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
  • B05C1/00—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating
  • B05C1/04—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length
  • B05C1/08—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line
  • B05C1/0813—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line characterised by means for supplying liquid or other fluent material to the roller
• • 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
  • B05C1/00—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating
  • B05C1/04—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length
  • B05C1/08—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line
  • B05C1/0826—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line the work being a web or sheets
  • B05C1/083—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line the work being a web or sheets being passed between the coating roller and one or more backing rollers
• • 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
  • B05C1/00—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating
  • B05C1/04—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length
  • B05C1/08—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line
  • B05C1/0826—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line the work being a web or sheets
  • B05C1/0834—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line the work being a web or sheets the coating roller co-operating with other rollers, e.g. dosing, transfer rollers

Definitions

• This invention relates to a substrate coating. More particularly, the invention relates to a paperboard coating for food packaging. The invention also relates to an apparatus and method of applying the coating to a substrate.
• a barrier in the form of a separate layer of material must be applied to the paperboard to ensure that the paperboard itself remains dry as far as possible and therefore retains its mechanical strength.
• the barrier also ensures that the liquid does not seep through the packaging.
• the barrier should, additionally, be relatively impermeable to air in order to substantially prevent meat contained within the packaging from becoming discoloured, be insoluble when in contact with a wide range of solvents, be colour free, have substantially no odour, a high coefficient of friction and have hot-seal properties.
• a plastics film layer is extruded or glued onto paperboard to make water or greaseproof packaging and can be used to package a wide range of foodstuffs including liquids.
• the extrusion process offers the fastest of the two coating methods and is the cheapest option for large production volumes, but requires high capital expenditure. The method is only viable if the process is to be carried out continuously. The gluing process has a lower capital outlay, but can only be carried out at lower speed and is therefore not cost effective for large production volumes.
• the specific weight of the film that is applied is generally in the region of 20g/m 2 .
• the film used is non-biodegradable, and is difficult to recycle because once the film has been adhered to the paperboard, it is problematic to separate the two again.
• US 5 776 619 to Shanton discloses a paperboard layer for use in forming rigid food containers.
• the layer comprises a base coat comprising a styrene acrylic polymer latex and pigment that is applied directly to the paperboard, and a top coat comprising a styrene acrylic polymer latex and pigment that is applied to the base coat.
• the layer seeks to improve grease, oil and cut resistance and enhance printing qualities.
• the present invention seeks to meet the above criteria and overcome or at least mitigate the problems of the prior art.
• One aspect of the invention provides an apparatus for applying a coating to a substrate comprising a first cylinder onto which a liquid emulsion of the coating is introduced, a scraper for removing excess coating from the first cylinder and a second cylinder in contact with the first cylinder and arranged so as to transfer the coating from the first cylinder to the substrate, wherein the scraper comprises two mutually opposed scraper blades and a coating reservoir.
• pressure may be applied to the substrate so as to compress the substrate by approximately 0.1 mm at working speeds.
• the apparatus may be flexographic apparatus.
• the second cylinder is resilient.
• the second cylinder may be manufactured from EPDM or a photopolymeric flexographic sheet.
• the first cylinder maybe a honeycomb ceramic cylinder.
• a second aspect of the invention provides a method of applying a coating to a substrate comprising the steps of: i) applying a liquid emulsion of the coating to a first cylinder of a coating apparatus from a coating reservoir. ii) Removing excess coating from the first cylinder using a scraper blade associated with the coating reservoir, iii) Transferring the coating to a second cylinder in contact with the first, iv) Transferring the coating to a substrate in contact with the second cylinder.
• a third aspect of the invention provides an acrylic coating for application to a substrate comprising resin and a dispersant, the coating being substantially water resistant, grease resistant and having low migration characteristics.
• the coating may be an oil in water emulsion. More preferably, it may comprise epoxide PE wax approved for use by the DGCCRF for direct food contact in the European Union. Even more preferably, the epoxide PE wax may be included at a concentration of between 0.01 and 5%. Preferably, the epoxide PE wax maybe included in a concentration of 5%.
