THERMOSETTING ADHESIVE FILMS

Abstract

Flexible films of thermosetting adhesive materials which are non-tacky to the touch are storage stable at room temperature and can be cured at elevated temperature with a short cure time and can be cured to produce a tough flexible adhesive layer including bonding to oily surfaces, the materials are particularly useful in bonding together dissimilar substrates.

Claims

1: An article comprising: a curable thermosetting epoxy resin based adhesive film which is flexible prior to cure and storage stable at room temperature, the adhesive film being derived from a mixture of: (a) an elastomer/epoxy resin adduct; (b) a core shell material; and (c) a curing agent.

2: The article according to claim 1, wherein the adhesive film is cured in no more than 45 minutes at a temperature no higher than 190 C.

3: The article according to claim 1, wherein the adhesive film forms an adhesive bond with oily surfaces and a shear strength of the adhesive film when bonded with the oily surfaces is 90% or more of a shear strength of the adhesive film when bonded to a similar surface free of oil.

4: The article according to claim 2, wherein the adhesive film is cured at a temperature in the range of 130 C. to 190 C.

5: The article according to claim 1, wherein the adhesive film is foamable and the adhesive film expands to a size at least 50% greater than a size of the adhesive film in an unfoamed state.

6: The article according to claim 1, wherein the adhesive film has an uncured thickness between 0.2 and 3.0 mm.

7-9. (canceled)

10: The article according to claim 1, wherein the adhesive film contains 5 to 40 wt % of the elastomer/epoxy resin adduct, and 5 to 25 wt % of the core shell material.

11: The article according to claim 1, wherein the article is supported by a carrier.

12: The article according to claim 11, wherein the carrier is a fibrous carrier or fleece selected from: a woven mat, a knit mat, or a random mat; and wherein the fibrous carrier or fleece is derived from: glass, polyester, polyimide, carbon, or aramid fibres.

13: The article according to claim 12, wherein the adhesive film is located on opposing sides of the fibrous carrier prior to curing.

14-28. (canceled)

29: The article according to claim 1, wherein the adhesive film is thixotropic during a curing of the adhesive film.

30: The article according to claim 1, wherein the elastomer/epoxy resin adduct is 40% to 60% elastomer.

31: The article according to claim 12, wherein the fibers within the fibrous layer or fleece are unidirectional.

32: The article according to claim 11, wherein the adhesive film at least partially impregnates the carrier.

33: The article according to claim 1, wherein the article further includes a release liner disposed on the adhesive film so that the article is adapted for reeling and unreeling at room temperature.

34: The article according to claim 1, wherein the adhesive film further contains at least one mono-functional epoxy resin.

35: The article according to claim 10, wherein the adhesive film further contains 0.5 to 40 wt % of one or more fillers.

36: The article according to claim 10, wherein the adhesive film further contains 0.001 to 7 wt % of the curing agent, and the curing agent includes a curing agent accelerator.

37: A process for the manufacture of the article of claim 1, comprising: (a) extruding the adhesive film at a temperature in the range of 70 C. to 120 C.; (b) calendering the adhesive film to a thickness of 0.3 to 2 mm; (c) laminating the adhesive film to one or both sides of a fibrous layer; and (d) cutting the adhesive film into sections of a desired length.

38: The process according to claim 37, wherein the extruding is completed by a twin-screw having a plurality of extruder zones and the plurality of extruder zones vary in temperature; and wherein the calendering is completed at a temperature in the range of 80 C. to 90 C.

Description

EXAMPLE 1

[0169] An adhesive film was prepared by blending the following materials.

TABLE-US-00002 Component % CTBN modified epoxy resin (1600 g/Eq) 6.00% Epoxy resin (900 g/Eq) 5.00% Micronized grade of dicyandiamide (<50 micrometers) 5.00% Aromatic substituted urea (latent accelerator for the 0.60% dicyandiamide cure of epoxy resins) Calcium oxide (<70 micrometers) 5.00% Calcium carbonate (<70 micrometers) 18.40% Epoxy resin (200 g/Eq) 16.00% Methacrylate-butadiene-styrene (MBS) Coreshell impact 16.00% modifier: cross-linked poly (butadiene/styrene) core with a grafted polymethyl methacrylate shell Epoxy Phenol Novolac Resin 8.00% Phenoxy Resin 15.00% Silica (<50 nanometers: 40%) reinforced bisphenol F based 5.00% epoxy resin

[0170] The formulation was extruded from a twin-screw then calendared to make a film as illustrated in FIG. 1 hereto.

[0171] The temperatures in the different extruder zones were:

TABLE-US-00003 Zone 1 30 Zone 2 60 Zone 3 85 Zone 4 110 Zone 5 100 Zone 6 100 Zone 7 90 Zone 8 80 Zone 9 80 Zone 10 80 Zone 11 80

[0172] The temperature of the calendar cylinder is between 80 and 90 C.

[0173] The calendared film had a thickness between 0.3 and 2 mm.

[0174] The adhesive film was used to bond two steel plates. The curing conditions was heating at 165 C. for 20 minutes.

[0175] Lap shear strength: 30 MPa/Cohesive failure

EXAMPLE 2 TAPE MANUFACTURING

[0176] A tacky film (a tape) was made by applying a liquid epoxy resin on at least one of the two surfaces of the Adhesive Film of Example 1.

[0177] The liquid resin used for the tacky coat can be [0178] a Bisphenol-A based epoxy resin or [0179] a Bisphenol-F based epoxy resin

[0180] The liquid resin can also be: [0181] the same than then liquid resin used in the formula of the Adhesive film. [0182] Different from the liquid resin used in the formula of the Adhesive film.

[0183] Example 2A: the liquid resin is a Bisphenol-A based epoxy resin and is the same as the liquid resin used in the formula of the Adhesive film.

[0184] Example 2B: the liquid resin is a Bisphenol-A based epoxy resin and is different from the liquid resin used in the formula of the Adhesive film.

[0185] The mechanical performances of bonded assemblies using the Adhesive Films of Examples or the Adhesive Tapes of Examples 2A and 2B are almost the same. The Adhesive Tapes have a slightly higher lap shear strength and a slightly lower peel strength.

[0186] The manufacture of films according to the present invention is illustrated by reference to the accompanying drawing II in which FIG. 1 shows the manufacturing line comprising an extruder (1) to which the first thermosetting resin system (2) is fed. The first thermosetting resin system is extended at about 80 C. and passes into a calendaring system (3) where it is calendared by passage through pressure rollers (4) to the required thickness.

[0187] Optionally, the calendared extrudate may then pass to a laminate system where it is laminated to a fibrous layer (5) provided from reels (6). As a further option the laminate may then be passed to a coating system where it is coated with a second tacky thermosetting resin (7) supplied from tanks (8) from which it passes to a cutting system (9) where a release liner (10) can be provided on the tacky surface and the film or tape can be cute by a knife (11) into sections (12) of the desired length.

[0188] When the film is to be used without a supporting fibrous layer and without a tacky layer it may pass directly to the cutting station. Similarly if a laminate with a fibrous layer is required without a tacky layer the laminate may pass directly to the cutting station after lamination.