UV-curing hot melt adhesive containing low content of oligomers

Patent metadata

Field	Value
Publication number	US-9676977-B2
Application number	US-201514605087-A
Country	US
Kind code	B2
Filing date	Jan 26, 2015
Priority date	Jul 26, 2012
Publication date	Jun 13, 2017
Grant date	Jun 13, 2017

Abstract

A reactive hot melt adhesive comprising a blend of a (meth)acrylate polymer, a polyurethane polymer containing (meth)acrylate groups and a polyurethane prepolymer containing NCO-groups wherein the content of low molecular weight (meth)acrylate urethanes is less than 1 wt % of the adhesive. The adhesive provides a fast and improved green strength during application.

First claim

What is claimed is:

1. A reactive hot melt adhesive comprising a blend of a (meth)acrylate polymer, a polyurethane polymer containing (meth)acrylate groups and a polyurethane prepolymer containing NCO-groups wherein the content of low molecular weight (meth)acrylate urethanes is less than 1 wt % of the adhesive.

2. A hot melt adhesive according to claim 1 , wherein the (meth)acrylate polymer has a molecular weight (M N ) of more than 5000 g/mol.

3. A hot melt adhesive according to claim 1 , wherein the adhesive comprises 5 to 45 wt % of the (meth)acrylate polymer, the (meth)acrylate polymer has a molecular weight (M N ) of more than 5000 g/mol and the (meth)acrylate polymer is non reactive.

4. A hot melt adhesive according to claim 1 , wherein the polyurethane polymer containing (meth)acrylate groups comprises about 70 to 100 mol % of (meth)acrylate groups and 0 to 30 mol-% of remaining NCO-groups.

5. A hot melt adhesive according to claim 4 , wherein the polyurethane polymer containing (meth)acrylate groups is prepared by reaction of a NCO-containing PU-prepolymer comprising less than 1 wt-% of monomeric diisocyanates with OH-alkyl-substituted (meth)acrylate esters in a ratio OH:NCO from 0.7:1 to 1.01:1.

6. A hot melt adhesive according to claim 4 , wherein the adhesive comprises 5 to 50 wt % of the polyurethane polymer containing (meth)acrylate groups.

7. A hot melt adhesive according to claim 1 , wherein the amount of the polyurethane prepolymer is from 10 to 50 wt-% of the adhesive composition.

8. A hot melt adhesive according to claim 1 , optionally further comprising additives, fillers, stabilizers, tackifiers, plasticizers, adhesion promotors or additional non-reactive polymers.

9. A hot melt adhesive according to claim 1 , having a viscosity of from 2000 to 20000 mPas at 100° C., measured according to Brookfield, Digital Viscometer RVT, EN ISO 2555, spindle 27, 10 rpm.

10. A hot melt adhesive according to claim 1 , having an NCO-value of 2 to 12 wt %.

11. A process to manufacture a hot melt adhesive according to claim 1 , comprising:
preparing a low monomer content PU prepolymer;
reacting the prepared low monomer content PU prepolymer with at least one OH-containing alkyl(meth)acrylate monomer in an OH:NCO ratio from 0.7:1 to 1.01:1 to form a PU polymer; and
blending the PU polymer with an NCO-containing PU-prepolymer and a (meth)acrylate polymer.

12. A process to manufacture according to claim 11 , wherein the process is carried out at a temperature of 70 to 120° C.

13. A process to manufacture according to claim 12 , wherein the (meth)acrylate polymer is free of OH and/or NH groups.

14. A process to bond substrates, comprising;
heating the hot melt adhesive according to claim 1 to a molten state;
applying the molten hot melt adhesive onto a first substrate;
exposing the disposed hot melt adhesive to ultraviolet radiation to initiate curing of that hot melt adhesive; and
disposing a second substrate into contact with the disposed hot melt adhesive in a non-solidified state.

15. A process according to claim 14 , wherein the adhesive is applied to the first substrate in an amount of 10 to 500 g/m 2 .

16. Cured reaction products of the hot melt adhesive according to claim 1 .

Assignees

• Henkel Ag & Co Kgaa

Inventors

• Kinzelmann Hans-Georg
• Cao Yang
• Franken Uwe
• Zhao Hongxia

Classifications

• C09J4/06 Primary

  {Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond} in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00 · CPC title

• B32B38/0008

  Electrical discharge treatment, e.g. corona, plasma treatment; wave energy or particle radiation (heat treatment B32B38/0036) · CPC title

• B32B37/18

  involving the assembly of discrete sheets or panels only · CPC title

• C08G2270/00

  Compositions for creating interpenetrating networks · CPC title

• C08G18/7671

  containing only one alkylene bisphenyl group · CPC title