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.