JP2000290444A - Inorganic fiber-containing polypropylene-based resin molding material, method for molding the same and molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject molding material capable of giving molded products which have excellent mechanical properties including flexural strength and flexural rigidity and appearance and are improved in weld strength and impact strength esp. falling ball impact strength irrespective of its apparent density, without substantially aggravating its injection moldability. SOLUTION: This molding material comprises (A) 30-99 wt.% of polypropylene-based resin pellets comprising a polypropylene-based resin and 10-90 wt.% of inorganic fibers each having a length of 3-100 mm nearly the same as that of each of the pellets and arranged in parallel to one another, (B) 1-50 wt.% of a flexible polypropylene-based resin having (1) a tensile modulus of 100-800 MPa and (2) a melting point of 140-170 deg.C, and (C) 0-69 wt.% of a polypropylene-based resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding material having excellent strength, rigidity and impact resistance, and more particularly to a polypropylene resin molding material capable of obtaining a molding product having a wide range of apparent density with improved impact strength. The present invention relates to a molding method and a molded article of an inorganic fiber-containing polypropylene resin molded article which can be applied to an industrial field such as an automobile part, a building material, and a civil engineering field using the molding material.

[0002]

2. Description of the Related Art Fiber-reinforced thermoplastic resin molded articles reinforced by containing inorganic fibers such as glass fibers have been known. This inorganic fiber reinforced thermoplastic resin molded product has excellent mechanical properties such as tensile strength, flexural strength, flexural modulus and heat resistance, so it can be used for instrument panel cores, bumper beams, door steps, roof racks, rear quarter panels. It is widely used as automobile parts such as air cleaner cases and the like, as well as building and civil engineering members such as panels for outer walls, panels for partition walls, concrete forms and the like. In producing such an inorganic fiber reinforced thermoplastic resin molded article, an injection molding method of injecting a molten resin containing fibers into a mold can be used. According to this injection molding method, it is possible to mold even a complicated shape, and since a predetermined molding cycle can be repeated continuously, there is an advantage that the same shape can be mass-produced.

In order to improve the strength and rigidity of an inorganic fiber reinforced thermoplastic resin molded article formed by injection molding, when the amount of inorganic fiber such as glass fiber is increased, the weight of the molded article is increased and the fiber weight is increased. Warpage deformation tends to increase due to anisotropy due to orientation. For this reason, in order to reduce the weight, a foam injection molding method has been proposed in which a foaming agent is mixed into a raw material and molding is performed while foaming a resin as a molded product (JP-A-7-247679). In this foam injection molding method, it is not easy to obtain a sufficient expansion ratio even if a considerable amount of a foaming agent is used to achieve weight reduction. Moreover, even if the expansion ratio is sufficiently obtained, the appearance is impaired, such as the occurrence of silver on the molded product,
Poor uniformity may not ensure sufficient performance. Further, it is difficult to apply the method to thin molded products, and the field of application is greatly restricted.

On the other hand, as a method for improving the bending strength, bending stiffness and impact resistance of glass fiber reinforced polyolefin resins, particularly polypropylene resin molded products, it is also known to use pellets having a long glass fiber length in the molding material. (For example, see JP-A-5-239286,
-259,753). For these, a suitable melt index of the polypropylene resin to be used, the use of a polypropylene resin modified with an unsaturated carboxylic acid or a derivative thereof, and the use of a highly crystalline resin as the polypropylene resin are suitable for strength and rigidity. It is disclosed.

[0005] Further, in a molded article using long fiber pellets in a state where these glass fibers are arranged in parallel with each other, the fiber is cut during melt-kneading in molding by injection molding or the like, and the final molded article has Fiber length may not be enough. Further, although the strength and rigidity are excellent, the impact resistance may not be sufficient. For this reason, Japanese Unexamined Patent Application Publication No.
No. 784, Japanese Unexamined Patent Publication No. 8-3396 and the like disclose blending an elastomer such as an ethylene-based elastomer and a styrene-based elastomer.

[0006] However, since a pellet containing long glass fibers is originally used as a molding material, the melt viscosity at the time of melt-kneading is high, and in addition, the blending of these elastomers further deteriorates the melt fluidity. I have. For this reason, it is extremely difficult to form large molded products and thin molded products. For this reason, it is difficult to maintain the glass fiber length in a molded product long by making use of the characteristics of the long fibers in the raw material pellets, and the field of application is limited.

The above-mentioned Japanese Patent Application Laid-Open No. 6-340784 discloses that an ethylene elastomer, a styrene elastomer and a specific inorganic filler are used together with a density of 1.0.
A compact of 10 g / cm ³ or less is described, and a lightweight compact is an object of the invention. However, as is clear from the examples, the density of the molded product is 1.03 to 1.10 g.
/ Cm ³ , which is much higher than the density of the polypropylene resin, and is far from the weight reduction desired from the market.

[0008] In order to solve these problems, international publication WO 97/97, in order to reduce the weight while maintaining mechanical properties such as strength, rigidity and impact resistance and appearance quality.
No. 29896 discloses a fiber-reinforced resin pellet containing relatively long fibers, in which a springback phenomenon is generated by the contained fibers, and the resin being molded is expanded by the springback phenomenon to obtain a lightweight molded product. A molding method is disclosed. According to this method, the weight of the molded article can be sufficiently reduced without impairing the mechanical properties, and it can be said that this method is effective for reducing the weight of the fiber-reinforced resin molded article.

According to the molding method disclosed in the above international publication, molding with a wide expansion ratio is possible, and excellent bending strength, flexural rigidity, and impact resistance are achieved despite weight reduction. Due to these characteristics, it has potential application in a wide range of fields. However, depending on the application,
There are fields where higher levels of impact resistance are required. In particular, in the case of parts such as automobiles, the conversion of materials from metal to resin is rapidly progressing from the viewpoint of energy saving and resource saving. In construction and civil engineering materials, there is a demand for resin-made lightweight materials in view of depletion of wood, improvement in durability and workability. Furthermore, recyclable thermoplastic resins are receiving attention due to social demands for resource saving and waste reduction.
For these thermoplastic resin materials, various physical properties have been improved by blending a polypropylene-based resin or an inorganic filler such as talc or rubber with the polypropylene-based resin mainly in consideration of recyclability. However, these materials are naturally limited in weight reduction in order to achieve both moldability and physical properties.

