JP2009144064A - Manufacturing method of molded body - Google Patents

Abstract

A method for producing a molded body that is lightweight and excellent in mechanical strength is provided. Moreover, the manufacturing method of a molded object with little metal mold contamination is provided.
A modified propylene grafted with a propylene polymer (A), a polylactic acid (B), an ethylene polymer (C) containing an epoxy group and / or an α, β-unsaturated glycidyl ester. A method for producing a molded article obtained by molding a resin composition containing a polymer (D), wherein thermally expandable microcapsules are added to the resin composition.
[Selection figure] None

Description

  The present invention is a modified propylene obtained by grafting a propylene polymer (A), a polylactic acid (B), an ethylene polymer (C) containing an epoxy group and / or an α, β-unsaturated glycidyl ester. The manufacturing method of the molded object formed by shape | molding the resin composition containing a type | system | group polymer (D).

In recent years, the use of polylactic acid-based resins synthesized using plants as raw materials has been studied in consideration of the impact on the global environment.
For example, Patent Document 1 discloses a foam molded in a mold of an injection molding machine in a state where the volatile foaming agent is absorbed in a polylactic acid-based resin and is molded in an unfoamed state. A method for obtaining a foam by heating an adhesive molded article is disclosed.
JP 2007-106843 A

However, the mechanical strength of the foam obtained is often not at the required level, and the mold after the foam is produced may be contaminated.
In view of the above problems, an object of the present invention is to provide a method for producing a molded article that is lightweight and excellent in mechanical strength. Moreover, it aims at providing the manufacturing method of a molded object with little metal mold contamination.

  The present inventors have found that the problems of the present invention can be solved by using the production method described below, and have completed the present invention. Specifically, the following are provided.

  The present invention is a modified propylene obtained by grafting a propylene polymer (A), a polylactic acid (B), an ethylene polymer (C) containing an epoxy group and / or an α, β-unsaturated glycidyl ester. A molded product produced by molding a resin composition containing a polymer (D), wherein a thermally expandable microcapsule is added to the resin composition. Provide a method.

  According to this invention, it becomes possible to manufacture the molded object which is lightweight and excellent in mechanical strength. Moreover, according to this invention, it becomes possible to reduce the contamination of the metal mold | die after a molded object manufacture.

  The molded product according to the present invention is grafted with a propylene polymer (A), a polylactic acid (B), an ethylene polymer (C) containing an epoxy group and / or an α, β-unsaturated glycidyl ester. And a modified propylene polymer (D). This will be described in detail below.

[Resin composition]
<Propylene polymer (A)>
The propylene polymer used in the present invention (hereinafter also referred to as component (A)) has a monomer unit derived from propylene, and is a propylene homopolymer (hereinafter also referred to as component (A-1)). And the at least 1 sort (s) of propylene polymer chosen from the group which consists of a propylene-ethylene copolymer (henceforth a component (A-2)) is used.
As propylene-ethylene copolymer (component (A-2)), propylene-ethylene random copolymer (hereinafter also referred to as component (A-2-1)), propylene-ethylene block copolymer (hereinafter referred to as component) (Also referred to as (A-2-2)). This propylene-ethylene block copolymer (component (A-2-2)) is a copolymer comprising a propylene homopolymer component and a propylene-ethylene random copolymer component.
The propylene polymer (component (A)) is preferably a propylene homopolymer (component (A-1)) or a propylene-ethylene block copolymer (component (A) from the viewpoint of rigidity, heat resistance or hardness. -2-2)).

The isotactic pentad fraction measured by ¹³ C-NMR of the propylene homopolymer (component (A-1)) is preferably 0.95 or more, more preferably 0.98 or more.
The isotactic pentad fraction of the propylene homopolymer component of the propylene-ethylene block copolymer (component (A-2)) measured by ¹³ C-NMR is preferably 0.95 or more, more preferably 0. .98 or more.

