JPH0359049A - Polyolefin composition for large blow molding - Google Patents

Abstract

PURPOSE:To provide the title composition excellent in drawdown resistance, coatability, impact resistance, etc., by mixing polypropylene, polyethylene and ethylene/alpha-olefin copolymer rubber, each specified in properties such as a melt flow index, together in a specified mixing ratio. CONSTITUTION:40-80wt.% polypropylene of a melt flow index <=0.7g/10min is mixed with 5-35wt.% polyethylene of a melt flow index <=0.2g/10min and 15-25wt.% ethylene/alpha-olefin copolymer rubber of a melt flow index <=1g/10min (e.g. ethylene/propylene copolymer rubber). In this way, a polypropylene composition having a melt flow index <=0.3g/10min and is desirable for long large blow moldings which need be painted, such as automobile exterior furnishings and bumpers.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for large-sized blow-molded products that exhibits good drawdown resistance when forming large-sized blow-molded products and has improved surface quality and paintability. The present invention relates to polyolefin compositions.

[Conventional technology]

Resins used for blow molding generally need to have excellent drawdown resistance, and high-density polyethylene, which has this feature, is widely used.

However, although high-density polyethylene has excellent drawdown resistance, there is a problem in that it is not very suitable when the surface quality of the blow-molded product is very important. Therefore, high-density polyethylene has conventionally been mainly used for drum cans, gasoline tanks, boats, solar tanks, and the like.

On the other hand, although polypropylene has excellent surface quality, it has poor drawdown resistance, and when used for long objects of about 1.5 m or more, the uniformity of the wall thickness becomes poor. Further, during blow molding, there is a problem that a difference in surface quality tends to appear between the part that is hit first and the part that is hit after the mold. Therefore, it is not particularly suitable for large-sized blow molded products by itself.

Therefore, various polyolefin compositions have been proposed, which are based on high-density polyethylene and polypropylene and have an ethylene-α olefin copolymer rubber added thereto as a third component.

For example, JP-A-59-199740 discloses (a) 50 to 90% by weight of high-density polyethylene with a melt index of O, 1 g/10 min or less, (b) crystalline polypropylene 10 with a melt flow index of Ig/10 min or less. ~50
Weight %, (c) Ethylene-α olefin copolymer rubber 5
-10% by weight, and (d) 0-30% by weight of mica.

In addition, Japanese Patent Publication No. 64-6657 discloses (a) high-density polyethylene 50 with a melt index of 0.5 g/10 minutes or less.
~93% by weight, (0) 5 to 50% by weight of crystalline polypropylene with a melt flow index of 0°5 g/10 minutes or less, and (c) a melt flow index of 1.0 g/10 min.
Ethylene-α olefin co-electropolymer rubber 2 to 10 minutes or less
20% by weight.

Furthermore, Japanese Patent Publication No. 62-28174 discloses (
1) Crystalline ethylene with a melt flow index of 0.5 to 20 g/10 min and an ethylene content of 20% by weight or less
Propylene block copolymer 20-79% by weight, (2)
20 to 50% by weight of ethylene-propylene copolymer rubber or ethylene-propylene-diene terpolymer rubber having a Mooney viscosity of 10 to 120, and (3) an aspect ratio of 3 or more and an average particle diameter of 0. The present invention discloses a thermoplastic resin composition comprising 1 to 30% by weight of talc having an average particle size of 5 to 15 microns, mica having an average particle size of 1 to 200 microns, or fibrous crystalline calcium silicate having an average particle size of 1 to 100 microns. This document also describes in comparative examples 60% ethylene-propylene block copolymer, 10% BPR, and 30%
)l[]PB is shown.

[Problem to be solved by the invention]

However, the above two polyolefin compositions (JP-A-59-199740 and JP-B-64-6657) have excellent drawdown resistance because they are based on high-density polyethylene; It was found that there were some problems with surface quality when used for long products of about 2 m. Therefore, there is still room for improvement for use in automotive exterior parts, etc., which have strict surface quality requirements.

On the other hand, the thermoplastic resin composition of Japanese Patent Publication No. 62-28174 contains 20 to 50% by weight of ethylene-propylene copolymer rubber or ethylene-propylene-diene terpolymer rubber, so it is good. It exhibits good impact resistance and paintability, but if polyethylene is not blended, the drawdown resistance is insufficient, so it is not suitable for large-sized blow molded products. Further, even when polyethylene is blended, the melt index of the composition described in the specification is relatively large, so there remains the problem that drawdown resistance is insufficient when large-sized blow-molded products are formed.