[0010]

DISCLOSURE OF THE INVENTION The present invention provides excellent mechanical properties, flexural strength and flexural rigidity of a molded product having an excellent appearance, without substantially lowering the injection moldability, regardless of the apparent density. It is an object of the present invention to provide a molded product having improved weld strength and impact strength, particularly, falling ball impact strength.

[0011]

Under these circumstances, the present inventors have conducted intensive studies on the relationship between weight reduction, moldability and physical properties of an inorganic fiber-containing polypropylene resin molded article. As a result, when a specific soft polypropylene-based resin is blended with a specific inorganic fiber-containing polypropylene-based resin pellet, unlike the case where a thermoplastic elastomer is blended, there is no decrease in injection moldability, impact strength, weld strength, especially The present inventors have found that the falling ball impact, which is close to practical physical properties, is greatly improved, and completed the present invention based on this finding.

That is, the present invention provides: (1) (A) a polypropylene resin, comprising 10 to 90% by weight of inorganic fibers arranged in parallel with each other and having substantially the same length as a pellet; 30-99% by weight of a certain inorganic fiber-containing polypropylene resin pellet, (B) (a) a flexural modulus of 100-800 MPa,
(B) An inorganic fiber-containing polypropylene resin molding material comprising 1 to 50% by weight of a soft polypropylene resin having a melting point of 140 to 170 ° C and (C) 0 to 69% by weight of a polypropylene resin. (2) The inorganic fiber-containing polypropylene resin molding material according to (1), wherein the polypropylene resin in the component (A) contains 0.01 to 10% by weight of a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof. . (3) The inorganic fiber-containing propylene-based resin molding material according to the above (1) or (2), wherein the inorganic fiber is a glass fiber. (4) A molding method in which the inorganic fiber-containing polypropylene-based resin molding material according to any one of (1) to (3) is melt-kneaded and injected or injected into a molding die cavity. (5) The polypropylene resin molding material containing an inorganic fiber according to any one of the above (1) to (3) is melt-kneaded, injected into a molding die cavity or compressed by injection, and then the volume of the molding cavity is increased. An expansion molding method for expanding. (6) The molding method according to (5), wherein a gas is injected into the molten resin after the expansion of the cavity volume of the molding die is started. (7) A molded article containing 10 to 60% by weight of an inorganic fiber having an average fiber length of 2 to 20 mm formed by the molding method according to any one of the above (4) to (7). (8) The molded article according to (7), wherein the apparent density is 0.2 to 1.0 g / cm ³ . (9) 40 to 90% by weight of a polypropylene resin and 10 to 60% by weight of inorganic fibers, the average fiber length of the inorganic fibers is 2 to 20 mm, and the apparent density is 0.2 to 1.2 g / cm.
^3. DuPont impact strength [load: 1 kg, strike core: 1/2 inch R, saucer: 50 mm diameter, starting height at which cracks occur on the back of the molded product. ] Is 30 cm or more.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, the inorganic fiber-containing polypropylene-based resin molding material is a molding material used for producing a molded article by various molding methods described later. That is, it is used particularly for general injection molding and injection compression molding. Particularly, it is used for an expansion molding method in which a molten resin is injected or filled into a fixed molding die cavity by injection compression or injection compression, and then the volume of the molding die cavity is enlarged, and the molten resin is expanded to reduce the weight. is there. Here, the polypropylene resin molding material containing an inorganic fiber of the present invention comprises the components (A), (B) and (C).

(A) Inorganic fiber-containing polypropylene resin pellets Inorganic fibers having a length of 3 to 100 mm, including 10 to 90% by weight of inorganic fibers arranged in parallel with the polypropylene resin and having substantially the same length as the pellets. Containing polypropylene resin pellets. That is, inorganic fibers equal to the length of the pellet are arranged in parallel,
Usually, it is manufactured by continuously drawing an inorganic fiber bundle in a molten resin and cutting it into a pellet of 3 to 100 mm, preferably 5 to 50 mm.

[0015] The polypropylene resin in the component (A) used in the present invention is not particularly limited.
Polypropylene, propylene and ethylene, butene-1,
Examples include propylene-based random copolymers with other olefins such as hexene-1, octene-1, propylene-based block copolymers, and mixtures thereof.

The polypropylene resin preferably contains a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof. Here, the modified polyolefin resin includes the above-mentioned polypropylene-based resin, polyethylene-based resin and the like, and is preferably a polypropylene-based resin. As the unsaturated carboxylic acid used for the modification, for example, acrylic acid, methacrylic acid,
Maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, sorbic acid, mesaconic acid, angelic acid, and the like. Derivatives thereof include acid anhydrides, esters, amides, imides, and metal salts. For example, maleic anhydride, itaconic anhydride, citraconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, monoethyl maleate, acrylamide, maleic monoamide, maleimide, N-butylmaleimide, acrylic acid Sodium and sodium methacrylate can be exemplified. Among these, unsaturated dicarboxylic acids and derivatives thereof are preferred, and maleic anhydride and fumaric acid are particularly preferred.

These unsaturated carboxylic acids and derivatives thereof may be used alone or in combination of two or more when modifying the polyolefin resin. The modification method is not particularly limited, and various conventionally known methods can be used. For example, a method of dissolving a polyolefin-based resin in an appropriate organic solvent, adding an unsaturated carboxylic acid or a derivative thereof and a radical generator, stirring and heating, or supplying the respective components to an extruder to perform graft copolymerization A method or the like can be used.

Here, as the acid-modified polyolefin resin, the amount of unsaturated carboxylic acid or its derivative added is 0.01%.
It is preferably in the range of 20 to 20% by weight, more preferably 0.02 to 10% by weight, and particularly preferably maleic anhydride-modified polypropylene. The acid-modified polyolefin resin is used in an amount of 0.01 to 10% by weight, preferably 0.0 to 10% by weight, based on the total amount of the polypropylene resin in the molding material of the present invention.
It is about 5 to 5% by weight.

