JP2011000837A - Thermoplastic resin foam molding and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin foam molding which has an excellent external appearance and a uniform cell structure and the foaming cell of which has excellent minuteness.SOLUTION: A propylene-based resin composition includes (A) 40-99 mass% isotactic propylene polymer, (B) 1-60 mass% ethylene-α-olefin copolymer (on condition that the total of (A) the isotactic propylene polymer and (B) the ethylene-α-olefin copolymer is 100 mass%), (C) 0.1-20 parts mass syndyotactic propylene polymer based on 100 parts mass of the total of (A) the isotactic propylene polymer and (B) the ethylene-α-olefin copolymer and (D) 0.1-20 parts mass organic polymer bead based on 100 parts mass of the total of (A) the propylene polymer and (B) the ethylene-α-olefin copolymer. The thermoplastic resin foam molding is obtained by melting the propylene-based resin composition, dissolving carbon dioxide being a foaming agent in the molten propylene-based resin composition and foam-molding the carbon dioxide-dissolved propylene-based resin composition.

Description

  The present invention relates to a thermoplastic resin foam molded article and a method for producing the same.

Polypropylene is widely used in various molding fields because it is excellent in mechanical properties, chemical resistance, etc., and extremely useful in balance with economy.
As a means for obtaining a composition for obtaining a foamed molded product of polypropylene or a polypropylene molded foamed product, for example, a copolymer comprising propylene and α, ω-diene produced using a metallocene supported catalyst, the copolymer Discloses a polypropylene resin composition containing a foaming agent, a foam obtained by heating, melting, kneading, and foam-molding the composition, and a foam-molded body obtained by molding the foam (see Patent Document 1). ).
Furthermore, there is known a method of injection foam molding a thermoplastic resin containing an inert gas as a foaming agent and a composition containing polycarboxylic acid and hydrogen carbonate as a foam nucleating agent (see Patent Document 2).

JP 2001-316510 A JP 2002-264164 A

  However, the polypropylene resin composition disclosed in Patent Document 1 does not necessarily have sufficient foamability, and it is difficult to obtain a foam having a high expansion ratio or a foam having a dense foam cell structure. Further, in the molded product obtained by the method disclosed in Patent Document 2, silver streaks may occur on the surface of the molded product, and the appearance is not satisfied.

  In view of the above problems, an object of the present invention is to provide a thermoplastic resin foam molded article having excellent appearance, uniform cell structure, and excellent foam cell fineness.

  The present inventors have found that the above problems can be solved by adopting the following configuration, and have completed the present invention.

  That is, the present invention relates to 40 to 99% by mass of an isotactic propylene polymer (A) and 1 to 60% by mass of an ethylene-α-olefin copolymer (B) (however, the isotactic propylene polymer (A)). And the ethylene-α-olefin copolymer (B) are 100% by mass), the syndiotactic propylene polymer (C), the isotactic propylene polymer (A) and the ethylene-α-olefin. 1 to 20 parts by mass with respect to a total of 100 parts by mass of the copolymer (B), and the organic polymer beads (D) are mixed with the isotactic propylene polymer (A) and the ethylene-α-olefin copolymer (B ) And a propylene-based resin composition containing 0.1 to 20 parts by mass with respect to 100 parts by mass in total. There is provided a thermoplastic resin foam molded body characterized by being obtained by foam molding by dissolving carbon dioxide Te.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the thermoplastic resin foam molded object which was excellent in the external appearance, made the cell structure uniform, and was excellent in the fineness of the foam cell.

It is a figure which shows the perspective view of the thermoplastic resin foaming molding used in the Example.

The thermoplastic resin foam molded body (hereinafter referred to as foam) according to the present invention comprises an isotactic propylene polymer (A), an ethylene-α-olefin copolymer (B), and a syndiotactic propylene polymer ( It is obtained by dissolving a foaming agent in a propylene-based resin composition containing C) and organic polymer beads (D) and subjecting it to foam molding.
[Isotactic propylene polymer (A)]
The isotactic propylene polymer (A) used in the present invention has an isotactic pentad fraction measured by ¹³ C-NMR of 0.95 to 1.00, preferably 0.96 to 1.00. Propylene polymer.

Here, the isotactic pentad fraction is the fraction of propylene monomer units at the center of the isotactic chain in the pentad units in the propylene polymer molecular chain, in other words, five consecutive propylene monomer units. The fraction of propylene monomer units at the center of the meso-bonded chain. The method for measuring the isotactic pentad fraction is as follows. It is the method described by Zambelli et al., Macromolecules, 6, 925 (1973), that is, the method measured by ¹³ C-NMR. (However, the assignment of the NMR absorption peak was determined based on 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.

