JP2001114956A - Thermoplastic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin composition, especially a polypropylene resin composition, excellent not only in surface hardness but also in impact resistance. SOLUTION: A thermoplastic resin composition is prepared by compounding (A) 50-99 wt.% polypropylene resin with (B) 1-40 wt.% organic peroxide-treated ethylene-α-olefin random copolymer having a density of 0.85-0.90 g/cm3 and an MFR (230 deg.C, 2160 g load) of 0.1-100 g/10 min and (C) 0-40 wt.% inorganic filler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a thermoplastic resin composition having excellent surface hardness and excellent impact resistance. Specifically, the present invention can be suitably used for injection molded articles (including injection compression molded articles) such as interior and exterior parts of automobiles.
The present invention relates to a thermoplastic resin composition mainly composed of polypropylene.

[0002]

2. Description of the Related Art Polypropylene is widely used in various fields because of its low cost, low density, but good heat resistance, rigidity and moldability. However, since the impact resistance is inferior, ethylene-propylene block copolymer obtained by multi-stage polymerization for the purpose of improvement
Various polypropylene resin compositions to which a rubber component such as a propylene copolymer or an ethylene / butene copolymer and an inorganic filler such as talc are added have been proposed.

[0003] These resin compositions are used as molding materials for various industrial parts such as automobile interior / exterior parts such as bumpers, instrument panels and garnishes, and home electric appliance parts such as TV cases. In recent years, these products have been reduced in thickness, function, and size, and therefore, higher performance of materials is required.

However, since the effect of improving the impact resistance of the rubber component is small, it is necessary to include a large amount of the rubber component in order to improve the impact resistance. Although the thermoplastic resin composition containing a large amount of the rubber component has excellent impact resistance,
The rigidity, surface hardness, and heat resistance are greatly reduced. Therefore, it has been difficult to obtain a thermoplastic resin composition having excellent impact resistance and excellent rigidity, surface hardness, and heat resistance.

Attempts have been made to use other ethylene / α-olefin random copolymers or blends thereof instead of the rubber component. For example, JP
In JP-A-281915, the balance between molding dimensional stability, bending rigidity, and surface smoothness is improved by dynamically heat-treating polypropylene, an olefin random copolymer, and an organic peroxide. However, this propylene composition has room for improvement in impact resistance and surface hardness.

Japanese Patent Application Laid-Open No. 07-110325 proposes a material for automotive interior materials having excellent fogging resistance by dynamically heat treating polypropylene, an olefin random copolymer and an organic peroxide. I have. However, there is room for improvement in impact resistance and surface hardness.

Furthermore, Japanese Patent Application Laid-Open No. Hei 10-87919 proposes a stamping mold material in which polypropylene, an olefin random copolymer and an inorganic filler are dynamically heat-treated. There is still room for improvement. Therefore, development of a thermoplastic resin composition having excellent surface hardness and excellent impact resistance has been desired.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermoplastic resin composition, particularly a polypropylene resin composition, having excellent surface hardness and excellent impact resistance.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, have found that a polypropylene resin, an ethylene / α-olefin random copolymer treated with a specific organic peroxide, and optionally an inorganic filler. It has been found that the above-mentioned problems can be solved by blending, and the present invention has been completed.

That is, the present invention provides the following components (A) to
The present invention relates to a thermoplastic resin composition containing (C). (A) polypropylene resin; 50 to 99% by weight (B) Density is 0.85 to 0.90 g / cm ³ , and melt flow rate (MFR: 230 ° C., under a load of 2160 g) is 0.1 to 100 g / 10 1 to 40% by weight of an ethylene / α-olefin random copolymer finely cross-linked with an organic peroxide (C) an inorganic filler;

Further, the present invention provides an ethylene / α-olefin random copolymer as the component (B), wherein the MFR (MFR _b ) before the organic peroxide treatment and the MFR (MFF) after the treatment with the organic peroxide are used.
The ratio (MFR _b / MFR _a ) to R _a ) is 1.5 or more.

