JPS61233048A - Polypropylene resin composition - Google Patents

Abstract

PURPOSE:To provide a polypropylene resin composition having high rigidity and excellent low-temperature impact resistance, molding flowability, gloss and paintability, by compounding a specific crystalline ethylene-propylene block copolymer with a specific propylene-ethylene copolymer rubber and an inorganic filler. CONSTITUTION:(A) A crystalline ethylene-propylene block copolymer containing 6-30(wt)% ethylene and >=70% fraction insoluble in boiling n-heptane and having an intrinsic viscosity of 1.2-2.0 in tetraline at 135 deg.C and a melt flow index of >=8 is compounded with (B) a propylene-ethylene copolymer rubber having an ethylene content of 10-38% and a Mooney viscosity ML1+4 (100 deg.C) of 15-80 at 100 deg.C and (C) an inorganic filler having particle diameter of <=6mum. The ratios of the components A, B and C are 95-65pts.(wt.), 5-35pts. and 2-25pts. based on 100pts. of the sum of the components A and B.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a polypropylene resin composition that has excellent low-temperature impact resistance, high molding fluidity, surface gloss, and paintability, and has high rigidity. .

[Conventional technology]

Polypropylene resin has traditionally been widely used in various fields due to its excellent physical properties such as low specific gravity, high rigidity, chemical resistance, and heat resistance, but it has the disadvantage of low impact resistance at low temperatures. ing. In order to overcome this drawback, copolymerization with ethylene has been carried out, or methods have been carried out in which rubber-like substances such as ethylene-propylene copolymers and polyethylene are mixed. Furthermore, it is common practice to further improve rigidity, heat resistance, dimensional stability, paintability, etc. by blending various fillers with polypropylene resin.

However, at present, polypropylene resin has high rigidity and
Various contradictory physical properties such as high heat resistance, ease of painting, high molding fluidity, and high impact resistance are required, and high levels of physical properties are increasingly required for each of them.

Currently, various improvements have been proposed for these purposes; however, most of these proposals are insufficient to meet the advanced physical properties and balance of physical properties required in the current market. . Therefore, it is necessary to increase the amount of rubber components, fillers, etc. added to the polypropylene resin, or to perform special treatments, which inevitably leads to high prices in many cases.

In order to achieve the above object, the inventors first filed a patent application in 1973.
8-164074, the propylene content is 40 to 3
0% by weight, Mooney viscosity at 100'C is 15-80
We proposed a polypropylene resin composition using an ethylene-propylene copolymer rubber.

Although the above composition is an excellent composition, when molded using the resin composition, the surface gloss of the unpainted part of the product is poor, and further improvement is desired.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an inexpensive polypropylene resin composition that has excellent low-temperature impact resistance, high molding fluidity, and paintability, as well as high rigidity and high surface gloss.

Another object of the present invention is to provide a polypropylene resin composition suitable for use in large-sized molded products such as automobile bumpers, fenders, and side molds.

[Means for solving problems]

The inventors of the present invention have made extensive studies to improve the above-mentioned drawbacks, and found that when the ethylene content is 10 to 38% by weight,
Even if a propylene-ethylene copolymer rubber having a Mooney viscosity of 15 to 80 is used, not only can a balance of physical properties and paintability almost the same as in the previous application be obtained, but also a product with very good gloss can be obtained. This discovery led to the present invention.

That is, the present invention consists of the following components (a) to (c), and the blending ratio of each component is (a) 95 to +55 Jl parts, (b) 5 ~3
5 parts by weight, and (c) 2 to 25 parts by weight.

(a) Ethylene content 6-30% by weight, boiling n-heptane insoluble content 7S% by weight or more, tetralin solution (135% by weight)
C), a crystalline ethylene-propylene block copolymer having an intrinsic viscosity of 1.2 to 2.0 and a melt flow index of 8 or more.

(b) A propylene-ethylene copolymer rubber having an ethylene content of 10 to 58% by weight and a Mooney viscosity ML1+4 (100°C) of 15 to 80.

(e) Inorganic filler with a particle size of 6 μm or less.

The propylene-ethylene block copolymer used in the present invention has an ethylene content of 6 to 30% by weight, a content insoluble in boiling n-heptane of 75% by weight or more, and an intrinsic viscosity of a tetralin solution at 165°C of 1.2 to 2.0. , and the melt flow index is 8 or more. If the above-mentioned ethylene content is less than 6% by weight, the paintability of the resulting molded product will be reduced, and if it exceeds 30% by weight, the flexural modulus of the molded product will be reduced. In addition, if the n-heptane insoluble content of the polypropylene portion is less than 7S% by weight, the flexural modulus of the molded product will be small, and if the intrinsic viscosity of the tetralin solution at 135°C is less than 1.20, molding will be difficult. If the low-temperature impact strength of the product exceeds 2.0, the melt flow index of the resulting polypropylene composition will decrease; if the melt flow index is less than 8, the melt flow index of the polypropylene composition obtained will decrease. The melt flow index decreases, and in either case, the rigidity, impact resistance, and molding fluidity of the resulting polypropylene resin composition decrease, which is undesirable.

