Molding resin material and its manufacturing method

Abstract

To provide a resin material for molding which is formed by uniformly mixing a woody biomass roasted material and a thermoplastic resin, has such has viscosity as to prevent cutting and breakage in injection molding, and facilitates molding.SOLUTION: A resin material for molding contains 40-90 mass% of a woody biomass roasted material having an average particle diameter of 100 μm or less, and further contains a thermoplastic resin and acid-modified polyolefin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a molding resin material containing woody biomass roasted material, a thermoplastic resin typified by polypropylene, polyethylene, polylactic acid, etc., and an acid-modified polyolefin, and a method for producing the same. [Background technology]

[0002] Biomass materials are attracting attention as industrial resources. Biomass materials refer to materials derived from living organisms such as plants. Because biomass materials are organic, they emit carbon dioxide when burned. However, the carbon contained in them comes from carbon dioxide absorbed from the atmosphere by photosynthesis during the growth process of the biomass, so it is safe to say that the use of biomass materials does not increase the amount of carbon dioxide in the atmosphere overall. This property is called carbon neutral.

[0003] Against the backdrop of global environmental issues such as global warming, there is an urgent need to conserve resources, recycle materials to turn waste into raw materials, and promote environmental circulation cycles such as those typified by biodegradable plastics.In Japan, the revised Recycling Law and the Green Purchasing Law have been established, and there is a growing need for products that comply with these laws.

[0004] In this context, incorporating biomass materials into resin molded products, which are widely used in everything from automotive parts to everyday items, would promote the implementation of the carbon-neutral concept. For example, Patent Document 1 describes a composite material containing carboxymethylated cellulose nanofibers, a polymer compound having a primary amino group, an acid-modified polyolefin, and a polyolefin. Patent Document 2 describes a cellulose composite material containing wood pulp and a polymer matrix. Patent Document 3 describes a method for producing a wood-flour-containing resin injection-molded product by mixing wood flour and random polypropylene resin and using an injection molding machine. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. WO2014 / 087767 [Patent Document 2] Special Publication No. 2019-512591 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-138337 Summary of the Invention [Problem to be solved by the invention]

[0006] However, simply mixing "woody biomass" and "polypropylene" and then heating and melting them to form a mold involves problems such as the inability to mix the woody biomass and polypropylene uniformly due to the hydrophilic nature of the woody biomass, the resin body being cut into small pieces at the outlet of the device that injects the mixture of woody biomass and polypropylene, and the surface of the resulting molded article not being smooth.

[0007] For example, Patent Document 1 describes the use of carboxymethylated cellulose nanofibers, but in order to carboxymethylate the cellulose and further increase the uniform dispersion with the polyolefin resin, it is necessary to add a polymer compound having a primary amino group and an acid-modified polyolefin, which increases costs.

[0008] Therefore, an object of the present invention is to provide a molding resin material containing woody biomass at low cost, in which the woody biomass and thermoplastic resin are uniformly mixed and which is less likely to cut or crack during molding, such as injection. [Means for solving the problem]

[0009] The present inventors have discovered that a molding resin material with excellent moldability can be obtained by mixing pulverized woody biomass roasted material with a thermoplastic resin such as polypropylene, polyethylene, or polylactic acid, and further with an acid-modified polyolefin, and then heating and kneading the mixture, and have thus completed the present invention.

[0010] The present invention includes, but is not limited to, the following: (1) A molding resin material containing 40 to 90 mass % of pulverized woody biomass roasted material having an average particle size of 100 μm or less, and further containing a thermoplastic resin and an acid-modified polyolefin. (2) The molding resin material according to (1), wherein the acid-modified polyolefin has a weight-average molecular weight of 9,000 to 45,000. (3) The molding resin material according to (1) or (2), wherein the acid-modified polyolefin has an acid value of 26 to 70. (4) The molding resin material according to any one of (1) to (3), wherein the content of the acid-modified polyolefin in the molding resin material is 0.1 to 10% by mass. (5) The molding resin material according to any one of (1) to (4), which contains, as the thermoplastic elastomer, any one of a styrene-butadiene block copolymer, an ethylene-octene copolymer, and a propylene-ethylene copolymer. (6) The molding resin material according to any one of (1) to (5), wherein the thermoplastic resin contains a polyolefin-based resin. (7) The molding resin material according to any one of (1) to (6), wherein the thermoplastic resin comprises a polypropylene resin. (8) The molding resin material according to any one of (1) to (7), wherein the thermoplastic resin contains a biodegradable resin. (9) A method for producing a molding resin material, comprising a step of heating and kneading pulverized woody biomass roasted material, a thermoplastic resin, and a thermoplastic elastomer. (10) The method according to (9), wherein the molding material is continuously produced by processing with a twin-screw kneading extruder in the heating and kneading step. [Effects of the Invention]