The isotactic pentad fraction is defined as A.I. Zambelli et al., Macromolecules, 6, 925 (1973), that is, isotactic linkage with pentad units in a propylene polymer molecular chain measured by ¹³ C-NMR, in other words propylene monomer units. The fraction of propylene monomer units at the center of five consecutive meso-bonded chains (however, the assignment of NMR absorption peaks is determined based on subsequently published Macromolecules, 8, 687 (1975)). . Specifically, the ratio of the mmmm peak area to the absorption peak area of the methyl carbon region measured by ¹³ C-NMR spectrum is the isotactic pentad fraction. NPL reference material CRM No. of NATIONAL PHYSICAL LABORATORY measured by this method. The isotactic pentad fraction of M19-14 Polypropylene PP / MWD / 2 was 0.944.

Intrinsic viscosity ([η] _P ) of propylene homopolymer (component (A-1)) measured in a tetralin solvent at 135 ° C., propylene homopolymer of block copolymer (component (A-2)) Intrinsic viscosity ([η] _P ) measured in a tetralin solvent at 135 ° C. of the component, Intrinsic viscosity measured in a tetralin solvent at 135 ° C. of the random copolymer (component (A-2-1)) [[ η]) is preferably 0.7 dl / g to 5 dl / g, respectively, more preferably 0.8 dl / g to 4 dl / g.

  Also, propylene homopolymer (component (A-1)), propylene homopolymer component of block copolymer (component (A-2-2)), random copolymer (component (A-2-1)) The molecular weight distribution (Q value, Mw / Mn) measured by gel permeation chromatography (GPC) is preferably 3 or more and 7 or less, respectively.

  The ethylene content contained in the propylene-ethylene random copolymer component of the block copolymer (component (A-2-2)) is 20% by mass to 65% by mass, preferably 25% by mass to 50% by mass. (However, the total amount of the propylene-ethylene random copolymer component is 100% by mass).

The intrinsic viscosity ([η] _EP ) measured in a 135 ° C. tetralin solvent of the propylene-ethylene random copolymer component of the block copolymer (component (A-2-2)) is preferably 1. It is 5 dl / g-12 dl / g, More preferably, it is 2 dl / g-8 dl / g.

  The content of the propylene-ethylene random copolymer component constituting the block copolymer (component (A-2-2)) is 10% by mass to 60% by mass, preferably 10% by mass to 40% by mass. It is.

  The melt index (MI) of the propylene homopolymer (component (A-1)) is preferably 0.1 g / 10 min to 400 g / 10 min, more preferably 1 g / 10 min to 300 g / 10 min. It is. However, the measurement temperature is 230 ° C. and the load is 2.16 kg.

  The melt flow rate (MFR) of the propylene-ethylene copolymer (component (A-2)) is preferably 0.1 g / 10 min to 200 g / 10 min, more preferably 1 g / 10 min to 150 g. / 10 minutes. However, the measurement temperature is 230 ° C. and the load is 2.16 kg.

As a method for producing a propylene polymer (component (A)), a method of homopolymerizing propylene using a Ziegler-Natta type catalyst or a metallocene catalyst, or one or more olefins selected from olefins other than propylene and Examples thereof include a method of copolymerizing with propylene. The Ziegler-Natta type catalyst includes a catalyst system using a combination of a titanium-containing solid transition metal component and an organometallic component. Examples of the metallocene catalyst include a catalyst system using a combination of a transition metal compound of Group 4 to Group 6 having at least one cyclopentadienyl skeleton and a promoter component.
Examples of the polymerization method include a slurry polymerization method, a gas phase polymerization method, a bulk polymerization method, a solution polymerization method, and a polymerization method combining these. The polymerization method may be either batch type or continuous type, and may be one-stage polymerization or multi-stage polymerization. Moreover, as a propylene polymer (component (A)), you may use a commercially available propylene polymer.

<Polylactic acid resin (B)>
The polylactic acid resin used in the present invention (hereinafter also referred to as component (B)) is a polylactic acid having a repeating unit derived from L lactic acid and / or a repeating unit derived from D lactic acid (hereinafter simply referred to as polylactic acid). ), Or a copolymer of this polylactic acid and other plant-derived polyester resin. The component (B) may contain other plant-derived polyester resins as necessary.
Examples of other plant-derived monomers copolymerizable with lactic acid include hydroxycarboxylic acids such as glycolic acid, aliphatic polyhydric alcohols such as butanediol, and aliphatic polycarboxylic acids such as succinic acid. The polylactic acid-based resin (component (B)) is a method of directly dehydrating polycondensation of lactic acid and / or other plant-derived monomers, or a cyclic dimer of lactic acid and / or hydroxycarboxylic acid (for example, lactide, glycolide, ε- Caprolactone) can be produced by a ring-opening polymerization method.