[0012] The present invention also relates to the thermoplastic resin composition, wherein the decomposition temperature for making the half life of the organic peroxide 1 minute is in the range of 150 to 250 ° C. Further, the present invention relates to the thermoplastic resin composition, wherein the ethylene / α-olefin random copolymer of the component (B) is polymerized using a metallocene catalyst.

Further, the present invention is characterized in that the ethylene / α-olefin random copolymer of the component (B) is a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms. The present invention relates to a thermoplastic resin composition. Also,
The present invention relates to the thermoplastic resin composition, wherein the ethylene / α-olefin random copolymer of the component (B) is a copolymer of ethylene and an α-olefin having 6 carbon atoms.

Further, the present invention relates to the thermoplastic resin composition, wherein the inorganic filler (C) is talc having an average particle size of 10 μm or less. Further, the present invention relates to a molded article obtained by molding the thermoplastic resin composition.

[0015]

Embodiments of the present invention will be described below. The thermoplastic resin composition of the present invention contains a polypropylene resin (component (A)) and an ethylene / α-olefin random copolymer (component (B)), and optionally further contains an inorganic filler (component (C)). May be included.

(1) Polypropylene resin (component (A)) The polypropylene resin (A) used in the present invention comprises:
Propylene homopolymer (homopolypropylene resin),
Alternatively, a copolymer of propylene and a small amount of another polymerizable monomer (comonomer) may be used. Examples of the comonomer include ethylene and α-olefins having 4 to 10 carbon atoms (specifically, 1-butene, 1-pentene, 4-methyl-
1-pentene, 1-hexene, 1-octene, etc.). Among them, a propylene / ethylene copolymer (ethylene content of about 0.1 to 5% by weight) is particularly desirable from the viewpoint of physical property balance and cost.

The propylene / ethylene copolymer is preferably synthesized by multi-stage polymerization. In multistage polymerization, first, propylene is polymerized in the presence of a Ziegler catalyst or the like to produce a crystalline propylene homopolymer portion (which may contain a small amount of a comonomer component). The mixture is switched to produce a propylene / ethylene copolymer portion.

The propylene / ethylene block copolymer synthesized by the multi-stage polymerization is substantially composed of a crystalline homopolypropylene portion, a propylene / ethylene copolymer portion, and a small amount of a crystalline homopolyethylene portion. Yes, each part may be present as a single polymer, or each may be in a linked state. Each of the above parts is basically composed of propylene and / or ethylene.
-Olefins, for example 1-butene, 1-pentene, 4
-Methyl-1-pentene, 1-hexene, 1-octene, diene-based monomers and the like may be contained in small amounts.

The above polypropylene resin can be produced by various methods. Among them, a preferable method is, for example, production by applying a known slurry polymerization method, a solution polymerization method, a liquid phase polymerization method using an olefin monomer as a medium, and a gas phase polymerization method in the presence of a stereoregular catalyst. Can be. As the polymerization catalyst, a Ziegler-Natta catalyst, a metallocene catalyst, or the like can be used. From the viewpoint of the balance between the fluidity and the physical properties of the resin composition, the MFR of the polypropylene resin is preferably from 10 to 200 g / 10 minutes, and
0 to 150 g / 10 min is particularly preferred. An organic peroxide may be added to the polypropylene resin to reduce the molecular weight by a melt extrusion reaction or the like to adjust the melt flow rate to a desired value.

(2) Ethylene / α-olefin random copolymer (component (B)) The resin composition of the present invention is an organic peroxide-treated ethylene / α-olefin random copolymer having specific physical properties. (B) is contained as an essential component.

(I) Organic Peroxide Treatment The ethylene / α-olefin random copolymer (B) used in the present invention has been previously subjected to a dynamic thermal microcrosslinking treatment with an organic peroxide. The organic peroxide to be used preferably has a decomposition temperature at which the half-life is 1 minute within the range of 150 to 250 ° C, preferably 170 to 190 ° C.

Specifically, benzoyl peroxide,
Dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane,
2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, 1,3-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, n-butyl-4, 4-bis (t-butylperoxy) valerate, 1,3-bis (t-butylperoxyisopropyl) benzene, t-butylperoxybenzene, and the like.

