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WO1989011921A1 - Procede et appareil d'enduction d'une feuille moulable - Google Patents

Procede et appareil d'enduction d'une feuille moulable Download PDF

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Publication number
WO1989011921A1
WO1989011921A1 PCT/GB1989/000623 GB8900623W WO8911921A1 WO 1989011921 A1 WO1989011921 A1 WO 1989011921A1 GB 8900623 W GB8900623 W GB 8900623W WO 8911921 A1 WO8911921 A1 WO 8911921A1
Authority
WO
WIPO (PCT)
Prior art keywords
coating
sheet
chamber
curtain
moulding
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1989/000623
Other languages
English (en)
Inventor
Michael Frederick Underwood
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CAMBRIAN STRONGHOLD Ltd
Original Assignee
CAMBRIAN STRONGHOLD Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by CAMBRIAN STRONGHOLD Ltd filed Critical CAMBRIAN STRONGHOLD Ltd
Publication of WO1989011921A1 publication Critical patent/WO1989011921A1/fr
Priority to GB9026223A priority Critical patent/GB2244940A/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
    • B05C5/005—Curtain coaters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
    • B05C5/002—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work the work consisting of separate articles
    • B05C5/004—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work the work consisting of separate articles the work consisting of separate rectangular flat articles, e.g. flat sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/30—Processes for applying liquids or other fluent materials performed by gravity only, i.e. flow coating
    • B05D1/305—Curtain coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/02—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to macromolecular substances, e.g. rubber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
    • B29C51/14—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor using multilayered preforms or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2033/00—Use of polymers of unsaturated acids or derivatives thereof as moulding material
    • B29K2033/04—Polymers of esters
    • B29K2033/12—Polymers of methacrylic acid esters, e.g. PMMA, i.e. polymethylmethacrylate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/769—Sanitary equipment
    • B29L2031/7692—Baths

