JPH06256596A - Polypropylene resin molding - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a polypropylene resin molded product having excellent dimensional stability, mold releasability during injection molding, and moldability. [Structure] Expressed as a weight ratio, 45 to 70 parts of a polypropylene resin having a melt flow rate (X) of 10 to 60 g / 10 minutes and containing 0 to 8% of ethylene, and an amorphous ethylene-α-olefin 65 to 95% of polymer component consisting of 55 to 30 parts of polymer (EO copolymer)
And the inorganic filler is 5 to 35%. The relationship between the content (C) of the EO copolymer and the content (D) of the inorganic filler is D> 155-37InC. The EO copolymer is composed of 30 to 60% of a high molecular weight EO copolymer having a weight average molecular weight of 380,000 to 1,000,000 and 70 to 40% of a low molecular weight EO copolymer having a weight average molecular weight of 150,000 to 330,000. The linear expansion coefficient of polypropylene resin molded product is 5 × 10 ^-5 cm /
cm / ° C or lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene resin molded product excellent in dimensional stability, mold releasability during injection molding, and moldability.

[0002]

2. Description of the Related Art Polypropylene resin is a thermoplastic resin that is excellent in mechanical properties such as flexural strength and flexural modulus and chemical resistance and is inexpensive. Therefore, it has many uses such as interior / exterior parts for automobiles and industrial machines, home electric appliance parts and the like. However, on the other hand, thermal expansion and contraction are large,
There is a problem with dimensional stability.

In order to solve such a problem, conventionally, JP-A-61-34048, JP-A-61-21145, JP-A-1-272450, JP-A-2-311533,
JP-A-63-186754, JP-A-62-15333
4 and Japanese Examined Patent Publication No. 4-2620.

However, the polypropylene resins disclosed in the above-mentioned prior arts all have a linear expansion coefficient of 5.0 to 5.0.
It is in the range of 9.0 × 10 ⁻⁵ cm / cm / ° C. Therefore, thermal expansion and contraction are still large. In particular, when it is used as an elongated component such as a side molding, a rocker molding, a side garnish, a door lower molding, a bumper for automobiles, the dimensional stability is insufficient.

Therefore, the present inventors have made various studies, paying attention to further reducing the linear expansion coefficient. Then, a polypropylene resin molded product having a linear expansion coefficient of 3.0 to 3.9 × 10 ⁻⁵ cm / cm / ° C. and excellent in dimensional stability was invented (Japanese Patent Laid-Open No. 4-8744).

The polypropylene resin molded product is polypropylene / amorphous ethylene-α-olefin copolymer / fibrous filler system (PP / EPR / fibrous filler system). This uses 60-85% of a polymer component consisting of 30-70 parts by weight of polypropylene resin and 30-70 parts by weight of EPR having a Mooney viscosity of less than 70, and E
The linear expansion coefficient is lowered by setting the aspect ratio of PR to 5 or more and flatly dispersing the EPR.

[0007]

[Problems to be Solved] However, the surface adhesiveness of the molded product of polypropylene resin is
/ EPR / larger than that of fibrous filler system. Therefore, when injection molding a mirror-like molded product without grain,
The molded product sticks to the mold, making it difficult to release it. As a result, the molded product may be deformed or damaged during release.

Therefore, the present inventors have made the following studies. (1) Prolong the cooling time. (2) A mold release agent is applied to the mold. (3) Reduce the amount of EPR added. (4) Increase the molecular weight of EPR. (5) Increase the amount of fibrous filler added. (6) Two or more kinds of EPRs having different compositions and physical properties are combined.

However, in (1), the molding cycle becomes long. In (2), automatic molding cannot be performed. (3),
In (4), the linear expansion coefficient becomes large and the dimensional stability of the molded product deteriorates. In the case of (5), impact resistance and molding processability are deteriorated. Although (6) is disclosed in the above-mentioned various prior art documents, a method for simultaneously improving surface tackiness and dimensional stability has not been proposed.

As described above, the inventors further conducted various studies in order to solve the above various problems without impairing the low linear expansion performance and dimensional stability. In view of the above conventional problems, the present invention intends to provide a polypropylene resin molded product which is excellent in dimensional stability, releasability during injection molding, and moldability.

