GB2201613A

GB2201613A - Wallcovering and their production

Info

Publication number: GB2201613A
Application number: GB08805242A
Authority: GB
Inventors: Frank Milton Jepson
Original assignee: NAIRN CONTRACT FABRICS Ltd
Current assignee: NAIRN CONTRACT FABRICS Ltd
Priority date: 1987-03-05
Filing date: 1988-03-04
Publication date: 1988-09-07
Anticipated expiration: 2008-03-04
Also published as: GB2201613B; GB8705154D0; GB8805242D0

Abstract

A wallcovering comprises a coated substrate wherein the coating is substantially free of halogen, has a dry weight of at least 20g/m<2> and comprises a fire retardant that is substantially free of halogen (often aluminium trihydrate) and a film-forming resin that is substantially free of halogen (often an acrylic or vinyl acetate resin).

Description

Wallcoverings and their Production Traditional wallcoverings are made by applying print or other decoration to paper or other suitable substrate.

If the wallcovering is to be washable a thin lacquer coating is applied over the decorated surface. The lacquer may be based on, for instance, acrylic resin or vinyl resin and the coating may have a dry weight of up to, generally, 5 g/m2.

With any particular paper substrate the print quality and the strength can be improved by applying a thin acrylic coating over the substrate, beneath the print. The dry weight of coating is usually below 5 g/m2.

Where particularly good print or other decorative effects are required and where high or physical strength is required the products known as vinyl wallcoverings are produced. These consist of a substrate carrying a heavy polyvinyl chloride coating on which appropriate decoration is applied, optionally covered by a lacquer.

If the substrate is of paper and the coating weight of the polyvinyl chloride composition is, for instance, about 80 g/m2 the product is suitable for domestic use.

If the substrate is stronger, for instance being a non-woven or other fabric, and the polyvinyl chloride composition weight is heavier, for instance 200 to 1,000 g/m2, the product is suitable for contract use.

The vInyl composition making up this coating of, for instance, 200 to 1,000 g/m2 is formed of polyvinyl chloride, plasticiser, filler, pigment and conventional additives. The plasticiser is usually a phthalate and so the composition contains a large amount of chlorine (from the polymer) and aromatic compounds (from the plasticiser). Its content, especially its chlorine content, renders the composition very slow to ignite but if and when combustion does start the polyvinyl chloride composition rapidly causes smoke that is dense (due particularly to the aromatic content) and that is irritant, corrosive and toxic (due partly to the chlorine that forms hydrogen chloride upon combustion).

It would therefore be desirable to reduce the risk of the wallcovering generating such smoke - without adversely affecting the flame retardancy.

It might be thought that this could be achieved by including additional fire retardant so as to reduce still further the risk of the wallcovering igniting.

Unfortunately the great majority of fire retardants that can be included in the compositions are materials that will contribute to dense smoke formation if the wallcovering becomes ignited and so could make the situation even worse in a serious fire. Examples are, for instance, phosphate fire retardants and fire retardants based on antimony and halogen.

According to the invention a decorative wallcovering is substantially free of halogen and comprises a coated substrate in which the coating is formed of a composition that is substantially free of halogen, has a dry weight of at least 20 g/m2 and comprises a fire retardant that is substantially free of halogen and a film-forming resin that is substantially free of halogen. There may be decoration printed -on the coating and there may be a lacquer coat over any such printing.

Thus in the ina-e..70n iion the co.iventional polyvinyl chloride coating is replaced by a coating of halogen-free film-forming resin and halogen-free fire retardant.

Since the resin is not a vinyl chloride resin the coating does not have to contain a plasticiser for vinyl resin and so it is also possible for the coating composition, and for the entire wallcovering, to be substantially free of aromatic compounds as well as being substantially free of halogen.

The resin may be selected from any halogen-free, and preferably aromatic-free resins that are film-forming and that can provide a coating that will serve as a base for printed or other decoration. The resin should not introduce components that, upon ignition, give toxic fumes. Acrylic resins and vinyl acetate resins, particularly copolymerised with ethylene or acrylics, can be used. Preferred resins are ethylene/vinyl acetate, vinyl acetate/butyl acrylate, and ethyl acrylate/butyl acrylate. The resin may include cross linking groups in order that the resin cross links upon drying, optionally with heating. Typical ethylene/vinyl acetate copolymers have an ethylene content of less than 20to, often 5 to 10%.