Definitions

  • This invention relates to a process and apparatus for coating a mouldable thermoplastics sheet for colouring or decoration thereof. It also provides a mouldable product made from a sheet as aforesaid.
  • Polymethylmethacrylate (PMMA or acrylic) coatings for application to plastics materials exhibit normal thermoplastic characteristics of acrylic or . modified acrylic resins and in film form can be softened and moulded within certain limitations.
  • the characteristics exhibited by a particular acrylic paint depend upon the formulation of the particular methacrylate present, e.g. its co- monomers, molecular weight, free acid content, impurity content etc.
  • the solubility of the resultant resin in organic solvents By selection of an appropriate formulation the solubility of the resultant resin in organic solvents, its ability to be suspended as a colloid, its dried film toughness and its performance under different temperature regimes may be affected.
  • By selection of an appropriate combination of resin and solvent mixture the drying characteristics of the paint and its ability to hold pigment loadings can be varied, as well as its capacity to adhere to various substrates and its physical handling characteristics.
  • Pre-pigmented sheet for thermo-forming is available in cast or extruded opaque. translucent and surface textured grades of acrylic, polystyrene, ABS , PVC and polycarbonate sheet, and an extensive colour range is available from the sheet manufacturers.
  • the fact that the sheet is pre-pigmented by " the manufacturer means that the user is limited to the colour ranges provided by the manuf cturer. For a wide colour range to be available, the individual colours are called for less frequently, and as the range extends larger and larger stocks have to be held by manufacturer, user or a stockholder. For these reasons the cost of pre-pigmented sheet is signifi'cantly above that of clear sheet.
  • pre-pigmented sheet In products formed from pre- pigmented sheet all secondary decoration has to be applied to the revealed surface. It is difficult to introduce new colours quickly in response to changing customer demand or to make small production runs of a particular colour because of the inflexibility of the stockholding chain to demand. Production of special colours not only takes time but also requires significant minimum batch quantities.
  • Semi-mouldable coating materials are known, but their use has been restricted to shallow mouldings for distantly viewed products such as signs or other products where minor imperfections are not significant.
  • the invention provides a method of decorating an intended unrevealed face of a plastics sheet before moulding thereof, which comprises applying to the sheet a coloured or pigmented layer that is highly stretchable under moulding conditions for the sheet.
  • the coating material is formed into a liquid film or sheet which is deposited on the substrate.
  • the coating is applied to the sheet as a liquid film or curtain that comprises a high molecular weight resin in a volatile solvent mixture.
  • the coating may be pigmented with Ti ⁇ 2 or a mixture of Ti ⁇ 2 and china clay.
  • the liquid film is fed from the coating head onto the sheet through a chamber that surrounds the liquid film, the interior of the chamber becoming saturated or nearly saturated with solvent mixture.
  • the volatile solvents used preferably have boiling points below about 80 C and the solvent mixture used is selected to have more volatile and less volatile components such that it can dry finger hard in a few minutes at ambient or slightly elevated temperatures but retains a degree of fluidity until it is completely dry so that there is not premature skinning-over of an under-layer containing entrapped solvent which could be detrimental to subsequent moulding.
  • the sheet may be screen printed before it is coated, and a feature of the method is that fine detail may be printed in the sheet before the overall coating is applied and that detailed printing is compatible with the subsequent coating and is not damaged by the solvent or other materials present during the overall coating step.
  • a method of decorating an intended unrevealed face of a plastics sheet before moulding thereof with a printed pattern and a background colour which comprises;
  • a layer to form a background colour by forming a solution of a high molecular weight resin in a volatile solvent mixture into a liquid film or curtain and depositing the liquid film or curtain over the printed face of the sheet, the resin being highly stretchable during subsequent moulding and the pattern printed onto the sheet and the film deposited over the sheet containing the same or substantially the same resin or mixture of resins.
  • the sheet on which the resin is printed or deposited contains active sites, it is advantageous if the resin coated onto the sheet can chemically link to the material of the sheet at those sites either after coating or ' during a subsequent thermoforming process to increase the coating adhesion and delamination resistance during repeated hot and cold cycling such as may be required e.g. of sanitaryware during its service life.
  • Acrylic sheet of SW grade suitable for use in sanitaryware is crosslinked by the sheet manufacturers to increase its toughness and mechanical resistance and has sites available for formation of chemical bonds to the coating material.
  • the invention also provides a method of forming a shaped article which comprises coating an intended unrevealed face of a plastics sheet before moulding thereof with a coloured or pigmented layer that is highly stretchable under moulding conditions for the sheet, the coating being applied to the sheet as a liquid film or curtain containing a high molecular weight resin in an organic solvent, drying the coating and moulding the article.
