Heat-resistant filter element and method for production thereof
A subject for the invention is to provide a low-cost heat-resistant filter element produced from polyethylene particles which is for use in separating and collecting particles from a dust gas, can be continuously used even in a high-temperature environment of about from 70° C. to 130° C., especially from 90° C. to 110° C., is excellent in chemical resistance, and has flexibility and excellent suitability for mass production. Another subject is to provide processes by which the heat-resistant filter element can be produced at a reduced equipment cost while taking care of the environment. In the invention, a coating layer of a fluororesin was formed on a surface of a permeable porous molding obtained from particles of a resin composition containing a polyethylene as a main component of a resin ingredient and from 0.1 to 3 parts by weight of an antioxidant per 100 parts by weight of the resin ingredient by fusion-bonding the particles to one another at the surface thereof.
1. A heat-resistant filter element for separating and collecting particles from a dust gas, comprising:
a permeable porous molding comprising particles of a resin composition in which the particles are fused to one another on the surface thereof, said fused portion including an antioxidant, wherein the resin particles have a fused surface portion and an unfused inner portion, said antioxidant being present in higher concentration in said fused portion than in said unfused portion, wherein the resin composition comprises a polyethylene as a main component of its resin ingredient and from 0.5 to 3 parts by weight of the antioxidant per 100 parts by weight of the resin ingredient; and
a coating layer of a fluororesin formed on the surface of the permeable porous molding, said heat-resistant filter element prepared by:
(I-1) dispersing a powdered antioxidant in resin particles comprising a polyethylene as a main component,
(I-2) infiltrating the antioxidant into the resin particles comprising a polyethylene as a main component by heating to a temperature which is not lower than the melting point where the antioxidant liquefies and is in the range where the resin particles substantially retain their shape to prepare a particulate resin composition,
(I-3) packing the particulate resin composition into a mold followed by heating to fusion-bond the resin composition particles to one another at the surface thereof to thereby form a permeable porous molding, and
(I-4) forming a coating layer of a fluororesin on the surface of the permeable porous molding formed.
2. A heat-resistant filter element for separating and collecting particles from a dust gas, comprising:
a permeable porous molding comprising particles of a resin composition in which the particles are fused to one another on the surface thereof, said fused portion including an antioxidant, wherein the resin particles have a fused surface portion and an unfused inner portion, said antioxidant being present in higher concentration in said fused portion than in said unfused portion, wherein the resin composition comprises a polyethylene as a main component of its resin ingredient and from 0.5 to 3 parts by weight of the antioxidant per 100 parts by weight of the resin ingredient; and
a coating layer of a fluororesin formed on the surface of the permeable porous molding, said heat-resistant filter element prepared by:
(II-1) dispersing a powdered antioxidant in resin particles comprising a polyethylene as a main component,
(II-2) packing the resin particles comprising the powdered antioxidant dispersed therein into a mold followed by heating to fusion-bond the resin composition particles to one another at the surface thereof to thereby form a permeable porous molding while infiltrating the antioxidant into the resin particles, and
(II-3) forming a coating layer of a fluororesin on the surface of the permeable porous molding formed.