PSA of renewable origin with temperature-stable adhesive power

1. A heat-curable adhesive composition comprising:

(a) from 35% to 75% weight/weight of a composition (A) comprising at least 90% weight/weight of polyurethanes bearing hydrolysable alkoxysilane end groups 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 divalent polyester block which is derived from a polyester diol of formula R 2 (OH) 2 by replacing each of the two hydroxyl groups with a free valency;

R 3 represents a linear divalent alkylene radical comprising from 1 to 3 carbon atoms;

R 4 and R 5 , in each case, independently, represent a linear or branched alkyl radical of 1 to 4 carbon atoms;

m is an integer such that the number-average molar mass of the polyurethanes of formula (I) is between 900 Da and 27 kDa; and

p is an integer equal to 0, 1 or 2;

wherein composition (A) is obtained via a process that comprises

preparing a composition (A-1) of polyester diols of formula R 2 (OH) 2 by reacting via a polycondensation reaction:

(i) one or more dimerized fatty acids included in a composition (A-1-1) with an acid number I A of between 190 and 200 mg KOH/g with one or more diols comprising from 2 to 44 carbon atoms and optionally one or more heteroatoms chosen from oxygen and sulfur; or

(ii) one or more dimerized fatty alcohols included in a composition (A-1-2) with a hydroxyl number I OH of between 200 and 220 mg KOH/g with one or more dicarboxylic acids comprising from 4 to 44 carbon atoms and optionally one or more heteroatoms chosen from oxygen and sulfur;

such that said composition (A-1) has a hydroxyl number I OH of between 15 and 35 mg KOH/g and a Brookfield viscosity measured at 80° C. of less than 10 Pa·s;

(b) from 22% to 62% weight/weight of a compatible tackifying resin (B) with a number-average molar mass of between 200 Da and 10 kDa; and

(c) from 0.01% to 3% weight/weight of a crosslinking catalyst (C).

2. The heat-curable adhesive composition according to claim 1 , wherein when composition (A-1) of polyester diols of formula R 2 (OH) 2 is obtained according to variant (i), composition (A-1-1) is a composition comprising from 95% to 98% of dimerized fatty acids with an acid number I A of between 194 and 198 mg KOH/g.

3. The heat-curable adhesive composition according to claim 1 , wherein when composition (A-1) of polyester diols of formula R 2 (OH) 2 is obtained according to variant (ii), composition (A-1-2) is a composition comprising at least 96% of aliphatic dimerized fatty alcohols with an I OH of between 202 and 212 mg KOH/g.

4. The heat-curable adhesive composition according to claim 1 , wherein composition (A-1) of polyester diols of formula R 2 (OH) 2 has a hydroxyl number I OH of between 16 and 25 mg KOH/g and a Brookfield viscosity measured at 80° C. of less than 6 Pa·s.

5. The heat-curable adhesive composition according to claim 1 , wherein R 1 is chosen from one of the following divalent radicals, of which the formulae below reveal the two free valencies:

e) —(CH 2 ) 6 .

6. The heat-curable adhesive composition according to claim 1 , wherein R 1 is

7. The heat-curable adhesive composition according to claim 1 , wherein

R 3 is methylene or n-propylene;

R 4 and R 5 each independently represent methyl or ethyl; and/or

p equals 0 or 1.

8. The heat-curable adhesive composition according to claim 1 , wherein tackifying resin (B) is chosen from:

(iii) rosins of natural or modified origin and hydrogenated, dimerized or polymerized derivatives thereof or derivatives esterified with monoalcohols or polyols; or

(v) terpenic resins in the presence of Friedel-Crafts catalysts.

9. The heat-curable adhesive composition according to claim 1 , wherein said composition comprises:

(a) from 40% to 65% weight/weight of composition (A),

(b) from 33% to 58% weight/weight of tackifying resin (B), and

(c) from 0.45% to 2.5% weight/weight of crosslinking catalyst (C).

10. The heat-curable adhesive composition according to claim 1 , further comprising a polymer of formula (V):

in which:

R 6 represents a divalent hydrocarbon-based radical comprising from 5 to 15 carbon atoms, which is aromatic or aliphatic, and linear, branched or cyclic;

R 7 represents a linear or branched divalent alkylene radical comprising from 1 to 4 carbon atoms;

R 8 represents a linear divalent alkylene radical comprising from 1 to 3 carbon atoms;

R 9 and R 10 , in each case, independently, represent a linear or branched alkyl radical of 1 to 4 carbon atoms;

q is an integer such that the number-average molar mass of a polyether block of formula —[OR 7 ] q — is between 300 Da and 30 kDa;

r is either equal to zero or to a non-zero integer such that the number-average molar mass of the polymer of formula (V) is between 600 Da and 60 kDa; and

s is an integer equal to 0, 1 or 2,

wherein the amount of said polymer of formula (V) is up to 15% weight/weight.