The isotactic propylene polymer (A) is preferably at least one selected from the group consisting of a propylene homopolymer (A-1) and a propylene-ethylene copolymer (A-2).
Examples of the propylene-ethylene copolymer (A-2) include a propylene-ethylene random copolymer (A-2-1) and a propylene-ethylene block copolymer (A-2-2). Here, the propylene-ethylene block copolymer (A-2-2) refers to a copolymer composed of a propylene homopolymer component and a propylene-ethylene random copolymer component.
Among the above (A-1) and (A-2), from the viewpoint of increasing the rigidity, heat resistance or hardness of the foam, the propylene homopolymer (A-1) or It is preferable to use a propylene-ethylene block copolymer (A-2-2).

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

In addition, the intrinsic viscosity ([η] _P ) of the propylene homopolymer (A-1) measured in a tetralin solvent at 135 ° C., the propylene homopolymer component of the block copolymer (A-2-2) The intrinsic viscosity ([η] _P ) measured in a tetralin solvent at 135 ° C., the intrinsic viscosity ([η]) of a random copolymer (A-2-1) measured in a tetralin solvent at 135 ° C. is It is 0.7-5 dl / g, Preferably it is 0.8-4 dl / g.

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

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

The intrinsic viscosity ([η] _EP ) measured in a tetralin solvent at 135 ° C. of the propylene-ethylene random copolymer component of the block copolymer (A-2-2) is 1.5 to 12 dl / g. Yes, preferably 2-8 dl / g, more preferably 3-8 dl / g.

  Content of the propylene-ethylene random copolymer component which comprises the said block copolymer (A-2-2) is 10-60 mass%, Preferably it is 10-40 mass%.

  The melt flow rate (MFR) of the propylene homopolymer (A-1) is 0.1 to 400 g / 10 minutes, preferably 1 to 300 g / 10 minutes. However, the measurement temperature is 230 ° C. and the load is 2.16 kg.

  The propylene-ethylene copolymer (A-2) has a melt flow rate (MFR) of 0.1 to 200 g / 10 minutes, preferably 5 to 150 g / 10 minutes. However, the measurement temperature is 230 ° C. and the load is 2.16 kg.

As a manufacturing method of the said isotactic propylene polymer (A), the method of manufacturing with a well-known polymerization method using a well-known polymerization catalyst is mentioned, for example.
Examples of the known polymerization catalyst used in the method for producing the isotactic propylene polymer (A) include (1) a solid catalyst component containing magnesium, titanium, halogen and an electron donor as essential components; And a catalyst system comprising an organoaluminum compound and (3) an electron donor component. Examples of the method for producing this catalyst include the production methods described in JP-A-1-319508, JP-A-7-216017 and JP-A-10-212319.

  Examples of the polymerization method used in the above production method include a bulk polymerization method, a solution polymerization method, a slurry polymerization method, and a gas phase polymerization method. These polymerization methods may be either batch type or continuous type, and these polymerization methods may be arbitrarily combined.

As a manufacturing method of said propylene-ethylene block copolymer (A-2-2), Preferably, it consists of said solid catalyst component (1), an organoaluminum compound (2), and an electron donor component (3). In the presence of a catalyst system, a polymerization tank comprising at least two tanks is arranged in series to produce a propylene homopolymer component of the propylene-ethylene block copolymer, and then the produced component is transferred to the next polymerization tank. In this polymerization tank, a propylene-ethylene random copolymer component is continuously produced to produce a propylene-ethylene block copolymer.
The amount of the solid catalyst component (1), the organoaluminum compound (2) and the electron donor component (3) used in the above production method and the method of supplying each catalyst component to the polymerization tank may be appropriately determined. .

  The polymerization temperature is -30 to 300 ° C, preferably 20 to 180 ° C. The polymerization pressure is normal pressure to 10 MPa, preferably 0.2 to 5 MPa. For example, hydrogen may be used as the molecular weight modifier.

  In the production of the isotactic propylene polymer (A), prepolymerization may be performed by a known method before carrying out the main polymerization. As a known prepolymerization method, for example, a method of supplying a small amount of propylene in the presence of the solid catalyst component (1) and the organoaluminum compound (2) and carrying out in a slurry state using a solvent can be mentioned.

