JP2003183460A - Polypropylene resin composition for injection molding, polypropylene resin molded article and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene resin composition suitable for manufacturing an injection molded article which hardly suffers from generation of flow marks and is excellent in rigidity, impact resistance and surface hardness. <P>SOLUTION: The resin composition has a converted shear rate, represented by the product (τ×R<SP>2</SP>) of a relaxation time (τ: unit s) of the resin composition at the temperature of injection molding and a shear rate (R<SP>2</SP>: unit s<SP>-1</SP>) of the resin composition in a mold, of at most 50 or at least 100. As a concrete example of resin compositions having such characteristics, there can be exemplified a composition comprising (A) 50-99 wt.% of a polypropylene resin, (B) 0-50 wt.% of an elastomer and (C) 0-30 wt.% of an inorganic filler, the total amount of (B) and (C) being 1-50 wt.%. Preferably, (A) is a propylene/α-olefin block copolymer and (B) is an olefinic thermoplastic elastomer or a styrenic thermoplastic elastomer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene resin composition for injection molding, which is suitable for producing a molded product with less appearance of flow marks and a good appearance, a polypropylene resin molded product produced from the same, and a method for producing the same. .

[0002]

BACKGROUND OF THE INVENTION Polypropylene resin has a relatively high melting point among general-purpose resins, so it has heat resistance, high rigidity, and is light in weight.
It is used in a wide range of industrial fields such as electrical parts, daily necessities, and packaging materials.

In order to improve the physical properties of the polypropylene resin, attempts have been made to blend the polypropylene resin with an inorganic filler such as an ethylene / propylene copolymer or talc. For example, such a composition is disclosed in JP-A-55 / 55
-21494, JP-A-57-55952, JP-A-5
7-159841, JP-A-57-177038, JP-A-57-195134, and JP-A-57-207630.
JP-A-58-111846, JP-A-58-171
No. 39 and JP-A-59-98157, neither of them has sufficient fluidity or the surface hardness of the molded articles obtained therefrom is not good.

Therefore, the polypropylene resin itself is modified, or the ethylene resin specific to the polypropylene resin is used.
Taking means such as blending an α-olefin copolymer,
A method for improving molding workability and surface hardness is disclosed in JP-A-60
-13838, JP-A-5-59251, JP-A-5-
98093 and JP-A-5-98098.

On the other hand, a flow mark may appear in a molded product obtained by injection molding a polypropylene resin composition, which is one of the causes of poor appearance. It is generally known to use a material having a large die swell as a method for preventing flow marks. Therefore, measures such as broadening the molecular weight distribution of the polypropylene resin, increasing the amount of the high molecular weight component, or increasing the intrinsic viscosity [η] of the rubber component in the propylene block copolymer are taken. However, the generation of flow marks may still be observed, and further improvement is desired.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention provides a polypropylene resin composition which has few flow marks and is suitable for the production of an injection-molded article excellent in heat resistance, rigidity and surface hardness and has a good moldability. For the purpose of provision. Another object of the present invention is to provide a polypropylene resin molded article produced from such a resin composition and a method for producing the same.

[0007]

That is, according to the present invention, the relaxation time (τ: unit s) of the resin composition at the injection molding temperature and the shear rate (R ² : unit s) of the resin composition in the mold are described.
⁻¹ ) and a reduced shear rate (R ¹ ) represented by the product (τ × R ² ) of 50 or less or 100 or more.

As an example of a concrete resin composition showing such a converted shear rate (R ¹ ), a composition comprising (A) polypropylene resin, (B) elastomer and (C) inorganic filler is mentioned. You can More specifically,
(A) polypropylene resin 50 to 99% by weight, (B) elastomer 0 to 50% by weight, and (C) inorganic filler 0
It is possible to cite a composition composed of 1 to 50% by weight and a total amount of (B) and (C) of 1 to 50% by weight.

The preferred (A) polypropylene resin has a melt flow rate of 1 to 150 (g / 10).
Min) and propylene homopolymer component 70 to 9
7% by weight and 3 to 30% by weight of a random copolymer component of propylene having an intrinsic viscosity [η] of 2 to 10 (dl / g) and other α-olefin having 2 to 20 carbon atoms. A propylene / α-olefin block copolymer can be used.