Various engineering plastics such as polyphenylene oxide and nylon have come to be used as resins for large blow-molded products such as spoilers, but they have the problem of high material cost.

Therefore, there is a need for a polyolefin composition for large blow-molded products that is based on polypropylene and has good surface quality and excellent paintability while overcoming its drawback of drawdown property.

It is therefore an object of the present invention to provide an inexpensive polyolefin composition for large blow molded articles that exhibits good drawdown resistance, surface quality and paintability.

[Means to solve the problem]

As a result of intensive research in view of the above objectives, the present inventors have discovered that polypropylene is used as a base material to provide molded products with good surface quality, polyethylene has the effect of improving drawdown resistance, and ethylene has the effect of making the two compatible. The inventors have discovered that a polyolefin composition for large-sized blow molded products that can achieve the above objectives can be obtained by blending an appropriate amount of α-olefin copolymer rubber, and have conceived the present invention.

That is, the polyolefin composition for large blow molded products of the present invention has (a) a melt flow index of 0.7 g;
(a) 5-35% by weight of polyethylene with a melt index of 0.2g/10min or less; (c) 1% by weight of polyethylene with a melt index of 0.2g/10min or less; Contains more than 15% by weight and not more than 25% by weight of ethylene-α olefin copolymer rubber of Og/10 minutes or less, and 0
．． It is characterized by having a melt index of 3 g/10 minutes or less.

Another polyolefin composition for large blow molded products of the present invention has a melt flow index of 0.7 g/10
(c) 40-80% by weight of polypropylene with a melt index of 0.2g/10min or less; (c) 5-35% by weight of polyethylene with a melt index of 0.2g/10min or less;
g/10 minutes or less of ethylene-α olefin copolymer rubber exceeding 15% by weight and not more than 25% by weight, and (a) average particle size of 3
Contains 5-25% by weight of talc of 0.3g or less
It is characterized by having a melt index of /10 minutes or less.

The present invention will be explained in detail below.

The polypropylene used in the present invention is generally crystalline polypropylene, with a melt flow index (MPI: JI
The material is not limited to a homopolymer, but may be a block copolymer or a random copolymer with ethylene, as long as it is 0.7 g/10 minutes or less (measured using S6758 at a temperature of 230° C. and a load of 2.16 kg). In the case of copolymers, the ethylene content is preferably 10 mol% or less. If the MFI of polypropylene is greater than 0.7 g/10 minutes, the drawdown in the blow mold will be severe, making it difficult to form the bottom of a large blow-molded product with a long parison. Preferred MPI
is between 0.2 and 045, especially between 0.3 and 0.4.

Polyethylene has a melt index (Ml: JISK6
760 at a temperature of 190° C. and a load of 2.16 kg) is required to be 0.2 g/10 minutes or less.

As long as this condition is satisfied, the material is not limited to high-density polyethylene, but may be low-density polyethylene or linear low-density polyethylene. Note that when the Ml of polyethylene exceeds 0°2 g/10 minutes, the drawdown resistance decreases. Preferred Ml
is 0.01 to 0.1 g/10 minutes.

In addition to the homo-type polyethylene, polyethylene of a type copolymerized with a comonomer such as butene-1, hexene-1, etc. can also be used. Generally, the former is used for the purpose of improving rigidity, and the latter is used for the purpose of preventing stress cracking.

The ethylene-α-olefin copolymer rubber used in the present invention includes ethylene and α-olefin, such as haflopyrene,
A copolymer rubber containing butene-11hexene-t1tctene-1, etc., a copolymer rubber of ethylene and α-olefin, or a non-conjugated diene as a third component in the ethylene-propylene system, such as ethylidene norbornene, di Examples include terpolymer rubber (hereinafter referred to as BPDM), which is a copolymer of cyclopentadiene, 1,4-hexadiene, and the like.

Among these, ethylene-propylene copolymer rubber (hereinafter referred to as BPR) or BPDM is preferred.

These ethylene-α olefin copolymer rubbers are MI
(190°C, 2.16 kg) is required to be 1.0 g/10 minutes or less. If the weight exceeds 1.0 g/10 minutes, the drawdown resistance decreases. The preferred old is 0. l~
It is 0.7g/10 minutes.

The ethylene-α olefin copolymer rubber has an ethylene content of 20 to 90% by weight and a Mooney viscosity (according to JIS -
6300ML, 100℃ or less) is 60~100
It is preferable that If the ethylene content in the copolymer rubber is less than 20% by weight or more than 90% by weight, the rubber properties will be insufficient and the impact strength of the resulting molded product will be reduced. Furthermore, if the Mooney viscosity of the copolymer rubber is outside the above range, the compatibility between polypropylene and polyethylene during kneading will deteriorate, and this is also undesirable for the drawdown resistance of the composition.