The content of the repeating unit derived from L-lactic acid or D-lactic acid contained in the above-mentioned “polylactic acid” and “polylactic acid segment in the copolymer of polylactic acid and other plant-derived polyester resin” enhances heat resistance. From the viewpoint, it is preferably 80 mol% or more, more preferably 90 mol% or more, and further preferably 95 mol% or more.
The weight average molecular weight (Mw) of the polylactic acid resin (component (B)) is preferably 10,000 or more and 1,000,000 or less, more preferably 50,000 or more and 500,000 or less. The molecular weight distribution (Q value, Mw / Mn) is preferably 1 or more and 4 or less. The molecular weight and molecular weight distribution are measured by gel permeation chromatography (GPC) using standard polystyrene as the molecular weight standard substance.

<Ethylene polymer containing epoxy group (C)>
The ethylene-based polymer containing an epoxy group used in the present invention (hereinafter also referred to as component (C)) is a copolymer having a monomer unit derived from ethylene. Examples of the monomer having an epoxy group include α, β-unsaturated glycidyl ethers such as α, β-unsaturated glycidyl esters such as glycidyl methacrylate and glycidyl acrylate, allyl glycidyl ether, and 2-methylallyl glycidyl ether. Preferably, it is glycidyl methacrylate.

  The ethylene polymer having an epoxy group as the component (C) may have a monomer unit derived from another monomer. Examples of the other monomer include methyl acrylate, Examples thereof include unsaturated carboxylic acid esters such as ethyl acrylate, methyl methacrylate and butyl acrylate, and unsaturated vinyl esters such as vinyl acetate and vinyl propylene acid.

  In the ethylene polymer having an epoxy group as the component (C), the content of the monomer unit derived from the monomer having an epoxy group is 0.01% by mass to 30% by mass, more preferably 0%. .1% by mass to 20% by mass. However, the content of monomer units derived from all monomers in the ethylene-based polymer having an epoxy group is measured by an infrared method.

  The melt flow rate (MFR) of the ethylene-based polymer having an epoxy group as the component (C) is 0.1 g / 10 min to 300 g / 10 min, preferably 0.5 g / 10 min to 80 g / 10 min. is there. The melt flow rate here is measured under the conditions of a test load of 21.18 N and a test temperature of 190 ° C. by the method defined in JIS K 7210 (1995).

  As a method for producing an ethylene polymer having an epoxy group as the component (C), a known method is used. For example, a monomer having an epoxy group by a high pressure radical polymerization method, a solution polymerization method, an emulsion polymerization method or the like. And a method of copolymerizing ethylene with another monomer as required, a method of graft-polymerizing a monomer having an epoxy group to an ethylene-based resin, and the like.

<Modified propylene polymer (D)>
The modified propylene polymer (hereinafter also referred to as component (D)) used in the present invention is a modified propylene polymer obtained by grafting an α, β-unsaturated glycidyl ester. That is, it is a polymer obtained by grafting a predetermined amount of α, β-unsaturated glycidyl ester or α, β-unsaturated glycidyl ether to a propylene-based polymer.
Examples of the α, β-unsaturated glycidyl ester include glycidyl methacrylate and glycidyl acrylate. Examples of the α, β-unsaturated glycidyl ether include allyl glycidyl ether and 2-methylallyl glycidyl ether, and glycidyl methacrylate is preferable.

  The content of the structural unit derived from the α, β-unsaturated glycidyl ester contained in the modified propylene polymer (component (D)) is 0.1% by mass or more and less than 20% by mass, More preferably, the content is greater than or equal to 5% by mass and less than 5% by mass, even more preferably greater than or equal to 0.5% and less than 1.0% by mass. However, the content of the structural unit in the modified propylene polymer is 100% by mass. In addition, the content of the structural unit derived from the α, β-unsaturated glycidyl ester is measured by an infrared method.

