.
k2 = core back amount of the core back k1-final core back amount of the movable type K

The time (movement time) required for the movable type 22 to move in the fixed type direction is usually 0.05 to 1 second, preferably 0.05 to 0.5 seconds.

The foaming ratio is a value "(K + m) / m" calculated based on the final core back amount K of the movable type 22 and the initial thickness m of the cavity, and is usually 3 to 8 times, more preferably. It is 4 to 6 times.

In this step, compression may be performed in one step or in multiple steps. By performing the compression in multiple stages, the sound absorption property can be further improved. Compressing in multiple stages means compression until the movable mold 22 reaches the final core back amount K (“target final thickness T in foamed resin molded product”-“initial thickness m of cavity”). It means that the movement of is not performed continuously, but intermittently. In other words, after the movable type 22 starts the compression movement, a holding time for stopping the compression movement is secured at least once while reaching the final core back amount K, and the compression movement is continued after the holding. .. The number of compression transfer stages is not particularly limited as long as it is 2 or more, and may be appropriately determined according to the final core back amount.

In this step, the mold temperature is preferably maintained within the same temperature range as in the injection step.

(Cooling process)
After the compression is completed, the fibrous resin is held as it is in the mold to be cooled, and then the mold is opened to obtain a foamed resin molded product.

[Foam resin molded product]
The foamed resin molded product produced by the above method of the present invention has achieved fibrosis as described above inside, and as shown in FIG. 2C, the fibrous dense region 23 has a parallel cross section. Is formed. The inside is a region separated from the skin layer on the surface of the molded product by 100 μm or more, preferably 200 μm or more.

In the present invention, the fiber is not only the fibrous material 30, but also the cell wall, as shown in FIG. 5, which shows a vertical cross section (hereinafter, may be simply referred to as “vertical cross section”) of the foamed resin molded product with respect to the core back direction. It includes the aspherical cell wall marks 31 and 32 formed by the fracture, and does not include the annular cell wall 33 that remains without being fractured. In the present invention, the fibrous material 30 and the aspherical cell wall marks 31 and 32 are solid in the vertical cross section of the foamed resin molded product, and are not hollow.

The foamed resin molded product of the present invention does not necessarily have to be entirely fibrous, and for example, as shown in FIG. 5, it prevents the foamed resin molded product from having an annular cell wall 33 in part. is not it. The total number of annular cell walls 33 may be 10 or less in 100 micrographs (magnification of 500 times) of an arbitrary cross section obtained by cutting the foamed resin molded product perpendicularly to the core back direction.

In FIG. 2C, the dense region 23 is formed substantially in the central portion in the core back direction M, but is not limited to this, as long as the dense region 23 and the sparse region 24 around it are formed. , May be formed in any position. Specifically, for example, the dense region 23 may be formed at a position closer to the movable mold 22 as shown in FIG. 3 than the central portion thereof, or may be formed at a position closer to the fixed mold 21. Good.

In the foamed resin molded product of the present invention, the dense regions 23 are formed one by one in FIGS. 2 (C) and 3, but the number of dense regions 23 is the dense regions 23 and the sparse regions 24 around them. Is not particularly limited as long as is formed, and may be two or three or more as shown in FIG. 4, for example.

In the foamed resin molded product of the present invention, the surrounding sparse regions 24 are formed on both sides of the dense regions 23 in FIGS. 2 (C), 3 and 4, but only on one side of the dense regions 23. It may be formed.

In the foamed resin molded product of the present invention, the positions and the number of dense regions 23 formed are various and unpredictable, and the boundary between the fibrous dense regions 23 and the surrounding sparse regions 24 is not always clear. .. Therefore, it can be said that it is impractical to directly specify the foamed resin molded product of the present invention by its structure or characteristics, but the foamed resin molded product according to one embodiment obtained by the production method of the present invention is described below. Shown in.

