GB2095619A

GB2095619A - Sublimation printing method

Info

Publication number: GB2095619A
Application number: GB8109930A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-03-31
Filing date: 1981-03-31
Publication date: 1982-10-06
Also published as: GB2095619B

Abstract

A method of sublimation printing on materials provided with synthetic surfaces comprising cross-linking thermosetting plastics in the form of methacrylics, especially using polyisocyanate cross-linking agents wherein the thermosetting plastics is coated on one or both sides of the material, e.g. textile fabric, sheet metal, wood or synthetic material, and subsequently dried until completely or partly cross-linked, followed by the application of dyes according to the known thermosublimation process.

Description

SPECIFICATION Method for printing on surfaces of synthetic materials using the sublimation printing method The invention relates to a method for printing on surfaces of synthetic materials using the sublimation printing method. The invention in particular relates to the treatment prior to the sublimation printing method of the synthetic or natural materials which do not soften under the thermal treatment necessary for effecting this printing method.

The sublimation printing technique consists in the gaseous transfer of a single or multi colour intaglio print from an auxiliary print support onto the object to be decorated while heating under pressure during a specific time interval. It is already known by sublimation printing to process decoratively textile fabrics or knitted fabrics of natural or synthetic fibres. In accordance with the sublimation printing method the fabrics to be printed are distinguished in their chemicalphysical properties in such a way that during a heat treatment of 1 800--2200C and at a pressure of 0,4-0,7 p/cm2 a reversible structural change takes place which enables the molecular intercalation or addition of the dyes supplied in the gaseous state.Depending on the chemical makeup and the temperatures applied, this softening of the fibres starting at the surface under the said conditions of the supply of gaseous sublimation dyes can be advanced up to the non-softened fibre core. After a period of 1 5-40 secs. during which time the fabric is subjected to heat and pressure, the fibres harden and, depending on the depth of penetration, form a seal around the dyes which have been picked up.

In contrast to the chemical-physical acceptor properties for sublimation printing of synthetic fibres, natural fibres, because of their thermal instability, up to the start of the thermal carbonisation, cannot be changed chemically or physically. Because of this, sublimation printing is not suited for natural fibres.

However, through preparational measures they may be produced by either mixing with at least 50% synthetic fibres such as polyesters, polyacrylic nitrile or polyamide or mixtures of the same, or they may be produced by encasing the natural fibres with a synthetic material either during the manufacture of the fabric of afterwards in order thus to make the natural fibres accept the sublimation dyes.

In the case where the natural fibres are encased by synthetic materials, acid hardenable melamin formaldehyde resins, which are applied in partly cross-linked form, are available. After preparation however, the characteristic and progressively advancing reaction of these sublimation dye acceptors, which are afterwards applied to the natural fibre fabric in the form of an encasing synthetic material, requires that the sublimation dye be applied rapidly.

The reaction time necessary for the melamin formaldehyde resins is speeded up by the operating features necessary for the sublimation printing (1800--2200C, 0,4-0,7 p/cm2 for 1 5-40 secs.) and is ended depending upon the ingredients used. The reaction product resulting under the said operating conditions and including the sublimation dyes has the chemical structure which in contrast to the thermoplastic synthetic materials described has no repetitive acceptor properties.The synthetic material preparation which is applied to the natural fibre as a partly cross-linked and acid-hardenable melamin formaldehyde resion together with for example magnesium chloride as the hardener and for example 1,4 dimethylcyclohexane is characterised by its high degree of sublimation dye absorption during the simultaneous, and under favourable conditions complete cross-linking while subjected to the sublimation pressure taking place as a result of the said operating features. The limitation on the dye absorption capacity using this sublimation pre-printing treatment is the requirement of uninterrupted further processing in the sense that the said printing method must be applied to the pretreated natural fibre fabric promptly so that the pretreated fabric spends little time in storage.

It is furthermore known to pretreat non-textile organic and inorganic synthetic and natural fibres with thermoplastic substances which possess the aforementioned acceptor properties.

Investigations carried out in this context on melamin formaldehyde resins, for example on a laminated sheet of pressed board produced from a number of resin-coated papers, whilst having good dye absorption properties, resulted in qualitatively unusable board containing gas bubbles, which even the step-by-step changes in the ingredients in accordance with the recipes known at the time showed none or only a limited degree of the absorption which can withstand the demands made upon it by the normal domestic cleaning agents.

