Mixed blocked isocyanate prepolymers, a process for their production and their use for the production of flexible epoxy resin systems
AssigneeBayer Aktiengesellschaft
InventorsLutz Schmalstieg, Rainer Rettig, Eberhard Konig
Life of this patent
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Abstract
Isocyanate prepolymers based on an aromatic diisocyanate and a polyether polyol in which at least 95% of the isocyanate groups are blocked by blocking agents selected from A) about 50 to about 97 equivalent % of a phenol or substituted phenol, B) about 30 to about 50 equivalent % of a pyrazole or a substituted pyrazole and C) 0 to about 10 equivalent % of a blocking agent different from A) and B). These blocked isocyanate prepolymers are particularly useful for the production of flexible epoxy resin systems.
Claims6
An isocyanate prepolymer which is the reaction product of
- (1) an aromatic diisocyanate and
- (2) a polyether polyol having an average hydroxyl functionality of from about 1.5 to about 4, in which at least 95 equivalent % of the isocyanate groups are blocked with a blocking agent composition made up of
- (A) from about 50 to about 97 equivalent % of a phenol or substituted phenol,
- (B) from about 3 to about 50 equivalent % of a pyrazole or a substituted pyrazole, and
- (C) from 0 to about 10 equivalent % of a blocking agent which is different from (1) and (2) with the sum of (A) plus (B) plus (C) totalling 100
- and from about 1.3 to about 7% of the total weight of the prepolymer is the sum of the weight of free isocyanate groups plus the weight of the blocked isocyanate groups.
A process for the production of a blocked isocyanate prepolymer comprising
- 1) reacting
- a) an aromatic diisocyanate with
- b) a polyether polyol having an average hydroxyl functionality of from about 1.5 to about 4 to form a prepolymer which has an isocyanate group
- content of from 1.4 to 8.5% by weight,
- and
- 2) blocking at least 95 equivalent % of the isocyanate groups present in the prepolymer produced in step 1)with a blocking agent composition made up of
- (A) from about 50 to about 97 equivalent % of a phenol or a substituted phenol,
- (B) from about 3 to about 50 equivalent % of a pyrazole or a substituted pyrazole, and
- (C) from 0 to about 10 equivalent % a of blocking agent which is different from (A) and (B),
- with the total equivalent % of (A) plus (B) plus (C) being equal to 100.
Dependencies are inferred from the claim text.