WO1997015430A1

WO1997015430A1 - Laminated products

Info

Publication number: WO1997015430A1
Application number: PCT/AU1996/000665
Authority: WO
Inventors: Denis Louis Elton Griffin
Original assignee: MAECHER PICTUREPRODUCTS Pty Ltd
Current assignee: MAECHER PICTUREPRODUCTS Pty Ltd
Priority date: 1995-10-23
Filing date: 1996-10-22
Publication date: 1997-05-01
Anticipated expiration: 1998-04-23
Also published as: AU668069B3; ZA968745B

Abstract

A decorated laminated product, such as a plate, is produced by taking a digitally stored image of the decorative material and printing it onto coated paper to form a high definition print which is then located beneath a paper surface sheet which is impregnated with a thermosetting resin. A second sheet of paper, also impregnated with thermosetting resin, is then positioned below the print and the assembly so formed is then located over material for forming a rigid substrate, such as a plate. Heat and pressure are applied to bond the assembly and the substrate. The process is such that the thermosetting resin provides a transparent protective covering over the print and bonds the print into the product.

Description

LAMINATED PRODUCTS TECHNICAL FIELD

The present invention relates to laminating products and, in particular, concerns applying a decorative design by laminating to a substrate.

One example of application of the invention is to the decoration of melamine articles, such as plates. BACKGROUND OF THE INVENTION

Australian Patent No 459,410 (25,681 /71 ) describes a process for laminating articles, such as melamine plates, and wherein a sandwich is formed of (a) a surface sheet of non-pigmented paper impregnated with thermosetting melamine-formaldehyde resin, (b) a decorated sheet of ordinary paper and (c) an underlying sheet of paper impregnated with thermosetting melamine-formaldehyde resin. This sandwich is laminated to a substrate by applying heat and pressure to the assembly to cause bonding and to form a decorated article. SUMMARY OF THE INVENTION

According to the present invention, there is provided a method of producing a decorated laminated product comprising printing a digitally stored image of the decorative material onto a coated paper to form a relatively high definition print, locating the print beneath a paper surface sheet impregnated with a thermosetting melamine-formaldehyde resin, positioning a second paper sheet impregnated with a thermosetting melamine-formaldehyde resin below the print, locating the assembly so formed over material for forming a rigid substrate, and applying heat and pressure to bond the assembly and the substrate to form a rigid product, the thermosetting resin providing a transparent protective covering over the print and bonding the print into the product.

Preferably, impregnation of the surface sheet and of the second sheet is such that the weight of resin is one and a half to three times the weight of the paper.

Preferably, the paper onto which printing occurs has low sheen, such as Epson Special Coated Paper suitable for 720 dpi printing (product code

#S041026) or a similar paper such as Hewlett Packard Inkjet Premium

Paper (product code #51 6342). Preferably, the method is initiated by first scanning artwork, such as a photographic print, into a computer to provide digitally stored information for the printing process. Successful scanning has been achieved of photographs using an Epson GT 9000 colour image scanner with Adobe

Photoshop software. However, similar products can also be used. The printing step, for example, can be carried out with the use of a high quality colour printer, such as an Epson Stylus Pro printer, which operates at about 720 dpi.

Surprisingly, it has been found that in contrast to the aforementioned prior art method, which has been restricted to use of certain types of coloured markers on bond paper, high quality results can be achieved with various embodiments of this invention without any degradation or blistering of the printed image and that significantly improved lamination occurs notwithstanding the nature of the paper and the type of ink used in the printing step. In another aspect, the invention extends to a laminated product produced by the aforementioned method.

DETAILED DESCRIPTION OF THE INVENTION For illustrative purposes, an example of the invention will now be described: EXAMPLE 1

An ordinary coloured photograph was scanned using an Epson GT 9000 colour image scanner using Adobe Photoshop software and a digitally stored image was thus recorded using a personal computer. The computer was connected to an Epson Stylus Pro colour printer and Epson special coated paper for 720 dpi printing was used. A print was made.

