JP2019044002A - Polylactic acid-containing propylene resin composition excellent in foamability during injection molding and foam molding of the same - Google Patents

Abstract

An object of the present invention is to provide a polylactic acid-containing propylene-based resin composition having excellent production stability and foamability during injection molding, and a foamed molded article thereof. SOLUTION: It contains 40 to 88 parts by mass of a polypropylene resin (A), 1 to 30 parts by mass of a polypropylene alone resin (B), 10 to 50 parts by mass of a polylactic acid resin (C), and an epoxy group. A polylactic acid-containing propylene-based resin composition containing 1 to 10 parts by mass of an ethylene-based polymer (D) and having a melt flow rate (measurement conditions: 230 ° C, 21.18 N) of 10 to 100 g / 10 minutes or less. (However, the total content of the polypropylene-based resin (A), the polypropylene-based resin (B), the polylactic acid-based resin (C), and the ethylene-based polymer (D) containing an epoxy group is 100 parts by mass.) [Selection diagram] FIG.

Description

  The present invention relates to a polylactic acid-containing propylene resin composition and a foamed molded product thereof.

  In recent years, considering the impact on the global environment, the use of polylactic acid resins synthesized from plants as raw materials has been studied, and composites with polypropylene resins have been developed for the purpose of improving molding processability and mechanical properties. It has been made and improvements for solving various problems have been made.

  For example, Patent Document 1 describes a resin composition characterized by containing a polylactic acid resin, a propylene polymer, and an ethylene polymer containing an epoxy group, and propylene-ethylene having a specific intrinsic viscosity. By including a propylene-based polymer containing a random copolymer component, attempts have been made to improve mechanical strength, anisotropy of shrinkage of molded articles, dimensional stability, appearance, and the like. Further, Patent Document 2 attempts to improve the dispersibility, impact resistance, and moldability of a polylactic acid resin by including two types of propylene polymers having different MFRs.

  On the other hand, foam molding has been attempted in the prior art to reduce the weight of parts. For example, Patent Document 3 discloses that a foaming agent is obtained by adding a foaming agent at the time of injection molding, and Patent Document 4 discloses aliphatic polyester, polyolefin having a specific melt tension, and functional group-containing hydrogenation. A method for producing a foamed molded article having a step of foam-molding a resin composition containing a diene polymer using a foaming agent is disclosed.

  However, the productivity of the resin composition may be lowered due to the improvement of the foam moldability, and the stabilization of the productivity and the further improvement of the foam moldability have been demanded.

JP 2009-155517 A JP 2010-163614 A JP 2009-144061 A JP 2012-229416 A

  An object of this invention is to provide the polylactic acid containing propylene-type resin composition excellent in production stability and the foamability at the time of injection molding, and its foaming molding.

That is, the present invention includes the following inventions.
[1] 40 to 88 parts by mass of a polypropylene resin (A);
1-30 parts by mass of a polypropylene-only resin (B),
10 to 50 parts by mass of polylactic acid resin (C),
It contains 1 to 10 parts by mass of an ethylene-based polymer (D) containing an epoxy group, and the melt flow rate (measurement conditions: 230 ° C., 21.18 N) is 10 g / 10 min or more and 100 g / 10 min or less. Polylactic acid-containing propylene-based resin composition (however, the content of the polypropylene-based resin (A), the polypropylene-only resin (B), the polylactic acid-based resin (C), and the ethylene-based polymer (D) containing an epoxy group) The total is 100 parts by mass),
The polypropylene resin (A) is a propylene homopolymer having an intrinsic viscosity of 0.8 to 3.0 dl / g measured in a tetralin solvent at 135 ° C., or the intrinsic viscosity is 0.8 to More than 70% by mass of a 3.0 dl / g propylene homopolymer component and 95% by mass or less, and 5% by mass to less than 30% by mass of the propylene-ethylene random copolymer component having the intrinsic viscosity of 2-9 dl / g. A propylene-ethylene block copolymer consisting of
The polypropylene single resin (B) has a propylene homopolymer component of 3 to 30% by mass with an intrinsic viscosity of 5 to 10 dl / g measured in a tetralin solvent at 135 ° C., and the intrinsic viscosity of less than 5 dl / g. A propylene homopolymer containing 70 to 97% by mass of a propylene homopolymer component,
The polylactic acid resin (C) is a polylactic acid-containing propylene resin composition having a melt flow rate (measurement conditions: 230 ° C., 21.18 N) of 10 g / 10 min or more and 50 g / 10 min or less.
[2] The polylactic acid-containing propylene resin composition according to the above [1], wherein the content of the polypropylene single resin (B) is 3 to 12 parts by mass.
[3] A foam molded article obtained by molding the polylactic acid-containing propylene resin composition according to the above [1] or [2].

