JP2009144061A - Foam molding - Google Patents

Abstract

An object of the present invention is to provide a foamed molded article that is lightweight and excellent in strength.
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 are grafted. A foamed molded article obtained by molding a resin composition containing a modified propylene polymer (D), having a density of 0.95 g / cm ³ or less, and two skin layers on the front and back sides; A foam layer having a plurality of bubbles disposed between the skin layers, and the thickness of a single layer of the skin layer is 100 μm or more, and an average cell of the plurality of bubbles in the foam layer The diameter is 500 μm or less, and the cell density in the foam layer is 5 × 10 ⁴ cells / cm ³ to 1 × 10 ⁷ cells / cm ³ .
[Selection] Figure 1

Description

  The present invention relates to a foam molded article having a predetermined structure. Specifically, 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 are grafted. It is related with the foaming molding formed by shape | molding the resin composition containing modified propylene polymer (D) which becomes.

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 foamed molded article by heating an adhesive molded article is disclosed.
JP 2007-106843 A

  However, with regard to the weight and strength of the obtained foamed molded product, there are currently many that do not reach the required level.

  In view of the above problems, an object of the present invention is to provide a foamed molded article that is lightweight and excellent in strength.

  The present inventors have found that it is possible to provide a foam molded body that is lightweight and excellent in strength by setting the structure of the foam molded body to a predetermined structure, and the present invention has been completed. . Specifically, the following are provided.

In the present invention, 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 are grafted. A foamed molded article obtained by molding a resin composition containing a modified propylene polymer (D), having a density of 0.95 g / cm ³ or less, and two skin layers on the front and back sides; A foam layer having a plurality of bubbles disposed between the skin layers, and the thickness of a single layer of the skin layer is 100 μm or more, and an average cell of the plurality of bubbles in the foam layer A diameter is 500 micrometers or less, and the bubble density in the said foaming layer provides the foaming molding which is 5 * 10 < ⁴ > piece / cm < ³ > -1 * 10 < ⁷ > piece / cm < ³ >.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the foaming molding which is lightweight and excellent in intensity | strength.

  As described above, the foamed molded product according to the present invention has a skin layer and a foamed layer having a predetermined structure. This will be described in detail below.

[Foamed molded product]
FIG. 1 is a view showing a cross section of a foamed molded article 1 according to the present invention. The foam-molded body 1 includes two skin layers 10a and 10b having substantially no air bubbles, and a foam layer 20 having a plurality of air bubbles 21 disposed between the skin layers 10a and 10b. Consists of. 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, it is possible to provide a foamed molded article having excellent strength. In the present invention, the average value of L1 and L2 is the thickness of the skin layer of the foam molded article.
The density of the entire foamed molded article 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, and even more preferably 0.5 g / cm ³ or less. It is. By setting the density in such a range, the foamed molded product 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 bubbles 21 mainly indicate substantially independent ones, but a plurality of bubbles 21 are also included. The average cell diameter in the foam layer 20 is 500 μm or less, preferably 500 μm to 30 μm, more preferably 400 μm to 50 μm, and still more preferably 200 μm to 50 μm.
As shown in FIG. 1, the average cell diameter is divided into three regions (in this embodiment, the foam layer 20 in the vicinity of the skin layer (region (a), region (b)) and the central portion (region (c)). The average value calculated from the average bubble diameter in each region. And the bubble diameter in each area | region says the average value ((D1 + D2) / 2) of the largest long diameter (D1) of each bubble, and the short diameter (D2) orthogonal 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 2 × 10 ⁵ cells / cm ^{3 to} 5 × 10 ⁶ cells / cm ³ . It is preferably 20 × 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, the foamed molded product can be reduced in weight and the strength can be improved.
The cell density of the foamed layer is an average value of the cell densities in the respective regions (a) to (c). The bubble density is a value obtained by converting the number of bubbles in each region into the number of bubbles per unit area (1 cm ² ) and multiplying the number of bubbles by 3/2.

  The foaming ratio of the foamed molded product according to the present invention is a value obtained by dividing the density of the resin composition by the density of the entire foamed molded product 1, preferably more than 1 and not more than 10 times, 1.05 It is more preferable that it is double to 3 times.

[Resin composition]
The foamed molded article having the structure as described above is composed of a propylene polymer (A), a polylactic acid resin (B), an ethylene polymer (C) containing an epoxy group and / or an α, β-non-polymer. A resin composition containing a modified propylene polymer (D) formed by grafting a saturated glycidyl ester is molded. This resin composition will be described in detail below.

