Method for manufacturing foam molding

Abstract

To provide a method for manufacturing a new foam molding, capable of enhancing shock resistance.SOLUTION: A method for manufacturing a foam molding comprises the steps of: supplying a molten material at least including a fibrous material using polyolefin and cellulose as a main component and having an aspect ratio of 10 or more and 1000 or less and a physical foaming agent into a die; and forming the molten material in the die to obtain a foaming molding. The physical foaming agent is a liquid in the environment of 25°C and the atmospheric pressure and is gas in the environment of 100°C and the atmospheric pressure; and the addition amount of the fibrous material to the mass of all the components of a solid in the molten material in the environment of 25°C and the atmospheric pressure is in a range of 0.1 mass% or more and less than 15 mass%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a foamed molded article. [Background technology]

[0002] Foam molded products of thermoplastic resins are generally lightweight and have excellent thermal insulation, insulation, sound absorption, shock absorption, etc., and are therefore used in a variety of products, including building materials, packaging materials, and acoustics. Although foam molded products are inferior to unfoamed molded products made from thermoplastic resins in mechanical properties such as elastic modulus and strength, and thermal properties such as heat distortion temperature, the introduction of air bubbles allows for a reduction in the amount of resin used compared to unfoamed products, and so demand is expected to expand further in the future from the perspective of resource conservation.

[0003] Resin foaming methods can be broadly divided into two categories: chemical foaming and physical foaming. Chemical foaming is a molding method using organic or inorganic chemical foaming agents, which decompose or react when heated, generating gas. This method has the advantage of keeping initial investment low and easily increasing the amount of foaming gas, but it has some issues, such as the need for crosslinking depending on the foaming material, the fact that residues are left behind after the foaming agent decomposes or reacts, making it unsuitable for recycling resins, and the difficulty of controlling foaming.

[0004] Physical foaming is a method of generating bubbles by dissolving liquefied gas or supercritical fluid in plastic under high pressure and temperature, and then reducing the solubility by lowering the pressure or heating.This method is becoming widely used today.

[0005] In this context, as disclosed in Patent Document 1, efforts have recently been made to use, as a foaming agent, a material that is liquid at 25°C and atmospheric pressure, such as water or alcohol, in physical foaming. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2015 / 174255 publication [Patent Document 2] WO2017 / 119228 publication [Patent Document 3] WO2016 / 072112 publication Summary of the Invention [Problem to be solved by the invention]

[0007] However, hydrophobic plastics are difficult to dissolve in water or alcohol, and tend to separate even in a molten state. This can lead to larger foam cells and reduced mechanical strength. For these reasons, there is room for improvement in the mechanical strength of propylene-based foamed molded articles foamed with water or alcohol.

[0008] The present invention was devised to solve these problems, and aims to provide a method for producing foamed molded articles that can increase mechanical strength while using a blowing agent that is liquid at 25°C and atmospheric pressure. [Means for solving the problem]

[0009] [1] A step of supplying a molten material containing at least a polyolefin, a fibrous material mainly composed of cellulose and having an aspect ratio of 10 to 1000, and a physical foaming agent into a mold; and foaming the molten material in the mold to obtain a foamed molded article, the physical foaming agent is a liquid at 25°C under atmospheric pressure and a gas at 100°C under atmospheric pressure; A method for producing a foamed molded product, wherein the amount of the fibrous material added is in the range of 0.1 mass % or more and less than 15 mass % relative to the mass of all components in the molten material that are solid in an environment of 25°C and atmospheric pressure.

[0010] [2] The method according to [1], wherein the physical foaming agent is water and / or alcohol.

[0011] [3] The method according to [1], wherein the physical foaming agent is water.

[0012] [4] The method according to any one of [1] to [3], wherein the molten material further contains a carboxylic acid anhydride-modified polypropylene.

[0013] [5] The method according to any one of [1] to [4], wherein the polyolefin comprises a polyolefin having a branched structure having 20 or more carbon atoms.

[0014] [6] The method according to any one of [1] to [5], wherein in the step of supplying the molten material into the mold, a decorative sheet that comes into contact with the molten material is further placed in the mold.

