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EP-4735221-A2 - A MULTILAYER STRUCTURE, METHOD FOR ITS MANUFACTURE AND USAGE THEREOF

EP4735221A2EP 4735221 A2EP4735221 A2EP 4735221A2EP-4735221-A2

Abstract

The invention relates to a multi-layer structure, a method for manufacturing it and usage of it.

Inventors

  • SANDBERG, LARS

Assignees

  • ALPLA Werke Alwin Lehner GmbH & Co. KG

Dates

Publication Date
20260506
Application Date
20240626

Claims (20)

  1. 1. A multilayer structure with dry press formed material comprising at least one layer with dry press formed material, and on top of said layer a discrete layer to which moisture has been added, which material contains fibers, preferably cellulosic fibers, and on top of said discrete layer, a powder coating comprising a polymeric material, wherein, the moisture has essentially vanished in said discrete layer and wherein the fibers in said material have been bound to each other through the first moisturizing and then the subsequent drying.
  2. 2. A multilayer structure according to claim 1 wherein the moisture is provided by adding one layer with wet fiber material, preferably wet laid material, between said dry formed material and said powder coating, thus providing an air-laid multilayer material.
  3. 3. A multilayer structure according to claim 1 wherein the discrete layer covers all fibers of the surface of said dry press formed layer.
  4. 4. A multilayer structure according to claim 1 wherein the discrete layer is a transition zone that may be sharp or fuzzy.
  5. 5. A multilayer structure according to claim 1 wherein the powder has been melted using heat, and then has been left to solidify, by cooling down, to create a barrier layer on said material.
  6. 6. A multilayer structure according to claim 1 wherein the powder is present on the inside of the structure.
  7. 7. A multilayer structure according to claim 1 wherein the powder coating layer has a thickness of from about 5 pm to about 200 pm, preferably from about 10 pm to about 100 pm.
  8. 8. A multilayer structure according to claim 1 wherein the relationship fiberlength/thickness of powder coating layer is from about 5 to about 600, preferably from about 10 to about
  9. 9. A multilayer structure according to claim 1 wherein the polymeric material, is selected from the group comprising polyolefins or polyethylene therephtalate or mixtures thereof, such as polypropylene or polyethylene or co-polymers thereof.
  10. 10. A multilayer structure according to claim 2 wherein the moisture content in the wet laid material is from about 4 to about 25%, preferably from about 7 to about 15 %.
  11. 11 . A multilayer structure according to claim 1 wherein a strength increasing agent has been added to the dry press formed material, wherein said agent is selected from the group comprising latex, starch or a combination thereof.
  12. 12. A method for manufacturing a multilayer structure according to any one of the preceding claims, comprising the following steps: a) providing a dry-press formed material, preferably comprising fibers, most preferred preceded by a treatment at from about 150 °C to about 250 °C and at a pressure of from about 100 to about 10000 Bar, such as from about 200 to about 2000 Bar, b) providing moisture to said material, c) adding thereon a powder comprising polymeric material to create a coating, preferably at a temperature range of from about 10 °C to about 40 °C, most preferred at ambient temperature, especially preferred at room temperature, and d) subjecting said material formed into a multi-layered intermediate product to high temperature, preferably from about 60 °C to about 220 °C, thus providing a multilayer structure with a coating layer, preferably a three-layer structure.
  13. 13. A method according to claim 12 wherein the moisture is provided in step b) by using any one or a combination of the following: b1) wetting fibers on the top of said material, and optionally drying said fibers, or b2) adding on top of the dry press formed material in layer form, a layer of wet fiber material, and optionally drying said fibers, or b3) adding a wet-laid layer on to the dry press formed material in layer form, or b4) adding a wet-laid layer essentially simultaneously when the dry press formed material is formed.
  14. 14. A method according to claim 12 wherein the high temperature of step d) provides dry forming and that water is dried, preferably in a range of from about 80 °C to about 200 °C, most preferred in a range of from about 100 °C to about 140 °C.
  15. 15. A method according to claim 12 wherein the high temperature of step d) is provided by using an oven.
  16. 16. A method according to claim 12 wherein the structure emanates from ChemiThermoMechanical Pulp, ThermoMechanical pulp, Kraft pulp, sulfate pulp, sulfite pulp, recycled pulp material, board or carton, or a combination thereof.
  17. 17. A method according to claim 12 wherein the structure emanates from bleached or nonbleached pulp, or a combination thereof.
  18. 18. A method according to claim 12 wherein the structure emanates from hardwood or softwood, bagasse, algae or straw or a combination thereof.
  19. 19. A method according to claim 12 wherein in step a) a strength increasing agent is added to the dry press formed material, wherein said agent is selected from the group comprising latex, starch or a combination thereof.
  20. 20. A multilayer structure obtainable by a method according to any one of claims 12 - 19.