  • the unrevealed face of the moulded article may then be further treated e.g. by being cleaned with an organic solvent and/or reinforced with a plastics reinforcing material, and the deposited coating should be sufficiently resistant to withstand such further treatments .
  • the method described above is intended for the production of lar-ge quantities of the decorated clear sheets in small batches. and it is important to the economics of such a method that there should be the minimum of waste of coating material on change from one colour to another and that the cleaning operations required during colour change-over should be capable of being carried out rapidly.
  • the invention provides apparatus for the curtain coating of articles comprising a coating head having chamber and a slit leading from the .chamber for discharge of a curtain of liquid coating material, wherein at least the inner surface of the chamber is of a plastics material that readily releases the coating liquid, means within the chamber being movable to expel the paint and mechanically clean the chamber when use of the coating liquid is to be discontinued.
  • the chamber may be provided with a pair of pistons towards each end that are movable to define the width of the curtain. and means may be provided for sweeping at least one of the pistons along the chamber for cleaning thereof .
  • the invention provides apparatus for curtain coating an article including means that defines a chamber below the curtain head, through which chamber the curtain flows from the head to the substrate .
  • an inlet and a discharge conveyer to the coating station • share a common drive and have to be physically connected along their lateral edges for drive transfer from one conveyer to another.
  • the coating head is cantilevered over the gap between the belt conveyers, which requires an unnecessarily robust and heavy construction.
  • apparatus for the coating of substrates comprising a station for coating the substrates with a descending sheet of liquid coatine: material, a feed conveyer for feeding the substrates to the coating station, and a discharge conveyer for conveying the substrates from the station, the station fitting between physically disconnected inlet and discharge conveyers and having a coating head supported at both ends.
  • Figure 1 is a diagram showing successive stages in a process for coating and subsequent moulding of a plastics bath coloured on its non-revealed surface;
  • Figure 2 is a view in central longitudinal section of a coating station for use in the process of Figure 1;
  • Figure 3 is a diagrammatic side or curtain face elevation of the coating station of Figure 2;
  • Figure 4 is a diagrammatic lateral section through an end part of a coating head forming part of the station of Figures 2 and 3;
  • Figure 5 is a diagrammatic cross-section of the coating head
  • Figure 6 is a diagrammatic side elevation of the coating station positioned between a pair of conveyer tables.
  • Figure 7 is a plan of a typical coating station and associated equipment including a drying tunnel, showing material movement.
  • the invention is " concerned with the coating of ,the non-revealed face of articles of transparent sheet for subsequent moulding into shaped articles by thermo—"forming. By colouring the unrevealed face of the product there is obtained a product having a brilliant glazed lustre, reducing its 'plastic' quality.
  • some or all of the following criteria may be significant:
  • (f) deep draw mouldings are used. i.e. mouldings in which the depth exceeds 25% of their shortest dimension and may be up to 100-125% of the shortest dimension.
  • the resin system should be tough and desirably has a surface hardness similar to that of the hardest likely substrates. It should be a good adhesive and desirably should adhere to most clear thermoplastics materials that are available for thermoforming including acrylic, polystyrene, ABS , PVC polycarbonate cellulose acetate and cellulose butyrate sheets. It is desirably pigmentable and should be capable of being highly charged with pigment without destroying its physical or chemical properties so that a film of e.g.20-25 u dry thickness will be sufficiently opaque. It should also be plastic at the time of moulding and should be demouldable.
  • a coating 75 u thick may become reduced in thickness to about 25 u during moulding at about 200 C and should not deteriorate or become uneven in appearance as a result of this process.
  • the temperature response profile of the coating material and if possible other factors such as its hygroscopic character should be as close as possible to those of acrylic sheet which is the most important substrate.
  • the coating should also be benign to the substrate and in particular should not give rise to significant crazing, embrittlement or other weakening or damage.
  • a clear acrylic sheet 10 to be moulded in this instance into a bath is received from the manufacturer covered with protective films which are removed at la.
  • the sheet may be printed with decorative designs e.g. by screen printing using the same high molecular weight resin in solvent as is employed in the subsequent background coating step.
  • the pattern applied should be designed with the shape changes that occur in moulding borne in mind.
  • the sheet 10 is coated, after any printing stage, with a coating liquid before it is moulded.
  • the coating produced on the sheet needs to be fully mouldable in the sense that a flat sheet coated with a pigmented dry film can be stretched and shaped typically with an increase of up to ninefold in its surface area by threefold linear extension on two orthogonal axes without:
  • the coating produced should exhibit adequate resistance to organic solvents so that the moulded products can be cleaned before reinforcement or other post-moulding operations.