[0015] [7] The method according to any one of [1] to [6], wherein the step of foaming the molten material in the mold is a step of expanding the cavity volume in the mold. [Effects of the Invention]

[0016] According to the present invention, a novel foam molded article capable of increasing impact resistance is provided. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of an injection molding apparatus used in a method for producing a foamed molded article according to one embodiment. [Figure 2] FIG. 2 is a cross-sectional view illustrating a foam molded article according to one embodiment. [Figure 3] FIG. 3 is a cross-sectional view illustrating a foam decoration according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] (Method of manufacturing foam molded article) This method includes the steps of supplying a molten material containing at least a polyolefin, a fibrous material containing cellulose as a main component and having an aspect ratio of 10 to 1000, and a physical foaming agent into a mold; and a step of foaming the molten material in the mold to obtain a foamed molded article. The physical blowing agent is a liquid at 25°C under atmospheric pressure and a gas at 100°C under atmospheric pressure. The amount of the fibrous material added is in the range of 0.1% by mass or more and less than 15% by mass relative to the mass of all components that are solid in a 25°C atmospheric pressure environment in the molten material.

[0019] (Polyolefin) Examples of polyolefins include linear polyolefins such as polyethylene, polypropylene, polybutene, copolymers of ethylene and one or more α-olefins, copolymers of two or more α-olefins, and the like, and may also be a mixture of any two or more of these. Polyolefins are thermoplastic and not crosslinked.

[0020] Examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene.

[0021] The polyolefin may be a so-called linear polyolefin having no branched chains with 20 or more carbon atoms, a long-chain branched polyolefin having branched chains with 20 or more carbon atoms, or a mixture containing these in any ratio. The so-called linear polyolefin having no branched chains with 20 or more carbon atoms may be a mixture of polypropylene and an ethylene-α-olefin copolymer. The polyolefin may contain 10% by mass or more of linear polyolefin, 20% by mass or more, 40% by mass or more, 50% by mass or more, 70% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass. It is particularly preferable that the content be 70% or less. It is even more preferable that the content be 50% or less.

[0022] The polyolefin may include a long-chain branched polyolefin having a branched chain with 20 or more carbon atoms. The upper limit of the number of carbon atoms in the branched chain may be 100,000 or less, 1,000 or less, or 100 or less. Examples of long-chain branched polyolefins include low-density polyethylene (LDPE), long-chain branched polypropylene, and polylactic acid. Examples of polyolefins having a branched chain with 20 or more carbon atoms include low-density polyethylene produced by radical polymerization, polyolefins graft-polymerized with electron beams, and high-melt tension polypropylene polymerized with a metallocene catalyst. From the viewpoints of compatibility with polypropylene resins and recyclability, high-melt tension polypropylene polymerized with a metallocene catalyst is more preferred. When the long-chain branched polyolefin is contained, the branched long chains become entangled, which increases the melt tension and makes it possible to suppress the bursting and coalescence of cells during foaming.

[0023] The proportion of long-chain branched polyolefin in the polyolefin may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 50% by mass or more, 80% by mass or more, or even 100% by mass. It is particularly preferably 30% by mass or more, and more preferably 50% by mass or more. The polyolefin may contain linear polyolefin and not contain long-chain branched polyolefin.

[0024] In this specification, the term "polyolefin" does not include the carboxylic acid anhydride-modified polyolefin described below.

[0025] The amount of polyolefin may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, based on the mass of all components in the molten material that are solid in an atmospheric pressure environment at 25°C.

[0026] (Carboxylic acid anhydride modified polyolefin) Preferably, the molten material further contains a carboxylic acid anhydride modified polyolefin. An example of a carboxylic acid anhydride is maleic anhydride. An example of a carboxylic acid anhydride-modified polyolefin is maleic anhydride-modified polypropylene.

[0027] When the molten material, i.e., the foamed molded product, contains a carboxylic acid anhydride-modified polyolefin, the compatibility between the polyolefin and the fibrous material whose main component is cellulose is improved, making it easier for the fibrous material to disperse and for the air bubbles (cells) to be made finer.

[0028] The amount of carboxylic acid anhydride-modified polyolefin per 100 parts by mass of polyolefin may be 0.1 parts by mass or more, 0.15 parts by mass or more, 0.2 parts by mass or more, 0.25 parts by mass or more, 0.5 parts by mass or more, 10 parts by mass or less, 7.5 parts by mass or less, or 5 parts by mass or less. A range of 1 part by mass or more to 5 parts by mass or less is particularly preferred. A range of 1.1 parts by mass or more to 3 parts by mass or less is even more preferred.