  The melt flow rate (MFR) of the modified propylene polymer (component (D)) is 0.1 g / 10 min to 300 g / 10 min, preferably 0.5 g / 10 min to 80 g / 10 min. Here, the melt flow rate is a value measured under conditions of a test temperature of 230 ° C. and a test load of 21.18 N according to JIS K 7210 (1995).

  Examples of the method for producing the modified propylene polymer (component (D)) include a method of melt-kneading the propylene polymer and the α, β-unsaturated glycidyl ester using a mixer or an extruder. .

As content of component (A), component (B), component (C) and component (D) used in the present invention, when the total amount of component (A) and component (B) is 100% by mass, The content of the component (A) is 10% by mass to 90% by mass, more preferably 20% by mass to 80% by mass, and the content of the component (B) is 90% by mass to 10% by mass, more preferably. It is 80 mass%-20 mass%.
Moreover, when adding a component (C) and a component (D) independently, it is 1 mass part-80 mass parts with respect to 100 mass parts of a component (A) and a component (B), respectively, Preferably 1 mass part- Contains 20 parts by weight. When adding both a component (C) and a component (D), 1 mass part-80 mass parts, Preferably 1 mass part-20 mass parts are contained.

  The said resin composition may contain the other additional component as needed. For example, foaming agents, antioxidants, weather resistance improvers, nucleating agents, flame retardants, plasticizers, lubricants, antistatic agents, various colorants, organic fillers, inorganic fillers, and elastomers other than component (C) And other resins.

  Examples of the inorganic filler include glass fiber, carbon fiber, metal fiber, glass bead, mica, calcium carbonate, titanium oxide, zinc oxide, potassium titanate whisker, talc, kaolinite, bentonite, smectite, sepiolite, wollastonite. Montmorillonite, clay, allophane, imogolite, fibrous magnesium oxysulfate barium sulfate, glass flakes, carbon black and the like.

  As an average particle diameter of an inorganic filler, they are 0.01 micrometer-50 micrometers, Preferably they are 0.1 micrometer-30 micrometers, More preferably, they are 0.1 micrometer-5 micrometers. Here, the average particle diameter of the inorganic filler is equivalent to 50% obtained from an integral distribution curve of a sieving method measured by suspending in a dispersion medium such as water or alcohol using a centrifugal sedimentation type particle size distribution measuring device. It means the particle diameter D50.

  Elastomers mean rubbery elastic bodies. Elastomers include rubber having a crosslinking point in the molecule and a thermoplastic elastomer in which the molecule is constrained by a molecular group of hard layers in the molecule.

  The elastomer is not particularly limited as long as it is an elastomer other than the component (C) described above, but a polyolefin-based elastomer (for example, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-α-olefin copolymer) Polymer, ethylene-propylene-nonconjugated diene copolymer), aliphatic polyester elastomer (for example, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polybutylene succinate carbonate), various acrylic rubbers, ethylene-acrylic Acrylic elastomers such as acid copolymers and alkali metal salts thereof (so-called ionomers), ethylene-glycidyl methacrylate copolymers, ethylene-acrylic acid alkyl ester copolymers (examples) For example, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer), acid-modified ethylene-propylene copolymer, diene rubber (eg, polybutadiene, polyisoprene, polychloroprene), copolymer of diene and vinyl monomer. Examples thereof include polymers (for example, styrene-butadiene random copolymer, styrene-butadiene-styrene block copolymer) and the like.

  Examples of the α-olefin used for the ethylene-propylene-α-olefin copolymer include α-olefins having 4 to 20 carbon atoms. Examples of the α-olefin having 4 to 20 carbon atoms include linear α-olefins and branched α-olefins. Examples of the linear α-olefin include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1 -Tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nanodecene, 1-eicocene and the like. Examples of the branched α-olefin include 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-hexene and the like.

