GB2234249A - Coating compositions - Google Patents

Abstract

Paint or varnish for producing gleamy decorative coatings (1) comprises organic binder (3) and 10 to 50 vol % of solid lenticular particles (2) (e.g. spheres) having diameters of from 10 to 90 mu m and being able to receive light through most and preferably all of their surface. Gleamy decorative coatings are produced by subjecting the coating while still wet to differential pressures across its surface. <IMAGE>

Description

PAINT OR VARNISH FOR PRODUCING GLEAMY DECORATIVE 2^, COATINGS This invention relates to a paint or varnish (including varnishes intended for application to dried coats of paint even though they are sometimes called "glazes") which paint or varnish dries under ambient conditions to produce a gleamy decorative dried coating. The invention also relates to an optionally interrupted gleamy decorative dried coating obtainable by use of the paint or varnish and to a technique for applying the paint or varnish to produce an accentuated gleamy decorative coating by interrupting the coating.

For some years now, modern interior decorators have been searching for paints and varnishes which dry to give decorative coatings showing novel visual appearances. For example, British patent specification GB 2171413A discloses paints containing rigid spheroidal opaque organic polymeric beads having a tone or colour different to that of the rest of the paint when dry so that when the paint is applied to a wall or ceiling and allowed to dry, the paint produces a decorative coating which shows variations in tone or colour. However because the beads are opaque, the dried coatings have no ability to create highlights and as a result the coatings do not have a gleamy appearance.

United States patent specification US 4 263 345 discloses coating compositions for making clothing reflective at night. The compositions comprise for example an aqueous emulsion of acrylic copolymer containing glass microspheres which have been metallised over a hemispherical portion of their surface to make them reflective. However, the coated garments appear non-reflective in daylight and the metallisation prevents the tone and colour of the coated substrate from contributing to the visual effect produced by the light which has been reflected through the microspheres.

Reflective road marking compositions have been proposed which comprise large (i.e. having diameters of lmm or above) glass spheres dispersed in chlorinated rubber binder material and which need to be applied to road surfaces in very thick (i.e. 75 to 250m) coatings. lpm is 10 6m. Such road marking compositions are quite unsuitable for decorating walls and ceilings.

An object of this invention is to provide a paint or varnish suitable for application to walls or ceilings and which dries under ambient conditions to produce a decorative coating which can gleam in daylight or ordinary room lighting.

Accordingly this invention provides a paint or varnish which dries under ambient conditions to produce a gleamy decorative dried coating and which comprises an essentially transparent organic binder material which when the paint or varnish dries serves to bind together other ingredients of the paint or varnish and wherein the paint or varnish also comprises from 5 to 40 (preferably 10 to 30) wt % of solid transparent lenticular (preferably, spheroidal and most preferably spherical) particles having a) a maximum diameter no greater than 150m (and preferably no greater than 90cm) b) a minimum diameter no less than 10pm (and preferably no less than 20pom) and desirably c) over 50% (preferably over 808 and most preferably over 98%) of the surface area of each particle able to allow light coming from beyond the surface to enter the particle.

This invention also provides a gleamy decorative dried coating comprising an optionally interrupted film of dried binder material wherein the film is up to 70m thick and contains bound therein solid transparent lenticular particles as defined above and which cause the dried coating to present curved surfaces to light incident from outside the coating.

Preferably from 10 to 50% of the maximum diameter of a particle should protrude from the top surface of the binder material located to the side of that particle.

Preferably the lenticular particles should have a refractive index of 1.4 to 1.88 and preferably the refractive index should be similar to or a little greater than that of the dried binder material.

Usually the dried binder material will have a refractive index of from 1.4 to 1.6. The particles preferably have smooth surfaces and may be made from organic materials or from inorganic materials such as glass. Both crown or flint glasses may be used.

A wide variety of binder materials may be used chosen from those well known to the paint trade.