[0029] (fibrous materials) The melt material contains a fibrous material whose main component is cellulose and whose aspect ratio is 10 or more and 1,000 or less.

[0030] Examples of fibrous materials whose main component is cellulose include plant fibers, recycled fibers, acetate-based fibers (diacetate and triacetate), pulp fibers, and cellulose fibers.

[0031] Examples of plant fibers include cotton and hemp.

[0032] Examples of acetate-based fibers include acetate fibers, diacetate fibers, and triacetate fibers.

[0033] Examples of regenerated fibers include rayon and cupra.

[0034] Pulp fibers are fibers obtained by removing lignin and hemicellulose from plant fibers.

[0035] The cellulose fibers are fibers obtained by defibrating pulp fibers. The diameter of the cellulose fibers may be 1 μm or more, or may be less than 1 μm. The diameter of the cellulose fibers may be 3 nm to 10 μm.

[0036] The cellulose in the fibrous material may be modified with a hydrophobic functional group such as fluorene.

[0037] Fibers containing cellulose as a main component, such as cellulose fibers, may contain at least one of hemicellulose and lignin in addition to cellulose. Cellulose may account for 50% by mass or more, or 70% by mass or more, of the fibrous material.

[0038] The average aspect ratio of the fibrous material containing cellulose as a main component is 10 to 1000. The average aspect ratio may be 30 or more, 50 or more, 100 or more, 150 or more, or 200 or more. The average aspect ratio may be 950 or less. If the aspect ratio is too small, the effect of increasing the viscosity of the molten material is less pronounced, and if the aspect ratio is too large, the viscosity of the molten material tends to become too high, making molding difficult.

[0039] The average aspect ratio of a fibrous material whose main component is cellulose is defined as (average fiber length / average fiber diameter). Specifically, the fiber diameter and fiber length of any 20 fibers in a transmission electron microscope image of a foamed molded product are obtained, and the average aspect ratio can be calculated by dividing the average fiber length by the average fiber diameter.

[0040] The diameter of the fibrous material may be 0.003 to 10 μm.

[0041] The amount of the fibrous material containing cellulose as a main component is 0.1 to 15% by mass relative to the mass of all components in the molten material that are solid at 25°C under atmospheric pressure. In the foamed molded product, the amount of the fibrous material containing cellulose as a main component may be 0.2% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 2.0% by mass or more, 3.0% by mass or more, 13% by mass or less, 10% by mass or less, or 9.0% by mass.

[0042] By using a cellulose-based fiber material in an amount of 0.1 parts by mass or more, the effect of improving mechanical properties is easily realized, while by using a cellulose-based fiber material in an amount of 15 parts by mass or less, it is possible to suppress the aggregation of the fiber material while improving mechanical properties.

[0043] (physical foaming agent) The molten material contains a physical foaming agent that is liquid at 25°C under atmospheric pressure and gaseous at 100°C under atmospheric pressure. Examples of such physical foaming agents include water and / or alcohol. Examples of alcohol include monohydric alcohols such as ethanol, methanol, and isopropyl alcohol, dihydric alcohols such as ethylene glycol, and trihydric or higher alcohols such as glycerin. Other examples of physical foaming agents include ethers, esters, and ketones.

[0044] The physical blowing agent may be a mixture of water and an alcohol such as ethanol, which is a liquid at 25°C under atmospheric pressure and a gas at 100°C under atmospheric pressure.

[0045] The amount of such physical foaming agent in the molten material can be adjusted appropriately depending on the expansion ratio, etc. The amount of physical foaming agent may be 0.1 to 40 parts by mass, 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 10 parts by mass or more, 30 parts by mass or less, or 20 parts by mass or less, relative to 100 parts by mass of all components in the molten material that are solid at 25°C under atmospheric pressure. An amount of 0.1 parts by mass or more is preferred because foaming proceeds sufficiently. An amount of 40 parts by mass or less is preferred because it can prevent the internal pressure from becoming too high during foaming, causing foam cells to burst or preventing some of the foam cells from expanding outward like a balloon (puncture).