  • the coating liquid to be applied to the sheet 10 may contain a high molecular weight resin dissolved in a mixture of volatile solvents, the coating forming b ' y drying without significant increase of molecular weight by polymerisation during the drying process.
  • the best commercially available material at present known to the applicants is a polymethyl methacrylate resin dissolved in an organic solvent system.
  • the sheet 10 is passed through a coating station 21 having a coating head 12 from which a curtain of pigmented or non-pigmented fluid film 14 is applied to a face of the sheet 10 to form a layer 16 thereon at lb.
  • the layer 16 is dried at lc by blow drying under mild conditions, conveniently at or slightly above ambient temperatures e.g. at 20-24 C, to form a dry coated sheet on which the coating 16 has the capacity to stretch during subsequent moulding and has physical properties that match those of the sheet 10.
  • mild drying conditions assists in preventing premature skinning which accentuates damage to the coating from bubbles in the film arising from static charges on the sheet being coated and also gives rise to damage from trapped solvents.
  • the coated and dried sheet is inverted at Id and placed in a mould.
  • mouldeding is carried out at le to form a bath 20; the moulding of other deeply dished or shaped articles is similar.
  • moulding by vacuum forming it may be desirable to "blow" the softened sheet to obtain an even material distribution before drawing down, thus avoiding under-side wrinkling in the region of sharp corners that could appear as creases in the colour.
  • moulded products that can be made according to the invention include furniture, domestic equipment, building materials for internal or external use, panels for display signs and motor or motor accessory panels. It is anticipated that sheets up to 2m wide can be processed at rates between 30 and 60 linear meters per minute.
  • the resin used should be of relatively high molecular weight and should be a pure hom ⁇ polymer, which maximises its compatibility with cellcast acrylic resins.
  • the melting point of the coating resin is desirably no lower than that of the substrate sheet and is desirably the same.
  • sanitaryware grade acrylics which are cross-linked it is desirable to use a grade of coating resin that has free acid groups that can cross-link with the substrate sheet and improve the bond of the coated film, the cross-links .
  • the resin found to be most useful is a PMMA homopolymer of molecular weight about 80000, melting point about 210 C and acid number 7. It is a chemically and temperature resistant resin of satisfactory hardness. Higher molecular weight grades of PMMA are available, but these may be lower melting or have other disadvantages. Less preferred materials which may have some utility include methacrylate copolymers e.g. with styrene or a vinyl compound, or butyl acrylate polymers or copolymers. For screen printing prior to coating (see above), a slightly softer grade may be employed, and the ketone content of the initial solvent mix may be partly or wholly replaced my methyl ethyl glycol or cyclohexanone.
  • the resin employed may initially be in the form of beads and is first contacted with a solvent mixture that is sufficiently aggressive to take the resin into solution but is nevertheless rapidly and completely volatile. There is a need for both a clear resin base mixture for translucent colours and for the darker colours and for a white resin base mixture for white or light-coloured articles e.g. baths and sanitaryware.
  • a suitable formulation for the solution is :
  • the MEK and toluene are mixed with a dispersant which for Ti ⁇ 2 can be 50% by weight of a silicone modified polycarboxylic acid derivative and 50% of a carrier such as di-( 2-ethylhexyl)-phthalate.
  • the dispersant with its carrier is present in an amount of 0.3% by weight of the total mixture (including pigment in the case of a white base) and in these quantities the di-( 2-ethylhexyl ) - phthalate does not significantly plasticise the resin.
  • the resin beads or granules are dispersed in the MEK, toluene and carrier mixture system and mixed at 35-40 C for 8-10 hours (or less if greater temperatures are used) .
  • the higher boiling solvents can be added when the resin has gone into a bead free solution on visual inspection (which should provide a reading of about 4 on the Hegman scale) .
  • the higher boiling isobutanol and EGA are also volatile materials but have a greater persistence than the MEK and toluene which if used on their own could lead to premature skinning which would resist further volatilisation of solvent .
  • a clear resin base may be coloured with temperature stable and high light resistance organic dyestuffs.
  • a white resin base may be pigmented with Ti ⁇ alone but it is preferably pigmented with a mixture of Ti ⁇ £ and china clay. It has been found that the more glossy the surface of the film the less the tendency for granulation and that for pigments above 12u (7 on the Hegman scale) granulation is certain to occur at full stretch of the applied film during subsequent moulding. Accordingly the pigments may be sized to a nominal size of 2u and preferably not above 5u. As a further anti-granulation precaution the moulding temperatures used are not above 190 C and in the case of acrylics about 165-175 C.
  • Pigment may be mixed with the above clear base in at 24% w/w pigment and 76% clear base (pigment : binder ratio 1:1) .
  • the high P:B ratio and the finely ground state of the pigments gives films of useful opacity in the particular resins selected.
  • the pigments are added before the high boil solvents, and as the latter are mixed in the mixture is tested for viscosity and if necessary adjusted to a Brookfield viscometer viscosity of 200 poise. If the viscosity is above this value, low boiling solvent has been lost and MEK is added to bring it to the required value. If a non-white pigment is required, oorrggaanniicc ccoolloouurraannttss ssttaabbllee up to at least 240 C and of high light-fastness are added.