[Ethylene-α-olefin copolymer (B)]
The propylene-based resin composition used in the present invention contains an ethylene-α-olefin copolymer (B).
Examples of the ethylene-α-olefin copolymer (B) used in the present invention include an ethylene-α-olefin random copolymer, an ethylene-α-olefin block copolymer, or a mixture thereof. These may be used alone or in combination of two or more. In the present invention, an ethylene-α-olefin random copolymer is preferred.

  The α-olefin used in the ethylene-α-olefin copolymer (B) is an α-olefin having 4 to 20 carbon atoms. For example, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-eicosene, etc. Is mentioned. These α-olefins may be used alone or in combination of two or more. The α-olefin is preferably an α-olefin having 4 to 12 carbon atoms such as 1-butene, 1-hexene, 1-octene, and more preferably 1-butene.

  The melt flow rate (190 ° C., 2.16 kg load) of the ethylene-α-olefin copolymer (B) is 1 to 50 g / 10 minutes, more preferably 10 to 40 g / 10 minutes, and still more preferably. 10-35 g / 10 min. Within the above numerical range, it is possible to obtain a foam having fine cells.

The density of the ethylene-α-olefin copolymer (B) is preferably 0.85 to 0.89 g / cm ³ , more preferably 0.85 to 0.88 g / cm ³ , and still more preferably 0. .86 to 0.88 g / cm ³ . Within the above numerical range, a propylene-based resin composition having excellent foam moldability can be obtained. Moreover, the foam excellent in uniformity and fineness can be obtained.
The content of ethylene contained in the ethylene-α-olefin copolymer (B) is preferably 40 to 90% by mass. The ethylene content can be determined by an infrared absorption spectrum method.

  As a method for producing the ethylene-α-olefin copolymer (B), a predetermined monomer is polymerized using a metallocene catalyst by a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, or the like. Is mentioned. Examples of the metallocene catalyst include, for example, Japanese Patent Laid-Open Nos. 3-163088, 4-268307, 9-12790, 9-87313, 11-80233, and special tables. Examples thereof include metallocene catalysts described in JP-A-10-508055. As a method for producing the ethylene-α-olefin copolymer (B) using a metallocene catalyst, a method described in EP-A-1211287 is preferable.

  As a content rate of the said isotactic propylene polymer (A) and an ethylene-alpha-olefin copolymer (B), an isotactic propylene polymer (A) is 40-99 mass%, Preferably, it is 60-95. It is 70 mass%, More preferably, it is 70-95 mass%. When content is less than 40 mass%, the rigidity of a molded object may fall. Moreover, when there is more content than 99 mass%, impact strength may fall. The content of the ethylene-α-olefin copolymer (B) is 1 to 60% by mass, preferably 5 to 40% by mass, more preferably 5 to 30% by mass (provided that (A) and ( The total amount of B) is 100% by mass).

[Syndiotactic propylene polymer (C)]
The propylene-based resin composition used in the present invention contains a syndiotactic propylene polymer (C). By containing the syndiotactic propylene polymer (C), it is possible to prevent appearance defects such as silver streak and corrugation from occurring during the production of the foam.

The propylene polymer in which the structure of the propylene polymer is a syndiotactic structure is 20.2 ppm based on tetramethylsilane in a ¹³ C-NMR spectrum measured with a 1,2,4-trichlorobenzene solution at 135 ° C. The value (syndiotactic pentad fraction [rrrr]) obtained by dividing the peak intensity observed in the above by the total peak intensity attributed to the methyl group of the propylene unit is preferably 0.3 to 0.9. It is a propylene resin, more preferably 0.5 to 0.9, and even more preferably 0.7 to 0.9. In addition, attribution of a necessary peak is A. It was carried out according to Zambelli et al, Macromolecules, 6, 925 (1973).

  The melt flow rate (MFR) of the syndiotactic propylene polymer (C) is preferably 0.1 to 200 g / 10 minutes, more preferably 5 to 150 g / 10 minutes, and further preferably 10 to 50 g / 10 minutes. It is. However, the measurement temperature is 230 ° C. and the load is 2.16 kg. Within the above numerical range, a propylene-based resin composition having excellent foam moldability can be obtained.