  The polylactic acid-containing propylene-based resin composition of the present invention has good production stability and excellent foamability during injection molding. The foamed molded product of the present invention can contribute to weight reduction of resin parts for automobiles.

It is a microscope picture which shows the foamability of the injection molding obtained from the resin composition of Example 1-2 and Comparative Example 1-2.

  The polylactic acid-containing propylene resin composition of the present invention (also referred to as the resin composition of the present invention) is a polypropylene resin (A) having a specific intrinsic viscosity (hereinafter also referred to as component (A)), a specific intrinsic viscosity. Polypropylene-based resin (B) having the following (hereinafter also referred to as component (B)), polylactic acid resin (C) having a specific melt flow rate (hereinafter also referred to as component (C)), and an epoxy group An ethylene polymer (D) (hereinafter also referred to as component (D)) is contained in a specific amount and has a specific melt flow rate.

[Polypropylene resin (A)]
The polypropylene resin (A) used in the resin composition of the present invention is a propylene homopolymer having an intrinsic viscosity of 0.8 to 3.0 dl / g measured in a tetralin solvent at 135 ° C, or The propylene homopolymer component having an intrinsic viscosity of 0.8 to 3.0 dl / g exceeds 70 mass% and is 95 mass% or less, preferably 75 to 90 mass%, and the intrinsic viscosity is 2 to 9 dl / g. The propylene-ethylene random copolymer component g is a propylene-ethylene block copolymer composed of 5% by mass or more and less than 30% by mass, preferably 10% by mass or more and 25% by mass or less.

  When the polypropylene resin (A) is a propylene homopolymer, the intrinsic viscosity measured in a 135 ° C. tetralin solvent of the polypropylene resin (A) is 0 from the viewpoint of productivity of the resin composition and foam moldability. .8 to 3.0 dl / g, preferably 1.0 to 2.0 dl / g.

  When the polypropylene resin (A) is a propylene-ethylene block copolymer, the propylene homopolymer component has an intrinsic viscosity of 0.8 to 3.0 dl / g, preferably 1.0 to 2.0 dl / g. The intrinsic viscosity of the propylene-ethylene random copolymer component is 2 to 9 dl / g, preferably 2.2 to 5.0 dl / g. By making the intrinsic viscosity of the propylene homopolymer component within the above range, the productivity of the resin composition and the deterioration of the foam moldability can be prevented. By setting the intrinsic viscosity of the propylene-ethylene random copolymer component to be equal to or higher than the above lower limit value, it is possible to prevent the foam moldability from being lowered. By setting the intrinsic viscosity of the propylene-ethylene random copolymer component to the upper limit or less, the propylene-ethylene random copolymer component can be prevented from becoming a gel and deteriorating the appearance of the molded product. The propylene homopolymer component of the propylene-ethylene block copolymer can be obtained by taking it out from the polymerization tank after the polymerization of the propylene homopolymer component in the first step during the production thereof, and the taken out propylene homopolymer Thus, the intrinsic viscosity in the 135 ° C. tetralin solution can be determined. The intrinsic viscosity can be measured, for example, by the method described in the section “(3) Intrinsic viscosity (unit: dl / g)” below. The intrinsic viscosity of the propylene-ethylene random copolymer component contained in the propylene-ethylene block copolymer in a 135 ° C. tetralin solution is, for example, a propylene homopolymer as described in JP-A-2000-109620. It can be determined by measuring the intrinsic viscosity of each of the coalescence component and the entire propylene-ethylene block copolymer.

  The polypropylene resin (A) can be produced by a method of polymerizing a monomer using a stereoregular olefin polymerization catalyst. As the catalyst, a known stereoregular olefin polymerization catalyst can be used, and examples thereof include a Ziegler-Natta catalyst system, a metallocene catalyst system, and a catalyst system combining them. Examples of the polymerization method include a bulk polymerization method, a solution polymerization method, a slurry polymerization method, a gas phase polymerization method, or a polymerization method in which these polymerization methods are arbitrarily combined. A continuous gas phase polymerization method is preferable. . Polymerization conditions such as polymerization temperature, polymerization pressure, monomer concentration, catalyst input amount and polymerization time can be appropriately determined according to the composition and structure of the target polypropylene resin (A).

