AU2005217210B2

AU2005217210B2 - Cement paint

Info

Publication number: AU2005217210B2
Application number: AU2005217210A
Authority: AU
Inventors: Richard John Bright; Philip Green
Original assignee: Freeworld Coatings Global Pty Ltd
Current assignee: Freeworld Coatings Global Pty Ltd
Priority date: 2004-01-30
Filing date: 2005-01-19
Publication date: 2009-12-10
Anticipated expiration: 2025-01-19
Also published as: AU2005217210A1; WO2005082805A1; MXPA06008539A; EP1713741A1; AP2006003718A0; JP2007534584A; CN1930101A; ZA200606925B; CA2555174A1

Description

1 CEMENT PAINT THIS INVENTION relates, broadly, to a cement paint. More particularly, it relates to a water-based cement paint; and it relates to a process for formulating the 5 water-based cement paint. According to the invention there is provided a water-based cement paint, the paint being a paint which includes, as constituents thereof, cement particles and water, the cement particles being uncured cement particles, the paint also including, 10 as a constituent, colloidally-sized particles of polymeric material capable of forming a stable colloid in water, the paint being in the form of a homogeneous blend of said constituents, the cement particles forming 5 - 40% by mass of the paint and the colloidally-sized particles forming 0.25 - 10% by mass of the paint. 15 The present invention further provides a water-based cement paint which includes, as constituents thereof, cement particles and water, wherein the paint is a paint in which the cement particles are uncured cement particles, the paint also including, as a constituent, colloidally-sized particles of polymeric material capable of forming a stable colloid in water, the paint being in the form of a homogeneous blend 20 of said constituents, the cement particles forming 5 - 40% by mass of the paint and the colloidally-sized particles forming 0.25 - 10% by mass of the paint, and the paint being in single-pack form. It is a feature of the paint of the present invention that the paint can be 25 formulated as a stable blend of its constituents, in that the blend has an extended shelf-life in the absence of air. By stable is meant not only that the blend has said extended shelf-life in the absence of air, but also that it has little or no tendency, when sealed in a paint can, to separate quickly into its constituent parts, and after mixing by stirring in a paint can prior to use, will not require further mixing for at least 60 30 minutes. By an extended shelf-life is meant that the paint, in the absence of air (for example when contained in a sealed paint can), will be usable for several months WO 2005/082805 PCT/IB2005/000125 2 or more, requiring no more than stirring to provide it with acceptable homogeneity prior to use. 5 The uncured cement particles are capable of being cured, i.e. in this context being capable in bulk of setting and hardening into a mass, by contact with water and are conveniently run-of-the-mill portland cement particles, which may be of white or grey portland cement, depending on the intended colour of the paint and on any pigment used in the paint. The ordinary particle size of uncured portland cement 10 is suitable for the present invention; and the cement particles may form 10 - 30% by mass of the paint, preferably 12 - 18% by mass of the paint. The colloidally-sized polymeric particles will have a particle size in the range 1 - 100nm and, as indicated above, will be capable of forming a stable 15 colloidal suspension in water. Suitable colloidally-sized particles may be fibrous in shape, being elongated and typically having a length at least several time their maximum transverse dimension. The colloidally-sized particles may be of a material selected from the group of polymeric materials consisting of sodium carboxymethyl cellulose, hydroxyethyl-cellulose, carboxymethyl-cellulose, polyvinyl-alcohol and 20 mixtures thereof. Preferably the colloidally-sized polymeric particles are of sodium carboxymethyl -cellulose. The polymeric particles may form 1 - 6% by mass of the paint, preferably 1.5 - 3% by mass of the paint. In a particular embodiment of the invention, the cement particles may 25 be run-of-the-mill portland cement particles, the cement particles forming 10 - 30% by WO 2005/082805 PCT/IB2005/000125 3 mass of the paint and the colloidally-sized particles forming 1 - 6% by mass of the paint. In a more preferred embodiment they form respectively 12 - 18% and 1.5 3% by mass. As indicated above, the cement particles may be grey portland cement 5 particles, or, instead, the cement particles may be white portland cement particles. Without being bound by theory, the Applicant believes that the colloidally-sized particles act by adhering in the paint blend to the surfaces of the cement particles, to form a sufficiently continuous coating thereon to protect the 10 cement particles from water in the blend and to resist or prevent premature or so called in-can curing of the cement in the blend. Too low a proportion of the polymeric particles is expected to result in premature or in-can curing of the cement, while too high a proportion can adversely affect early water resistance of the paint, when it has been applied to provide a painted layer on a substrate, and can also adversely affect 15 curing of the cement in the layer on the substrate. Routine experimentation will thus be required to determine, as with the cement proportions, acceptable or optimum proportions of the polymeric particles in the paint. As indicated above, the particles may be fibrous in shape, i.e. they may 20 have a shape which resembles that of fibres, so that they are indeed in the form of fibres; and a particularly preferred embodiment the polymeric material is sodium carboxymethyl cellulose. The paint may include a particulate elastomer. In particular, the 25 elastomer may be capable of curing on exposure to the atmosphere when forming WO 2005/082805 PCT/IB2005/000125 4 part of a paint layer painted on a substrate, to provide the paint layer with early or short-term film strength, desirable flexibility and sheen, durability and ease of application. The elastomer is desirably also be capable of providing, when cured, 5 resistance to water penetration through the layer into the substrate, the resistance lasting at least until the curing of the cement in the paint reaches a sufficient stage to take over from the elastomer in providing the paint layer with these properties on a long-term basis. Suitable elastomers may be selected from the group of elastomeric materials consisting of latex, synthetic rubber, styrene, butadiene and mixtures 10 thereof, latex being preferred. When the elastomer is a latex, it may form 5 - 60% by mass of the paint, preferably 20 - 50%. The averaqe particle size of the latex may be in the range 0.08 - 1pm, preferably 0.1 - 0.7pm, all the particles conveniently falling