Patent Application
20070277462
This invention relates to a composite board and a method of making the board.
Composite boards have numerous applications in industry and allow for the variation of the characteristics of any component such as a panel made there from.
This invention aims to provide an alternative composite board and a method of manufacture thereof.
The invention provides a composite board which includes a moulded front wall, a sheet insert which is attached to the front wall, a frame element which is attached to the front wall and the insert and an adhesive which acts between the front wall, the insert and the frame element.
The front wall may be made from a mouldable composition which may include a first resin and a catalyst. The first resin may be a thermosetting resin and the mouldable composition may include a filler and an additive selected from any one or combination of an anti-foaming agent, a surfactant, an accelerator and pigment.
Alternatively the mouldable composition may include a hydraulic binder and reinforcing.
The insert may be made from an expanded or foamed material which may include any one of polystyrene, polyurethane and phenolic foams.
In an alternative form of the invention the insert is made from an open-celled polymeric foam which may be impregnated with a hydraulic binder.
The frame element may be made from any appropriate material such as wood.
The adhesive may include a second resin and a catalyst. The second resin may be a thermosetting resin.
The adhesive may include a filler and an anti-foaming agent.
The board may include a reinforcing member which is submerged in the adhesive.
The insert may be covered with a sealant which may be in the form of a thermoplastics polymer.
The board may include a backing sheet which covers the insert and the frame element or the board may include a connecting layer which is applied to the insert and the frame element with which a second composite board is secured to the insert and the frame element.
The invention also provides a method of manufacturing a composite board of the aforementioned kind which includes the steps of:
The mould surface may be made from silicone rubber.
The method may include the steps of submerging a reinforcing member in the adhesive, covering the sheet with a sealant and attaching a backing sheet over the insert and the frame element.
Alternatively the method may include the steps of applying a connecting layer to the insert and the frame element and securing a second composite board to the insert and the frame element by way of the connecting layer.
The invention is further described by way of examples with reference to the accompanying drawings in which:
FIGS. 2 to 4 are partial, cross sectional and schematic representations of a composite board manufactured according to the method of FIGS. 1 and a composite panel made there from.
The board 10 can be used in any appropriate application such as for example a cabinet door.
In a first step shown in
In a first example of the invention the composition 32 comprises a first thermosetting resin and a catalyst for the resin. The resin is preferably a liquid polyester resin such as the unsaturated isophthalic or orthophthalic liquid polyester resins. Examples of these are those manufactured by Scott Bader of England including Crystic™ 272 catalysed by catalyst powder B and Crystic™ 196 and those under the Atlac™ brand by DSM.
Other suitable polyester resins are those produced by National Chemical Products, Germiston, South Africa, such as Polylite™ 33410, Polylite™ 8130, Polylite™ 8000 and Polylite™ 8382X. Suitable latent catalysts for these resins include di-tert-butyl peroxy 3,3,5-trimethylcyclohexane in dibutyl phthalate such as those sold by Akzo Chemie under the name Triganox™ 29B240, Lucidol™ KL50, Triganox™ 21, Triganox™ C or Triganox™ K-70, benzoyl peroxide formulations, t-butylperbenzoate sold by Interox under codes TBTB and TBPB, dibenzoyl peroxide sold by Interox under code MIKP NAI or t-Butyl 2-perethyl haxanoate. These catalysts generally trigger polymerisation at a temperature in the region of 60° C. upwards, more typically 80° C. upwards.
Suitable room temperature catalysts for these resins which have been accelerated with accelerators such as cobalt octoates or naphthenates or tertiary amines, are organic peroxides such as methylethyl ketone peroxide, cyclohexanone peroxide and similar.
The composition 32 includes 50 to 350% by weight and preferably about 300% by weight of the resin of an inorganic particulate filler. The filler is included for sizing, as a heat sink, for cohesive strength and for liquid phase flow. The preferred filler is barium sulphate at a specific gravity of approximately 4,8 and a particle size of approximately 300 mesh. Barium sulphate is particularly used to promote flow, to settle into the mould surface picking up every detail, to add cohesive strength to the composition and to minimise shrinkage. Calcium carbonate (10 micron particle size) is added in certain applications to balance the barium sulphate.
Other possible fillers include calcium carbonate, talc, hollow glass balloons, kaolin, silica or mica, all in the particle size spectrum range of from 65 to 300 mesh.
Depending on requirements the composition 32 includes additives such as an anti-foam agent, for example Byk 057 or Byk 066 for unsaturated polyesters, or Byk 085 for phenol formaldehyde resole resins, a surfactant such as Disperbyk 163 or Tween 20 which is a polyoxethylene 20 sorbitan monolaurate by ICI, for either polyester or phenolic resins and appropriate pigment such as titanium dioxide and yellow oxide.
These agents are added to ensure that the composition flows easily across the mould surface, wetting it intimately, that all entrained bubbles are freely and easily released so that the front layer is seamless, without bubbles and of consistent thickness without pull away, fish eyes or similar defects and to obtain appropriate colouring of the wall 12.
An example of the ingredients of the first composition 32 which is for a board 10 to simulating wood, is as follows:
The composition 32 is allowed to polymerise to form the wall 12. For example, the mould 30 is passed under an inductive heat source such as infra red lamps in order to polymerise the thermosetting resin before the next part of the composite board 10 is added.
