JPH0655863B2 - Polyolefin resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyolefin resin composition, more specifically, a polyolefin resin having high rigidity and impact strength and an excellent surface appearance, which is suitable as a material for the automobile field and the like. It relates to a resin composition.

[Prior Art and Problems to be Solved by the Invention] In order to improve the impact resistance of polypropylene, resin compositions to which various elastomers are added are used in various industrial fields. Among them, for example, bumper materials for automobiles. Is often used as.

However, recently, with the increase in size of parts and the streamlining of shapes, it is necessary to improve the rigidity of materials.

Therefore, a resin composition further containing a tabular filler such as talc is used.

However, even if talc is added, not only the effect of improving rigidity is limited, but also flow marks are liable to occur in the molded product, the weld appearance and weld strength are lowered, and the surface gloss is deteriorated. Dots occur.

In order to solve these problems, when glass fiber is blended, it is possible to improve the rigidity of the resin composition, but a large drop in impact strength and a marked drop in appearance occur, making it suitable for practical use. I can't stand it. In addition, when an amorphous (spherical, cubic, coagulated) inorganic filler typified by calcium carbonate is blended, the problems of weld appearance or weld strength and flow marks are solved, but the improvement of rigidity is There is no reason to reach talc.

The object of the present invention is to improve the rigidity without lowering the impact strength to the extent that it cannot be practically used, and also to improve the weld strength, the weld appearance, the surface appearance, and the polyolefin resin composition in which flow marks are hard to occur. To provide.

[Means for Solving the Problems] The present invention for solving the above problems includes a thermoplastic elastomer of 60 to 90% by weight, a thermoplastic elastomer selected from the group consisting of ethylene elastomers and styrene elastomers, and 10 to 40% by weight. Of the mixture of the polyolefin resin and the melt index (hereinafter sometimes abbreviated as MI) of the polyolefin resin, and the MI of the mixture of the polyolefin resin and the thermoplastic elastomer selected from the group consisting of the ethylene elastomer and the styrene elastomer. 100 parts by weight of a resin composition having a ratio adjusted to 0.25 or more, and 5 to 50 parts by weight of fibrous calcium carbonate having an average fiber diameter of 3 μm or less and an average aspect ratio of 15 or more are mixed. It is a polyolefin resin composition.

Hereinafter, the polyolefin resin composition of the present invention will be described in detail.

-Polyolefin resin-As the polyolefin resin in the present invention, polypropylene, polypropylene such as propylene-ethylene block copolymer and propylene-ethylene random copolymer, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene. Such as polyethylene; ethylene-propylene copolymer, ethylene-
Ethylene-α-olefin copolymers such as butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer; ethylene containing propylene-butene 1 copolymer, cyclopentadiene and the like. -Propylene-olefin copolymers such as propylene-diene copolymers; polybutene-1; poly-4-methyl-pentene-3 and the like can also be used in the present invention. The polyolefin resins listed above can be used in appropriate combination of two or more kinds.

From the viewpoint of the production method, a polyolefin obtained by using a Ziegler-Natta catalyst and a multi-stage polymerization method of two stages or three stages or more can also be used.

A method for producing, for example, a so-called propylene-ethylene block copolymer by this multistage polymerization method will be described below.

That is, for example, in the presence of a Ziegler-Natta catalyst, for example, the propylene monomer in the first stage is polymerized to obtain a polypropylene homopolymer, and then the propylene monomer is removed or not removed, and in the presence of ethylene in the second stage and thereafter. Alternatively, polypropylene can be produced by carrying out a polymerization reaction in the coexistence of ethylene and propylene. The pressure in the reaction in each stage may be several atm to 40 atm, and the temperature may be room temperature to 80 ° C. Further, as the polymerization reaction type, solution polymerization, slurry polymerization, gas phase polymerization, a combination method thereof or the like can be adopted.

