CA1060277A

CA1060277A - Metallized paper

Info

Publication number: CA1060277A
Application number: CA242,416A
Authority: CA
Inventors: Youkichi Taniguchi; Tadashi Kubota
Original assignee: Alcan Research and Development Ltd
Current assignee: Alcan Research and Development Ltd
Priority date: 1975-12-23
Filing date: 1975-12-23
Publication date: 1979-08-14
Also published as: SE7514614L; DE2600167A1; CH606606A5; NL7600038A; AT346688B; ATA1476A; FR2337228A1; GB1556805A; BE837307A; DE2600167B2; JPS52137017A

Abstract

Abstract of the Disclosure A method of making a metallized paper web is disclosed, in which a film of synthetic resin coating agent is deposited onto a continuously running band having a release surface, a web of paper is continuously fed towards the release surface to engage it, and the paper web is pressed against the release surface so that the paper is coated with a coherent layer of coating agent having a surface determined by the contour of the release surface. The re-lease surface is then released from the coated paper web which is thereafter metallized. Thus, the configuration of the metallized surface is determined primarily by the surface contour of the release surface rather than by the surface of the paper web substrate.

Description

~L06(:~Z77 ~his invention relates to a method of making metallized paper webs and more particularly to making metallized paper webs having a smooth and therefore specularly reflective surface.
Paper webs have surfaces which are matt so that when 1 5 they are metallized by vacuum (vapour) deposition the metal-j lized surface has a matt ash-coloured surface and lacks ¦ metallic lustre. To obtain a shiny finish a relatively ¦ thick coat of a synthetic resin is applied to the paper and ¦ is solidified on the paper. In order to obtain a suitably reflective surface for metallizing, it may be necessary to apply two or more coats of synthetic resin. If a very thin J film of a resinous coating agent is applied by a conventional ¦ coating technique, the coating acquires a surface corres-¦- ponding to the surface of the underlying paper substrate.
When a relatively thick coating of resin is applied the coated paper tends to curl and also becomes difficult to fold.
The present invention provide~ a method of overcoming these difficulties.
¦ ~he present invention accordingly provides a method of making a metallized paper web characterised i~ that the process comprises the steps of:
depositing a film of a synthetic resin coating agent in a flowable condition onto a continuously running band having a release surface;
continuously feeding a web of paper towards the said .

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60Z~17 release surface so as to enga~e therewith;
pressing the paper web against the release surface coated wiuh the coating agent whereby the paper is coated with a coherent layer of coating agent having a surface determined by the contour of the release surface;
¦ 5 releasing the release surface fr~m the paper web and the coherent layer of coating agent adherent thereto; and subsequently metallizing the coated paper web.
The principal distinction between the products of the ¦ prior art and those of the present invention is that, ¦ 10 whereas in the prior art the configuration of the metallized ¦ surface ls determined primarily by the surface of the paper web substrate, in the present in-~ention the configuration of the metallized surface is determined primarily by the contour or surface condition of the release surface and not by that of the paper web substrate.
Preferably the release surface is specularly smooth by which we mean that the surface is mirror-like where the underlying material is itself reflective e.g. stainless steel or is similarly smooth where the material is itself non-reflective e.g. plastics films. If desired the surface may be engraved e.g. with a decorative pattern or identi-fying symbols or words. Where the release surface is engraved it is still preferred that at least the remainder of the surface be specularly smooth, i.e. the une~graved areas.

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~06()277 Use of an engraved and specularly smooth release surface gives a metalli~ed product with an embossed but still mirror-like finish. The engraved areas may be specularly smooth or matt. In the latter case it increases the contrast of the embossed areas.
The synthetic resin coating agent can be either thermo-plastic or thermosetting. The agent can be deposited onto the transfer surface in solution either in water or a non-aqueous e.g. organic solvent, as an emulsion or plastisol or in the liquid form e.g. as with hot-melt coatings. Where a hot-melt coating is employed it may be applied in powder form and melted in situ on the release surface. The amount ~ -of coating agent used in the present invention is typically -from 1 to 15 grams per square metre of paper web substrate.
This is, very approximately equivalent to a coating having an average thickness of from l,u to 15,u which is much less than is necessary for a self supporting film especially of "as cast" synthetic resin materials. If less than 1 g/m ;~
of coating agent is used the eventual metallized surface may be more like the surface of the paper web substrate than that of the release surface. Preferably the coating weight is in the range 3-5g/m2. Use of more than 5 g/m2 does not generally bring any substantial further improvement and, as is mentioned above, with large amounts of coating agent such as 25g/m2 or above the product loses its paper properties and ~
becomes more difficult to handle. ;
In applying the coating agent to the paper it is ~4~