[0011] According to the present invention, it is possible to stably produce a molding resin material having high viscosity and containing pulverized woody biomass roasted material, which does not break or crack during injection molding. Furthermore, by increasing the blending ratio of woody biomass roasted material, it is possible to obtain a molding resin material with excellent carbon neutrality. DETAILED DESCRIPTION OF THE INVENTION

[0012] The roasted product of the present invention can be obtained, for example, by roasting pulverized woody biomass having a size of 50 mm or less under conditions of an oxygen concentration of 10% or less and a material temperature of 240 to 350°C.

[0013] The present invention uses torrefied woody biomass. Both broad-leaved and coniferous trees can be used as raw wood for the woody biomass. Specific examples of broad-leaved trees include, but are not limited to, eucalyptus, rubber tree, beech, linden, birch, poplar, acacia, oak, sugar maple, Asian elm, paulownia, magnolia, willow, ash, phillyraeoides phillyraeoides, oak, sawtooth oak, horse chestnut, zelkova, beech, dogwood, and ash. Coniferous trees include cedar, spruce, larch, black pine, Abies sachalinensis, dwarf pine, yew, juniper, spruce, and yew. Examples include fir, Japanese holly, fir, Japanese sawara, Douglas fir, Asunaro, Japanese cypress, Japanese hemlock, Japanese hemlock, Japanese cypress, yew, Japanese yew, spruce, yellow cedar (Thujopsis thunbergii), Japanese cypress (Chamaecyparis obtusa), Douglas fir (Douglas fir), Sitka spruce (Picea abies), Radiata pine, Eastern spruce, Eastern white pine, Western larch, Western fir, Western hemlock, and tamarack.

[0014] Among these, wood of the genus Eucalyptus and rubber tree (Hevea brasiliensis) are preferred. Examples of Eucalyptus include Eucalyptus (hereinafter abbreviated as E.) calophylla, E. citriodora, E. diversicolor, E. globulus, E. grandis, E. urograndis, E. gummifera, E. marginata, E. nesophila, E. nitens, E. amygdalina, E. camaldulensis, E. delegatensis, E. gigantea, E. muelleriana, E. obliqua, E. regnans, E. sieberiana, E. viminalis, and E. marginata.

[0015] In the present invention, the form of the woody biomass used as the raw material is not limited, and for example, wood chips, bark, sawdust, sawdust, etc. can be suitably used. In a preferred embodiment, woody biomass having a size of 50 mm or less can be used as the raw material. For example, woody biomass can be adjusted to a size of 50 mm or less by pulverizing it, and it is preferable to use woody biomass pulverized to a size of 1 mm to 50 mm as the raw material. In the present invention, the size of the pulverized woody biomass is determined by sieving it according to the size of the circular holes in a sieving box. When pulverizing woody biomass, it is preferable to pulverize it using, for example, a hammer mill or a knife-cutting type biomass fuel chipper.

[0016] In the present invention, torrefaction of woody biomass is used. Torrefaction generally refers to a process of heating in a low-oxygen atmosphere at a temperature lower than that of so-called carbonization. While the temperature for normal wood carbonization is 400 to 700°C, in the present invention, torrefaction is carried out at 240 to 350°C. By torrefaction, a solid fuel with a higher energy density than the starting material is obtained.