  When the polypropylene resin (A) is a propylene-ethylene block copolymer, the production method is preferably a first method for obtaining a propylene homopolymer component by homopolymerizing propylene in the presence of a stereoregular olefin polymerization catalyst. This is a multistage polymerization comprising a step and a second step following the first step, in which a propylene-ethylene copolymer component is obtained by copolymerizing ethylene and propylene in the presence of the propylene homopolymer component. The multistage polymerization is also referred to as a polymer blend.

  Polypropylene resin (A) has a content of component (A), component (B), component (C) and component (D) from the viewpoint of production stability of the composition and uniform foamed cells in the molded product. When the total is 100 parts by mass, the resin composition of the present invention contains 40 to 88 parts by mass, preferably 45 to 75 parts by mass.

[Polypropylene single resin (B)]
The polypropylene single resin (B) used in the resin composition of the present invention has a propylene homopolymer component of 3 to 30% by mass with an intrinsic viscosity of 5 to 10 dl / g measured in a tetralin solvent at 135 ° C., A propylene homopolymer containing 70 to 97% by mass of a propylene homopolymer component having an intrinsic viscosity of less than 5 dl / g. Here, the polypropylene single resin (B) is preferably composed of the propylene homopolymer component. The intrinsic viscosity of each propylene homopolymer component contained in the component (B) can be measured in the same manner as described above for the component (A).

  The propylene homopolymer component having an intrinsic viscosity of 5 to 10 dl / g measured in a 135 ° C. tetralin solvent contained in the polypropylene homopolymer resin (B) is preferably 5.5 to 9.0 dl / g. Has viscosity. The effect which improves foam moldability is acquired as it is more than the said lower limit, and it can prevent that the defect by a dispersion | distribution defect worsens a shaping | molding external appearance as it is below the said upper limit. The content of the propylene homopolymer component having an intrinsic viscosity of 5 to 10 dl / g measured in a tetralin solvent at 135 ° C. in the polypropylene homopolymer resin (B) is from the viewpoint of uniform foamed cells in the molded article. And 3 to 30% by mass, preferably 5 to 25% by mass with respect to the polypropylene single resin.

  The propylene homopolymer component having an intrinsic viscosity of less than 5 dl / g measured in a tetralin solvent at 135 ° C. contained in the polypropylene homopolymer (B) preferably has an intrinsic viscosity of 0.9 to 3 dl / g. . If it is less than the above upper limit, the take-up property of the strand during production of the composition will be good, and the productivity will be excellent. The content of the propylene homopolymer component having an intrinsic viscosity of less than 5 dl / g measured in a tetralin solvent at 135 ° C. in the polypropylene homopolymer resin (B) is, from the viewpoint of homogenizing the foamed cells in the molded product, It is 70-97 mass% with respect to a polypropylene single resin, Preferably it is 75-95 mass%.

  Polypropylene single resin (B) can be manufactured by the method of superposing | polymerizing a monomer using a stereoregular olefin polymerization catalyst. As the catalyst, a known stereoregular olefin polymerization catalyst can be used, and examples thereof include a Ziegler-Natta catalyst system, a metallocene catalyst system, and a catalyst system combining them. Specific polymerization methods include, for example, And can be produced by the method of JP-A-11-228629.

  Polypropylene single resin (B) is the content of component (A), component (B), component (C) and component (D) from the viewpoint of stabilizing the production of the composition and making the foamed cells uniform in the molded body. 1 to 30 parts by mass, preferably 3 to 25 parts by mass, and more preferably 3 to 12 parts by mass in the resin composition of the present invention.

[Polylactic acid resin (C)]
The polylactic acid resin (C) used in the resin composition of the present invention is:
A resin comprising a polymer consisting only of repeating units derived from L-lactic acid and / or D-lactic acid,
A resin comprising a copolymer comprising a repeating unit derived from L-lactic acid and / or D-lactic acid and a repeating unit derived from a monomer other than L-lactic acid and D-lactic acid, or L-lactic acid and / or D-lactic acid From a mixture of a polymer consisting only of a repeating unit derived from a repeating unit derived from L-lactic acid and / or D-lactic acid and a repeating unit derived from a monomer other than L-lactic acid and D-lactic acid It is preferable that it is resin which becomes. In addition, the repeating unit derived from L-lactic acid and the repeating unit derived from D-lactic acid may be referred to as an L-lactic acid-derived repeating unit and a D-lactic acid-derived repeating unit, respectively.