[Method for producing molded article]
The method for producing a molded body from the above resin composition is not particularly limited, but so-called injection foam molding is preferably used. In the injection foam molding, first, the above resin composition and the thermally expandable microcapsule are introduced and mixed at a predetermined temperature. And these are filled in the cavity which the metal mold | die of an injection molding apparatus forms. The thermally expandable microcapsule is then expanded in this cavity.
The method for expanding the thermally expandable microcapsule is not particularly limited. For example, as in the so-called core back molding method, there is a method of expanding the thermally expandable microcapsules by expanding the cavity volume by retreating the cavity wall surface and foaming the molten resin composition filled in the cavity. Can be mentioned.
In addition, it is preferable that the injection amount of the resin composition and the thermally expandable microcapsule into the cavity is an amount that fills the entire cavity volume with the resin immediately after the completion of the injection.

  The injection method is not particularly limited, and examples thereof include single-axis injection, multi-axis injection, high-pressure injection, low-pressure injection, and an injection method using a plunger.

The injection foam molding may be performed in combination with a molding method such as gas assist molding, melt core molding, insert molding, core back molding, or two-color molding.
The shape of the molded body is not particularly limited, and may be any known shape.

  As the temperature in the injection foam molding, the cylinder temperature of the injection molding machine is 150 ° C. to 250 ° C., preferably 170 ° C. to 200 ° C., and the cavity temperature is 0 ° C. to 100 ° C., preferably 5 ° C. to 60 ° C., more preferably. Is 20 ° C to 50 ° C.

The back pressure during molding is 2 MPa to 10 MPa, preferably 3 MPa to 6 MPa. By setting the back pressure in such a range, it is possible to prevent the thermally expandable microcapsules in the molten resin from expanding.
The timing of expanding the thermally expandable microcapsule filled in the cavity is not particularly limited, but it is 0 to 10 seconds after filling the cavity, preferably 0 to 5 seconds, and more. Preferably after 0 second to 2 seconds.

The heat-expandable microcapsule used in the present invention has a so-called core-shell structure containing a volatile expansion agent that volatilizes at a predetermined temperature and becomes gaseous. By adding and molding this microcapsule, it is possible to reduce the weight of the resulting molded body.
The volatile swelling agent is preferably one that becomes gaseous at a temperature below the softening point of the shell. For example, ethane, ethylene, propane, n- butane, isobutane, butene, isobutene, n- pentane, isopentane, neopentane, n- hexane, heptane, low molecular weight hydrocarbons such as petroleum _{ether, CCl 3 F, CClF 2 -CClF} 2 And chlorofluorocarbons such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trialkyl-n-propylsilane. These may be used alone or in combination of two or more.
The base polymer of the shell is preferably a resin such as a phenolic resin, a vinylidene chloride resin, or an acrylonitrile resin.

  The expansion start temperature of the thermally expandable microcapsule is 100 ° C to 200 ° C, preferably 150 ° C to 200 ° C, and the maximum expansion temperature is 150 ° C to 250 ° C, preferably 180 ° C to 220 ° C.

The amount of the thermally expandable microcapsule added is not particularly limited because it depends on the expansion coefficient of the molded body, but is 0.5 to 30 parts by mass, preferably 100 parts by mass with respect to 100 parts by mass of the resin composition. 1 mass part-20 mass parts, More preferably, they are 3 mass parts-15 mass parts.
By setting it as such addition amount, it becomes possible to obtain the molded object which is lightweight and excellent in mechanical strength. Moreover, it becomes possible to reduce the contamination of the mold after manufacturing the molded body.

The molded body obtained by such a method has two skin layers of front and back and a core layer disposed between these skin layers.
FIG. 1 is a view showing a cross section of a molded body 1 according to the present invention. As described above, the molded body 1 is disposed between the front and back skin layers 10a and 10b in which the heat-expandable microcapsules are not substantially expanded, and the skin layers 10a and 10b. And a foam layer 20 having a plurality of bubbles 21 formed by expansion of the conductive microcapsule.
The thicknesses L1 and L2 of the skin layers 10a and 10b are each 100 μm or more, preferably 200 μm or more, more preferably 200 μm to 1 mm, and further preferably 200 μm to 600 μm. By setting the thickness of the skin layer in such a range, a molded body having excellent strength can be provided. In the present invention, the average value of L1 and L2 is the thickness of the skin layer of the molded body.
The density of the entire molded body 1 is 0.95 g / cm ³ or less, preferably 0.8 g / cm ³ or less, more preferably 0.6 g / cm ³ or less. By setting the density in such a range, the molded body can be reduced in weight. In addition, the value measured by the underwater substitution method is used for the density in the present invention.

