JPH1129690A - Polypropylene-based resin composition and its injection molding product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both a polypropylene-based resin composition excellent in balance between impact strength and rigidity and its injection molding product. SOLUTION: This composition and its injection molding product comprise (1) 55-75 wt.% of a polypropylene-based resin (A) selected from (i) a propylene- ethylene block copolymer having a propylene homopolymer part which is a first segment and a propylene-ethylene random copolymer part which is a second segment and (ii) a mixture of (i) the propylene-ethylene block copolymer and a propylene homopolymer, (2) 10-15 wt.% of an ethylene-octene copolymer rubber (B) having 0.5-10 g/minute MFR (melt flow rate at 190 deg.C), 20-25 wt.% octene content and 0.860-0.875 density and (3) 15-30 wt.% of a talc (C) having <=3 μm average particle diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has excellent rigidity and impact resistance in terms of physical properties, and has a short molding cycle in terms of injection molding workability, and has the occurrence of flow marks, weld lines and surface distortion. TECHNICAL FIELD The present invention relates to a polypropylene-based resin composition having a characteristic in surface quality, such as absence of a resin, and an injection molded article thereof. More specifically, a polypropylene resin composition comprising a specific polypropylene-based resin, a specific ethylene-octene copolymer rubber component and talc, and having excellent physical properties and injection molding processability as described above, and injection molding the same. TECHNICAL FIELD The present invention relates to an injection molded article having excellent dimensional stability, particularly an injection molded article for an automobile interior (instrument, door trim, pillar, etc.) formed by the method.

[0002]

2. Description of the Related Art Recently, a propylene-ethylene block copolymer has been used as an automotive interior material in view of weight reduction and cost reduction. However, conventional propylene-
Ethylene block copolymer material has low impact strength,
In addition, the amount of the inorganic filler was large in order to impart thermal properties such as rigidity and heat deformation temperature, so that the specific gravity was relatively large. In order to improve the impact strength, it is possible to blend an ethylene-propylene copolymer rubber or an ethylene-octene copolymer rubber with a propylene-ethylene block copolymer, for example, as described in JP-A-53-22552 and JP-A-6-159.
92500, JP-A-6-248156, JP-A-6-248
192506 and JP-A-53-40045. However, since ethylene-propylene copolymer rubber and ethylene-octene copolymer rubber are compounded, thermal properties such as rigidity and thermal deformation temperature are inferior as materials for automobile interiors. In order to solve this, inorganic fillers such as calcium carbonate, barium sulfate, mica, crystalline calcium silicate and talc may be added and blended, for example, as described in JP-A-51-136735 and JP-A-53-136735.
-64256, 53-64257, 57-55
No. 952, No. 57-207630, No. 58-1713
No. 9, No. 58-111846, No. 59-98157
And Japanese Patent Publication No. 55-3374. Thus, the composition of propylene-ethylene block copolymer / ethylene-propylene copolymer rubber or ethylene-octene copolymer rubber (abbreviated as ethylene-propylene or ethylene-octene copolymer rubber composition) is as follows. Because of its low cost, good moldability, etc., it is widely used as a material for automobile interiors.By improving the ethylene-propylene copolymer rubber component, the balance between impact strength and rigidity can be further improved. The development of good materials is required.

[0003]

In such a situation,
The present invention relates to a conventionally used ethylene-propylene,
Another object of the present invention is to provide a polypropylene resin composition having a better balance between impact strength and rigidity as compared with an ethylene-octene copolymer rubber composition, and an injection molded article thereof.

[0004]

