JP2003183461A - Conductive resin composition and molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin molded article which suppresses a decrease in impact strength due to the addition of a conductive material component, and has a sufficient surface resistance value with good surface appearance (good gloss, no flow mark). Obtaining a thermoplastic resin molded product containing a conductive material. SOLUTION: 10 to 80% by weight of a polypropylene resin obtained by propylene homopolymerization or random copolymerization of propylene and ethylene, and linear low density polyethylene 5 to 50 polymerized by using a metallocene catalyst as a modifier component. % Of carbon black, graphite, metal powder and whiskers thereof, metal fibers, metal oxides, and carbon fibers. And molded articles obtained using the same.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a conductive resin composition which imparts excellent impact strength and high gloss to a polypropylene resin molded product.

[0002]

2. Description of the Related Art Taking antistatic measures by incorporating a conductive material such as carbon black into a thermoplastic resin, particularly a polypropylene resin, is effective for various types of thermoplastics, especially electronic parts that are easily damaged by electrostatic discharge. It is applied to resin molded products. Polypropylene resin has many characteristics such as low specific gravity, good chemical resistance, low cost, and good moldability. Conductive containers, sheets, trays using polypropylene resin, Various molded products such as pipes are widely supplied.

[0003]

However, in the case where the conductive material is carbon black, metal powder, or conductive metal oxide powder, a considerable amount of addition is required to develop conductivity,
For example, in the case of carbon black, it is necessary to add 10 to 25% by weight to the composition of the molded product, so that there is a drawback that the flowability and impact resistance originally possessed by the polypropylene resin are significantly reduced.

As a method conventionally used to overcome this drawback, an olefin such as ethylene-propylene rubber (hereinafter abbreviated as EPR) or ethylene-propylene-diene rubber (hereinafter abbreviated as EPDM) is used in a resin composition. It is widely practiced to add impact rubber or high molecular weight polyethylene to improve impact resistance.
Flowability and surface gloss of the molded product deteriorate, especially in the case of injection molded products, short shots (molding failure phenomenon caused by the resin not flowing to the back of the molding die), flow marks, and cloudiness on the surface However, there was a drawback that the appearance deteriorated.

[0005]

Means for Solving the Problems The present inventor has found that conventional impact modifiers such as olefin rubber and polyethylene are
Conductivity of polypropylene-based resin containing a conductive material, fluidity without lowering impact resistance, maintaining the gloss of the surface of the molded article, to the above fact that the problem of the contradictory conductive resin composition cannot be solved In view of the above, the inventors have made diligent studies on a new impact modifier capable of improving the resin fluidity, improving the compatibility with the polypropylene resin, and imparting the glossiness of the surface of the molded product, and as a result, a linear chain polymerized using a metallocene catalyst has been obtained. By adding low-density polyethylene (hereinafter abbreviated as metallocene LLDPE) to the conductive resin composition as an impact modifier, it has been possible to improve the resin fluidity and surface gloss which cannot be obtained by the conventional constitution. In particular, when the characteristics of a conventionally used olefin rubber against a system using an EPDM-containing polypropylene resin were verified, it was found that the fluidity of the compounded system having the same Izod impact strength,
It was confirmed that the surface gloss was dramatically improved.

That is, the first aspect of the present invention is a polypropylene resin 10 to 80 obtained by homopolymerization of propylene or random copolymerization of propylene and ethylene.
%, Linear low density polyethylene polymerized using a metallocene catalyst as a modifier component 5 to 50% by weight, carbon black, graphite, metal powder and its whiskers, metal fibers, metal oxides, carbon fibers 5 to 70% by weight of at least one kind of conductive material
It is a conductive resin composition comprising:

A second invention is the conductive resin composition according to the first invention, characterized in that the conductive material is carbon black.

A third aspect of the present invention is a linear low density polyethylene polymerized by using a metallocene catalyst at 230 ° C.
Melt flow rate measurement value 1 to 10 under 60 g load
0 g / 10 min. First characterized by being in the range of
Alternatively, it is the conductive resin composition according to the second invention.

A fourth aspect of the present invention is a linear low density polyethylene polymerized by using a metallocene catalyst having a density of 840 to 92.
The electroconductive resin composition according to any one of the first to third inventions, which has a bending elastic modulus of 0 to 100 kg / m ³ and a bending elastic modulus of 100 to 500 MPa.