In the present invention, among the above-mentioned various polyolefins, so-called propylene-ethylene block copolymers produced by a multistage polymerization method, polypropylene homopolymers and the like are preferable, and further, the ethylene content is 4 to 10
A so-called ethylene-propylene block copolymer having a MI of 5 or more, especially 8 to 50 g / 10 minutes in weight% is preferable.

—Thermoplastic Elastomer— Examples of the thermoplastic elastomer in the present invention include thermoplastic elastomers selected from the group consisting of ethylene elastomers and styrene elastomers.

Examples of the ethylene elastomer include ethylene-propylene rubber, ethylene-propylene-non-conjugated diene rubber, ethylene-1-butene rubber, ethylene-isobutylene rubber, polyisobutylene, and mixtures thereof. Among these rubber-like elastic bodies, ethylene-propylene rubber and ethylene-propylene-containing ethylene: propylene having a molar ratio of 5: 1 to 1: 3.
Non-conjugated diene rubber and the like are preferable.

The non-conjugated diene is selected from norbornene, liquid dienes, aliphatic dienes, and the like. 5-ethylidene-2
-Norbornene and dicyclopentadiene are preferable, and the ratio thereof is preferably 40 or less in terms of iodine value.

The ethylene elastomer used in the present invention has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 10 to 100, especially 20.
It is desirable to be 90.

Examples of the styrene elastomer include styrene-butadiene block copolymer rubber (SB, SBS, BSB), rubber obtained by partially or completely hydrogenating the butadiene portion of the styrene-butadiene block copolymer (SEBS), styrene-isoprene. Examples include rubber (SEP, SEPS) partially or completely hydrogenated in the isoprene portion of the block copolymer, maleic anhydride-modified SBS, maleic anhydride-modified SEBS, maleic anhydride-modified SEP, maleic anhydride-modified SIS, etc. .

In the present invention, two or more kinds of ethylene-based elastomers and styrene-based elastomers may be appropriately combined and used, and the ethylene-based elastomer and styrene-based elastomer may be used in combination with each other.

-Resin composition-The polyolefin resin composition of the present invention is prepared by mixing the above-mentioned polyolefin resin and a thermoplastic elastomer selected from the group consisting of ethylene-based elastomers and styrene-based elastomers in a specific ratio and adjusting to a specific MI. Another resin composition is essential.

The resin composition comprises 60 to 90% by weight, particularly 65 to 85% by weight of the polyolefin resin, and 40 to 10% by weight, particularly 35 to 35% by weight of a thermoplastic elastomer selected from the group consisting of the ethylene elastomer and the styrene elastomer. 15% by weight and the MI of the polyolefin resin
The MI ratio of the mixture of the polyolefin resin with the thermoplastic elastomer selected from the group consisting of the ethylene-based elastomer and the styrene-based elastomer (the former is A and the latter is B / A) is 0.25 or more,
It is particularly preferably adjusted to 0.30 to 0.85.

Therefore, in the present invention, the case where the polyolefin resin and the thermoplastic resin are simply mixed so as to fall within the above range, or the mixture of the polyolefin resin and the thermoplastic elastomer is within the range of the MI is not sufficient. However, the object of the present invention cannot be achieved. The object of the present invention is achieved only when the mixing ratio of the polyolefin resin to the thermoplastic elastomer selected from the group consisting of ethylene-based elastomers and styrene-based elastomers and the MI of the mixture are within the above range. It is worth noting that it can be achieved.

When the blending ratio of the thermoplastic elastomer selected from the group consisting of ethylene elastomer and styrene elastomer is less than 10% by weight, the impact strength at low temperature of the polyolefin resin composition is lowered, and the ethylene elastomer and styrene elastomer are also reduced. 40% by weight of thermoplastic elastomer selected from the group consisting of elastomers
If the amount exceeds the range, the rigidity becomes low and flow marks are easily generated in the molded product.