[0011]

According to the present invention, 45 to 70 parts by weight of a polypropylene resin having a melt flow rate (X) of 10 to 60 g / 10 minutes and containing 0 to 8 wt% of ethylene, and an amorphous ethylene-α-olefin are used. Copolymer (hereinafter,
It is called EO copolymer. The content of the EO copolymer is 65 to 95 wt% and the content of the inorganic filler is 5 to 35 wt%. The content (C) of the EO copolymer and the content of the inorganic filler ( The relationship with D) is
A polypropylene resin molded product having D> 155-37InC, wherein the EO copolymer has a weight average molecular weight of 38.
10,000 to 1 million high molecular weight EO copolymer 30 to 60 wt%
And a low molecular weight EO copolymer having a weight average molecular weight of 150,000 to 330,000 and 70 to 40 wt%, and having a linear expansion coefficient of 5
A polypropylene resin molded article is characterized by having a density of ^{x10 -5} cm / cm / ° C or less.

What is most noticeable in the present invention is that the melt flow rate (X) of polypropylene resin is 10 to 10.
60 g / 10 minutes, the EO copolymer is composed of a high molecular weight EO copolymer having a weight average molecular weight of 380,000 to 1,000,000 and a low molecular weight EO copolymer having a weight average molecular weight of 150,000 to 330,000, and The linear expansion coefficient of the polypropylene resin molded product is 5.0 × 10 ⁻⁵ cm / cm / ° C. or less.

The polypropylene resin molded product according to the present invention comprises a polymer component of 65 to 95 wt% (hereinafter referred to as%) and an inorganic filler of 5 to 35%. When the content of the polymer component is less than 65%, there are problems of reduction of impact strength and deterioration of surface quality. If it exceeds 95%, there is a problem that the linear expansion coefficient becomes 5.0 × 10 ⁻⁵ cm / cm / ° C. or more.

The polymer component is composed of 45 to 70 parts by weight (hereinafter referred to as "parts") of polypropylene resin and 30 to 55 parts of EO copolymer (amorphous ethylene-α-olefin copolymer). If the polypropylene resin is less than 45 parts, the content of the EO copolymer increases, so that the releasability and the appearance of the molded product deteriorate. If it exceeds 70 copies,
There is a problem that the coefficient of linear expansion becomes 5.0 × 10 ⁻⁵ cm / cm / ° C. or more.

The polypropylene resin comprises 0 to 8% ethylene and 92 to 100% polypropylene.
If the ethylene content (Y) exceeds 8%, the releasability deteriorates. The polypropylene resin has a melt flow rate (X) of 10 to 60 g / 10 minutes. 10 g
If it is less than / 10 minutes, the flowability of the blended material becomes poor and the molding cycle becomes long. In addition, the appearance of the molded product deteriorates.

On the other hand, when it exceeds 60 g / 10 minutes,
Since the dispersibility of the EO copolymer deteriorates, the appearance of the molded product deteriorates. The methyl flow rate is 230 ℃, 2.1
It is a measured value under the condition of a load of 6 kg / cm ² .

The ethylene content (Y) is preferably in the range of 0.3 to 7.0%, more preferably 0.5 to 6.0. Further, between the melt flow rate (X) and the ethylene content (Y), Y ≦ 0.08X + 3.4
It is preferable that In this case, the balance between the linear expansion coefficient and the releasability becomes particularly good.

As the polypropylene resin, in addition to homopolypropylene, a propylene-ethylene random copolymer, a propylene-ethylene block copolymer and a mixture thereof are used. Further, a modified polypropylene resin, that is, a polypropylene resin modified with an unsaturated carboxylic acid or its derivative and an organic oxide may be partially blended and used.

The EO copolymer comprises 30 to 60% of high molecular weight EO copolymer and 40 to 70% of low molecular weight EO copolymer. When the amount of the high molecular weight EO copolymer is less than 30%, the effect of improving the releasability is insufficient. If it exceeds 60%, the linear expansion coefficient becomes large.