Of the above, 2,5-dimethyl-2,5-
Di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-
3,1,3-bis (t-butylperoxy) -3,3
5-Trimethylcyclohexane and the like are preferable from the viewpoint of the surface hardness improving effect.

(Ii) Density The ethylene / α-olefin random copolymer (B)
Has a density of 0.85 to 0.90 g / cm ³ , preferably 0.86 to 0.88 g / cm ³ . When the ethylene / α-olefin random copolymer (B) having a density of less than 0.85 g / cm ³ is used, only a thermoplastic resin composition having insufficient hardness can be obtained, and the density is 0.90 g / c.
If the ethylene / α-olefin random copolymer (B) exceeding m ³ is used, only a thermoplastic resin composition having insufficient impact resistance can be obtained.

(Iii) Melt flow rate The ethylene / α-olefin random copolymer (B) after the dynamic thermal microcrosslinking treatment has an MFR (230 ° C., 2160
g load) is 0.1 to 100 g / 10 min, preferably 0.2 to 80 g / 10 min. MFR 0.1 g /
From the ethylene / α-olefin random copolymer of less than 10 minutes, only a thermoplastic resin composition having insufficient impact resistance and fluidity can be obtained, and the ethylene / α-olefin random copolymer having an MFR of more than 100 g / 10 minutes is obtained. Only a thermoplastic resin composition having insufficient impact resistance and surface hardness can be obtained from the copolymer. In addition, the MFR (MF
_Rb ) and the ratio of the treated MFR (MFR _a ) (MFR _b /
It is preferable that MFR _a ) is 1.5 or more from the viewpoint of improving the surface hardness.

(Iv) Production of ethylene / α-olefin random copolymer The above ethylene / α-olefin random copolymer (B)
Is obtained by subjecting an ethylene / α-olefin random copolymer (base rubber) obtained by polymerization to an organic peroxide treatment. The polymerization of the copolymer can be carried out using a known titanium-based catalyst, vanadium-based catalyst or metallocene catalyst, but is preferably carried out using a metallocene catalyst.

The organic peroxide treatment is carried out by blending the obtained copolymer (base rubber) with an organic peroxide, followed by melt-kneading at a predetermined temperature. The reaction conditions in the organic peroxide treatment are not particularly limited, but preferably, the reaction temperature is 180 to 230 ° C, the reaction time is 5 to 10
0 second, ratio of organic peroxide; 100 based on the total amount of copolymer
It is preferable to process at about 3000 ppm.

The ethylene / α thus obtained
The olefin random copolymer (B) is preferably a random copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms. Specific examples of such α-olefin include 1-butene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, and the like. Among them, a random copolymer of ethylene and an α-olefin having 6 carbon atoms is preferred. The ethylene and α
-The ethylene content of the olefin random copolymer (B) is not particularly limited, but is preferably from 40 to 90% by weight, and more preferably from 45 to 85% by weight. When the ethylene content is within the above range, the performance as a rubber is exhibited.

(3) Inorganic filler (component (C)) As the inorganic filler (C) used in the present invention, specifically, talc, calcium carbonate, glass fiber, basic magnesium sulfate whisker, calcium titanate Whiskers, aluminum borate whiskers, mica and the like. Among them, talc is preferred.

The talc preferably used in the present invention has an average particle diameter of 10 μm or less, preferably 5 μm or less. The average talc particle size can be measured by a laser diffraction scattering method. In the present invention, among such talcs, talc having an average aspect ratio (ratio of length or thickness in either the vertical or horizontal direction) of 4 or more, preferably 5 or more is used. The measurement of the talc aspect ratio is
It is determined from a value measured by a microscope or the like.

The talc is first produced by, for example, pulverizing raw talc with an impact mill or a micron mill type pulverizer, or finely pulverizing it with a micron mill or jet mill, and then using a cyclone or a micron separator. It is manufactured by a method such as classification adjustment.