in these size ranges. As with the cement and colloidally-sized polymeric particles, routine experimentation can also be used to establish acceptable or 15 optimum proportions and particle sizes for the elastomer particles in the paint blend. The Applicant has successfully used both pure acrylic latexes and styrene-acrylic latexes. Accordingly, the paint may include, as a constituent thereof, an uncured 20 particulate elastomer capable of curing upon exposure to the atmosphere. The elastomer may, in particular, be a latex forming 5 - 60% by mass of the paint, and having an average particle size in the range 0.08 - 1 pm; and in a preferred version of the paint, the latex may form 20 - 50% by mass of the paint, the paint having a particle size in the range 0.1 - 0.7 pm. 25 WO 2005/082805 PCT/IB2005/000125 5 Optionally, the paint includes a thickener. The thickener may be any suitable commercially available thickener, used in appropriate or manufacturer's recommended proportions to obtain a desired degree of thickening of the paint blend. 5 The Applicant has found that, in general, hydroxyalkyl-celluloses are suitable for this purpose, examples being hydroxyethyl-cellulose, methyl hydroxyethyl- cellulose, ethyl hyd roxyethyl-cellulose, methyl hydroxypropyl-cellu lose, or the like. The thickener can desirably affect the application properties of the paint, can inhibit separation of constituents of the blend from one another in the can and settling 10 therein of solids, and can generally provide good stability and extended shelf-life. A preferred version of the paint includes 0.1 - 0.6% by mass of a hydroxyalkyl-cellulose thickener. Furthermore, the paint optionally includes a suitable pigment, to provide 15 it with a desired colour and/or opacity. While the proportion of pigment used can vary widely, a proportion of 1 - 15% by mass has been found to be suitable. Inorganic pigments such as oxides, in particular metal oxides, are preferred, as being compatible with the cement in the paint, the pigments being typically present in proportions forming 2 - 10% by mass of the paint, preferably 3 - 5%, and having an 20 average particle size of 0.05 - 100pm, preferably 1 - 20pm, all the pigment particles conveniently falling in these size ranges. It follows that the paint may include 1 15% by mass of a pigment; and in particular the pigment may be a particulate inorganic pigment forming 2 - 10% by mass of the paint and having an average particle size in the range 0.05 - 100 pm. 25 WO 2005/082805 PCT/IB2005/000125 6 The paint may include, as optional constituents, one or more suitable in-can biocides, one or more dry-film fungicides and/or algicides, one or more defoamers and one or more dispersants. Commercially available products may be 5 used for these purposes, in the usual proportions prescribed by the manufacturers. The Applicant has successfully used, as formaldehyde-releasing biocidal agents, in can biocides selected from methyl-isothiazalone, chloromethyl-isothiazalone, benzyl isothiazalone and suitable mixtures thereof. In paints. according to the present invention, the Applicant has used 0.1 - 0.3% by mass of said formaldehyde-releasing 10 agents to resist microbiological attack on the colloidally-sized polymeric particles in the can, together with 0.05 - 1%, preferably 0.5 - 1%, by mass dry-film fungicide and/or algicide, and with 0.05 - 0.5%, preferably 0.1 - 0.4%, by mass defoamer and 0.05 - 0.5% by mass dispersant. 15 As with the cement, polymeric material and elastomer, routine experimentation can be employed, both for the selection of the various said optional constituents and for selection of their proportions in the paint, bearing in mind both technical and economic considerations, for optimum or at least acceptable results. Typically, once the proportions of all the constituents have been established, water 20 will make up the balance. To formulate the paint blend the colloidally-sized polymer particles may be dispersed in water to form a colloidal suspension of the particles therein, the cement then being admixed into the colloidal suspension, followed optionally by the 25 particulate elastomer. Conveniently, any in-can biocide, fungicide/algicide and/or I:08-09-2006! E M Ub /U2 2d/ 7 defoamer used is admixed with the water or colloidal suspension prior to the cement, and any pigment, thickener and/or dispersant used is admixed with the other constituents, after addition of the elastomer to the colloidal suspension. In particular, 5 the pigment, thickener and/or dispersant may be dispersed (dissolved and/or suspended) in water before addition thereof to the blend of the other constituents. The invention accordingly extends to a process for formulating a water based cement paint as defined above, the process including the steps of: 0 suspending the colloidally-sized polymer particles in water to form a colloidal suspension; and admixing the cement particles with the colloidal suspension to form a paint which is a blend of the water, cement and colloidally-sized polymer particles. 15 The process may include the step of admixing the elastomer particles with the water to form the colloidal suspension, before the admixing of the cement particles with the suspension. The various other said optional constituents may be admixed with the 20 water, polymer particles, cement particles and elastomer particles in any desired or convenient sequence. The invention will now be described, by way of non-limiting illustrative example, with reference to the following worked Examples: 25 WO 2005/082805 PCT/IB2005/000125 8 EXAMPLE 1 In an initial trial a batch comprising 182 kg (178t) of a colloidal 5 suspension was prepared by admixing, into 160f water, 12 kg of colloidally sized cellulose fibres, 5 kg of in-can biocide, 5 kg of defoamer, and 10f of acrylic latex available under the Trade Mark "REV 6115" from Revertex Chemicals (Proprietary) Limited of 200 Lansdowne Road, Jacobs, Durban, Republic of South Africa. The cellulose fibres were those available under the 10 Trade Mark "NORILOSE 6064" from Protea Chemicals Limited of 1 Berrange Road, Wadeville, Gauteng, Republic of South Africa; the biocide was that available under the Trade Mark "ROCIMA 623N" from (ACIMA) Servochem (Proprietary) Limited of 8 Struwig Street, Jet Park, Republic of South Africa; and the defoamer was that available under the Trade Mark "DEFOAMER 15 AF306" from Servochem. To 178t of the colloidal suspension was added 100 kg of ordinary white portland cement available from Lafarge South Africa (Proprietary) Limited of Century Club Estates, 21 Woodlands Drive, Woodmead, Gauteng, Republic of 20 South Africa to obtain about 270 kg of a blend of the cement and the colloidal suspension. To the cement-containing blend were added a further 230f of the "REV 6115" acrylic latex, to form a water-based cement paint according to the 25 invention.

