GB2267848A

GB2267848A - Wall covering

Info

Publication number: GB2267848A
Application number: GB9212981A
Authority: GB
Inventors: Peter John Herbert
Original assignee: ICP COATINGS Ltd
Current assignee: ICP COATINGS Ltd
Priority date: 1992-06-19
Filing date: 1992-06-19
Publication date: 1993-12-22
Also published as: GB9212981D0

Abstract

A wall covering comprises a substrate, a deformable plastics coating laminated to one major surface of the substrate, and a layer of a pressure-sensitive adhesive bonded to the other major surface of the substrate. The adhesive is selected to form a permanent bond with the substrate and a removeable bond with the plastics coating.

Description

WALL COVERING The present invention relates to a wall covering, more particularly to a wall covering which can be self-wound and which is self-adhesive.

Conventional wall coverings such as wallpaper have hitherto been made self-adhesive by coating a layer of paper with a layer of dry adhesive. This type of wallpaper has been termed "ready pasted" wallpaper. Such wallpaper can be self-wound and sold in rolls. When required for use, the wallpaper has to be soaked in a trough of water so as to wet the dry adhesive. From the viewpoint of the user of the wallpaper, this can be a troublesome exercise.

Another conventional wall covering is a plastic film coated with a permanently tacky adhesive. This can be sold in a rolled-up form and comprises an outer layer of, for example, polyvinyl chloride (PVC) and an inner adhesive layer. In order to prevent the free surface of the inner adhesive layer from sticking to the free surface of the outer PVC layer when stored in rolled-up form, it is necessary to provide a "release liner" positioned between the free surfaces of the two layers. Thus, when such border material is rolled-up, the release liner prevents unwanted adhesion of the adhesive layer to the PVC layer. This material is relatively expensive to manufacture because of the need to provide the additional liner layer Self-wound self-adhesive products are known outside the field of wall coverings. Conventional adhesive tapes are made as rolls of self-wound self-adhesive products.For successful operation, the strength of any adhesive bond between the adhesive and the uncoated side of the tape in the roll must be lower than the internal strength of the tape substrate itself. This is accomplished in one of two construction types. In the first construction, the tape substrate is produced with a very high internal strength.

Packaging tapes can be made of polypropylene film which has a very high resistance to internal delamination. In such tapes, one major surface of the polypropylene film is treated, for example, with a corona discharge to ensure that the adhesive bonds to this surface of the film and does not bond strongly to the untreated surface of the film in the roll. In another construction, the tape substrate has a low internal strength, for example where the substrate is paper. In tapes of low internal strength, one major surface of the substrate is treated with a release agent to prevent the adhesive adhering to that major surface in the roll.

In order to produce a useful self-wound, self-adhesive wall covering, it is not possible to adopt the features used in the self-wound self-adhesive tape construction.

Polypropylene is unsuitable as a constituent of wall coverings, primarily because it is too rigid. Wall coverings need to be capable of being embossed so as to produce a decorative surface. Moreover, wall coverings need to conform to wall surfaces which are generally relatively uneven. High strength materials such as polypropylene are too rigid to fulfil these requirements.

If wall coverings are treated with a release agent in the same way as the low internal strength tapes, no adhesion is possible between the adhesive and the exterior surface of the covering in position on the wall. In use, it is essential for wall coverings to be capable of being overlapped. Such overlapping requires that the exterior surface of the wall covering be bonded to the interior adhesive layer. This could not be achieved if the exterior surface had been treated with the release agent.

The present invention aims to overcome the disadvantages hitherto encountered by providing a wall covering capable of being self-wound and self-adhesive.

The present invention provides a wall covering comprising a substrate, a deformable plastics coating laminated to one major surface of the substrate, and a layer of a pressure-sensitive adhesive bonded to the other major surface of the substrate. The adhesive is selected to form a permanent bond with the substrate and a removeable bond with the plastics coating.

When the wall covering is self-wound, the adhesive forms a reversible bond with the plastics coating which permits the wall covering to be unwound so as to free the adhesive layer for bonding to the surface of the wall. Thus, no extra expense is incurred in production of the wall covering to incorporate an additional release liner.

