GB2159068A

GB2159068A - Wallpaper with improved washability

Info

Publication number: GB2159068A
Application number: GB08512647A
Authority: GB
Inventors: Pentti Rissanen
Original assignee: KYRO Oy
Current assignee: KYRO Oy
Priority date: 1984-05-21
Filing date: 1985-05-20
Publication date: 1985-11-27
Also published as: GB2159068B; DE3518071A1; DE3518071C2; GB8512647D0; FR2564496A1; FR2564496B1

Abstract

The wallpaper of the invention comprises a layer of body paper covered with a pigment coating containing latex and pigments, over which an aqueous solution of the salts of di- or polyvalent metals is spread in order to reduce the proportion of latex in the pigment coating, with no adverse effect on the washability of the wallpaper.

Description

SPECIFICATION Wallpaper and a Method of Making a Wallpaper The present invention relates to a wallpaper of the type comprising a layer of body paper, over which there is a pigment coating containing latex and pigments for printing the wallpaper, using such methods as glue, silk screen, flexo and gravure printing.

Such wallpaper must withstand a certain amount of washing. The degree of washability can be tested, for example, with a Timberley WPM device and method B, using felt as the rubbing surface and 2% alkaline soap solution as the medium. A reasonable requirement is that the wallpaper sample withstands 30 strokes without any damage to the surface.

Washability can be improved by increasing the amount of latex in the pigment coating.

In this application "latex" means the so-called homo- or copolymer latexes generally used in wall coverings, e.g. polvyinyl acetate homopolymer, polyvinyl acetate-acrylate copolymer, ethylene-vinyl acetate copolymer, styrene-acrylate copolymer, all-acrylate and styrene butadiene latexes.

Practice has shown that adequate washability is achieved by adding to the pigment coating an amount of latex which is more than 25% of the weight of pigment.

Latex, however, is expensive and increases the manufacturing cost of wallpaper.

Experience also shows that whenever high percentages of latex are used, the printing techniques fail to produce a good line sharpness and an even, compact surface, because the ink tends to sparkle as a result of the deteriorated absorption ability of the pigment layer, which in turn is due to the high latex content.

Latex has poor opacity and this must be compensated for by pigments with good opacity, such as titanium oxide. Such a pigment however, is expensive.

To eliminate the above-mentioned disadvantages the object of the invention is to improve the washability of wallpaper by a means other than the addition of latex, whereby the proportion of latex in the pigment coating could be decreased.

In accordance with the invention, in order to improve washability and to reduce the content of latex, an aqueous solution of one or more inorganic or organic salts, of di- or polyvalent metals such as titanium, aluminium, calcium or magnesium, is spread over the pigment coating.

The invention is based on the unexpected observation that whenever an aqueous solution of inorganic or organic salts, of di- or polyvalent metals, is spread over the pigment coating containing latex and pigments, and located on top of the body paper, to allow printing, the washability of the wallpaper is improved considerably, and the proportion of latex in the pigment coating can be reduced to 10% or less of the amount of pigment, while washability still remains adequate. As the proportion of latex is reduced, the cost of wallpaper manufacturing is considerably lowered, because the cost of the added solution is much less than that of latex and a high-opacity pigment. Printability, too, is improved, as explained above.

In accordance with the present invention there is provided a wallpaper comprising a layer of body paper covered with a pigment coating containing latex and pigments over which an aqueous solution of one or more inorganic or organic salts of di- or polyvalent metals has been spread.

In a preferred embodiment of the invention the salt of the di- or polyvalent metal is aluminium sulphate Al2(SO4)3 XH20, where X is 14to 18.

In another preferred embodiment the salt of the di- or polyvalent metal is stannous chloride, stannic chloride, zirconium chloride, titanium chloride, zirconium sulphate, titanium citrate, aluminium chloride, aluminium sulphate, aluminium nitrate, aluminium acetate, aluminium propionate, ferric chloride, ferric nitrate, cadmium chloride, zinc chloride, zinc sulphate, barium chloride, calcium chloride, magnesium chloride, chromium sulphate, or chromic chloride.