• the coating may be a water based solution so as to be absorbed, partially by the substrate.
• the coating may be approved by the DGCCRF. According to another optional feature of the third aspect of the invention the coating may be substantially colour free.
• the coating may be substantially odour free.
• the coating be used in heat sealing processes.
• the surface tension modifier may lower the surface to less than 36 dynes/cm.
• the surface tension may be 36 to 40 dynes/cm.
• FIGURE 1 is a schematic side view of the apparatus for applying the coating to paperboard illustrating the reservoir
• FIGURE 2 is a side elevation of the scraper and scraper blades
• FIGURE 3 is a perspective view of one end of the scraper.
• FIGURE 4 is a view of the scraper illustrating the inlet and outlet pipes for the liquid coating.
• the DGCCRF in turn complies with EU directives 82/711, 93-8, 90-128, 92-39, 85-572 and the modifications to the 82/711 by 97/48/CE implemented on 29 July 1997. Furthermore, all compounds comprising the coating are on current EU non-toxic "positive lists", specifically resolution AP96/5 "Surface coatings intended to come into contact with foodstuffs" of the European Council and adopted by the Council of Ministers on 2 October 1996.
• a voluntary final stage of the procedure is the specific migration test in which specific monomers and catalysts used in the coating are subjected to a migration test using a gas chromatograph. This test was developed to test migration into meat particularly.
• the formulation process has resulted in an acrylic coating formulation, one example of which is an oil in water emulsion.
• the emulsion comprises a liquid disperse phase and a continuous liquid phase.
• the liquid disperse phase comprises epoxide PE wax in a 5% concentration to provide the grease barrier properties.
• the formulation further comprises a wax dispersant, and preferably a surface tension modifier to aid the transfer of the coating from the cylinders and onto the paper by lowering the surface tension to less than 36-40 dynes/cm (the surface tension of the board) and an antifoaming agent.
• the formulation has a surface tension of 32 dynes/cm.
• a second example dispenses with the epoxide PE wax to form an entirely water based solution of the coating without the PE wax.
• a further advantage of the coating is that it is an oxygen barrier to increase the shelf life of the foodstuff held by the package.
• the coating is substantially non-adhesive and colour free, is insoluble over a wide range of different simulating solvents, has a low odour and is non-delaminating but does have some relative adhesion for foodstuffs such as turkey.
• This may be achieved by the addition of a blocking agent to the formulation.
• Some relative adhesion is advantageous as this permits cartons made from the coated paperboard and containing foodstuffs to be placed on shelving angled toward purchasers of the foodstuffs whilst maintaining the foodstuffs in a desired position within the carton. This in turn enhances the presentation and marketability of the foodstuffs.
• the coating is also advantageously heat sealable.
• a coating to coating seal can be achieved at a temperature of 150°C and a pressure 2 bars for 2 seconds.
• a temperature of 160°C and a pressure of 3 bars should be maintained for 5 seconds. The fact that any attempt to tear board coated using the above coating results in the delamination of the board indicates that a good seal is achieved.
• the coating is absorbed partially by the substrate, for example the coated board.
• FIG. 1 there is shown apparatus 10 for applying a coating to a substrate such as paperboard 20 using a flexography process.
• a liquid emulsion or solution of the coating is applied to the surface of an anilox cylinder 12.
• a ceramic honeycomb cylinder permits an accurate proportion of the coating to be transferred to the blanket cylinder 16.
• the honeycombs are preferably 35 microns in depth, with there being 90 cells/linear cm giving an effective capacity of 11-14 cm 3 /m 2 .
• 6g/m 2 is transferred in one pass (40% of the theoretical volume) with a 60° engraving angle.
• This type of anilox cylinder 12 is used as this enables an increased amount of the coating to be carried by the cylinder.
• a scraper 14 removes any excess coating before the coating is transferred from the anilox cylinder 12 to the blanket cylinder 16.
• the cylinder 16 is advantageously made of resilient material such as butyl, EPDM (ethylene propylene diene methylene), nitrile or silicone rubber.
• EPDM ethylene propylene diene methylene
• nitrile or silicone rubber.
• EPDM or a Cyrel R TM type photopolymeric flexographic sheet having a hardness of approximately 50-80° shore is used.
• the scraper 14 comprises upper and lower scraper blades 28 and 30 mounted on a coating reservoir portion 32.
• the scraper 14 is, in this embodiment, adjustably mounted in relation to the anilox cylinder 12 by a pair of locating holes 40a and 40b that engage corresponding fingers (not shown) provided on a frame that supports the cylinders.
• Adjustment means for adjusting the position of the scraper in relation to the cylinder 12 is provided.
• a pair of pressure adjusting screws 36a and 36b is provided .
• the method of applying pressure is automated as part of an overall control system for the apparatus (not shown).