[0017] The roasting conditions in the present invention are an oxygen concentration of 10% or less and a material temperature of 240 to 350°C. Here, the material temperature during roasting refers to the temperature of woody biomass near the outlet of the roasting treatment device. In the present invention, roasting is performed under conditions of an oxygen concentration of 10% or less. However, if the oxygen concentration exceeds 10%, the material yield and calorific yield may decrease. Furthermore, if the material temperature is less than 240°C, it is difficult to grind the roasted material to small particle sizes, and if it exceeds 350°C, the material yield and calorific yield decrease. The material temperature is preferably 240 to 330°C, and more preferably 250 to 320°C. Hemicellulose undergoes significant thermal decomposition around 270°C, while cellulose and lignin undergo significant thermal decomposition around 355°C and 365°C, respectively. Therefore, it is presumed that by setting the roasting temperature to 170 to 350°C, hemicellulose is preferentially thermally decomposed, making it possible to produce a molding resin material that achieves both material yield and pulverizability.

[0018] In the present invention, the roasting treatment apparatus is not particularly limited, but a rotary kiln and / or a vertical furnace is preferred. It is preferable to replace the atmosphere inside the apparatus with an inert gas such as nitrogen to adjust the oxygen concentration to 10% or less. The roasting treatment time is not particularly limited, but is preferably 1 to 180 minutes, more preferably 5 to 120 minutes, and even more preferably 10 to 60 minutes. When a continuous apparatus is used, the residence time in the roasting apparatus can be controlled.

[0019] In the present invention, an externally heated roasting device may be used as the device for performing the roasting treatment. For example, an externally heated rotary kiln has a structure in which a part or all of the inner kiln cylinder is covered with an outer kiln cylinder. Woody biomass is roasted in the inner kiln, and fuel is burned in the outer kiln to indirectly heat the woody biomass inside the inner kiln. The temperature inside the outer kiln cylinder can be 400 to 800°C, and preferably 450 to 750°C. If the temperature inside the outer kiln cylinder is less than 400°C, the pyrolysis of the woody biomass inside the inner kiln cylinder will be insufficient, and the crushability of the resulting solid fuel will be reduced. On the other hand, if the temperature exceeds 800°C, the temperature of the woody biomass inside the inner kiln cylinder will rise excessively, resulting in a decrease in the material yield and calorific yield of the resulting solid fuel.

[0020] The roasted product used in the present invention preferably has a material yield of 60 to 90% and a calorific yield of 70 to 95% relative to the woody biomass raw material. Furthermore, the Hardgrove Grindability Index (HGI) specified in JIS M 8801:2004, which is an index of grindability, is preferably 25 or more, more preferably 30 or more. The higher the HGI, the easier it is to grind. If the HGI is in the range of 25 to 70, it can be easily mixed with a thermoplastic resin and molded.

[0021] The roasted product used in the present invention may be formed into a molded product. That is, the starting material (roasted product) in the form of a pulverized woody biomass is molded into briquettes or pellets. Forming into a molded product makes it easier to handle and increases the density, thereby reducing transportation costs. The bulk density of the molded product after densification is preferably 500 kg / m or more, more preferably 600 kg / m or more. The bulk density can be measured according to JIS K 2151, Section 6, "Bulk Density Test Method."

[0022] In the present invention, the device for forming the roasted product into a molded product is not particularly limited, but for example, a briquette (manufactured by Kitagawa Iron Works), a ring die type pelletizer (manufactured by CPM), a flat die type pelletizer (manufactured by Kahl or Dalton), etc. are desirable.

[0023] In the present invention, when the roasted material is formed into a molded product, the moisture content of the roasted material is preferably 8 to 50%, and more preferably 10 to 30%. If the moisture content is less than 8%, clogging occurs inside the briquette or pelletizer, making it impossible to produce a stable molded product. If the moisture content exceeds 50%, molding becomes difficult and the product is discharged in a powder or paste form.

[0024] In the present invention, a binder may be added to the roasted product. The binder is not particularly limited, but suitable examples include organic polymers such as starch and lignin, inorganic polymers such as acrylic acid amide, and agricultural residues such as bran (residue generated during wheat flour production). From the viewpoint of efficiently utilizing woody biomass, it is desirable to add a small amount of binder, preferably 50 parts by mass or less, and more preferably 20 parts by mass or less, per 100 parts by mass of the roasted product. However, adding more than 50 parts by mass does not necessarily mean that high density is impossible.