The MI (melt index) of the polypropylene resin is not particularly limited, and MI [JIS
Based on K7210, temperature 230 ° C, load 2.16kg
At 5 to 1,000 g / 10 min, preferably 1 to 1,000 g / 10 min.
0 to 600 g / 10 minutes. Next, (A) of the present invention
The inorganic fiber used for the production of the inorganic fiber-containing polypropylene resin pellets is not particularly limited as long as it is an inorganic continuous fiber having high strength and rigidity, and glass fiber, carbon fiber,
Examples thereof include metal fibers such as silicon carbide fibers, stainless steel fibers, and copper fibers. In particular, glass fibers are preferably used. Examples of the glass fiber include E-glass, S-glass, and the like, the diameter of which is 3 to 30 μm, and preferably 6 to 25 μm.
m. In this case, the fiber diameter is 3μ
If it is less than 30 m, it becomes difficult to impregnate and handle the resin,
If it exceeds m, the appearance and physical properties of the molded product may be reduced. When compounding with a polypropylene-based resin, it is usually used in the form of a fiber bundle obtained by collecting a plurality of glass filaments, so-called glass fiber roving.

In the present invention, in order to improve the wettability and adhesion with the resin, the above glass fiber is used.
It may be previously treated with a surface treatment agent. Examples of the surface treating agent include silane-based, titanate-based, aluminum-based, chromium-based, zirconium-based, and borane-based coupling agents. Among these, silane-based coupling agents and titanate-based coupling agents are exemplified. Preferred are silane coupling agents.

Examples of the silane coupling agent include triethoxysilane, vinyl tris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, N-β- (aminoethyl) -γ
-Aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxy Silane, γ-chloropropyltrimethoxysilane and the like. Among them, γ-aminopropyltriethoxysilane, N-β-
Aminosilanes such as (aminoethyl) -γ-aminopropyltrimethoxysilane are preferred. The method for treating the glass fiber with the surface treatment agent is not particularly limited, and any method conventionally used, for example, an aqueous solution method, an organic solvent method, a spray method and the like can be used.

The production of the inorganic fiber-containing polypropylene resin pellets of the present invention will be described by taking glass fiber as an example.
As the glass fiber bundle, from 200 to 3000 glass fibers having a fiber diameter of 6 to 25 μm, from the viewpoints of resin impregnation, wettability and adhesion with the resin, mechanical properties of the obtained composite material, cost, and handleability. What has been surface-treated with an aminosilane-based coupling agent is preferably used. next,
The glass fiber bundle is guided into a die, brought into contact with a polypropylene resin supplied from an extruder, and then drawn out of the die. At this time, the glass fiber bundle can be treated with a liquid substance having a boiling point higher than the temperature of the molten resin in the die, such as liquid paraffin. The strands drawn from the dies are cooled, taken up by a take-up machine, cut into a length of 3 to 100 mm, preferably 5 to 50 mm by a cutter, and pelletized.

If the length of the pellet is less than 3 mm, the reinforcing effect of the molded product or the expandability in the expansion molding may not be sufficiently exhibited, and if it exceeds 100 mm, the bite is poor in supply to the melt-kneading molding machine. In some cases, it is difficult to stably produce a uniform molded product. The (A) inorganic resin-containing polypropylene-based resin pellets are not limited to cut polypropylene fiber-containing long fiber bundles in which the fiber bundle is formed into strands and the cross-sectional shape of which is substantially circular. By arranging, a sheet-shaped, tape-shaped or band-shaped resin-containing long fiber bundle may be cut into a predetermined length.

The content ratio of the fiber and the resin component in the inorganic resin-containing polypropylene resin pellet (A) of the present invention is such that the content of the inorganic fiber is 10 to 90% by weight and the content of the polypropylene resin is 90 to 10% by weight. . When the content of the inorganic fiber is less than 10% by weight, the amount of the fiber is insufficient, and it may be difficult to quantitatively extract the fiber. Since the amount of the resin is large, it is difficult to control the shape of the pellet. Also, 90
If the content is more than 10% by weight, it may be difficult to impregnate the resin,
Pellet cracks are likely to occur when the strand is cut, and it becomes difficult to control the shape of the pellet as the inorganic fibers fall off. From the viewpoint of resin impregnation and drawability, especially in the case of glass fiber, the glass fiber
0 to 85% by weight, and the content of the polypropylene resin is 80%.
It is preferably in the range of 〜15% by weight.

Next, the component (B) (a) has a flexural modulus of 1
100 to 800 MPa, (B) melting point of 140 ° C. to 170 ° C.
Is not particularly limited, and is a polypropylene resin containing a crystal part. Among them,
It is a homopolypropylene resin, a random polypropylene resin containing 4% by weight or less of other olefins such as ethylene or butene-1, or a polypropylene block copolymer composed of these polypropylene resins and an ethylene-propylene copolymer component.

That is, unlike a general polypropylene resin, it is a resin having a low flexural modulus, being soft, and having a high melting point as a polypropylene resin.
This is a special polypropylene resin different from those conventionally used for glass fiber reinforced polypropylene resins. Such a soft polypropylene-based resin is disclosed in, for example, JP-A-63-243106 and JP-A-63-243106.
JP-A-43107, JP-A-2-255707, JP-A-3-168234, JP-A-7-173223
For example, a polypropylene-based resin obtained by the production method described in Japanese Patent Application Laid-Open Publication No. H10-133, or a known syndiotactic polypropylene-based resin can be exemplified.

More specifically, (a) the flexural modulus is 100 to 800 MPa, and (b) the melting point is 140 to 170.
C., a soft polypropylene resin, preferably (a)
Flexural modulus 100-700MPa, (b) Melting point 15
It is a soft polypropylene resin having a temperature of 0 to 165 ° C.
That is, a propylene homopolymer, a copolymer of propylene and another olefin, or a mixture thereof can be exemplified. Specifically, (I) a propylene homopolymer and / or a copolymer containing 4% by weight or less of other olefin units may be used. ) Olefin units other than propylene 10 to 80
You may use the composition which consists of a propylene-type copolymer containing the weight%.

