Adhesive Composition Comprising a Thixotropic Agent

Abstract

The present invention refers to an adhesive composition comprising a thixotropic agent, a polyurethane adhesive obtained from the adhesive composition as well as to the thixotropic agent comprised in the adhesive composition.

Claims

1. An adhesive composition comprising a component A and a component B, wherein: Component A comprises at least one polyol and a thixotropic agent comprising a hydrogenated castor wax and at least one amide wax; and Component B comprises at least one NCO-terminated compound.

2. The adhesive composition according to claim 1, wherein the adhesive composition or the thixotropic agent is essentially free of silica.

3. The adhesive composition according to claim 1, wherein the at least one amide wax is derived from reaction of a fatty acid with amines and/or diamines.

4. The adhesive composition according to claim 1, wherein the at least one polyol is castor oil.

5. The adhesive composition according to claim 1, wherein the at least one polyol is present in an amount of 60 to 99 wt.-%, based on the total weight of component A.

6. The adhesive composition according to claim 1, wherein the hydrogenated castor wax is present in an amount of 1 to 10 wt.-%, based on the total weight of component A.

7. The adhesive composition according to claim 1, wherein the at least one amide wax is present in an amount of 1 to 10 wt.-%, based on the total weight of component A.

8. The adhesive composition according to claim 1, wherein the hydrogenated castor wax and the at least one amide wax are employed in a weight ratio of 4:1 to 1:4.

9. A polyurethane adhesive made by mixing component A and component B of the adhesive composition of claim 1 to form a mixture, and curing the mixture.

10. An article comprising the polyurethane adhesive of claim 9.

11. The article of claim 10, further comprising a semipermeable membrane, wherein the polyurethane adhesive adheres to the semipermeable membrane.

12. An article comprising cured reaction products of the polyurethane adhesive of claim 9.

13. A spiral wound filter comprising the adhesive composition of claim 1.

14. A polyurethane adhesive made by mixing component A and component B of the adhesive composition of claim 1, in a 1 to 0.8 to 1 to 0.95 weight ratio of component A to component B, to form a mixture, and curing the mixture.

15. A thixotropic agent comprising hydrogenated castor wax and at least one amide wax.

16. The thixotropic agent according to claim 15, characterized in that the hydrogenated castor wax and the at least one amide wax are employed in a weight ratio of 4:1 to 1:4, preferably 3:1 to 1:3.

Description

EXAMPLES

[0030] Component A was prepared as follows:

[0031] The polyol was heated to a temperature of 75 to 85° C. and stirred for one hour before the thixotropic agent was added. In case of inventive example 1 a mixture of hydrogenated castor wax and amide wax in a weight ratio of 1:1 was used as thixotropic agent. In case of inventive example 2, the weight ratio of hydrogenated castor wax and amide wax was 3:1. The properties are summarized in Table 1.

TABLE-US-00001 TABLE 1 Comp.-1 Comp.-2 Comp.-3 Ex 1 Ex 2 Polyol 95 95 95 96 96 [wt.-%] TA* [wt.-%] 5 5 5 4 4 Type TA fumed amide hydrogenated 1:1 3:1 silica wax castor wax viscosity.sup.1) 18000 5200 3500 18500 22000 TI.sup.2) 4.8 2.7 3.1 4.0 4.6 *Thixotropic agent .sup.1)Viscosity given in cps measured at 25° C. according to ASTM D1084 using a Brookfield viscosimeter .sup.2)Thixotropic index measured according to standard procedure.

[0032] As can be seen, a thixotropic agent employing a mixture of hydrogenated castor wax and amide wax affords rheology properties which are comparable to those of fumed silica. However, in contrast to the composition according to comparative example 1 (Comp.-1) which took about 5 hours to degas, degassing was completed after one hour in case of inventive examples 1 and 2 (Ex.-1 and Ex.-2).

[0033] The composition according to Example 2 was reacted with an NCO-terminated compound on the basis of the prepolymer in a mixing ratio of 1:1 (Ex. 4). As a comparison, a commercially available polyurethane adhesive was used (Comp.-4). The properties of both adhesive are summarized in Table 2.

TABLE-US-00002 TABLE 2 Ex. 4 Comp.-4 Viscosity [cps] 20000 17000 TI 4.0 2.0 spreading <40% >60%

[0034] As can be seen, the adhesive according to the invention showed favorable spreading properties. While in case of the inventive adhesive, spreading of the adhesive after application was less than 40%, in case of the commercially available adhesive a spreading of 60% was observed. It was further found that the adhesive according to the invention showed a much better penetration behavior than the comparative adhesive, making the inventive adhesive especially suitable for the production of filter systems.