Composition for a structural adhesive

Abstract

The present invention relates to a polymerization-initiating agent for acrylic adhesives containing an epoxidized silane.

Claims

1. A polymerization-catalyzing agent comprising between 5 and 40% by weight of a free radical polymerization initiating agent and between 1 and 30% by weight of an epoxidized silane, wherein the polymerization-catalyzing agent is capable of initiating polymerization of a resin comprising monomers upon mixture with the resin.

2. The catalyzing agent as claimed in claim 1, characterized in that it does not comprise a plasticizing agent or in that it comprises at most 20% (by weight) of plasticizing agent.

3. The catalyzing agent as claimed in claim 1, characterized in that the free radical polymerization initiating agent is a peroxide.

4. The catalyzing agent as claimed in claim 3, characterized in that said peroxide is benzoyl peroxide.

5. The catalyzing agent as claimed in claim 1, characterized in that it comprises between 10 and 20% by weight of polymerization initiating agent.

6. The catalyzing agent as claimed in claim 1, characterized in that it additionally comprises an epoxide resin.

7. The catalyzing agent as claimed in claim 1, characterized in that it additionally comprises inorganic fillers.

8. A method for initiating the polymerization of a (meth)acrylic resin comprising mixing the catalyzing agent of claim 1 with a (meth)acrylic resin.

9. The method of claim 8, wherein said catalyzing agent is mixed with said resin in a ratio of 1:1 to 1:30 (by volume) with respect to said resin.

10. The method of claim 9, wherein said catalyzing agent is mixed with said resin in a ratio of 1:10 (one part of catalyzing agent per 10 parts of resin).

11. The method of claim 8, wherein said resin additionally comprises at least one other element chosen from an elastomeric block copolymer comprising styrene and isoprene, an elastomeric block copolymer comprising styrene and butadiene or ethylene, an elastomer, an acrylate ester monomer in which the alcohol part exhibits at least one linear chain of at least 6 carbon atoms, a polymerization accelerator, a rheological agent, an adhesion promoter, an acid monomer, particles formed of a thermoplastic shell and of an elastomeric core (acrylonitrile/butadiene/styrene, methacrylate/butadiene/styrene, methacrylate/acrylonitrile/butadiene/styrene or methacrylate/acrylonitrile particles and the mixtures of these).

12. A method for promoting the adhesion of parts to a composite material comprising adhering a part to a composite material with the catalyzing agent of claim 1.

13. A two-component structural adhesive comprising a) a resin comprising monomers, which polymerize upon addition of a polymerization-catalyzing agent; and b) a polymerization-catalyzing agent, wherein said polymerization-catalyzing agent comprises between 5 and 40% by weight of a free radical polymerization initiating agent and between 1 and 30% by weight of an epoxidized silane.

14. The two-component structural adhesive of claim 13, wherein said polymerization-catalyzing agent additionally comprises an epoxide resin.

15. The two-component structural adhesive of claim 13, wherein said polymerization-catalyzing agent comprises between 10 and 20% by weight of polymerization initiating agent.

16. The two-component structural adhesive of claim 13, wherein said polymerization-catalyzing agent does not comprise a plasticizing agent or comprises at most 20% (by weight) of plasticizing agent.

17. The two-component structural adhesive of claim 13, wherein said resin is a (meth)acrylic resin.

18. The two-component structural adhesive of claim 13, wherein said resin additionally comprises at least one other element selected from the group consisting of an elastomeric block copolymer comprising styrene and isoprene, an elastomeric block copolymer comprising styrene and butadiene or ethylene, an elastomer, an acrylate ester monomer in which the alcohol part exhibits at least one linear chain of at least 6 carbon atoms, a polymerization accelerator, a rheological agent, an adhesion promoter, an acid monomer, and particles formed of a thermoplastic shell and of an elastomeric core (acrylonitrile/butadiene/styrene, methacrylate/butadiene/styrene, methacrylate/acrylonitrile/butadiene/styrene or methacrylate/acrylonitrile particles and the mixtures of these).

19. A cartridge comprising a compartment containing a polymerizable resin and another compartment containing polymerization-catalyzing agent comprising between 5 and 40% by weight of a free radical polymerization initiating agent and between 1 and 30% by weight of an epoxidized silane.