The foamed resin molded product of the present embodiment is located at a position of T / 4 or T / 2 from the end face in the core back direction in a parallel cross section when the length of the foamed resin molded product in the core back direction is T (mm). It has a dense region 23 at one of the positions and a sparse region 24 at the other. Foamed resin molded article of the present embodiment, for example, in FIG foamed resin molded article (I) and having a dense region 23 only one position of T / 2 (P ₂₎ as shown in FIG. 2 (C) 3 As shown, it includes a foamed resin molded article (II) having only one dense region 23 at the T / 4 position (P _1).

P ₁ is a measurement point at a distance of T / 4 from the end face in the core back direction and corresponding to the center of the molded product (for example, in FIGS. 2 (C) and 3 in the vertical direction and the front and back directions).
P ₂ is a measurement point at a distance of T / 2 from the end face in the core back direction and corresponding to the center of the molded product (for example, in FIGS. 2 (C) and 3 in the vertical direction and the front and back directions).

(Effervescent resin molded product (I))
The foamed resin molded product (I) has a length of the molded product in the core back direction of T (mm), a position of T / 4 (P ₁ ) and a position of T / 2 (P ₂ ) from the end face in the core back direction. When the void lengths in the above are LT _{/ 4} (μm) and LT _{/ 2} (μm), respectively, LT _{/ 4} / _{LT / 2} is 1.5 or more, particularly 1.5 to 5, which is preferable. Is 1.5 to 3, more preferably 1.8 to 3. The foamed resin molded product (I) is composed of a sparse region 24 at _{the T / 4 position (P 1} ) and a dense region 23 at _{the T / 2 position (P 2).}

In the present specification, the void lengths LT _{/ 4} (μm) and LT _{/ 2} (μm) can be calculated by the above-mentioned method from the parallel cross sections at each position.

In the foamed resin molded product (I), the _{LT / 4} is usually more than 20 μm, particularly 25 to 100 μm, and is preferably 25 to 80 μm, more preferably 25 to 50 μm from the viewpoint of further improving the sound absorption property.
The _{LT / 2} is usually 20 μm or less, particularly 1 to 20 μm, and is preferably 5 to 20 μm, more preferably 10 to 20 μm from the viewpoint of further improving the sound absorption property.

In the foamed resin molded product (I), when the average diameters of the fibers at the _{T / 4 position (P 1} ) and the T / 2 position (P _{2 ) are DT / 4} and _{DT / 2} , respectively, the following Is the street:
The _{DT / 4} is usually 8 μm or less, particularly 0.05 to 8 μm, and is preferably 0.1 to 6 μm, more preferably 0.5 to 5 μm from the viewpoint of further improving the sound absorption property.
The _{DT / 2} is usually 10 μm or less, particularly 0.1 to 10 μm, and is preferably 0.5 to 8 μm, more preferably 1 to 5 μm from the viewpoint of further improving the sound absorption property.

In the present specification, the average diameters _{DT / 4} and _{DT / 2} of the fibers at the T / 4 position (P ₁ ) and the T / 2 position (P ₂ ) are calculated from the micrographs of the vertical cross section at each position. The value is used. Specifically, the fiber diameters of any 100 fibers are measured in the photograph, and the average value thereof is obtained. As shown in FIG. 5, the fiber diameter is the longest diameter d1 when the fiber is fibrous 30, and the maximum thickness d2 of the cell wall mark when the fiber is acyclic cell wall marks 31 and 32. , D3.

In the foamed resin molded product (I), when the number of fibers at the _{T / 4 position (P 1} ) and the T / 2 position (P _{2 ) is NT / 4} and _{NT / 2} , respectively, the following Street:
_{NT / 4} is usually 20 pieces / 100 μm ² or more, particularly 20 to 400 pieces / 100 μm ^{2 , preferably 40 to 300 pieces / 100 μm 2} , more preferably 40 to 200 pieces from the viewpoint of further improving sound absorption. / 100 μm ² .
N _{T / 2} is usually 40/100 [mu] m ² or more, in particular at 40 to 500 pieces / 100 [mu] m ^2, from the viewpoint of further improvement of the sound absorption 50 to 400 pieces / 100 [mu] m ^2, more preferably 50 to 200 / 100 μm ² .