A surface sheet was prepared by impregnating a sheet of an alpha cellulose paper with an aqueous solution of a melamine-formaldehyde reaction product. Before impregnation, the alpha cellulose paper was .0045 inch thick and weighed 4.4 grams per square foot. After impregnation, the surface sheet was dried at 270°F for about one minute. The dried impregnated surface sheet was approximately .007 inch thick and consisted of 31 % by weight of alpha cellulose and 69% by weight of melamine-formaldehyde reaction product.

An assembly was created comprising a first impregnated sheet, the colour print and a second impregnated sheet, each being circular in shape and with a diameter slightly more than the diameter of the dinner plate to be decorated.

Finely divided commercial alpha cellulose-filled melamine- formaldehyde moulding composition, in an amount sufficient to produce a dinner plate, was consolidated under pressure into a preform, was preheated, and was placed between the dies which were used to form the dinner plate. The dies were at a temperature of 31 5°F, and they were closed upon the preform of the moulding composition under a pressure of about 3,000 lbs per square inch, and were held closed under that pressure for 80 seconds. The dies were then opened, and a subassembly of the sheets consisting of the non-impregnated printed sheet with the printed side uppermost, between two impregnated sheets, was placed on top of the moulding composition and the dies were then immediately closed to hold the assembly under the same pressure and temperature for 85 seconds. The dies were then opened and the dinner plate was ejected.

The method thus produced a rigid melamine plate formed under heat and pressure and incorporating an assembly which is bonded therewith as surface decoration. The manufacturing techniques are as described in Patent No

459,410.

The surface sheet which is used in producing a decorated moulded article consists of unpigmented paper impregnated with 1 V to 3 times its weight of a thermosetting aminoplast. The paper used for impregnation with a thermosetting aminoplast preferably consists of a substantially pure cellulose. For example, the paper may consist of 1 00% alpha cellulose fibre, or it may consist of a mixture of alpha cellulose fibre and rayon fibre, the proportion of each fibre usually being between 40% and 60% by weight. The additional sheet of paper, impregnated with a thermosetting aminoplast, interposed between the decorated paper sheet and the resin- impregnated moulding composition serves as a wick for supplying the fused aminoplast to the underside of the decorated paper sheet immediately after the application of heat and pressure to the assembly. Thus the additional paper sheet may be made of any desired material which can be impregnated with a thermosetting aminoplast. In the impregnation of a paper sheet which is to be used as the surface sheet (or as the additional sheet interposed beneath the decorated paper sheet), the thermosetting aminoplast preferably is applied in the form of an aqueous solution. The concentration of the impregnating solution may be any concentration which makes it possible to impart the desired amount of the aminoplast to the paper by an impregnating operation. Ordinarily the concentration of an aqueous solution of the aminoplast is from about 30% to about 70% solids.

A solution of a thermosetting aminoplast may be used to impregnate the paper in the usual manner. A continuous web of paper may be fed from a supply roll, and may be impregnated by means of coating rolls, or by passing it beneath the surface of the solution. Preferably the paper is initially impregnated by means of rolls and then is passed through the solution. Although the preferred aminoplast for use in the practice of the present invention is a melamine-formaldehyde reaction product, other amino triazines or other aldehydes, such as the amino triazines and aldehydes listed in US Patent No 2,841 ,571 , may be used in preparing the aminoplast. One amino triazine which may be used in place of melamine is gamma-methyl-gamma-acetyloimeloguanamine. Another amino triazine which may be used in place of melamine to produce an aminoplast for use in the practice of the present invention is 2-methyl glutaroguanamine. Either of those amino triazines, which are diguanamines, may be used to replace all or part of the melamine, for the reaction with formaldehyde to produce an aminoplast for use in embodiments of the invention. Also, a monoguanamine may be used to replace part of the melamine. For example, the resistance to coffee staining may be improved by replacing as much as 80 vol% of the melamine with benzoguanamine.