  The addition amount of the syndiotactic propylene polymer (C) is 1 to 20 parts by mass with respect to a total of 100 parts by mass of the propylene polymer (A) and the ethylene-α-olefin copolymer (B). It is preferably 2 to 15 parts by mass, more preferably 4 to 15 parts by mass. When the syndiotactic propylene polymer (C) is 1 part by mass or less, appearance defects such as silver streak and corrugation may occur during the production of the foam. Moreover, when it exceeds 20 mass parts, a foam with a low bending elastic modulus and impact strength may be obtained.

[Organic polymer beads (D)]
The propylene-based resin composition used in the present invention contains organic polymer beads (D).
The organic polymer beads (D) that can be used in the present invention are more preferably crosslinked organic polymer beads.
The organic polymer beads (D) can be obtained, for example, using a general emulsion polymerization method, dispersion polymerization method, suspension polymerization method, soap-free polymerization method, or seed polymerization method. Examples of monomer species that can be used for the polymerization of organic polymer beads include (meth) acrylic monomers and styrene monomers. (Meth) acrylic monomers include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate and other acrylic acid or ester derivatives of acrylic acid, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc. Mention may be made of methacrylic acid or ester derivatives of methacrylic acid. Styrene monomers include styrene derivatives such as styrene, methyl styrene, ethyl styrene, butyl styrene, and propyl styrene, and other monomers include polymerizable vinyl such as vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, and methacrylonitrile. Mention may be made of monomers. Of these monomers, it is preferable to use a (meth) acrylic monomer or a styrene monomer. These monomers may be used alone or in combination of two or more.

  In the polymerization of the organic polymer beads (D) that can be used in the present invention, it is preferable to use a crosslinking agent in combination. The crosslinking agent may be any radically polymerizable monomer containing two or more vinyl groups. Specific examples include divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate. . These crosslinking agents may be used alone or in combination of two or more.

Examples of organic polymer beads other than those described above include siloxane polymer beads having one or more organic groups. The siloxane polymer beads are generally called silicone rubber and silicone resin, and are solid at normal temperature.
Examples of the organic group include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an arylalkyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a hydrocarbon ring group.
Siloxane polymers are mainly produced by hydrolysis and condensation of organochlorosilanes.
For example, a siloxane-based polymer can be obtained by condensing organochlorosilanes represented by dimethyldichlorosilane, diphenyldichlorosilane, phenylmethylchlorosilane, methyltrichlorosilane, and phenyltrichlorosilane with hydrolysis.
These organochlorosilanes can be used individually by 1 type or in mixture of 2 or more types.

A siloxane polymer can also be obtained by hydrolysis and condensation of the organochlorosilanes and tetrachlorosilane.
Further, these siloxane-based polymers are converted to benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-chlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2, Crosslinked with a peroxide such as 5-di (t-butylperoxy) hexane, or by introducing a silanol group at the end of the siloxane polymer and condensation crosslinking with alkoxysilanes to form crosslinked siloxane polymer beads. Obtainable.
The organic polymer beads (D) that can be used in the present invention may be porous polymer beads.
Among these, the organic polymer beads (D) that can be used in the present invention are preferably cross-linked polymethyl methacrylate polymer beads, cross-linked siloxane polymer beads, or cross-linked polystyrene polymer beads. More preferred are methyl acrylate polymer beads or crosslinked siloxane-based polymer beads, and particularly preferred are crosslinked polymethyl methacrylate polymer beads.

  The content of the organic polymer beads (D) contained in the propylene resin composition used in the present invention is 100 parts by mass in total of the propylene polymer (A) and the ethylene-α-olefin copolymer (B). Is 0.1 to 20 parts by mass, preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 6 parts by mass. When the content is 0.1 parts by mass or less, a foam with a coarse and uneven cell structure may be obtained. Further, when the content is 20 parts by mass or more, the production cost may be increased, and the mechanical properties of the foam may be insufficient.

The weight average particle diameter of the organic polymer beads is preferably 0.1 to 20 μm, more preferably 0.1 to 10 μm, and still more preferably 0.1 to 6 μm. Examples of the shape of the polymer beads include a spherical shape, an elliptical shape, and a crushed shape.
The value measured by the Coulter counter method is used for the weight average particle diameter of the organic polymer beads in the present invention.

[Inorganic filler (E)]
The propylene-based resin composition according to the present invention may further contain an inorganic filler (E).
Examples of the inorganic filler (E) that can be used in the present invention include carbon fiber, metal fiber, glass bead, mica, calcium carbonate, potassium titanate whisker, talc, bentonite, smectite, mica, sepiolite, wollastonite, and allophane. , Imogolite, fibrous magnesium oxysulfate, barium sulfate, glass flakes, and the like. Talc and fibrous magnesium oxysulfate are preferable, and talc is more preferable. These inorganic fillers may be used alone or in combination of two or more.