[0046] (coloring agent) The molten material may contain a colorant. Examples of colorants include dyes and pigments. Examples of pigments include inorganic pigments such as metal oxides, such as titanium oxide and iron oxide, and composite oxides, such as iron-zinc oxide, chromium-antimony oxide, and iron-aluminum oxide.

[0047] The color of the foamed molded article can be appropriately selected depending on the type of colorant.

[0048] The amount of colorant may be 0.1% by mass or more and 30% by mass or less relative to the mass of all components in the molten material that are solid in an environment of 25° C. and atmospheric pressure.

[0049] (Other ingredients) The molten material may contain other components, such as elastomers, ultraviolet absorbers, light stabilizers, inorganic materials such as calcium carbonate, mica, and talc, flame retardants such as metal hydrates, pigments, foam control agents, lignin, hemicellulose, antioxidants, nucleating agents, antistatic agents, processing stabilizers, and slip agents.

[0050] (Preparation of molten material) The molten material can be obtained by melt-kneading a resin such as polyolefin, a fibrous material, and a physical foaming agent.

[0051] For example, the above-mentioned molten material can be obtained by supplying polyolefin pellets, pellets containing a fibrous material, and a physical foaming agent to a plasticizer such as a single-screw extruder having a heating barrel and a screw, and melt-kneading them.

[0052] The resin temperature after heating and melting in the heating cylinder should be equal to or higher than the crystalline melting temperature, which is usually equal to or higher than the temperature at which polyolefin melts.Since cellulose begins to decompose at temperatures above 250°C, the temperature is specifically 100 to 250°C.

[0053] The back pressure during plasticization is preferably set so as to enhance the dispersibility of the gas or liquid of the physical foaming agent in the molten material, and specifically can be set to 5 to 30 MPa.

[0054] The physical foaming agent may be supplied together with the resin from a hopper provided in the heating barrel, or, as will be described later, may be supplied separately from the resin from an inlet for the physical foaming agent provided in the heating barrel between the hopper and the outlet nozzle. When the physical foaming agent is supplied together with the resin from the hopper, it is also preferable to provide a lid on the hopper or the like and open and close it for each shot in order to prevent the physical foaming agent from escaping from the hopper.

[0055] Furthermore, since the back pressure during plasticization is high, it is preferable to provide a shut-off nozzle at the tip exit of the heating barrel to prevent resin leakage such as dripping.

[0056] (supply to mold) The molding die is not particularly limited as long as it has a cavity into which the molten material is supplied, and may be a Cerca type die used in extrusion molding. Also, so-called insert molding may be performed in which another member such as a decorative sheet is placed in the mold.

[0057] As will be described later, the mold may be a so-called core-back mold, which allows the cavity volume within the mold to be expanded after the molten material is supplied.

[0058] The molten material can be supplied to the mold by driving the screw of a single-screw plasticizer, for example.

[0059] (Foaming process) After supplying the molten material into the cavity of the mold, the resin is foamed by a known method. For example, in the case of a core-back type foaming method, the cavity volume in the mold is expanded after supplying the molten resin, thereby reducing the pressure and foaming the resin.

[0060] Furthermore, by short-shotting the molten material into the cavity of the mold, the molten material can be foamed within the cavity.

[0061] In the case of a Cerca-type mold, molten resin can be extruded from a die in a hollow shape, and the surface of the resin extruded by the mold can be cooled while foaming toward the center of the resin.

[0062] If other members such as a decorative sheet are placed inside the mold, the foam material will come into contact with the back surface of the decorative material.

[0063] (Example of injection molding equipment) An example of a foam injection molding apparatus suitable for carrying out the method for producing a molded article according to the present invention is shown in FIG. The molding device 1 has a uniaxial plasticizer 10 having a heating barrel (cylinder) 11 and a screw 12, and a hopper 13 for feeding raw materials such as resin and filler is provided near the rear end (right side in Figure 1) of the uniaxial plasticizer 10.

[0064] A conical head 15 is provided at the tip of the screw 12, and the tip of the heating barrel 11 is narrowed to a conical shape corresponding to the shape of the head 15, and is provided with an outlet nozzle 16 at its tip. An inlet 17a for supplying a physical foaming agent is provided in the heating barrel 11 between the hopper 13 and the outlet nozzle 16, and a tank 40 for storing a physical foaming agent such as water or alcohol is connected to the inlet 17a via a metering pump 17.