The talc may be untreated or surface-treated in advance. Surface treatment is preferred because the rigidity and heat resistance of the composition can be improved. Specific examples of the surface treatment include a chemical or physical treatment using a treating agent such as a silane coupling agent, a higher fatty acid, a fatty acid metal salt, an unsaturated organic acid, or an organic titanate.

The method of surface treatment of talc using a metal salt is not particularly limited, and examples thereof include a method of mixing talc powder, which has been pulverized and classified in advance, and a predetermined amount of a metal salt with a high-speed mixer. When kneading and granulating the composition, a method may be used in which the metal salt and talc powder are blended and mixed with other polypropylene or the like, and the mixture is provided to a granulator. Further, the above-mentioned inorganic fillers may be used alone or as a mixture of several kinds.

(4) Other Ingredients The thermoplastic resin composition of the present invention may contain other additives, for example, a heat stabilizer, an oxidizing agent, for the purpose of other modification depending on its use such as interior and exterior materials of automobiles. An inhibitor, a light stabilizer, a flame retardant, a granulating agent, a plasticizer, an antistatic agent, a copper damage inhibitor, a release agent, a foaming agent, a coloring agent, a pigment and a dispersant thereof can be added. The above-mentioned various additives and pigments are generally added when each component is mixed. However, a high-concentration master batch may be prepared in advance and then blended after injection or extrusion.

(5) Mixing ratio of each component The mixing ratio of the above components is such that the polypropylene resin (A) accounts for 50 to 99% by weight, preferably 60 to 95% by weight, based on the total amount of the resin composition. The ethylene / α-olefin random copolymer (B) finely crosslinked with an oxide is 1 to 40% by weight, preferably 3 to 30% by weight, and the inorganic filler (C) is 0 to 40% by weight, preferably Is 1 to 40
%, More preferably 5 to 30% by weight.

When the content of the polypropylene resin (A) is less than 50% by weight, the rigidity and heat resistance of the obtained thermoplastic resin composition are reduced.
Hardness tends to decrease, while if it exceeds 99% by weight, impact resistance decreases. If the ethylene / α-olefin random copolymer (B) is less than 1% by weight, the impact resistance is insufficient, while if it exceeds 40% by weight, the strength, rigidity, heat resistance, hardness and the like are reduced. In addition, the inorganic filler (C) may not be blended in the resin composition of the present invention, but by including the inorganic filler (C), there is an advantage that rigidity is improved. However, when the amount of the inorganic filler (C) exceeds 40% by weight, impact resistance and ductility decrease.

(6) Production of thermoplastic resin composition The thermoplastic resin composition of the present invention comprises the components (A) to
(C) and other components used as needed are blended in the above blending ratio, and a usual kneading machine such as a single screw extruder, a twin screw extruder, a Banbury mixer, a roll mixer, a Brabender plastograph, a kneader and the like is used. And obtained by kneading. In this case, it is preferable to select a kneading method capable of uniformly dispersing the components, and usually kneading is performed using a twin-screw extruder. In this kneading, the compound of each of the above components may be kneaded at the same time or may be kneaded sequentially.

(7) Molding of thermoplastic resin composition The thermoplastic resin composition thus obtained is molded by injection molding (including gas injection molding) or injection compression molding (press injection). Accordingly, various molded products, particularly, interior and exterior parts of automobiles such as bumpers, instrument panels, and garnishes, and parts of home electric appliances such as TV cases can be obtained.

[0039]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. In addition, the raw materials and test methods used in Examples and Comparative Examples are as follows.

1. Raw Materials (1) Polypropylene resin (component (A); abbreviated as “PP”) PP: crystalline ethylene / propylene containing 8% by weight of an ethylene / propylene random copolymer part and having an MFR of 50 g / 10 min for the whole component A block copolymer was used.

(2) Ethylene / α-olefin random copolymer (component B) α-olefin carbon number, density, MFR (MFR _b ) before organic peroxide treatment, after organic peroxide treatment shown in Table 1 M
An ethylene / α-olefin random copolymer having FR (MFR _a ) was used. As the organic peroxide, 2,
5-Dimethyl-2,5-di (t-butylperoxy) hexyne-3 was used. In the organic peroxide treatment, the base rubber shown in Table 1 was used, and after blending the amount of peroxide shown in Table 1, a twin-screw extruder (manufactured by Nippon Steel Works, Ltd.) at a temperature of 200 ° C. (TEX30).