20. The cartridge of claim 19, wherein said resin is a (meth)acrylic resin, which optionally comprises at least one other element selected from the group consisting of an elastomeric block copolymer comprising styrene and isoprene, an elastomeric block copolymer comprising styrene and butadiene or ethylene, an elastomer, an acrylate ester monomer in which the alcohol part exhibits at least one linear chain of at least 6 carbon atoms, a polymerization accelerator, a rheological agent, an adhesion promoter, an acid monomer, and particles formed of a thermoplastic shell and of an elastomeric core (acrylonitrile/butadiene/styrene, methacrylate/butadiene/styrene, methacrylate/acrylonitrile/butadiene/styrene or methacrylate/acrylonitrile particles and the mixtures of these).

21. The catalyzing agent of claim 1, which contains between 5 and 20% by weight of epoxidized silane.

22. The two-component structural adhesive of claim 13, wherein the monomers are (meth)acrylate monomers.

23. The two-component structural adhesive of claim 13, wherein the resin comprises an acid monomer.

24. The two-component structural adhesive of claim 23, wherein the acid monomer present in the resin is selected from the group consisting of maleic acid, crotonic acid, isophthalic acid, fumaric acid, and methacrylic acid.

25. The two-component structural adhesive of claim 13, wherein the resin comprises an adhesion promoter, wherein the adhesion promoter is a methacrylated phosphate ester.

26. The two-component structural adhesive of claim 25, wherein the adhesion promoter is 2-hydroxyethyl methacrylate phosphate ester.

Description

EXAMPLE

(1) The tensile shear strength (SS) is measured according to a protocol deriving from standard. ISO 4587. In brief, test specimens of composite with dimensions of 100251.6 mm (lwt) are used. Two test specimens are adhesively bonded to one another, the area of overlap being 2512 mm (300 mm.sup.2), with a thickness of the adhesive seal of approximately 200 to 400 m. The force necessary to break the adhesion by pulling on the two test specimens is subsequently measured. Tearing of the contact surface of one of the two test specimens is looked for.

(2) The elongation at break is observed according to a method described in particular by standard ISO 527, the drawing rate of the adhesive being constant and of 50 mm/min.

(3) Two compositions comprising the free radical polymerization initiators are prepared.

(4) Composition I:

(5) TABLE-US-00001 Epon 828 (liquid epoxide resin) 22% Plasticizing agent (diisobutyl 12% phthalate) Titanium oxide 23% Millennium Chemicals Defoamer (Byk 088) 1% Silica (Cab-O-Sil M5), thickening 2% agent 50% Benzoyl peroxide as paste 40%
Composition II:

(6) TABLE-US-00002 Epon 828 (liquid epoxide resin) 20% Epoxidized silane (Coatosil 1770) 5% Titanium oxide 20% Defoamer (Byk 088) 1% Silica (inert and Cab-O-Sil M5) 14% 50% Benzoyl peroxide as paste 40%

(7) The benzoyl peroxide as paste used comprises approximately 50% of benzoyl peroxide, approximately 25% of plasticizing agent and approximately 25% of fillers, stabilizers and rheological agents.

(8) The two compositions thus comprise approximately 20% of peroxide.

(9) Composition I comprises approximately 22% of plasticizing agent, whereas composition II comprises only 10% of plasticizing agent (originating from the peroxide source).

(10) The plasticizing agent has been replaced, in composition II, by inert fillers (silica) and by epoxidized silane.

(11) These polymerization initiating agents are used with the resin:

(12) TABLE-US-00003 Methyl methacrylate AtoFinaElf 42.3% SIS copolymer D1160, Kraton Polymers 16% SIBS copolymer MD6455, Kraton Polymers 5% Elastomer VTB, Hans Chemie 7.5% Acrylate ester monomer 2EHA, AtoFinaElf 4% Acrylate ester monomer HEMA, Cray Valley 4% Adhesion promoter Genorad 40, Rahn 2% Acid monomer MAA, AtoFinaElf 4% Polymerization DMPT, PTE, Pergan 1% accelerator Elastomeric particles C303H, Arkema 10.7% Rheological agent Disparlon 6500, 2.5% Kusumoto Chemicals Other fillers 1.1%

(13) The resin and the polymerization initiating agent (composition I or composition II) are mixed in the ratio 10:1 (by volume), i.e. 10 parts of resin per one part of peroxide-based agent.

(14) The shear strength SS and the elongation at break of the resin are measured.

(15) The RTM test specimens are prepared by sanding with grain 80 and cleaning with isopropyl alcohol.

(16) TABLE-US-00004 Composition I + Composition II + Resin Resin SS 100% adhesive 100% failure of the failure of the substrate of the adhesive bonding adhesive bonding surface at 1.1 MPa surface at 3.4 MPa Elongation at break 137.3% 130.3%

(17) A better shear strength is thus observed when the catalytic composition comprises an epoxidized silane, while maintaining the elongation properties of the adhesive.