The film-forming temperature of the resin is preferably below 1500 C, and most preferably below 1000 C, since this permits the use of fire retardants that are unstable at higher temperatures. In particular it permits the use of fire retardants which have not previously been usable in polyvinyl chloride wallcoverings because of their instability at the high processing temperatures (about 1800C or higher) typically encountered during the production of vinyl wallcoverings.

The preferred fire retardants for use in the invention are inorganic hydrates, most preferably alumina trihydrate.

Preferred coatings according to the invention comprise 1 part by weight dry film-forming resin and 0.25 to 2 parts, preferably about 1 part, by weight alumina trihydrate or other fire retardant. The coating may contain additional filler such as mineral clay and/or calcium carbonate. Suitable amounts of such filler are 0.25 to 2 parts. Ail parts are per part dry resin.

Other components that may be present in the coating include pigments, cross linking agents, viscosity modifiers and surface active agents.

The substrate can be a paper, inorganic tissue, mineral base, non-woven or woven substrate. If the coating weight is relatively low, for instance 20 to 100 g/m2 the product is suitable for domestic use and the substrate can be paper. The coating weight is usually at least 30 or 40 g/m2. For contract use the substrate can be paper but is preferably a woven or non-woven substrate and the resin coating weight is then preferably above 50, most preferably above 100 g/m2. It may be up to, for instance, 300 g/m2 or higher. The fibres from which the woven or non-woven substrate is formed may be any of the conventional fabric-forming fibres such as rayon, nylon, cotton, polyester, glass and blends thereof.

The coating is preferably formed by applying an aqueous composition comprising a latex oS the resin together with the other coating components. The composition may be applied to the substrate by any suitable method of coating for instance by screen printing, reverse roll, or knife over roller, knife over jacket or spraying.

If the coating is to be foamed the composition may be mechanically foamed before application or by the inclusion of a foaming agent that will produce a foam during dryina or cross b linking, for example an encapsulated volatile compound such as pentane or hexane.

The coating may be applied in one or more applications.

If the coating includes a foamed layer it may be preferable to apply this and then to apply non-foamed composition over the foamed layer.

After drying the coating may be heated to a higher temperature, for instance 110 to 1600 C, for a short while for instance 2 to 5 minutes. This heating will cause cross linking, if the composition is cross linkable.

This heating is often also desirable for softening the coating in order that it can be smoothed by calendering, so as to provide a better surface for printing. The temperature must not be such as to adversely affect the performance of the product.

The dry coating, optionally after cross linking and/or smoothing, may then be printed with appropriate decoration. Printing is preferably by gravure or screen but can be by flexographic or jet printing or other suitable method. The inks used for printing may be solvent based or water based inks and normally include an acrylic binder.

After drying and/or curing, an overall coating of a lacquer, water based or solvent-based, may be applied using a gravure lacquer cylinder or other suitable lacquer applicator. The coated product is then treated to dry and/or cure the lacquer and print. If the product is to be embossed this may be effected while the product is either hot or cold. Naturally the lacquer should preferably be free of haolgen or aromatic materials.

The smoke production properties of wallcoverings can be measured by ASTM E662 test (specific optical density of smoke generated by solid materials). The actual value will depend on coating weight and, at equivalent weights, the wallcoverings of the invention can give values (both in the flaming mode and non-flaming mode) that are less than 3/4, and often less than 1/2, the values obtained with vinyl wallcoverings.

The following are examples of the invention.

Example 1 A wet laid non-woven substrate (70 g/m2 polyester/rayon blend) was coated with an acrylic water based coating applied by knife over roller. The acrylic coating had a solids content of 50% and contained 1 part alumina trihydrate per 1 part dry weight of resin.

The coating was applied in two coats, a first coat of 70 g/m2 dry weight and a second coat of 130 g/m2 dry weight. Each coat was dried using an oven temperature of 1000 C. After drying the second coat the coated base was heated for 3 minutes at 1500C and faced up to give a smooth surface.

