Process for producing prepolymers which cure to improved sealants, and products formed thereby

• US 5,990,257 A
• Filed: 01/22/1998
• Issued: 11/23/1999
• Est. Priority Date: 01/22/1998
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: Witco Corporation (Lanxess AG)
• Inventors: Lehmann, Patrice, Johnston, Robert R.
• Primary Examiner(s): SERGENT, RABON A
• Application Number:
  US09/009,868
• Time in Patent Office: 670 Days
• Field of Search: 528/28, 528/29, 528/59, 528/69, 556/414, 556/420
• US Class Current: 528/28
• CPC Class Codes: C08G 18/10 Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
• CPC Class Codes: C08G 18/289 containing silicon
• CPC Class Codes: C08G 18/4866 having a low unsaturation value
• CPC Class Codes: C08G 18/718 containing silicon
• CPC Class Codes: C08G 18/7671 containing only one alkylene bisphenyl group
• CPC Class Codes: C08G 2190/00 Compositions for sealing or packing joints

Abstract

Silylated polyurethanes exhibiting a superior combination of mechanical properties and which cure in reasonable time to a low-tack sealant, without excessive viscosity, are prepared by reacting a polyol component having terminal unsaturation of less than 0.2 meq/g with a diisocyanate component to form a hydroxyl-terminated prepolymer, and endcapping the prepolymer with an isocyanate silane of the formula OCN--R--Si--(X)_m (--OR¹)_3-m wherein m is 0, 1 or 2, each R¹ is alkyl containing 1 to 4 carbon atoms, each X is alkyl containing 1 to 4 carbon atoms, and R is a difunctional organic group.

Claims

1. A process for preparing a silylated polyurethane, comprising

(A) reacting (i) a polyol component having terminal unsaturation less than 0.02 milliequivalents per gram of polyol with a molecular weight of 2,000-20,000 daltons, with (ii) a diisocyanate component at a stoichiometric excess of said polyol component to said diisocyanate component, whereby a polyurethane prepolymer is formed which is hydroxyl-terminated;

and

(B) reacting said polyurethane prepolymer with one or more isocyanate silanes of the formula (1)

space="preserve" listing-type="equation">OCN--R--Si--(X).sub.m (--OR.sup.1).sub.3-m (

     1)

wherein m is 0, 1 or 2, each R¹ is alkyl containing 1 to 4 carbon atoms, each X is alkyl containing 1 to 4 carbon atoms, and R is a difunctional organic group, to endcap the hydroxyl groups on said prepolymer with said isocyanate silane.

2. A process according to claim 1 wherein R is difunctional straight or branched alkyl containing 2 to 6 carbon atoms.

3. A process according to claim 1 wherein each R¹ is methyl or ethyl.

4. A process according to claim 1 wherein each X is methyl or ethyl.

5. A process according to claim 1 wherein m is zero.

6. A process according to claim 1 wherein m is one.

7. A process according to claim 1 wherein said isocyanate silane of formula (1) is gamma-isocyanatopropyl-trimethoxysilane.

8. A process according to claim 1 wherein said isocyanate silane of formula (1) is gamma-isocyanatopropyl-triethoxysilane.

9. A process according to claim 1 wherein said diisocyanate component is selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'"'"'-diphenyl-methanediisocyanate, 2,4'"'"'-diphenyl-methanediisocyanate, isophorone diisocyanate, 4,4'"'"'-dicyclohexylmethane-diisocyanate-isomers, and mixtures thereof.

10. A silylated polyurethane prepared by a process comprising

(A) reacting (i) a polyol component having terminal unsaturation less than 0.02 milliequivalents per gram of polyol with a molecular weight of 2.000-20.000 daltons, with (ii) a diisocyanate component at a stoichiometric excess of said polyol component to said diisocyanate component, whereby a polyurethane prepolymer is formed which is hydroxyl-terminated;

and

(B) reacting said polyurethane prepolymer with one or more isocyanate silanes of the formula (1)

space="preserve" listing-type="equation">OCN--R--Si--(X).sub.m (--OR.sup.1).sub.3-m (

     1)

wherein m is 0, 1 or 2, each R¹ is alkyl containing 1 to 4 carbon atoms, each X is alkyl containing 1 to 4 carbon atoms, and R is a difunctional organic group, to endcap the hydroxyl groups on said prepolymer with said isocyanate silane.

11. A silylated polyurethane according to claim 10 wherein R is difunctional straight or branched alkyl containing 2 to 6 carbon atoms.

12. A silylated polyurethane according to claim 10 wherein each R¹ is methyl or ethyl.

13. A silylated polyurethane according to claim 10 wherein each X is methyl or ethyl.

14. A silylated polyurethane according to claim 10 wherein m is zero.

15. A silylated polyurethane according to claim 10 wherein m is one.

16. A silylated polyurethane according to claim 10 wherein said isocyanate silane of formula (1) is gamma-isocyanatopropyl-trimethoxysilane.

17. A silylated polyurethane according to claim 10 wherein said isocyanate silane of formula (1) is gamma-isocyanatopropyl-triethoxysilane.

18. A silylated polyurethane according to claim 10 wherein said diisocyanate component is selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'"'"'-diphenyl-methanediisocyanate, 2,4'"'"'-diphenyl-methanediisocyanate, isophorone diisocyanate, 4,4'"'"'-dicyclohexylmethane-diisocyanate-isomers, and mixtures thereof.