COATING OF CELLULOSIC SUBSTRATES WITH A MATERIAL CURABLE BY RADIATION AS A REPLACEMENT OF AQUEOUS COATINGS

Abstract

The present invention refers to a process for pre-coating substrates with copy a matrix surface by curable material for use in industrial printing systems and allowing the advantageous production of substrates ready for printing or finishing. It also refers to the machines necessary to its attainment, in particular those that allow the simultaneous coating of two opposite surfaces of the substrate.

Claims

1-16. (canceled)

17. Process of pre-treatment of a cellulosic substrate by a copy of a surface of a matrix with a material curable by radiation in order to make it capable of receiving new layers of materials, characterized by the fact that the pre-treatment consists of the polymerization of the material curable by means of ultraviolet radiation or by a beam of electrons and comprises of the following stages: a) Apply at least one layer of the material curable by radiation on the surface of the matrix; b) Arrange a perfect contact between the surface of the substrate with the surface of the matrix; c) Polymerize the curable coating by means of exposure to ultraviolet radiation or by a beam of electrons of the surfaces of the substrate and of the matrix while the surfaces of the substrate and of the matrix are in perfect contact; and d) Separate the surfaces of the substrate and of the matrix leaving the cured coating completely adhered to the surface of the substrate after the stage of polymerization.

18. Process of pre-treatment of a cellulosic substrate in accordance with claim 1 characterized by the fact that the surface of the substrate with the cured coating has an optical surface characteristic that is shiny or matte.

19. Process of pre-treatment of cellulosic substrate in accordance with claim 17 characterized by the fact that it additionally comprises of the stage of: e) Apply a second layer of material after stage d) that reduces the porosity of the surface of the cellulosic substrate.

20. Process of pre-treatment of a cellulosic substrate in accordance with claim 19 characterized by the second layer of coating being composed of silicone.

21. Process of pre-treatment of a cellulosic substrate in accordance with claim 17 characterized by the fact that curable material is one within a group constituted of inks, lacquers and varnishes.

22. Process of pre-treatment of a cellulosic substrate in accordance with claim 17 characterized by the fact that the cellulosic substrate has a surface with low porosity and the curable material is epoxidised soybean oil.

23. Process of pre-treatment of a cellulosic substrate in accordance with claim 17, characterized by the fact that the ratio of curable material used is 4 g/m.sup.2.

24. Process of pre-treatment of a cellulosic substrate in accordance with claim 17, characterized by the fact that application mechanism of the curable material consists of a kissroll system and a system of solventless type laminators.

25. Process of pre-treatment of a cellulosic substrate in accordance with claim 17, characterized by the fact that the application of the curable material is performed on the two opposite surfaces of the cellulosic substrate simultaneously.

26. Process of pre-treatment of a cellulosic substrate in accordance with claim 17, characterized by the fact that in stage c) the radiation is emitted through the cellulosic substrate in order to polymerize the curable material.

Description

DETAILED DESCRIPTION OF THE FIGURES

[0088] The following nomenclature applies to all the figures:

[0089] AUV curing unit BEB curing unit

[0090] C1, C2Points of possible application of coating DSubstrate

[0091] E1Transparent cylindrical matrix

[0092] E2Cylindrical matrix

[0093] E3Film-shaped matrix

[0094] E4Continuous belt-shaped matrix

[0095] In FIG. 1, a coiled film-shaped substrate D passes through at least one station for the application of the coating curable by radiation C1 or C2, and is pressed against a cylindrical-shaped matrix E1 transparent to UV rays. This transparent matrix is hollow and contains within it a UV A cure unit that will emit the necessary radiation beam to cure the coating then adhered to the substrate.

[0096] In FIG. 2, a coiled film-shaped substrate D passes through at least one station for the application of a coating curable by radiation C1 or C2 and is pressed against a cylindrical matrix E2 so that said radiation-curable coating is between the cylindrical matrix E2 and the substrate D. Therefore, the electron beam from unit B, passes through the substrate and cures the coating on the opposite surface.

[0097] The energy electron beam has a penetrating power greater than UV rays and, therefore, this physical characteristic can be used with advantages, since the presence of atmospheric oxygen results in undesirable chemical reactions in the coating, which impacts the quality of the treatment and may even make their application unfeasible, hence the need to cure these compounds in an inert atmosphere. When irradiating on the reverse side of the substrate D, only a negligible amount of air will be trapped between the matrix E2 and the substrate D, which dispenses with the complex inerting equipment.