The weight average molecular weight of the high molecular weight EO copolymer is 380,000 to 1,000,000. If less than 380,000,
The molecular weight is similar to that of a low molecular weight EO copolymer, and the effect of improving releasability becomes insufficient. On the other hand, when it exceeds 1,000,000, the linear expansion coefficient becomes large and the appearance of the molded product deteriorates.

The weight average molecular weight of the low molecular weight EO copolymer is 150,000 to 330,000. When it is less than 150,000, the crystallinity becomes high, which is not preferable. If it exceeds 330,000, the molecular weight becomes similar to that of the high molecular weight EO copolymer, which is not preferable.

Amorphous ethylene-α olefin copolymer (EO copolymer) means α such as propylene, butene-1, hexene-1, decene-1,4-methylbutene-1,4-methylpentene-1. An olefin is used as a copolymerization component. The term "amorphous" here means a material that does not substantially form a crystalline region. Further, among the above-mentioned amorphous ethylene-α-olefin copolymers, when the α-olefin is polypropylene, that is, when ethylene-propylene rubber (EPR) is used, a particularly excellent low linear expansion coefficient is exhibited.

The content (D) of the inorganic filler is the content (C) of the amorphous ethylene-α-olefin copolymer.
And D> 155-37InC (In is natural logarithm)
It is in. This relationship has a linear expansion coefficient of 5 × 10 ^-5 cm / c
It is necessary to keep the temperature below m / ° C (Fig. 2).

As the inorganic filler, there are fibrous filler, non-fibrous filler, flat-shaped filler and the like. Fibrous fillers include fillers in the fiber state such as potassium titanate whiskers, magnesium oxysulfate whiskers, aluminum borate whiskers, calcium carbonate whiskers, calcium sulfate whiskers, zinc oxide whiskers, wollastonite, glass fibers, carbon fibers and the like. To use.

The fibrous filler is the above-mentioned amorphous ethylene-α.
It acts with the olefin copolymer and contributes greatly to the reduction of the linear expansion coefficient. Among the above, in particular, potassium whisker titanate is a fibrous filler excellent in material properties and dimensional stability. As the non-fibrous filler, flat talc or mica, granular calcium carbonate, etc. are used.

In the present invention, in addition to the above components, crystalline polyethylene such as high-density polyethylene and low-density polyethylene, and an olefin-based copolymer of ethylene-vinyl acetate copolymer system are used for the purpose of adjusting mechanical properties and fluidity. Polymers or additives such as softeners, antioxidants, ultraviolet absorbers, lubricants, antistatic agents, nucleating agents, pigments, flame retardants, extenders and processing aids may be mixed.

Further, the above-mentioned respective components are melt-kneaded by using a kneader such as a single-screw extruder, a twin-screw extruder, a kneader, a Brabender or a Banbury mixer at least at a temperature at which the polypropylene resin is melted or higher. , The composition. Further, after the melt-kneading in this way, it is usually pelletized. Further, the composition is molded into a desired shape by injection molding, extrusion molding, blow molding or the like.

The polypropylene resin molded product of the present invention can be used for side garnishes, other electric parts, mechanical parts, etc. in addition to the side moldings and bumpers for the exterior of automobiles and ships. Especially, dimensional stability is required, and when it is used for a molded product having a mirror-free mirror surface, its characteristics are exhibited.

[0029]

FUNCTION AND EFFECT The polypropylene resin molded product of the present invention has a low coefficient of linear expansion of 5 × 10 ⁻⁵ cm / cm / ° C. or less. Therefore, there is almost no expansion or contraction due to heat, and it has excellent dimensional stability. In addition, the mold releasability during injection molding is good and the molding processability is also excellent. Therefore, even if the molded product has a long shape, without reinforcement such as metal inserts,
It can be attached to a mating member. Also, since it has excellent releasability, it is ideal for molded products that require a mirror-like smooth surface condition.

The reason why the polypropylene resin molded product of the present invention exhibits a low linear expansion coefficient as described above is presumed to be as follows. That is, the low molecular weight EO copolymer has better compatibility with polypropylene than the high molecular weight EO copolymer. Also, the melt viscosity of the high molecular weight EO copolymer is lower. For these reasons, the high molecular weight EO copolymer and the low molecular weight EO copolymer do not exist independently, but the low molecular weight EO copolymer encloses the high molecular weight EO copolymer.

