ADHESIVE COMPOSITION BASED ON POLYLACTIDE POLYOLS

Abstract

A two-part laminating adhesive including a Part A polyol component and a Part B isocyanate component. The polyol component includes a polylactide polyol as a first polyol, and the isocyanate component includes an isocyanate-terminated polyurethane prepolymer. The adhesive is suited for making flexible laminates for use in packaging including food packaging.

Claims

1. A two-part laminating adhesive comprising Part A, a polyol component comprising a first polyol that is a polylactide polyol, and Part B, an isocyanate component the Part B being present relative to the Part A at an NCO/OH ratio of at least about 1.

2. The adhesive of claim 1, wherein the potylactide polyol is a reaction product of a facade and a hydroxyl-functional initiator selected from the group consisting of glycerol, a fatty acid monoglyceride, a fatty acid diglyceride, and combinations thereof.

3. The adhesive of claim 1, wherein the polyactide polyol has a number average molecular weight of from about 500 g/mole to about 10,000 g/mole.

4. The adhesive of claim 1, wherein the polylactide polyol has a hydroxyl (OH) functionality of no greater than 3.

5. The adhesive of claim 2, wherein the fatty acid of the fatty acid monoglyceride and the fatty acid diglyceride has a saturated or unsaturated aliphatic hydrocarbon chain comprising from 6 to 32 carbon atoms.

6. The adhesive of claim 2, wherein the fatty acid of the fatty acid monoglyceride and the fatty acid diglyceride is selected from stearic acid, oleic acid, linoleic acid, and combinations thereof.

7. The adhesive of claim 1, wherein the polyol component further comprises an additional polyol that is different from the polylactide polyol.

8. The adhesive of claim 1, wherein the polyol component further comprises and additional polyol selected from the group consisting of dipropylene glycol, polypropylene glycol, diethylene glycol adipate, and combinations thereof.

9. The adhesive of claim 1, wherein Part B is present relative to Part A at an NCO/OH ratio of from about 1:1 to about 1.5:1.

10. The adhesive of claim 1, wherein Part A has a viscosity of no greater than 20,000 cps at 25 C.

11. The adhesive of claim 1, wherein Part B has a viscosity of no greater than 10,000 cps at 25 C.

12. The adhesive of claim 1, wherein Part A further comprising a catalyst.

13. The adhesive of claim 1, wherein the isocyanate component is an isocyanate-terminated polyurethane prepolymer that is a reaction product of a second polyol and a polyisocyanate, the prepolymer having a percentage isocyanate (NCO%) of from about 4% to about 25% based on the weight of the prepolymer.

14. The adhesive of claim 13, wherein the second polyol is a polylactide polyol.

15. A method of making a laminate that comprises a first substrate and a second substrate, the method comprising Preparing an adhesive mixture by combining the Part A and the Part B of the two-part, adhesive of claim 1, applying the adhesive mixture to a surface of the first substrate to form an adhesive bearing surface of the first substrate, and contacting a surface of the second substrate with the adhesive bearing surface of the first substrate to form the laminate.

16. The method of claim 15, wherein the first and the second substrates are the same or different material, at least one of the first and the second substrates comprises polyethylene, polypropylene, polyester, polylactic acid, nylon, ethylene-methacrylic acid ionomers, aluminum foil, metalized material, paper, laminates thereof, and combinations thereof.

17. The method of claim 15, further comprising curing the adhesive mixture.

18. A laminate, comprising a first substrate, and a second substrate, the first substrate being adhered to the second substrate through the adhesive of claim 1,

19. The laminate of claim 18, wherein the first and the second substrates are the same or different material, at least one of the first and the second substrates comprises polyethylene, polypropylene, polyester, polylactic acid, nylon, ethylene-methacrylic acid ionomers, aluminum foil, metalized material, paper, laminates thereof, and combinations thereof.

20. A packaged food article, comprising a laminate of claim 19 in a form of a food package, and a food product contained inside of the food package.

Description

EXAMPLES

[0075] Test Methods

Viscosity

[0076] The viscosity is determined using a Brookfield Programmable Rheometer Model DV-III using Spindle #27 at 20 RPM and about 10.5 gram (g) of sample material at 25 C.1 C. and 40 C.1 C.

Initial Viscosity

[0077] Initial viscosity of an adhesive is determined using a Brookfield Programmable Rheometer Model DV-III using Spindle #27 at 20 RPM, and about 10.5 gram (g) of sample material at 40 C.1 C.

Average Molecular Weight

[0078] Weight average molecular weight (M.sub.w) and number average molecular weight (M.sub.n) are determined according to ASTM D 5296-05 entitled Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution of Polystyrene by High Performance Size Exclusion Chromatography.

Glass Transition Temperature (Tg)

[0079] Glass transition temperature (Tg) is determined by ASTM D3418-03 entitled Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry.

Hydroxyl (OH) Number

[0080] Hydroxyl number (OH number) is determined by ASTM E 222-00 entitled Standard Test Method for Hydroxyl Groups Using Acetic Anhydride Acetylation.

Percent Isocyanate (NCO%)

[0081] Percentage isocyanate (NCO%) of a prepolymer is determined by ASTM D2572-97 entitled Standard Test Method for Isocyanate Groups in Urethane Materials or Prepolymers.