  As an average particle diameter of an inorganic filler (E), Preferably it is 0.01-50 micrometers, More preferably, it is 0.1-30 micrometers, More preferably, it is 0.1-5 micrometers. Here, the average particle diameter of the inorganic filler (E) was determined from the integral distribution curve of the sieving method measured by suspending in a dispersion medium such as water or alcohol using a centrifugal sedimentation type particle size distribution measuring device. % Equivalent particle diameter D50.

  The inorganic filler (E) may be used as it is without treatment, in order to improve the interfacial adhesive strength with the resin composition, or to improve the dispersibility of the inorganic filler in the resin composition. The surface of the inorganic filler may be treated with various known silane coupling agents, titanium coupling agents, higher fatty acids, higher fatty acid esters, higher fatty acid amides, higher fatty acid salts or other surfactants.

  As content of an inorganic filler (E), Preferably it is 0.1-60 mass parts with respect to a total of 100 mass parts of the said propylene polymer (A) and the said ethylene-alpha-olefin copolymer (B). More preferably, it is 1-30 mass parts, More preferably, it is 1-10 mass parts.

〔Additive〕
You may add an additive to the propylene-type resin composition used for this invention as needed.
There is no restriction | limiting in particular as an additive which can be used for this invention, A well-known additive can be used. For example, neutralizers, antioxidants, light resistance agents, ultraviolet absorbers, copper damage inhibitors, lubricants, processing aids, plasticizers, dispersants, antiblocking agents, antistatic agents, nucleating agents, flame retardants, bubbles An inhibitor, a crosslinking agent, a coloring agent, a pigment, etc. are mentioned.

  The melt flow rate (measurement temperature is 230 ° C., load is 2.16 kg) of the propylene-based resin composition is preferably 40 to 200 g / 10 minutes, more preferably 40 to 150 g / 10 minutes, and still more preferably. 40-120 g / 10 min. When it is within the above range, fluidity is suitable, and appearance defects such as burrs are less likely to occur during foam molding.

  The method for producing the propylene-based resin composition used in the present invention includes a method of kneading each component, and examples of the apparatus used for kneading include a single screw extruder, a twin screw extruder, a Banbury mixer, a hot roll, and the like. It is done. The kneading temperature is 170 to 250 ° C., and the kneading time is 20 seconds to 20 minutes. Moreover, kneading | mixing of each component may be performed simultaneously and may be performed by dividing | segmenting. For example, it is preferable to include a step of weighing a predetermined amount of each component of the resin composition and uniformly premixing with a tumbler or the like, and a step of melt kneading the premixture.

[Method for producing thermoplastic resin foam molding]
The foam of the present invention is obtained through the following steps. The shape of the foam is not particularly limited, and may be any known shape.
Step (1): Step of dissolving carbon dioxide as a foaming agent in a molten propylene-based resin composition Step (2): The propylene-based resin composition in which the foaming agent is dissolved is formed with a pair of molds. Step (3): Step of cooling the propylene-based resin composition filled in the mold cavity Step (4): Step of filling the mold cavity Step of increasing the volume and foaming the propylene-based resin composition Step (5): Step of opening the mold and taking out the obtained foam

In the step (1), examples of the method for dissolving the foaming agent in the molten propylene resin composition include a method in which the foaming agent is injected into a nozzle or cylinder of an injection molding apparatus. A method of injecting the foaming agent into the cylinder is preferred because the molten propylene resin composition and the foaming agent are easily dissolved uniformly.
In addition to the above carbon dioxide, the blowing agent may be used in combination with an inert gas such as nitrogen, argon, neon or helium, or a physical blowing agent such as a volatile organic compound other than chlorofluorocarbon such as butane or pentane. The density | concentration of the carbon dioxide contained in the whole physical foaming agent when using a physical foaming agent together is 50 mass% or more, Preferably it is 70 mass% or more, More preferably, it is 80 mass% or more, More preferably, it is 90 mass% or more.

  Carbon dioxide is preferably in a supercritical state. Carbon dioxide in the supercritical state has high solubility in the resin, and can be uniformly diffused in the molten propylene resin composition in a short time, so the foaming ratio is high and foaming has a uniform foamed cell structure. You can get a body.