[0025] In the present invention, the roasted material is preferably pulverized before being kneaded with the thermoplastic resin. The average particle size of the pulverized material must be 100 μm or less, and 50 μm or less is more preferable. If the average particle size of the pulverized roasted material is greater than 100 μm, it becomes difficult to uniformly mix it with the resin, and problems such as the resin being shredded at the outlet of the device that ejects the mixture of the pulverized material and the resin, or difficulty in conveying it to a cooling treatment device, may occur. The average particle size is the 50% volume average particle size (D50) measured by laser light scattering (laser diffraction) and can be measured using a laser diffraction / scattering particle size distribution analyzer (Malvern Instruments, Instrument Name: Mastersizer 2000) or the like.

[0026] The grinder used to grind the roasted material may be any device capable of grinding organic materials, including, but not limited to, a ball mill, rod mill, bead mill, conical mill, disk mill, edge mill, hammer mill, mortar, pellet mill, VSI mill, Willy mill, roller mill, jet mill, mass colloider, etc.

[0027] The molding resin material of the present invention can be obtained by heating and kneading the roasted product, a thermoplastic resin, and an acid-modified polyolefin. The blending ratio of the roasted product in the molding resin material is preferably high in order to achieve a high level of carbon neutrality, but considering the manufacturing and strength of the resulting resin material and molded article, it is preferably 40% by mass or more and 90% by mass or less, more preferably 50% by mass or more and 80% by mass or less.

[0028] The thermoplastic resin used in the present invention is preferably molded into granules for ease of handling, but may be in any form. Two or more types of thermoplastic resins may be used simultaneously.

[0029] Examples of thermoplastic resins include, but are not limited to, polyethylene and polypropylene, and any resin that can be plasticized and molded by heat can be used. Among these, polyethylene such as LDPE (low-density polyethylene) and polypropylene are preferred from the viewpoint of moldability.

[0030] In the present invention, a biodegradable resin may be used as the thermoplastic resin. Examples of biodegradable resins having thermoplastic properties include, but are not limited to, polylactic acid (PLA), polybutylene succinate, polyethylene succinate, polyglycol, polycaprolactone, and polyvinyl alcohol.

[0031] In the present invention, by adding an acid-modified polyolefin, a molding resin material with high uniformity and adhesiveness can be produced when the roasted product and thermoplastic resin are kneaded.

[0032] The weight-average molecular weight of the acid-modified polyolefin is preferably 9000 to 45000, more preferably 20000 to 35000. When the weight-average molecular weight is in the range of 9000 to 45000, the dispersibility of the roasted wood biomass material is improved, and the tensile strength is increased.

[0033] The acid value of the acid-modified polyolefin measured in accordance with JIS K 0070 is preferably 26 to 70, more preferably 40 to 60. When the acid value is in the range of 26 to 70, the dispersibility of the roasted wood biomass material improves and the tensile strength increases.

[0034] Known acid-modified polyolefins can be used, and examples thereof include, but are not limited to, maleic anhydride-modified polypropylene (UMEX 1001, 1010, manufactured by Sanyo Chemical Industries, Ltd.) and Modic (registered trademark) P908 (manufactured by Mitsubishi Chemical Industries, Ltd.).

[0035] The content of the acid-modified polyolefin in the molding resin material obtained by kneading is preferably 0.1 to 10 mass %, more preferably 0.3 to 5 mass %, and even more preferably 0.4 to 1 mass %.

[0036] In the present invention, by adding a thermoplastic elastomer, it is possible to stably produce a molding resin material with high viscosity that does not break or crack during injection molding, even when ground woody biomass roasted material is blended.

[0037] The thermoplastic elastomer used in the present invention may be a styrene-based thermoplastic elastomer. More specifically, it may be a block copolymer such as a styrene-butadiene-styrene (SBS) copolymer, a styrene-isoprene-styrene (SIS) copolymer, a styrene-ethylene-butylene-styrene (SEBS) copolymer, a styrene-ethylene-propylene-styrene (SEPS) copolymer, or a styrene-butadiene-butylene-styrene (SBBS) copolymer. These may be used alone or in combination of two or more.

[0038] The thermoplastic elastomer used in the present invention may be a polyolefin elastomer. More specifically, examples include ethylene-butene copolymer, EPR (ethylene-propylene copolymer), modified ethylene-butene copolymer, EEA (ethylene-ethyl acrylate copolymer), modified EEA, modified EPR, modified EPDM (ethylene-propylene-diene terpolymer), ionomer, α-olefin copolymer, modified IR (isoprene rubber), modified SEBS (styrene-ethylene-butylene-styrene copolymer), halogenated isobutylene-paramethylstyrene copolymer, ethylene-acrylic acid modified product, ethylene-vinyl acetate copolymer, and its acid-modified product, and mixtures containing these as the main components. These may be used alone or in combination of two or more.