In the polyolefin composition of the present invention, the content of polypropylene is 40 to 80% by weight, the content of polyethylene is 5 to 35% by weight, the content of ethylene-α olefin copolymer rubber is more than 15% by weight, and the content of polyethylene is more than 15% by weight. % by weight or less.

If the amount of polypropylene is 40% by weight, the surface quality of the blow-molded product will be poor, and if it exceeds 80% by weight, the drawdown resistance will decrease. The preferred polypropylene content is 45 to 70% by weight.

If the amount of polyethylene is less than 5% by weight, the effect of improving drawdown resistance will not be sufficient, and if it exceeds 35% by weight, a decrease in surface quality will be observed. The preferred polyethylene content is 10 to 30% by weight.

If the amount of ethylene-α-olefin copolymer rubber is less than 15% by weight, the paintability of the resulting composition will be low, and if it exceeds 25% by weight, not only will the paintability not be further improved, but the heat resistance will be poor. A problem arises in that the rigidity is reduced. The preferred content of the ethylene-α olefin copolymer rubber is 20 to 25% by weight.

The composition of the present invention consisting of such components has a content of 0°3g/
It has a melt index of 10 minutes or less.

When the melt index of the composition is greater than 0.3 g/10 minutes, the drawdown resistance is insufficient.

Another polyolefin composition of the present invention has a polyolefin composition of 40 to 8
0% by weight polypropylene, 5-35% by weight polyethylene and more than 15% by weight but not more than 25% by weight ethylene-
It is characterized by containing 5 to 25% by weight of talc (average particle size of 3 μm or less) in addition to the α-olefin copolymer rubber. Talc has the effect of improving heat-resistant stiffness, and compensates for the heat-resistant stiffness reduced by the addition of the ethylene-α-olefin copolymer rubber.

Regarding the average particle size, if it exceeds 3 μm, the surface properties of the composition will deteriorate, so it is necessary to use talc having an average particle size of 3 μm or less. The preferred average particle size of talc is 2
It is less than μm. If the talc content is less than 5% by weight, a sufficient effect of improving heat resistance and stiffness cannot be obtained. but,
If it exceeds 25% by weight, the surface properties and impact resistance of the composition will decrease.

The composition of the present invention can be prepared by blending the above-mentioned components and kneading them in a heated molten state using a kneading machine such as a high-speed mixer, a Banbury mixer-1 continuous kneader, or a single- or twin-screw extruder. can get.

In addition to the above-mentioned components, the composition of the present invention may contain various additives such as antioxidants, ultraviolet absorbers, stabilizers, lubricants, antistatic agents, electrical property improvers, flame retardants, processability improvers, and pigments. Additives can be added.

The polyolefin composition of the present invention thus obtained is suitable for large-sized blow-molded products, particularly long products of 2 m or more.

〔Example〕

The present invention will be explained in further detail by the following examples.

In addition, the test method of the characteristics of the composition in the examples is as follows.

(1) Evaluation of drawdown resistance Large-sized blow molding machine (manufactured by Ishikawajima Harima Heavy Industries ■, IPB-20
0C), length 2.0m, width 0.16m, weight 4
kg bumper is molded, and the ratio of the upper wall thickness to the lower wall thickness is 0.6 to 1.0: ○; when it is less than 0°6,
Both cases of poor molding and cases where molding was impossible were rated as ×.

(2) Evaluation of surface quality The above bumper was measured using a surface roughness meter, and when the average value of the surface roughness at 10 measurement points was 20 μm, the O
The case of 20 μm or more was marked as ×.

(3) Heat distortion temperature JIS K7207, load 4.6kg/cd0 (4)
According to Izot impact strength ASTM 0256, -30
Measured in °C.

(5) Apply paintable lacquer paint with 1 coat/1 bake, l 0m
A square area was marked with 100 base marks using a cutter, and a base mark peeling test was performed.If the number of base marks peeled off was 20/100 or less, it was rated as 0; otherwise, it was rated as ×.