  • the viscous base material described above has to be thinned (e.g. for gravity flow to a viscosity of about 100- 90 seconds at 18 C in a Ford No 4 cup and for pressure flow to a somewhat greater viscosity) by addition of a rapidly evaporable thinner.
  • a rapidly evaporable thinner that may be needed to be added to the base material so that it can form a fluid film or curtain by gravity flow is:
  • the thinner may be:
  • Figures 2-6 show diagrammatically a coating station 21 for use in the above process that fits between an inlet conveyer 22 whose top face defines an on-table for the station 21 and a discharge conveyer 24 whose top face defines an off-table for the station 21.
  • the conveyers 22. 24 are formed as individual units that are separate both from one another and from the structure of station 21 itself. and are independently driven. However, motors and timing units of the conveyers 22.24 are arranged to provide for smooth passage of the sheets 10 through the station 21.
  • a gap is provided between the conveyers 22,24, above which is disposed the coating head 12 and below which is disposed a fluid receiving and reservoir tank.
  • the coating head 12 is supported at each end on a pair of support members 25 rather than being cantilevered as in previous curtain coater designs.
  • a coating fluid top tank 29 is defined by a pair of abutting hollow e.g. semi-cylindrical half-shells 28 closed at their ends by end closures 48 including plates 60 that fit fluid- tightly to the ends of the half-shells 28.
  • the material of the half-shells 28 is preferably a plastics that is not easily wettable by the coating material e.g. a high molecular weight polyethylene or polypropylene.
  • a downwardly convergent channel 27 loads frcra the cavity 29 to a liquid discharge slit 32 from which the curtain of coating liquid issues .
  • the presently preferred coating liquid comprises a high molecular weight resin dissolved in a volatile mixture of solvents, and it is desirable to minimise solvent loss that the curtain of coating liquid should be confined for a major portion of its length in a closed chamber in which the atmosphere can become saturated or near saturated with solvent vapours.
  • transverse walls 34 and end plates 36 of clear glass depend from the coating head 12.
  • Vertically adjustable glass covers 36 at the lower ends of the walls 34 allow a range of different thicknesses of sheet 10 to be coated.
  • a receiving and reservoir tank 38 extending across the gap between conveyers 22,24 from one end to the other thereof and having a sloping floor 41 is disposed below the coating head 12, and when a sheet 10 is absent catches the falling curtain 14 of coating material.
  • the tank 38 is of a plastics material that is difficultly wettable by the coating liquid (e.g. high molecular weight polyethylene or polypropylene) and is supported on a frame 40 carried on an underframe 39 by scissor jacks 43 that allow the height and levelness of the tank 38 to be adjusted.
  • the underframe 38 has castors 35 permitting the whole coating station 21 to be wheeled out of position between conveyers 22,24 and replaced by a stand-by coating station 21a (Fig. 7) .
  • the tank 38 has an outlet 42 leading to a pump unit 44 from which coating liquid flows to a delivery tube 45 that leads through choke valve 46 and inlet end fitting 47 to the cavity 29 of the coating head.
  • Coating liquid that is not discharged through slit 32 flows through outlet end fitting 48 to return tube 50 having overpressure relief valve 52.
  • Tubes 45 and 50 are also of a plastics material that is difficultly wettable by the coating liquid.
  • the tube 50 leads via filler cap 54 and inlet 56 to the tank 41.
  • valves 46,52 By appropriate selection of the rate of pump 44 and the settings of valves 46,52 it is possible either to permit the coating liquid to flow from the cavity 29 by gravity alone or to cause it to flow under positive pressure and to adjust the pressure of the coating liquid within cavity 29 to bring about a rate of flow through slit 32 that will maintain the curtain 14 and give rise to a desired thickness of the dried coating 16, that thickness also depending on the speed of the sheet 10 through the curtain.
  • a T-tube 62 has one limb passing through the plate 60 - an opposite limb 66 closed by an end cap 67, and a central limb 64 that forms part of the tube 45 or 50.
  • An annular piston 70 of relatively soft material not easily coatable with the coating liquid e.g. of softer polyethylene or PTFE
  • the piston 70 also fits into the convergent channel leading to the discharge slit 32.
  • the inner end face of each piston 70 is flat.
  • the piston 70 and a steady disc 72 are carried by a support tube 68 that is a sliding fit in the T-tube 62.
  • the positions of the pistons 70 along the cavity 29 are adjustable to set the width of the curtain 14. and edge steady wires 71 depend from the pistons 70 through the slit 32 to position the edges of the curtain and maintain the curtain width against its tendency to narrow as it falls.
  • the tube 68 may be formed in sections that may be connected together e.g. by threaded ends so that the piston 70 may be moved close to the centre of the cavity 29 when only relatively narrow sheets are being coated.
  • a further function of the pistons 70 is to provide a means for mechanically cleaning the interior of the chamber 29 to enable unused coating liquid to be recovered, and in many instances to allow immediate use of the coating liquid of the next succeeding colour, the residual coating liquid being so small in proportion to the volume of the liquid in chamber 29 as to have a negligibly small effect on the colour produced by the coating liquid of the next succeeding colour on the sheets.
