CYANATE ESTER BASED ADHESIVE AND METHOD FOR PRODUCING CYANATE ESTER BASED ADHESIVE

Abstract

A cyanate ester based adhesive comprising component A which has at least one cyanate ester with at least two OCN groups, and component B which comprises at least one catalyst for the trimerisation reaction of OCN groups to form a triazine ring. The catalyst is retained releasably on a carrier, particularly a pyrogenic silica.

Claims

1-14. (canceled)

15. A cyanate ester-based adhesive comprising: component A, which includes at least one cyanate ester having at least two OCN groups, and component B, which includes at least one catalyst for the trimerization reaction of OCN groups to form a triazine ring, wherein the at least one catalyst is tin octoate and is retained reversibly on a carrier by physical or chemical adsorption.

16. The cyanate ester-based adhesive according to claim 15, wherein the at least one catalyst is in a non-complexed state.

17. The cyanate ester-based adhesive according to claim 15, wherein the carrier is a pyrogenic silica.

18. A method for producing a cyanate ester-based adhesive according to claim 15, comprising a step a) of: contacting the component A, which includes at least one cyanate ester having at least two OCN groups, and the component B, which includes at least one catalyst comprising tin octoate, for the trimerization reaction of OCN groups to form a triazine ring, in a solution, wherein the catalyst is retained reversibly on the carrier by physical or chemical adsorption.

19. The method according to claim 18, wherein the contacting in step a) takes place at a temperature of 20 to 100 C. for a time of 1 to 10 min.

20. The method according to claim 18, wherein at least one of the component A and the component B is provided as solution in step a).

21. The method according to claim 18, wherein the components A and B are both provided as solids in step a).

22. A method for coating a component with a cyanate ester-based adhesive according to claim 15, comprising the steps of: a) applying a cyanate ester-based adhesive to a substrate, b) applying the component to the cyanate ester-based adhesive applied to the substrate, and c) crosslinking the cyanate ester-based adhesive at a temperature of >100 C.

23. The method according to claim 22, wherein the crosslinking takes place with exclusion of atmospheric moisture.

24. The method according to claim 22, wherein at least one of the substrate and the component are pretreated.

25. The method according to claim 15, wherein the carrier is pyrogenic silica.

26. The method according to claim 18, wherein step a) is followed by step b) of degassing the composition from step a) under reduced pressure.

27. The method according to claim 24, wherein the at least one of the substrate and the component are pretreated by at least one of chemical and physical cleaning.

28. A system according to claim 25, additionally comprising (iii) instructions for use.

Description

EXAMPLES

[0039] Below, aspects of the cyanate ester-based adhesive of the invention and, respectively, of the method for producing the cyanate ester-based adhesive are elucidated in more detail with reference to working examples.

[0040] The materials used are listed below:

TABLE-US-00001 Tradename Material Manufacturer Primaset PT-30 Novolac-based cyanate Lonza ester, 100% solids content Aerosil 200 Pyrogenic silica Evonik WorleeAdd Liquid tin octoate on Worle-Chemie ST-70 an amorphous silicate powder as carrier substance

Comparative Example

[0041] The comparative example concerns the incorporation of tin octoate without an adsorption step on a pyrogenic silica in a cyanate ester-based adhesive. For this example, 245 g of novolac-based cyanate ester with 100% solids content (Primaset PT-30, Lonza) were preheated at 60 C., 0.245 g of tin octoate (Borchi Kat 28) and 9.8 g of pyrogenic silica (Aerosil 200, Evonik) were added, and mixing took place with a laboratory mixer at 750 rpm (revolutions per minute). The mixture was stored at 60 C.

Working Example

[0042] The working example concerns the incorporation of tin octoate, which is retained reversibly on a pyrogenic silica (WorleeAdd ST-70), into a cyanate ester-based adhesive. For this purpose, first 245 g of Primaset PT-30 are preheated in an oven at 60 C. Then 0.355 g of tin octoate, which is retained reversibly on a pyrogenic silica (Worlee-Add ST-70), and 9.7 g of pyrogenic silica (Aerosil 200, Evonik) were added and the mixture was dispersed in a laboratory mixer at 750 rpm. The mixture was stored at 60 C.

[0043] DSC Measurements (Netzsch DSC 204 F1 Phoenix with Autosampler and Intracooler ETK100/A)

TABLE-US-00002 Area Reaction Reaction J/g range [ C.] peak [ C.] Comparative example 578 159 to 330 238/261 Working example 600 170 to 329 264

[0044] The DSC measurements were carried out in a cold-welded, 25 l aluminum crucible with aluminum lid. 9 to 11 mg of an adhesive sample corresponding to the comparative and working examples were weighed out. The measurement was carried out at 25 C. to 400 C. at 10 C./min with synthetic air flushing (40 ml/min), followed by an isothermal step at 400 C. for 5 h with synthetic air purging (40 ml/min).

[0045] Brookfield Viscosity Measurements (Brookfield RVDVI+)

TABLE-US-00003 [mPas] after after after after after after after prep. 1 d 2 d 3 d 4 d 7 d 8 d Comparative 10 300 12 750 16 700 21 300 23 900 31 300 32 750 example Working 12 250 16 100 17 800 16 450 17 100 21 900 21 350 example [mPas] after after after after after 9 d 14 d 15 d 16 d 17 d Comparative 36 250 49 750 >100 000 >100 000 >100 000 example Working 20 900 28 000 31 750 32 550 32 550 example

[0046] The adhesives of the comparative example and working example were stored before the viscosity measurement at 60 C. for a duration as indicated in the table above.

[0047] After 7 months of storage at room temperature (around 20 to 23 C.), the comparative example had a Brookfield viscosity of >100 000 mPas and the working example had a Brookfield viscosity of 23 800 mPas.

[0048] The Brookfield viscosity measurements were carried out according to method B of ASTM D1084-97 (Reapproved 2005) (Standard Test Methods for Viscosity of Adhesives). Measurement here took place with spindle #6 at 20 rpm and 60 C.

[0049] In comparison to the comparative example, the working example according to the invention exhibits significantly improved storage stability. Whereas the cyanate ester-based adhesive of the comparative example exhibits a significantly higher viscosity after just 3 days of storage, and after 15 days it is no longer possible to measure the viscosity, the cyanate ester-based adhesive of the working example has comparatively low viscosity figures over at least 17 days. Accordingly, the adhesive of the working example can be processed for much longer after production.

[0050] The cyanate ester-based adhesives thus produced can be applied using standard commercial hotmelt coating systems at 60 to 90 C. onto fabric (preferably glass) or aluminum foil. In this way the fabrics are coated with a noncrosslinked cyanate ester-based adhesivein other words, there is no crosslinking during the coating of the fabrics. The typical application rates are between 30 and 70 g/m.sup.2. Employed are a gravure roll (Cavitec, Lacom), engraved roller, positive, or screen (System Nordson, Cavitec, J. Zimmer).