Therefore, the effect of suppressing the linear expansion coefficient is comparable to that when the low molecular weight EO copolymer is blended alone. In addition, it is considered that the presence of the high molecular weight EO copolymer forms fine irregularities on the surface of the molded product, thereby improving the releasability. The EO copolymer is evenly dispersed not only in the skin portion (surface layer portion) of the polypropylene resin molded product but also in the core portion (inner layer portion).

Therefore, it is considered that the linear expansion coefficient of the polypropylene resin molded product can be further reduced as compared with the conventional one. As described above, according to the present invention, dimensional stability,
It is possible to provide a polypropylene resin molded product having excellent mold releasability during injection molding and molding processability.

[0033]

EXAMPLES Examples according to the present invention will be described below together with comparative examples. [Sample preparation and measurement method] In each of the examples and comparative examples, the sample No. Except E15, polypropylene resin (PP) shown in Table 1 and EPR (ethylene-propylene rubber) as an amorphous ethylene-α olefin copolymer (EO copolymer) shown in Table 2 were used. still,
In E15, an ethylene-butene copolymer was used.

Then, these two components and talc were mixed at the compounding ratios shown in Tables 3 to 7. Mixing was performed for 5 minutes with a tumbler type blender. Next, these mixtures were melt-kneaded and pelletized. In kneading, a rubber softening agent such as paraffin oil was added in an amount of 1 to 15 parts by weight, if necessary, in order to adjust the fluidity of the composition.

Next, the above pellets are length L / diameter D = 3
It was fed to the most downstream part (end) of the screw of a 0 mm counter-rotating twin-screw extruder. Then, after melt-kneading, pellets of polypropylene resin composition were obtained. In the above,
The setting temperature at the time of kneading is 220 ° C, the extrusion rate is 7 to 8 kg / H.
r, the screw rotation speed was 100 rpm.

After hot-drying the above composition pellets for 8 hours, a test piece having a predetermined shape was prepared by injection molding.
This was used as a sample. The test piece was molded using an 80-ton injection molding machine with an injection time of 10 seconds and a resin temperature of 210-2.
It was set to 20 ° C.

The measuring method of various physical properties, the evaluation method and each component are shown below or in the lower column of the table. -Releasability The surface of the molding die was evaluated with and without wrinkles (rough surface) and without (mirror surface). In the evaluation, when the releasability was extremely excellent, it was marked with ◯, when it was excellent with ◯, when it was not suitable for practical use, it was marked with Δ, and when it was not significantly applied, it was marked with x.

Appearance of molded product The appearance of the obtained polypropylene resin molded product was evaluated.
In the evaluation, ◎ when the appearance is extremely excellent,
The case where it was excellent was evaluated as ○, the case where the appearance was poor and not suitable for practical use was evaluated as △, and the case where it was not significantly suitable was evaluated as ×.

Linear expansion coefficient Tested according to ASTM-D696. Bending elastic modulus, bending strength Tested according to ASTM-D790.

The following components were used as the components in each example. -Polypropylene resin 7 types of ethylene content (weight%) shown in Table 1 were used.

Amorphous ethylene-α olefin copolymer The ethylene / propylene copolymer (EPR) shown in Table 2 was used.・ Inorganic filler talc

Table 3 and FIG. 1 show low molecular weight EPR (hereinafter,
It is called L-EPR. ) And the high molecular weight EPR in the EPR (hereinafter referred to as H-EPR). Table 4 shows the evaluation results of examining the weight average molecular weights of L-EPR and H-EPR.

Table 5 shows the evaluation results of the EPR content (EPR / (PP + EPR)) in the polymer component and the talc content in the polypropylene resin molded product. Table 6 shows the evaluation results of examining the ethylene content in PP.