[0039] Preferred thermoplastic elastomers for use in the present invention include styrene-butadiene block copolymers, ethylene-octene copolymers, and propylene-ethylene copolymers. Styrene-butadiene block copolymers are particularly preferred. The thermoplastic elastomers may be modified with maleic anhydride, fumaric anhydride, or the like. In the styrene-butadiene block copolymer, the styrene content is preferably 15 to 30% by mass.

[0040] The blending ratio of the thermoplastic elastomer is preferably 1 to 20% by mass, and more preferably 3 to 10% by mass.

[0041] A molded article can be obtained by heat-treating the molding resin material of the present invention. The temperature at which the molding resin material of the present invention is heat-treated (heated, melted, kneaded, etc.) is usually about 100 to 300°C, preferably about 110 to 250°C, and particularly preferably about 120 to 220°C. The molded article obtained by heat treatment can be molded into the desired shape using a conventionally known resin molding method.

[0042] In the method for producing a molding resin material of the present invention, the roasted product and the acid-modified polyolefin can be heated and kneaded using equipment commonly used in resin molding. For example, a common extruder or twin-screw kneading extruder can be used. The TEX series manufactured by The Japan Steel Works, Ltd. can be used as the twin-screw kneading extruder.

[0043] The molding resin material of the present invention can be used to produce various molded articles. For molding, a conventional method used for molding thermoplastic resins can be used, such as, but not limited to, injection molding, extrusion molding, blow molding, mold molding, hollow molding, and foam molding.

[0044] The molding resin material of the present invention or the molded article obtained by molding it may contain organic and / or inorganic substances other than the thermoplastic resin and the roasted product. Examples of other components include alkalis such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide; inorganic fillers such as clay, talc, calcium carbonate, myca, titanium dioxide, and zinc oxide; organic fillers such as carbon black, graphite, and glass flakes; dyes or pigments such as red iron oxide, azo pigments, and phthalocyanines; and property-modifying additives such as dispersants, lubricants, plasticizers, mold release agents, flame retardants, antioxidants (phenolic antioxidants, phosphorus antioxidants, and sulfur antioxidants), antistatic agents, light stabilizers, UV absorbers, metal deactivators, crystallization accelerators (nucleating agents), foaming agents, crosslinking agents, and antibacterial agents.

[0045] The molding resin material of the present invention can be molded for various purposes and can be used as a substitute for plastic products. Molded articles obtained from the molding resin material of the present invention can be widely used, including, for example, trays, automobile parts, automobile dashboards and other interiors, airplane luggage compartments, structural components for transportation equipment, housings for home appliances, electrical appliance components, cards, various containers such as toner containers, building materials, seedling pots, agricultural sheets, writing implements, wooden products, household appliances, straws, cups, toys, sporting goods, port components, building components, generator components, tools, fishing gear, packaging materials, 3D printer models, pallets, food containers, tableware, cutlery (spoons, forks, etc.), chopsticks, and various sheets. When these products are no longer needed, they are disposed of. However, even if they are incinerated and carbon dioxide is emitted, the torrefied woody biomass contained therein can be treated as not increasing the amount of carbon dioxide in the atmosphere. [Example]

[0046] The present invention will be described in more detail below with reference to experimental examples of the present invention, but the present invention is not limited to these experimental examples. Unless otherwise specified, parts and % represent parts by mass and % by mass, and numerical ranges are stated as including their endpoints.