[0042]

[Table 1]

(3) Inorganic filler (C) Talc having an average particle size of 4.6 μm and an aspect ratio of 6 was used.

2. Physical property measurement method (1) Based on MFR ASTM-D1238, temperature 230 ° C, load 21
Measured at 60 g. (2) Izod impact strength (Izod) Measured at a temperature of 23 ° C. according to ASTM-D256 (unit is kJ / m ² ). (3) Rockwell hardness Measured according to ASTM-D785 (scale is R).

[0045]

Examples 1 to 7, Comparative Examples 1 to 6 Each component (A) to (C)
Were blended at the ratios shown in Tables 2 and 3, and dry-blended using a supermixer. Then, raw materials were supplied from a hopper and melt-kneaded using a high-speed twin-screw extruder (KCM, manufactured by Kobe Steel Ltd.). And extruded to obtain pellets. The obtained pellets were injection-molded at a resin temperature of 210 ° C. and a mold temperature of 30 ° C. using an injection molding machine, and physical property test pieces were molded and evaluated. The results are shown in Tables 2 and 3.

As shown in Tables 2 and 3, the thermoplastic resin compositions having the compositions shown in Examples 1 to 7 all exhibited a good balance of physical properties. On the other hand, those shown in Comparative Examples 1 to 6 had poor physical property balance.

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

The thermoplastic resin composition of the present invention has excellent surface hardness and also excellent impact resistance. Therefore, it is useful for products obtained by injection molding of industrial materials such as automotive interior / exterior parts and home electric parts. In particular,
It can be suitably used as a molding material for various industrial parts such as automobile parts such as bumpers, instrument panels, garnishes, and home electric appliance parts such as TV cases, etc. .

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) C08L 23:08 C08L 23:08 23:26) 23:26) F-term (reference) 4F071 AA15X AA20 AA21X AA75 AA76 AA88 AB30 AE17 AG05 AH11 BA01 BB05 BC03 4J002 BB052 BB121 BB141 BB151 BB202 BP021 DE186 DE236 DG046 DJ046 DJ056 DK006 DL006 FA046 FA066 FA086 FB086 FB096 FB166 FD016 GN00 GQ01

Claims (8)

[Claims] 1. A thermoplastic resin composition comprising the following components (A) to (C). (A) polypropylene resin; 50 to 99% by weight (B) Density is 0.85 to 0.90 g / cm ³ , and melt flow rate (MFR: 230 ° C., under a load of 2160 g) is 0.1 to 100 g / 10 1 to 40% by weight of an ethylene / α-olefin random copolymer finely cross-linked with an organic peroxide (C) an inorganic filler; 2. The ethylene / α-olefin random copolymer of the component (B) has a MFR before an organic peroxide treatment.
(MFR _b ) and the ratio of the treated MFR (MFR _a ) (MFF _b )
R _b / MFR _a) is according to claim 1 the thermoplastic resin composition wherein a is 1.5 or more. 3. The decomposition temperature at which the half life of the organic peroxide is 1 minute is in the range of 150 to 250 ° C.
Or the thermoplastic resin composition according to 2. 4. The thermoplastic resin composition according to claim 1, wherein the ethylene / α-olefin random copolymer of the component (B) is polymerized using a metallocene catalyst. object. 5. The ethylene / α-olefin random copolymer of the component (B) is a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms. The thermoplastic resin composition according to any one of the above. 6. The ethylene / α-olefin random copolymer of the component (B) is a copolymer of ethylene and an α-olefin having 6 carbon atoms.
6. The thermoplastic resin composition according to any one of items 1 to 5. 7. An inorganic filler (C) having an average particle size of 10 μm
The thermoplastic resin composition according to any one of claims 1 to 6, which is the following talc. 8. A molded article obtained by molding the thermoplastic resin composition according to claim 1.