Examples of monomers other than the L-lactic acid and D-lactic acid include hydroxycarboxylic acids such as glycolic acid, aliphatic polyhydric alcohols such as butanediol, and aliphatic polycarboxylic acids such as succinic acid. Polylactic acid resin (C)
A method of dehydrating polycondensation of lactic acid (L-lactic acid, D-lactic acid, or a mixture of L-lactic acid and D-lactic acid) and, if necessary, other monomers,
A method of ring-opening polymerization of a cyclic dimer of lactic acid (ie, lactide),
Ring-opening polymerization of lactide and a cyclic bimolecular condensate of lactic acid and a hydroxycarboxylic acid other than lactic acid,
Cyclic bimolecular condensate of lactide and / or lactic acid and hydroxycarboxylic acid other than lactic acid, and if necessary, cyclic dimer of hydroxycarboxylic acid other than lactic acid (for example, glycolide) or cyclic ester derived from hydroxycarboxylic acid (For example, ε-caprolactone) can be produced by a ring-opening polymerization method.

  When the polylactic acid resin (C) contains a polymer containing both L-lactic acid-derived repeating units and D-lactic acid-derived repeating units, from the viewpoint of heat resistance of the resin composition of the present invention, in the polymer, The content of the repeating unit derived from L-lactic acid or the content of the repeating unit derived from D-lactic acid is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 95 mol% or more.

  The polylactic acid-based resin (C) has a melt flow rate (abbreviation: MFR, measurement condition: 230 ° C., 21.18 N) of 10 g / 10 min or more from the viewpoint of preventing streaks from occurring on the surface of the molded product and deteriorating the appearance. , 50 g / 10 min or less, preferably 20 g / 10 min or more and 50 g / 10 min or less.

  The polylactic acid-based resin (C) is a total content of the component (A), the component (B), the component (C) and the component (D) from the viewpoint of preventing the appearance defect of the molded body and the viewpoint of using the polylactic acid. 10 to 50 parts by mass, preferably 15 to 35 parts by mass in the resin composition of the present invention. The MFR of component (C) is measured under the conditions of a test load of 21.18 N and a test temperature of 230 ° C. by the method defined in JIS K7210 (1995).

[Ethylene Polymer Containing Epoxy Group (D)]
The ethylene-based polymer (D) containing an epoxy group used in the resin composition of the present invention has a monomer unit derived from a monomer having an epoxy group and a monomer unit derived from ethylene. It is a copolymer. 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 (D) containing an epoxy group is derived from another monomer in addition to a monomer unit derived from a monomer having an epoxy group and a monomer unit derived from ethylene. The monomer may have a monomer unit. Examples of the other monomer include unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, and butyl acrylate, vinyl acetate, and propion. Examples thereof include unsaturated vinyl esters such as vinyl acid.

  In the ethylene polymer (D) containing an epoxy group, the content of the monomer unit derived from the monomer having an epoxy group is preferably 0.01 to 30% by mass, and more preferably. Is 0.1 to 20% by mass. However, the content of all monomer units in the ethylene-based polymer having an epoxy group is 100% by mass. In addition, content of the monomer unit derived from the monomer which has an epoxy group is measured by an infrared method.

  The MFR of the ethylene polymer (D) containing an epoxy group is preferably 0.1 g / 10 min to 300 g / 10 min, more preferably 0.5 g / 10 min to 80 g / 10 min. The MFR of component (D) is measured under the conditions of a test load of 21.18 N and a test temperature of 190 ° C. by the method specified in JIS K7210 (1995).

  As a method for producing the ethylene-based polymer (D) containing an epoxy group, a known method is used. For example, by a high-pressure radical polymerization method, a solution polymerization method and an emulsion polymerization method, Examples thereof include a method of copolymerizing ethylene and another monomer as required, and a method of graft-polymerizing a monomer having an epoxy group to an ethylene polymer.

  From the viewpoint of stabilizing the production of the composition and homogenizing the foamed cells in the molded product, the ethylene-based polymer (D) containing an epoxy group is composed of component (A), component (B), component (C) and component ( When the total content of D) is 100 parts by mass, the resin composition of the present invention contains 1 to 10 parts by mass, preferably 3 to 8 parts by mass.