  In the step (2), the filling of the mold cavity with the propylene-based resin composition in which the foaming agent is dissolved is performed using a so-called injection molding method. The injection method of the propylene-based resin composition 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 propylene-based resin composition filled in the mold cavity is filled so as to have a volume equal to or less than the mold cavity volume. Thereby, generation | occurrence | production of appearance defects, such as a silver streak, at the time of manufacture of a foam can be suppressed.

As for the temperature conditions in the injection foam molding, the cylinder temperature of the injection molding machine is 150 to 300 ° C., preferably 180 to 270 ° C., more preferably 200 to 260 ° C., and the cavity temperature is 0 to 100 ° C., preferably 20 It is -80 degreeC, More preferably, it is 40-60 degreeC.
If the cylinder temperature is less than 150 ° C., it becomes difficult to fill the resin into the cavity and the appearance deteriorates, which is not preferable. If the cylinder temperature is higher than 300 ° C., the propylene-based resin composition deteriorates due to heat, Mechanical properties may be reduced.
If the mold temperature is less than 0 ° C, the filling property and appearance in the cavity may be deteriorated, and if it is 100 ° C or more, the cooling time of the foam may be too long.
The back pressure at the time of molding is 2 to 30 MPa, preferably 5 to 20 MPa. By setting the back pressure in such a range, it is possible to prevent the molten resin composition from foaming in the cylinder.

Further, the pressure in the mold cavity is not particularly limited, but is preferably not more than atmospheric pressure, more preferably less than atmospheric pressure. Therefore, you may further have the process of making the pressure in a metal mold cavity into atmospheric pressure or less after the said process (1). As a method of setting the pressure in the mold cavity to atmospheric pressure or lower, a method in which a vacuum-suckable mold is used as at least one mold and the cavity is vacuum-sucked in advance is exemplified. The pressure of the mold cavity is preferably kept at atmospheric pressure or lower even when the resin is filled.
Since a molten propylene resin composition containing a foaming agent is supplied to a mold cavity having a pressure lower than atmospheric pressure, gas does not enter between the molten propylene resin composition and the cavity wall surface. The resulting foam has a good appearance with no dents on the surface.

  In the step (3), the cooling temperature of the propylene resin composition filled in the mold cavity is not less than (crystallization temperature −15 ° C.) of the propylene polymer (A), and (crystallization temperature + 15 ° C.). The following is preferable. By setting it as such temperature, the foam which has a desired foaming magnification and has a fine cell can be obtained.

  In the step (4), as a method of increasing the volume of the mold cavity and foaming the propylene-based resin composition, for example, a method of expanding the entire cavity by retreating the mold cavity surface, a slide core is used. And a method of enlarging a part and / or the whole cavity.

  The shape of the foam obtained by the above steps (1) to (5) is not particularly limited, and may be any known shape. The foaming ratio of the foam is a value obtained by dividing the density of the resin composition by the density of the entire foam 1, and is preferably more than 1 and not more than 10 times, and is 1.5 to 5 times. More preferably, it is more preferably 2 to 4 times.

  The foam 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.

(1) Isotactic propylene polymer (A)
As the isotactic propylene polymer (A), a propylene-ethylene block copolymer (A) produced by a gas phase polymerization method using a solid catalyst component prepared by the following method was used.
Various physical properties of this propylene-ethylene block copolymer are as follows.
MFR: 80 g / 10 min Intrinsic viscosity [η] _{T of the} entire propylene-ethylene block copolymer: 1.4 dl / g
Intrinsic viscosity [η] _P of propylene homopolymer component: 0.8 dl / g
Mass ratio of propylene-ethylene random copolymer component to the entire propylene-ethylene block copolymer: 12% by mass
Intrinsic viscosity [η] of propylene-ethylene random copolymer component _EP : 7.0 dl / g
Ethylene unit content of propylene-ethylene random copolymer component: 32% by mass

The propylene-ethylene block copolymers used in the examples and comparative examples are disclosed in
It was produced by gas phase polymerization using a solid catalyst component for α-olefin polymerization described in JP-A-182876 and a solid catalyst component prepared according to the method for producing the solid catalyst component for α-olefin polymerization.