These are reviewed in the third edition of the book "Introduction to Paint Chemistry and Principles of Paint Technology" by G P A Turner published in 1988 by Chapman and Hall of London, see especially Chapters 11 and 12 the contents of which are herein incorporated by reference. Preferred examples of binder materials of the type described in Chapter 11 ibid include homopolymers and copolymers of vinyl esters and ethers, lower alkyl acrylates and methacrylates, lower olefins, halogenated vinyl monomers; and styrene/butadiene copolymers. Typical monomers include vinyl acetate, vinyl propionate, vinyl esters of saturated tertiary moncarboxylic acids (for example acids commercially available from Shell Chemicals under the Registered Trade Mark "Versatic" acids), (meth)acrylic acid, methyl methacrylate, ethyl acrylate, 2-ethyl hexyl acrylate, vinyl chloride and vinylidene chloride.Preferred binder materials of the type described in Chapter 12 ibid include organic materials which undergo (usually autoxidised) crosslinking reactions as the paint dries to produce for example alkyd resins, polyesters or polyurethanes. The dried binder material should be largely transparent and preferably at least sufficiently transparent to allow over 30% of light entering the dried coating to travel through the coating, be reflected and travel back through the coating. This degree of transparency not only ensures a gleamy appearance but also allows the tone and colour of a substrate to which the coating is applied to contribute to the appearance of the coating.

It has been found that the gleam is more striking if the paint contains a particulate opacifier having a number average maximum diameter which does not exceed about 20% (preferably about 15%) of the maximum diameter of the lenticular particles. Preferably the opacifier particles will have a maximum diameter of from 1 to 15cm. Possible opacifiers include titanium dioxide or organic vesiculated particles such as those available commercially from Rohm and Haas under the trade name "Ropaque". However the preferred vesiculated particles are those available from Imperial Chemical Industries PLC under the trade name "Spindrift". A fuller description of "Spindrift" is given in United States patent specification US 4 321 332 (the contents of which are herein incorporated by reference).

The paints and varnishes according to this invention may also contain other conventional ingredients such as anti-skin, anti-foam and anti-freeze agents and the paints may contain pigments, dyes, tinters, extenders and thickeners provided the paints remain adequately transparent.

The invention also provides a technique for producing an accentuated gleamy decorative coating wherein the technique comprises a) applying a coating of the paint or varnish according to this invention to a wall or ceiling and before the coating has become dry b) subjecting different portions of the still wet coating to different pressures whereby the paint or varnish is at least partially displaced from a portion subjected to a higher pressure to a portion subjected to a lower pressure so interrupting the homogeneity of the coating. It is found that the displacement causes lenticular particles to bunch creating zones of higher concentrations of particles and zones of lower concentrations of particles. The zones of higher concentration have accentuated gleam, often amounting to a sparkle which creates a more striking appearance.Accordingly this invention also provides an accentuated gleamy decorative dried coating comprising zones of higher and lower concentrations of lenticular particles.

Portions of wet coating may be subjected to differential pressure by manual techniques such as brushing, rag-rolling or rag-dabbing. Alternatively a tool may be traversed across the surface of the wet coating. A suitable tool may comprise a roller having its cylindrical surface modified to enable the roller to exert different pressures when different portions of its cylindrical surface contact the coating. For example the cylindrical surface may be modified by the provision of a plurality of flexible flaps which strike the wet coating with a repeated beating action as the roller traverses the coating.

Such a roller is more fully described in British patent specification GB 2207733A the contents of which are herein incorporated by reference.

The application of differential pressure also usually interrupts the thickness of the coating because the coating tends to be thickest in portions which have been subjected to lesser pressures. If very high pressures are applied, there may be zones from which the coating has been totally displaced leaving a zero thickness. Accordingly the invention also provides a coating comprising zones in which the coating is thicker than elsewhere.

Preferably the paint or varnish of this invention is applied to a wall or ceiling which has already been decorated (preferably painted using a coloured basecoat) whereupon the tone and colour of the decoration contribute to the overall appearance of the wall or ceiling.