In a third preferred embodiment, the salt of the di- or polyvalent metal is polyaluminium sulphate or polyaluminium chloride.

It is of advantage that the concentration of the aqueous solution of salt, which is spread over the pigment coating, is 0.5 to 10% by weight.

It is also of advantage that the concentration of the aqueous solution of salt, which is spread over the pigment coating, is about 5% by weight.

The invention also includes a method of making wallpaper, whereby the body paper is covered with a pigment coating containing latex and pigments for printing the wallpaper, using glue, silk screen, flexo or gravure printing, wherein it is characteristic of the invention that an aqueous solution of one or more inorganic or organic salts of a di- or polyvalent metal, such as titanium, aluminium, calcium or magnesium, is spread over the pigment coating in orderto improve washability and to reduce the consumption of latex.

Even so-called double-salts can be used, where the salt of a di- or polyvalent metal can be used together with the salt of a univalent metal. Such double salts include potash alum, cesium alum and sodium alum.

The solution can be spread, for instance, with rollers that can be used in various ways applied in paper making techniques, or by atomizing whereby air is used, or by spraying. Even impregnating, or an immersion method can be used.

Before spreading the salt solution, the pigment coating is dried until it is at least dry to touch.

In a preferred embodiment the pigment coating is dried after spreading the salt solution, until it has the moisture of printing paper.

In a preferred embodiment of the invention the salt of the di- or polyvalent metal is aluminium sulphate Al2(SO4)3 XH2O where X is 14 to 18.

In another preferred em bodiment the salt of the di- or polyvalent metal is stannous chloride, stannic chloride, zirconium chloride, titanium chloride, zirconium sulphate, titanium citrate, aluminium chloride, aluminium sulphate, aluminium nitrate, aluminium acetate, aluminium propionate, ferric chloride, ferric nitrate, cadmium chloride, zinc chloride, zinc sulphate, barium chloride, calcium chloride, magnesium chloride, chromium sulphate, or chromic chloride.

The di- or polyvalent salt can advantageously also be polyaluminium sulphate or polyaluminium chloride.

Further, in a preferred embodiment of the invention the concentration of the aqueous solution of salt is 0.5 to 10% by weight.

In another preferred embodiment the concentration of the aqueous solution of salt is about 5% by weight.

In addition to the above defined concentrations and method of spreading the solution, as well as the dryness of the pigment coating, it is necessary, for the required result, to take into account some additional factors known to the man skilled in the art, such as the temperature of the solution, the velocity of the pressweb, the absorption capacity of the paper, as well as the use of agents to speed up the absorption.

Some of these factors, for instance, the selection of the speed of the pressweb in the production process, are also affected by requirements other than better washability. Such requirements include production quantity, etc. Even qualitative aspects must be taken into consideration.

The desired result, of course, can be achieved through various combinations of the above factors.

Based on the relevant factors known at the time of spreading, the man skilled in the art is able to choose the most suitable combination based on his expertise and experience.

The invention is illustrated by the following practical example: EXAMPLE The effect of latex content and an after-treatment with 5% aluminium sulphate on washability.

The treatment was an off-machine treatment with a bar coater. Velocity 150 mlmin. Hot air drying.

7 Pigment coating Latex 25.0 15.0 10.0 Pigments Titanium oxide 23.0 16.0 12.0 Other pigments 77.0 84.0 88.0 Thickener CMC 0.3 0.6 1.0 Washability no after- 40 (C) 20 (B) 5 (A) treatment (withstands with after- 150 (D) 100 (D) 40 (C) rubbing) Timberley treatment In the example: A=washability definitely poor B=washability insufficient C=washability sufficient D=washability too good (surface too closed) The proportion of the ingredients of the pigment coating have been calculated as % dry weight of the amount of pigment.

The purpose of the thickener in the pigment coating is to improve the levelling of the coating. The most commonly used thickener is water-soluble CMC, or carboxymethyl cellulose. Another property of the thickening agent is that it tends to reduce the washability of the wallpaper.