Alternatively to the first composition 32 a second composition 32 can be used which has a hydraulic binder slurry reinforced with a choice of either a thermoplastic polymer or a water dispersible, miscible or soluble thermosetting resin which is allowed to polymerise or to set to form the wall 12.
The binder slurry is reinforced with a thermoplastic polymer in water chosen from an acrylate, a methacrylate, a vinyl, a polyvinyl alcohol or a polyvinyl acetate for the purpose of easily wetting of the reinforcing layer 20 and to promote the adhesion and cohesion of the binder slurry to the reinforcing layer 20. Alternatively water soluble, miscible or dispersible thermosets chosen from oligo isocyanates, unsaturated polyesters or phenol formaldehyde resoles can reinforce the binder slurry, either on their own or in combination with the thermoplastic polymers above with which, in the case of the oligo isocyanites in particular, a cross link can occur.
When a binder slurry is used in the second composition 32 and a polystyrene core is used as the insert 22 the core does not require to be sealed against solvent attack.
In
The second thermosetting resin can be the same as the first thermosetting resin of the wall 12 to promote cross-linking.
The adhesive 18 is used to adhere the wall 12 to the reinforcing layer 20, the insert 22 and the frame 24.
A further quantity of the adhesive 18 is applied over the reinforcing layer 20 so that the reinforcing layer 20 is submerged in the adhesive 18.
The insert 22 and the frame 24 are located on the reinforcing layer 20 and the adhesive 18, as is shown in
The insert 22 is a shaped expanded polystyrene foam core 36 sealed with an acrylic resin sealant 38.
The core 36 is of a density between 24 and 40 kg/m3 and is either formed by injection moulding or by post cutting with a hot wire to exactly the edge profile required to minimise consumption of the adhesive 18 and to ensure that a rear surface 40 presented to the back has no indentations, voids or gaps after sanding.
The sealant 38 is preferably a thermoplastic polymer in water chosen from acrylates, methacylates, vinyls, or polyvinyl alcohols or any combinations or co-polymers between them or a phenol formaldehyde resole resin with a catalyst therefore. Suitable examples are E330 Acrylic Polymer by Rohm & Haas or Polyvinyl Alcohol 5 to 10% solution in water or Mowiol™ 18/88 by Clariant or resin code 1028 with catalyst Phencat™ 10 by Schenectady Corporation to coat the core 36. The sealant 38 can be applied by brush or by spray and preferably does not contain any filler or extender.
Alternatively the solvent resistant sealant 38 is a solution of Gelatin in water applied at a temperature exceeding 30° C. and more preferably 45° C. The sealant 38 can contain Glycerol at a proportion of up to 60% of the dry mass of Gelatin, and preferably in the range of 35% to 50% in order to impose toughness to the sealant film after drying.
The surface of the core 36 is dried and the acrylic coalesces forms an unbroken film which is resistant to the attack of solvents such as the styrene monomer in unsaturated polyester resins which would penetrate the core 36 without the unbroken acrylic film and dissolve the polystyrene of the core 26, making it unsuitable for the application.
The core 36, first sealed by the sealant 36 in water or alcohol medium can after drying, be further over sealed by a further sealant in the solvent medium which is allowed to set or to dry before the sealed core 36 is placed into the adhesive 18 before it has set and there by ensuring an unbroken inter layer of the adhesive 18 between the wall 12 and the insert 22 and without entrapped bubbles of air.
The insert 22 connects the wall 12 to the backing sheet 26. The insert 22 gives excellent thermal insulation, minimizes weight and is cost effective and tough. Less preferred alternates to polystyrene foam are rigid polyurethane or phenolic foams.
When resistance to fire is important for the board 10 the insert 22 is made of a flexible open cell polymeric foam such as a polyurethane foam which has been impregnated with an hydraulic binder slurry chosen from gypsum, which is the alpha or the beta hemihydrate of calcium sulphate, or alternatively a Portland cement or a blend between the two. The gypsum or Portland cement is allowed to set and dry to form a rigid core 36 resistant to fire in the dry density range 200 to 500 kg/m3. The open cell polyurethane foam is in the density range 6 to 12 kg/m3 and with a cell size in the range 0.5 to 6 mm in diameter. The foam is impregnated and the insert 22 is made in a known manner.
The frame 24 is in the form of an elongate wooden member which is machined to the profile of the mould 30. The frame 24 can be made from any wood substitutes which can accommodate mechanical fixings such as hinges, handles, bolts and jointly mechanisms such as screws and which can impart strength and stability to the board 10.
Once the adhesive 18 has set the rear surface 40 is sanded if required and the backing sheet 26 is laminated over the insert 22 and the frame 24 with an appropriate thermosetting resin and catalyst to form the board 10 shown in
In
The connecting layer 50 is solvent free or is in water or alcohol or alternatively with a hot melt or in the form of a contact adhesive which does not contain solvents.
The construction of the panel 52 ensures dimensional stability as each board 10B, 10C form half of the panel 52 and balances the tensions in the other. It also assists in the accurate control of thickness.
The advantages of the board 10 or the panel 52 of the invention are that they have high strength to weight ratios, are lightweight, provide surfaces that simulate natural material such as wood, stucco, stone or rendering, have good thermal insulation properties, can be made to conform to any profile, are easy to incorporate into another structure by mechanical methods, are seamless, waterproof, resistance to wear or weather and cost effective.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003/6900 | Mar 2004 | ZA | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/ZA05/00045 | 3/4/2005 | WO | 8/3/2007 |