The (B) elastomer is preferably an olefin-based thermoplastic elastomer or a styrene-based thermoplastic elastomer, and particularly contains 30 to 9 ethylene constitutional units.
An ethylene / α-olefin copolymer containing 0% by weight and 10 to 70% by weight of an α-olefin structural unit having 3 to 20 carbon atoms is preferable. Further, as the inorganic filler, talc or calcium carbonate is preferable.

The present invention also relates to a polypropylene resin molded article formed by injection molding the above polypropylene resin composition.

Further, the present invention provides the polypropylene resin composition as described above, wherein the resin temperature (T) is 170 ° C. <T <300 ° C.
The present invention relates to a method for producing a polypropylene resin molded product that is injection-molded within the range.

[0013]

Tree fat group formed product (1) Polypropylene resin composition according to the present invention DETAILED DESCRIPTION OF THE INVENTION (1) is converted shear rate R ¹ in the injection molding 50 or less or 100 or more, preferably a 100 or more It relates to a resin composition. Here, the converted shear rate R ¹ is represented by the product of the relaxation time τ (unit s) of the resin composition at the injection molding temperature and the shear rate R ² (unit s ⁻¹ ) of the resin composition in the mold. Value. That is, R ¹ = τ × R ²

The relaxation time τ is a value determined from the characteristics of the resin composition to be injected and the injection molding temperature, and can be calculated by the stress relaxation measuring method after the steady flow is stopped.

The shear rate R ² is a value determined by the capacity of the injection molding machine and the characteristics of the mold, and the specific heat of the resin composition, thermal conductivity, shear viscosity, melt density, no-flow temperature, etc. Can be calculated by first using the resin flow analysis software, for example, MOLDFLOW manufactured by Moldflow Co., Ltd.

The reduced shear rate R ¹ , which is the product of the relaxation time τ and the shear rate R ² calculated by such a method, is 5
A resin composition having 0 or less or 100 or more, preferably 100 or more, can be injection-molded by using the resin composition as a raw material to obtain a resin molded product with few flow marks.

The tree fat group forming compound (2) polypropylene resin composition suitable for exhibiting the characteristics (2) is specifically (A) a polypropylene resin,
An example can be given which is composed of (B) an elastomer and (C) an inorganic filler.

A preferred resin composition is 50 to 99% by weight of (A) polypropylene resin, more preferably 55 to 8%.
0% by weight, (B) elastomer 0 to 50% by weight, more preferably 10 to 40% by weight, and (C) inorganic filler 0 to 30% by weight, more preferably 5 to 25% by weight, The total amount of (B) and (C) is 1 to 50% by weight, more preferably 15 to 45% by weight. When the composition of each component is within the above range, high rigidity and impact resistance are exhibited, and the rigidity and impact resistance are well balanced.

<Polypropylene Resin> The polypropylene resin (A) which is the main component of the resin composition may be a propylene homopolymer, or propylene and other α-olefins having 2 to 20 carbon atoms. It may be a copolymer thereof or a blend thereof.
Examples of the α-olefin here include ethylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-.
Mention may be made of penten, 1-octene and 1-decene. The copolymer is a mixture of propylene and α-olefin.
It may be a ternary system or a ternary system.

A preferred polypropylene resin is a propylene block copolymer containing a crystalline propylene homopolymer component and a random copolymer component of propylene and other α-olefin having 2 to 20 carbon atoms, If necessary, an α-olefin homopolymer component may be further included. As the α-olefin, the same α-olefin as described above can be used. Here, the propylene homopolymer component is preferably 70 to 97% by weight, more preferably 85 to 93% by weight, and the random copolymer component is preferably 3 to 30% by weight, more preferably 7 to 15% by weight. %.