[0065] A mold 20 is disposed at the tip side of the heating barrel 11. The mold 20 has a fixed mold 21 and a movable mold 22 that is movable relative to the fixed mold 21. A cavity 23 that will have the shape of the molded product when the molds are clamped is formed between the fixed mold 21 and the movable mold 22 of the mold 20. The thickness of the cavity 23 can be expanded by a drive mechanism (not shown) for driving the movable mold 22 (not shown). An outlet nozzle 16 can be connected to the fixed mold 21, and a passage (hot runner) 21a that communicates with the cavity 23 from the connection portion of the outlet nozzle 16 is formed.

[0066] Another molding machine suitable for producing the molten resin according to this embodiment is disclosed in, for example, WO2015 / 174255.

[0067] (Shape of foam molded product) The shape of the foamed molded article is not particularly limited, and may be a plate, block, sheet, sphere, cone, polygonal pyramid, cylinder, polygonal column, or irregular shape. It may also be a partially cut-out shape of any of these, or a combination thereof. Furthermore, the surface layer may be embossed for decorative relief.

[0068] When the foamed molded article is in the form of a plate, the thickness may be 0.5 mm or more, 1.0 mm or more, 15.0 mm or less, or 10.0 mm or less. If the thickness is less than 0.5 mm, the surface area relative to the volume is too large, which makes gas leakage more likely. If the thickness is 0.5 mm or more, this gas leakage can be prevented, which is preferable.

[0069] As shown in Fig. 2, the foamed molded product 100 has a large number of cells 120. The foamed molded product 100 may have either an open-cell structure or a closed-cell structure, but a closed-cell structure is preferable from the viewpoint of mechanical properties.

[0070] The expansion ratio of the foamed molded article may be 0.1 to 10 times.

[0071] The average diameter of the cells in the foamed molded article may be 0.01 mm to 10.0 mm or less. When the average diameter of the foamed cells is 0.01 mm or more, the foamed cells grow sufficiently, which is preferable because the expansion ratio increases. When the foamed cells are 10 mm or less, it is preferable because it is possible to make the mechanical strength uniform. It is also preferable because it is possible to prevent the problem of reduced shock absorption performance. It is also preferable because it is possible to make the appearance uniform. However, the average diameter of the cells must be equal to or less than the thickness of the molded article.

[0072] The diameter of each bubble (cell) is the average of the long and short diameters of the cell, and the average diameter of the bubble (cell) is defined as the arithmetic mean value of the diameters of 10 cells randomly extracted from a cross-sectional image obtained by a scanning electron microscope or the like.

[0073] (Structure of decorative foam molding) An example of a decorated foam molded article 300 of the present invention will be described with reference to FIG.

[0074] As shown in FIG. 3, the decorated foam molded body 300 includes at least the foam molded body 100 and a decorative layer 200 provided on the surface of the foam molded body 100 .

[0075] The decorative layer 200 may be a separately formed decorative sheet, in which case the decorative sheet may be an adhesive layer laminated to the foam molded body 100 via an intermediate layer 150, and the decorative sheet may be in direct contact with the foam molded body 100 by insert molding.

[0076] The decorative layer 200 may be a dried / cured product of paint applied to the surface of the foam molded body 100. The paint can be applied using a known printing method. When the decorative layer is mainly composed of polypropylene, the recyclability is improved by making it a mono-material. Furthermore, when the decorative layer is a cross-linked layer, the impact resistance is further improved. Furthermore, the design properties can be improved by introducing a color pigment into the cross-linked layer.

[0077] The decorative layer can have any pattern. Addition of the decorative layer can further improve mechanical properties such as impact resistance.

[0078] The decorative layer may contain a resin and a colorant such as a pigment, etc. The amount of the colorant in the decorative layer may be 0.1% by mass or more and 30% by mass or less.

[0079] An intermediate layer 150 such as a primer layer may be present between the decorative layer 200 and the foam molded body 100 .