When B / A is less than 0.25, flow marks are apt to occur in the molded product, and the weld appearance also deteriorates.

This resin composition has the above-mentioned limited contents,
A polyolefin resin is mixed with a thermoplastic elastomer selected from the group consisting of ethylene-based elastomers and styrene-based elastomers.

The mixing method is not particularly limited, and a generally known method such as a mixing method using a kneader can be appropriately adopted.

—Fibrous Calcium Carbonate— The polyolefin resin composition of the present invention is formed by mixing the resin composition and a specific fibrous calcium carbonate in a specific blending ratio.

The fibrous calcium carbonate needs to have a fiber diameter of 3 μm or less and an average aspect ratio of 15 or more, and particularly preferably an average fiber diameter of 1 μm or less and an average aspect ratio of 20 or more.

In the present invention, by incorporating calcium carbonate having a conventional shape such as an amorphous shape, a cubic shape, and a spindle shape, the object of the present invention cannot be achieved, and even if fibrous calcium carbonate is added, Even if compounded, if the average fiber diameter exceeds 3 μm, the effect of improving the rigidity of the polyolefin resin composition becomes small, and the impact strength decreases, and the appearance deteriorates. Further, when the average aspect ratio is less than 15, the effect of improving rigidity becomes small.

The compounding ratio of fibrous calcium carbonate to the resin composition should be 5 to 50 parts by weight, preferably 10 to 40 parts by weight with respect to 100 parts by weight of the former.

This is because when the blending ratio of fibrous calcium carbonate is less than 5 parts by weight, the effect of improving the rigidity of the polyolefin resin composition is poor, and when it exceeds 50 parts by weight, the impact strength is markedly reduced. .

-Polyolefin resin composition-As long as the polyolefin resin composition of the present invention does not impair the object of the present invention, a known filler, if necessary,
It may contain one kind or two or more kinds of additives and the like.

For example, talc, barium sulfate, calcium carbonate (amorphous, cubic, spindle-shaped), gypsum, carbon black, titanium oxide, quartz powder, etc. as fillers; heat stabilizers, lubricants, surface treatment agents as additives Dispersant, antioxidant, ultraviolet ray, absorber, antistatic agent, weather resistance agent, flame retardant,
A colorant or the like can be contained.

In producing the polyolefin resin composition of the present invention, the above-mentioned respective components are blended in a predetermined amount, preliminarily blended with a ribbon blender, a V-type blender or the like, and uniformly mixed with a kneader to obtain a powdery or granular composition. can do.

Alternatively, a predetermined amount of a composition of a polyolefin resin and a thermoplastic elastomer selected from the group consisting of ethylene-based elastomers and styrene-based elastomers, and a predetermined amount of fibrous calcium carbonate are separately separated, and from the extrusion port of the kneader A material supply port (first hopper) located at a distant position is supplied with a blend of a polyolefin resin and a thermoplastic elastomer selected from the group consisting of ethylene-based elastomers and styrene-based elastomers, and a material supply located near the extrusion port. The fibrous calcium carbonate was supplied to the mouth (second hopper), and when the composition was pushed forward by the screw into a molten state, the fibrous calcium carbonate was introduced from the second hopper to change the contents of the kneader. The polyolefin resin composition can be obtained by uniformly mixing. To maintain the shape of the fibrous calcium carbonate and bring out the effect of the polyolefin resin composition,
Such latter kneading method is preferred.

The polyolefin resin composition of the present invention includes injection molding, extrusion molding, hollow molding, compression molding, lamination molding, roll molding,
A molded product can be obtained by various molding methods such as stretch molding and stamping.

Molded articles obtained from the polyolefin resin composition of the present invention are not only highly rigid and excellent in impact resistance, but also excellent in weld strength and appearance, and are excellent in that flow marks are unlikely to occur. It has the characteristic

[Examples] Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples.