Specific examples of the random copolymer of propylene and α-olefin include propylene / ethylene random copolymer, propylene / 1-butene random copolymer, propylene / 1-pentene random copolymer, propylene. 1-hexene random copolymer, propylene-4-methyl-1-pentene random copolymer, propylene / 1-octene random copolymer, propylene / 1
-Decene random copolymer, ethylene / propylene / 1
-Butene random copolymer, ethylene / propylene / 1
-Pentene random copolymer, ethylene / propylene /
1-hexene random copolymer, ethylene / propylene-4-methyl-1-pentene random copolymer, ethylene / propylene / 1-octene random copolymer, ethylene / propylene / 1-decene random copolymer You can

In this propylene block copolymer, the propylene homopolymer component has a boiling n-heptane insoluble content of 96% by weight or more and a melt flow rate of 5%.
~ 300 (g / 10 minutes), preferably 70-250 (g
/ 10 minutes). The propylene / α-olefin random copolymer component has an intrinsic viscosity [η] of 2 to 1
0 (dl / g), preferably 2 to 8 (dl / g), and the content of propylene units is 50 to 85% by weight, preferably 60 to 80% by weight, the content of α-olefin units other than propylene. The amount is 15 to 50% by weight, preferably 2
It is 0 to 40% by weight. When the content of the propylene and α-olefin units is within this range, the resin exhibits excellent impact resistance, rigidity and heat resistance. Then, according to ASTM D-1238 of the block copolymer, 230 ° C,
The value of melt flow rate measured under a load of 2.16 kg is 1 to 150 (g / 10 minutes), preferably 10 to 10
It is 0 (g / 10 minutes).

A particularly preferred block copolymer is a propylene / ethylene block copolymer having the following properties. (1) The content of the room temperature p-xylene insoluble component is preferably 70 to 97% by weight, more preferably 85 to 93% by weight.
Is. This insoluble component is mainly a crystalline propylene homopolymer.

(2) The room temperature p-xylene insoluble component is
The content of the boiling n-heptane insoluble matter is preferably 9
It is 6% by weight or more. Within this range, the block copolymer exhibits high crystallinity, and a resin composition having excellent heat resistance, rigidity and surface hardness can be obtained. (3) The crystalline propylene homopolymer component is ASTM
Based on D-1238, the melt flow rate (MFR) measured at 230 ° C. under a load of 2.16 kg is preferably 5 to 300 (g / 10 minutes), more preferably 70 to 2
It is 50 (g / 10 minutes).

(4) Room temperature The content of the p-xylene soluble component is preferably 3 to 30% by weight, more preferably 7-1.
It is 5% by weight. This soluble component is mainly a propylene / ethylene random copolymer. (5) The propylene / ethylene random copolymer component is
The intrinsic viscosity [η] measured at 135 ° C. in decalin is preferably 2 to 10 (dl / g), more preferably 2 to 8
(Dl / g). (6) The content of propylene units in the propylene / ethylene random copolymer component is preferably 50-8.
5% by weight, more preferably 60 to 80% by weight, and the content of ethylene unit is preferably 15 to 50% by weight, more preferably 20 to 40% by weight. Within this range, impact resistance and rigidity are high. A resin composition having excellent heat resistance is provided.

(7) The block copolymer has a MFR
Is preferably 1 to 150 (g / 10 minutes), more preferably 10 to 100 (g / 10 minutes). Within this range, good moldability and high mechanical strength are exhibited.

If desired, a modified polypropylene obtained by graft-modifying polypropylene with an unsaturated carboxylic acid and / or a derivative thereof can be added to the polypropylene resin. As such a graft modified product, a conventionally known one can be used, and its compatibility with other components can be increased by blending.

Such a polypropylene resin is obtained by polymerizing propylene using an olefin stereoregular polymerization catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst and optionally using other α-olefins in combination. , Can be manufactured. The propylene / ethylene block copolymer mentioned above as a particularly preferable example may be produced by mechanically mixing a propylene homopolymer and a propylene / ethylene random copolymer separately produced in advance, or propylene It is also possible to produce the homopolymer in the first step and then to produce it in the subsequent second step by a chemical mixing method such as a two-step polymerization method of producing a propylene / ethylene random copolymer.

<Elastomer> The elastomer (B) that can be used in the resin composition of the present invention may be any one having properties as an elastomer, and among them, an olefin-based thermoplastic elastomer or a styrene-based thermoplastic elastomer is preferable, A modified product obtained by graft-modifying the elastomer with an unsaturated carboxylic acid and / or a derivative thereof can also be used.

The olefin-based thermoplastic elastomer is a low-crystalline or non-crystalline α-olefin copolymer, and a copolymer containing ethylene as a constituent unit is particularly preferable. For example, ethylene propylene rubber (EPR),
Ethylene / 1-butene rubber (EBR), ethylene / 1
-Octene rubber (EOR), ethylene propylene
Examples thereof include 1-butene rubber (EPBR) and ethylene / propylene / diene rubber (EPDM).