Moreover, the wall covering is ready to use and needs no further treatment before use, such as soaking in water.

By a permanent bond is meant one which is stronger than the tear strength of the substrate. By a removable bond is meant one which is semi-permanent or reversible with a non-porous or sealed surface such as the surface of the plastics coating.

Typically, the substrate consists of a fibrous material such as paper or a non-woven fabric or tissue. Whilst any substrate commonly used in the wall covering field may be used in the present invention, paper is a preferred substrate.

The deformable plastics coating must be able to conform with common wall surfaces which are often relatively uneven. The plastics coating must also be sufficiently deformable to allow conventional patterning to be embossed on its surface. Preferably, the deformable plastics coating comprises a polyvinyl chloride coating which is commonly referred to in the field of wall coverings as a "vinyl" coating. Conventionally this type of vinyl wallcovering is made by coating a PVC plastisol onto a paper substrate and this process is well known in the wallcovering industry. A plastisol is a suspension ofv a PVC polymer in a suitable plasticizer. This produces a spreadable dough which can be coated by a conventional knife coating process onto, for example, paper.The plasticizer is then incorporated into the PVC by heating the plastisol and so forming a flexible plasticised film.

In many instances it is desirable to print the plastics coating with inks and so the plastics coating should be able to accept such inks, if necessary.

Typically, a polyvinyl chloride coating is applied at 90 grams per square metre on a paper substrate of 80 grams per square metre. The polyvinyl chloride may be applied to the paper in the form of a plastisol, or an organosol (which is a plastisol containing a volatile organic solvent).

Preferably, the adhesive formulation is as follows: Component Parts bv weight a) 50% dispersion of a polymer 20-80 of butyl acrylate b) 50% dispersion of a copolymer 80-20 of butyl acrylate, 2-ethyl hexyl acrylate containing a comonomer component for hardening the adhesive ~~~~~ 100 Total c) Plasticizer 10-30 d) Surfactant up to 3 e) Base To give pH 8-9 Increasing the level of component (a) in the formulation will increase the level of adhesion and conversly increasing the level of component (b) will reduce the level of adhesion.

The level of plasticizer present will also change the adhesion properties of the formulation. Increasing the level of plasticizer will reduce the level of adhesion and conversly decreasing this component will increase adhesion. Component (d) is preferably added to the plasticizer prior to this blend being added to the combined acrylic dispersions. This component (d) is added to ensure satisfactory dispersion of the plasticizer into the acrylic dispersion.

In order to achieve the required balance of properties in the adhesive, component (b) incorporates a comonomer component for hardening the adhesive but which still allows self-adhesion. Useful comonomers are those with a relatively high glass transition temperature such as one or more of the following: acrylic acid, acrylonitrile, methacrylate, ethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, methacrylic acid, methyl methacrylate, butyl methacrylate, vinyl acetate, and styrene. The comonomer component is preferably acrylic acid and acrylonitrile.

Preferably, the plasticizer is an alkyl phthalate.

Dialkyl phthalates may be used as the plasticizer, such as dioctyl phthalate and dibutyl phthalate.

Preferably the surfactant is an alkylphenol ethoxylate with a cloud point in water of between 500C to 95 0C.

Any suitable base may be used to adjust the pH although the preferred base is ammonia.

Typically, the wall coverings are coated with adhesive to a level of 25 to 35 grams per square metre, preferably 30 grams per square metre. The adhesive is applied to the wallcovering with conventional coating equipment which is well known in the self adhesive coating industry.

Where the plastics coating of the wall covering is printed with inks, sometimes residual solvent from the inks remains on the plastic coating. In order to prevent any interference of this contaminating solvent with the adhesion properties of the adhesive, it is preferable to pre-treat the wall covering to render it substantially free of the contaminating solvent. Typically, the wall covering is pretreated at 1000C for at least 3 minutes so as to render it free of solvent odour. This pretreatment is conveniently effected in a hot air drying oven.

The present invention will now be described in further detail by way of example only with reference to the following Examples.