Peel Adhesion Test

[0082] Peel adhesion test is conducted on a laminate placed in a controlled 25 C./50% relative humidity room to cure after lamination and during the testing window using a Thwing-Albert Friction/Peel Tester Model 225-1. Prior to the test, a laminate made of two substrates bonded through an adhesive composition at a coat weight of from about 1.2 gsm to about 2 gsm is cut into 25 mm250 mm sample strips. Each of the strips is separated at one end and then peeled at a speed of 300 mm/minute for 20 seconds. The peel strength in g/25 mm is recorded. An average of three (3) samples is reported.

Examples

Polyol Component

[0083] The following polyol components were used as Part A for making the adhesives to be tested in the Examples.

Polyol Component 1 (PC-1)

[0084] A polylactide polyol was prepared by reacting 2157 grams of OLYGOS DMR (a mixture of meso-, L-, and D-lactides at a ratio of meso-lactide to combined L- & D-lactides at 2:1) with 1342 grams of glycerol monostearate (from ChemPacific) at 248 F. for 4 hours in the presence of 1.5 grams of DABCO T-9 ((Sn(Oct).sub.2, catalyst from Air Product). After 4 hours, the catalyst was neutralized with an equal weight of H.sub.3PO.sub.4 (85% aq.) and the mixture was sparged with dry nitrogen gas for 1 hour at 248 F. The viscosity of the resultant polylactide polyol was measured to be about 2,650 cps at 40 C. The weight average molecular weight (M.sub.w) was measured to be about 1,000 g/mole, and the hydroxyl (OH) number is 120. The resultant polylactide polyol was a semi-solid at 25 C.

Polyol Component 2 (PC-2)

[0085] Polyol Component 2 was prepared by mixing PC-1 with dipropylene glycol (DPG) in a weight ratio of 90:10 PC-1:DPG. The viscosity of the PC-2 was measured to be 8,113 cps at 25 C. and 1,063 cps at 40 C.

Polyol Component 3 (PC-3)

[0086] Polyol Component 3 was prepared by mixing PC-1 with polypropylene glycol (PPG, MW: 2000, OH number: 56.1) in a weight ratio of 90:10 PC-1:PPG. The viscosity of the PC-3 was measured to be 1,675 cps at 40 C. The PC-3 is a semi-solid at 25 C.

Polyol Component 4 (PC-4)

[0087] Polyol Component 4 was prepared by mixing PC-1 with VORANOL 230-238 (PPG, from Dow Chemical) in a weight ratio of 90:10 PC-1:PPG. The viscosity of the PC-4 was measured to be 15,900 cps at 25 C. and 1,788 cps at 40 C.

Prepolymer A (P-A)

[0088] Prepolymer A was prepared by reacting 1146 grams of the polylactide polyol made as described above as PC-1 with 1854 grams of MONDUR MLQ (50/50 mixture of 2,4- and 4,4-MDI, from Bayer) at NCO/OH ration of 5.65:1 at 75 C. for 1.5 hours. The final percent isocyanate was measured at 17.68% and the viscosity was 9,012 cps at 25 C. and 1,337 cps at 40 C.

Prepolymer B (P-B)

[0089] Prepolymer B was prepared by reacting a mixture of 143 grams polypropylene glycol (PPG, MW: 2000, OH number: 56.1) and 563 grams of PC-1 with 1093 grams of MONDUR MLQ (50/50 mixture of 2,4- and 4,4-MDI) at NCO/OH ratio of 6.10:1 at 75 C. for 1.5 hours. The final percent isocyanate was measured at 17.68% and the viscosity was 4,977 cps at 25 C. and 887.5 cps at 40 C.

Examples 1-5

[0090] Each adhesive composition of Examples 1-5 was prepared by combining Part A and Part B, according to Table 1, at an NCO/OH ratio of 1.25:1 and room temperature prior to the lamination.

TABLE-US-00001 TABLE 1 Initial Part A Part B Viscosity (cps (grams) (grams) at 40 C.) Ex. 1 PC-1 (500) P-A (427) 2250 Ex. 2 PC-2 (500) P-A (527) 1863 Ex. 3 PC-3 (500) P-A (332) 1975 Ex. 4 PC-4 (500) P-A (370) 2138 Ex. 5 PC-2 (500) P-B (527) 1438

Example 6 (Laminate)

[0091] Laminates of various film substrates were prepared by applying an adhesive according to Table 2 at a coat weight of from about 1.2 gsm to about 2 gsm to a major surface of a first film substrate according to Table 2 at an application temperature of 105 F. via roll-to-roll coating. The adhesive-bearing film substrate was then laminated to a second film substrate according to Table 2. The peel strength of each laminate was measured according to the herein described Peel Adhesion test method within 24 to 72 hours of lamination. The test results are also shown in Table 2.

TABLE-US-00002 TABLE 2 First substrate Second substrate Adhesive Peel Strength OPP OPP Control* Destruct** PET PE Control* Destruct OPP OPP 1 Destruct PET PE 1 Destruct OPP OPP 2 Destruct PET PE 2 Destruct OPP OPP 3 Destruct PET PE 3 Destruct OPP OPP 4 Destruct PET PE 4 Destruct OPP OPP 5 Destruct PET PE 5 Destruct *Fiextra Fast WD4120/XR1500, Commercially available from HB Fuller (St. Paul, MN) ** Destruct means that the substrate(s) tore before the adhesive bond failed, OPP: oriented polypropylene PET: polyethylene terephthalate PE: polyethylene

[0092] Table 2 shows that the adhesives of the invention exhibited very good adhesion with a variety of substrates.

[0093] The above specification, examples and data provide a complete description of the disclosure. Since many embodiments can be made without departing from the spirit and scope of the disclosure, the invention resides in the claims hereinafter appended.