[Elastomers (E)]
The resin composition of the present invention may contain elastomers (E) (hereinafter also referred to as component (E)) from the viewpoint of imparting performance when impact resistance is required. Examples of the elastomers used in the resin composition of the present invention include natural rubber, polybutadiene rubber, polyisoprene rubber, butyl rubber, amorphous or low-crystalline ethylene elastomer, butadiene-styrene elastomer, butadiene-acrylonitrile elastomer, Examples include hydrogenated or non-hydrogenated styrene-conjugated diene block elastomers, polyester rubbers, acrylic rubbers, and silicone rubbers. As the elastomers, one type of elastomer may be used alone, or two or more types of elastomers may be used in combination. Among these, it is preferable to use an ethylene-based elastomer.

  The ethylene-based elastomer is an elastomer containing a monomer unit derived from ethylene, and examples thereof include an ethylene homopolymer, an ethylene-α-olefin copolymer, and an ethylene-unsaturated ester copolymer. Moreover, the copolymer of polyunsaturated compounds, such as a conjugated diene and a nonconjugated diene, and ethylene and an alpha olefin can also be mentioned as an example of an ethylene-type elastomer. As the elastomers, one type of ethylene elastomer may be used alone, or two or more types of ethylene elastomer may be used in combination. Such an ethylene-based elastomer is preferably an ethylene-α-olefin copolymer that is a copolymer of ethylene and one or more α-olefins. The α-olefin is preferably an α-olefin having 3 to 12 carbon atoms. Specifically, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 4-methyl-1-pentene, 4 -Methyl-1-hexene, vinylcyclohexane, vinylcyclohexene, styrene, norbornene, butadiene, isoprene and the like.

  In the present invention, the “amorphous elastomer” refers to an elastomer in which a crystal melting peak having a heat of fusion of 1 J / g or more is not observed within a range of −100 ° C. to 200 ° C. by differential scanning calorimetry (DSC). . The “low crystalline elastomer” refers to an elastomer in which a crystal melting peak having a heat of fusion of 1 to 30 J / g is observed in the range of −100 ° C. to 200 ° C. by differential scanning calorimetry (DSC).

  Elastomers (E) can be produced using a known polymerization method using a known olefin polymerization catalyst. For example, an ethylene-α-olefin copolymer is a solution polymerization method, slurry polymerization method, high pressure ion polymerization method and gas phase polymerization method using a Ziegler-Natta catalyst, a complex catalyst such as a metallocene complex or a nonmetallocene complex, Moreover, it is preferable to manufacture by the block polymerization method using a radical initiator, the solution polymerization method, etc. Among them, it is preferable to use a polymerization method using a Ziegler-Natta catalyst or a complex catalyst, and it is preferable to use a method of producing an ethylene-α-olefin copolymer in the presence of a metallocene catalyst.

  The content of the elastomers (E) is the total of the content of the polypropylene resin (A), the polypropylene single resin (B), the polylactic acid resin (C) and the ethylene polymer (D) containing an epoxy group. It is 30 mass parts or less normally with respect to 100 mass parts, Preferably it is 25 mass parts or less.

  The contents of the polypropylene resin (A), the polypropylene single resin (B), the polylactic acid resin (C) and the ethylene polymer (D) containing an epoxy group used in the resin composition of the present invention are as follows. The total content of the four components is 100 parts by mass, the content of polypropylene resin (A) is 40 to 88 parts by mass, the content of polypropylene single resin (B) is 1 to 30 parts by mass, polylactic acid resin The content of (C) is 10 to 50 parts by mass, and the content of the ethylene polymer (D) containing an epoxy group is 1 to 10 parts by mass. And from a viewpoint of productivity and foam moldability of the resin composition of this invention, it is preferable that content of polypropylene independent resin (B) is the range of 3-12 mass parts.

  The melt flow rate (abbreviation: MFR, measurement conditions: 230 ° C., 21.18 N) of the resin composition of the present invention is 10 g / 10 min or more and 100 g / 10 min or less from the viewpoints of moldability, appearance of molded products, and productivity. It is preferably 10 g / 10 min or more and 50 g / 10 min or less.

  As a manufacturing method of the resin composition of this invention, the method of melt-kneading component (A), (B), (C) and (D) is mentioned. The order of blending the components during melt-kneading is arbitrary. More preferably, there is a method in which the component (C) and the component (D) are kneaded in advance, and the components (A) and (B) are added to the kneaded product of the components (C) and (D) and kneaded. . The kneading temperature is preferably 170 to 240 ° C.

