Latent two-part polyurethane adhesives

Patent metadata

Field	Value
Publication number	US-10400144-B2
Application number	US-201615579744-A
Country	US
Kind code	B2
Filing date	Jun 14, 2016
Priority date	Jun 18, 2015
Publication date	Sep 3, 2019
Grant date	Sep 3, 2019

Abstract

Two-component polyurethane adhesives include a polyol component and a polyisocyanate component. The polyol component includes a polyether polyol and specific amount of an aliphatic diol chain extender. The polyisocyanate component includes an isocyanate prepolymer made by reacting an aromatic polyisocyanate with a polyether. The adhesive has an excellent combination of a prolonged open time followed by curing to form a strong adhesive bond. The adhesive is especially useful for bonding carbon fiber-reinforced plastics.

First claim

What is claimed is:

1. A two-component polyurethane adhesive composition having a polyol component and an isocyanate component, wherein:
the polyol component includes:
a) at least 35 weight percent, based on the weight of the polyol component, of one or more polyether polyols having a hydroxyl equivalent weight of 400 to 2000 and a nominal hydroxyl functionality of 2 to 4, which polyether polyols(s) are selected from homopolymers of propylene oxide and copolymers of 70 to 99% by weight propylene oxide and 1 to 30% by weight ethylene oxide;
b) 4 to 8 equivalents per equivalent of a), of one or more aliphatic diol chain extenders;
c) 0.1 to 3 parts by weight per 100 parts by weight of a), of at least one compound having at least two primary and/or secondary aliphatic amine groups;
d) i) a catalytically effective amount of at least one ambient temperature urethane catalyst which is active at a temperature of below 30° C., and
ii)a catalytically effective amount of at least one latent urethane catalyst which is active at a temperature of at least 40° C.;

e) up to 60 weight percent, based on the weight of the polyol component, of at least one particulate filler;
and the polyisocyanate component includes:
25 to 60 weight percent, based on the weight of the polyisocyanate component, of at least one isocyanate-terminated prepolymer having at least 2 isocyanate groups per molecule and an isocyanate equivalent weight of 500 to 3500, the prepolymer being a reaction product of one or more aromatic diisocyanates having a molecular weight of up to 350 with i) at least one 700 to 3000 molecular weight homopolymer of poly(propylene oxide) having a nominal hydroxyl functionality of 2 to 4 or ii) a mixture of i) with up to 3 parts by weight, per part by weight of i), of a 2000 to 8000 molecular weight polyether polyol which is a copolymer of 70 to 99 weight percent propylene oxide and 1 to 30 weight percent ethylene oxide and has a nominal hydroxyl functionality of 2 to 4;
20 to 50 weight percent, based on the weight of the polyisocyanate component, of at least one polyisocyanate compound having an isocyanate equivalent weight of up to 300 and 2 to 4 isocyanate groups per molecule; and
up to 50% by weight of at least one particulate filler;
wherein the isocyanate equivalent weight of the polyisocyanate component and the equivalent weight per isocyanate-reactive group of the polyol component are such that when the polyisocyanate component and the polyol component are mixed at a 1:1 ratio by volume the isocyanate index is 1.1 to 1.8.

2. A composition according to claim 1 wherein the one or more latent room temperature organometallic catalysts contain tin, zinc or bismuth.

3. A composition according to claim 1 wherein the one or more latent room temperature organometallic catalysts are zinc alkanoates, bismuth alkanoates, dialkyltin alkanoates, dialkyl tin mercaptides, dialkyl tin bis(alkylmercaptoacetates), dialkyltin thioglycolates or mixtures thereof.

4. A composition according to claim 1 wherein the one or more latent room temperature organometallic catalysts are dialkyl tin mercaptides, dialkyl tin bis(alkylmercaptoacetates), dialkyltin thioglycolates or mixtures thereof.

5. A composition of claim 1 wherein the latent catalyst is one or both of a dialkyltinthioglycolate and an acid-blocked amidine catalyst.