In the present specification, the number of fibers at the T / 4 position (P ₁ ) and the T / 2 position (P _{2 ), NT / 4} and _{NT / 2,} are cross sections perpendicular to the core back direction at each position. The values based on the micrographs of are used. Specifically, as shown in FIG. 5, the total number of fibers 30, 31 and 32 is obtained in an arbitrary region, and the total number is divided by the area of the region. In the present invention, the average value of "the number of fibers per unit area" in 10 arbitrary regions is used.

(Foam resin molded product (II))
The foamed resin molded product (II) has a length of the molded product in the core back direction of T (mm), a position of T / 4 (P ₁ ) and a position of T / 2 (P ₂ ) from the end face in the core back direction. When the void lengths in the above are LT _{/ 4} (μm) and LT _{/ 2} (μm), respectively, LT _{/ 4} / _{LT / 2} is 0.7 or less, particularly 0.01 to 0.7. , Preferably 0.1 to 0.7, more preferably 0.3 to 0.7. The foamed resin molded product (II) is composed of a dense region 23 at _{the T / 4 position (P 1} ) and a sparse region 24 at _{the T / 2 position (P 2).}

In the foamed resin molded product (II), LT _{/ 4} is within the same range as _{LT / 2} of the foamed resin molded product (I).
LT _{/ 2} is within the same range as _{LT / 4} of the foamed resin molded product (I).

In the foamed resin molded product (II), when the average diameters of the fibers at the _{T / 4 position (P 1} ) and the T / 2 position (P _{2 ) are DT / 4} and _{DT / 2} , respectively, the following Is the street:
_{DT / 4} is within the same range as _{DT / 2} of the foamed resin molded product (I).
_{DT / 2} is within the same range as _{DT / 4} of the foamed resin molded product (I).

In the foamed resin molded product (II), when the number of fibers at the _{T / 4 position (P 1} ) and the T / 2 position (P _{2 ) is NT / 4} and _{NT / 2} , respectively, the following Street:
_{NT / 4} is within the same range as _{NT / 2} of the foamed resin molded product (I).
_{NT / 2} is within the same range as _{NT / 4} of the foamed resin molded product (I).

[Use]
The foamed resin molded product of the present invention is excellent in sound absorption of at least high frequency sound (frequency 1000 Hz or more and 5000 Hz or less) by being manufactured by the above-mentioned manufacturing method. The sound absorption coefficient of such a foamed resin molded product at, for example, 4000 Hz is usually 0.60 or more, preferably 0.65 or more, more preferably 0.73 or more, and further preferably 0.80 or more.

The foamed resin molded product of the present invention is manufactured by increasing the core back amount within a predetermined range in the above-mentioned manufacturing method, thereby not only absorbing high-frequency sound (frequency 1000 Hz or more and 5000 Hz or less) but also low frequency. It is also excellent in sound absorption of wave sound (frequency 200 Hz or more and less than 500 Hz). The sound absorption coefficient of such a foamed resin molded product at, for example, 200 Hz is usually 0.07 or more, preferably 0.09 or more, and more preferably 0.12 or more.

The foamed resin molded product of the present invention is also manufactured by further increasing the core back amount within a predetermined range in the above-mentioned manufacturing method, thereby producing high-frequency sound (frequency 1000 Hz or more and 5000 Hz or less) and low-frequency sound (frequency 200 Hz or more). It is excellent not only in sound absorption of medium frequency sound (frequency 500 Hz or more and less than 1000 Hz) but also in sound absorption of medium frequency sound (frequency 500 Hz or more and less than 1000 Hz). The sound absorption coefficient of such a foamed resin molded product at, for example, 800 Hz is usually 0.18 or more, preferably 0.20 or more, and more preferably 0.22 or more.

The high-frequency sound, medium-frequency sound, and low-frequency sound absorbed by the foamed resin molded product of the present invention correspond to the following sounds in automobile applications:
High frequency sound-engine radiation sound;
Medium frequency sound-road noise;
Low frequency sound-engine vibration, intake and exhaust sound.