Because of the favourable acceptor effect of the known thermoplastics such as polyesters, polyacrylic nitrile and polyamide, these are applied to non-organic textile and inorganic synthetic or natural materials in the form of surface coatings.

For example, the surface to be treated may be electrostatically coated with a polyester layer which is applied to non-textile materials. The dyes applied by sublimation printing in their intercalation behaviour are similar to the thermally unstable synthetic fibres already described. As a result of this thermal instability polyester-coated non-textile materials should be used only within the context of comparable dye treating methods, i.e. no further thermal treatment under pressure and heat should be used since at a heat treatment of 1 600C the synthetic material becomes soft again and the intercalated dyes again start to migrate.

It is the object of the invention to eliminate these disadvantages when using the thermoplastic synthetic materials in surface treatments and to provide a method of the aforementioned kind wherein the natural fibre is encased by a synthetic material which can also be used for treating surfaces of non-textile organic and inorganic synthetic or natural materials as well as sheet metal or similar material.This object is achieved by providing a method for printing on synthetic surfaces using the sublimation printing method by applying pressure and heat to the sublimation dye arranged on an auxiliary support and the subsequent transfer and intercalation in the surface of the synthetic material which is characterised in that the synthetic surfaces comprise cross-linking thermosetting plastics in the form of (meth-) acrylates, especially polyisocyanate cross-linking thermosetting plastics which for example are applied by coating with dip roller or by spraying on one or both sides of textile fabrics, sheet metal, wood or synthetics and which by drying are subsequently completely or partly cross-linked, this being followed by the application of dyes according to the known thermosublimation process.

The method according to the invention has the essential advantage in that, when using polyisocyanate cross-linked thermosetting plastics, a dye absorption and colour brightness is achieved which can be compared with that of a polyester and within the context of sublimation printing comparable degrees of fastness are achieved. Thus, while the thermoplastics are of little use in the thermal reprinting method because of the said above disadvantages, the polyisocyanate cross-linked thermosetting plastics lead to substantially improved results.

The invention is now explained in more detail with the aid of a number of embodiment examples from which further features of the invention will become obvious.

In accordance with the features of the present invention, on at least one plane surface of thermal non-softenable organic or inorganic natural or synthetic materials the thermosetting plastic paint as described in the following was applied and completely cross-linked.

The materials which in accordance with all the particular sublimation dyes to be printed on were equally pretreated according to the invention using the following paint recipe.

1. Lacquer recipe 100 parts wt. (meth-) acrylates, preferably low molecular weight, 26-35 parts wt. polyisocyanate, preferably blocked, 1,5 parts wt, Ca-Octoate (33%).

1 a Lacquer recipe 1 5-24 parts wt. dimethylcyclohexane dissolved in 1 5-40 parts wt. ethylglycolacetate with an addition of 1-3 parts wt. of a polymethacrylic acid salt with 65-110 parts wt.

ethyl glycol acetate or 11 0-1 70 parts wt. ethyl glycol acetate in the case of paint receipe 1 a.

The preparation proceeds as follows: The natural fibre is impregnated by the dip roller method either according to recipe 1 or 1 a or is treated on one side by the spray coating method. The application method is followed by a drying process, normally carried out at a temperature between 11 50C-1 600C which causes the aforementioned synthetic materials to be cross-linked with a degree of cross-linking which is greater than 70% and which reaches about 1 00% after storing for 48 hours at room temperature.

The sublimation ink deposition takes place because the gaseous dyes supplied in accordance with the penetration depth always attach themselves to the non-cross-linked hydro functional groups inside the paint, i.e. the dyes form an addition compound with the thermosetting plastic.

A further embodiment example is described in which roller aluminium sheeting is pretreated with the materials as described in the invention for printing with the sublimation dyes. In this case the following paint recipe and preparation sequence is used as well as the cross-linking process with the sublimation dye absorption.

2. Lacquer recipe 100 parts wt. (meth-) acrylate, preferably low molecular weight, 1 6-35 parts wt. polyisocyanate, preferably blocked, 1,5 parts wt. Ca-Octoate (33%), 1 5-40 parts wt. ethyl glycol acetate, 5-10 parts wt. Xylol.

If necessary to this paint recipe may be added: 1-7 parts wt. pyrogen precipitated silicic acid and/or 20-30 parts wt. titanium dioxide.