Means for Solving the Problems The present inventor has proposed a polypropylene resin composition which satisfies the above object by using a polypropylene resin as a main component and adding a specific rubber component thereto at a specific composition ratio. The present inventors have found that the injection molded article can be obtained, and have reached the present invention. That is, the present invention is as follows. [1] (1) A polypropylene resin (A) selected from the following (i) or (ii): 55 to 75 wt% (i) a propylene homopolymer portion as the first segment and propylene-ethylene as the second segment Propylene-ethylene block copolymer having random copolymer part (ii) Mixture of propylene-ethylene block copolymer of (i) and propylene homopolymer (2) MFR at 190 ° C. (melt flow rate, JI
SK-6758, the same applies hereinafter) from 0.5 to
10g / 10min, octene component content 20-25wt
% And a density of 0.860 to 0.875 ethylene-octene copolymer rubber (B): 10 to 15 wt% (3) Talc (C) having an average particle diameter of 3 μm or less: 15 to 15%
A composition containing 30 wt%, wherein the amount of the second segment of the propylene-ethylene block copolymer of the polypropylene resin (A) is (A) ′, and the content of the ethylene-octene copolymer rubber is (B) ′. Then, the following equation: 0.25 ≦ {(A) ′ / [(A) ′ + (B) ′]} ≦
0.40, and the composition has a flexural modulus at 23 ° C. of X (kg / cm ² ) and an Izod impact strength at 23 ° C. of Y (kg * cm / cm). Y ≧ −0.002X + 85 (however, X ≧ 20000, Y ≧ 15) is satisfied, and 23
Has an elongation of 150% or more in a tensile test at 150 ° C. and an MFR (230 ° C.) of 15 to 25 g / 10 min,
A polypropylene resin composition having a density of 1.00 to 1.14. [2] An injection molded article obtained by molding the polypropylene resin composition according to [1] by an injection molding method. [3] The injection molded article according to the above [2], wherein the injection molded article is for an automobile interior.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, the polypropylene-based resin (A) is a polymer mainly composed of propylene.
A propylene homopolymer portion as a segment, a propylene-ethylene block copolymer of a propylene-ethylene random copolymer portion as a second segment, or (ii) a mixture of the propylene-ethylene block copolymer of (i) and a propylene homopolymer.

The polypropylene resin (A) of the present invention comprises:
Weight average molecular weight (Mw) / number average molecular weight (Mn) representing the molecular weight distribution of the propylene homopolymer portion by gel permeation chromatography (GPC).
The Q value as a ratio is preferably 3.0 to 5.0, and more preferably 3.5 to 4.5. When the Q value is less than 3.0, the fluidity deteriorates, and when the Q value exceeds 5.0, a favorable result cannot be obtained in the balance between the rigidity and the impact property. Here, the propylene homopolymer portion of the polypropylene resin (A) refers to both the propylene homopolymer and the first segment portion of the propylene-ethylene block copolymer (i).

Particularly preferable physical properties, compositions and the like when the polypropylene resin (A) is a propylene homopolymer are as follows. That is, as described above, the Q value is preferably 3.0 to 5.0, more preferably 3.5 to 4.5, and the isotactic pentad fraction calculated by ¹³ C-NMR is 0.1. 97 or more, preferably 0.9
8 or more. Isotactic pentad fraction of 0.
If it is less than 97, it is difficult to satisfy the desired rigidity and heat resistance. In addition, the intrinsic viscosity of the tetralin solution at 135 ° C [η] P
Is from 0.9 to 1.8 dl / g, preferably from 0.9 to 1.
6 dl / g. Intrinsic viscosity [η] P is 0.9 dl /
If it is less than g, the impact strength becomes low in terms of physical properties, and a favorable result cannot be obtained. If it exceeds 1.8 dl / g, the fluidity deteriorates.

Particularly preferred physical property values when the polypropylene resin (A) is a propylene-ethylene block copolymer (i) having a propylene homopolymer portion as the first segment and a propylene-ethylene random copolymer portion as the second segment The composition and the like are as follows. The physical properties of the propylene homopolymer portion that is the first segment in the propylene-ethylene block copolymer (i) are the same as those of the propylene homopolymer. That is, the Q value is 3.0 to 5.0, preferably 3.5 to 4.5, and the isotactic pentad fraction calculated by ¹³ C-NMR is 0.97, preferably 0.98 or more. It is. Further, the intrinsic viscosity [η] P of the 135 ° C. tetralin solution is 0.9 to 1.8 dl / g, preferably 0.9 to 1.6 dl / g. The propylene homopolymer portion, which is the first segment of the propylene-ethylene block copolymer (i), can be obtained by removing the propylene homopolymer portion from the polymerization tank after the polymerization of the propylene homopolymer portion in the first step.