[Example 1A]
(Crystal Nucleation Masterbatch)
100 parts by weight of polypropylene pellets as a thermoplastic resin (NBX04G; manufactured by Japan Polypropylene Corporation; MFR 36 g / 10 minutes (230 ° C), Tcps 124 ° C) and 5.0 parts by weight of gelol MD (manufactured by Shin Nihon Kagaku Co., Ltd.) as a crystal nucleating agent. Was melt-kneaded, cooled and pulverized to obtain a crystal nucleating agent masterbatch. Storage modulus at crystallization temperature Tcps polypropylene pellets was 1 × ¹⁰ 5 Pa.

(Melting and kneading process)
Dry blend of crystal nucleating agent masterbatch and polypropylene pellets (NBX04G; manufactured by Japan Polypropylene Corporation; MFR 36 g / 10 minutes (230 ° C.), Tcps 124 ° C.) at a ratio of polypropylene: crystal nucleating agent to a weight ratio of 100: 0.5. Then, it was put into the cylinder 11 from the hopper 13 of the foam injection molding apparatus 1 of FIG. While melting and kneading these mixtures in the cylinder 11 at 185 ° C. (= Tccf + 92 ° C.), nitrogen gas as a physical foaming agent was added to 100 parts by weight of the thermoplastic resin by the high pressure gas supply device 17 by 0.132 weight. Partially injected. When obtained was measured crystallization temperature Tccf and Tccs thermoplastic resin composition is 93 ° C. and 124 ° C., respectively, the storage elastic modulus at Tccs was 1 × ¹⁰ 5 Pa.

(Injection process)
The melt in the cylinder 11 was injected into the cavity 23 between the molds of the fixed mold 21 and the movable mold 22. The mold temperature was 40 ° C. (= Tccf-53 ° C.), the injection speed was 40 mm / sec, and the thickness of the cavity was 2 mm.

(Core back process)
After injection, the melt is held at 40 MPa for 5.8 seconds in the mold cavity, and then the movable mold 22 is cored back by 10 mm (k1) for 0.5 seconds in the direction opposite to the direction of the fixed mold 21. This resulted in foaming and fibrosis, followed by holding the fibrous product for 0.5 seconds. At the start of core back, the temperature of the melt was 94 ° C (= Tccf + 1 ° C), and the cell diameter in the melt was 20 μm or less. The mold was maintained at 40 ° C. in this step.

(Compression process)
Then, the fibrous material was compressed by moving the movable mold 22 in the direction of the fixed mold 21 over 0.1 seconds by 2 mm (k2). The final core back amount (K) was 8 mm, and the foaming ratio was 5 times. The mold was maintained at 40 ° C. in this step.

(Cooling process)
After the core back was completed, the fibrous product was cooled by holding it as it was in a mold at 40 ° C. Then, the mold was opened to obtain a fibrous foamed resin molded product.

[Examples 2A to 4A and Comparative Example 1]
A foamed resin molded product was produced by the same method as in Example 1A except that the molding conditions shown in Table 1 were adopted.
In Comparative Example 1, the core back step was performed under the conditions shown in Table 1, and compression was not performed.

[Comparative Examples 2 and 3]
A foamed resin molded product was produced by the same method as in Example 1A except that the temperature of the melt at the start of core back was Tccf-11 ° C. or Tccf + 22 ° C.
In Comparative Example 2 (Tccf-11 ° C.), foaming could not be performed. In Comparative Example 3 (Tccf + 22 ° C.), the core layer was hollowed out (hollowed out), and a foamed resin molded product could not be obtained.