(2) Ethylene-α-olefin copolymer (B)
Ethylene-α-butene copolymer rubber Product name: CX5505 (manufactured by Sumitomo Chemical Co., Ltd.)
Density: 0.878 (g / cm ³ )
MFR (190 ° C., 2.16 kg load): 14 (g / 10 min)

(3) Syndiotactic propylene polymer (C)
Product name: FINAPLAS 1751 (manufactured by Atofina)
MFR (230 ° C., 2.16 kg load): 25 (g / 10 min)

(4) Organic polymer beads (D)
Cross-linked polymethacrylate methyl polymer beads Product name: Eposta MA1002 (Nippon Shokubai Co., Ltd.)
Particle size: 2.0 μm

(5) Organic peroxide Product name: Parkadox 14R-P (bis (t-butyldioxyisopropyl) benzene (made by Kayaku Akzo Co., Ltd.))

[Evaluation methods]
(1) Melt flow rate (MFR)
The 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 2.16 kg according to JIS K7210.
The ethylene-α-olefin copolymer (B) was measured under the conditions of a temperature of 190 ° C. and a load of 2.16 kg according to JIS K7210.

(2) Structural analysis of propylene-ethylene block copolymer (A) (2-1) Intrinsic viscosity of propylene-ethylene block copolymer (A) (2-1-a) Intrinsic viscosity of propylene homopolymer component: [Η] _P
Intrinsic viscosity of propylene homopolymer component: [η] _P is measured at the time of production, after the polymerization of propylene homopolymer, the propylene homopolymer is taken out from the polymerization tank, and [η] _P of the taken out propylene homopolymer is measured. And asked.

(2-1-b) Intrinsic viscosity of propylene-ethylene random copolymer component: [η] _EP
Intrinsic viscosity of propylene-ethylene random copolymer component: [η] _EP represents intrinsic viscosity of propylene homopolymer component: [η] _P and intrinsic viscosity of propylene-ethylene block copolymer as a whole: [η] _T It measured and calculated | required by calculation from following Formula using mass ratio: X with respect to the whole propylene-ethylene block copolymer component of a propylene-ethylene random copolymer component.
[Η] _EP = [η] _T / X− (1 / X−1) [η] _P
[Η] _P : Intrinsic viscosity (dl / g) of the propylene homopolymer portion
[Η] _T : Intrinsic viscosity of the entire propylene-ethylene block copolymer (dl / g)

(2-1-c) Mass ratio of propylene-ethylene random copolymer component in propylene-ethylene block copolymer: X
The mass ratio (X) of the propylene-ethylene random copolymer component to the entire propylene-ethylene block copolymer was determined by measuring the heat of crystal melting of the propylene homopolymer component and the entire propylene-ethylene block copolymer, respectively, It calculated | required by calculation using. The amount of crystal melting heat was measured by suggestive scanning thermal analysis (DSC).
X = 1− (ΔHf) T / (ΔHf) P
(ΔHf) T: Heat of fusion of the entire block copolymer (cal / g)
(ΔHf) P: heat of fusion of propylene homopolymer component (cal / g)

(3) Ethylene content of propylene-ethylene random copolymer component in propylene-ethylene block copolymer: (C2 ′) EP
Ethylene content of propylene-ethylene random copolymer component of propylene-ethylene block copolymer: (C2 ') EP is a measure of the ethylene content (C2') T of the entire propylene-ethylene block copolymer by infrared absorption spectroscopy. And obtained by calculation using the following equation.
(C2 ′) EP = (C2 ′) T / X
(C2 ′) T: Ethylene content (mass%) of the entire propylene-ethylene block copolymer
(C2 ′) EP: ethylene content (mass%) of propylene-ethylene random copolymer component
X: Mass ratio of propylene-ethylene random copolymer component to the entire propylene-ethylene block copolymer

(4) Appearance evaluation of foam (silver streak)
A range of a circle having a diameter of 60 mm shown in FIG. 1 (part where silver streak was evaluated) 2 shown in FIG. 1 at a part 100 mm away from the gate part 1 of the foamed body 3 made of a polypropylene resin composition obtained by foam molding is visually observed. Evaluated and determined as shown below.
○: Silver streaks on the surface of the foam cannot be confirmed by visual observation △: Silver streaks are slightly noticeable ×: Silver streaks are conspicuous

(5) Foaming ratio The foaming ratio of the foam is a value obtained by measuring the specific gravity with a specific gravity meter (Mirage Trading Co., Ltd., electronic specific gravity meter EW-200SG), and dividing the specific gravity of the unfoamed product by the specific gravity of the foam. It showed in.