However, it is particularly preferable that the soft polypropylene-based resin (I) is the above-mentioned ((a) flexural modulus,
(B) In addition to the melting point, (c) rrrr / (1-mmmm) × 100 is 10 to 60 in pentad fraction by isotope carbon nuclear magnetic resonance spectrum ( ¹³ C-NMR).
%, (D) containing a propylene homopolymer having a melting enthalpy (ΔH) of 10 to 100 J / g as measured by a differential scanning calorimeter (DSC) and / or other olefin units of 4% by weight or less. 100 to 40% by weight of copolymer
And (II) olefin units other than propylene 10 to 80
0 to 60% by weight of a propylene copolymer containing 1% by weight
And a soft polypropylene resin comprising:

Hereinafter, desirable properties relating to the soft polypropylene resin as the component (B) in the present invention (a)
(D) will be described. First, the soft polypropylene resin has (a) a flexural modulus of 100 to 800 MPa,
Preferably it is 100 to 700 MPa. 100MPa
If less, the strength, rigidity and heat resistance may decrease,
If it exceeds 800 MPa, the effect of improving impact resistance and low-temperature impact resistance becomes insufficient. The flexural modulus is JIS-K7
This is a value obtained in accordance with 202. (B) a melting point of 140 to 170 ° C, preferably 150 to 1;
65 ° C. Here, the melting point is measured by a differential scanning calorimeter (D
SC) is the melting peak temperature (Tm) measured in SC). If the melting point is lower than 140 ° C., sufficient heat resistance cannot be obtained. This melting point is a value measured as a melting peak temperature in accordance with JIS K7121 by measuring using DSC-7 manufactured by Perkin-Elmer.

For the propylene homopolymer of the component (I) and the copolymer containing 4% by weight or less of other olefin units, (c) isotope carbon nuclear magnetic resonance spectrum ( ¹³ C-NMR) Rrrr / (1-mmmm) × 100 is 10 to 60
% Is desirable. If this value is less than 10%, the heat resistance is insufficient, and if it exceeds 60%, the flexibility is insufficient. From these aspects, preferred rrrr /
(1-mmmm) × 100 is in the range of 15 to 55%. Here, rrrr refers to a three-dimensional structure in which five methyl groups as side chains are alternately located in opposite directions to a main chain formed by carbon-carbon bonds composed of any five consecutive propylene units, or a ratio thereof. The mmmm means a three-dimensional structure in which all five methyl groups as side chains are located in the same direction with respect to a main chain formed by carbon-carbon bonds composed of any five consecutive propylene units, or a ratio thereof. Means

Incidentally, this rrrr / (1-mmmm) ×
100 is a value measured as follows. That is, using JNM-FX-200 (manufactured by JEOL Ltd., ¹³ C-nuclear resonance frequency 50.1 MHz), measurement mode: proton complete decoupling method, pulse width: 6.9 μs (45
°), pulse repetition time: 3 s, integration frequency: 1000
0 times, solvent: 1,2,4-trichlorobenzene / deuterated benzene (90/10% by volume), sample concentration 250 mg / 2.5
Under the conditions of milliliter solvent and measurement temperature: 130 ° C, ¹³
A C-NMR measurement was performed, and the difference in chemical shift due to the stereoregularity of the methyl group, that is, 22.5-1.
The pentad fraction was measured from the area intensity ratio of each peak of mmmm to mrrm appearing in the 9.5 ppm region, and rrr was measured.
The value of r / (1-mmmm) × 100 was determined.

Further, regarding the above component (I), (d)
The enthalpy of fusion (ΔH) measured by DSC is 10
Desirably, it is 100 J / g. ΔH is 100 J /
If it exceeds g, flexibility may be impaired, and the object of the present invention may not be achieved. This ΔH is usually 20 to 100 J /
g. Note that the ΔH is the value of Perkin-El.
The measurement was performed using DSC-7 manufactured by Mer Co., Ltd.
It is a value determined as the total heat energy absorbed during crystal melting according to −7122. The rate of temperature rise and fall in the measurement of the melting point and ΔH by DSC is 10 ° C./min.

The propylene homopolymer of the component (I) and the copolymer containing 4% by weight or less of other olefin units have a boiling n-heptane insoluble content of 40 to 95%.
Those in the range of weight% are preferred. If the boiling n-heptane insoluble content exceeds 95% by weight, flexibility may be impaired, and if it is less than 40% by weight, sufficient thermal properties may not be obtained. From the viewpoint of the balance between flexibility and heat resistance, a more preferable boiling n-heptane insoluble content is in the range of 45 to 93% by weight. In addition, boiling n-
The amount of heptane insolubles was determined using a Soxhlet extraction tester.
It is a value obtained by calculating from the amount of extraction residue after extraction with boiling n-heptane for 6 hours.

The soft polypropylene resin (B) of the present invention has a melt index (MI) of, for example, 0.1.
Desirably, it is in the range of 5 to 500 g / 10 minutes. If the MI is less than 0.5 g / 10 minutes, the melt-kneading properties of the component (A) with the inorganic fiber-containing polypropylene resin pellets are not sufficient, and if the MI exceeds 500 g / 10 minutes, the mechanical properties of the molded product obtained are May be insufficient. From the viewpoint of the balance between the moldability and the mechanical properties of the molded product, the more preferable MI is in the range of 2 to 300 g / 10 minutes. The MI is based on JIS K7210, and the load is 2.1.
It is a value measured under the conditions of 6 kg and a temperature of 230 ° C.

The soft polypropylene resin comprising the component (I) or the components (I) and (II) is, for example, a single-stage gas phase polymerization method, a single-stage slurry polymerization method, a multi-stage gas phase polymerization method, a multi-stage slurry polymerization method, or a blending method. And the like. For example, when produced by a polymerization method, a solid catalyst component composed of magnesium, titanium, a halogen atom and an electron donor, and a solid component composed of a crystalline polyolefin used as needed, an organic aluminum compound, In the presence of a catalyst system comprising an alkoxy group-containing aromatic compound or an alkyl aluminum aryloxide compound and an electron-donating compound used as necessary, homopolymerize propylene or copolymerize propylene with other olefins. It can be obtained by:

The soft polypropylene resin is prepared by adding a peroxide to a powder obtained by polymerization, decomposing it in an extruder to reduce the molecular weight, so that the melt viscosity can be appropriately controlled and the moldability can be easily processed. Become. Even if the resin is decomposed by this peroxide and the molecular weight is reduced, the resin only has good fluidity (increased MI) and hardly affects the pendad fraction, the melting peak temperature and the melting enthalpy described above. do not do. As the peroxide, for example, 2,5-dimethyl-2,5-di- (t-butylperoxy) -hexane, 1,3-bis- (t-butylperoxyisopropyl) benzene, or 2,5- Di-methyl-2,5-di-
It is advisable to mix (t-butylperoxy) hexyne-3 and the like, and to add an antioxidant, a stabilizer and a chlorine scavenger as required.