In the present invention, the bubble 21 means a capsule after expansion of the thermally expandable microcapsule, but is not limited thereto, and includes bubbles formed only by a gas such as a foaming agent. Moreover, although the bubble 21 mainly points out what is substantially independent, the thing connected in multiple numbers is also contained. The average cell diameter in the foam layer 20 is 500 μm to 10 μm, preferably 400 μm to 50 μm, more preferably 200 μm to 50 μm.
As shown in FIG. 1, the average cell diameter is an average value calculated from the cell diameter in the foam layer 20. Each bubble diameter is an average value ((D1 + D2) / 2) of the largest long diameter (D1) of each individual bubble and the short diameter (D2) perpendicular to the long diameter.

The cell density of the foam layer is 5 × 10 ⁴ cells / cm ³ to 1 × 10 ⁷ cells / cm ³ , preferably 1 × 10 ⁵ cells / cm ^{3 to} 5 × 10 ⁶ cells / cm ³ . Preferably, it is 1 × 10 ⁵ pieces / cm ³ to 1 × 10 ⁶ pieces / cm ³ . By setting the average cell diameter and cell density in the foamed layer within the above ranges, it is possible to reduce the weight of the molded body and improve the strength.
The bubble density of the foamed layer is a value obtained by converting the number of bubbles in the foamed layer into the number of bubbles per unit area (1 cm ² ) and raising the number of bubbles to 3/2.

  The expansion coefficient of the molded product according to the present invention is a value obtained by dividing the density of the resin composition by the density of the molded product 1 as a whole, preferably more than 1 time and 10 times or less, and 1.05 times to 3 times. It is more preferable that The expansion coefficient of the obtained molded body can be obtained by dividing the density of the resin composition by the density of the molded body with respect to the density of the resin composition and the density of the molded body.

  The molded object obtained by the manufacturing method which concerns on this invention can be used suitably for uses, such as components for motor vehicles, parts for household appliances, and other industrial products.

  EXAMPLES Hereinafter, although this invention is demonstrated in more detail based on an Example, this invention is not limited to these Examples.

In the examples or comparative examples, the following resins and thermally expandable microcapsules were used.
(1) Propylene homopolymer (A-1)
“Product name: X101A” manufactured by Sumitomo Chemical Co., Ltd.
MFR: 40 (g / 10 min)
(2) Propylene- (propylene-ethylene) copolymer (A-2)
"Product name: WPX5343" manufactured by Sumitomo Chemical Co., Ltd.
MFR: 50 (g / 10 minutes)

(3) Polylactic acid resin (B)
"Product name: Terramac TE-4000" manufactured by Unitika Ltd.
(4) Ethylene-glycidyl methacrylate copolymer (C)
"Product name: Bond First E" manufactured by Sumitomo Chemical Co., Ltd.
MFR (190 ° C.): 3 (g / 10 minutes)
Monomer unit content derived from glycidyl methacrylate: 12% by mass
(5) Ethylene-butene copolymer rubber (E)
"Product name: CX5505" manufactured by Sumitomo Chemical Co., Ltd.
Density: 0.878 (g / cm ³ )
MFR (190 ° C.): 14 (g / 10 minutes)

(6) Thermally expandable microcapsule (F-1)
A master batch of thermally expandable microcapsules filled with a blowing agent (low molecular weight polyethylene added with 30% microcapsules) was used.
Average particle size: 20 μm
Maximum expansion temperature: 210-220 ° C

(7) Foaming agent (F-2)
A baking soda-based foaming agent was used as the foaming agent.
"Product name: MB3274" manufactured by Sankyo Kasei

[Evaluation methods]
(1) Melt flow rate (MFR)
In accordance with JIS K7210, a resin mainly composed of a repeating unit derived from propylene was measured under the conditions of a temperature of 230 ° C. and a load of 21.2N.

(2) Monomer unit content derived from glycidyl methacrylate (unit: mass%)
A press sheet was prepared, and the absorbance of the characteristic absorption in the infrared absorption spectrum was corrected with the thickness, and the calibration curve method was used. In addition, as the glycidyl methacrylate characteristic absorption, a peak at 910 cm ⁻¹ was used.