WO 2005/082805 PCT/IB2005/000125 9 Finally, additional optional constituents were added to the paint, namely 100f water into which was admixed 30 kg of titanium dioxide pigment having a particle size in the range 1 - 20pm to form a pigment suspension, together with 5 1.6 kg of hydroxyethyl-cellulose available from Dow/Servochem under the Trade Mark "CELLOSIZE QP52000" and 0.2 kg of dispersant available from Rohm and Haas/Servochem under the Trade Mark "OROTAN N4000". This made up a batch of paint having a mass of 617 - 631 kg and a volume of 570 - 580f. 10 To form the colloidal suspension the biocide, defoamer and cellulose fibres were added slowly to the water with medium-speed stirring, the stirring being continued for 10 minutes after the addition was complete. The suspension was left to digest without stirring for an hour, after which the 15 acrylic latex was added over 5 minutes with medium-speed stirring. To obtain the cement-containing blend, the cement was added slowly to the colloidal suspension with mixing by medium-speed stirring, after which the mixing was continued for a further 10 minutes to obtain a paste, which was left 20 to digest overnight. The remaining acrylic latex was added, after the digestion overnight, to the paste slowly with mixing by medium-speed stirring, which continued for 15 minutes after the addition was complete, to obtain the paint. 25 WO 2005/082805 PCT/IB2005/000125 10 The pigment suspension was made by adding the thickener slowly to the water with medium-speed stirring, after which the stirring was continued for 10 minutes. The pigment was then admixed into the water containing the 5 thickener over a period of 15 - 25 minutes with medium-speed stirring. Finally, the pigment suspension was added to the paint with mixing over a period of 5 minutes by means of medium-speed stirring to colour the paint. 10 EXAMPLE 2 In a subsequent trial Example 1 was repeated except that the "REV 6115" latex was replaced by the same mass of the latex available from Servochem 15 under the Trade Mark "PRIMAL SF-016"; and the white portland cement was replace by the same mass of ordinary grey portland cement, also obtained from Lafarge South Africa (Proprietary) Limited. The titanium dioxide pigment was omitted, the batch sizes and volumes being reduced to 587 - 601 kg and 500 - 510f respectively. 20 EXAMPLE 3 In another subsequent trial Example I was repeated except that the white portland cement was replaced by the same mass of ordinary grey portland 25 cement from the same supplier; and the titanium dioxide pigment was WO 2005/082805 PCT/IB2005/000125 11 replaced by the same mass of red iron (ferrous) oxide pigment of the same particle size. 5 EXAMPLE 4 In a further subsequent trial Example 1 was repeated except that the "NORILOSE 6064" cellulose fibres admixed into the 160f water were increased from 12 kg to 18 kg; and the "REV 6115" latex was replaced by the 10 same mass of "PRIMAL SF-016" latex. The initial trial of the present invention as illustrated by Example 1 showed substantial increases in in-can shelf-life, compared with a control which had the same composition except that it omitted the colloidally-sized cellulose fibres, and 15 promised to render feasible provision of a water-based cement paint which is in single-pack form and can be stored for a substantial shelf-life of several months or more in a paint tin or paint can. Such paint would be useful for coating substrates, in particular cementitious substrates, for both waterproofing and colouring purposes. 20 The subsequent trials detailed in Examples 2 - 4 provided paints which lived up to the promise of Example 1 in that they embodied the advanges promised by Example 1, and exhibited (Examples 2 and 3), or promise to exhibit (Example 4) said long shelf-lives. The paint can be used without frequent stirring after the can has been opened and cures rapidly by virtue of its acrylic latex content, nevertheless 25 continuing to cure for long-term utility by virtue of its cement content. The cement WO 2005/082805 PCT/IB2005/000125 12 content also bonds with cement in cement-containing substrates to which the paint is often expected to be applied, the cement curing and bonding after application thereof to the substrate. 5

