AU613785B2

AU613785B2 - A staining compound

Info

Publication number: AU613785B2
Application number: AU40076/89A
Authority: AU
Inventors: Michael Manassa
Original assignee: SCAN INTERNATIONAL Pty Ltd
Current assignee: SCAN INTERNATIONAL Pty Ltd
Priority date: 1988-08-19
Filing date: 1989-08-21
Publication date: 1991-08-08
Anticipated expiration: 2009-08-21
Also published as: AU4007689A

Description

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APPLICANT:

NUMBER:

FILING DATE:

AUSTRALIA

PATENT ACT 1952 COMPLETE SPECIFICATION 0000 040 0 0, 0000 0 00 4 Complete specification of the invention entitled: A STAINING COMPOUND Ko 7 0c This invention is described in the following statement: ~g~Arn~

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I

The present invention relates to stains for wood and cork surfaces.

Two basic types of stain have been available for wood and cork. Stains based on aqueous acrylic emulsions have been available for some time. However these stains provided an opaque film having a flat finish through which the surface of the wood or cork, to which it was applied, was not visible. If one wished to coat a wooden or cork surface with a clear stain through which the surface was visible then one had to use a solvent based system. Polyurethanes dissolved in a suitable 9 -2.

solvent were normally used in this second type of stain.

This second type of stain also had the advantage of providing the surface with a glossy finish.

Environmental concerns have made the widespread use of solvent based systems undesirable. The solvents used were toxic and locations in which such stains were used had to be well ventilated. Furthermore account had to be taken of the flammability of the solvents when using the stains. However, up until now, all attempts to provide a water based system having a clear finish have failed in particular to solve the problem of the stain once applied being discoloured by water soluble components leached out of the surface to which they were applied. This problem has been particularly evident with cork surfaces. The present invention provides a water based stain which overcomes these problems whilst still retaining the benefits of the solvent based system.

Accordingly the present invention provides a water based stain for wood and cork comprising: an emulsion in water of an acrylic polymer adapted to form a film when applied to a surface; a dispersion in water of an aliphatic polyurethane; a talc; a finely divided zinc oxide powder; and a water based colouring agent, wherein the components of the stain are present in such proportions that when the stain is applied to a surface made of wood or cork, a tough clear coloured film is formed through which the characteristics of the surface remain clearly discernible.

Acrylic emulsions that have been found useful in the performance of this invention are those that have been adapted for use as sealers and which are compatible with water soluble dyes such. as the Aquacet series made by Ciba and the Sandolan series made by Sandoz.

3 Preferably the emulsion has a solids content of about 32%, a slightly alkaline pH, a maximum viscosity at 25 0

°C

of 500 mPa's, a minimum film forming temperature of 0 0

C.

and a coalescent content of 12%. A particularly preferred acrylic emulsion is Neocryl A614 made by Polyvinyl Chemie and sold in Australia by Abbey Chemical Agencies Pty. Ltd.

Aqueous dispersions of aliphatic polyurethane resins that have been found useful in formulating the stain of this invention are those manufactured by Polyvinyl Chemie and sold under the trade name NeoRez especially the R960 series and in particular NeoRez a ep R-961. NeoRez R961 is a white translucent dispersion in water of a one-component aliphatic polyurethane. It has 0o 15 a solids content of abut 33%, a slightly alkaline pH, a viscosity at 25°C of 100-500 cps, an acid number of 30, a 0000 minimum film forming temperature of less than 0 C, a oo0a S water content of 48% and a coalescent content of 17%.

The coalescent used is n-methylpyrrolidone.

The water based colouring agent may be one selected from the Aquacet series made by Ciba or one from o004 0 4 4 0 o the Sandolan series made by Sandoz. Alternatively any colouring agent normally used for colouring water based paints may be used.

I 25 The proportion of acrylic emulsion to i polyurethane dispersion is crucial but varies from one 'I combination to another. In the case of, NeoRez R961 and Neocryl A614, a 40:60 ratio is preferred. Substantial departures from this ratio, result in formulations that i| 30 exhibit undesirable characteristics. As the acrylic content increases the formulation won't form a film. As the polyurethane content increases the formulation won't flow and is difficult to apply.

The talc and zinc oxide appear to play a vital role in dispersing the colouring agents throughout the film formed by application of the formulations. If too 4 little zinc oxide is used the film formed is opaque. On Sthe other hand if too much zinc oxide is used the formulation can become too viscous. The viscosity and body of the formulation is controlled to some extent by the content of talc. The viscosity of the formulations may be reduced by the addition of water.

The stains of the present invention obviate the need for sanding each coat prior to the addition of another coat. Furthermore worn areas can be patched up by an application of the stain in those areas. The stains of the present invention also have a much lower propensity to yellow and hence have a longer life than conventional solvent based systems.

A preferred embodiment of the invention is oO 15 described in the example below.

c ,o Example 0Pour 6 litres of Neocryl A614 into a clean empty 50 litre open topped drum. Add 5 litres of water while stirring with a portable mechanical stirrer. Add 4 litres of NeoRez 961 while continuing to stir. o 0 litres of a talc known as TS100 available from Robert 3ryce is measured into a measuring cylinder and slowly stirred into the mixture. Similarly 7.5 litres of a fine zinc oxide powder is added to the mixture and finally ml of an aqueous solution of a suitable colouring agent is added.

The resultant stain when applied to a cork surface dried in 30 to 60 minutes leaving a tough durable coating of excellent clarity through which the surface of the cork can be clearly seen albeit with a different colour from its natural state.

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Claims

2. A stain according to Claim i, wherein the l acrylic polymer is one adapted for use as a seal for wood or cork and which, when in an aqueous emulsion, is compatible with water soluble dyes.
3. A stain according to either Claim 1 or Claim 2, wherein the emulsion has a solids content of about 32%, a Sslightly alkaline pH, a maximum viscosity at 25 C of 500 a. mPa's, a minimum film forming temperature of 0 0 C and a coalescent content of 12%.
4. A water based stain according to any one of the preceding claims, wherein the dispersion in water of the aliphatic polyurethane has a solids content of about 33%, a slightly alkaline pH, a viscosity at 25 C of 100-500 cps, an acid number of 30, a minimum film forming temperature of less than 0 0 C, a water content of 48% and a coalescent content of 17%. The stain according to Claim 4, wherein the coalescent is n-methylpyrrolidone. r -6- iof forming a film and is capable of being readily applied. i 7. A water based stain according to any one of the preceding claims, wherein the proportion of zinc oxide in the stain is such that the film formed by the stain is clear and the stain is capable of being applied.
8. A stain substantially as hereinbefore describe' with reference to the accompanying example. oa.o "DATED this 21st day of August, 1989 -MICHAEL MANASSA o 'By his Patent Attorneys GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia 4 s a