If a decorated moulded article having extremely high heat resistance and water resistance is not required, the cost of manufacture can be reduced by using a commercial water-soluble urea-formaldehyde reaction product as the aminoplast.

The resin impregnated moulding composition may be any finely divided composition such as melamine-formaldehyde or urea-formaldehyde moulding composition. For example, a solution of a melamine-formaldehyde reaction product which is the same as the solution used to impregnate the surface sheet may be employed to impregnate bleached sulfite pulp, or any other cellulosic filler. The dried impregnated filler, which preferably contains about 60 to 75% by weight of the formaldehyde-melamine reaction product and from about 25 to 40% of cellulose, is ground to a fine powder, together with modifiers such as pigments, zinc stearate or other lubricants, and phthalic anhydride or other acidic materials which serve as curing catalysts. EXAMPLE 2 A side plate was formed using the same steps as in example 1 except the side plate had an initial moulding of the plate body portion for 50 seconds and the step of bonding the assembly to the surface of the substrate was achieved in 70 seconds.

Various modifications may be made to details of the method steps without departing from the scope or ambit of the present invention.

Claims

1 . A method of producing a decorated laminated product comprising printing a digitally stored image of the decorative material onto a coated paper to form a relatively high definition print, locating the print beneath a paper surface sheet impregnated with a thermosetting melamine- formaldehyde resin, positioning a second paper sheet impregnated with a thermosetting melamine-formaldehyde resin below the print, locating the assembly so formed over material for forming a rigid substrate, and applying heat and pressure to bond the assembly and the substrate to form a rigid product, the thermosetting resin providing a transparent protective covering over the print and bonding the print into the product.

2. The method of claim 1 and further comprising taking a colour photograph and digitally scanning the photograph into a computer to form the digitally stored image which is then used for the remaining steps of the method.

3. The method of claim 2 wherein the method comprises using an Epson GT 9000 Colour Image Scanner with Adobe Photo Shop software.

4. The method of any one of the preceding claims wherein the printing step is effected using the inking technology used with an Epson Stylus Pro printer or a functionally equivalent printer using coated printing paper for 720 dpi printing of the type known as Epson special coated paper or

Hewlett Packard Inkjet premium paper or functionally equivalent paper. 5. The method of any one of the preceding claims wherein impregnation of the surface sheet and the second sheet is such that the weight of resin is in the range of 1 .

5 to 3 times the weight of the paper.

6. The method of any one of the preceding claims wherein the material for forming the rigid substrate comprises alpha cellulose-filled melamine- formaldehyde moulding material and the method further includes consolidating a sufficient quantity of this material under pressure into a preform which is formed into a plate-like object under heat of about 31 5°F and pressure of about 3,000 pounds per square inch for a time of about 80 seconds prior to application of the assembly thereto, the method further comprising applying pressure and heat for about 85 seconds to form the decorated laminated product.

7. The method of any one of the preceding claims wherein the resin is a thermosetting aminoplast.

8. The method of any one of the preceding claims wherein the surface sheet and the second sheet consist of a substantially pure cellulose.

9. The method of any one of the preceding claims wherein the resin is applied in the form of an aqueous solution.

10. A decorated laminated product produced by the method of any one of the preceding claims.

1 1 . A laminated product comprising a rigid substrate to which a decorative assembly is bonded under heat and pressure, the decorative assembly comprising a paper surface sheet which is impregnated with a thermosetting melamine-formaldehyde resin, a coated paper sheet disposed beneath the surface sheet and carrying a digitally printed image of decorative material on its face adjacent the surface sheet, and a second paper sheet which is impregnated with a thermosetting melamine- formaldehyde resin disposed below the coated paper and bonding the coated paper to the substrate, the surface sheet providing a transparent protected covering to the coated paper.