(Examples 1 to 8) Polypropylene having the types and blending amounts shown in Table 1, a thermoplastic elastomer selected from the group consisting of ethylene elastomers and styrene elastomers, and fibrous calcium carbonate were kneaded as follows. .

A thermoplastic elastomer selected from the group consisting of polypropylene, ethylene-based elastomer and styrene-based elastomer is used for the first hopper located far from the extrusion opening of the twin-screw extruder (Model TEM-35: manufactured by Toshiba Machine Co., Ltd.). The fibrous calcium carbonate was fed to each of the second hoppers located close to each other by the separate quantitative feeder.

The contents were melt-kneaded at a kneading temperature of 230 ° C and a screw rotation speed of 500 rpm to produce pellets.

Then, the pellets were applied to an injection molding machine to prepare a flat plate 2 of 420 × 100 × 3 mm having a hole 1 of 50 × 50 mm as shown in FIG. 1, and the flow mark, weld appearance and weld strength were obtained as follows. Was evaluated.

Evaluation of flow mark: As shown in FIG. 1, the generation distance 1 of the flow mark 3 was visually measured.

Evaluation of Weld Appearance: Weld 4 was observed as shown in FIG. 1, and when it was inconspicuous, it was evaluated as ○, when it was conspicuous, it was evaluated as Δ, and when it was significantly conspicuous, it was evaluated as ×.

Weld strength measurement: 2kg at -30 ℃ as shown in Fig.1.
The DuPont impact strength was measured under the conditions of load and impact core 1/2.

On the other hand, a test piece was prepared from the flat plate, the Izod impact strength was measured in accordance with JIS K 7110 with a notch in an atmosphere of −30 ° C., and the flexural modulus was measured in accordance with JIS K 7203.

Regarding the measurement of the MI of the polyolefin resin and the MI of the mixture of the resin and the thermoplastic elastomer selected from the group consisting of the ethylene-based elastomer and the styrene-based elastomer prior to the kneading of the respective components, JIS K 7210 ( 230 ° C, 2,160g).

The results of these measurements are shown in Table 1.

(Comparative Examples 1 to 7) The thermoplastic elastomer selected from the group consisting of polypropylene, ethylene elastomer and styrene elastomer in the types and blending amounts shown in Table 1 and the inorganic filler were used in Example 1 above. The polyolefin resin composition was evaluated in the same manner as in Example 1 except that the first hopper of the axial extruder was supplied in a fixed amount and the mixture was melt-kneaded.

The results are shown in Table 2.

(Evaluation) As is clear from Table 1, all of the polyolefin resin compositions of Examples 1 to 8 satisfy the conditions of the present invention, and therefore have excellent rigidity, weld strength, weld appearance, and impact resistance. Moreover, there are few flow marks.

On the other hand, as shown in Table 2, since the polyolefin resin compositions in Comparative Examples are out of the conditions of the present invention, it is clear that one of the physical properties is significantly inferior.

[Advantages of the Invention] According to the present invention, a polyolefin having improved weld strength, weld appearance and surface appearance, and having less likely to cause flow marks while improving the rigidity without lowering the impact strength to the extent that it cannot be practically used. A resin composition can be provided.

[Brief description of drawings]

FIG. 1 is a plan view of a test flat plate obtained by injection molding the polyolefin resin composition in order to investigate its physical properties.

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Claims (1)

[Claims] 1. A thermoplastic resin selected from the group consisting of 60 to 90% by weight of a polyolefin resin, an ethylene elastomer and a styrene elastomer, and 10 to 40% by weight.
A resin composition in which the melt index ratio of the mixture of the polyolefin resin and the thermoplastic elastomer selected from the group consisting of ethylene-based elastomers and styrene-based elastomers to the melt index of the polyolefin resin is adjusted to 0.25 or more. A polyolefin resin composition, characterized by being mixed with 5 parts by weight of fibrous calcium carbonate having an average fiber system of 3 μm or less and an average aspect ratio of 15 or more.