Description

A MULTILAYER STRUCTURE, METHOD FOR ITS MANUFACTURE AND USAGE THEREOF Field of the invention The present invention relates to a multilayer structure comprising at least one layer with dry press formed material, wherein moisture has been added, which material preferably contains fibers, most preferred cellulosic fibers, and on top of said material, a powder coating comprising a polymeric material, which has been in melted form which subsequently solidify, wherein, the moisture has essentially vanished when said polymeric material has become solid. It also relates to a method for its manufacturing and usage thereof. In short, a multilayer structure with a dry press formed material, and preferably also wet laid material, and a powder coating (that is melted) is provided. Background Powder coating may be used to achieve barrier coatings. For example, PE (polyethylene) powders could be used to coat a surface and then melted, subsequently solidified, into a continuous barrier layer. In solidified form this PE may then be part of the barrier in liquid carton boards. Powder coatings may be achieved through that particles are charged and through that sent towards a grounded or opposite charged surfaces and through that being organized into a layer. The surface needs to be at least partly conductive in order to facilitate the process. Cellulose fiber surfaces support this coating method under some circumstances. Dry formed fibers may typically be compressed to high density. The technology has one downside that surface located fibers are typically at higher risk to be less firmly bound to the surface. When an electrical field are exposed over the surface, any partly loose fiber will rise from the surface (same load on the fibers and surface crate repelling forces and makes the fibers stand out from the surface). There is known through US20120183771 a cellulose and/or synthetic fibre-based support of which at least one surface is coated with a layer containing at least one water-soluble polymer comprising hydroxyl or primary, secondary amino functional groups, at least some of which have been functionalized beforehand with at least one organic compound comprising at least one epoxy functional group, and at least one R1 group wherein R1 is a vinyl functional group or at least one Si(R2)3 functional group and wherein R2=hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations thereof. Through EP1807221 it is known, a method for forming a polymeric coating on a substrate surface, by plasma treating a mixture comprising a free-radical initiated polymerisable monomer having one or more free-radical polymerisable groups in the presence of a free radical initiator, wherein said plasma treatment is a soft ionisation plasma process (a process wherein precursor molecules are not fragmented during the plasma process and as a consequence, the resulting polymeric coating has the physical properties of the precursor or bulk polymer) aid depositing the resulting polymeric coating material onto a substrate surface. Further, through US 2005123678A it is disclosed that a surface of a continuous web, the fibrous portion of which consists of papermaking fibres, is coated with a coating powder. The web is allowed to move between electrodes, which are in different potentials. A coating powder of inorganic material and polymeric binder material is applied on the surface of the web by utilizing the difference in the electric potential. The coated surface of the web is then finished. The coating powder is said to comprise 10.1-99.5 wt.-% of inorganic material. A dry surface treated sheet material is thus formed. Further, through EP3737559A1 , it is disclosed a method to produce a veneered element, the method including applying a first layer on a substrate, applying a second layer on the first layer, applying a veneer layer on the second layer, pressing the first layer, the second layer and the veneer layer together to form a veneered element, wherein, after pressing, the second layer is transparent or translucent such that the first layer is visible through a crack, cavity, hole and/or knot of the veneer layer. Further, a fiber product can be made by pressing a web or a sheet of fibers. Typically, a combination of natural fibers (e.g. wood pulp fibers), synthetic fibers (e.g. polyolefin based fibers which may be polyethylene or polypropylene) and other additives such as binder or dye. In some applications it is preferred that such a web essentially merely comprises of natural fiber, with or without additives. Typical process conditions for said fiber product, which may e.g. be a packaging material or a structure for use in a packaging material, are 150 - 250 °C and pressures 100 - 10000 Bar (such as 200 - 2000 Bar). Moisture content may typically be less than 20%. When using e.g. cellulosic fibers in said above context, the fibers may give rise to unevennesses and/or disruptions. Thus, there is a need for a method whereby such unevennesses an