  • a threaded or otherwise formed outer end structure on the tube 68 also allows attachment of a cleaning rod 74 shown in phantom in Fig 4.
  • the end cap 67 can be removed and the rod 74 attached to the tube 68 at each side of the head 12, after which the pistons 70 are pushed inwardly until their end faces abut, sweeping a great part of the residual coating liquid out of the cavity 29.
  • only one of the pistons 70 could be caused to sweep the whole working length of the cavity 29.
  • the above curtain coater or liquid contact coating machine has the advantage that it can provide very fast turnaround on a coating liquid colour change since it is quick to clean, flush and recharge.
  • the tank 38 may also be mechanically cleaned between coating liquids by passing a cleaning piston along it in the same way as for the cavity 29.
  • the pipes 45,50 can be emptied and washed, or if the members 48 are modified to be of X-profile " with an additional top limb closed by a removable cap, the pipes 45,50 could be simply rodded through. To avoid having to wash out the pump unit 44, it could be of the peristaltic kind.
  • the curtain coater can be operated with only a few litres (e.g.
  • the chamber 29 can be dismantled easily and any residual coating material allowed to dry and peeled from the inner surfaces of half shells 28 from which it is readily released.
  • the machine is of simple and relatively inexpensive construction and has an almost totally enclosed coating head 12,34,36 that can be connected to a fume extraction duct of required.
  • the rate of gas extraction from around the curtain 14 should be relatively low to avoid disturbance of the curtain and loss of solvent. Because the running viscosities of the coating liquid are generally constant through low solvent evaporation and because the coating machine is intended for a single task (e.g. coating sheets to be formed into baths) it is possible to use a head 12 having a fixed.
  • pairs of shells 28 can be provided having a range of gap -widths, and can be exchanged quickly as required.
  • the curtain may form largely by gravity flow from the cavity 29 which in that case may be incompletely filled, or it may be formed by pressure flow. In the latter case, the height of the head 12 above the sheet 10 or other workpiece may be as little as about 30-50 mm and the width of the slit 32 may be relatively narrow. Pressure coating enables coating liquids of significantly higher viscosity to be used, which reduces diluent use and drying times.
  • sheet material moves from the on-table defined by conveyer 22 to the off-table defined by conveyer 24 and thence to a wheeled loading rack 75 on which it may be transported to a drying tunnel 79 working at 20-24 °C having a fan 81 for drying air and an extractor fan 83 , so that the coated sheet is dried under relatively mild temperature conditions in a flow of air.
  • the coatings applied may be used to effect a lamination of two clear or one clear and one obscured sheet.
  • this lamination procedure one face of each sheet is coated as described above and after the coatings have dried the coated sides of the sheets are offered together and the two sheets are formed in an oven or on forming equipment . As they reach forming temperatures of about 180 C the sheets adhere together through their coatings, assisted (in the case of a forming machine) by the pressure of the forming.- The appearance presented to the user is a similar to that of a single sheet.
  • this form of the invention provides a relatively thick sheet which has the coloured layer closer to the visible surface of the sheet, gives additional protection to the coloured layer from mechanical damage, and an opportunity to resist colour leach with less " pigment applied .
  • the coating may be applied by the process described to act as a barrier coat on styrene mouldings so that they may be reinforced with resins possessing solvents and characteristics that would otherwise destroy the moulding.
  • a coated mouldable sheet made according to the invention may be employed as a decorative veneer to a principal moulding material that provides structural integrity.
  • the present coated mouldable sheet material is then used as a form of mould transfer coating, the sheet that is coated being very thin ( ⁇ lmm) and mounted on a carrier board until used.
  • the veneer sheet of polymethylmethacrylate or other clear acrylic polymer can be coated as aforesaid and is vacuum formed into a mould for use in replacement of the conventional sprayed powdered coating as a mould lining with easy mould release properties.
  • the coated sheet may have a single overall colour or it may have printed patterns a d a background overcoated colour.
  • the temperature response and shrinkage profil.es of the thin coated sheet is such that it can be used to provide a decorative surface to foamed or solid thermoplastic formings with which it forms an excellent bond at moulding temperatures and also with polyurethane high or low density foams. It can also be used with foamed polyesters.
  • the thin coated sheet can be used with an intermediate adhesive layer for mouldings using reinforced polyester thermosetting dough moulding compositions and sheet moulding compositions which normally have set/cure o " temperatures of 120-160 C, and the resultant products can be used at working temperatures typically of up to 75 C.
  • the resultant moulded articles based on an acrylic sheet coated on its non-revealed face which is adhered to the principal moulding material have high gloss , are surf ce repairable, colour fast, tough and resistant to age whitening.
  • PVC or polystyrene veneer sheets can be coated in the same way, but are less preferred because they are softer and more prone to damage and whitening.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Mechanical Engineering (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Coating Apparatus (AREA)