In the example, a 5% aluminium sulphate solution was used. Laboratory tests have shown that even a 0.5% solution brings about the effect of the invention. When the strength is increased to 2% the effect is apparent. An optimal effect, considering the various factors, is achieved when the strength of the solution is about 5%. If the strength is increased further, the effect on the amount of latex increases slowly. If the strength exceeds 10%, some adverse effects are manifest, for instance the surface may become spotted.

As shown in the table, the application of the method of the invention allows a reduction in the proportion of latex in the pigment coating, from 25 to 10%, while the washability of the wallpaper remains adequate. Further, it is possible to reduce the proportion of titanium oxide in the total amount of pigment, from 23 to 12%. At the same time the cost of wallpaper manufacture is reduced and the printability of the pigment coating is improved.

Another advantage of the invention is that, due to the remarkable reduction in the proportion of latex required. A thickener can be used more liberally to allow good leveling of the pigment coating.

A lower latex content offers the following additional benefits: The pigment-coated reject, produced prior to the treatment of the invention, can be returned to the paper production process.

Cleaning of the equipment used in coating is easier.

The biological oxygen demand (BOD) of the waste water is lower.

Claims

1. Wallpaper comprising a layer of body paper, covered with a pigment coating containing latex and pigments over which an aqueous solution of one or more inorganic or organic salts of di- or polyvalent metals has been spread.

2. Wallpaper according to claim 1, wherein the di- or polyvalent metals are titanium, aluminium, calcium or magnesium.

3. Wailpaper according to claim 1, wherein the salt of the di- or polyvalent metal is aluminium sulphate Al2(SO4)3 XH2O,whereXis 14to 18.

4. Wallpaper according to claim 1, wherein the salt of the di- or polyvalent metal is stannous chloride, stannic chloride, zirconium chloride, titanium chloride, zirconium sulphate, titanium citrate, aluminium chloride, aluminium sulphate, aluminium nitrate, aluminium acetate, aluminium propionate, ferric chloride, ferric nitrate, cadmium chloride, zinc chloride, zinc sulphate, barium chloride, calcium chloride, magnesium chloride, chromium sulphate, or chromic chloride.

5. Wallpaper according to claim 1, wherein the salt of the di- or polyvalent metal is polyaluminium sulphate or polyaluminium chloride.

6. Wallpaper according to claim 1, wherein the concentration of the aqueous solution of the salt spread over the pigment coating, is 0.5 to 10% by weight.

7. Wallpaper according to claim 6, wherein the concentration of the aqueous solution of the salt is about 5% by weight.

8. Method for the production of a wallpaper according to claim 1, in which the body paper is covered with a pigment coating, containing latex and pigments wherein the pigment coating is dried until it is at least dry to touch, whereafter an aqueous solution of one or more inorganic or organic salts, of a di- or polyvalent metal is spread over the pigment coating.

9. Method according to claim 8, wherein the di- or polyvalent metals are titanium, aluminium, calcium or magnesium.

10. Method according to claim 8, wherein afterthe solution is spread, the pigment coating is dried until it has the moisture of printing paper.

11. Method according to claim 8, wherein the salt of the di- or polyvalent metal is aluminium sulphate Al2(SO4)3 XH2O, wherein X is 14to 18.

12. Method according to claim 8, wherein the salt of the di- or polyvalent metal is stannous chloride, stannic chloride, zirconium chloride, titanium chloride, zirconium sulphate, titanium citrate, aluminium chloride, aluminium sulphate, aluminium nitrate, aluminium acetate, aluminium propionate, ferric chloride, ferric nitrate, cadmium chloride, zinc chloride, zinc sulphate, barium chloride, calcium chloride, magnesium chloride, chromium sulphate, or chromic chloride.

13. Method according to claim 8, wherein the salt of the di- or polyvalent metal is polyaluminium sulphate or polyaluminium chloride.

14. Method according to claim 8, wherein the concentration of the aqueous solution of the salt is 0.5 to 10% by weight.

15. Method according to claim 14, wherein the concentration of the aqueous solution of the salt is about 5% by weight.

16. A wallpaper substantially is described herein with reference to the Example.

17. A method for the production of a wallpaper substantially as described herein with reference to the Example.

18. Awallpaperwhenever prepared by a method as claimed in any one of claims 8 to 15 or 17.