The invention is further illustrated by the following descriptions which refer to the drawings of which Figure 1 shows in diagrammatic section a gleamy decorative dried coating according to this invention, Figure 2 shows in diagrammatic section an accentuated gleamy decorative dried coating according to this invention and Figure 3 is a diagram on a larger scale postulating how paints or varnishes of this invention are believed to create a gleamy effect.

Figure 1 shows a gleamy decorative dried coating 1 comprising lenticular glass microspheres 2 bound in a transparent dried organic binder material 3 applied to a wall 4. About 40% of the diameter of microspheres 2 protrudes from the top surface la of the dried binder material located to the sides of the microspheres 2 with the result that coating 1 presents a series of curved surfaces lb through which light incident from outside the coating can pass.

Glass microspheres 2 have virtually the same refractive index as binder material 3.

Figure 2 shows an accentuated gleamy decorative dried coating 11 comprising glass microspheres 12 bound in a transparent dried organic binder material 13 applied to a dried coat 15 of coloured paint which in turn is applied to a wall 14. Small particles 16 of opacifier are located between microspheres 12 and coat 15 of coloured paint. Again microspheres 12 protrude above the dried binder material located to the side of them so that coating 11 presents a series of curved surfaces lia through which light incident from outside the coating can pass.

Coating 11 is interrupted both in homogeneity and thickness. Homogeneity is interrupted by the presence of zones 17 of high concentrations of microspheres 12 and opacifier particles 16, zones 17a of high concentrations of opacifier alone and zones 17b which contain no microspheres 12 and often no opacifier. Thickness is interrupted by thicker zones of coating 17 or 17a, thinner zones 17b and zones 17c. In zones 17c coating 11 has zero thickness because all the coating has been displaced to zones of greater thickness.

Figure 3 illustrates one way in which it may be that paint or varnishes according to this invention create a gleamy effect. Daylight 31 from a distant source 32 enters curved surface lb of thin retaining layer 3a of dried binder material 3 and passes into microsphere 2 through front portion 2a of its surface. For the purpose of showing the path of the light more clearly, microsphere 2 is shown spaced from wall 4 although in practice most microspheres will touch the substrate (e.g. wall 4) onto which the coating has been applied. Light 31 crosses microsphere 2 leaving it through portion 2b of its surface and then strikes wall 4. Surface 4a of wall 4 is not mirror-like and so light incident upon it is reflected diffusely in all directions. However much of this reflected light re-enters microsphere 2 through portion 2c of its surface and leaves through front portion 2a.Finally light 31 leaves curved surface lb of thin layer 3a and is seen by the eye 33 of an observer. On passing through microsphere 2 the first time, light 31 is partially focused with the result that it establishes a highlight at 34 on wall 4. It is this highlight which creates the gleamy effect because it appears brighter than its immediate surroundings. On passing back through microsphere 2, light 31 diverges so that the highlight at 34 appears magnified. Also, because light 31 is reflected from surface 4a of wall 4, its appearance to the observer is influenced by the tone and colour of surface 4a.

This invention is further illustrated by the following Examples.

EXAMPLE 1 This example illustrates the use of a paint according to this invention in which the binder material is particulate film-forming copolymer present as an aqueous latex. When the paint dries, water evaporates and particles of the copolymer coalesces to form a transparent film in which the lenticular particles are bound.

A paint was made by stirring together the following ingredients: Ingredients Wt in g Water 18.4 Propylene glycol 13 *Copolymer latex containing 50 wt% water 31 *Glass microspheres 19 Aqueous dispersion of "Spindrift" 571 521 opacifier particles containing 74wt % water 16 *Thickener 1.4 Non-ionic surfactant 0.8 Antifoaming agent 0.2 Ammonia 0.2 100g * The copolymer comprised about equal amounts of methyl methacrylate and 2-ethyl hexyl acrylate and also acrylic acid to an amount not exceeding 3wt% of the copolymer.

* The glass microspheres had diameters in the range 50 to 80 and were available from Filtec Ltd.