A fifth invention is a molded article obtained by using the conductive resin composition according to any one of the first to fourth inventions.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. As the polypropylene resin used in the present invention, a commonly used resin that can measure the melt flow rate according to JIS K7210 corresponds. For example, a resin obtained by homopolymerization of propylene, a resin obtained by random copolymerization of propylene and ethylene, and the like can be mentioned. However, in order to improve impact resistance, those containing a block copolymer with ethylene or an olefinic rubber have a The wax-like polymer, which has poor gloss and poor appearance, and whose mechanical properties as a molded article cannot be expressed, is excluded because wax-like polymers whose melt flow rate is difficult to measure.

Further, the melt flow rate of the polypropylene resin (measured by the method specified in JIS K7210, measurement temperature 230 ° C., measurement load 2160 g load)
The measured values of 0.1 to 10 g / 10 min. For pipes, sheets and film molded products. , 1 for injection molded products
100 g / 10 min. The range of is desirable.

Examples of the conductive material used in the present invention include carbon black, graphite, metal powder and its whiskers, metal fibers, metal oxides, carbon fibers, etc. These are used alone or in combination of two or more kinds. it can. In order to have conductivity, particularly an antistatic function, a surface resistance value of 1 MΩ or less is required. Therefore, although powdery substances such as carbon black, graphite, and metal powder vary depending on the specific gravity of the conductive material, carbon black is 8 to 30% by weight, preferably 10 to 25% by weight, and graphite and metal powder is 30% by weight.
~ 75 wt%, preferably 40-60 wt% addition is required. In the case of whiskers and fibrous substances, it is possible to reduce the amount added above the above amount. Further, in the case of stainless fiber or carbon fiber, the surface resistance value can be set to 1 MΩ or less at 5 to 15% by weight.

The impact modifier used in the present invention includes:
Polyethylene polymerized with a metallocene catalyst is used. This resin is a copolymer of polyethylene and α-olefin, and the α-olefin is 1-butene, 1-butene.
Examples include hexene and 1-octene. In recent years, polyethylene used as the impact modifier is inexpensively polymerized by a metallocene catalyst and is being developed for various applications. Especially, metallocene LLDPE having a low crystallinity can control a narrow molecular weight distribution and has a low molecular weight. Since it can efficiently reduce the amount of substances, it has a high stickiness due to its low crystallinity, an excessive decrease in the melting point, smoke prevention during molding, etc., a high gloss compared to other thermoplastic elastomers, a good fluidity, etc. In recent years, polypropylene-based resin modifiers,
Used as an impact modifier.

The reason why excellent impact resistance, surface gloss and fluidity are exhibited by using metallocene LLDPE is considered as follows. First, the reason why metallocene LLDPE has excellent impact resistance is that metallocene LLDPE
Is a non-crosslinked resin, but fine crystals at room temperature
This is because the crystals are bonded to each other due to the presence of tie molecules, and a pseudo three-dimensional network structure is formed, which is similar to other rubber-like substances. The presence of Thai molecules is confirmed in ordinary linear low-density polyethylene, but metallocene LLDPE
It is considered that the existence probability of the above-mentioned tie molecule is as many as 2 to 4 times, and thus the impact resistance is likely to be expressed.

Secondly, the reason why the metallocene LLDPE has an excellent gloss while having an impact resistance is that the other olefin rubbers have a rubber dispersed particle diameter of several to several tens of microns, whereas the metallocene LLDPE has In this case, it is considered that there is no substance having a dispersed particle size of several to several tens of microns as seen in the polypropylene block copolymer, and therefore high gloss can be imparted without forming irregularities on the surface of the molded product. .

Thirdly, the reason why the metallocene LLDPE has excellent fluidity is that the tie molecule forming the three-dimensional network structure described in the first section exists at room temperature, but is crystallized by being heated. Disappears with the melting of
This is because it is possible to take the same behavior as normal polyethylene near the molding temperature. On the other hand, in an elastomer containing an olefin-based rubber, since the rubber remains as crosslinked particles having poor fluidity even near the molding temperature, the fluidity tends to deteriorate as the rubber compounding amount increases. Conceivable.

Metallocene LLDPE used in the present invention
Is a resin polymerized by a metallocene catalyst, and the metallocene catalyst is specifically 4 such as titanium, zirconium, nickel, palladium, hafnium, niobium and platinum.
It is the name of a catalyst in which at least one ligand having a cyclopentadienyl skeleton is coordinated with a valent transition metal.