[Sound absorption]
The vertical incident sound absorption coefficient of the foamed resin molded product was measured. Specifically, the molded product was used so that its core back direction was parallel to the vertical direction for sound absorption coefficient measurement. The measurement conditions are shown below, and the results are shown in FIGS. 6 to 7 and Table 1.
Measuring device: Acoustic impedance tube device with φ (diameter) 40 mm (Nitto Boseki Acoustic Engineering Co., Ltd.)
Measurement conditions: Sample size; φ (diameter) 40 mm, skin layer on the sound wave incident side removed (sound absorption at 4000 Hz)
◎◎; 0.80 or more;
◎; 0.73 or more;
◯; 0.65 or more;
Δ; 0.60 or more (no problem in practical use);
X; less than 0.60 (there is a problem in practical use).
(Sound absorption at 800 Hz)
◎; 0.22 or more;
◯; 0.20 or more;
Δ; 0.18 or more (no problem in practical use);
X; less than 0.18 (there is a problem in practical use).
(Sound absorption at 200 Hz)
◎; 0.12 or more;
○; 0.09 or more;
Δ; 0.07 or more (no problem in practical use);
×; Less than 0.07 (There is a problem in practical use);

(Cross section photography)
The foamed resin molded articles obtained in Examples 1A and 4A and Comparative Example 1 were cut in parallel and perpendicular to the core back direction, and micrographs of their cross sections were taken. These photographs were taken at the position of T / 4 and the position of T / 2 from the movable mold with respect to the length T (mm) in the core back direction of the molded product.
For the foamed resin molded product of Example 1A, micrographs (SEMs) of parallel cross sections with respect to the core back direction at the T / 4 position and the T / 2 position are shown in FIGS. 8A and 8B, respectively, and the void length in the core back direction is shown. Was measured by the method described above. Photomicrographs (SEMs) of cross sections perpendicular to the core back direction at the T / 4 and T / 2 positions are shown in FIGS. 8C and 8D, respectively, and the average diameter of the fibers and the number of fibers were measured by the methods described above.
For the foamed resin molded product of Example 4A, micrographs (SEMs) of parallel cross sections with respect to the core back direction at the T / 4 position and the T / 2 position are shown in FIGS. 9A and 9B, respectively, and the void length in the core back direction is shown. Was measured by the method described above.
For the foamed resin molded product of Comparative Example 1, micrographs (SEMs) of parallel cross sections with respect to the core back direction at the T / 4 position and the T / 2 position are shown in FIGS. 10A and 10B, respectively, and the void length in the core back direction is shown. Was measured by the method described above. Photomicrographs (SEMs) of cross sections perpendicular to the core back direction at the T / 4 and T / 2 positions are shown in FIGS. 10C and 10D, respectively, and the average diameter of the fibers and the number of fibers were measured by the methods described above.

[Measurement]
Melt crystallization temperature Tccs and Tccf, storage modulus of melt at Tccs (° C), thermoplastic resin crystallization temperature Tcps, thermoplastic resin storage modulus at Tcps, melt at coreback start The temperature, the storage elastic modulus of the melt at the start of core back, the cell diameter in the melt at the start of core back, the average diameter of fibers, and the number of fibers were measured by the above-mentioned methods.
For the foamed resin molded products obtained in all the examples, in 100 micrographs (magnification of 500 times) of an arbitrary cross section cut perpendicular to the core back direction, holes were formed in the inner depth of the annular cell wall 33. The total number of cells that were closed cells was 0.

The foamed resin molded product produced by the method for producing a fibrous foamed resin molded product based on the injection molding method according to the present invention is useful as a shock absorber, a heat insulating material, and a sound absorbing material.

1: Foam injection molding device 10: Screw feeder 11: Cylinder 12: Screw shaft 13: Hopper 14: Check ring 15: Conical head 16: Nozzle 17: High pressure gas supply device 20: Mold device 21: Fixed mold 22: Movable type 23: Cavity 24: Temperature and pressure sensor 25: Cooling mechanism 30: Fibrous material 31:32: Non-annular cell wall mark 33: Annular cell wall

Claims (14)