Abstract

Le procédé décrit sert ß décorer une face non découverte désirée d'une feuille de plastique avant son moulage. Ledit procédé consiste à appliquer sur la feuille une couche colorée ou pigmentée ayant une étirabilité élevée dans les conditions de moulage de la feuille. La couche est appliquée sur la feuille sous la forme d'un film liquide ou d'un rideau d'une résine à poids moléculaire élevé dans un mélange de solvants volatils et est éventuellement pigmentée avec du TiO2 ou avec un mélange de TiO2 et d'argile blanche, la granulométrie moyenne du pigment étant égale à environ 2 microns. Le matériau d'enduction peut être amené par pression ou par gravité depuis la tête d'enduction sur la feuille à travers une chambre qui entoure le film liquide, l'intérieur de la chambre étant destiné à être saturé ou quasi-saturé par le mélange de solvants. La présente invention décrit également un appareil servant à enduire d'un rideau des articles, ledit appareil comprenant une tête d'enduction pourvue d'une chambre et une fente s'étendant depuis la chambre et servant à déverser un rideau de matériau d'enduction liquide, appareil dans lequel au moins la surface interne de la chambre est en matériau plastique permettant une libération rapide du liquide d'enduction.
PCT/GB1989/000623 1988-06-03 1989-06-05 Procede et appareil d'enduction d'une feuille moulable Ceased WO1989011921A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9026223A GB2244940A (en) 1988-06-03 1990-12-03 Process and apparatus for coating a mouldable sheet