The styrene-based thermoplastic elastomer is an elastomer containing styrene as a constituent unit, and is, for example, styrene-butadiene-styrene rubber (S
BS), styrene / isoprene / styrene rubber (SI
S), SBS hydrogenated styrene / ethylene /
Examples thereof include butylene / styrene rubber (SEBS) and SIS hydrogenated styrene / ethylene / propylene / styrene rubber (SEPS).

Among these, particularly EPR, EBR, E
OR, SEBS and mixtures thereof can be preferably used. Ethylene / α-such as EPR, EBR, EOR
In the case of an olefin copolymer, the content of ethylene units is preferably 30 to 90% by weight, more preferably 60 to 80%.
% By weight, and the content of α-olefin unit is 10 to 7
It is 0% by weight, more preferably 20 to 40% by weight. Moreover, the MFR value measured under the conditions of 230 ° C. and a load of 2.16 kg according to ASTM D-1238 is preferably 0.1 to 120 (g / 10 minutes), more preferably 0.5 to 60. A copolymer of (g / 10 minutes) is desirable.

<Inorganic Filler> As the inorganic filler (C), talc, calcium carbonate, barium carbonate, whiskers, glass fibers, mica, and other inorganic substances generally used as a compounding material for plastics can be used. Of these, talc and calcium carbonate are preferable.

<Resin Composition> A predetermined amount of the above-mentioned polypropylene resin, elastomer and inorganic filler is melt-kneaded with a kneading machine such as a uniaxial kneading machine, a biaxial kneading machine or a Banbury mixer to obtain a uniform composition. After that, it is usually processed into pellets and can be used as a resin composition.

When mixing the respective components, antioxidants, heat-resistant stabilizers, nucleating agents, ultraviolet absorbers, lubricants, antistatic agents, flame retardants, pigments,
You may mix | blend a dye, an organic filler, etc.

Injection Molded Product The polypropylene resin molded product according to the present invention is a molded product obtained by injection molding using the above-mentioned polypropylene resin composition as a raw material, and its shape is arbitrarily selected according to the application. I can decide. Therefore, this molded product has excellent heat resistance, rigidity, impact resistance, and surface hardness, and has a good appearance because there are few flow marks on the surface of the molded product. , Electrical parts, daily necessities, packaging materials, etc.

Method for Manufacturing Molded Article In the method for manufacturing a molded article according to the present invention, the resin composition described above is supplied to an ordinary injection molding machine and the resin temperature (T) is 1 or less.
Injection molding is performed in the range of 70 ° C <T <300 ° C. At that time, the relaxation time (τ: unit s) of the resin composition of the raw material
And the reduced shear rate (R ¹ ) represented by the product (τ × R ² ) of the shear rate (R ² : unit s ⁻¹ ) of the resin composition in the mold is 50 or less or 100 or more. Since it is adjusted to be 100 or more,
There are almost no flow marks on the surface of the molded product, and a molded product having a good appearance can be manufactured with good moldability.

[0038]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. First, various physical property measurements performed to evaluate the resin compositions and molded articles obtained in the examples were performed by the test methods described below.

(1) Melt flow rate (MFR): A
According to STM D-1238, the weight (g) of the resin extruded in a strand shape was measured by using a melt indexer under a load of 2.16 kg at 230 ° C. for 10 minutes.

(2) Relaxation time (τ): The stress relaxation behavior after the steady flow stop was measured using an ARES manufactured by Rheometrics Co. equipped with a cone plate having a diameter of 25 mm and a cone angle of 0.1 radian. The measurement temperature is 200,
230 and 250 ℃, the shear rate during steady flow is 1
(S- ¹ ), and the time was 120 seconds.

The time-dependent changes in the stress during steady flow and the stress after steady flow were determined, and "mechanical properties of polymer and composite material (LE Nielsen, translated by Shigeharu Onoki, Doujin Kagaku)" By the method described on pages 44 to 45,
τ (relaxation time) was calculated.

(3) Evaluation of flow mark: The molded product was visually evaluated in the following five grades. Rating 5: No flow mark is seen. Rating 4: Very thin flow marks are seen. Score 3: A thin flow mark is seen. Score 2: Clearly visible flow marks. Score 1: Very clear flow marks are visible.