6. A composition according to claim 5 wherein the acid-blocked amidine catalyst comprises 1,8-Diazabicyclo[5.4.0]undec-7-ene) or 1,5-Diazabicyclo[4.3.0]non-5-ene.

7. A composition of claim 1 , wherein the polyol component includes 4 to 7 equivalents of one or more aliphatic diol chain extenders per equivalent of a).

8. A composition of claim 1 , wherein the polyol component includes monoethylene glycol.

9. A composition of claim 8 , wherein the polyol component includes 4 to 6 equivalents of monoethylene glycol per equivalent of a).

10. A composition of claim 1 , wherein the isocyanate-terminated prepolymer is a reaction product of one or more aromatic diisocyanates having a molecular weight of up to 350 with i) at least one 700 to 3000 molecular weight homopolymer of poly(propylene oxide) having a nominal hydroxyl functionality of 2 to 4.

11. A composition of claim 1 , wherein the polyol component and the polyisocyanate component each are devoid of a plasticizer.

12. A composition of claim 1 , wherein the polyol component and the polyisocyanate component each are devoid of carbon particles.

13. A composition of claim 1 , wherein polyisocyanate compound having an isocyanate equivalent weight of up to 300 and 2 to 4 isocyanate groups per molecule is a mixture of at least one aliphatic polyisocyanate compound and at least one aromatic polyisocyanate compound.

14. A cured adhesive formed by curing the two-component polyurethane adhesive composition of claim 1 .

15. A method of bonding two substrates, comprising forming a layer of the two-component polyurethane adhesive of claim 1 at a bondline between two substrates, and curing the layer at the bondline to form a cured adhesive bonded to each of the substrates.

16. A composition according to claim 1 wherein d) i) the ambient cure catalyst is selected from stannic chloride, stannous chloride, stannous octoate, stannous oleate, dimethyltin dilaurate, dibutyltin dilaurate, tin ricinoleate and other tin compounds of the formula SnRn(OR)4-n, wherein R is alkyl or aryl and n is 0 to 18, dialkyl tin mercaptides; tertiary amines, amidines, bismuth salts, cobalt salts, zinc salts or mixtures thereof and the d) ii) latent urethane catalyst is selected from zinc alkanoates, bismuth alkanoates, dialkyltin alkanoates, dialkyl tin mercaptides, dialkyl tin bis(alkylmercaptoacetates), dialkyltin thioglycolates, acid-blocked tertiary amine and/or cyclic amidine catalysts or mixtures thereof.

17. A composition according to claim 1 wherein the d) ii) latent urethane catalyst is selected from dialkyl tin thioglycolates; and acid-blocked tertiary amine and/or cyclic amidine catalysts.

18. A composition according to claim 1 wherein the d) ii) latent urethane catalyst is selected from dioctyltinthioglcolate, dibutyltinthioglycolate and dimethyltinthioglycolate, acid-blocked tertiary amine and/or cyclic amidine catalysts, in which the acid blocking group is a C 1 -C18 alkanoic acid, a benzoate or substituted benzoate, or mixtures thereof.

19. A composition according to claim 1 wherein the polyol includes monoethylene glycol, or a mixture of monoethylene glycol with one or both of 1,2-propane diol and 1,4-butanediol, in an amount sufficient to provide at least 4 equivalents of monoethylene glycol per equivalent of polyol a.

Assignees

• Dow Global Technologies Llc

Inventors

• Schmatloch Stefan
• Caderas Ilona

Classifications

• C08G18/5024

  containing primary and/or secondary amino groups · CPC title

• C09J175/04 Primary

  Polyurethanes · CPC title

• C08G18/724

  Combination of aromatic polyisocyanates with (cyclo)aliphatic polyisocyanates · CPC title

• C08J3/24

  Crosslinking, e.g. vulcanising, of macromolecules (mechanical aspects B29C35/00; crosslinking agents C08K) · CPC title

• C08K9/00

  Use of pretreated ingredients · CPC title