, ' ' ' ~(~602 ~77 ; important to ensure that the coating agent is set, solid-ified or cured sufficiently by the time it is released from the release surface to ensure that the coating retains the surface characteristics of the release surface. Where the coating agent is used in the form of a solution or emulsion it is ad~antageous if at least a part of the solvent or continuous phase is removed e.g. by evaporation before the film of coating agent and paper web are brought together.
I This reduces possible problems of the paper absorbing fluid ¦ and allows the coating agent to form at least a partially coherent film having a surface complimentary to that of the release surface before coming into contact with the paper web. In any event by the time the film of coating agent, adhering to the paper, is removed from the release surface the coating agent must be in the form of a coherent and ¦ 15 substantially non-flowable film. This generally means that , the coating agent is,by that time, solid. With hot melt ¦ coating agents this can be achieYed by cooling the film of agent in contact with the paper, if necessary having previ-ously thermally activated the hot melt coating agent. With coating agents in solution or emulsion form it will be necessary to remove the solvent or emulsion continuous phase if this has not been completed before bringing the paper web and film of coating agent together. This can conveniently be done by heating e.g. by passing the paper web in contact with the film of coating agent on the release surface between a set of heated rolls. Subsequently the paper web ., ~,~ .

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and coatlng a~gent are cooled to ensure satisfactory coherence of the coating agent.
The invention will be described further with reference . ~ to the accompanying drawings in which:
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Figure 1 illustrates, ir a dia~'rammio way, a process -1, . .

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according to an embodiment of the invention;
Fig. 2 is a diagramatical view illustrating a process of a further embodiment of the invention;
Figs. 3 and 4 are enlarged diagramatical views showing the main parts of the above embodiments;
Fig. 5 is a diagramatical view showing a process of a still further embodiment of the invention;
Fig. 6 is a lO0 x enlarged photograph showing an untreated paper surface;
Fig. 7 is a photograph in the same magnification, showing a paper surface treated by a conventional coating method; and Fig. 8 is a photograph in the same magnification, showing a paper surface treated by the process of the invention.
Throughout the drawings, similar steps~ parts and elements are shown by similar reference numerals and letters.
Referring now to Figs. 1, 3 and 4, the numeral 1 designates a coating station including a bath 2 containing a synthetic resin coating agent A, and rolls 3 and 4 for applying the coating agent to an endless belt 5. The method of coating the agent A on the endless belt 5 may be any known one, for example, rotogravure coating, roll coating or hot-melt coating. The coating agent A is either thermo-plastic or thermo-setting synthetic resin, which may be water-soluble, solvent-soluble or emulsive.
Said endless belt 5 has an outer surface easily releasable from the coating agent A when the latter ~060277 thin resilient steel such as stainless steel strip which is given a mirror-like finish known in the art as "super-~inish".
Alternatively, the belt can be a plastics strip having a suitably smooth sur~ace e.g. polyolefine sand polyesters such as terephthalate esters. The release properties of the surf-! 5 ace can be improved by coating the sur~ace with a smooth layer of a substance having particularly good release properties such as fluorinated polymeric hydrocarbonsespecially poly-tetrafluoroethylene e.g. Teflon (Trade Mark) and silicones.
Where the release surface is a plastics material it can be ln supported or reinforced by, for example, glass fibre cloth.
¦ The endless belt 5 may be engraved with a predetermined ' ~ C6~
pattern in its outer surface. However, the cm~oosc~ surface should be finished microscopically smooth.
Said endless belt 5 is supported and t:cavelled by means ¦ 15 of roll~ 6,7 and 8 and a cooling roll 9.
The numeral 10 is a paper web, the uncoiled extension of which is adapted to pass, while being pressed against the outer surface of the endless belt 5, through a heating roll 11 and a cooling roll 12 which are opposed to the rolls 8 and 9 respectively. The numeral 13 designates a treated web being coiled. The numerals 14 and 15 illustrate a drying zone and cooling zone respectively, In operation, at the coating station 1 the coating agent A is applied to the outer smooth surface of the endless belt 5' which then travels along the drying zone 14 to dry the , , ' ' . ~ . ~ .
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coating agent. The paper web 10~ which is uncoiled and fed towards the rolls 8 and 11, is engaged and pressed against the outer surface of the endless belt 5 between the roll 8 and heating roll 11~ whereby the paper web is adhered to the coating agent A on the outer surface of the endless belt 5.