(6) Cell Fineness and Cell Uniformity The foam was cut, the cross section was observed with a microscope (manufactured by SCARA, digital field microscope, DG-3), and the cell state was photographed. In the photographed foamed cross section, an arbitrary 500 μm square was selected in the vicinity of the skin layer and the center of the foamed layer, and the bubble diameter in each square was measured to calculate the average value. As a result, regarding the fineness of the cell, a cell having an average cell diameter of less than 200 μm was marked as “◯”, and a cell having an average cell diameter of 200 μm or more was marked as “X”. Concerning cell uniformity, a cell having a uniform and fine cell structure is marked with a circle, and a cell having a non-uniform cell size and shape due to unity and communication of cells x It was.

[Example 1]
Each component shown in Table 1 was weighed in a predetermined amount and uniformly premixed with a tumbler. Next, using a twin-screw kneading and extruding machine (Tex44SS 30BW-2V type manufactured by Nippon Steel Co., Ltd.), the extrusion amount is 30 to 50 kg / hr, the screw rotation speed is 300 rpm, and the kneading extrusion is performed under vent suction, and the propylene polymer composition pellets Manufactured.
Using this pellet, ES2550 / 400HL-MuCell manufactured by Engel Co., Ltd. (clamping force 400 tons) is used as an injection molding machine, and the mold part dimensions shown in FIG. 1 are 350 mm × 450 mm, height 105 mm, thickness 1 as a mold. Foam molding was carried out using a box shape of 0.5 mmt (gate structure: valve gate, see FIG. 1 for arrangement). As shown in Table 1, as the foaming agent, carbon dioxide in a supercritical state pressurized to 10 MPa is supplied into the cylinder of the injection molding machine and dissolved in a predetermined amount of the molten propylene-based resin composition. Injection was performed at 250 ° C. and a mold temperature of 50 ° C. so that the mold was fully filled. After 4.5 seconds from injection filling, the cavity wall surface of the mold was retreated by 2 mm to enlarge the cavity volume, and the propylene resin composition was foamed. The foamed resin was cooled and solidified to obtain a foam. Evaluation was performed at 150 mm from the gate A of the obtained foam (reference numeral 5 in the figure). The results are shown in Table 1.

[Comparative Example 1]
A foam was produced and evaluated in the same manner as in Example 1 except that nitrogen was used instead of carbon dioxide as the foaming agent.

[Comparative Examples 2 and 3]
A foam was produced and evaluated in the same manner as in Example 1 except that the composition of the propylene-based resin composition was changed as shown in Table 1.

1: Gate A contact part 2: Gate B contact part 3: Gate C contact part 4: Opening part 5: Part 150 mm away from the gate (part where the cross section of the foam was evaluated)
6: Foam

Claims (5)

Isotactic propylene polymer (A) 40-99 mass%,
1 to 60% by mass of ethylene-α-olefin copolymer (B) (however, the total of isotactic propylene polymer (A) and ethylene-α-olefin copolymer (B) is 100% by mass) When,
The syndiotactic propylene polymer (C) is 1 to 20 parts by mass with respect to a total of 100 parts by mass of the isotactic propylene polymer (A) and the ethylene-α-olefin copolymer (B), and
Propylene-based resin composition containing 0.1 to 20 parts by mass of organic polymer beads (D) with respect to a total of 100 parts by mass of the isotactic propylene polymer (A) and the ethylene-α-olefin copolymer (B). Melt the
A thermoplastic resin foam molded article obtained by dissolving and foaming carbon dioxide as a foaming agent in this molten propylene resin composition.   The thermoplastic resin foam molded article according to claim 1, wherein the organic polymer beads have a mass average particle diameter of 0.1 to 20 µm.   The thermoplastic resin foam molded article according to claim 1 or 2, wherein the carbon dioxide is in a supercritical state. It is a manufacturing method of the thermoplastic resin foam molded object in any one of Claims 1-3, Comprising: The manufacturing method of the thermoplastic resin foam molded object which has the following process.
Step (1): Step of dissolving carbon dioxide as a foaming agent in a molten propylene-based resin composition Step (2): The propylene-based resin composition in which the foaming agent is dissolved is formed with a pair of molds. Step (3): Step of cooling the propylene-based resin composition filled in the mold cavity Step (4): Step of filling the mold cavity Step of increasing the volume and foaming the propylene resin composition (5): opening the mold and taking out the obtained thermoplastic resin foam molded article   The manufacturing method of the thermoplastic resin foam molding of Claim 4 which further has the process of making the pressure in the said mold cavity into an atmospheric pressure or less after the said process (1).

Images