GB2196012A

GB2196012A - Acrylic adhesive composition

Info

Publication number: GB2196012A
Application number: GB08721195A
Authority: GB
Inventors: Stephen J Harris; Maureen G Macmanus
Original assignee: Henkel Loctite Ireland Ltd
Current assignee: Henkel Loctite Ireland Ltd
Priority date: 1986-09-11
Filing date: 1987-09-09
Publication date: 1988-04-20
Also published as: GB8721195D0

Abstract

An acrylic monomer adhesive composition, which is activatable by contact with a free radical initiator comprising a metal salt which has limited solubility in the composition, includes a halogenated organic compound selected from halogenated hydrocarbyl, hydrocarbylaryl and aryl compounds, either saturated or unsaturated, and substituted derivatives thereof. Cure-through-volume performance is markedly improved by the halogenated organic compound. A process for free radical polymerisation of acrylic monomeric material comprises bringing together (a) an organic medium comprising the acrylic monomer, (b) the metal salt initiator, and (c) the halogenated organic compound. o

Description

SPECIFICATION Surface-activated acrylic adhesive compositions and a process for the polymerisation thereof This invention relates to the free radical polymerisation of acrylic monomer adhesive compositions using a metal salt as the free radical initiator. The term "acrylic monomer" as used herein includes methacrylic monomers and mixed monomer compositions in which one of the monomers is an acrylic monomer.

It is known to use metal salts as surface activators for anaerobic adhesive compositions.

However the preferred metal salts, particularly copper salts, have limited solubility in an acrylic monomer medium. When such surface-activated compositions are used to join two surfaces with a gap between them, it is found that the gap filling ability or CTV (cure through volume) is unsatisfactory because the interior portions of the composition, spaced from the surfaces, do not cure sufficiently.

The present invention provides an acrylic monomer adhesive composition adapted for activation by a metal salt initiator, wherein the composition includes a halogenated organic compound selected from halogenated hydrocarbyl, hydrocarbylaryl and aryl compounds, either saturated or unsaturated, and substituted derivatives thereof.

The invention also provides a process for the free radical polymerisation of acrylic monomeric material which comprises bringing together a) an organic medium comprising the acrylic monomer b) a free radical initiator comprising a metal salt having limited solubility in the organic medium c) a halogenated organic compound as defined above.

The halogen atom(s) may be chlorine, bromine, fluorine or iodine, which may be the same or different when more than one halogen atom is present in the molecule.

The substituted derivatives may suitably be hydrocarbyl, hydrocarbylaryl or aryl compounds substituted and/or interrupted by one or more heteroatoms, preferably oxygen.

Hydrocarbyl is preferably alkyl or alkylene having 1-10 carbon atoms, more particularly 1-5 carbon atoms.

The halogenated organic compound may suitably be present in an amount of 1-10%, preferably 3-7%, by weight of the composition.

Particularly preferred halogenated organic compounds are substituted derivatives having copolymerisable functionality, especially halogenated alkyl acrylates which are halogenated on the alkyl portion.

In our co-pending application No 87 00467 having the same priority date herewith, we have described the use of a halogenated acrylate or methacrylate jointly with a calixarene derivative as defined in that specification for improving CTV (cure through volume) in an acrylic/methacrylic monomer adhesive composition which is surface-activated by a copper salt. In this application we do not seek to protect the use of such a combination and we make no claim thereto.

The acrylic monomeric material may be one or more of the acrylic and methacrylic monomers which are well known in the art. It may suitably be an acrylate or methacrylate ester of a monohydric, dihydric, trihydric or polyhydric alcohol. It may include as a modifier or auxiliary polymerisable agent an epoxy or urethane system, or a prepolymer of a low molecular weight urethane or polyester capped with acrylate groups. It may also be an oligomer of an acrylate monomer.

Organic solvents which are known in the art may be used as the organic medium. The metal salt initiator may be a transition metal salt such as a copper salt or cobalt salt.

It is believed that the halogenated organic compound assists in solubilising the metal salt in the acrylic monomer composition and facilitates its diffusion through the volume of the adhesive.

