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. A curable thermosetting epoxy resin based adhesive composition which is formulated to adhesively bond with oily surfaces after curing, and which comprises: i) a liquid epoxy resin; ii) a phenoxy resin in an amount of 15 to 40 wt % of the composition; iii) a core shell polymer in an amount of 5 to 30 wt. % of the composition; iv) a thermally activated curing agent in an amount of 0.001 to 7 wt. % of the composition; v) a toughener; and vi) a filler; wherein the adhesive composition is storage stable at room temperature, and is in an extrudate form having: (a) an uncured thickness between 0.2 and 3.0 mm, (b) a density of from 1.1 to 1.5 g/ml, or both (a) and (b).

2-28. (canceled)

29. The composition of claim 1 wherein the toughener includes a material selected from an elastomer/epoxy resin adduct, a polyether sulfone, or a combination thereof.

30. The composition of claim 1, wherein a metal oxide is present in the composition.

31. The composition of claim 29, wherein a metal oxide is present in the composition.

32. The composition of claim 30, wherein the metal oxide includes calcium oxide.

33. The composition of claim 31, wherein the metal oxide includes calcium oxide.

34. The composition of claim 1, wherein a mono-functional epoxy resin reactive diluent is present in the composition.

35. The composition of claim 30, wherein a mono-functional epoxy resin reactive diluent is present in the composition.

36. The composition of claim 31, wherein a mono-functional epoxy resin reactive diluent is present in the composition.

37. The composition of claim 32, wherein a mono-functional epoxy resin reactive diluent is present in the composition and the core shell polymer includes butadiene rubber.

38. The composition of claim 1, wherein the toughener includes a polyether sulfone in an amount of 0.1 to 20 wt %.

39. The composition of claim 1, wherein the composition includes a physical blowing agent present to 5% by weight and the composition is expandable to at least 50% greater than its unfoamed volume and less than 400% of its unfoamed volume.

40. The composition of claim 29, wherein the composition includes a physical blowing agent present to 5% by weight and the composition is expandable to at least 50% greater than its unfoamed volume and less than 400% of its unfoamed volume.

41. The composition of claim 35, wherein the composition includes a physical blowing agent present to 5% by weight, the composition is expandable to at least 50% greater than its unfoamed volume and less than 400% of its unfoamed volume.

42. The composition of claim 1, wherein the composition includes a flame retardant.

43. The composition of claim 38, wherein the composition includes a flame retardant.

44. A curable thermosetting epoxy resin based adhesive composition, which is formulated to adhesively bond with oily surfaces, and which comprises: i) a liquid epoxy resin; ii) a core shell polymer including butadiene rubber in an amount of 5 to 30 wt. % of the composition; iii) a thermally activated curing agent in an amount of 0.001 to 7 wt. % of the composition; iv) a toughener that includes an ingredient selected from an elastomer/epoxy resin adduct, a polyether sulfone, or a combination thereof; v) a filler including graphite; wherein the adhesive composition is in the form of an extrudate having: (a) an uncured thickness between 0.2 and 3.0 mm, (b) a density of from 1.1 to 1.5 g/ml, or both (a) and (b); and wherein the adhesive composition is storage stable at room temperature.

45. The composition of claim 44, wherein the toughener includes a polyether sulfone, and the hardener includes a substituted urea.

46. A curable thermosetting epoxy resin based adhesive composition, comprising: i) a liquid resin epoxy; ii) a thermoplastic selected from a phenoxy resin in an amount of 15 to 40 wt % of the composition or a sulfone polymer in an amount of 0.1 to 50 wt. % of the composition; iii) a core shell polymer including butadiene rubber, the core shell polymer being present in an amount of 5 to 30 wt. % of the composition; iv) a substituted urea curing agent in an amount of 0.001 to 7 wt. % of the composition; v) a filler including fumed silica and graphite; vi) a physical blowing agent that is present to 5% by weight; and vii) a liquid epoxy resin; wherein the adhesive composition is storage stable at room temperature and it is expandable to at least 50% greater than its unfoamed volume and less than 400% of its unfoamed volume; and wherein the adhesive composition is storage stable at room temperature.

47. The composition of claim 46, wherein the adhesive composition is in the form of an extrudate having: (i) an uncured thickness between 0.2 and 3.0 mm, (ii) a density of from 1.1 to 1.5 g/ml, or both (i) and (ii).

Description

[0134] The invention is illustrated by reference to the following examples.

EXAMPLE 1

[0135] An adhesive film was prepared by blending the following materials.

TABLE-US-00004 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 5.00% bisphenol F based epoxy resin

[0136] The formulation was extruded from a twin-screw then calendared to make a film as illustrated in FIG. 1 hereto.

[0137] The temperatures in the different extruder zones were:

TABLE-US-00005 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

[0138] The temperature of the calendar cylinder is between 80 and 90? C.

[0139] The calendared film had a thickness between 0.3 and 2 mm.

[0140] The adhesive film was used to bond two steel plates. The curing conditions was heating at 165? C. for 20 minutes.

[0141] Lap shear strength: 30 MPa/Cohesive failure

EXAMPLE 2

Tape Manufacturing

[0142] 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.

[0143] The liquid resin used for the tacky coat can be [0144] a Bisphenol-A based epoxy resin or [0145] a Bisphenol-F based epoxy resin

[0146] The liquid resin can also be: [0147] the same than then liquid resin used in the formula of the Adhesive film. [0148] Different from the liquid resin used in the formula of the Adhesive film.

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.

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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.