Examples 1 to 7 Crystalline polypropylene (PP: MFI 0.4 g/1
0 minutes), high density polyethylene (HDPB: density Q, 94
5 g/ctl, formerly 0.04 g/10 min), ethylene-propylene copolymer rubber (BPR: ethylene content 73 wt%, Mooney viscosity 70, MlO, 7 g/
10 minutes), or these and talc (average particle size 2 μm) are blended in the combinations shown in Table 1, mixed in a mixer, and the resulting mixture is melt-kneaded in a twin-screw kneading extruder set at a temperature of 220°C. After that, it was made into a beret. Using the obtained pellet, a bumper with a length of 2 m, a width of 0.16 m, and a weight of 4 kg was blown and evaluated for drawdown resistance. In addition, surface roughness (representing surface quality), Izot impact strength, and heat distortion temperature were measured using test pieces cut out from the bumper, and paintability was evaluated by a base grain test. The results are shown in Table 1.

Comparative Examples 1 to 8 Test pieces were prepared and evaluated in the same manner as in the Examples, except that the amounts of polypropylene, high-density polyethylene, BPR, and talc were variously changed. The results are shown in Table 'M1.

Comparative Example 9 Polypropylene with a melt flow index of 1.
A test piece was prepared in the same manner as in the example except that one with a weight of 0 g/10 minutes was used, and the same evaluation was performed. The results are shown in Table 1.

Comparative Example 10 A test piece was prepared in the same manner as in the example except that HOPE having a melt index of OJg/10 minutes was used, and the same evaluation was performed. The results are shown in Table 1.

Comparative Example 11 Except for using talc with an average particle size of 5 μm,
Test pieces were prepared in the same manner as in the examples and evaluated in the same manner. The results are shown in Table 1.

From the above results, the following can be understood.

(1) When the proportion of polypropylene is 40% by weight,
Poor surface quality (Comparative Example 7).

(2) When the MPI of polypropylene exceeds 0.7 g/10 minutes, drawdown resistance is low (Comparative Example 9).

(3) When the proportion of HDPEI is 5% by weight, the drawdown resistance is low (Comparative Example 8).

(4) When Ml on day II D P exceeds 0.2 g/10 minutes, drawdown resistance is low (Comparative Example 10).

(5) In order to improve paintability, it is necessary to add more than 15% by weight of 8PR.

(6) When 8PR is in the range of more than 15% by weight and less than 25% by weight, adding an appropriate amount of talc (5 to 25% by weight) improves heat resistance and provides a good balance between surface properties and impact resistance. It becomes a material (Examples 4 to 7).

(7) Adding more than 25% by weight of BPR will result in poor heat-resistant rigidity, and even if talc is added to improve heat-resistant rigidity, talc will be incorporated into BPH, resulting in poor heat-resistant rigidity. There is almost no improvement (Comparative Examples 5 and 6).

(8) When talc is added in an amount exceeding 25% by weight, surface properties and impact resistance become poor (Comparative Example 4).

(9) When the average particle size of talc exceeds 3 μm, surface quality deteriorates (Comparative Example 11).

As is clear from the above results, when polypropylene, polyethylene, and ethylene-α-olefin copolymer rubber are within the scope of the present invention, drawdown resistance, surface quality, heat distortion temperature, and Izot impact strength are all improved. A composition is obtained which is satisfactory and has improved paintability. Furthermore, by containing talc, it is possible to compensate for the decrease in heat resistance rigidity caused by the addition of the ethylene-α olefin copolymer rubber.

〔Effect of the invention〕

As detailed above, the polyolefin composition of the present invention has good drawdown resistance and surface quality, and is also excellent in heat-resistant rigidity and impact resistance, so it is particularly suitable for large-scale blow molding of long objects. suitable for the product. Furthermore, since the paintability has been improved, it is possible to write on or paint with lacquer paint, urethane paint, etc. Therefore,
It can be suitably used for large blow-molded long objects such as automobile exterior parts and bumpers that require painting.

Claims (2)

[Claims] (1) (a) Melt flow index is 0.7g/1
(b) 40-80% by weight of polypropylene of 0 min or less;
5 to 35% by weight of polyethylene with a melt index of 0.2 g/10 minutes or less, and (c) a melt index of 1
．． 0g/10min or less of ethylene-α olefin copolymer rubber exceeding 15% by weight and not more than 25% by weight;
A polyolefin composition for large blow molded products, characterized by having a melt index of 3 g/10 minutes or less. (2) (a) Melt flow index is 0.7g/1
(b) 40-80% by weight of polypropylene of 0 min or less;
5 to 35% by weight of polyethylene with a melt index of 0.2 g/10 minutes or less, and (c) a melt index of 1
．． 0g/10min or less of ethylene-α olefin copolymer rubber exceeding 15% by weight and not more than 25% by weight, and (d) 5 to 25% by weight of talc having an average particle size of 3 μm or less;
A polyolefin composition for large blow molded products, characterized by having a melt index of 3 g/10 minutes or less.