Next, the propylene-ethylene random copolymer portion as the second segment in the propylene-ethylene block copolymer (i) is preferably 5 to
30% by weight, more preferably 10 to 20% by weight
It is. The ethylene content (C2 ') EP of the propylene-ethylene random copolymer portion is preferably 25 to 55% by weight, more preferably 30 to 50% by weight. 25
If it is less than 55% by weight or more than 55% by weight, favorable results are not obtained with respect to the impact resistance of the composition. Also, the intrinsic viscosity [η] of the propylene-ethylene random copolymer portion
EP is preferably 4.0 to 6.0 dl / g, more preferably 4.5 to 6.0 dl / g. If it is less than 4.0 dl / g, favorable results cannot be obtained in balance between rigidity and impact strength. On the other hand, if it exceeds 6.0 dl / g, a bumpy portion occurs, and a favorable result cannot be obtained in terms of surface quality.

Next, a method for measuring the above-mentioned various physical properties will be described. The isotactic pentad fraction refers to A.I. Z
Macromolecule by amberli et al.
s, 6 , 925 (1973), i.e., isotactic linkage in pentad units in a polypropylene molecular chain measured using ¹³ C-NMR, in other words, five propylene monomer units. It is the fraction of propylene monomer units at the center of successive meso-linked chains. However, regarding the assignment of NMR absorption peaks, Macromolecule published afterwards
s, 8 , 687 (1975). Specifically, the isotactic pentad fraction is measured as the area fraction of the mmmm peak among all the absorption peaks in the methyl carbon region of the ¹³ C-NMR spectrum. By this method, UK NATIONAL PHYSICAL L
ABORATORY's NPL CRM CRM No. M
19-14 Polypropylene PP / MWD
The isotactic pentad fraction of / 2 was 0.944.

In the propylene-ethylene block copolymer (i), the weight ratio X of the propylene-ethylene random copolymer portion to the entire block copolymer is determined by measuring the heat of crystal fusion of the propylene homopolymer portion and the entire block copolymer. Thus, it can be obtained by calculation from the following equation. X = 1− (ΔHf) T / (ΔHf) P (ΔHf) T: heat of fusion of the entire block copolymer (cal / g) (ΔHf) P: heat of fusion of the propylene homopolymer portion (cal / g) Propylene-ethylene random The ethylene content of the copolymer portion can be determined by measuring the ethylene content of the entire block copolymer in terms of% by weight by an infrared absorption spectrum method and calculating from the following equation. (C2 ') EP = (C2') T / X (C2 ') T: ethylene content (% by weight) of the whole block copolymer (C2') EP: ethylene content (% by weight) of the propylene-ethylene random copolymer portion

Further, in the propylene-ethylene block copolymer (i), the intrinsic viscosity [η] EP of the propylene-ethylene random copolymer portion is obtained by measuring the intrinsic viscosities of the homopolymer portion and the entire block copolymer by the following formula. Can be obtained by calculation. [Η] EP = [η] T / X- (1 / X-1) [η] P [η] P: Intrinsic viscosity of propylene homopolymer part (dl / g) [η] T: Inherent of block copolymer Viscosity (dl
/ G)

When used in applications where impact resistance is particularly required, the polypropylene-based resin comprises a crystalline propylene homopolymer portion which is the first segment polymerized in the first step and a second segment polymerized in the second step. It is preferable to use a propylene-ethylene block copolymer consisting of a propylene-ethylene random copolymer portion as a segment. The block copolymer can be produced by a slurry polymerization method, a gas phase polymerization method, or the like.

The ethylene-octene copolymer rubber (B) has an MFR at 190 ° C. of 0.5 to 10. If the MFR at 190 ° C. is 10 or more, favorable results regarding impact strength cannot be obtained. If the MFR at 190 ° C. is less than 0.5, dispersion with the polypropylene resin (A) is poor and favorable results regarding impact strength are obtained. Absent.

The ethylene-octene copolymer rubber (B) has an octene content of 20 to 25% by weight. If the octene content is less than 20 wt%, favorable results on impact resistance cannot be obtained, and if it exceeds 25 wt%, favorable results on rigidity cannot be obtained.

