METHOD OF REINFORCING AN ARTICLE

Abstract: A method of spray reinforcing an article using a curable syrup of a poly((meth)acrylate) in a curable (meth)acrylate monomer and an aqueous dispersion of an organic peroxide which is capable of curing the syrup. The syrup and aqueous dispersion are intimately mixed and sprayed as a reactive spray. The reactive spray entraps suitable reinforcing material in flight towards the article to be reinforced. The use of an aqueous dispersion reduces environmental problems associated with solvent-based systems.

Description: Method Of Reinforcing An Article The present invention relates to a method of reinforcing an article. Conventionally, household articles such as sanitary fittings, e.g. baths, shower trays, together with larger articles such as boat hulls have been reinforced with a combination of polyester resin binder and reinforcing material such as glass fibre, inert fillers and the like. Combinations of such polyester resin binders and reinforcing materials are not easily recyclable and, where the article is formed from an acrylic material, the polyester resin binder is often incompatible with the acrylic material to the extent that the reinforcing material can become detached during use. EP-A-0693503 proposes the use of an acrylic resin binder in order to overcome the above two problems. However, the acrylic resin binder disclosed therein is required to be cured using an initiator system in which the active components, dibenzoyl peroxide and dilauryl peroxide, are delivered as a solution in an organic solvent, methyl ethyl ketone. This presents an additional problem in that the solvent, which is volatile, is emitted into the atmosphere as a pollutant. It has now been found that an acrylic resin binder can be successfully cured using an initiator system in which the active component is delivered in the form of an aqueous dispersion thereby providing a more environmentally friendly method of reinforcing articles and which method does not suffer from the above problems. Accordingly, the present invention provides a method of reinforcing an article, particularly an article formed from an acrylic material, which method comprises (A) supplying to a mixing zone (i) a first supply of an aqueous dispersion of an organic peroxide (ii) a second supply of a syrup of a poly((meth)acrylate) in a curable (meth)acrylate monomer which is curable by the organic peroxide (B) mixing the first and second supplies in the mixing zone to form an intimate mixture; (C) spraying the intimate mixture to form a reactive spray (D) entrapping reinforcing material within the reactive spray to form a reinforcing medium (E) directing the reinforcing medium onto a surface of the article to be reinforced to form at least a partial coating; and (F) curing the (meth)acrylate monomer within the coating so as to form a reinforced article. The aqueous dispersion of the peroxide is preferably one of those disclosed in US 4917816 or WO93/17054 both of which are directed towards the preparation of aqueous peroxide dispersions for use in curing polyester resins. The preferred aqueous dispersions therefore contain an organic peroxide, such as benzoyl peroxide, and optionally in addition an inorganic peroxide. The preferred aqueous dispersions contain the peroxide in a finely divided particulate form and can be made to have suitably low viscosities by the inclusion of materials which are stated as producing an ionic region around the peroxide particles. Other additives may be included such as defoamers to reduce the incidence of foaming; acidic inorganic salts to stabilise the dispersion, fire retardants and humecants. Typically, the organic peroxide represents about from 25 to 55% by weight, e.g. 40% by weight, of the dispersion. Commercially available materials include Abcat 40 and Abcure S-40-25 obtainable from ABCO Industries. The viscosity of the aqueous dispersion is controlled such that it is easily sprayable from conventional equipment. Typically, the viscosity of the dispersion is from 100 to 5000 centipoise (1 x 10 ' to 5 Ns.m ). Suitable organic peroxides for use in the present invention include benzoyl peroxide, lauroyl peroxide, d-cumyl peroxide and di-cetyl peroxide. The quantity of organic peroxide used is preferably design so as to provide a cure time for the curable monomer of about thirty minutes or some other period of time at the end of which the coating is able to be self supporting. The poly((meth) acrylate used in the present invention is preferably a homopolymer of methyl methacrylate and the (meth) acrylate monomer is methyl methacrylate. The poly((meth) acrylate) may be formed using conventional polymerisation techniques and then added to the chosen monomer to form the syrup required in the present invention. The molecular weight, Mn, of the polymer may range from 10000 to 20000, although more typically the molecular weight is in the range 10000 to 15000. Alternatively, the polymer may be formed using catalytic char- transfer techniques directly into the monomer such that the resulting polymer has a very low polydispersivity index thereby leading to syrups having relatively high polymer contents. Typically, the syrup contains from 35 to 45 % by weight of polymer with the remainder being monomer. Preferably, the syrup contains from 35 to 40% by weight of polymer. The syrup may also contain other additives such as cross-linking agents (ethylene glycol dimethacrylate), stabilisers, waxes and pigments. Usually, each of such additives is added as a minor component in the range of 0.1 to 3% by weight of the syrup. It is important that the aqueous dispersion and syrup are intimately mixed. Maldistribution of the dispersion can result in a significant variation in the speed of curing of the monomer which leads to localised hot spots, bubbling and poor control of the physical properties of the reinforcement coating. To assist in the control of the speed of curing, it is desirable to include an exotherm peak suppressant such as terpinolene. Usually such exotherm peak suppressants are included directly into the syrup. Typically, such exotherm peak suppressants are used at a level from 200 to 700 ppm by weight based on the syrup, preferably from 300 to 600 ppm by weight based on the syrup. Typically, the ratio of the weight of reinforcing medium to reactive spray is in the range 1 :1 to 0.2:1 , preferably 0.7:1 to 0.4:1 , for example about 0.5:1. The reinforcing medium is preferably glass fibre which is delivered into the reactive spray in a presized form. Additional reinforcing medium, such as alumina trihydrate, calcium carbonate and other inorganic fillers may be incoφorated within the syrup. The process of the present invention may be effected using conventional spray systems as used in conjunction with polyester resins. The aqueous dispersion may be delivered to the mixing zone using a pumped system. The syrup may be similarly delivered. The mixing zone may be a separate, high energy mixing system or may be incorporated within the spray head of the spray system. Where necessary, the spray system may incorporate heating systems to maintain the syrup and aqueous dispersion in appropriate fluid forms. Typically, the syrup is delivered to the mixing zone at a temperature from 25 to 30°C. The present invention is illustrated by reference to the following example. Example 1 In this example, a conventional bath formed from thermoformable acrylic sheet was successfully reinforced using the process of the present invention. Commercially -available Abcat 40 was used as the aqueous dispersion of an cyanic peroxide. A resin formed from a solution of polymethyl methacrylate in methyl methacrylate monomer was used as the syrup. The polymethyl methacrylate represented about 35 to 38% by weight of the syrup. The syrup had a viscosity of 450 cP (4.5 x 10 1 Ns.nr 2 ) at 20 to 23 °C and contained as major additives 550 ppm by weight of terpinolene, 0.25% by weight of a parrafin wax having a melting point in the range 54 to 57°C and 0.2% by weight of dimethyl para toluidene. Chopped glass was used at a ratio of glass to syrup of 0.45:1 by weight The aqueous dispersion, syrup and chopped glass were mixed to form a reinforcing medium as required by the present invention using a Magnum Spray System (MSC-BPO-MS-11). The supply of the aqueous dispersion and syrup were regulated by pressure control. The pressure of the supply of aqueous dispersion was set at 30 psig (308 kN.m 2 ) and that of the syrup at 80 psig (653 kN.πrv 2 ). Within a spray booth held at a temperature of 16°C, three layers of the reinforcing medium were sprayed onto the reverse face of the base of the bath. Additionally, two layers of the reinforcing medium were sprayed on to the reverse sides of the bath. The layers were left to polymerise over a period of about an hour. Thereafter, a further layer of the reinforcing medium was sprayed on to the base and a baseboard positioned over the further layer. A final layer was then sprayed over the baseboard. The layers were then rolled out manually to release entrapped air and to smooth out any outstanding fibres of glass fibre. No distortion was observed of the bath after reinforcement. The reinforced bath was then subjected to the British Standards Institution, BS 4305 Part 1 1989; EN198: 1987 thermal cycling test which was passed.

