Moisture-curable, hot-melt composition

• US 5,827,926 A
• Filed: 11/08/1996
• Issued: 10/27/1998
• Est. Priority Date: 11/08/1996
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Shimizu, Yoshinori
• Primary Examiner(s): Short, Patricia A.
• Application Number:
  US08/745,364
• Time in Patent Office: 718 Days
• Field of Search: 525/127, 525/131
• US Class Current: 525/127
• 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 18/307 Atmospheric humidity
• CPC Class Codes: C08G 2170/20 Compositions for hot melt adhesives
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• CPC Class Codes: C09J 175/04 Polyurethanes

Abstract

There are provided moisture-curable hot-melt compositions comprising a polyurethane prepolymer and a crystalline polymer obtained from monomer(s) containing at least one crystalline ethylenically unsaturated monomer with no active hydrogen, which have low melt viscosities and high initial impact strength and final strength. The monomers may also contain amorphous ethylenically unsaturated monomers with no active hydrogen, in addition to the crystalline monomer. Typical crystalline monomers are (meth)acrylate esters of non-tertiary alcohols, the alkyl portions of which comprise 16 or more carbon atoms. Typical amorphous monomers are (meth)acrylate esters of non-tertiary alcohols, the alkyl portions of which comprise no more than 15 carbon atoms. Use of an alkyl acrylamide as one of the amorphous monomers is advantageous for improving the performance of the moisture-curable hot-melt adhesive.

Claims

1. A moisture-curable hot-melt composition comprising a polyurethane prepolymer and a crystalline polymer obtained from monomer(s) containing at least one crystalline (meth)acrylate monomer with no active hydrogen.

2. The composition according to claim 1, wherein said crystalline polymer is a polymer obtained from the crystalline (meth)acrylate monomer with no active hydrogen and amorphous ethylenically unsaturated monomer(s) with no active hydrogen.

3. The composition according to claim 2, wherein said crystalline polymer has a melting point of 15°

-135°

C.

4. The composition according to claim 3, wherein said crystalline (meth)acrylate monomer is a (meth)acrylate ester of a non-tertiary alcohol, the alkyl portion of which comprises 16 or more carbon atoms.

5. The composition according to claim 2, wherein said amorphous ethylenically unsaturated monomer(s) is selected from the group consisting of (meth)acrylate esters of non-tertiary alcohols, the alkyl portions of which comprise no more than 15 carbon atoms, (meth)acrylate esters of alcohols other than alkyl alcohols, vinyl esters, vinyl ethers, alkyl acrylamides, styrene, acrylonitrile, N-vinyllactams, vinylidene chloride and vinyltoluene.

6. The composition according to claim 2, wherein said crystalline polymer contains an alkyl acrylamide.

7. The composition according to claim 1, wherein said crystalline polymer has a melting point of 15°

-135°

C.

8. The composition according to claim 7, wherein said crystalline (meth)acrylate monomer is a (meth)acrylate ester of a non-tertiary alcohol, the alkyl portion of which comprises 16 or more carbon atoms.

9. The composition according to claim 1, wherein said monomers include 5-100 wt % of a crystalline monomer.

10. The composition according to claim 1, wherein said monomers include 10-90 wt % of a crystalline monomer.

11. The composition according to claim 1, wherein said monomers include 30-80 wt % of a crystalline monomer.

12. The composition according to claim 1, wherein the weight average molecular weight of said crystalline polymer is between 5,000 and 100,000.

13. The composition according to claim 1, wherein the weight average molecular weight of said crystalline polymer is greater than 30,000 and up to 100,000.

14. The composition according to claim 1, wherein the weight average molecular weight of said crystalline polymer is greater than 30,000 and up to 60,000.

15. The composition according to claim 1 which contains said crystalline polymer at an amount of 5-90 wt %.

16. The composition according to claim 1 which contains said crystalline polymer at an amount of 5-80 wt %.

17. The composition according to claim 1 which contains said crystalline polymer at an amount of 5-70 wt %.

18. The composition according to claim 1 which has a melt viscosity at 121°

C. (250°

F.) of 50,000 centipoise or lower.

19. The composition according to claim 1 which has an initial impact strength of 5 kg·

cm or greater.

20. The composition according to claim 1 which has a final strength of 15 kg/cm² or greater.

21. The composition of claim 1, wherein said crystalline (meth)acrylate monomer is behenyl methacrylate.

22. A method of preparing the moisture-curable hot melt composition of claim 1, comprising the steps of:

providing a polyol;

incorporating a crystalline (meth)acrylate polymer into the polyol;

adding an isocyanate component to the polyol, such that the polyol and the isocyanate component are capable of forming the polyurethane prepolymer having the crystalline (meth)acrylate polymer therein; and

reacting the polyol and the isocyanate component such that they form the polyurethane prepolymer.

23. The method of claim 22, further comprising the step of hot-melt coating the moisture-curable, hot-melt composition.