High-performance filter with high thermal and chemical stability - has adsorber particles bonded to a three-dimensional porous support coated with a thermally stable, hydrolysis-resistant plastic

摘要

A high-performance filter is claimed, consisting of a 3-dimensional supporting structure (A) to which adsorber particles (B) are attached by means of a bonding agent (C). (A) is coated with a thermally-stable plastic (I) which is very resistant to hydrolysis, in amts. of 20-500% w.r.t. (A). Pref. (A) is reticulated PUR foam with large pores, coated with a silicone resin, esp. silicone rubber, or sintered polypropylene (PP), hydrolysis resistant PUR, crosslinked acrylic resin, synthetic rubber or fluorinated or partly fluorinated plastic, or a combination of such materials with complementary properties. (C) is an adhesive with good chemical and thermal stability which is also resistant to hydrolysis, esp. PUR, acrylate copolymer, acrylate, or a latex based on neoprene, chloroprene, butyl rubber, synthetic rubber or silicone. USE/ADVANTAGE - The invention provides a high-performance filter which combines the advantages of a polyurethane (PUR) foam support (good porosity (i.e. high air permeability), and flexibility) with high thermal stability and resistance to hydrolysis (contrast uncoated PUR which is unable to withstand desorption by heating to above 150 deg.C or by treatment with superheated steam). In an example, reticulated PUR-polyurea foam with 15 pores/inch and bulk density 30g/l was impregnated and squeezed out with a mixt. of 1000 pts. wt. Impranil HS 62 (RTM) and 62 pts. wt. Imprafix HSC (RTM) (squeezing effect 120%), and dried at 160 deg.C to give a crosslinked, very hydrolysis-resistant coating which improved the response of the foam to external conditions. The same material was used as bonding agent for the adsorber (active carbon). The finished filter mat had density, 295g/l, comprising 30 g/l original foam, 65g/l PUR coating and adhesive, and 200g/l adsorber. The service life of the mat was increased by 40-60% for desorption by superheated steam; for nitrogen desorption the temp. could be increased to 160-165 deg.C.