In accordance with this recipe the rolled aluminium sheet is coated on one or both sides by means of the roller application method or the spray coating method. The application process is followed by the drying process, which normally is carried out at 1700--2100C, and which causes the aforementioned synthetic materials to be cross-linked by up to 100%.

The sublimation dye absorption by means of the reprinting method takes place for 1 5-40 secs. at 1800--2200C under a pressure of 0,4-0,7 p/cm2, the gaseous dyes under the same conditions entering the solid plastic and being deposited there centrally as seen in cross-section.

This addition compound which can be detected is determined by the position of the reactive hydrofunctional groups within the polymerisate.

Because of the addition compound it is possible to repeat thermal treatment under the same conditions several times since dye migration takes place only with the thermal decomposition starting at 2700C for 1 5-40 secs. The dye absorption and accumulation thus described is characterised by the same applicability on all carrier materials.

Naturally, the method according to the invention can also be split up, whereby the sheet or foil is first of all provided with the polyisocynate cross-linked thermosetting plastic and at a later point in time is printed on with the sublimation dyes according to the above described method.

In a further development of the method according to the invention a (meth-) acrylate may be used which has a hydroxyl content (weight % OH to solid resin) approx. 1,5--4,4 Hydroxyl content of solid resin (5 5--1 05 mg KOH/g).

This enables the surface to be marked, for example by means of a felt-tip pen, and to be erased again.

Naturally, the cross-linking of the thermosetting plastic may also be carried out in the form of (meth-) acrylates by physical means, for example by radiation with electron beams of UV light.

Claims

1. Method for printing on synthetic surfaces of materials using the sublimation printing method, characterised in that the synthetic surfaces comprise cross-linking thermosetting plastics in the form of (meth-) acrylates, especially polyisocyanate cross-linking thermosetting plastics which are applied by coating on one or both sides of textile fabrics, sheet metal, wood or synthetics and subsequent drying until completely or partly cross-linked, followed by the application of dyes according to the known thermosublimation process.

2. Method according to claim 1, characterised in that the polyisocynate treated thermosetting plastic is a lacquer containing the following ingredients.

100 parts wt. (meth-) acrylate, preferably of low molecular weight, 26-35 parts wt. polyisocyanate, preferably blocked and 1,5 parts wt. Ca octoate (33%).

3. Method according to claim 1 , characterised in that the polyisocyanate treated thermosetting plastic is a lacquer containing the following ingredients.

100 parts wt. (meth-) acrylate, preferably of low molecular weight, 26-35 parts wt. polyisocyanate, preferably blocked, 1,5 parts wt. Ca-octoate (33%), 1 5-24 parts wt. 1,4 dimethylcyclohexane dissolved in 1 5-40 parts wt. ethylglycol acetate, 1-3 parts wt. of a polymethacrylic acid salt with 65-110 parts. or 110-170 parts.

ethyl glycol-acetate.

4. Method according to claim 1, characterised in that the polyisocyanate treated thermosetting plastic is a paint containing the following ingredients.

100 parts wt. (meth-) acrylate, preferably low molecular weight, 26-35 parts wt. polyisocyanate, preferably blocked, 1,5 parts wt. Ca-octoate (33%), 1 5-40 parts wt. ethyl glycol acetate, 5-10 parts wt. Xylol.

5. Method according to claim 4, characterised in that the paint also contains 20-30 parts wt. titanium dioxide.

6. Method according to claim 4 or 5, characterised in that the paint also contains 1-7 parts wt. pyrogenically precipitated silicic acid and, if necessary or suitable, dye additive for enhancing the brightness.

7. Method according to any one or more of the aforementioned claims, characterised in that the (meth-) acrylate has a hydroxyl content (wt. % OH to solid resin) approximately 1,5--4,4 hydroxyl content of solid resin (55-1 50 mg KOH/g).

8. Method according to claim 1, characterised in that the (meth-) acrylate is cross-linked physically, for example by subjecting it to electron radiation or UV light.

New claims or amendments to claims filed on 5 Jan. 1982.

Superseded claims 1.

New or amended claims:

1. Method for printing on synthetic surfaces of materials using the sublimation printing method, characterised in that the synthetic surfaces comprise cross-linking thermosetting plastics in the form of polyisocyanate cross-linking (meth-) acrylates which are applied by coating on one or both sides of textile fabrics, sheet metal, wood or synthetics and subsequent drying until completely or partly cross-linked, followed by the application of dyes according to the known thermosublimation process.