Adhesive derived from dimeric fatty acid or dimeric fatty diol

Abstract

An adhesive containing polyisocyanate and a polyol containing at least one dimer fatty acid and/or dimer fatty diol. The adhesive is particularly suitable for use on wood.

Claims

1. A moisture-curable adhesive, comprising a reaction product of: 1) at least one polyisocyanate; and 2) at least one polyester having a number average molecular weight in the range from 500 to 5,000, wherein the at least one polyester is formed from: a) a carboxylic acid component, comprising: i) 60 to 100% by weight of dimer fatty acids, relative to the weight of the total weight of dicarboxylic acids; and ii) 0 to 40% by weight of non-dimer fatty acids, relative to the weight of the total weight of dicarboxylic acids, wherein the non-dimer fatty acids are aliphatic dicarboxylic acids having terminal carboxyl groups and a 2 to 20 carbon chain; and b) a polyol component; wherein: i) the adhesive comprises an isocyanate content in the range from 11 to 40 wt. %, relative to the weight of the adhesive; and ii) the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 8 MPa of greater than 1,000 seconds in water at 90 C.

2. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a lap shear adhesion value of greater than 8 MPa.

3. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a lap shear adhesion value of greater than 10 MPa.

4. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a lap shear adhesion value of greater than 12 MPa.

5. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 8 MPa of greater than 1,000,000 seconds in air at 23 C.

6. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 6 MPa of greater than 500,000 seconds in air at 23 C.

7. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 4 MPa of greater than 500,000 seconds in air at 23 C.

8. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 8 MPa of greater than 1,500 seconds in water at 23 C.

9. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 8 MPa of greater than 1,500 seconds in water at 90 C.

10. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 6 MPa of greater than 500 seconds in water at 90 C.

11. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 6 MPa of greater than 10,000 seconds in water at 90 C.

12. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 4 MPa of greater than 2,000 seconds in water at 90 C.

13. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value at a stress value of 4 MPa of greater than 500,000 seconds in water at 90 C.

14. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value in water at 90 C. of at least 50% of the value in air at 23 C.

15. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value in water at 90 C. of at least 70% of the value in air at 23 C.

16. The moisture-curable adhesive of claim 1, wherein the adhesive, after curing, comprises a creep rupture adhesion value in water at 90 C. of at least 90% of the value in air at 23 C.

17. The moisture-curable adhesive of claim 1, wherein the dimer is formed from C.sub.14 to C.sub.22 alkyl chains.

18. The moisture-curable adhesive of claim 1, wherein the polyol comprises a polyester.

19. The moisture-curable adhesive of claim 1, wherein the ratio of the at least one polyisocyanate and the at least one polyol is in the range from 20 to 80 wt. %:20 to 80 wt. %.

20. The moisture-curable adhesive of claim 1, wherein the NCO:OH molar ratio of the at least one polyisocyanate and the at least one polyester is in the range from 1.1:1 to 16:1.

21. The moisture-curable adhesive of claim 1, wherein the adhesive comprises from 14 to 30% by weight of dimer fatty acid.

22. The moisture-curable adhesive of claim 1, wherein the at least one polyester has an acid value less than 1.

23. The moisture-curable adhesive of claim 1, wherein the polyol component comprises at least one diol selected from ethylene glycol and propylene glycol.

Description

Example 1

(1) (i) Synthesis of Polyol

(2) 2210 g of Pripol 1017 ((trade mark) dimer acid, C36 dicarboxylic (ex Uniqema)) and 957 g ethylene glycol were reacted in a 4 litre standard distillation unit including separation column at approximately 190 C. for 5.9 hours at atmospheric pressure. The heating time was 3.9 hours, and the maximum temperature of the distillation column was 105 C. After a reaction time of 0.3 hour, 0.26 ml of 0.01 weight % solution of tetra butyl titanate was added. When the reaction mixture reached an acid value of 0.36 mg KOH/g, the excess ethylene glycol was distilled off at a maximum distillation column temperature of 150 C., and a minimum pressure of 2.3 mbar. The resultant oligoester was obtained by filtering at 85 C., and exhibited the following properties, measured as described herein.

(3) (i) The hydroxyl value was 117 mgKOH/g.

(4) (ii) The acid value was 0.28 mgKOH/g.

(5) (i) Synthesis of Adhesive

(6) 100 g of the oligoester produced above was placed into a 500 ml round bottomed flask fitted with a mechanical stirrer, nitrogen inlet, thermocouple, dropping funnel and vacuum take-off line. The oligoester was heated to 120 C. and a vacuum was applied down to 25 mbar, to remove any water from the oligoester. The vacuum was held for 1 hour, and then released by allowing nitrogen into the reactor. The reaction was then cooled to 80 C. and 174 g of liquid VKS20 (MDI (ex Bayer)) was added over a period of 10 minutes from a dropping funnel. The dropping funnel was removed and replaced with a drying tube. The reaction then continued for 2 hours at 80 C., after which time the resin was poured into two glass bottles, flushed with dry nitrogen and sealed. The resulting adhesive had the following properties, measured as described herein;

(7) (i) Lap shear adhesion value was 8 MPa.

(8) (ii) Creep rupture adhesion value at 23 C. in air was >1,000,000 seconds at a stress of 8 MPa.

(9) (iii) Creep rupture adhesion value in water at 90 C. was;

(10) a) 2700 seconds at a stress of 8 MPa,

(11) b) 15,350 seconds at a stress of 6 MPa, and

(12) c) >1,000,000 seconds at a stress of 4 MPa.

Example 2

(13) This is a comparative example not according to the present invention. The procedure of Example 1 was repeated except that 100 g of polypropylene glycol of molecular weight number average 1000 was used as the polyol instead of the oligoester, and reacted with 158.2 g of VKS20. The resulting adhesive had the following properties, measured as described herein;

(14) (i) Lap shear adhesion value was 7 MPa.

(15) (ii) Creep rupture adhesion value at 23 C. in air was >1,000,000 seconds at a stress of 8 MPa.

(16) (iii) Creep rupture adhesion value at 90 C. in water was;

(17) a) 30 seconds at a stress of 8 MPa,

(18) b) 135 seconds at a stress of 6 MPa, and

(19) c) 1920 seconds at a stress of 4 MPa.

(20) The above examples illustrate the improved properties of an adhesive according to the present invention.