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB888813077A GB8813077D0 (en) 1988-06-03 1988-06-03 Coating of plastics sheets
GB8813077.8 1988-06-03

Publications (1)

Publication Number Publication Date
WO1989011921A1 true WO1989011921A1 (fr) 1989-12-14

Family

ID=10637964

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1989/000623 Ceased WO1989011921A1 (fr) 1988-06-03 1989-06-05 Procede et appareil d'enduction d'une feuille moulable

Country Status (4)

Country Link
EP (1) EP0442886A1 (fr)
AU (1) AU3736589A (fr)
GB (2) GB8813077D0 (fr)
WO (1) WO1989011921A1 (fr)

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2721809A (en) * 1952-09-10 1955-10-25 Alvin M Marks Method for the uniform coating of large surfaces
GB1225438A (fr) * 1968-09-17 1971-03-17
US3584120A (en) * 1969-05-27 1971-06-08 Eastman Kodak Co Method for projecting a bubble-free coating film or curtain
FR2259695A1 (fr) * 1974-02-01 1975-08-29 Systemes Ab
GB1472150A (en) * 1975-04-26 1977-05-04 Topla Kk Marble-patterned bathtub basin or sink
EP0000446A1 (fr) * 1977-07-13 1979-01-24 Linfordware Ltd. Procédé de fabrication de feuilles laminées, décoratives
DE3026793A1 (de) * 1980-07-15 1982-02-25 Iwata Air Compressor Manufacturing Co. Ltd., Tokyo Beschichtungsverfahren in einer fliessbeschichtungseinrichtung
DE8628473U1 (de) * 1986-10-23 1986-12-11 Dimter GmbH Maschinenfabrik, 89257 Illertissen Vorrichtung zur Leimangabe an zu verleimende Holzflächen

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2721809A (en) * 1952-09-10 1955-10-25 Alvin M Marks Method for the uniform coating of large surfaces
GB1225438A (fr) * 1968-09-17 1971-03-17
US3584120A (en) * 1969-05-27 1971-06-08 Eastman Kodak Co Method for projecting a bubble-free coating film or curtain
FR2259695A1 (fr) * 1974-02-01 1975-08-29 Systemes Ab
GB1472150A (en) * 1975-04-26 1977-05-04 Topla Kk Marble-patterned bathtub basin or sink
EP0000446A1 (fr) * 1977-07-13 1979-01-24 Linfordware Ltd. Procédé de fabrication de feuilles laminées, décoratives
DE3026793A1 (de) * 1980-07-15 1982-02-25 Iwata Air Compressor Manufacturing Co. Ltd., Tokyo Beschichtungsverfahren in einer fliessbeschichtungseinrichtung
DE8628473U1 (de) * 1986-10-23 1986-12-11 Dimter GmbH Maschinenfabrik, 89257 Illertissen Vorrichtung zur Leimangabe an zu verleimende Holzflächen

Also Published As

Publication number Publication date
AU3736589A (en) 1990-01-05
GB9026223D0 (en) 1991-09-11
GB2244940A (en) 1991-12-18
GB8813077D0 (en) 1988-07-06
EP0442886A1 (fr) 1991-08-28

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