A thermoplastic resin composition containing a physical foaming agent and a thermoplastic resin is melted and kneaded, injected into a mold consisting of a fixed mold and a movable mold, and then the movable mold is cored in a direction opposite to that of the fixed mold. A method for producing a foamed resin molded product, which molds a thermoplastic resin composition while foaming and fiberizing it by backing it.
When the crystallization temperature of the thermoplastic resin composition at a cooling rate of 19 ° C./sec is Tccf (° C.), the core back is started when the temperature of the thermoplastic resin composition is Tccf-10 ° C. to Tccf + 20 ° C. After finishing, move the movable mold toward the fixed mold to compress the fibrous resin in the mold.
The core back amount k1 in the core back is 1.1 × K to 2 × K with respect to the final core back amount K (mm) of the movable type.
After the completion of the core back and before the compression of the fibrous resin, a holding time for stopping the movement of the movable type is secured.
In the foamed resin molded product, the movement of the movable mold in the fixed mold direction promotes contact between the fibers.
The foamed resin molded product has one or more fiber dense regions and a fiber sparse region around the fiber dense region in a cross section parallel to the core back direction.
A method for producing a foamed resin molded product, wherein the one or more fiber dense regions are regions in which the fiber density is relatively higher than the fiber sparse regions and the fiber orientation directions are different in the parallel cross section. The method for producing a foamed resin molded product according to claim 1 , wherein the holding time is 0.1 to 4.0 seconds. The method for producing a foamed resin molded product according to claim 1 or 2 , wherein the amount of movement k2 of the movable mold in the fixed mold direction satisfies the following relational expression.
k2 = core back amount of the core back k1-final core back amount of the movable type K The fibers in the dense region have a form in which the fibers are oriented in a non-linear manner in the parallel cross section.
The method for producing a foamed resin molded product according to any one of claims 1 to 3 , wherein the fibers in the sparse region have a form in which the fibers are linearly oriented in the parallel cross section. When the length of the foamed resin molded product in the core back direction is T (mm),
The foamed resin molded product has the dense region at one of the positions T / 4 or T / 2 from the end face in the core back direction and the sparse region at the other in the parallel cross section. The method for producing a foamed resin molded product according to any one of 4 to 4. When the void lengths at the T / 4 position and the T / 2 position are LT _{/ 4} (μm) and LT _{/ 2} (μm), respectively.
The method for producing a foamed resin molded product according to any one of claims 1 to 5 _{, wherein LT / 4} / LT _{/ 2} is 1.5 or more or 0.7 or less. The dense region has a void length of 20 μm or less in the parallel cross section.
The method for producing a foamed resin molded product according to any one of claims 1 to 6 , wherein the sparse region has a void length of more than 20 μm in the parallel cross section. The dense region has an average diameter of 10 μm or less and a fiber number of ^{40 fibers / 100 μm 2 or more in a cross section perpendicular to the fiber orientation direction.}
The method for producing a foamed resin molded product according to any one of claims 1 to 7 , wherein the sparse region has an average diameter of 8 μm or less and a number of fibers of ^{20 fibers / 100 μm 2 or more in a cross section perpendicular to the fiber orientation direction.} Claims 1 to 8 wherein the thermoplastic resin composition has a storage elastic modulus ^{of 1 × 10 3 to} 5 × 10 ⁶ Pa at a crystallization temperature Tccs at a cooling rate of 10 ° C./min of the thermoplastic resin composition. The method for producing a foamed resin molded product according to any one of. The method for producing a foamed resin molded product according to any one of claims 1 to 9 , wherein the thermoplastic resin composition further contains a crystal nucleating agent. Claimed that the thermoplastic resin is a polymer having a crystallization temperature of Tcps at a cooling rate of 10 ° C./min at 90 to 210 ° C. and a storage elastic modulus ^{of 1 × 10 3} to 1 × 10 ^{6 Pa at Tcps.} Item 8. The method for producing a foamed resin molded product according to any one of Items 1 to 10. The foamed resin molding according to any one of claims 1 to 11 , wherein the thermoplastic resin composition is injected into the mold, the thermoplastic resin composition is held in the mold, and the movable core back is started. How to manufacture the product. The method for producing a foamed resin molded product according to any one of claims 1 to 12 , wherein the cell diameter in the thermoplastic resin composition in the mold at the start of core back is 30 μm or less. The method for producing a foamed resin molded product according to any one of claims 1 to 13 , wherein foaming is performed at a foaming ratio of 3 to 8 times.

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