The propylene/ethylene copolymer rubber used in the present invention is limited to one having an ethylene content of 10 to 68% by weight and a Mooney viscosity ML++4 (100° C.) of 15 to 80. When the ethylene content is less than 10% by weight,
The produced propylene/ethylene copolymer rubber has poor productivity and properties, is difficult to handle, and is not practical. or,
If it exceeds 68% by weight, the flexural modulus, surface gloss, and paintability of the resulting molded product will deteriorate, which is undesirable. In addition, when a propylene/ethylene copolymer rubber having a Mooney viscosity ML1+4 (at 100°C) of less than 15 or more than 80 is added to the crystalline ethylene-propylene block copolymer, particles of the propylene/ethylene copolymer rubber dispersed in each If the diameter is too small or too large, the physical properties of the resulting molded product will be unbalanced, which is undesirable.

In addition, in the present invention, the amount of the propylene/ethylene copolymer rubber blended is 1/2, the total amount of the crystalline ethylene/propylene block copolymer and the propylene/ethylene copolymer rubber.
If the amount is less than 5 parts by weight, the impact resistance and paintability of the resulting composition will decrease, and if it exceeds 35 parts by weight, the molding fluidity, The flexural modulus decreases, which is not preferable in either case.

The inorganic filler used in the present invention is a powdered inorganic filler, such as calcium oxide, magnesium oxide, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, magnesium carbonate, calcium silicate, magnesium silicate, calcium sulfate. , calcium carbonate,
Examples include barium sulfate, calcium sulfite, talc, clay, glass, basic magnesium carbonate, dolomite, and wollastonite, with calcium carbonate, barium sulfate, calcium silicate, and talc being particularly preferred.

Further, in the present invention, it is essential that the particle size of the inorganic filler used is 6 μm or less, and particularly preferably 5 μm or less. If an inorganic filler with a particle size exceeding 6 μm is used, the impact resistance of the resulting polypropylene resin composition will decrease.

The particle size in the present invention is an equal area diameter determined by a light transmission method, and the value determined as the particle size at 50 o'clock (generally referred to as beam) of the particle size cumulative distribution is used.

In the present invention, the addition ratio of the inorganic filler with a particle size of 6 μm or less is 10% of the resin component consisting of a crystalline ethylene/propylene block copolymer and a propylene/ethylene copolymer rubber.
The amount ranges from 2 to 25 parts by weight relative to 0 parts by weight. If the proportion of the inorganic filler added is less than 2 parts by weight, the rigidity will not improve much and the effect of addition will be small, which is not preferable. If more than 25 parts by weight is added, the rigidity will improve to a certain extent, but the impact resistance and paintability will decrease, and especially the inorganic filler in the resin will absorb moisture, causing blisters between the resin layer and the paint film. This is undesirable because hot water resistance and moisture resistance deteriorate.

In addition, the inorganic filler used in the present invention may be surface-treated, for example, by surface treatment with various coupling agents such as silane type, titanate type, higher fatty acid type, unsaturated organic acid type, etc. This can be done with a processing agent.

Such surface treatment is effective in improving physical properties such as wire crosstalk, moldability, self-tap strength, and weld strength, in addition to the effects of the present invention.

The components used in the polypropylene composition of the present invention are mixed using a single-screw extruder commonly used in the art.
This is carried out using a twin-screw presser such as FCMlCIM.

Antioxidants that are generally added to polypropylene resin, within a range that does not significantly impair the effects of the present invention,
Heat stabilizers, ultraviolet absorbers, flame retardants, nucleating agents, organic/inorganic pigments, etc. may be used alone or in combination.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

In the following description, the melt flow index is AS
TM D-1238, flexural modulus is ASTM, D-79
0, Izot impact value was measured according to ASTM D-256, and surface gloss was measured according to ASTM D-52'5.

Example 1 Ethylene content: 12.5% by weight, boiling n-heptane insoluble content: 88% by weight, and intrinsic viscosity of a 135°C solution of tetralin: 1.
7. Crystalline ethylene with a melt flow index of 12.
75 parts by weight of propylene block copolymer (PP-A),
Ethylene content 24% by weight, Mooney viscosity ML1+4
25 parts by weight of propylene-ethylene copolymer rubber (PER-A) whose temperature (at 100°C) is 44.5, talc with a particle size of 1.3 μm as an inorganic filler, and the PP-A, PER
After adding 5 parts by weight and other antioxidants to 100 parts by weight of the total amount of -A, the whole was mixed in a Henschel mixer and pelletized using an extruder ζ trowel. The obtained pellets were molded into predetermined test pieces using an injection molding machine, and each physical property value was measured.

Furthermore, the paintability was evaluated by painting using the following two methods.

Coating method - A> A two-component acrylic-chlorinated polypropylene undercoat paint with a film thickness of 10 μm was applied to the test piece obtained using an injection molding machine.
After drying at 90℃ for 30 minutes, apply a two-component urethane top coat to a film thickness of 70μm, dry at 90℃ for 40 minutes, and leave at room temperature for 48 hours. A paintability test piece (test piece - person) was obtained by standing.

