REACTIVE HOT-MELT ADHESIVE COMPOSITION CONTAINING A POLYESTER-POLYURETHANE

Abstract

A reactive hot-melt adhesive composition is provided which is the product of a reaction mixture comprising a polyester-polyurethane intermediate, optionally crystalline and/or amorphous polyesters or polyethers, and an excess of isocyanate groups. The inclusion of the polyester-polyurethane intermediate in the reactive hot-melt adhesive composition allows the properties of the adhesive composition to be customized for various applications.

Claims

1. A reactive hot-melt adhesive composition comprising the reaction product of: (A) a polyester-polyurethane intermediate comprising the reaction product of (i) a hydroxyl-functional polyester having a molecular weight of about 4,000 Daltons or lower measured by assay of terminal functional groups and (ii) a first polyisocyanate wherein a ratio of isocyanate groups from the first polyisocyanate to hydroxyl groups from the hydroxyl-functional polyester is about 0.4:1 to about 0.75:1; and (B) a second polyisocyanate.

2. The reactive hot-melt adhesive composition of claim 1 wherein the hydroxyl-functional polyester polyol comprises the reaction product of a alkylene glycol with a dicarboxylic acid.

3. The reactive hot-melt adhesive composition of claim 2 wherein the dicarboxylic acid is selected from adipic acid, sebacic acid, and succinic acid, and mixtures thereof.

4. The reactive hot-melt adhesive composition of claim 2 the alkylene glycol is selected from 1,2-ethylene glycol, 1,4-butanediol, 1,6-hexane diol and mixtures thereof.

5. The reactive hot-melt adhesive composition of claim 1, wherein the hydroxyl-functional polyester polyol comprises polycaprolactone.

6. The reactive hot-melt adhesive composition of claim 1, further comprising: a crystalline polyester.

7. The reactive hot-melt adhesive composition of claim 1 further comprising: an amorphous polyester polyol having a Tg less than 25 C. measured by DSC.

8. The reactive hot-melt adhesive composition of claim 1 further comprising: an amorphous polyester polyol having a Tg greater than 25 C. measured by DSC.

9. The reactive hot-melt adhesive composition of claim 1 further comprising: an amorphous polyether polyol.

10. The reactive hot-melt adhesive composition of claim 1 wherein the polyester-polyurethane intermediate has a molecular weight of 8,000 Daltons or less as measured by assay of terminal functional groups.

11. The reactive hot-melt adhesive composition of claim 1, wherein the second polyisocyanate is present in an amount sufficient to provide an NCO:OH ratio of 1.5:1 to 2.5:1.

12. The reactive hot-melt adhesive composition of claim 1, wherein the polyester-polyurethane intermediate having the formula: ##STR00002## wherein n is 0-6, m is 2-14, p is 3-27, and R is derived from the first isocyanate component.

13. The reactive hot-melt adhesive composition of claim 12, wherein R is derived from hexamethylene diisocyanate, methylene dicyclohexyl diisocyanate , isophorone diisocyanate, tolyl diisocyanate, or methylenediphenyl diisocyanate.

14. A method of making a reactive hot-melt composition comprising: preparing a polyester polyurethane intermediate by reacting (i) a hydroxyl-functional polyester having a molecular weight of about 4,000 Daltons or lower measured by assay of terminal functional groups and (ii) a first polyisocyanate wherein a ratio of isocyanate groups from the first polyisocyanate to hydroxyl groups from the hydroxyl-functional polyester is about 0.4:1 to about 0.75:1; preparing an isocyanate functional polyurethane prepolymer from a reaction mixture comprising the polyester polyurethane intermediate and a second polyiscyanate, wherein the second polyisocyanate is present in an amount sufficient to provide an NCO:OH ratio of 1.5:1 to 2.5:1.

15. The method of claim 14 wherein the reaction mixture further comprises a crystalline polyester.

16. The method of claim 14, wherein the reaction mixture further comprises an amorphous polyester polyol having a Tg less than 25 C. measured by DSC.

17. The method of claims 14, wherein the reaction mixture further comprises an amorphous polyester polyol having a Tg greater than 25 C. measured by DSC.

18. The method of claim 14, wherein the reaction mixture further comprises an amorphous polyether polyol.

19. A polyester polyurethane additive for reactive hot-melt adhesive compositions, having the formula ##STR00003## wherein n is any integer from 0-6, m is any integer from 2-14, p is any integer from 3-27, and R is derived from hexamethylene diisocyanate, methylene dicyclohexyl diisocyanate, isophorone diisocyanate, tolyl diisocyanate, or methylenediphenyl diisocyanate.

20. The polyester polyurethane additive of claim 19, wherein the polyester-polyurethane additive has molecular weight of 8,000 Daltons or less as measured by assay of terminal functional groups.

21. The polyester polyurethane intermediate additive of claim 19, wherein the polyester polyurethane additive is formed from the reaction product of (i) a hydroxyl-functional polyester having a molecular weight of about 4,000 Daltons or lower measured by assay of terminal functional groups and (ii) a first polyisocyanate wherein a ratio of isocyanate groups from the first polyisocyanate to hydroxyl groups from the hydroxyl-functional polyester is about 0.4:1 to about 0.75:1.