  In addition to the above components (A), (B), (C) and (D), the resin composition of the present invention may contain the elastomers (E), if necessary, as long as it is not contrary to the object of the present invention. Other additional components may be added. Examples of such additional components include antioxidants, processing stabilizers, weather resistance improvers, nucleating agents, flame retardants, plasticizers, lubricants, antistatic agents, colorants, organic fillers, and inorganic fillers. And other resins. The content of other additional components is the total content of the polypropylene resin (A), the polypropylene single resin (B), the polylactic acid resin (C), and the ethylene polymer (D) containing an epoxy group. It is 10 mass parts or less normally with respect to 100 mass parts, Preferably it is 7 mass parts or less.

  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 and carbon black.

  As an average particle diameter of inorganic fillers other than fibrous form, it is preferable that it is 0.01-500 micrometers, More preferably, it is 0.1-100 micrometers, Especially preferably, it is 0.1-20 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.

  The average fiber diameter of the fibrous inorganic filler is preferably 0.001 to 50 μm, more preferably 0.01 to 30 μm. The average fiber length in the composition is 0.01 to 10000 μm, preferably 0.1 to 1000 μm.

  The present invention also relates to a foam molded article (hereinafter, also referred to as a foam molded article of the present invention) made of the resin composition of the present invention. The foamed molded product of the present invention can be produced preferably by a foam molding method, more preferably by injection foam molding. In 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 for foaming the molten 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 to expand the foaming agent gas and foaming the molten resin composition filled in the cavity. . In addition, it is preferable that the injection amount of the molten resin composition 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 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 molding methods such as gas assist molding, melt core molding, insert molding, core back molding, and two-color molding. The shape of the foamed molded product of the present invention 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 260 ° C., preferably 170 ° C. to 220 ° C., and the cavity temperature is 0 ° C. to 100 ° C., preferably 5 ° C. to 80 ° C., more preferably. Is 20 ° C to 60 ° C.

  The back pressure during molding is 2 MPa to 15 MPa, preferably 5 MPa to 12 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 for foaming the molten resin composition filled in the cavity is not particularly limited, but 0 seconds to 10 seconds, preferably 0 seconds to 5 seconds after filling the cavity, and further Preferably after 0 second to 2 seconds.

  The foaming agent is preferably a physical foaming agent. As a physical foaming agent, at least any one from the group consisting of an inert gas and a volatile organic compound can be used. By using such a foaming agent, it is possible to provide a foamed molded article that is lightweight and excellent in mechanical strength. In addition, it is possible to prevent the mold after the foam molded body is manufactured from being contaminated.

  Examples of the inert gas include nitrogen, carbon dioxide, argon, neon, helium and oxygen. Volatile organic compounds include ethane, propane, butane, ethylene, propylene, petroleum ether, pentanes (n-pentane, 2,2-dimethylpropane, 1-pentene, cyclopentane, etc.), hexanes (n-hexane, 2 -Methylpentane, 3-methylpentane, 2,2-dimethylbutane, cyclohexane, etc.), heptanes (n-heptane, 2,2-dimethylheptane, 2,4-dimethylpentane, 3-ethylpentane, 1- Heptene, etc.), toluene, trichloromethane, tetrachloromethane, methanol, 2-propanol, isopropyl ether and methyl ethyl ketone. These may be used alone or in combination of two or more.

  Among the physical foaming agents, it is preferable to use an inert gas. The inert gas is preferably gaseous at normal temperature and normal pressure, which does not show reactivity with the target resin and does not cause deterioration of the resin. Of the inert gases, it is more preferable to use a supercritical inert gas. The supercritical inert gas has high solubility in the resin, and it is possible to uniformly diffuse the physical foaming agent in the resin in a short time, and has the effect of increasing the number of foamed cells generated. It is possible to obtain a foamed molded article having a fine foamed cell structure.

  The addition amount of the foaming agent varies depending on the expansion ratio of the foamed molded product, but the polypropylene-based resin (A), the polypropylene-only resin (B), the polylactic acid-based resin (C), and an ethylene-based polymer containing an epoxy group ( The total content of D) is 100 parts by mass to 0.3 part by mass, preferably 0.3 part by mass to 10 parts by mass, and more preferably 0.3 to 5 parts by mass. By setting it as such addition amount, it becomes possible to obtain the foaming molding which has a desired foaming ratio. Further, it is possible to obtain a foamed molded article that is lightweight and excellent in mechanical strength. Furthermore, it becomes possible to reduce the contamination of the mold after manufacturing the foam molded article.

  The foamed molded product obtained by the method as described above has two skin layers on the front and back sides and a foamed layer disposed between these skin layers. Since the foam (also referred to as a cell) shape of the foam layer is more uniform, the moldability and appearance are more preferable.

