Polyurethane with polyether and polyester blocks and alkoxysilane end group

1. A method of preparing a polyurethane with polyurethane-polyether and polyurethane-polyester blocks comprising at least 2 end blocks each consisting of a polyurethane-polyester block joined to an alkoxysilane end group, said method comprising the sequential steps of:

(i) reaction of a mixture of alcohols comprising a polyether polyol (A) with a stoichiometric excess of an aliphatic diisocyanate or an aromatic diisocyanate (B) of the formula:

NCO—R 1 —NCO  (I)

in which R 1 represents a divalent aliphatic or aromatic hydrocarbon radical comprising 5 to 15 carbon atoms which is linear, branched or cyclic, to form a polyurethane-polyether block possessing at least 2 —NCO end groups, then

(ii) reaction of the polyurethane from (i) with a stoichiometric excess of a polyester polyol (C), to form a polyurethane with polyurethane-polyether and polyurethane-polyester blocks comprising at least 2 end blocks each consisting of a polyurethane-polyester block joined to an —OH end group, then

(iii) reaction of the polyurethane with —OH end group from (ii) with a stoichiometric amount of an isocyanatosilane (D).

2. The method of preparing a polyurethane according to claim 1 , wherein the polyether polyol (A) used in (i) is a polyether diol alone or mixed with up to 30 wt. % of a polyether triol, relative to said mixture.

3. The method of preparing a polyurethane according to claim 1 , wherein the polyether polyol (A) is a polypropylene glycol with hydroxyl functionality equal to 2 or 3.

4. The method of preparing a polyurethane according to claim 1 , wherein a polypropylene glycol diol or triol whose polymolecularity index is from 1 to 1.4 is used as polyether polyol (A).

5. The method of preparing a polyurethane according to claim 1 , wherein R 1 is one of the following divalent radicals whose formulae given below show the 2 free valences:

a) a divalent radical derived from isophorone:

b)

c)

—(CH 2 ) 6 — (or hexamethylene radical)

d)

or

e)

6. The method of preparing a polyurethane according to claim 1 , wherein the amounts of the 2 reactants used in step (i) correspond to an —NCO/—OH equivalent ratio between 1.3:1 and 5:1.

7. The method of preparing a polyurethane according to claim 1 , wherein one or more polyester polyols having an —OH functionality of 2 are used in step (ii).

8. The method of preparing a polyurethane according to claim 1 , wherein the amounts of reactants used in step (ii) correspond to an —NCO/—OH equivalent ratio between 0.10:1 and 0.80:1.

9. The method of preparing a polyurethane according to claim 1 , wherein a polyester polyol (C) having a melting point greater than or equal to 55° C. is used in step (ii).

10. The method of preparing a polyurethane according to claim 1 , wherein the isocyanatosilane (D) has the formula:

NCO—R 2 —Si(R 3 ) p (OR 4 ) 3-p   (II)

in which:

R 2 represents a divalent linear alkylene radical comprising 1 to 3 carbon atoms;

R 3 and R 4 , which are identical or different, each independently represent a linear or branched alkyl radical with from 1 to 4 carbon atoms,

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

11. The method of preparing a polyurethane according to claim 1 , wherein the mixture of alcohols used in step (i) comprises at least 80 wt. % based on the mixture of alcohols of a polypropylene glycol diol or triol (A) whose polymolecularity index is from 1 to 1.4; and the polyester polyol (C) used in step (ii) has a melting point greater than or equal to 55° C.

12. A polyurethane with polyurethane-polyether and polyurethane-polyester blocks comprising at least 2 end blocks each consisting of a polyurethane-polyester block joined to an alkoxysilane end group, said polyurethane being obtained by the method as defined in claim 1 .

13. An adhesive composition comprising the polyurethane as defined in claim 12 and from 0.01% to 3% by weight based on the polyurethane of a crosslinking catalyst.

14. A method of assembly of 2 substrates comprising:

melting the adhesive composition as defined in claim 13 , by heating at a temperature between 30 and 120° C., then

coating it, in the form of a layer of thickness between 0.3 and 5 mm, on at least one of the 2 surfaces belonging respectively to the 2 substrates to be assembled and which are intended to be brought into contact with one another during assembly on a faying surface, then, without exceeding a period of time corresponding to the maximum open assembly time of the adhesive composition,

bringing the 2 substrates into effective contact on their faying surface.