06027~7 Thereafter the endless belt 5 together with the paper web passes through the coolingjzone 15 to solidify the coating agent A, which is now securely lamina~ed as a synthetic resin film on the paper web, which is then parted from the endless belt 5 at the opposed cooling rolls 9 and 12 thereby causing said synthetic resin film on the paper web to release from the outer surface of the endless belt 5, as seen from Figs. 3 ~nd 4. This release can be smoothly performed without iri~ing the synthetic resin film (coating agent) since the outer sur-face of the endless belt 5 has a property easily releasable from a synthetic resin (coating agent) film which ~ras pressed and securely engagcd with the surface of the paper web by means of the rolls 8 and 11. In case that the coating agen-t is thermo-setting it is cured at the heating roll 11.
In the above operation, if the surface of the endless belt 5 is flat, then the synthetic resin film having the same surface is formed on the paper web, while if the surface cf the endless belt 5 has an embossed pattern, the synthetic resin film having the complementary pattern is laminated on the paper web. In any case the paper web is gi~en a controlled smooth surface suitable for metallizing Also in the above operation, if the hot-melt coating is employed at the coating station 1, a synthetic resin of hot-melt type can be used as a coating agent. In this case the drying zone 14 is replaced by a cooling zone. The other steps are the same. In any ~ype of coating agent, it is possible to mix flllers, extender pigments, color pigments, dyes or like substances.

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As shown by the dot-dash lines in Fig. 1, instead of the ~ndiess belt 5 may be used a roll of sheet or film B
having a surface condition similar to the endless belt 5 and having a length sufficient for treating the paper web. The extension of the sheet B travels through the rolls 6, 7, 8 and 9, and is then coiled at C departing from the paper web.
As will be understood, since the endless be]t 5 or the sheet B serves as a support for the synthetic resin film (coating agent), even a very thin film can readily be treated without tear, and the treatment of the paper web can be per--formed by a single and continuous process. After the treatment, the paper web is metallized by vacuum evaporation to present an excellent metallic luster owing to the smoothness of the controlled surface of synthetic resin film on the paper, which was given by the identically controlled surface of the endless belt 5 or sheet B (see Fig. 8, hereinafter explained).
Fig. 2 shows another embodiment of the invention. In the figure, the numeral 16 is a laminating station including opposed pressing rolls 17 and 1~. The numer~ 19 is a heating roll. Other parts and elements are the same as the previous embodiment.
In operation, at the coating station 1 the endless belt 5 is coated with the coating agent A. Then at the laminating station 16 the uncoiled paper web is pressed against the endless belt 5 the outer surface of which was coated with the coating agent A, which is thus secured to the paper web. The endless belt 5 together with the paper web travels towards the roll 7.