[0080] (Mechanism of action) According to this embodiment, the addition of a cellulose-based fibrous material with an aspect ratio of 10 to 1000 increases the viscosity of the molten material, enabling the foam cells to be refined without the use of a crosslinking agent, resulting in improved impact resistance. The resin-reinforcing effect of the fibrous material itself also contributes to improved impact resistance. Furthermore, by using a physical blowing agent, such as water or alcohol, which is liquid at 25°C and atmospheric pressure and gaseous at 100°C, foams can be obtained more cheaply than chemical blowing agents and with lower capital investment than physical blowing agents, such as CO2, which are gaseous at 25°C and atmospheric pressure. The use of polyolefins also eliminates concerns about hydrolysis, which can occur when using water.

[0081] In particular, when the physical blowing agent is water, the compatibility with the molten polyolefin is lower than that of commonly used organic solvents such as ethyl acetate, methyl ethyl ketone, methanol, and ethanol, and therefore the generated gas is thought to contribute efficiently to foaming.

[0082] In addition, when a carboxylic acid anhydride-modified polypropylene such as maleic acid-modified polypropylene is used, it acts as a compatibilizer between the polyolefin and the cellulose-based fibrous material, causing the cellulose-based fibrous material to be finely dispersed in the polyolefin, thereby maximizing the effect of the fibrous material, which is thought to result in finer foam cells and improved impact resistance.

[0083] Furthermore, when polyolefins with a branched structure containing 20 or more carbon atoms are added, the entanglement of molecules in the molten state improves the melt viscosity, which has the effect of making the foam cells finer, and is thought to result in improved impact resistance.

[0084] Furthermore, when the foam laminate is laminated with a decorative layer, the mechanical strength is further improved.

[0085] Furthermore, by laminating a decorative sheet whose main component is polypropylene onto the surface, recycling performance is improved by making it a mono-material.

[0086] Furthermore, if foam molding and sheet lamination are carried out simultaneously in a mold, the manufacturing process is simplified and economic rationality is enhanced.

[0087] Furthermore, by providing a crosslinked layer on the surface, impact resistance can be further improved, and by incorporating color pigments into the crosslinked layer, the design properties can also be improved.

[0088] Furthermore, with the core-back method, the foam cells are oriented in the thickness direction, which is thought to improve compression resistance, as the cellulose-based fibrous material is also oriented in the thickness direction. Furthermore, since resins containing cellulose-based fibrous materials have thixotropy, they have increased fluidity during injection molding, which is thought to reduce molding defects. [Example]

[0089] (Examples 1 to 13, Comparative Examples 1 to 4) The materials (1) to (6) listed in Tables 1 and 2 were dry-blended in the mass ratios listed, and the mixture was supplied in a fixed amount to the resin feeding hopper of a core-back driven injection molding machine. At the same time, water or methanol was added dropwise as a blowing agent to the resin feeding hopper using a fixed amount dripping device so that the mass ratios shown in Table 1 were obtained.

[0090] (1) CNF composite fiber Ellex-R67 is a polypropylene resin (manufactured by Daio Paper Co., Ltd.) containing 67% by mass of fiber whose main component is cellulose. The fiber diameter was in the range of 0.5 to 6.0 μm. (2) Maleic acid modified PP Umex 1010 is a maleic anhydride modified polypropylene resin (manufactured by Sanyo Chemical Industry Co., Ltd.). (3) Homo PP E2000GV is a homo polypropylene (manufactured by Prime Polymer). (4) LDPE Novatec PE LC600A is a long-chain branched high-pressure low-density polyethylene (manufactured by Mitsubishi Chemical Corporation). (5) HMS-PP Waymax MFX3 is a long-chain branched polypropylene (Japan Polypropylene Corporation). (6) Olefin copolymer Toughmer DF605 is an ethylene-α-olefin copolymer (manufactured by Mitsui Chemicals, Inc.). In Tables 1 and 2, (1) to (6) indicate the mass percentage (%) of all solid components at 25°C and atmospheric pressure, the foaming agent is expressed in parts by mass per 100 parts by mass of solid components at 25°C and atmospheric pressure, and the amount of cellulose-based fiber added is expressed in parts by mass (%) of all solid components at 25°C and atmospheric pressure.