The invention is illustrated in the following Example, in which results are indicated for 4 series of tests. Results can be compared within each series of tests, which were conducted simultaneously, but should not be compared between one series and another, due to different conditions arising from the grit-blasting preparation of lapshears and the time elapsing between the preparation of the lapshears and the carrying out of the tests.

EXAMPLE To an adhesive formulation based on 16.9% by weight hydroxypropyl methacrylate, 6.1% acrylic acid, 47.1% monomer B (a urethane acrylate prepared by reacting two moles of toluene diisocyanate with one mole of hydrogenated bisphenol A, diluting the reaction mixture with methyl methacrylate and further reacting it with two moles of hydroxyethyl methacrylate in manner disclosed in Example V of US Patent No. 3,425,988), 23.6% monomer A (a urethaneacrylate reaction product of toluene diisocyanate and the hydroxy polyoxypropylene derivative of trimethylol propane (commercially available under the trade mark PLURACOL T P 2450) having unreacted isocyanate functionality capped with hydroxyethyl methacrylate), 1% saccharin, 1% acetylphenyl hydrazine and 1.9% cumene hydroperoxide was added with stirring varying quantities of the halogenated organic compounds indicated below. Resulting compositions were then tested on grit blasted mild steel lapshears primed on both sides with brushed-on copper salt activator (which is commercially available from Loctite (Ireland) Limited, Dublin, under the name ''Activator N") at the gaps indicated below and cured for 24 hours at room temperature.CTV (cure through volume) performance was improved markedly without adversely affecting zero gap bond strengths.

Grit Blasted Mild Steel Lapshears; 24 Hour Test; Room Temperature; Double Sided Activation Additive 820 Strength Tensile Shear A with Adhesive Stability daNcm O mm Gap 0.4 mm Gap O > 2 hrs 214 11 5% CH2C12 > 2 hrs 215 23 (dichloromethane) 5% ClCH2CH2Cl > 2 hrs 175 25 (1 ,2-dichloroethane) 5% 1,2,4-trichloro- > 2 hrs 194 18 benzene O > 2 hrs 140 15 1% CH2C12 > 2 hrs 178 19 1% C1CH2CH2C1 > 2 hrs 165 18 1% 1,2,4-trichloro- > 2 hrs 189 21 benzene O > 2 hrs - 24 10% CH2C12 > 2 hrs - 78 O > 2 hrs 140 15 1% 2,2,3,3-tetrafluoro- > 2 hrs 179 13 propyl methacrylate (Rohm) 5% 2,2,3,3,-tetrafluoro- > 2 hrs 150 31 propyl methacrylate

Claims

1. An acrylic monomer adhesive composition adapted for activation by a metal salt initiator, wherein the composition includes a halogenated organic compound selected from halogenated hydrocarbyl, hydrocarbylaryl and aryl compounds, either saturated or unsaturated, and substituted derivatives thereof.

2. A composition according to claim 1, wherein the halogen atom(s) is/are chlorine, bromine, fluorine or iodine, which may be the same or different when more than one halogen atom is present in the molecule.

3. A composition according to claim 1 or 2, wherein the substituted derivative is hydrocarbyl, hydrocarbylaryl or aryl compounds substituted and/or interrupted by one or more hetero atoms.

4. A composition according to claim 3, wherein the hetero atom is oxygen.

5. A composition according to any of the preceding claims, wherein hydrocarbyl is alkyl or alkylene having 1-10 carbon atoms.

6. A composition according to claim 5, wherein hydrocarbyl is alkyl or-alkylene having 1-5 carbon atoms.

7. A composition according to any of the preceding claims, wherein the halogenated organic compound is present in an amount of 1-10% by weight of the composition.

8. A composition according to claim 7, wherein the halogenated organic compound is present in an amount of 3-7% by weight of the composition.

9. A composition according according to any of the preceding claims, wherein the halogenated organic compound is a halogenated alkyl acrylate which is halogenated on the alkyl portion.

10. A composition according to any of the preceding claims, substantially as described herein by way of Example.

11. A process for the free radical polymerisation of acrylic monomeric material which comprises bringing together a) an organic medium comprising the acrylic monomer b) a free radical initiator comprising a metal salt having limited solubility in the organic medium, and c) a halogenated organic compound as defined in any of claims 1-6 or 9.