Self-adhesive of renewable origin with temperature-stable adhesive power
Heat-curable adhesive composition: 47-60% of polyether/polyurethane bearing alkoxysilane end groups and polyurethanes bearing alkoxysilane end groups of formula (II): in which: R 6 is a divalent C5-C15 hydrocarbon-based radical; R 7 is a divalent C1-C3 alkylene radical; R 8 and R 9 are a C1-C4 alkyl; q is 0, 1 or 2; r is such that the number-average molar mass of the polymers of formula (II) is between 900 Da and 11 kDa; R 10 is a divalent polyester block with a hydroxyl number I OH of between 40 and 60 mg KOH/g; 37-50% of a compatible tackifying resin; and 0.01-3% of a crosslinking catalyst.
1. A heat-curable adhesive composition comprising:
(α) from 47% to 60% weight/weight of a composition (A) comprising polymers bearing hydrolyzable alkoxysilane end groups which composition (A) is:
from 10% to 50% weight/weight of a polymer (A1) of formula (I):
in which:
R 1 represents a divalent hydrocarbon-based radical comprising from 5 to 15 carbon atoms, which may be aromatic or aliphatic, and linear, branched or cyclic;
R 2 represents a linear or branched divalent alkylene radical comprising from 1 to 4 carbon atoms;
R 3 represents a linear divalent alkylene radical comprising from 1 to 3 carbon atoms;
R 4 and R 5 , which may be identical or different, each represent a linear or branched alkyl radical of 1 to 4 carbon atoms;
n is an integer such that the number-average molar mass of the polyether block of formula —[OR 2 ] n — is between 300 Da and 30 kDa;
m is either equal to 0 or a non-zero integer such that the number-average molar mass of the polymer of formula (I) is between 600 Da and 60 kDa;
p is an integer equal to 0, 1 or 2; and
from 50% to 90% weight/weight of a composition (A2) comprising at least 85% weight/weight of polyurethanes bearing hydrolysable alkoxysilane end groups of formula (II):
in which:
R 6 represents a divalent hydrocarbon-based radical comprising from 5 to 15 carbon atoms, which may be aromatic or aliphatic, and linear, branched or cyclic;
R 7 represents a linear divalent alkylene radical comprising from 1 to 3 carbon atoms;
R 8 and R 9 , which may be identical or different, each represent a linear or branched alkyl radical of 1 to 4 carbon atoms;
q is an integer equal to 0, 1 or 2;
r is a number such that the number-average molar mass of the polymers of formula (II) is between 900 Da and 11 kDa;
R 10 represents a divalent polyester block of formula (III):
in which:
R 11 represents a divalent hydrocarbon-based radical which is derived from a dimerized fatty alcohol by replacement of each of the two hydroxyl groups with a free valency, the said alcohol having a hydroxyl number I OH of between 200 and 220 mg KOH/g;
R 12 represents a divalent hydrocarbon-based radical which is derived from a dimerized fatty acid by replacement of each of the two carboxyl groups —COOH with a free valency, the said acid having an acid number I A of between 190 and 200 mg KOH/g;
s is a number such that the polyester diol of formula IV:
OH—R 10 —OH (IV)
has a hydroxyl number I OH of between 40 and 60 mg KOH/g;
(β) from 37% to 50% weight/weight of a compatible tackifying resin (B) with a number-average molar mass of between 200 Da and 10 kDa; and
(γ) from 0.01% to 3% weight/weight of a crosslinking catalyst (C).
2. The heat-curable adhesive composition according to claim 1 , wherein polymer (A1) is a polyether, corresponding to formula (I) in which m equals 0.
3. The heat-curable adhesive composition according to claim 1 , wherein in polymer (A1):
R 4 and R 5 , which may be identical or different, each represent a methyl or ethyl radical;
R 2 is ethylene, isopropylene, n-propylene, n-butylene, or ethylethylene.
4. The heat-curable adhesive composition according to claim 1 , wherein in the polymers of formula (II) the hydroxyl number I OH of the polyester diol of formula (IV) corresponding to the divalent polyester radical R 10 varies within a range from 45 to 55 mg KOH/g.
5. The heat-curable adhesive composition according to claim 1 , wherein in the polymers of formula (II) the dimerized fatty acid from which the radical R 12 is derived has an acid number I A of between 194 and 198 mg KOH/g.
6. The heat-curable adhesive composition according to claim 1 , wherein in the polymers of formula (II) the dimerized fatty alcohol from which the radical R 11 is derived has a hydroxyl number I OH of between 202 and 212 mg KOH/g.
7. The heat-curable adhesive composition according to claim 1 , wherein in the polymers of formula (II) the radical R 6 is one of the following divalent radicals for which the formulae below reveal the two free valencies:
a) a divalent radical derived from isophorone:
8. The heat-curable adhesive composition according to claim 1 , wherein in the polymers of formula (II) the radical R 6 is a divalent radical derived from isophorone.
9. The heat-curable adhesive composition according to claim 1 , wherein in the polymers of formula (II):
R 7 is a divalent methylene or n-propylene radical;
R 8 and R 9 each represent a methyl or ethyl radical; and/or
q equals 0 or 1.
10. The heat-curable adhesive composition according to claim 1 , wherein composition (A) is from 10% to 30% weight/weight of polymer (A1) and from 70% to 90% weight/weight of composition (A2).
11. The heat-curable adhesive composition according to claim 1 , wherein the tackifying resin (B) is:
(iii) rosins of natural or modified origin, or
(v) terpenic resins, resulting from the polymerization of terpenic hydrocarbons.
12. The heat-curable adhesive composition according to claim 1 , comprising:
(α) from 50% to 55% weight/weight of composition (A) of polymers bearing hydrolysable alkoxysilane end groups,
(β) from 43% to 48% weight/weight of tackifying resin (B), and
(γ) from 0.45% to 2.5% weight/weight of crosslinking catalyst (C).
13. The heat-curable adhesive composition according to claim 1 , having a Brookfield viscosity measured at 100° C. between 10 and 100 Pa·s.
14. A self-adhesive support obtained via the process comprising:
(a) preheating to a temperature of between 50 and 130° C. the adhesive composition as defined in claim 1 , and then
(b) coating it onto a support layer, and then
(c) curing it, by heating the support thus coated to a temperature of between 50 and 150° C.
15. One-sided or two-sided self-adhesive labels or tapes, comprising in said labels or tapes the self-adhesive support as defined in claim 14 .
16. The heat-curable adhesive composition according to claim 11 , wherein the tackifying resin (B) is rosin extracted from pine gum, wood rosin extracted from tree roots or hydrogenated, dimerized or polymerized derivatives thereof or derivatives esterified with monoalcohols or polyols.
17. The heat-curable adhesive composition according to claim 16 , wherein (B) is glycerol.
18. The heat-curable adhesive composition according to claim 11 , wherein (B) is a terpenic resin resulting from the polymerization of monoterpene in the presence of a Friedel-Craft catalyst.