If desired, the soft polypropylene resin may contain other resins and various additive components such as various stabilizers, inorganic or organic fillers, antistatic agents, chlorine scavengers, antiblocking agents, antifogging agents, and the like. Organic flame retardants, flame retardant aids, dyes, pigments, natural oils, synthetic oils, waxes and the like can be blended. Here, the content of the soft polypropylene resin as the component (B) in the inorganic fiber-containing polypropylene resin molding material of the present invention is 1 to 50% by weight, preferably 3 to 40% by weight, particularly 5 to 30% by weight. It is. Here, if the content exceeds 50% by weight, heat resistance and rigidity may decrease, and if less than 1% by weight, impact resistance cannot be improved.

Next, the polypropylene resin as the component (C) is not particularly limited, and the same one as described above for the component (A) can be used. However,
The components (A) and (C) may have different molecular weights, different melt viscosities, that is, different melt indices (MI). Here, the polypropylene resin of the component (C) is usually in the form of pellets, but may be in the form of other unmelted beads or flakes. The content of the polypropylene resin of the component (C) is as follows:
It is optional for adjusting the amount of inorganic fibers in the molding material by dilution, or for adjusting physical properties and melt viscosity by mixing a resin, and is usually 0 to 69% by weight, preferably about 20 to 60% by weight. These have a relatively large inorganic fiber content of 50% by weight or more in the component (A), and the content of the inorganic fiber in the molding material is 10 to 60% by weight, preferably 15 to 60% by weight.
It is efficient to use it in the range of 50% by weight.

The polypropylene resin molding material of the present invention basically comprises the components (A) to (C). If necessary, other additive components may be added from the components (A) to (C). 10% by weight or less based on the resin component. For example, when the molding material of the present invention is used as an expansion molding material, the inorganic fibers in the component (A) are substantially melt-kneaded and expanded by the restoring force (spring back phenomenon) of the entanglement of the inorganic fibers. It is due to. However, to aid this swelling, especially the initial swelling, 0.01 to 3% by weight, preferably. 0.1 ~
It may contain as little as 1% by weight of a blowing agent.

Here, the type of the foaming agent is not limited as long as it generates gas by heat. For example, oxalic acid derivatives, azo compounds, hydrazine derivatives, semicarbazide, azide compounds, nitroso compounds, triazoles,
Urea and its related compounds, nitrite, hydride, carbonate, bicarbonate and the like can be employed. More specifically, azodicarbonamide (ADCA), benzenesulfohydrazide, N, N-dinitropentamethylenetetramine, terephthalazide and the like can be used. As the foaming agent, use not only these chemically decomposed foaming agents, but also physical foaming agents such as water, alcohol, propane, butane, a fluorine compound, and an organic solvent, as long as they generate gas when the resin is melted and heated. Can also. These blowing agents are usually used as a master batch (MB) which is melt-mixed at a high concentration in a thermoplastic resin such as a polyolefin resin.

As other additives, various stabilizers, antistatic agents, coloring agents, nucleating agents, peroxides and the like can be contained. In particular, it is desirable to include an antioxidant, a light stabilizer, and an ultraviolet absorber in consideration of long-term stable performance and recycling. As antioxidants, phenolic,
There are phosphorus-based and sulfur-based ones. These various additives are usually 500 to 8,000 ppm, preferably 1,000 to 3,000 ppm, and 50 parts by weight of the antioxidant, based on the polypropylene resin in the molding material.
0 to 10,000 ppm, preferably 1,000 to 6,
000 ppm, ultraviolet absorber 500 to 10,000, preferably 1,000 to 6,000 ppm. These additives are added, for example, as a master batch using a polyolefin resin.

Further, as other additives, inorganic fillers,
Aramid fiber, Kepler fiber, polyarylate fiber, and the like can be generally contained in an amount of 50 parts by weight or less based on 100 parts by weight of the components (A) to (C). Here, the inorganic filler is not particularly limited, and may be in the form of granules, plates, fibers, or whiskers.
For example, talc, mica, glass flakes, clay,
Calcium carbonate, magnesium carbonate, calcium sulfate,
Magnesium hydroxide, aluminum hydroxide, glass powder,
Diatomaceous earth, silica, alumina, zeolite, titanium oxide,
Short glass fibers, glass milled fibers, carbon fibers, titanium oxide fibers, magnesium sulfate fibers, potassium titanate fibers and the like can be mentioned. As these inorganic fillers, inorganic fillers having an aspect ratio of 3 or more are also preferably used. In addition, the inorganic filler is a coupling agent,
Those surface-treated with a surfactant, metal soap or the like can also be used.

In addition to the components (A) to (C), the polyolefin resin modified with the unsaturated carboxylic acid or a derivative thereof described above, various additives, Inorganic fillers and the like are used as needed. These other components are (A)
(B) and (C) components are used by being melt-mixed in advance,
Each of them can be used independently or two or more of them can be used as a master batch.

The polypropylene resin molding material containing an inorganic fiber of the present invention is used as a material for producing molded articles by various molding machines. The molding method is not particularly limited, such as injection molding, compression molding, and extrusion molding, but is preferably used for injection molding and injection compression molding. Among them, it is preferably used for injection expansion molding shown below, which is a molding of a lightweight molded product.

Hereinafter, the expansion molding method of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a conceptual cross-sectional view of a molding die part which is a main part of the expansion molding method. In FIG. 1, 1 is a fixed mold, 2 is a movable mold, 3 is a mold cavity, 4
Denotes a sprue, 5 denotes an injection resin, 6 denotes a gas injection pipe, and 7 denotes a gas exhaust pipe. As is clear from FIG. 1, in the expansion molding method of the present invention, it is necessary that the volume of the molding die cavity 3 can be changed. Usually, the thickness of the cavity in the mold opening / closing direction can be changed. That is, an injection molding device having a function of moving the movable mold 2 forward and backward is used. As the injection molding machine, a molding machine capable of generally performing injection compression molding, or an injection molding machine provided with a movable mold moving device in a general injection molding machine is used.

In the molding of the expansion molded article of the present invention, the movable mold 2 moves forward with respect to the fixed mold 1 in FIG. Is advanced to a position where the clearance becomes D1. Then, the inorganic (glass) fiber-containing expansion molding material is melt-kneaded and plasticized and measured by a screw device (not shown).
The molten resin 5 corresponding to the mold cavity clearance D2 is injected from the sprue 4 into the mold cavity 3. This D2 is the amount that fills and fills the entire molding die cavity by compression in the next step. here,
The melt-kneading of the inorganic (glass) fiber-containing expansion molding material
Apparatus and conditions for minimizing breakage of the glass fiber are preferable, and the compression ratio is usually 2.5 or less, preferably 2 or less.