  The expansion ratio of the foamed molded product of 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 10 or less, and preferably 1.05 to 3 More preferably, it is double.

  The foam-molded article obtained using the resin composition of the present invention can be suitably used for applications such as automotive parts, household appliance parts, and other industrial products.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these Examples.

  The productivity, physical properties, and evaluation of the molded body of the resin composition were performed by the following methods.

(1) Evaluation of productivity The productivity was evaluated based on the take-up property of a rod-like strand in a molten state extruded from the die hole at the most downstream part of the kneader when the resin composition was produced by the kneader. When the resin composition is produced by extruding a melted rod-like strand with a kneader, the melted strand is cooled and solidified in cooling water in a cooling water tank and pelletized with a strand cutter installed on the downstream side. When this strand is taken up by a strand cutter, if the strand breaks, production will be hindered. When the strand was taken up, it was evaluated as “good” when it was stably taken up, and when it was difficult to take up due to surging (pulsation), it was evaluated as “difficult”.

(2) Melt flow rate (MFR, unit: g / 10 minutes)
According to JIS K7210, the test temperature was 190 ° C or 230 ° C and the test load was 21.18N.

(3) Intrinsic viscosity (unit: dl / g)
Using a Ubbelohde viscometer, reduced viscosities were measured at three concentrations of 0.1, 0.2 and 0.5 g / dl. Intrinsic viscosity is calculated according to the calculation method described in “Polymer Solution, Polymer Experiments 11” (published by Kyoritsu Shuppan Co., Ltd.), page 491. That is, the reduced viscosity is plotted against the concentration and extrapolated to zero. Obtained by extrapolation. Tetralin was used as a solvent as a solvent, and evaluation was performed at a temperature of 135 ° C.

(4) Foamability Observe the cross-section of the injection-molded foamed product with a microscope, visually determine the shape of the foamed cell, and whether the cell shape is “uniform”, “substantially uniform” or “non-uniform”. evaluated.

The materials used in the examples are as follows.
(A) Polypropylene resin (component (A))
Propylene-ethylene block copolymer (melt flow rate (measurement conditions: 230 ° C., 21.18 N) = 33 g / 10 min, content of propylene homopolymer component = 79% by mass, intrinsic viscosity of propylene homopolymer component = 1.06 dl / g, content of propylene-ethylene random copolymer component = 21 mass%, intrinsic viscosity of propylene-ethylene random copolymer component = 2.8 dl / g).
(B) Polypropylene single resin (component (B))
Melt flow rate (measurement conditions: 230 ° C., 21.18 N) = 10 g / 10 min, intrinsic viscosity = 6.3 dl / g (MFR (230 ° C., 21.18 N) = 0.01 g / 10 min) Contains 18% by mass of a blend and 82% by mass of a propylene homopolymer having an intrinsic viscosity of 1.17 dl / g.
(C) Polylactic acid resin (component (C))
“Terramac TE-2000” manufactured by Unitika Ltd. (melt flow rate (measurement condition: 230 ° C.) = 40 g / 10 min).
(D) Ethylene polymer containing an epoxy group (component (D))
“Bond First E” manufactured by Sumitomo Chemical Co., Ltd. (ethylene-glycidyl methacrylate copolymer, melt flow rate (measurement condition: 190 ° C.) = 3 g / 10 min, monomer unit content derived from glycidyl methacrylate = 12 mass%).
(E) Elastomers (component (E))
“Engage 8200” manufactured by Dow Chemical Co., Ltd. (ethylene-octene copolymer, melt flow rate (measured at 190 ° C.) = 4.9 g / 10 min).
(F) Additive “Sumilyzer GA-80” manufactured by Sumitomo Chemical Co., Ltd. (antioxidant)
"Sumilyzer GP" manufactured by Sumitomo Chemical Co., Ltd. (antioxidant)
“IRGAFOS168” (antioxidant) manufactured by BASF Corporation.
(G) Pigment master batch Black pigment master batch “SPEM8Y2382” manufactured by Sumika Color Co., Ltd.

[Example 1]
(Resin composition)
The resin composition according to the present invention was produced by the following method.
62.5 parts by mass of polypropylene resin (A), 6.25 parts by mass of polypropylene resin (B), 26.25 parts by mass of polylactic acid resin (C), and an ethylene polymer containing an epoxy group (D) With respect to 5.0 parts by mass and 100 parts by mass of components (A) to (D), 20 parts by mass of elastomer, 0.05 parts by mass of Sumilizer GA-80 as an additive, and Sumizer GP 0.1 parts by mass, 0.05 parts by mass of IRGAFOS 168, 4.0 parts by mass of pigment masterbatch, and kneaded and extruded under the conditions of 200 ° C. and 40 kg / hr using biaxial kneading ZSK32 manufactured by Coperion Co., Ltd. Manufactured.

