Process for preparing polyurethanes
AssigneeBASF SE
InventorsHans-Juergen Reese, Imbridt Murrar, Ralf Fritz, Andres Cabrera, Birgit Magg
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Abstract
The invention relates to a process for the preparation of polyurethanes by reacting polyisocyanates a) with compounds having at least two hydrogen atoms reactive with isocyanate groups b), wherein a polyisocyanate a) used is at least one polyisocyanate ai) having an average functionality of greater than 2, a content of diisocyanates of not more than 2% by weight and a content of uretonimines of not more than 4% by weight, based in each case on the weight of the polyisocyanate ai).
Claims26
A process for the preparation of a polyurethane, the process comprising:
- (A) removing uretonimines from a mixture comprising diphenylmethane diisocyanate and polyphenylenepolymethylene polyisocyanates ai) until a content of the uretonimines is not more than 4% by weight, thereby obtaining a polyisocyanate a);
- and
- (C) reacting the polyisocyanate a) with one or more compounds having at least two hydrogen atoms reactive with an isocyanate group b),
- wherein the polyisocyanate a) is at least one mixture of diphenylmethane diisocyanate and polyphenylenepolymethylene polyisocyanates ai)
- having an average functionality of from 2.2 to 5.2,
- a content of dinuclear MDI of not more than 2% by weight,
- a content of trinuclear MDI of from 25 to 65% by weight,
- a content of tetranuclear MDI of from 5 to 45% by weight,
- a content of ≧pentanuclear MDI of from 1 to 17.5% by weight, and
- a content of uretonimines of not more than 4% by weight, based in each case on a weight of the polyisocyanate ai), and
- wherein the polyisocyanate a) has a viscosity of 1258 to 7000 mPa·s at 25° C.
A polyisocyanate mixture, consisting of:
- diphenylmethane diisocyanate;
- and
- polyphenylenepolymethylene polyisocyanates,
- wherein the mixture has
- (i) a content of dinuclear MDI of not more than 2% by weight,
- (ii) a content of trinuclear MDI of from 25 to 65% by weight,
- (iii) a content of tetranuclear MDI of from 5 to 45% by weight,
- (iv) a content of ≧pentanuclear MDI of from 1 to 17.5% by weight, and
- (v) a content of uretonimines of not more than 4% by weight, based in each case on a weight of the polyisocyanate mixture,
- (vi) a viscosity of 1258 to 7000 mPa·s at 25° C., and
- (vii) an average functionality of from 2.2 to 5.2.
A polyisocyanate mixture, comprising:
- (1) at least one polyisocyanate ai) having
- (1a) an average functionality of from 2.2 to 5.2 and a viscosity 1258 to 7000 mPa·s at 25° C.,
- (1b) a content of dinuclear MDI of not more than 2% by weight,
- (1c) a content of trinuclear MDI of from 25 to 65% by weight,
- (1d) a content of tetranuclear MDI of from 5 to 45% by weight,
- (1e) a content of pentanuclear MDI of from 1 to 17.5% by weight, and
- (1f) a content of uretonimines of not more than 4% by weight, based in each case on the weight of the polyisocyanate ai), and
- (2) a prepolymer aii) comprising (2a) isocyanate groups and (2b) urethane groups and (2c) having a content of unconverted monomeric isocyanates of not more than 1% by weight, based on the weight of the prepolymer aii).
Dependencies are inferred from the claim text.