Five samples of wallpaper were produced in conventional manner having a paper substrate at 80 grams per square metres coated with a polyvinyl chloride coating at 90 grams per square metre. Each wallpaper was printed with a different pattern and pretreated to reduce any contaminating solvent to an acceptable level. All of the wallpapers were coated at 30 grams per square metre with two adhesives: ICP 52 and ICP 73.The formulation for these adhesives is as follows: Component Parts by weight ICP 52 ICP 73 a) 50% dispersion of a polymer 55 65 of butyl acrylate b 50% dispersion of a copolymer 45 35 of butyl acrylate, 2-ethyl hexyl acrylate containing acrylic acid and acrylonitrile c) Dioctyl phthalate 12.0 14.2 d) Alkylphenol ethoxylate* 1.2 1.4 e) Ammonia To give pH 8-9 *With a cloud point in water of between 50 0C and 95 0C Each of the samples was tested for peel adhesion to stainless steel after 5 minutes and after 24 hours. The samples were also tested for their adhesion to self after 24 hours. The tests were performed as described in British Standard BS 3887:1991 (Pressure Sensitive Adhesive Closing and Sealing Tapes).

The results of the test are detailed in Table 1 below.

Table 1 Evaluation of various wallpaper patterns with adhesives ICP 52 and ICP 73 Wallpapers A B C D E 5 mins peel to steel ICP52 1.55 2.21 1.60 1.72 1.71 ICP73 1.48 1.48 1.34 1.15 1.55 24 hr peel to steel ICP52 2.04 3.51 2.42 1.89 2.09 ICP73 2.53 2.89 2.85 1.61 2.49 24 hr peel to self ICP52 0.36 1.68 0.81 3.44 1.42 ICP73 0.30 0.89 0.59 2.40 0.98 Tested in accordance with BS 3887:1991. The figures refer to peel strengths and are given in Newtons per 25 mm width.

Claims

CLAIMS:

1. A wall covering comprising a substrate, a deformable plastics coating laminated to one major surface of the substrate, and a layer of a pressure-sensitive adhesive bonded to the other major surface of the substrate, wherein the adhesive is selected to form a permanent bond with the substrate and a removable bond with the plastics coating so as to permit the wall covering to be self wound and self adhesive.

2. A wall covering according to claim 1, wherein the substrate comprises paper.

3. A wall covering according to claim 1 or claim 2, wherein the deformable plastics coating comprises a polyvinyl chloride coating.

4. A wall covering according to any one of claims 1 to 3, wherein the adhesive is an acrylic based pressure sensitive adhesive.

5. A wall covering according to claim 4, wherein the adhesive consists of: a) 20 to 80 parts by weight of a 50% dispersion of a polymer of butyl acetate; b) 80 to 20 parts by weight at a 50% dispersion of a copolymer of butyl acetate and 2-ethyl hexyl acrylate containing a comonomer component for hardening the adhesive; c) 10 to 30 parts by weight of a plasticizer; d) up to 3 parts by weight of a surfactant; and e) base to give a pH in the range 8.0 to 9.0; in which components a) and b) together give a total of 100 parts by weight.

6. A wall covering according to claim 5, wherein the comonomer component for hardening the adhesive is at least one of the following: acrylic acid, acrylonitrile, methacrylate, ethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, methacrylic acid, methyl methacrylate, butyl methacrylate, vinyl acetate, and styrene.

7. A wall covering according to claim 6, wherein the component is acrylic acid and acrylonitrile.

8. A wall covering according to any one of claims 5 to 7, wherein the surfactant is an alkylphenol ethoxylate.

9. A wall covering according to claim 8, wherein the alkylphenol ethoxylate is present at approximately 1 to 2 parts by weight.

10. A wall covering according to any one of claims 5 to 8, wherein the plasticizer is an alkyl phthalate.

11. A wall covering according to claim 10, wherein the alkyl phthalate is dioctyl phthalate present at approximately 12 to 15 parts by weight.

12. A wall covering according to any one of claims 5 to 11, wherein component (a) is present at approximately 55 to 65 parts by weight.

13. A wall covering according to any one of the preceding claims, wherein the deformable plastics coating has been pretreated to be substantially free of contaminating solvent.

14. A wall covering substantially as hereinbefore described, with reference to any one of the Examples.