Electro-conductive thermoplastic resin foam and preparation proc

Details Electro-conductive thermoplastic resin foam and preparation proc Electro-conductive thermoplastic resin foam and preparation proc

1983-11-28

1985-06-25

Barr, Josephine L.

Compositions

Electrically conductive or emissive compositions

Elemental carbon containing

521 79, 521 82, 521138, 521140, 521149, 20415911, 20415914, 2041592, H01B 106

Patent

active

045252971

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE ART

The present invention relates to a polyolefin electro-conductive thermoplastic foam and a process for preparation thereof.


BACKGROUND OF THE ART

An electro-conductive thermoplastic foam is a promising material which can find wide applications in packing, transporting, and storing precision gauges such as electronic elements, or in making antistatic carpet underlays. Especially, concurrently with the striking development in electronic industries in recent years, there is increasing need for a shock absorbent material with excellent electro-conductivity for housing integrated circuits which require measures for preventing static electricity buildup. Film and resin-like materials which are conventional electro-conductive materials lack shock absorption capabilities, and sometimes have allowed integrated circuits (I.C.) or parts containing I.C. to break during transportion. In carbon black-impregnated polyurethane foam which has long been marketed as a foam, there are also faults such as carbon black being separated from the foam, which impairs the electro-conductivity, contaminates the product, and aggravates the working conditions; moreover, shaped foam products are not available because it is difficult to form the foam sheets into the molded product which are needed. Therefore, it is desirable to develop a further-improved electro-conductive thermoplastic foam.
Attempts have been made to produce electro-conductive thermoplastic foams using thermoplastic polyolefin resin, such as polyethylene, etc., but good marketable foams have not been developed because such foams as have been produced have faults such as production difficulties, quality variation, inferiority in foam mechanical properties, or difficulty to form needed foam sheets.
An object of the present invention is to provide an polyolefin-type electro-conductive thermoplastic foam which has, excellent intrinsic properties such as shock absorption, thermoformability, electro-conductivity, and quality stability, and which is easy to manufacture, and a process for preparing it.
Another object of the present invention is to provide an electro-conductive thermoplastic foam having a smooth surface without surface roughness, and a process for producing it.
A further object of the present invention is to provide a material for containers which makes it possible to prevent semiconductor integrated circuits, etc., from being damaged by static electricity, and to ensure their safe transportation, and a process for its preparation.


DISCLOSURE OF THE INVENTION

The present invention relates to a cross-linked electro-conductive thermoplastic foam which consists of 10 to 90 parts by weight of crystalline thermoplastic polyolefin resin, 10 to 90 parts by weight of low crystalline thermoplastic resin, and 5 to 40 parts by weight of electro-conductive carbon black per 100 parts by weight of a total of the aforesaid resin components, and a process for producing an electro-conductive thermoplastic foam, which comprises crosslinking and foaming a mixture consisting of 10 to 90 parts by weight of crystalline thermoplastic polyolefin resin, 10 to 90 parts by weight of low crystalline thermoplastic resin, and 5 to 40 parts by weight of carbon black per 100 parts by weight of a total of the aforesaid resin components.


MOST PREFERRED FORM FOR EMBODIMENT OF THE INVENTION

The crystalline thermoplastic polyolefin resin in the present invention is a crystalline olefin polymer of .alpha.-olefin having 2 to 8 carbon atoms as the necessary monomer. Specific examples of said crystalline polyolefin are polyethylene, polypropylene, polybutene, polymethylbutene, polymethyl-pentene, and copolymers of two members thereof, and pre-ferably polyethylene, polypropylene, and propylene ethylene random copolymer containing 2 to 5 wt % of ethylene. The melt index (MI) of the thermoplastic poly-olefin resin is preferably from 1 to 100 g/10 min, more preferably from 10 to 80 g/10 min, and most preferably from 30 to 70 g/10 min. The intrinsic viscosity (.eta.) of the thermo

REFERENCES:
patent: 4431575 (1984-02-01), Fujie et al.
Polymer Chemistry--pp. 3, 5.
Polymer and General Chemistry--p. 4.

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