<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 flow rate (MFR) 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. Minutes. 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-based polymer having an epoxy group as the component (C) may have a monomer unit derived from another monomer. Examples of the other monomer include unsaturated carboxylic acid esters such as methyl acrylate, 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 50% by mass to 90% by mass, and the content of the component (B) is 90% by mass to 10% by mass, more preferably. It is 50 mass%-10 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. By setting it as such addition amount, it becomes possible to provide the foaming molding which is lightweight and excellent in intensity | strength.

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

[Molding method]
As a method for producing a foam molded article from the above resin composition, for example, a known method such as injection foam molding or press foam molding can be employed. Among these, it is preferable to form by injection foam molding.
In the injection foam molding, a molten resin composition in which a foaming agent described later is dissolved in the above resin composition is filled in a cavity formed by a mold of an injection molding apparatus, and the molten resin is foamed in the cavity. Then, the foamed molten resin is cooled and solidified.
In this injection foam molding, the method of foaming the resin composition is not particularly limited. For example, as in the so-called core back molding method, there is a method of expanding the cavity volume by retreating the cavity wall surface so as to expand the gas of the foaming agent and foam the molten resin composition filled in the cavity. .
The amount of molten resin composition injected into the cavity is preferably such that the entire cavity volume is filled with resin immediately after the end of injection.

  The injection method in the injection foam molding 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 any molding method such as gas assist molding, melt core molding, insert molding, core back molding, and two-color molding.
The shape of the thermoplastic resin foam molded article is not particularly limited, and may be any known shape.

  The temperature conditions in the injection foam molding are: 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 at the time of molding is 2 MPa to 10 MPa, preferably 3 MPa to 6 MPa when using a chemical foaming agent and microcapsules described later as the foaming agent, and 2 MPa to 30 MPa when using a physical foaming agent. The pressure is preferably 5 MPa to 20 MPa, more preferably 6 to 15 MPa. By setting the back pressure in such a range, it is possible to prevent the molten resin composition from foaming in the cylinder.

  The timing of foaming the molten resin composition filled in the cavity is not particularly limited, but when using the chemical foaming agent and microcapsules described later, 0 seconds to 10 seconds after filling the cavity. Second, preferably 0 to 5 seconds, more preferably 0 to 2 seconds. And when using a physical foaming agent as a foaming agent, it is 0 second-20 seconds after filling in a cavity, Preferably it is 3 seconds-15 seconds, More preferably, it is 3 seconds-10 seconds.

  The foaming agent used in the present invention is not particularly limited, and known ones such as chemical foaming agents, physical foaming agents, and thermal expansion microcapsules can be used. You may use these individually or in combination of 2 or more types.

  The chemical foaming agent is not particularly limited as long as it does not decompose below the melting temperature of the thermoplastic resin but decomposes or reacts above the melting temperature of the thermoplastic resin and does not generate water during the decomposition or reaction. For example, an azo compound, a nitroso compound, a hydrazo compound, etc. are mentioned.

  Examples of the azo compound include azodicarbonamide (ADCA). An example of the Toroso compound is dinitrosopentamethylenetetramine (DPT). Examples of the hydrazo compound include hydrazodicarbonamide.

Examples of the physical foaming agent include inert gases such as nitrogen and carbon dioxide, and volatile organic compounds other than chlorofluorocarbons such as butane and pentane.
Examples of the inert gas include carbon dioxide, nitrogen, argon, neon, helium, oxygen, and the like. These may be used alone or in combination of two or more. Of these, carbon dioxide and nitrogen are preferably used.

  Thermal expansion type microcapsules (also simply referred to as microcapsules) include a volatile expansion agent that becomes gaseous at a temperature below the softening point of the shell as a core agent. The microcapsule has a foaming start temperature of 100 ° C to 200 ° C, preferably 150 ° C to 200 ° C.

The volatile swelling agent is preferably a substance that becomes gaseous at a temperature below the softening point of the polymer constituting 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 shell of the thermal expansion microcapsule is preferably made of a resin composition containing a phenol resin, a vinylidene chloride resin, an acrylonitrile resin, or the like.