[0091] The plasticization of each resin material and the liquid blowing agent was carried out in a single-screw plasticizer equipped with a single screw and a heating barrel, with the interior of the machine pressurized and set at a temperature of 190°C. The blowing agent, such as water or alcohol, was heated in the heating barrel and dispersed into the resin. Meanwhile, a 100mm x 100mm x 2mm (thickness) mold was prepared as the molding die. The mold was driven in conjunction with the core back drive of the injection molding machine, moving in the thickness direction by 2mm (4mm thick molded product, equivalent to double foaming), 4mm (6mm thick molded product, equivalent to triple foaming), and 6mm (8mm thick molded product, equivalent to quadruple foaming) to mold the product. The filling speed was 30mm per second, the injection time was 2.2 seconds, the holding pressure was 15MPa, the time until the mold opened was 10 seconds, and the time until the mold was released was 0.5 seconds. The aspect ratio of the cellulose-based fibers in the resin material was adjusted by increasing the screw rotation speed and performing kneading multiple times.

[0092] Example 14 Furthermore, in Example 14, the surface of the foamed molded body was subjected to corona treatment, and then a polypropylene-based decorative sheet (101 Eco Sheet: manufactured by TOPPAN Corporation) was attached to it using an adhesive (Bond GP100), thereby producing the foamed body of Example 14.

[0093] Example 15 Furthermore, in Example 15, the surface of the foamed molded body was similarly subjected to corona treatment, then sprayed with PP primer spray (manufactured by Rock Paint, product number: 062-4005), and then painted using acrylic lacquer spray ECO (manufactured by Rock Paint), to produce the foamed body of Example 15.

[0094] Example 16 A mold measuring 100 mm x 100 mm x 4 mm (thickness) was prepared as the molding die, and the foam of Example 16 was produced using the same method as in Examples 1 to 15, except that the resin was foamed and filled into the mold using a short shot without core backing.

[0095] Example 17 Using a short-axis profile extruder, a Cerca foaming mold with an opening width of 100 mm and a thickness of 4 mm was attached to the tip of the die to produce a slab foam equivalent to double the foaming density in terms of specific gravity.

[0096] (evaluation) The prototype foams of the Examples and Comparative Examples were evaluated for surface appearance and impact resistance. Impact resistance was evaluated by dropping a 500g iron ball onto the foam from a height of 500mm, and measuring the amount of dent on the surface. Measurements were performed five times, and the average of three values ​​excluding the maximum and minimum values ​​was recorded as the amount of dent. The test results are shown in Table 1.

[0097] (shock resistance) A φ12.7mm die is attached to a DuPont testing machine (manufactured by Tester Sangyo). The sample is placed under the die, and a 500g weight (iron ball) is dropped from a height of 500mm. The test is carried out with N=5, with the measurement position of the sample being shifted. The amount of dent in the sample is measured using a depth gauge (manufactured by Mitutoyo), and the average value is used to evaluate.

[0098] The conditions and results are shown in Tables 1 and 2.

[0099] [Table 1]

[0100] [Table 2]

[0101] In Examples 1 to 17, the impact resistance could be increased. [Explanation of symbols]

[0102] 100...foam molded body, 200...decorative layer, 300...decorative foam molded body.

Claims

1. supplying a molten material containing at least a polyolefin, a fibrous material containing cellulose as a main component and having an aspect ratio of 10 to 1000, and a physical foaming agent into a mold; and foaming the molten material in the mold to obtain a foamed molded article, the physical foaming agent is a liquid at 25°C under atmospheric pressure and a gas at 100°C under atmospheric pressure; A method for producing a foamed molded body, wherein the amount of the fibrous material added is in the range of 0.1 mass % or more and less than 15 mass % relative to the mass of all components in the molten material that are solid in a 25°C atmospheric pressure environment.

2. The method of claim 1 , wherein the physical blowing agent is water and / or alcohol.

3. The method of claim 1 , wherein the physical blowing agent is water.

4. The method of claim 1 or 2, wherein the molten material further comprises a carboxylic acid anhydride modified polypropylene.

5. The method according to claim 1 or 2, wherein the polyolefin comprises a polyolefin having a branched structure having 20 or more carbon atoms.

6. The method according to claim 1 or 2, wherein in the step of supplying the molten material into the mold, a decorative sheet is further placed in the mold so as to come into contact with the molten material.

7. The method according to claim 1 or 2, wherein the step of foaming the molten material in the mold is a step of expanding a cavity volume in the mold.

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