* The thickener was predominantly a urethane material available from Rohm and Haas as "Primal" RM8.

The paint was applied using a conventional roller to a substrate covered with a dried coat of a conventional coloured paint. Whilst the paint was still wet, its surface was traversed by a modified roller of the type described in GB 2 207 733A. An interrupted coating was obtained which dried to produce an accentuated gleamy decorative coating which exhibited sparkle when observed in sunlight coming from above and behind the observer. The thickness of the dried coating to the sides of the microspheres varied from 4 to 65m and the thickness in the presence of a microsphere reached 90m or multiples of 90pm in isolated instances where two or more microspheres were arranged one on top of another.

EXAMPLE 2 This Example illustrates the use of a paint according to this invention in which the binder material consists of polyamide modified and urethane modified precursors comprising soya bean oil, pentaerythritol and phthalic anhydride which crosslink by oxidation to produce a dried binder material.

A paint was made by stirring together the following ingredients: Ingredients Wt in g Polyamide modified precursor 37 Urethane modified precursor 27 Glass microspheres (as used in Example 1) 22 Dried "Spindrift" 571521 opacifier particles 5 White spirit 7.7 Drying agent 1.1 Anti-skinning agent 0.2 100.0 The paint was applied to a coated substrate as in Example 1. After traversing with the modified roller, the paint dried to produce an accentuated gleamy decorative coating.

Claims (13)

1. A paint or varnish which dries under ambient conditions to produce a gleamy decorative dried coating (1) and which comprises an essentially transparent organic binder material (3) which when the paint or varnish dried serves to bind together other ingredients of the paint or varnish and wherein the paint or varnish also comprises from 10 to 50 vol % of solid transparent lenticular particles (2) having a) a maximum diameter no greater than 90m b) a minimum diameter no less than 10pm and c) over 50% of the surface area of each particle able to allow light coming from beyond the surface to enter the particle.

2. A paint or varnish according to Claim 1 wherein the lenticular particles (2) are spherical.

3. A paint or varnish according to Claim 1 or Claim 2 wherein the lenticular particles (2) have a refractive index of from 1.4 to 1.88.

4. A paint or varnish according to any one of the preceding claims wherein the lenticular particles (2) are glass particles.

5. A paint or varnish according to any one of the preceding Claims wherein the paint or varnish contains a particulate opacifier (16) having a number average maximum particle diameter which does not exceed 20% of the maximum diameter of the lenticular particles.

6. A paint or varnish according to Claim 5 wherein the opacifier particles (16) have a number average particle size of from 1 to 15 pom.

7. A gleamy decorative dried coating (1) comprising an optionally interrupted film of dried binder material (3) wherein the film is up to 70pm thick and contains bound therein solid transparent lenticular particles (2) as defined in any one of Claims 1 to 5 and which cause the dried coating to present a curved surface la to light incident from outside the coating.

8. A coating as claimed in Claim 7 containing particles (16) of opacifier as claimed in Claim 5 or Claim 6.

9. A coating (11) as claimed in any one of Claims 7 to 9 wherein the coating comprises zones (17) of higher concentrations of lenticular particles (12) whereby the coating has an accentuated gleamy appearance.

10. A coating (11) according to claim 9 wherein the coating comprises zones (11) in which the coating is thicker than elsewhere.

11. A technique for producing an accentuated gleamy decorative coating (11) as claimed in Claim 9 or Claim 10 wherein the technique comprises a) applying a coating of the paint or varnish according to this invention to a wall or ceiling (14) and before the coating has become dry b) subjecting different portions of the still wet coating to different pressures whereby the paint or varnish is at least partially displaced from a portion (llb or llc) subjected to a higher pressure to a portion (lla) subjected to a lower pressure.

12. A technique according to Claim 11 wherein the wet coating (11) is traversed by a roller having its cylindrical surface modified to enable the roller to exert different pressures on the coating when different portions of it contact the wet coating.

13. A technique according to Claim 11 or Claim 12 wherein the wet coating is subjected to a repeated beating action.