Table 7 shows the evaluation results of the investigation of α-olefins in the low molecular weight EO copolymer and the investigation of the relationship between the contents of EPR (C) and talc (D). Figure 5 shows Table 5
7 is a graph showing the relationship between the linear expansion coefficient and the EPR content (C) in the polymer component and the talc content (D) in the polypropylene resin molded product in Table 7.

In Tables 1 to 7, (+) indicates a case where the numerical range of the present invention was exceeded and (-) indicates a case where the numerical range was not satisfied. In addition, in the same table, the content of each composition ratio is shown in parts by weight or wt%. In addition, in Table 1 and Tables 3 to 7,
Samples A, B, C, D and E show PP according to the present invention, and samples CF and CG show PP as a comparative example.

In Tables 2 to 7, samples LH, LI, L
J and LO are L-EPRs according to the present invention, and are samples HK and H.
L and HM represent H-EPR as the present invention, and sample CN represents H-EPR as a comparative example. In addition, in Table 3 to Table 7,
Sample No. Sample Nos. E1 to E15 are polypropylene resin molded products according to the examples of the present invention. C1 to C15 represent polypropylene resin molded articles as comparative examples.

In the table, the compounding ratio of each composition is shown by wt% in the polypropylene resin molded product. Further, in the table, H / (H + L) indicates the content (wt%) of H-EPR in the EPR, and EPR / (PP + EPR) indicates the content (part by weight) of the EPR in the polymer component.

In the table, D> 155-37InC
Indicates the relationship between the EPR content (C) in the polymer component and the talc (inorganic filler) content (D) in the polypropylene resin molded product according to the present invention. "○", and "X" when not satisfied.

As is known from Tables 3 to 7 and FIGS. 1 and 2, Examples E1 to E15 according to the present invention have a linear expansion coefficient of 5.00 × 10 ⁻⁵ cm / cm / ° C. or less and a bending strength. Is 1
35 kg / cm ² or more, flexural modulus of 9000 kg / c
m ² or more. In comparison, comparative examples C1 and C
2, C6, C9, C10 and C12 were not favorable in releasability. Comparative examples C4, C5, C7, C9, C11 are
The appearance of the molded product was not favorable. Comparative Examples C3, C4, C
5, C7, C8, C11, C13 to C15 had a coefficient of linear expansion higher than 5.0 × 10 ⁻⁵ cm / cm / ° C. and had a problem in dimensional stability.

As shown in FIG. 2, the relationship between the talc content (D) and the EPR content (C) is set in order to keep the linear expansion coefficient at 5.0 × 10 ⁻⁵ cm / cm / ° C. or less. Is D>
It can be seen that it is necessary to satisfy 155-37InC. As described above, according to the present invention, a polypropylene resin composition having a low linear expansion coefficient, a high bending strength and a high bending elastic modulus, and excellent dimensional stability, releasability during injection molding, and molding processability. Can be obtained.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

[0054]

[Table 4]

[0055]

[Table 5]

[0056]

[Table 6]

[0057]

[Table 7]

[Brief description of drawings]

FIG. 1 is a graph showing the evaluation results of the content of H-EPR and L-EPR and the linear expansion coefficient of a polypropylene resin molded product.

FIG. 2 is a graph showing the relationship between the contents of EPR and talc within the scope of the present invention.

Claims (1)

[Claims] 1. A melt flow rate (X) of 10 to 60.
45 to 70 parts by weight of a polypropylene resin containing g / 10 minutes and 0 to 8 wt% of ethylene, and 55 to 30 parts by weight of an amorphous ethylene-α olefin copolymer (hereinafter referred to as an EO copolymer). Polymer component consisting of 6
5 to 95 wt% and the inorganic filler is 5 to 35 wt%, and the relationship between the content (C) of the EO copolymer and the content (D) of the inorganic filler is D> 155-37I.
nC polypropylene resin molded product, wherein
The O copolymer includes a high molecular weight EO copolymer having a weight average molecular weight of 380,000 to 1,000,000 and 30 to 60 wt% and a low molecular weight EO copolymer having a weight average molecular weight of 150,000 to 330,000 and 70 to 40 wt.
% And has a linear expansion coefficient of 5 × 10 ⁻⁵ cm / cm
/ ° C or less, a polypropylene resin molded product.