When the molten resin containing the inorganic (glass) fiber is injected, the injection amount of the molten resin is usually not more than 2/3 of the cavity volume of the molding die at the time of injection of the molten resin, and the injection resin pressure is low. Low or substantially no fiber orientation. A few seconds after the start of the injection of the molten resin, the movable resin 2 is again advanced to the position indicated by the one-dot chain line, that is, the position where the molding die cavity clearance D2 is reached, so that the molten resin 5 is compressed into the molding die cavity. Fill completely. As a result, the surface of the molded article is cooled by the mold, and the mold surface is completely transferred even to minute irregularities. After the surface is cooled to some extent and the skin layer is formed, the movable mold 2 expands by retreating to the position of the molding die clearance D3, which is the thickness of the expansion molded product, and is cooled to form the expanded molded product. Then, by opening the movable mold 2, the expansion molded product is taken out.

FIG. 1 illustrates a case where the movable mold 2 leaves a movable clearance C with respect to the fixed mold 1 when the filling by compression is completed, but this clearance C is eliminated. You can also. However, in order to spread the molten resin evenly in the entire mold cavity in the compression step, it may be preferable that a certain level of specified pressure acts on the appearance of a molded product. In the compression step, besides controlling the mold cavity thickness, a molding method for controlling the compression force of the resin may be adopted. For example, in the case of integral molding of the skin material described later, the compression force can be controlled depending on the type of the skin material to prevent damage to the skin material.

The expansion molding method of the present invention is basically the above-mentioned method. However, nitrogen gas or the like can be injected from the gas injection pipe 6 after the movable mold 2 starts retreating. The injection of the gas assists the expansion by the glass fiber, and also presses the molded product against the surface of the mold after the expansion, thereby contributing to the improvement in mold transferability and appearance. Further, by controlling the pressure of the injected gas to a certain level as necessary and circulating the gas through the expansion molded product while exhausting the gas from the exhaust pipe, the cooling of the molded product can be promoted. This means that the expanded molded product that has been insulated due to the formation of voids can be cooled from the inside of the molded product by changing it to the inconvenience of having to be cooled by an external mold. It greatly contributes to improvement.
The injection gas is not particularly limited, but an inert gas such as a nitrogen gas or an argon gas is preferably used. The gas pressure is in the range of 0.01 to 20 MPa,
Preferably, it is selected in the range of 0.1 to 5 MPa.

The gas is usually a gas at room temperature, but a cooling gas having a temperature of 15 ° C. or lower, preferably 0 ° C. or lower can also be used. At this time, if a liquid such as volatile water is accompanied, the cooling effect is further improved. Further, the gas is opened to one of a gas nozzle provided inside a nozzle of an injection device for plasticizing and injecting the molten resin, or a sprue, a runner and a cavity provided inside the mold. It can be injected into the fiber-containing molten resin from a gas nozzle or a gas pin. Among these, it is preferable to inject from a gas pin provided in a mold, particularly from a gas pin opened in a cavity.

Although the above molding method is an example of a preferred molding method, the compression step can be omitted as an injection filling method of the molten resin depending on the shape and size of the molded product. However, as described above, it is preferable to use the injection compression molding method from the viewpoint of resin orientation, prevention of glass fiber orientation, ease of filling with molten resin, mold transferability, and the like. Further, in the expansion molding method of the present invention, a skin material for covering and integrating the surface of the molded product can be attached to the mold in advance before molding. As described above, by using a mold in which a skin material is mounted before molding, an expansion molded product whose surface is integrally covered with the skin material is obtained. Here, as the skin material, cloth such as woven fabric or nonwoven fabric, thermoplastic resin sheet, film, synthetic leather, thermoplastic resin foam sheet, and a single layer material such as a film on which a pattern or the like is printed, and, A multilayer material in which a backing material formed of a thermoplastic resin or a foamed sheet of a thermoplastic resin or the like is used as a skin material such as a thermoplastic elastomer or a vinyl chloride resin can be employed. The skin material can be entirely coated on the molded product or can be partially coated.

The molded article of the present invention is obtained by the above-mentioned molding method. These (expanded) molded products have a skin layer without voids on the surface, and are cooled under pressure, so that fine irregularities and patterns are faithfully transferred. The ribs, bosses, and the end of the molded product are faithfully formed. In addition, in the expansion molded product, the inorganic fiber and the polypropylene-based resin expand at the center portion, and usually continuous voids are formed. This gap can be arbitrarily controlled by the content of the inorganic fiber, the length of the inorganic fiber, the expansion ratio, and the like. Therefore, the expansion ratio is usually 1.0 to 6, preferably 1.5 to 5. Therefore, the apparent density of the obtained molded article is 0.2 to 1.3 g / cm ³ , and the molded article can have any apparent density from a substantially non-expanded range to a weight-reduced range of about ８. Goods. The content of the inorganic fiber in the molded product is 10 to 60% by weight, preferably 15 to 50% by weight.
%, And the average fiber diameter is 2 to 20 mm, preferably 3 to 15 mm.

Further, the composition and expansion ratio can be selected in consideration of the apparent density, strength, rigidity and impact resistance required for the application, based on the resin composition and expansion ratio. As the expansion molded product, a molded product having a plate or a plate-shaped portion as a main part is preferable. In the expansion molded product of the present invention, even when inorganic fibers having a high specific gravity are used, the molded product is reduced in weight by expansion and the apparent density is significantly reduced. In addition, since the apparent density is low and no thermoplastic elastomer is contained, a decrease in melt fluidity is suppressed. In addition, it has high bending strength, bending rigidity, and impact properties in a well-balanced manner. Moreover, there is a great feature in that a molded product having the same weight is evaluated as the surface density, that is, a molded product having excellent mechanical properties. This is due to the composite structure of the entanglement of the inorganic fibers and the continuous void structure between the surface and the intermediate portion, and is a conventional non-expanded glass fiber-containing light-weight molded article having an apparent density of 1 g / cm ³ or foamed by a foaming agent. A molded article is a completely different molded article. Therefore, depending on the selection of the apparent density, in addition to the mechanical properties, a heat insulating property, a sound insulating property, and a sound absorbing property can be obtained by performing a process of transmitting sound through the surface skin layer. Therefore, the (expanded) molded article of the present invention, in combination with its recyclability, is used as an interior material for automobiles,
It is expected to be used as an energy and resource saving material in various fields such as exterior materials, building materials, and civil engineering.