(3) Density The density of the compact was determined by measuring the specific gravity with a hydrometer (Mirage Trading Co., Ltd., electronic hydrometer EW-200SG), and the density of pure water was 1.0 g / cm ³ .

(4) Expansion coefficient The expansion coefficient of the molded body was obtained by dividing the density of the resin composition by the density of the molded body with respect to the density of the resin composition and the density of the molded body measured by the above-described density measurement method.

(5) Average cell diameter The molded body is cut, the cross section is observed with a microscope (manufactured by SCARA Co., Ltd., digital field microscope DC-3), the foam cross section is photographed, and in the vicinity of the skin layer and the center of the foam layer. Arbitrary 500 μm squares were selected and the bubble diameter in each square was measured and averaged.

(6) Bubble density In the cross section taken above, the number of bubbles in the square was counted and converted to the number of bubbles per 1 cm ² , and then the bubble density was calculated by raising to the power of 1.5.

(7) Impact value The impact value of the molded body was measured by a HIGH RATE IMPACT TESTER (manufactured by Reometrics. Inc.) as a measurement condition with a 1/2 inch dart diameter and a sample fixed with a 3 inch ring at a speed of 5 m / sec. The waveform of displacement and load was measured. Thereafter, the energy value required for impact was calculated.
(8) Mold Contamination A sample having no deposit on the surface that comes into contact with the molded product of the mold at the time when 10 molded articles were molded was rated as ◯, and a sample having a deposit was marked as x.

[Example 1]
The molded body was produced by the following method.
Using a 50 mmφ twin-screw kneading extruder (TEM 50A manufactured by Toshiba Machine Co., Ltd.), the cylinder temperature was set to 190 ° C. with the ratio and feed method shown in Table 1, the extrusion rate was 50 kg / hr, the screw rotation speed was 200 rpm, and the heat for foaming A pellet of the plastic resin composition was obtained.
Using this pellet, an injection molding machine having a clamping force of 100 tons was used, and the molded product was molded using a flat plate shape (gate structure: valve gate, side gate) having a molded product size of 260 mm × 330 mm and a thickness of 2 mmt.
Then, as shown in Table 1, a predetermined amount of thermally expandable microcapsules are mixed with the resin composition, injected at a molding temperature of 200 ° C. and a mold temperature of 20 ° C. so as to be fully filled in the mold, After 0.5 seconds had passed without injection, the mold cavity was expanded to expand the thermally expandable microcapsules, which were then cooled and solidified to obtain molded bodies for evaluation. The results are shown in Table 1.

[Comparative Example 1]
As an injection molding machine, ES2550 / 400HL-MuCell manufactured by Engel Co., Ltd. (clamping force 400 tons), and as a mold, the molded part dimensions are 290mm x 370mm, height 45mm, thickness 2mmt (gate structure: valve gate) The molded body was molded using the one having a central part of the molded body, and evaluated in the same manner as in Examples except that a foaming agent was added instead of the thermally expandable microcapsule described in Table 1.

FIG. 1 is a view showing a cross section of a molded body according to the present invention.

Explanation of symbols

1 Molded body 10a, 10b Skin layer 20 Core layer 21 Bubble

Claims (4)

A modified propylene polymer obtained by grafting a propylene polymer (A), a polylactic acid resin (B), an ethylene polymer (C) containing an epoxy group and / or an α, β-unsaturated glycidyl ester. A method for producing a molded article obtained by molding a resin composition containing the coalescence (D),
A method for producing a molded article, comprising adding thermally expandable microcapsules to the resin composition.   The method for producing a molded article according to claim 1, wherein an expansion start temperature of the thermally expandable microcapsule is 100 ° C to 200 ° C.   The method for producing a molded body according to claim 1 or 2, wherein an average particle size of the thermally expandable microcapsules in the molded body is 10 µm to 500 µm.   The method for producing a molded article according to any one of claims 1 to 3, wherein the content of the thermally expandable microcapsule is 0.5 to 30 parts by mass with respect to 100 parts by mass of the resin composition.

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