The ligand having a cyclopentadienyl skeleton includes cyclopentadienyl group, methylcyclopentadienyl group, ethylcyclopentadienyl group, n-
Or an i-propylcyclopentadienyl group, n-,
Alkyl monosubstituted cyclopentadienyl groups such as i-, sec-, tert-, butylcyclopentadienyl group, hexylcyclopentadienyl group, octylcyclopentadienyl group, dimethylcyclopentadienyl group, methylethylcyclo Alkyl disubstituted cyclopenta such as pentadienyl group, methylpropylcyclopentadienyl group, methylbutylcyclopentadienyl group, methylhexylcyclopentadienyl group, ethylbutylcyclopentadienyl group, ethylhexylcyclopentadienyl group Alkyl polysubstituted cyclopentadienyl groups such as dienyl group, trimethylcyclopentadienyl group, tetramethylcyclopentadienyl group, pentamethylcyclopentadienyl group, cyclo-substituted hexyl groups such as methylcyclohexylcyclopentadienyl group Cyclopentadienyl group, indenyl group, tetrahydroindenyl group, fluorenyl group and the like.

Examples of the ligand other than the ligand having a cyclopentadienyl skeleton include monovalent anion ligands such as chlorine and bromine, divalent anion chelate ligands, hydrocarbon groups, alkoxides, amides, arylamides and aryloxides. Examples thereof include phosphide, arylphosphide, silyl group, and substituted silyl group. Examples of the hydrocarbon group include those having about 1 to 12 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a heptyl group, an octyl group, Alkyl groups such as nonyl group, decyl group, cesyl group, decyl group, cesyl group and 2-ethylhexyl group, cycloalkyl groups such as cyclohexyl group and cyclopentyl group, aryl groups such as phenyl group and tolyl group, benzyl group, neophyll group And aralkyl groups, nonylphenyl groups and the like.

Examples of the metallocene compound coordinated with a ligand having a cyclopentadienyl skeleton include cyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, dimethylsilyltetramethylcyclopentadienyl- pn
-Butylphenylamide zirconium chloride, methylphenylsilyl tetramethylcyclopentadienyl-t
ert-butylamido hafnium dichloride, dimethylsilyl tetramethylcyclopentadienyl-tert-
Butyramide hafnium dichloride, indenyl titanium tris (diethyl amide), indenyl titanium bis (di-n-butyl amide) indenyl titanium bis (di-n-propyl amide) and the like can be mentioned.

These polymerizations can be carried out in a catalyst system in which, for example, a metallocene catalyst containing a tetravalent transition metal as described above is added as a cocatalyst, for example, methylaminoxane or a boron compound. In this case, the ratio of these catalysts to the metallocene catalyst is preferably 1 to 1,000,000 times mol.

The conductive resin composition can be manufactured by using a method in which a thermoplastic resin is kneaded with various fillers. For example, it can be achieved by using a batch kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader such as a single-screw or twin-screw extruder, a tandem kneader, and a cokneader. It is possible to knead various powdery materials such as carbon black, whisker-like, and fibrous conductive materials by these methods, but when kneading whisker-like and fibrous conductive materials, the shape is not destroyed. It is important to knead with the resin.

When kneading, a resin antioxidant,
An ultraviolet absorber, a light stabilizer, a lubricant, and a coloring agent may be added if necessary. As the antioxidant, phenol-based, phosphorus-based, sulfur-based, lactone-based, and other antioxidants may be added alone or in combination to prevent thermal deterioration during resin processing. Further, when weather resistance is required for outdoor use, a benzophenone-based, salicylate-based, benzotriazole-based, cyanoacrylate-based, hindered amine-based compound or the like can be used as an ultraviolet absorber or a light stabilizer. As a lubricant used for imparting lubricity during kneading and molding, polyolefin wax, higher fatty acid metal salt or amide, ester compound and the like can be added. As the colorant, a pigment, which is generally used for coloring polypropylene, is easily dispersed, and a powder, liquid, or pellet may be used.

[0025]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples. Hereinafter, “part” means “part by weight” and “%” means “% by weight”. The material description, composition and properties are given in the table. [Example 1] 20% by weight of carbon, 59.8% by weight of homo PP, 20% by weight of metallocene LLDPE and 0.2% by weight of antioxidant were kneaded in a Banbury mixer, and then formed into a cylindrical pellet having a diameter of 3 mm and a length of 3 mm. Granulated. After measuring the melt flow rate of the obtained pellets at 230 ° C. under a load of 2160 g, a flat plate of 200 mm × 400 mm was prepared by an injection molding machine with a mold clamping pressure of 75 t, and the gloss and surface resistance values were measured. Furthermore, the presence or absence of flow marks was visually confirmed. At the same time, an Izod test piece having a thickness of 5 mm was molded to measure the eyed impact strength.

[Example 2] The same operation as in Example 1 was performed except that the homo PP of Example 1 was changed to a random PP.

Comparative Example 1 The same operation as in Example 1 was carried out except that the homo PP of Example 1 was changed to block PP.