[0054]

EXAMPLES Next, the effects of the present invention will be described based on specific examples, but the present invention is not limited to these examples. Preparation of Flexible Polypropylene Resin (FPP) Preparation of Magnesium Compound A glass reactor equipped with a stirrer having an internal volume of about 5 liters was sufficiently replaced with nitrogen gas, and then ethanol was added to about 2,43.
0 g, 16 g of iodine and 160 g of metallic magnesium were charged and heated with stirring, and reacted under reflux conditions until hydrogen gas was not generated from the inside of the system to obtain a solid reaction product. The reaction solution containing the solid reaction product was dried under reduced pressure to obtain a magnesium compound.

Preparation of Solid Catalyst Component (W) 160 g of the magnesium compound (not pulverized) obtained above, 800 ml of purified heptane, were placed in a glass reactor having an internal volume of 5 liter which was sufficiently substituted with nitrogen gas. After charging 24 ml of silicon tetrachloride and 23 ml of diethyl phthalate, maintaining the inside of the system at 80 ° C., adding 770 ml of titanium tetrachloride with stirring, and reacting at 110 ° C. for 2 hours, the solid component was separated to 90 parts. Washed with purified heptane at ℃. Further, after adding 1,220 ml of titanium tetrachloride and reacting at 110 ° C. for 2 hours, it was sufficiently washed with purified heptane to obtain a solid catalyst component (W).

Then, 2.3 liters of purified heptane was charged into a 5 liter reaction vessel equipped with a stirrer, and 250 g of the solid catalyst component and 12 g of triethylaluminum were added.
g, cyclohexylmethyldimethoxysilane at a rate of 5 g. Thereafter, propylene was introduced until the partial pressure of propylene reached 0.3 kg / cm ² G, and the reaction was carried out at 25 ° C. for 4 hours. After the completion of the reaction, the solid catalyst component was washed several times with purified heptane, further supplied with carbon dioxide, and stirred for 24 hours.

Gas phase polymerization In a polymerization tank having an internal volume of 200 liters, 6.0 g / h of the solid catalyst component prepared above, 0.15 mol / h of triisobutylaluminum (TIBA), 1-allyl-
3,4-dimethoxybenzene (ADMB) 0.0042
Mol / h, cyclohexylmethyldimethoxysilane (CHMDMS) 0.012 mol / h, propylene 4
The solution was fed at a rate of 3 kg / hour, and polymerization was performed at 70 ° C. and 28 kg / cm ² G. The production amount of the polymer was 30 kg / hour.

The intrinsic viscosity [η] (at 135 ° C. in decalin) of the polymer obtained by this polymerization was 4.6 deciliter / g. Further, the amount of the boiling n-heptane insoluble component of the polymer was 91.5% by weight, [η] of the boiling n-heptane insoluble component was 4.87 dL / g, and the boiling n-heptane soluble component was [η]. ] Was 1.70 deciliter / g.

On the other hand, the ¹³ C-NMR spectrum of the homopolymer (mmmm: 0.749, rrrr: 0.05
Pentad fraction rrrr / (1-mm) calculated from 3)
mm) × 100 was 21.1%, the melting point (melting peak temperature) measured by DSC was 160.0 ° C., and the enthalpy of fusion (ΔH) was 74.5 J / g. In addition, no reversal bond was found for the head-to-tail bond of peropyrene.

2,5-dimethyl-
2,5-di- (t-butylperoxy) -hexane was mixed, and further added with an antioxidant, a stabilizer, and a chlorine scavenger, mixed and extruded with a 40 mmφ extruder.
Melt index (MI, 230 ° C, 2.16 kg
f) obtained a pellet of 10 g / 10 min. The above polymer was decomposed with peroxide to reduce the molecular weight. However, even with the reduced molecular weight polymer, the above-mentioned pendant fraction, melting peak temperature and melting enthalpy did not change. From the pellets, 3 mm thick by press molding
Was cut out from the sheet, and a strip test piece having a width of 10 mm was cut out and subjected to a bending test in accordance with JIS K7203. The flexural modulus was 600 MPa.

Example 1 Glass fiber-containing polypropylene resin pellets in which glass fibers (13 μm) are arranged in parallel, whose content is 60% by weight, and whose length is 8 mm (5% by weight of polypropylene modified with maleic anhydride) Content) [tensile elastic modulus = 1,80
0 MPa, melting point (Tm) = 166 ° C.] 60% by weight and 40% by weight of a soft polypropylene-based resin [FPP] were dry-blended to obtain molding materials.

The injection molding machine used a screw having a mold clamping force of 450 t and a compression ratio of 1.9 in order to minimize breakage of the glass fiber. The molding die is 400mm x 200m
A mold for molding a plate-like molded product having a variable mx thickness (two gates at the center of 1/2) was used. IP for moving the movable mold forward and backward so that the volume of the mold cavity can be changed
This is an injection molding apparatus having a mold structure equipped with an M unit (made by Idemitsu Petrochemical Co., Ltd.). The mold was provided with a facility for injecting and exhausting nitrogen gas into the cavity.

After the molding material was melt-kneaded and plasticized and measured, the thickness of the molding die cavity was set to D1 (2 mm), and a molten resin corresponding to the molding die cavity thickness and D2 (1 mm) was injected. After the start of the injection, the movable mold is advanced, compressed until it corresponds to the mold cavity thickness D2 (1 mm), and the molten resin (resin temperature: 250 ° C.) is filled in the mold cavity (mold temperature: 40 ° C.). . End of compression 2
After 2 seconds, the movable mold is moved to a mold cavity thickness of D3 (3 m).
m) and retracted to expand. Die retreat start 2
Seconds later, a 2 MPa nitrogen gas was injected into the resin from a gas pin. Thereafter, it was cooled and solidified for 40 seconds, and after evacuation of the gas, the mold was opened to obtain a plate-like expansion molded product. The plate-like expanded molded product had no large hollow inside, expanded about three times, and had a good appearance having a skin layer without generation of sink marks and silver. Table 1 shows the evaluation results of the molded articles.