The ethylene-octene copolymer rubber (B) has a density of 0.860 to 0.875. 0.86 density
If it is less than 0, a favorable result for rigidity is not obtained, and 0.875
If it exceeds 300, favorable results regarding impact resistance cannot be obtained.

Such an ethylene-octene copolymer rubber (B) is prepared by using a Ziegler-Natta catalyst system comprising a vanadium compound, an organoaluminum compound and a halogenated ester compound in an inert organic solvent such as a hydrocarbon. It can be obtained by copolymerizing octene. Further, it can also be obtained by copolymerizing ethylene and octene using a so-called metallocene catalyst, which is a catalyst in which a known metallocene compound coordinated to titanium, zirconium or hafnium is combined with alumoxane.

The talc used in the present invention has an average particle size of 3
μm or less. If it is larger than 3 μm, the impact strength is greatly reduced, and the appearance such as gloss is also deteriorated. Talc may be used without treatment, but various silane coupling agents, titanium coupling agents, and higher fatty acids commonly known for the purpose of improving the interfacial adhesion with the polypropylene resin and improving the dispersibility And those whose surfaces have been treated with higher fatty acid esters, higher fatty acid amides, higher fatty acid salts or other surfactants. Here, the average particle diameter of talc is a 50% equivalent particle diameter D50 obtained from an integral distribution curve of a sieving method measured by suspending in a dispersion medium such as water or alcohol using a centrifugal sedimentation type particle size distribution analyzer.
Means that

In the present invention, when the second segment amount of the propylene-ethylene block copolymer of the polypropylene resin (A) is (A) 'and the ethylene-octene copolymer rubber content is (B)', The following equation: 0.25 ≦ {(A) ′ / [(A) ′ + (B) ′]} ≦
0.40 must be satisfied. If the value is less than or more than these values, favorable results regarding impact strength cannot be obtained.

The polypropylene-based resin composition of the present invention comprises
Assuming that the flexural modulus at 3 ° C. is X and the Izod impact strength at 23 ° C. is Y, the following formula must be satisfied: Y ≧ −0.002X + 85 (where X ≧ 20000, Y ≧ 15). If it is less than these values, a desirable shape as a molded article for automobile interior cannot be obtained.

The tensile elongation of the polypropylene resin composition of the present invention is at least 150%. 15 elongation
If it is less than 0%, brittle fracture is likely to occur, and a favorable result cannot be obtained as a molded article for automobile interior.

The polypropylene resin composition 2 of the present invention
The MFR at 30C is 15-25 g / 10 minutes. MFR
If it is less than 15, the fluidity is poor and molding becomes difficult.
On the other hand, if the MFR exceeds 25, no favorable result can be obtained for the impact strength.

The density of the polypropylene resin composition of the present invention is from 1.00 to 1.14. If the value is less than or more than these values, a preferable shape as a molded article for automobile interior cannot be obtained.

The composition of the present invention can be produced by using a kneader such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, or a hot roll. The mixing of each component may be performed simultaneously or may be performed separately. As a method of divided addition, polypropylene resin (A) and talc (C)
After kneading, ethylene-octene copolymer rubber (B)
Or a method of adding talc (C) to a polypropylene resin (A) at a high concentration in advance to form a master batch,
There is a method of kneading it while diluting it separately with a polypropylene resin (A) or an ethylene-octene copolymer rubber (B). Further, as a second method of the divisional addition, after kneading the crystalline polypropylene (A) and the ethylene-octene copolymer rubber (B), adding talc (C) and kneading the mixture, or adding the talc (C) to the polypropylene (A) in advance. A method in which the ethylene-octene copolymer rubber (B) is kneaded at a high concentration to form a masterbatch, to which polypropylene (A) and talc (C) are added and kneaded, is also suitably employed. Third of split addition
Is a method in which polypropylene (A) and talc (C), and polypropylene (A) and ethylene-octene copolymer rubber (B) are kneaded beforehand, and finally, they are combined and kneaded. The temperature required for kneading is 170-250 ° C, and the time is 1-20 minutes. Further, in these kneaders, in addition to these basic components, if necessary, antioxidants, ultraviolet absorbers, lubricants,
Additives such as a pigment, an antistatic agent, a copper damage inhibitor, a flame retardant, a neutralizing agent, a foaming agent, a plasticizer, a nucleating agent, an air bubble preventing agent, and a crosslinking agent can be appropriately compounded.