[0098] In FIG. 3, a coiled film-shaped substrate D that passes through at least one station for the application of a curable coating by radiation C1 or C2 and is pressed against a film-shaped matrix which unwinds and is wound after being detached from the substrate D between the coils E3. While in close contact to the substrate D, the coating receives the UV radiation from unit A.

[0099] FIG. 4 describes a coiled film-shaped substrate D that passes through at least one station for the application of a curable coating by radiation C1 or C2 and is pressed against a film-shaped matrix which unwinds and is wound after being detached from the substrate D between the coils E3. While in close contract with the substrate D, the coating receives the electron beam (EB) from unit B from the opposite side of matrix E3 in the form of a film.

[0100] FIG. 5 describes a coiled film-shaped substrate B passing through a station for the application of a coating curable by radiation C1 or C2 and is pressed against a continuous belt-shaped matrix E4. While in close contact with substrate D and the coating receives the UV radiation from unit A.

[0101] FIG. 6 describes a coiled film-shaped substrate D passing through at least one station for the application of a coating curable by radiation C1 or C2 and is pressed against a continuous belt-shaped matrix E4. While in close contact with the substrate D, the coating receives the electron beam (EB) from unit B from the opposite side of the matrix E4 as a continuous belt.

[0102] FIG. 7 describes a coiled film-shaped substrate D passing through at least two station for the application of coatings curable by radiations C1 and C2 and are pressed against a continuous belt-shaped matrix E4. While in close contact with substrate D, the coatings receive the electron beam (EB) from unit B from the opposite side of the continuous belt-shaped matrix E4, wherein said electron beam is capable of passing through the continuous belt shaped-matrix E4, the coating, the substrate D and curing the coating layer applied to the opposite surface.

[0103] These description are simply illustrative and intend in no way to limit the possibility that the persons skilled in the art may suggest.

EXAMPLE 1

[0104] Use of pre-coating of substrates with copy of the matrix surface smoothed by radiation-curable material in order to obtain a printing surface of a higher quality than couch paper, traditional in the market.

[0105] In this specific case, the formulation A1 for curing by ultraviolet lamps or B1 for curing by electron beam in the ratio of 4 g/m.sup.2 on monolucent white kraft paper was used with a model 3 machine, application position C1. Flexographic printing was then done with water-borne and solvent-based inks. Comparison of the print quality result with that conventionally performed with couche paper revealed that the performance was higher than that which is regularly obtained in the conventional couche, resembling the result of a couche cote manufactured by the company Brasilcote in the castcote technology mentioned above, but with the cost, time and productivity gains also explained above.

EXAMPLE 2

[0106] Use of the pre-coating of substrates with copy of the matrix surface smoothed by radiation-curable material in order to obtain a printing surface of a superior quality and with reduced porosity as a basis for the application of silicone for use as liner of self adhesive papers with the significant reduction of silicone consumption. In this specific case, the formulation A2 for curing by ultraviolet lamps or B2 for curing by electron beam in the ratio of 6 g/m.sup.2 on monolucent white paper short fiber 60 g/m.sup.2 with a model 3 machine application position C1.

[0107] The material was later sent for silicone application, where it was possible to register a reduction of the order of 35% of the silicone application with the maintenance of the same self adhesive release properties.

EXAMPLE 3

[0108] Use of the pre-coating of substrates with copy of the smooth matrix surface by radiation-curable material with simultaneous transfer of coating, coating or metallization of the copied surface to the substrate.

[0109] In this specific case, the formulation A1 for curing by ultraviolet lamps or B1 for curing by electron beam in the ratio of 4 g/m.sup.2 on monolucent white kraft paper was used with a model 3 machine, application position C1. The basic objective was to transfer the metallization made on a low adhesion polyvinyl butyral coating with a weight of less than 1 g/m.sup.2 applied to a 45 micron BOPP film whose metallization performed by means of vacuum metallization on the respective coating was transferred by displacement to the surface of the substrate. The thus-treated substrate exhibited a metalized surface with the same characteristics of the metalized film, but without the consumption of the BOPP film and with full recyclability.