Description

EXAMPLES

[0035] Exemplary polyester-polyurethane intermediates according to Examples 1-9 as shown in Table 1.

TABLE-US-00001 TABLE 1 Isocyanate in Polyester- NCO: Example Polyester Polyurethane OH Comp. A Poly (hexanediol adipate) None Comp. B Poly (hexanediol dodecanoate) None Example 1 Poly (butanediol succinate) MDI 0.7 MW 1000-1200 Example 2 Poly (butanediol succinate-co-sebacate) MDI 0.6 (90:10) Mw 1000-1200 Example 3 Poly (butanediol succinate-co-sebacate) MDI 0.5 (80:20) MW 1800-2200 Example 4 Poly (butanediol succinate) MDI 0.5 MW 1800-2200 Example 5 Poly(butanediol sebacate) MDI 0.7 MW 1600-2000 Example 6 Poly (butanediol-co-propanediol MDI 0.5 (90:10) succinate) MW 1600 Example 7 Poly (butanediol succinate) HDI 0.5 MW 1600 Example 8 Polycaprolactone MDI 0.5 MW 2000 Example 9 Poly (butanediol succinate-co-sebacate) MDI 0.7 (75:25) MW 1000

[0036] Reactive hot-melt adhesive compositions were made using a standard reaction mixture of the following: Crystalline polyester: 29%, Solid Amorphous Polyester: 40%, Liquid Amorphous Polyester: 20%, Polyisocyanate: 11%. The components were combined to have a NCO:OH ratio of 2.2:1. In Comparative Examples A and B, standard crystalline polyester polyols as noted in Table 1 were used in the reaction mixture. In Examples 1-9, the crystalline polyester was replaced with the polyester-polyurethane intermediate of the present invention.

[0037] Each reactive-hot melt composition was evaluated to determine the Setting Time, Open Time, Softening Point, and Green Stength. The results are summarized in Table 2. Setting time was measured by heating a sample of the reactive-hot melt composition in an oven (T=140 C.) for 45 minutes. 1 gram of the sample was placed on a first wooden board using a 100 m extensor rod. The sample was spread to cover a 2.5 cm section at the end of the board. The end of a second wooden board is placed horizontally on the surface of the first wooden board and the boards pressed together until the surfaces of both boards are wet. The boards are turned slightly at 15 second intervals, until the boards will no longer slide against each other. The point at which no sliding occurs is called the Setting Time. Open time was measured by placing the sample and a 100 m extensor rod in an oven at 140 C. for 45 minutes. Using the extensor, a coating line about 20-25 cm long of the sample was placed on the paper. Stops of paper are placed onto the coating every 30 seconds over a 15 minute period. The sample is allowed to dry for 24 hours. Then, the strips of paper are removed from the sample in the reverse order of their application. The open time value is the time of application of the strip of paper that tears first due to the adhesion to the sample. Softening point was measured by UNE-EN1238. Green strength was measured by ASTM D1002.

TABLE-US-00002 TABLE 2 Free Setting Open Softening Green Strength NCO time time point R&B (N/mm) Example (%) (sec) (sec) ( C.) 1 min 3 min 24 h Comp. A 1.9 2400 3540 67 NA. N.A. N.A. Comp. B 2.0 10 900 77 6.5 7.2 >84 Example 1 1.7 13 1020 112 7.9 7.9 >83 Example 2 1.9 49 >57600 93 4.3 4.8 >83 Example 3 1.9 28 2100 95 3.6 4.5 >83 Example 4 1.9 24 850.0 114 5.6 6.0 >83 Example 5 2.0 22 420 69 2.7 3.1 >84 Example 6 2.0 70 3300 100 6.8 7.2 >83 Example 7 1.9 40 600 112 3.7 4.2 >83 Example 8 2 110 >57600 60 2.2 3.0 >84 Example 9 1.9 110 >18000 72 3.5 4 >83

[0038] Examples 1-9 illustrate that certain characteristics of a reactive hot-melt adhesive composition can be improved by the inclusion of a polyester-polyurethane intermediate component in accordance with the present invention. In addition, Examples 1-9 illustrate that the characteristics of an adhesive composition can be customized by including a polyester-polyurethane component in accordance with the present invention without changing the basic reactive hot-melt formulation.

[0039] Each of the documents referred to above is incorporated herein by reference, including any prior applications, whether or not specifically listed above, from which priority is claimed. The mention of any document is not an admission that such document qualifies as prior art or constitutes the general knowledge of the skilled person in any jurisdiction. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word about. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements.

[0040] As used herein, the transitional term comprising, which is synonymous with including, containing, or characterized by, is inclusive or open-ended and does not exclude additional, un-recited elements or method steps. However, in each recitation of comprising herein, it is intended that the term also encompass, as alternative embodiments, the phrases consisting essentially of and consisting of, where consisting of excludes any element or step not specified and consisting essentially of permits the inclusion of additional un-recited elements or steps that do not materially affect the basic and novel characteristics of the composition or method under consideration.

[0041] While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. In this regard, the scope of the invention is to be limited only by the following claims.