[0047] [Example 1] Eucalyptus eurograndis wood chips were crushed using a disc chipper. After crushing, the crushed chips, sized 1–50 mm, were dried using a conveyor dryer (Alvan Blanch) at 70°C for 3 hours to adjust the moisture content to 10%. Next, roasting was carried out in a large rotary kiln-type carbonization furnace with an oxygen concentration of 1% or less and a material temperature of the ground chips in the carbonization furnace of 260°C for a residence time of 12 minutes to obtain a roasted woody biomass product. After cooling, the roasted product was pulverized in a LabMill (manufactured by Osaka Chemical Co., Ltd.) to an average particle size of 50 μm. Next, the ground roasted material, polypropylene (product name: J107G, manufactured by Prime Polymer, melt flow rate: 30 g / 10 min), and acid-modified polyolefin (product name: UMEX 1010, acid value 52, molecular weight 30,000, manufactured by Sanyo Chemical Industries, Ltd.) were mixed in a ratio of 51:48.5:0.5. The mixture was kneaded at 190°C for 6 minutes in a DSM Xplore Compounder 15 (manufactured by Leo Labs), heated at 190°C, molded (9 bar 2 s - 11 bar 0.5 s - 11 bar 24 s), and molded at 40°C to create a dumbbell of the resin material for molding, and the physical properties were then measured. The average particle size of the pulverized roasted product was measured using a laser diffraction particle size measuring device (Mastersizer 3000, manufactured by Malvern), and the 50% particle size on a volume basis was taken as the average particle size.

[0048] [Example 2] A molding resin material was produced in the same manner as in Example 1, except that a maleic anhydride-modified styrene-butadiene block copolymer (product name: M1943, styrene content 20%, manufactured by Asahi Kasei Corporation) was used as the thermoplastic elastomer, and the compounding ratio of the ground roasted material, polypropylene, acid-modified polyolefin, and thermoplastic elastomer was 51:43.6:0.4:5.

[0049] [Example 3] A molding resin material was produced in the same manner as in Example 2, except that the compounding ratio of the ground roasted material, polypropylene, acid-modified polyolefin, and thermoplastic elastomer was 51:38.6:0.4:10.

[0050] [Comparative Example 1] A molding resin material was produced in the same manner as in Example 1, except that no acid-modified polyolefin was added and the ground roasted material and polypropylene were mixed in a compounding ratio of 50:50.

[0051] The tensile strength of the molding resin materials produced in Examples 1 to 3 and Comparative Example 1 was measured by the following method. The results are shown in Table 1. [Measurement of tensile strength]: JIS K 6251 dumbbells were prepared using a DSM Xplore Compounder 15 (manufactured by Leo Labs) and measured at a tensile speed of 1 mm / min in accordance with JIS K 7161: Plastics - Testing method for tensile properties.

[0052] [Table 1]

[0053] As shown in Table 1, the molding resin materials of Examples 1 to 3, to which acid-modified polyolefin was added, had higher breaking strain and higher viscosity than the molding resin material of Comparative Example 1, to which no thermal acid-modified polyolefin was added, and therefore were shown to have excellent moldability.

Claims

1. (a) pulverized woody biomass roasted material having an average particle size of 100 μm or less; (b) a thermoplastic resin; and (c) an acid-modified polyolefin; A molding resin material containing The molding resin material, wherein the content of pulverized woody biomass roasted material is 40 to 90% by mass, and the content of acid-modified polyolefin is 0.1 to 1% by mass.

2. 2. The molding resin material according to claim 1, wherein the weight average molecular weight of the acid-modified polyolefin is 9,000 to 45,000.

3. 3. The molding resin material according to claim 1, wherein the acid-modified polyolefin has an acid value of 26 to 70.

4. The molding resin material according to any one of claims 1 to 3, wherein the thermoplastic elastomer comprises any one of a styrene-butadiene block copolymer, an ethylene-octene copolymer, and a propylene-ethylene copolymer.

5. The molding resin material according to any one of claims 1 to 4, wherein the thermoplastic resin comprises a polyolefin-based resin.

6. The molding resin material according to any one of claims 1 to 5, wherein the thermoplastic resin comprises a polypropylene resin.

7. The molding resin material according to any one of claims 1 to 6, wherein the thermoplastic resin comprises a biodegradable resin.

8. A method for producing a molding resin material, comprising a step of heating and kneading (a) pulverized wood biomass roasted material, (b) a thermoplastic resin, (c) an acid-modified polyolefin, and (d) a thermoplastic elastomer, The method according to any one of claims 1 to 4, wherein the content of the pulverized woody biomass roasted material in the molding resin material is 40 to 90% by mass, and the content of the acid-modified polyolefin is 0.1 to 1% by mass.

9. The method according to claim 8, wherein the molding material is continuously produced by processing in a twin-screw kneading extruder in the heating and kneading step.

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