The polypropylene resin composition of the present invention can be formed into an injection molded article by a generally employed molding method. In particular, it is suitably used as a molded article for an automobile interior.

[0026]

EXAMPLES The present invention will be described below with reference to examples, but these are merely examples, and the present invention is not limited to these examples unless departing from the gist. Next, methods for measuring physical properties in the examples are described below. (1) Melt flow rate According to a method specified in JIS-K-6758. The measurement temperature was 230 ° C and the load was 2.16 unless otherwise specified.
It was measured in kg. (2) Bending test According to the method specified in JIS-K-7203. A test piece molded by injection molding is used. The thickness of the test piece is 6.4 mm, and the flexural modulus (FM) and flexural strength (FS) are evaluated under the conditions of a span length of 100 mm and a load speed of 2.0 mm / min. The measurement was performed at 23 ° C. (3) Izod impact strength (IZOD) According to the method specified in JIS-K-7110. A test piece molded by injection molding is used. The thickness of the test piece is 6.4 mm, and the notched impact strength that is notched after molding is evaluated. The measurement was performed at 23 ° C. (4) Tensile test According to the method specified in ASTM D638. A test piece molded by injection molding is used. The thickness of the test piece is 3.
The elongation at break (UE) was 2 mm and the tensile speed was 10 mm / min. The measurement was performed at 23 ° C. (5) Ethylene content, propylene content The ethylene content or propylene content appears in an infrared absorption spectrum measured by preparing a press sheet.
Methyl group (-CH ₃₎ and methylene group (-CH ₂
It was determined by the calibration curve method using the absorbance of the characteristic absorption of-). (6) Intrinsic Viscosity Using an Ubbelohde viscometer, reduced viscosities were measured at three points of concentrations of 0.1, 0.2 and 0.5 g / dl. Intrinsic viscosity is described in “Polymer Solution, Polymer Experimental Science 11” (198
The calculation method described on page 491 of Kyoritsu Shuppan Co., Ltd. (2 years), that is, the reduced viscosity was plotted against the concentration, and the extrapolation method was used to extrapolate the concentration to zero. The polypropylene resin was evaluated at a temperature of 135 ° C. using tetralin as a solvent. The ethylene-α-olefin copolymer rubber (a) was evaluated at a temperature of 70 ° C. using xylene as a solvent. (7) Molecular weight distribution (Q value) It was measured by gel permeation chromatography (GPC) and performed under the following conditions. GPC: 150C type manufactured by Waters Co., Ltd. Column: Shodex 80 MA manufactured by Showa Denko KK 2 samples Sample amount: 300 μl (polymer concentration 0.2 wt%) Flow rate: 1 ml / min Temperature: 135 ° C. Solvent: o-dichlorobenzene Toyo Calibration curves of elution volume and molecular weight were prepared using standard polystyrene manufactured by Soda Co., Ltd. The polystyrene-equivalent weight average molecular weight and number average molecular weight of the sample were determined using a calibration curve, and Q value = weight average molecular weight / number average molecular weight was determined as a scale of the molecular weight distribution.

The test pieces for evaluating physical properties of (2), (3) and (4) were prepared under the following injection molding conditions. The composition was dried at 120 ° C. for 2 hours with a hot air drier, and then molded at a molding temperature of 220 using an IS150EV type injection molding machine manufactured by Toshiba Machine Co.
Injection molding was performed at a temperature of 50 ° C., a mold cooling temperature of 50 ° C., an injection time of 15 sec, and a cooling time of 30 sec. The following compositions were produced under the following conditions. After uniformly premixing the polypropylene resin (A) and 0.2 parts by weight of aluminum p-tert-butyl benzoate as a nucleating agent with the composition shown in Table 3 using a Henschel mixer and a tumbler, a biaxial kneading extruder ( Nippon Steel Works TEX44SS 30BW
-2V type) at an extrusion rate of 30 kg / hr, a screw rotation speed of 900 rpm, and under a vent suction. The abbreviations in the table indicate the following. BC: propylene-ethylene block copolymer PP: propylene homopolymer EPR: ethylene-propylene copolymer rubber EOR: ethylene-octene copolymer rubber P part: propylene homopolymer part in BC EP part: propylene-ethylene random copolymer part in BC