11. The heat-curable adhesive composition according to claim 10 , wherein in the polymer of formula (V) r equals 0.

12. The heat-curable adhesive composition according to claim 10 , wherein in the polymer of formula (V):

R 7 is isopropylene;

R 8 is methylene;

s=0 or 1; and

R 9 and R 10 each represent methyl.

13. The heat-curable adhesive composition according to claim 1 , wherein said composition has a Brookfield viscosity measured at 100° C. of between 9 and 100 Pa·s.

14. A self-adhesive support that is obtained via a process comprising:

(a) preheating the adhesive composition as defined in claim 1 to a temperature of between 50 and 130° C., and then

(b) coating said adhesive composition on a support layer, and then

(c) curing said adhesive composition, by heating the support thus coated to a temperature of between 50 and 150° C.

15. A one-sided or two-sided self-adhesive label or tape comprising the self-adhesive support of claim 14 .

16. The heat-curable adhesive composition according to claim 1 , wherein wherein composition (A) is obtained via a process comprising:

(a) preparing a composition (A-1) of polyester diols of formula R 2 (OH) 2 by reacting via a polycondensation reaction:

(i) one or more dimerized fatty acids included in a composition (A-1-1) with an acid number I A of between 190 and 200 mg KOH/g with one or more diols comprising from 2 to 44 carbon atoms and optionally one or more heteroatoms chosen from oxygen and sulfur; or

(ii) one or more dimerized fatty alcohols included in a composition (A-1-2) with a hydroxyl number I OH of between 200 and 220 mg KOH/g with one or more dicarboxylic acids comprising from 4 to 44 carbon atoms and optionally one or more heteroatoms chosen from oxygen and sulfur;

such that said composition (A-1) has a hydroxyl number I OH of between 15 and 35 mg KOH/g and a Brookfield viscosity measured at 80° C. of less than 10 Pa·s;

(b) preparing a composition (A-2) comprising at least 90% weight/weight of polyurethanes bearing hydroxyl end groups by reacting polyester diol Composition (A-1) with diisocyanate of formula (II):

NCO—R 1 —NCO  (II)

in amounts corresponding to a ratio of the molar equivalent of the number of NCO/OH functions of between 0.3 and 0.7, to obtain polyurethanes bearing hydroxyl end groups of formula (III):

in which m is less than or equal to 10; and

(c) preparing composition (A) comprising at least 90% weight/weight of polyurethanes bearing alkoxysilane end groups of formula (I) by reacting Composition (A-2) of polyurethanes bearing hydroxyl end groups with an isocyanatosilane of formula (IV):

NCO—R 3 —Si(R 4 ) p (OR 5 ) 3-p   (IV)

in an amount corresponding to a ratio of the molar equivalent of NCO/OH functions of between 0.90 and 1.05.

17. The heat-curable adhesive composition according to claim 1 , wherein

R 3 is methylene or n-propylene;

R 4 and R 5 each independently represent methyl or ethyl; and

p equals 0 or 1.

18. The heat-curable adhesive composition according to claim 10 , wherein the polymer of formula (V) has a number-average molar mass ranging from 30 to 40 kDa and a viscosity, measured at 23° C., ranging from 30 to 37 Pa·s.

19. The heat-curable adhesive composition according to claim 10 , wherein the polymer of formula (V) has a polydispersity index ranging from 1 to 2.

20. The heat-curable adhesive composition according to claim 16 , wherein composition (A-1) of polyester diols of formula R 2 (OH) 2 is prepared by reacting, via a polycondensation reaction, one or more dimerized fatty acids included in a composition (A-1-1) with an acid number I A of between 190 and 200 mg KOH/g with one or more diols comprising from 2 to 44 carbon atoms and optionally one or more heteroatoms chosen from oxygen and sulfur.

21. The heat-curable adhesive composition according to claim 16 , wherein composition (A-1) of polyester diols of formula R 2 (OH) 2 is prepared by reacting, via a polycondensation reaction, one or more dimerized fatty alcohols included in a composition (A-1-2) with a hydroxyl number I OH of between 200 and 220 mg KOH/g with one or more dicarboxylic acids comprising from 4 to 44 carbon atoms and optionally one or more heteroatoms chosen from oxygen and sulfur.