(Injection molding)
After drying the resin composition in a hot air dryer at 90 ° C. for 3 hours, 3.75 parts by mass of Sankyo Kasei Co., Ltd. foaming agent Cell Microphone MB3064 is mixed with respect to 100 parts by mass in total of components (A) to (D) Using Engel's ES2550 / 400HL-MuCell type injection molding machine, injection molding is performed at a molding temperature of 200 ° C., a mold cooling temperature of 50 ° C. and an injection speed of 120 mm / sec. Backing was performed to obtain an injection foam molded article. The productivity and MFR (measurement temperature: 230 ° C.) of the resin composition and the foamability of the obtained injection-molded product were evaluated. The results are shown in Table 1.

[Example 2]
A polypropylene resin (A), a polypropylene single resin (B), a polylactic acid resin (C), and an ethylene polymer (D) containing an epoxy group are blended in the composition shown in Table 1. A resin composition and an injection-molded article were produced in the same procedure as in Example 1. The productivity and MFR of the resin composition and the foamability of the obtained injection-molded product were evaluated. The results are shown in Table 1.

[Comparative Example 1]
A polypropylene resin (A), a polypropylene single resin (B), a polylactic acid resin (C), and an ethylene polymer (D) containing an epoxy group are blended in the composition shown in Table 1. A resin composition and an injection-molded article were produced in the same procedure as in Example 1. The productivity and MFR of the resin composition and the foamability of the obtained injection-molded product were evaluated. The results are shown in Table 1.

[Comparative Example 2]
A polypropylene resin (A), a polypropylene single resin (B), a polylactic acid resin (C), and an ethylene polymer (D) containing an epoxy group are blended in the composition shown in Table 1. A resin composition and an injection-molded article were produced in the same procedure as in Example 1. The productivity and MFR of the resin composition and the foamability of the obtained injection-molded product were evaluated. The results are shown in Table 1.

  Since the resin composition of the present invention containing a polylactic acid-based resin is excellent in production stability and foamability at the time of injection molding, the resin composition of the present invention and the foamed molded product thereof are used for home appliances, automobile interior and exterior parts, etc. Can be used in the field.

Claims (3)

40 to 88 parts by mass of a polypropylene resin (A),
1-30 parts by mass of a polypropylene-only resin (B),
10 to 50 parts by mass of polylactic acid resin (C),
It contains 1 to 10 parts by mass of an ethylene-based polymer (D) containing an epoxy group, and the melt flow rate (measurement conditions: 230 ° C., 21.18 N) is 10 g / 10 min or more and 100 g / 10 min or less. Polylactic acid-containing propylene-based resin composition (however, the content of the polypropylene-based resin (A), the polypropylene-only resin (B), the polylactic acid-based resin (C), and the ethylene-based polymer (D) containing an epoxy group) The total is 100 parts by mass),
The polypropylene resin (A) is a propylene homopolymer having an intrinsic viscosity of 0.8 to 3.0 dl / g measured in a tetralin solvent at 135 ° C., or the intrinsic viscosity is 0.8 to More than 70% by mass of a 3.0 dl / g propylene homopolymer component and 95% by mass or less, and 5% by mass to less than 30% by mass of the propylene-ethylene random copolymer component having the intrinsic viscosity of 2-9 dl / g. A propylene-ethylene block copolymer consisting of
The polypropylene single resin (B) has a propylene homopolymer component of 3 to 30% by mass with an intrinsic viscosity of 5 to 10 dl / g measured in a tetralin solvent at 135 ° C., and the intrinsic viscosity of less than 5 dl / g. A propylene homopolymer containing 70 to 97% by mass of a propylene homopolymer component,
The polylactic acid resin (C) is a polylactic acid-containing propylene resin composition having a melt flow rate (measurement conditions: 230 ° C., 21.18 N) of 10 g / 10 min or more and 50 g / 10 min or less.   The polylactic acid-containing propylene-based resin composition according to claim 1, wherein the content of the polypropylene-only resin (B) is 3 to 12 parts by mass.   A foam molded article obtained by molding the polylactic acid-containing propylene resin composition according to claim 1 or 2.

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