Moisture- and heat-crosslinkable polyurethane-based adhesive composition comprising a low content of isocyanate monomer

Patent metadata

Field	Value
Publication number	US-10428245-B2
Application number	US-201414574620-A
Country	US
Kind code	B2
Filing date	Dec 18, 2014
Priority date	Dec 19, 2013
Publication date	Oct 1, 2019
Grant date	Oct 1, 2019

Abstract

The present invention also relates to a method of preparing said adhesive composition, a self-adhesive support coated with the crosslinked adhesive composition and the use of said support for making labels and/or self-adhesive tapes.

First claim

The invention claimed is:

1. A crosslinkable adhesive composition comprising:
a) from 40 to 60 wt % of at least one polyurethane obtainable by a polyaddition reaction:
of at least one aromatic or aliphatic diisocyanate that is:
a1) isophorone diisocyanate,
a2) 2,4-toluene diisocyanate,
a3) diphenylmethane-2,4′-diisocyanate,
a4) an allophanate derivative of hexamethylene diisocyanate of formula (I):

in which:
p is an integer in the range from 1 to 2;
q is an integer in the range from 0 to 9;
R represents a hydrocarbon chain, saturated or unsaturated, cyclic or acyclic, linear or branched, comprising from 1 to 20 carbon atoms;
R 3 represents a divalent alkylene group, linear or branched, having from 2 to 4 carbon atoms;

or a mixture of said aromatic or aliphatic diisocyanates,
with at least one polyether diol, with or without the presence of at least one reaction catalyst, at a reaction temperature T1 below 95° C., in anhydrous conditions, and in amounts of diisocyanate(s) and of polyether diol(s) leading to an NCO/OH molar ratio, designated r 1 , in the range from 1.6 to 1.9; said polyurethane having formula (II)

in which:
R 1 represents an aliphatic or aromatic divalent group:
a1′) a divalent group derived from isophorone diisocyanate:

a2′) a divalent group derived from 2,4-toluene diisocyanate:

a3′) a divalent group derived from diphenylmethane-2,4′-diisocyanate:

or
a4′) a divalent group derived from an allophanate of hexamethylene diisocyanate (HDI) of formula (III):

in which:
p is an integer in the range from 1 to 2;
q is an integer in the range from 0 to 9;
R represents a hydrocarbon chain, saturated or unsaturated, cyclic or acyclic, linear or branched, comprising from 1 to 20 carbon atoms;
R 3 represents a divalent alkylene group, linear or branched, having from 2 to 4 carbon atoms;

R 2 , which may be identical to or different from R 3 , represents a divalent alkylene group, linear or branched, having from 2 to 4 carbon atoms;
n is a non-zero integer such that the number-average molecular weight of the polyether block of formula [OR 2 ] n — is in the range from 2000 to 12000 g/mol;
m is an integer such that the number-average molecular weight of the polyurethane is in the range from 3000 to 21000 g/mol;
b) from 39 to 59 wt % of at least one compatible tackifying resin, with a number-average molecular weight in the range from 200 Da to 5000 Da, and selected from the resins obtained by one of the following methods:
b1) polymerization of terpene hydrocarbons in the presence of Friedel-Crafts catalysts, followed by reaction with phenols,
b2) polymerization of alpha-methylstyrene, followed by reaction with phenols; and
c) from 0.01 to 1 wt % of at least one crosslinking catalyst, said percentages being expressed by weight relative to the total weight of the adhesive composition.

2. The adhesive composition according to claim 1 , wherein the allophanate derivative of hexamethylene diisocyanate of formula (I) is in the form of a composition in which it is comprised at a level of at least 99.5 wt %, said composition comprising less than 0.5 wt % of hexamethylene diisocyanate relative to the total weight of said composition.

3. The adhesive composition according to claim 1 , wherein the at least one polyether diol has a number-average molecular weight in the range from 2000 to 12000 g/mol.

4. The adhesive composition according to claim 1 , wherein the at least one polyether diol is a polyoxypropylene diol with a polydispersity index in the range from 1 to 1.4.

5. The adhesive composition according to claim 1 , comprising:
a) from 40 to 60 wt % of the polyurethane of formula (II), in which:
R 1 represents the divalent group derived from 2,4-toluene diisocyanate,
R 2 represents the divalent propylene group,
n is a non-zero integer such that the number-average molecular weight of the polyether block of formula [OR 2 ] n — is in the range from 3500 to 8500 g/mol,
m is an integer such that the number-average molecular weight of the polyurethane is in the range from 4600 to 16800 g/mol;

b) from 39 to 59 wt % of the compatible tackifying resin, with a number-average molecular weight in the range from 200 Da to 5000 Da, that is a resin obtained by method b2); and
c) from 0.01 to 1 wt % of the least one crosslinking catalyst,

relative to the total weight of the adhesive composition.

6. The adhesive composition according to claim 1 , comprising less than 0.5 wt % of unreacted aliphatic diisocyanate monomer, and less than 0.1 wt % of unreacted aromatic diisocyanate monomer, relative to the total weight of the adhesive composition.

7. The adhesive composition according to claim 1 , having a total content of NCO group in the range from 0.15 to 1.7 wt % relative to the total weight of the adhesive composition.

8. A method of preparing a composition as defined in claim 1 , comprising mixing the at least one polyurethane the at least one tackifying resin and the at least one crosslinking catalyst.

9. A self-adhesive support obtainable by a method comprising:
(i′) preheating the adhesive composition as defined in claim 1 to a temperature T4, in order to make it liquid, and then
(ii′) coating said adhesive composition on a support layer, and
(iii′) crosslinking said adhesive composition by heating the coated support to a temperature T5 in the range from 70° C. to 150° C., in the presence of humidity.

10. A label and/or self-adhesive tape comprising the self-adhesive support as defined in claim 9 .

Assignees

• Bostik Sa

Inventors

• Michaud Guillaume
• Simon Frederic

Classifications

• C08G18/7837

  containing allophanate groups · CPC title

• C08G18/307

  Atmospheric humidity · CPC title

• C09J175/04

  Polyurethanes · CPC title

• C09J175/08

  from polyethers · CPC title

• C08G2170/40

  Compositions for pressure-sensitive adhesives · CPC title