Example 1 50% by weight of a propylene-ethylene block copolymer, 15% by weight of a propylene homopolymer,
14% by weight of octene copolymer rubber, average particle size 2.5
A test piece was injection-molded from a polypropylene-based resin composition obtained by kneading 21 μm of talc under predetermined conditions. Tables 1 and 2 show the physical properties of various materials, and Table 3 shows the composition ratios.
Table 4 shows the physical property results. The formula 系 (A) ′ / [(A) ′ +
(B) ′]｝ is 0.3. Also, the formula -0.00
The value of 2X + 85 is 32.0.

Comparative Example 1 50% by weight of a propylene-ethylene block copolymer, 15% by weight of a propylene homopolymer, 14% by weight of an ethylene-propylene copolymer rubber, and an average particle size of 2.
5 μm talc was kneaded under predetermined conditions at 21% by weight, and a test piece was injection molded. The physical properties of the various materials are shown in Tables 1 and 2, the composition ratio is shown in Table 3, and the physical property results are shown in Table 4. The formula {(A) ′ / [(A) ′>
+ (B) ′]｝ is 0.3. Also, the expression -0.0
The value of 02X + 85 is 32.4. Examples of the present invention have better fluidity than the comparative examples, and Izod impact strength,
It is also well-balanced and excellent in physical properties of embrittlement temperature.

[0030]

[Table 1] BC: Propylene-ethylene block copolymer PP: Propylene homopolymer P part: Propylene homopolymer part of BC or the whole PP EP part: Propylene-ethylene random copolymer part of BC Content 1: Content of EP part in BC Content 2: EP part Content of ethylene in mmmm: isotactic pentad fraction

[0031]

[Table 2] EPR: Ethylene-propylene copolymer rubber EOR: Ethylene-octene copolymer rubber

[0032]

[Table 3]

[0033]

[Table 4] MFR: Melt flow rate (g / 10 minutes) FM: Flexural modulus (kg / cm ² ) FS: Flexural strength (kg / cm ² ) UE: Elongation at break (%)

[0034]

The polypropylene resin composition according to the present invention is excellent in rigidity, impact strength and flowability.
The polypropylene resin composition provided by the present invention is suitably used for injection molded articles, particularly molded articles for automobile interiors, utilizing such physical properties.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 23:08) (C08L 53/00 23:08 23:12) B29K 23:00 B29L 31:58

Claims (3)

[Claims] (1) A polypropylene resin (A) selected from the following (i) or (ii): 55 to 75 wt% (i) a propylene homopolymer portion as the first segment and propylene as the second segment -Propylene-ethylene block copolymer having ethylene random copolymer part (ii) Mixture of propylene-ethylene block copolymer of (i) and propylene homopolymer (2) Melt flow rate (JIS-K-6758, 1
90 ° C.) is 0.5 to 10 g / 10 min, the octene component content is 20 to 25 wt%, and the density is 0.860 to
0.875 ethylene-octene copolymer rubber (B):
10 to 15 wt% (3) Talc (C) having an average particle size of 3 μm or less: 15 to 15%
A composition containing 30 wt%, wherein the amount of the second segment of the propylene-ethylene block copolymer of the polypropylene resin (A) is (A) ′, and the content of the ethylene-octene copolymer rubber is (B) ′. Then, the following equation: 0.25 ≦ {(A) ′ / [(A) ′ + (B) ′]} ≦
0.40, and the composition has a flexural modulus at 23 ° C. of X (kg / cm ² ) and an Izod impact strength at 23 ° C. of Y (kg * cm / cm). Y ≧ −0.002X + 85 (however, X ≧ 20000, Y ≧ 15) is satisfied, and 23
C. and a melt flow rate (JIS-K-6758, 23
0 ° C) is 15-25 g / 10 min, and the density is 1.00
1.14. A polypropylene-based resin composition, which is 1.14. 2. An injection molded article obtained by molding the polypropylene resin composition according to claim 1 by an injection molding method. 3. The injection molded article according to claim 2, wherein the injection molded article is for an automobile interior.