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. . - ~ ~ , ` ` 1060ZD77 during passing along the drying ~one 14 and the heating roll 19 the coating agent is dried, which is in turn cooled to solidify during passing through the cooling zone 15. There-after the paper web with the synthetic resin film (coating agent) secured thereto is released from the endless belt 5 at the opposed cooling rolls 9 and 12, and is then coiled at 13.
Various modifications similar to the first embodiment can also be applied to the present embodiment. The hot-melt coating may be employed at the coating station 1. Fillers, dyes and like substances can be mixedin the coating agent A.
Fig. 5 shows a still further embodiment of the invention.
In the figure a cylindrical drum 20is provided with an outer surface of a property easily releasable from the coating agent A when solidified. For the purpose the drum 20 is covered therearound with the synthetic resin material referred to in the first embodimentj and more particularly, for example, with Teflon (Trademark). In another example, the outer periphery of the drum 20 of hard metal is given a mirrorlike finish.
In operation, at the coating statîon 1 the coating agent A is coated on the outer periphery of said drum 20 being rotated. The coating agent A on the drum 20 is dried during passing along a drying zone 21, and thereafter at a pressing roll 22 the paper fed from the paper web 10 is pressed against the outer periphery of the drum 20. As the paper adhered on the drum 20 passes through a cooling zone 23, the coating agent A is cooled to solidify. The paper with the synthetic resin film (coating agent) secured thereto is released from the outer periphery of the dr~m 20 at a roll 24j and is then coiled at 1~. If required, a heating zone 25 and/or heating and pressing rolls 26 can be provided so as to improve adhesion , of the paper against the coat,ing agent. Also a heating zone 27 and/or hqating and pressing rolls 28 can be provided for `~ the further improvement of the surface of synthetic resin film on the paper. The paper web thus treated is metallized by vacuum evaporation.
The following are examples aocording to the prooess of the first embodiment (Fig. 1).
EXAMPLE 1 ' , Endless belt 5: 0.6mm thick mirrorlike finished stainless steel plate Coating agent: vinyl and acrylic resin mixture (ratio 7:3j, -solid content: 25%
(Dai-Nippon Ink Co., Ltd., Japan article number AF-400~
Coating weight: lg, 2g, 3g, 4g, 5g per square meter in the state dri'ed on the paper web~
Condition of drying at 14: hot air, temperature: 150C
Lamination temperature at roll 11:170C
Running speed of endless belt: 30m/min.
The results are as follows:-Coating weight Lus-ter after metallizing with all~inium lg ' pretty good but lacking in uniformity 2g - ditto -3g uniform and good luster 4g - ditto -g - ditto -`` 10602'77 Roll of film B: O.Ol?mm thick polyethylene- j terephthalate film Coating agent: one component thermo-setting acrylic resin emulsion, solid content: 40%
(Hoechst Gosei Co., Ltd., Japan, Trademark:
MOWINYL, article number ~9000) Coating weight: 3g per square meter, dried on the paper web Condition of drying at 14: hot air and infrared heater, temperature: 150jC
Lamination temperature at roll 11: 150 to 160C
Running speed: 30m/min.
By the above EXAMPLE 2, the metalllzed paper having a good - luster similar to the EXAMPLE 1 has been obtained.
Fig. 6 shows a surface conditio~ of an untreated paper.
As appears, the surface is very rough. Fi`g. 7 shows a surface condition in which a synthetic resin coating agent of 5g/m2 (dried) was applied to the paper of Fig. 6 by a conventional coating method. As seen, the surface is still rough, and when metallized it presents ash color due to the diffused relfection of light. On the other hand, Fig. 8 shows a surface condition of the paper with a synthetic resin film formed by the process according to the EXAMPLE 1, the coating weight being 3g/m2(dried) _ 14 -'' 1060Z~7 -much less th~n the previous conventional method of Fig. 7.
As appears, the .surface is much improved, and therefore is suitable for metallizing or printing. By any conventiGnal method it is impossible to ob-tain a smoo-th surface by such an extremely thin synthetic resin film layer. According to the present invention, therefore, the propertie.s of a paper will be little injured by an applied coating agent. ~lr-ther-more the present invention makes it possible to obtain a con-trolled surface of a paper by a single continuous process thereby improving the productivity.
The process of the invention can be applied to any paper by using any kind of`synthetic resin as a coating agent. The only thing to be considered is that the endless belt 5, sheet B or drum 20 should have a controlled smooth surface having a better releasability with respect to the coating agent as compared with the paper web to be filmed by the coating agent.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of making a metallized paper web characterized in that the process comprises the steps of: depositing a film of a synthetic resin coating agent in a flowable condition onto a continuously running band having a release surface; continuously feeding a web of paper towards the said release surface so as to engage therewith; pressing the paper web against the release surface coated with the coating agent whereby the paper is coated with a coherent layer of coating agent having a surface determined by the contour of the release surface; releasing the relase surface from the paper web and the coherent layer of and substantially non-flowable coating agent adherent thereto; and subsequently metallizing the coated paper web.

2. A method as claimed in claim 1 characterised in that the release surface is specularly smooth.

3. A method as claimed in either claim 1 or claim 2 wherein a layer of the coating agent is deposited onto the release surface, the release surface is then heated, in the case of a coating agent in the form of a solution or emulsion to remove substantially all the solvent or emulsion continuous phase and in the case of a hot-melt coating to thermally activate the coating, subsequently bringing the release surface carrying the layer of heated coating agent into contact with the paper web and cooling the release surface, coating agent and paper web together to solidify the coating agent before releasing the coated paper web from the release surface.

4. A method as claimed in either claim 1 or claim 2 wherein a layer of the coating agent is deposited onto the release surface, the paper web and release surface are then brought into contact and the release surface, coating agent and paper web are then heated, in the case of a coating agent in the form of a solution or emulsion to remove substantially all the solvent or continuous phase and in the case of a hot-melt coating to thermally activate the coating, and subsequently cooled to solidify the coating agent before releasing the coating agent from the release surface.

5. A method as claimed in claim 1 characterised in that the release surface is the surface of an endless belt.

6. A method as claimed in claim 1 characterised in that the release surface is the surface of a roll of sheet having a length sufficient to allow treatment of the paper web.

7. A method as claimed in claim 1 characterised in that the release surface is the surface of a cylindrical drum.