Claims
- 1. In a process for producing rigid foamed materials containing polyurethane groups and optionally isocyanurate groups by the reaction of
- a) one or more polyisocyanates with
- b) one or more compounds having molecular weights of from 400 to 10,000 and containing at least two hydrogen atoms reactive to isocyanates,
- in the presence of
- c) water and/or readily volatile organic substances as the foaming agent, optionally in the presence of
- d) one or more compounds of molecular weight 32 to 399 containing at least two hydrogen atoms reactive to isocyanates,
- the improvement wherein polyisocyanate a) is an aromatic polyisocyanate comprising a bottoms product containing isocyanate groups with a tolylene diisocyanate content less than 200 ppm, and is obtained by
- A) mixing distillation bottoms from tolylene diisocyanate production with polyisocyanates or polyisocyanate mixtures of the diphenyl methane series with an NCO content of at least 15 weight %, optionally modified with urethane and/or allophanate,
- B) working up the mixture by distillation, the mixture being heated before or during distillation work-up to temperatures of 190.degree. to 250.degree. C. and by this means substantially replacing the tolylene diisocyanate which is reversibly chemically bound in the distillation residue by the polyisocyanate mixed therewith, and
- C) reacting the distillation bottoms obtained in step B) with 0.1-10 weight % of a polyether alcohol of molecular weight from 206 to 948, said polyether alcohol being obtained by the reaction of alkylene oxides with C.sub.6 -C.sub.30 hydrocarbons containing 1-3 active hydrogen atoms.
- 2. The process of claim 1, wherein said polyether alcohol is used in an amount of from 2 to 7 weight % and wherein said hydrocarbon is a C.sub.8 -C.sub.20 hydrocarbon.
- 3. The process of claim 1, wherein the isocyanate mixed in step A) is selected from the group consisting of 4,4'-diisocyanatodiphenyl methane, its technical mixtures with 2,4'- and optionally 2,2'-diisocyanatodiphenyl methane and mixtures of these diisocyanatodiphenyl methane isomers with up to 65 weight % (based on the mixture) of their higher homologues containing more than 2 isocyanate groups per molecule.
- 4. The process of claim 1, wherein in step A), said tolylene diisocyanate bottoms contain NCO groups and are mixed with from 20-80 weight % of polyisocyanates of the diphenyl methane series.
- 5. The process of claim 1, wherein mixtures of diisocyanato-diphenyl methane isomers with up to 65 weight % (based on the mixture) of their higher homologues containing more than 2 isocyanate groups per molecule are admixed as polyisocyanates of the diphenyl methane series in step A).
Priority Claims (1)
Number |
Date |
Country |
Kind |
42 11 774.7 |
Apr 1992 |
DEX |
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Parent Case Info
This application is a division of application Ser. No. 08/040,699, filed Mar. 31, 1993, issued as U.S. Pat. No. 5,424,386.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4304708 |
Marx et al. |
Dec 1981 |
|
5028636 |
Gebauer et al. |
Jul 1991 |
|
5314588 |
Zarnack et al. |
May 1994 |
|
Foreign Referenced Citations (2)
Number |
Date |
Country |
257827 |
Jun 1988 |
DEX |
1434917 |
May 1976 |
GBX |
Divisions (1)
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Number |
Date |
Country |
Parent |
40699 |
Mar 1993 |
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