Comparative Example 2 The resin component of Example 1 (homo PP
And the metallocene LLDPE) were changed to TPO, and the same operation as in Example 1 was performed.

[Comparative Example 3] Metallocene LLD of Example 1
The PE was changed to ZLDGR catalyzed polymerized LLDPE. Otherwise, the same operation as in Example 1 was performed.

Example 3 60% by weight of metal oxide, 29.8% by weight of homo PP, 10% by weight of metallocene LLDPE and 0.2% by weight of antioxidant were kneaded in a Banbury mixer, and then the diameter was 3 mm and the length was 3 mm. Granulated into cylindrical pellets. After measuring the melt flow rate of the obtained pellets at 230 ° C and a load of 2160 g, a 200 mm x 400 mm flat plate was prepared with an injection molding machine with a mold clamping pressure of 75 t, and the gloss and surface resistance values were measured. The presence or absence of the mark was visually confirmed. At the same time, an Izod test piece having a thickness of 5 mm was molded and the Izod impact strength was measured.

[Example 4] The same operation as in Example 1 was performed except that the homo PP of Example 3 was changed to a random PP.

[Comparative Example 4] The same operation as in Example 1 was performed except that the homo PP of Example 3 was changed to block PP.

Comparative Example 5 The resin component of Example 3 (homo PP
And metallocene LLDPE) to TPO. Otherwise, the same operation as in Example 1 was performed.

Comparative Example 6 Metallocene LLD of Example 3
The PE was changed to ZLDGR catalyzed polymerized LLDPE. Otherwise, the same operation as in Example 1 was performed.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3] [Explanation of Tables 2 and 3] It can be seen that, out of 10 compounding examples, the conductive resin molded products obtained in Examples 1 to 4 have high gloss and a good appearance.

The embodiments and examples disclosed this time are illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

[0039]

The conductive resin composition of the present invention is polymerized by using propylene homopolymerization, or 10 to 80% by weight of polypropylene resin obtained by random copolymerization of propylene and ethylene, and a metallocene catalyst as a modifier component. 5 to 50% by weight of linear low-density polyethylene, carbon black, graphite, metal powder and its whiskers,
Since it contains 5 to 70% by weight of at least one kind of conductive material selected from metal fibers, metal oxides, and carbon fibers, the fluidity of the conductive resin composition and the resin at the time of manufacturing the molded product becomes high, and good molding Have sex.

When the conductive material in the conductive resin composition of the present invention is carbon black, the raw material for the conductive resin molded article can be supplied at a very low cost, and thus an excellent effect in terms of cost is brought about.

The linear low-density polyethylene polymerized by using a metallocene catalyst used in the conductive resin composition of the present invention has a melt flow rate measured value of 1 to 100 g / 10 mi at 230 ° C. and a load of 2160 g.
n. Within the range, the flowability of the conductive resin composition and the resin at the time of producing a molded article thereof is optimized, and good moldability is obtained.

The linear low-density polyethylene polymerized using a metallocene catalyst used in the conductive resin composition of the present invention has a density of 840 to 920 kg /
Since m ³ and the flexural modulus are in the range of 100 to 500 MPa, the conductive resin composition and its molded article have excellent impact strength.

As described above, by using metallocene LLDPE as an impact modifier in the conductive resin composition and using a homopolymer of polypropylene as the base resin or a random copolymer with ethylene, the impact resistance of the molded article is improved. It is possible to improve the fluidity of the resin and the surface appearance of the molded product while maintaining the same.

Claims (5)

[Claims] 1. A linear low-density polyethylene 5 polymerized by using a polypropylene resin obtained by homopolymerization of propylene or random copolymerization of propylene and ethylene in an amount of 10 to 80% by weight, and a metallocene catalyst as a modifier component.
To 50% by weight of carbon black, graphite, metal powder and its whiskers, 5 to 70% by weight of at least one kind of conductive material selected from metal fibers, metal oxides and carbon fibers. Composition. 2. The conductive resin composition according to claim 1, wherein the conductive material is carbon black. 3. A linear low-density polyethylene polymerized by using a metallocene catalyst is melt flow rate measured at 230 ° C. under a load of 2160 g, which is 1 to 100 g / 10 mi.
n. The conductive resin composition according to claim 1 or 2, wherein the conductive resin composition is in the range. 4. A linear low density polyethylene polymerized using a metallocene catalyst has a density of 840 to 920 kg / m ³ ,
The conductive resin composition according to any one of claims 1 to 3, which has a flexural modulus of 100 to 500 MPa. 5. A molded article obtained by using the conductive resin composition according to claim 1.