• suitable sealing means for example resilient seals 34a and 34b, formed from rubber or similar materials, are proved at each end of the reservoir 32 to prevent, or at least substantially minimise coating leakage.
• FIG 4 shows a rear view of the scraper 14, the infeed apertures 38a and 38b and outfeed aperture 42 for the liquid coating can be seen.
• pipes (not shown) feed the liquid coating into the reservoir 32 at each end thereof preferably from a peristaltic pump. Any excess coating then exits the reservoir at the centre through outfeed aperture 42 and is recycled.
• a closed or open loop coating supply system may be employed. It is preferred that a closed system is used as this substantially prevents contact between the coating and the atmosphere.
• anilox cylinder 12 is arranged to be in contact with blanket cylinder 16, the rotation thereof transferring the coating from the anilox cylinder 12 to the blanket cylinder 16.
• the thickness of the coating is adjusted by changing the velocity of one of the anilox cylinder or blanket cylinder relative the other.
• a controller is used to control the rotational velocities of each cylinder.
• the linear velocity of the anilox cylinder 12 is preferably 1.05 to 1.10 times greater than the linear velocity of the blanket cylinder 16. This enables a thick layer of coating to be more evenly applied to the paperboard 20.
• Paperboard either in the form of a continuous sheet or in discrete pieces 20 as shown, is fed into the apparatus by a first conveyor belt 22 running at the same linear velocity as the blanket cylinder 16.
• a force is applied by the apparatus to the anilox cylinder 12, in a direction X, the load being transferred via the blanket cylinder 16 such that the paperboard 20 is typically compressed by approximately 0.05 - 0.1 millimetres at normal running speeds and the coating is transferred to the paperboard 20 and in greater amounts than would be possible using an off-set process.
• the above described arrangement ensures that an even layer of the liquid emulsion is applied to the paperboard 20.
• An impression roller 18 is provided underneath the paperboard 20 so as to guide the paperboard past the blanket cylinder. Where it is necessary to blank areas of paperboard from printing, portions of the blanchet cylinder 16 may be recessed so as not to pick up the coating from the anilox cylinder 12.
• the coated paperboard is then preferably transferred by a second conveyor 24 to a heater 26 in direction Y.
• a particularly preferable heating system comprises a hot air flow at a temperature of approximately 180°C used in addition to infrared radiation for at least two seconds. It is preferable that the temperature should reach at least 85°C on the support conveyor 24.
• four 6kW infrared lamps (not shown) are used that emit radiation in a spectrum of 500 nm to 2000 nm wavelength to give a good coating surface whilst avoiding "orange skin” effects.
• a long drying station may be used to avoid off-setting as this provides sufficient time for the coating to dry before the paperboard 20 is stacked or rolled up.
• the coating is partially absorbed into the paperboard, with any remainder forming a layer on the surface thereof.
• the degree of absorption depends upon, amongst other factors, the characteristics of the paperboard and the interval between applying the coating and the paperboard entering the heater 26.
• a second coating is advantageously applied to the paperboard by a similar apparatus as described above.
• a thicker coating for example 9g/m 2 can be obtained.
• the second layer has different properties from the first, and the two layers have complementary properties so as to achieve the desired result.
• the first layer may include a pigment.
• the coating must comprise less than 5% of the board weight. Therefore, for a standard 300 g/m 2 board, the coating weight must be lower than 15 g/m 2 . Furthermore, in order for the finished board to be considered recyclable it is necessary for the coating weight to be less than 10 g/m 2 .
• the preferred total coating weight applied by the above apparatus is in the range of 6-7 g/m 2 dry.
• a single pass with a longer drying time may be sufficient.
• the chances of achieving a coating weight of 6-7 g/m 2 in a single pass are enhanced if the ceramic "honeycomb" anilox cylinder 12 is used.
• the coating is in the range of 3 to lOg/m 2 and comprises one or more coatings, which formed a pinhole free continuous coating resistant to water.
• the above described apparatus is generally capable of coating 130-150 metres of paperboard per minute by the abovementioned continuous application process. Following coating, the paperboard is cut, creased and glued as necessary. If aseptic packaging is required, the paperboard can then be treated with a hydrogen peroxide solution or other suitable antimicrobial agent.

Landscapes

• Paper (AREA)
• Coating Apparatus (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

Family

ID=9897791

Family Applications (1)

Country Status (6)

Citations (2)

Family Cites Families (7)

• 2000
  • 2000-08-18 GB GB0020279A patent/GB0020279D0/en not_active Ceased
• 2001
  • 2001-08-17 AU AU2001286522A patent/AU2001286522A1/en not_active Abandoned
  • 2001-08-17 DE DE60110916T patent/DE60110916T2/de not_active Expired - Fee Related
  • 2001-08-17 WO PCT/US2001/025751 patent/WO2002016050A2/en active IP Right Grant
  • 2001-08-17 EP EP01965975A patent/EP1311352B1/de not_active Expired - Lifetime
  • 2001-08-17 ES ES01965975T patent/ES2242766T3/es not_active Expired - Lifetime

Patent Citations (2)

Also Published As

Similar Documents

Legal Events