Coating method - B> Coating method - Using the same test piece as used in humans, after plasma treatment under the following conditions, a two-component urethane-based top coat was applied to a film thickness of 80 μm. Paint and 9
After drying at 0°C for 40 minutes, it was left to stand at room temperature for 48 hours to obtain a paintability test piece (test piece-B).

Plasma treatment conditions Plasma treatment device 2 Toshiba microwave plasma treatment device TMZ-2026M Processing gas: Oxygen treatment time: 30 seconds Gas pressure: 1.0 Torr Gas flow rate: 480 cc/m Microwave output crab 1soow obtained in this way A cut with a width of 10aIL was made in each test piece -A1-B using a cutter, and the 180° peel strength of the coating film was measured using an Instron tensile test.

Further, the coated product was immersed in warm water at 40° C., and the state of the coating film was visually judged after 240 hours.

○ No blisters in the coating film Δ l Slightly present × I Quite a lot The evaluation results of the melt flow index of the obtained polypropylene resin, the flexural modulus of the test piece, the measured Izot impact strength, the surface gloss, and the paintability are shown in Table 1. It was shown to.

Example 2 Test in the same manner as in Example 1 except that propylene/ethylene copolymer rubber (PER-B) having an ethylene content of 30% by weight and a Mooney viscosity ML1+4 (100°C) of 72 was used instead of PER-A. The results obtained are shown in Table 1.

Example 6 Instead of PP-A, the ethylene content was 10.5% by weight, the boiling n-heptane insoluble content was 85% by weight, the intrinsic viscosity of the tetralin solution at 135°C was 1.45, and the melt flow index was 40.
Crystalline ethylene-propylene block copolymer (PP
The test was carried out in the same manner as in Example 1 except that -B) was used, and the obtained results are shown in Table 1.

Example 4 A test was carried out in the same manner as in Example 1, except that the amount of PP-A added was 80 parts by weight and the amount of PER-A added was 20 parts by weight, and the obtained results are shown in Table 1.

Examples 5 to 6 Tests were conducted in the same manner as in Example 1, except that the amount of talc added was 2 parts by weight and 10 parts by weight, and the results obtained are shown in Table 1.

Examples 7-8 Tests were conducted in the same manner as in Example 1, except that barium sulfate with a particle size of 1.2 μm and calcium carbonate with a particle size of 1.9 μm were used as inorganic fillers in the proportions shown in Table 1. The results are shown in Table 1.

Comparative Example 1 A test was conducted in the same manner as in Example 1 except that no inorganic filler was added, and the results are shown in Table 1.

Comparative Example 2 Instead of PP-A, ethylene content was 72% by weight, boiling n-
Heptane insoluble content 93.8% by weight, Tetralin 165℃ solution intrinsic viscosity 2.4, melt flow index 1.6
crystalline ethylene-propylene block copolymer (pp
The test was conducted in the same manner as in Example 1, except that -c) was used, and the results are shown in Table 1.

Comparative Example 3 Same as Example 1 except that ethylene-propylene copolymer rubber (PER-C) having a propylene content of 55% by weight and a Mooney viscosity ML++4 (100°C) of 27 was used instead of PER-A. The results were shown in Table 1.

Comparative Example 4 Example 1 except that ethylene-propylene copolymer rubber (PER-D) having a propylene content of 26% by weight and a Mooney viscosity ML1-H (100°C) of 24 was used instead of PER-A. The results were shown in Table 1.

Comparative Example 5 A test was conducted in the same manner as in Example 1, except that talc with a particle size of 7 μm was used instead of talc with a particle size of 1.3 μm, and the obtained results are shown in Table 1.

Comparative Example 6 A test was conducted in the same manner as in Example 1, except that the amount of talc added was 30 parts by weight, and the results are shown in Table 1ζ.

Comparative Example 7 The amounts of PP-A and PER-A used were 50 parts by weight and 50 parts by weight, respectively.
The test was carried out in the same manner as in Example 1, except that the parts by weight were changed, and the obtained results are shown in Table 1.

〔Effect of the invention〕

The composition of the present invention has excellent low-temperature impact resistance, high molding fluidity, good gloss, and excellent paintability, so it is suitable for use in large molded products such as automobile bumpers, fenders, and side molds. .

Claims (1)

[Claims] (1) Consisting of the following components (a) to (c), the mixing ratio of each component is (a) 95 to 65 parts by weight, (b) to 100 parts by weight of the total amount of (a) and (b) ) 5 to 35 parts by weight; and (c) 2 to 25 parts by weight. (a) Ethylene content 6-30% by weight, boiling n-heptane insoluble content 75% by weight or more, tetralin solution (135°C)
A crystalline ethylene-propylene block copolymer having an intrinsic viscosity of 1.2 to 2.0 and a melt flow index of 8 or more. (b) ethylene content is 10-38% by weight, 100°C
Mooney viscosity ML_1_+_4 (100℃) at 15
-80 propylene-ethylene copolymer rubber. (c) Inorganic filler with a particle size of 6 μm or less.