Robust adhesives for laminating flexible packaging material

1. A two component adhesive suitable for use in transfer roll lamination equipment to make flexible packaging material comprising Component A and Component B; Component A comprising an isocyanate-functionalized polyurethane prepolymer; and Component B comprising a mixture of a high functionality polyol containing at least four hydroxyl groups per molecule with at least two primary OH groups on the molecule and two secondary OH groups on the molecule and a trifunctional polyol containing three OH groups on the molecule; wherein a mixture of Component A and Component B at a predetermined weight ratio has a pot-life based on viscosity doubling of at least about 25 minutes at a temperature of 40° C., a bond strength at 70° C. of at least 200 grams per inch after 24 hours of cure and has a BfR migration after 3 days of cure of less than 2 parts per billion, and each of these properties remains present throughout the range of Component A:Component B weight ratios of 25% less component A than the predetermined weight ratio, to the predetermined weight ratio, to 25 wt % more Component A than the predetermined weight ratio.

2. The laminating adhesive of claim 1 wherein Component B comprises a difunctional polyol containing two OH groups on the molecule.

3. The laminating adhesive of claim 1 wherein the high functionality polyol is a polyester polyol.

4. The laminating adhesive of claim 1 wherein the trifunctional polyol is a polyether polyol.

5. The two component laminating adhesive of claim 1 comprising about 5 wt % to about 20 wt % of a difunctional polyol.

6. The laminating adhesive of claim 1 , wherein the high functionality polyol has the following structure:

(HO) m (R 1 )—O—C(═O)—R 2 —C(═O)—O—(R 3 )(OH) n

wherein m and n are integers which are the same or different and which each have a value of at least 1; m+n=at least 4; and R 1 , R 2 and R 3 are hydrocarbon radicals.

7. The laminating adhesive of claim 1 , wherein the high functionality polyol has the following structure:

(HO) m (R 1 )—O—C(═O)—R 2 —C(═O)—O—(R 3 )(OH) n

wherein m and n are integers which are the same or different and which each have a value of at least 1 and m+n=at least 4;

R 1 is a hydrocarbon radical having 2 to 20 carbon atoms and a valency of m+1 with m OH groups being attached thereto;

R 2 is a hydrocarbon radical having 2 to 20 carbon atoms and a valency of 2;

R 3 is a hydrocarbon radical having 2 to 20 carbon atoms and a valency of n+1 with n OH groups being attached thereto.

8. The laminating adhesive of claim 1 , wherein the high functionality polyol has the following structure:

(HO) m (R 1 )—O—C(═O)—R 2 —C(═O)—O—(R 3 )(OH) n

wherein m and n are integers which are the same or different and which each have a value of at least 1 and m+n=at least 4;

R 1 is a CH 2 —CH—CH 2 — group with a valency of m+1 with m OH groups being attached thereto;

R 2 is a —(CH 2 ) o — moiety, where o is an integer of from 2 to 18; and

R 3 is a CH 2 —CH—CH 2 — group with a valency of n+1 with n OH groups being attached thereto.

9. The laminating adhesive of claim 1 , wherein the high functionality polyol has the following structure:

(HO) q (R 4 )—O—C(═O)—R 5 —C(═O)—O—R 6 —O—C(═O)—R 7 —C(═O)—O—(R 8 )(OH) r

wherein q and r are integers which are the same or different and which each have a value of at least 1; q+r=at least 4; R 4 , R 5 , R 7 and R 8 are hydrocarbon radicals; and R 6 is a divalent radical selected from hydrocarbon radicals and polyoxyalkylene radicals.

10. A flexible packaging material comprising two films bonded together by cured reaction products of the adhesive of claim 1 .

11. A flexible packaging material comprising a first layer comprised of a first polyolefin or first polyester; a second layer comprised of a second polyolefin, which may be the same or different from the first polyolefin, a second polyester, which may be the same as or different from the first polyester, or a metal foil; and cured reaction products of the adhesive of claim 1 bonding the first layer to the second layer.

12. A method of making a flexible film laminate, comprising:

combining Component A and Component B of the laminating adhesive of claim 1 at a predetermined weight ratio to form an adhesive mixture;

disposing the adhesive mixture on at least a portion of one surface of a first flexible film,

joining the first flexible film and a second flexible film wherein the adhesive mixture is interposed between the first flexible film and the second flexible film; and

curing the adhesive mixture.

13. Cured reaction products of the two component adhesive of claim 1 .

14. A method of making a flexible film laminate, comprising:

combining Component A and Component B of the laminating adhesive of claim 1 at a predetermined weight ratio to form an adhesive mixture;

disposing the adhesive mixture on at least a portion of one surface of a first flexible film;

joining the first flexible film and a second flexible film wherein the adhesive mixture is interposed between the first flexible film and the second flexible film; and

curing the adhesive mixture.