The material was then gravure printed with solvent based inks containing an acrylic binder. The printed material was lacquered with a solvent based lacquer containing an acrylic binder using a gravure lacquer roller.

Finally a texture was applied to the surface by embossing, using a matrix embossing roller.

Example 2 A woven cloth substrate (50:50 Polyester/Cotton blend - 87 g/m2) was sealed by coating with a foamed acrylic water based coating by knife over roller. The coating had a solids content of 50%, contained 1 part alumina trihydrate, per 1 part dry resin and was mechanically foamed to give a density of 0.3 gms/cc.

The foam coating was applied in one coat to give a dry weight of 70 gsm. A further unfoamed coating was applied, again by knife over roller, at a dry weight of 130 g/m2. Each coat was dried using an oven temperature of 1000C. After drying the material was heated for 3 minutes at 1500C and faced up to give a smooth surface.

The coated material was then printed, lacquered and embossed as described in Example 1 above.

Example 3 A paper substrate (120 g/m2) was treated exactly the same as Example 2 above.

Example 4 A woven cotton substrate (170 g/m2) was sealed with a foamed water based coating as in Example 2. Two further coatings of unfoamed acrylic were applied by knife over roller. Each coating was applied to give a dry weight of 200 g/m2, and dried at a temperature of 1000 C. After the final coating, the material was heated for 3 minutes at 1500C and faced up to give a smooth surface.

Example 5 The non-woven base of Example 1 was coated with an ethylene/vinyl acetate water based coating applied by knife over roller. The coating had a solids content of approximately 46% solids and contained 1 part alumina hydrate per 1 part dry resin.

The coating was applied in two coats each of 150 gsm dry weight. Each coat was dried at a temperature of 1000C. After drying the second coat the coated base was heated for 3 minutes at 1500C and faced up to give a smooth surface.

The product was then printed, lacquered and finished as described in Example 1.

Example 6 A mineral fibre base (150gsm) was coated with an acrylic water-based coating applied by a reverse roll coater. The acrylic coating had a solids content of 67t and contained 1 part of alumina hydrate per 1 part dry resin. The coating was applied in one coat at 150gsm dry weight and was dried at 100do. This was then heated to 1500C for one minute before being printed, lacquered and embossed as described in Example 1 above.

Claims

1. A decorative wallcovering that is substantially free of halogen and that comprises a coated substrate in which the coating is formed of a composition that is substantially free of halogen, has a dry weight of at least 20g/m2 and comprises a fire retardant is that is substantially free of halogen and a film-forming resin that is substantially free of halogen.

2. A wallcovering according to claim 1 in which the resin of the composition is selected from acrylic resins and vinyl acetate resins.

3. A wallcovering according to claim 1 in which the resin is selected from ethylene vinyl acetate, vinyl acetate/butyl acrylate, and ethyl acrylate/butyl acrylate resins.

4. A wallcovering according to any preceding claim in which the resin is applied from a latex having a film-forming temperature below 1500C.

5. A wallcovering according to claim 4 in which the film-forming temperature is below 1000C.

6. A wallcovering according to any preceding claim in which the fire retardant comprises an inorganic hydrate.

7. A wallcovering according to any preceding claim in which the fire retardant comprises alumina trihydrate.

8. A wallcovering according to any preceding claim in which the coating comprises 1 part dry weight film-forming resin, 0.25 to 2 parts retardant and 0.25 to 2 parts filler.

9. A wallcovering according to any preceding claim substantially free of aromatic compounds.

10. A wallcovering according to any preceding claim in which the weight of the coating is 20 to 300g/m2.

11. A wallcovering according to any preceding claim in which the weight of the coating is 100 to 300g/m2.

12. A wallcovering according to any preceding claim in which there is decoration printed on the coating.

13. A wallcovering according to any preceding claim in which the coating comprises a foamed layer.

14. A method of making a wallcovering according to any preceding claim comprising applying to the substrate an aqeuous composition comprising a latex of th'e resin, drying the coating and heating the coating at 110 to 1600C.

15. A process according to claim 14 in which the resin is cross linkable and is cross linked during the heating.