Claims: Claims 1 A method of reinforcing an article which method comprises (A) supplying to a mixing zone (i) a first supply of an aqueous dispersion of an organic peroxide (n) a second supply of a syrup of a poly((meth)acrylate) in a curable (meth)acrylate monomer which is curable by the organic peroxide (B) mixing the first and second supplies in the mixing zone to form an intimate mixture, (C) spraying the intimate mixture to form a reactive spray (D) entrapping reinforcing material within the reactive spray to form a reinforcing medium (E) directing the reinforcing medium onto a surface of the article to be reinforced to form at least a partial coating, and (F) curing the (meth)acrylate monomer within the coating so as to form a reinforced article 2 A method as claimed in claim 1 wherein the aqueous dispersion of the organic peroxide also contain an inorganic peroxide 3 A method as claimed in either claim 1 or claim 2 wherein the organic peroxide represents from 25 to 55% by weight of the dispersion 4 A method as claimed in any one of the preceding claims wherein the viscosity of the aqueous dispersion is from 100 to 5000 centipoise (1 x 10 ' to 5 Ns m 2 ) 5 A method as claimed in any one of the preceding claims wherein the organic peroxide is at least one selected from the benzoyl peroxide, lauroyl peroxide, d-cumyl peroxide and di-cetyl peroxide 6 A method as claimed in any one of the preceding claims wherein the syrup contains an exot'ierm peak suppressant 7 A method as claimed in claim 6 wherein the exotherm peak suppressant is terpinolene 8 A reinforced article prepared by a method as defined in any one of claims 1 to 7 9 A reinforced article as claimed in claim 8 wherein the arttcile is formed of an acrylic material

Inventors: IRVINE DEREK JOHN, KIRTLEY NEIL, WILFORD-BROWN JACQUIN HILARY, IRVINE, DEREK, JOHN, KIRTLEY, NEIL, WILFORD-BROWN, JACQUIN, HILARY
Applicants: ICI PLC, IRVINE DEREK JOHN, KIRTLEY NEIL, WILFORD BROWN JACQUIN HILARY, IMPERIAL CHEMICAL INDUSTRIES PLC, IRVINE, DEREK, JOHN, KIRTLEY, NEIL, WILFORD-BROWN, JACQUIN, HILARY
Application year: 1997
Main classification: C09D4
IPC codes: B05D1, B29C70, C09D4