The characteristics of the propylene / ethylene block copolymer used as the polypropylene resin are shown in Table 1. This block copolymer is composed of a propylene homopolymer component and a propylene / ethylene random copolymer component, and in Table 1, the propylene / ethylene random copolymer component is shown as a rubber part.

[0044]

[Table 1]

Ethylene-1 used as elastomer
The properties of the butene copolymer are shown in Table 2.

[0046]

[Table 2]

(Examples 1 to 26) (Comparative Examples 1 to 8) A polypropylene resin, an elastomer and an inorganic filler were blended in the proportions (% by weight) shown in Table 3 and melt-kneaded using a twin-screw kneading extruder. Then, three types of resin composition pellets were obtained.

[0048]

[Table 3]

Next, UBEMAX1 manufactured by Ube Industries, Ltd.
The resin composition shown in Table 3 was injection molded using a 50 injection molding machine. The width and length of the mold cavity used is
It was 40 mm and 200 mm, respectively. Also, the thickness of the molded product was two types, 1 mm and 2 mm. Table 4 shows the type of resin composition used, the injection molding conditions, and the degree of flow mark of the obtained molded product.

[0050]

[Table 4]

[0051]

The polypropylene resin composition of the present invention can be molded by injection molding to have high rigidity, impact resistance, surface hardness,
Further, it is possible to obtain a resin molded product with few flow marks while maintaining heat resistance. Further, according to the method for producing a resin molded product, the generation of flow marks on the surface of the molded product is small, and a molded product having an improved appearance can be manufactured with good moldability.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 101: 00) C08L 23:00 (C08L 23/10 25:04 23:00) (C08L 23/10 25:04) F-term (reference) 4F206 AA11 AA11F AA45 AA45F AB11 AM36 AR06 AR08 AR20 JA07 4J002 AA002 BB002 BB052 BB111 BB121 BB141 BB151 BB152 BC022 BP012 BP021 BP031 DE236 DJ046 DJ056 DL006 FA046 FD016GN0000

Claims (9)

[Claims] 1. The product (τ × R ² ) of the relaxation time (τ: unit s) of the resin composition at the injection molding temperature and the shear rate (R ² : unit s ⁻¹ ) of the resin composition in the mold. A polypropylene resin composition for injection molding, which has a reduced shear rate (R ¹ ) of 50 or less or 100 or more. 2. The polypropylene resin composition for injection molding according to claim 1, wherein the resin composition comprises (A) polypropylene resin, (B) elastomer and (C) inorganic filler. . 3. The resin composition comprises 50 to 99% by weight of (A) polypropylene resin and 0 to 50 (B) elastomer.
%, And (C) 0 to 30% by weight of inorganic filler, and the total amount of (B) and (C) is 1 to 50% by weight.
The polypropylene resin composition for injection molding according to claim 1, wherein 4. The polypropylene resin (A) has a melt flow rate of 1 to 150 (g / 10 minutes),
And a random copolymer component of 70 to 97% by weight of a propylene homopolymer component, propylene having an intrinsic viscosity [η] of 2 to 10 (dl / g), and other α-olefin having 2 to 20 carbon atoms. The polypropylene resin composition for injection molding according to claim 2 or 3, which is a propylene / α-olefin block copolymer composed of 3 to 30% by weight. 5. The polypropylene resin composition for injection molding according to claim 2, wherein the elastomer (B) is an olefinic thermoplastic elastomer or a styrene thermoplastic elastomer. 6. The (B) elastomer is an ethylene / α-olefin copolymer containing 30 to 90% by weight of an ethylene structural unit and 10 to 70% by weight of an α-olefin structural unit having 3 to 20 carbon atoms. The polypropylene resin composition for injection molding according to any one of claims 2 to 4, which is a united body. 7. The polypropylene resin composition for injection molding according to claim 2, wherein the inorganic filler (C) is talc or calcium carbonate. 8. A polypropylene resin molded article obtained by injection molding the polypropylene resin composition according to claim 1. 9. The polypropylene resin composition according to claim 1, which has a resin temperature (T) of 170 ° C. <T <3.
A method for producing a polypropylene resin molded article, characterized by performing injection molding in the range of 00 ° C.