The evaluation method is shown below. Glass fiber content: The weight was measured after incineration of the test piece. Average glass fiber length: After the test piece was incinerated, it was directly photographed at a magnification of 10 times with a universal projector, and the average glass fiber length was determined with a digitizer using the image. Apparent density (g / cm ³ ): molded article weight (g) / volume of molded article (cm ³ ) Area density (g / cm ² ): molded article weight (g) / projected area of molded article (cm ² ) Bending Test method: 160mm x 50mm x from molded product
A test piece for bending test having a thickness was cut out and subjected to a three-point bending test with a fulcrum distance of 80 mm at a test speed of 10 mm / min at room temperature (23 ° C.). DuPont impact strength: Load = 1 kg, hammer = 1/2 inch R, pan = 50 mm diameter, and the starting height at which cracks occurred on the back surface of the molded product was determined. Weld strength: The maximum load in a bending test centered on the weld.

Comparative Example 1 In Example 1, a soft polypropylene resin [FPP] was used.
Instead of 40% by weight, a polypropylene resin [tensile elastic modulus = 1800 MPa, melting point (Tm) = 166 ° C., MI
(280 ° C., 2.16 kg load) = 150 g / 10 min]
An expansion molded product was obtained in the same manner as in Example 1 except that 40% by weight was used. The plate-like expanded molded product had no large hollow inside, expanded about three times, and had a good appearance having a skin layer without generation of sink marks and silver. Table 1 shows the evaluation results.

Comparative Example 2 In Example 1, a soft polypropylene resin [FPP] was used.
Instead of 40% by weight, an ethylene / propylene elastomer [ethylene content = 24% by weight, Mooney viscosity = 2
3 (ML _{1 + 4} 100)] An expansion molded product was obtained in the same manner as in Example 1 except that 40% by weight was used. However, the melt fluidity was poor, and it was difficult to fill the mold cavity, and a molded product could not be obtained.

Comparative Example 3 In Example 1, 65% by weight of a soft polypropylene resin [FPP] and glass fiber chopped strand (fiber diameter: 13 μm, fiber length: 3 mm) were used as molding materials.
A molded product was molded in the same manner as in Example 1 except that a pellet obtained by melting and kneading the mixture in an extruder at a percentage of weight% was used, except that nitrogen gas was not injected. The average glass fiber length in the pellet was 0.43 mm. The molded product did not expand and the surface sink was remarkable. Table 1 shows the evaluation results.

[0068]

[Table 1]

[0069]

The polypropylene resin molding material containing an inorganic fiber of the present invention can provide a molded article excellent in impact strength, particularly DuPont impact strength which is practically important, while minimizing the decrease in product rigidity. Particularly, as a molding method, a lightweight molded product obtained by expanding and molding a resin in a molding die cavity to an expansion ratio of 1.5 times or more has excellent physical properties. In addition, compared with the improvement of impact resistance by the addition of a general thermoplastic elastomer, it is excellent in melt fluidity and molding of a thin molded product becomes easy. In the case of a thermoplastic elastomer, the weld strength tends to decrease, but when the soft resin of the present invention is used, a high weld strength is exhibited, which is suitable for molding a large molded product or complicated molding. Furthermore, since it is soft and has a high melting point, the heat resistance of the molded article substantially conforms to that of a homopolypropylene resin.
In addition, since the melt viscosity can be reduced, for example, in the case of an expansion molded product obtained by expansion molding, a lightweight molded product having good mold transferability and good appearance can be obtained. Although the expanded molded article has a low apparent density, excellent strength and rigidity can be obtained, and these properties are substantially maintained, thereby significantly improving impact resistance. Therefore, it is possible to contribute to weight reduction of automobile parts and building materials, and also to resource and energy saving.

[Brief description of the drawings]

FIG. 1 shows a conceptual cross-sectional view of a molding die part which is a main part of the expansion molding method of the present invention.

[Explanation of symbols]

 1: fixed mold 2: movable mold 3: molding mold cavity 4: sprue 5: injection molten resin 6: gas injection pipe 7: gas discharge pipe

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 23/26 C08L 23/26 // B29K 23:00 105: 12 F term (reference) 4F202 AA03 AA11 AA20 AB25 AH17 AH43 AH46 AM32 CA11 CB01 CK06 CK19 4F206 AA03 AA11 AA20 AB25 AE10 AH17 AH24 AH43 AM32 AP01 JA03 JF01 JF02 JF06 JF21 JL03 JN01 JP13 JP30 JQ81 JW50 4J002 BB121 BB211 DL006 FA046 GL00 GN00

Claims (9)

[Claims] (A) a polypropylene-based resin and 10 to 9 which are arranged in parallel with each other and have substantially the same length as a pellet.
Inorganic fiber-containing polypropylene resin pellets 30 to 9 containing 0% by weight of inorganic fibers and having a length of 3 to 100 mm
9% by weight, (B) (a) Flexural modulus is 100 to 800M
Pa, (b) An inorganic fiber-containing polypropylene resin molding material comprising 1 to 50% by weight of a soft polypropylene resin having a melting point of 140 to 170 ° C and (C) 0 to 69% by weight of a polypropylene resin. 2. The polypropylene resin in component (A) contains 0.01 to 10% by weight of a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof.
An inorganic fiber-containing polypropylene resin molding material as described in the above. 3. The method according to claim 1, wherein the inorganic fibers are glass fibers.
Or the inorganic fiber-containing polypropylene resin molding material according to 2. 4. A molding method comprising melt-kneading the inorganic fiber-containing polypropylene resin molding material according to claim 1 and injecting or injecting it into a molding die cavity. 5. The inorganic fiber-containing polypropylene resin molding material according to any one of claims 1 to 3, which is melt-kneaded and injected or injected into a molding die cavity and then expanded by expanding the cavity volume of the molding die. Expansion molding method. 6. The molding method according to claim 5, wherein a gas is injected into the molten resin after the expansion of the cavity volume of the molding die is started. 7. A molded product containing 10 to 60% by weight of an inorganic fiber having an average fiber length of 2 to 20 mm, which is molded by the molding method according to any one of claims 4 to 7. 8. An apparent density of 0.2 to 1.0 g / cm ^3.
The molded article according to claim 7, which is: 9. Polypropylene resin 40 to 90% by weight
And 10 to 60% by weight of inorganic fibers, the average fiber length of the inorganic fibers is 2 to 20 mm, and the apparent density is 0.2 to 1.2 g.
/ Cm ³ , DuPont impact strength [Load: 1kg, Hammering core: 1
/ 2 inch R, saucer: 50 mm diameter, starting height at which cracks occur on the back of the molded product. ] Is 30 cm or more.