The addition amount of the foaming agent is 0.5 parts by mass to 10 parts by mass, preferably 1 part by mass to 5 parts by mass, in the case of the chemical foaming agent, with respect to 100 parts by mass of the resin composition. In the case of a physical foaming agent, in the physical foaming agent field, 0.3 to 10 parts by weight, preferably 0.6 to 5 parts by weight, more preferably 0.6 to 2 parts by weight. It is. And in the case of a thermally expansible microcapsule, they are 1 mass part-30 mass parts, Preferably they are 3 mass parts-20 mass parts.
By setting it as such addition amount, it becomes possible to make the average bubble diameter, bubble density, etc. of a foaming molding obtained into a desired value. In addition, when the content of the foaming agent is out of the above range, the molding cost and the molding pressure may increase.

  The foamed molded article of the present invention can be suitably used for applications such as electrical parts, automotive parts, 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 foaming agents 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) Foaming agent (F-1)
Azodicarbonamide was used as a blowing agent.
"Product name: MB-31" manufactured by Sankyo Kasei

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

(4) Foaming ratio The foaming ratio of the foamed molded product is obtained by dividing the density of the resin composition by the density of the foamed molded product with respect to the density of the resin composition and the density of the foamed molded product measured by the above density measurement method. Asked.

(5) Skin Layer Thickness Cut the foam molded body, observe the cross section with a microscope (Digital Field Microscope DC-3, manufactured by SCARA Co., Ltd.), photograph the foam cross section, The thickness was measured and the average value was determined.

(6) Average bubble diameter From the foamed cross section photographed above, arbitrary 500 μm squares were selected in the vicinity of the skin layer and the center of the foam layer, and the bubble diameter in each square was measured and averaged.

(7) Bubble density The bubble density was calculated by counting the number of bubbles in the above square with the foamed cross section taken above, converting it to the number of bubbles per 1 cm ² , and multiplying by 1.5.

(8) Mold contamination The case where there was no deposit on the surface in contact with the molded product of the mold at the time when 10 foam molded articles were molded was marked with ◯, and the one with deposit was marked with x.

(9) Impact value The impact value of the foamed molded article was fixed by a HIGH RATE IMPACT TESTER (manufactured by Reometrics. Inc.) with a dart diameter of 1/2 inch as a measurement condition and a 3 inch ring at a speed of 5 m / sec. The sample was punched and the displacement and load waveforms were measured. Thereafter, the energy value required for impact was calculated.

[Example 1]
A foam molded article 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, ES2550 / 400HL-MuCell manufactured by Engel Co., Ltd. (clamping force 400 tons) is used as an injection molding machine, and the molded product part dimensions shown in FIG. 1 are 290 mm × 370 mm, height 45 mm, thickness. Foam molding was performed using a 2 mmt box shape (gate structure: valve gate, foam molded body central portion). As shown in Table 1, the foaming agent is mixed with a thermoplastic resin composition for foaming to test a predetermined amount of ADCA-based foaming agent, and filled in a mold at a molding temperature of 200 ° C. and a mold temperature of 20 ° C. After 0.5 seconds after injection filling without applying pressure, expand the mold cavity and foam the molten resin, then cool and solidify the foamed resin to obtain a foam molded body, Evaluation was performed. The results are shown in Table 1.

[Comparative Example 1]
Except for the foaming agents described in Table 1, the evaluation was performed in the same manner as in the examples.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Foam molding 10a, 10b Skin layer 20 Foam layer 21 Bubble

Claims (3)

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 foamed molded article formed by molding a resin composition containing the coalesced (D),
The density is 0.95 g / cm ³ or less, and
It is composed of two skin layers, front and back, and a foam layer disposed between these skin layers and having a plurality of bubbles,
The thickness of the single layer of the skin layer is 100 μm or more,
The average bubble diameter of the plurality of bubbles in the foam layer is 500 μm or less,
The foam density in the foam layer is 5 × 10 ⁴ cells / cm ³ to 1 × 10 ⁷ cells / cm ³ . The content of the propylene polymer (A) in the resin composition is 10% by mass to 90% by mass, and the content of the polylactic acid resin (B) is 90% by mass to 10% by mass. Yes,
The content of the ethylene-based polymer (C) containing the epoxy group and / or the modified propylene-based polymer (D) in which the α, β-unsaturated glycidyl ester is graphed is the content of the propylene-based polymer ( The foamed molded product according to claim 1, which is 1% by mass to 80 parts by mass with respect to 100 parts by mass of A) and the polylactic acid resin (B).   The foam molded article according to claim 1 or 2, which is molded by an injection molding method.

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