Claims

1. A water-based cement paint which includes, as constituents thereof, cement particles and water, wherein the paint is a paint in which the cement particles are uncured cement particles, the paint also including, as a constituent, colloidally-sized 5 particles of polymeric material capable of forming a stable colloid in water, the paint being in the form of a homogeneous blend of said constituents, the cement particles forming 5 - 40% by mass of the paint and the colloidally-sized particles forming 0.25 10% by mass of the paint, and the paint being in single-pack form.

2. A paint as claimed in Claim 1, wherein the cement particles are run-of-the 10 mill portland cement particles, the cement particles forming 10 - 30% by mass of the paint and the colloidally-sized particles forming 1 - 6% by mass of the paint.

3. A paint as claimed in Claim 2, wherein the cement particles form 12 - 18% by mass of the paint, the colloidally-sized particles forming 1.5 - 3% by mass of the paint.

4. A paint as claimed in any one of Claims 1 to 3 inclusive, wherein the cement 15 particles are grey portland cement particles.

5. A paint as claimed in any one of Claims 1-3 inclusive, wherein the cement particles are white portland cement particles.

6. A paint as claimed in any one of the preceding claims, wherein the colloidally-sized particles are fibrous in shape. 20

7. A paint as claimed in any one of the preceding claims, wherein the polymeric material is sodium carboxymethyl cellulose.

8. A paint as claimed in any one of Claims 1 to 7 inclusive, wherein it includes, as a constituent thereof, an uncured particulate elastomer capable of curing upon exposure thereof to the atmosphere. 25

9. A paint as claimed in Claim 8, wherein the elastomer is a latex, the latex forming 5-60% by mass of the paint, and having an average particle size in the range 0.08-1 pm. 14

10. A paint as claimed in Claim 9, wherein the latex forms 20 - 50% by mass of the paint, the latex having a particle size in the range 0.1 - 0.7 pm.

11. A paint as claimed in any one of the preceding claims, wherein it includes 0.1 - 0.6% by mass of a hydroxyalkyl cellulose thickener. 5

12. A paint as claimed in any one of the preceding claims, wherein it includes 1 15% by mass of a pigment.

13. A paint as claimed in Claim 12, wherein the pigment is a particulate inorganic pigment, the pigment forming 2 -10% by mass of the paint and having an average particle size in the range 0.05 - 100pm. 10

14. A paint as claimed in any one of the preceding claims, wherein it is a blend of said constituents, the blend being contained in the absence of air.

15. A paint as claimed in Claim 14, wherein it has a shelf-life of several months or more.

16. A paint as claimed in any one of the preceding claims, wherein it is in a can 15 and has an in-can shelf-life of several months or more.

17. A paint as claimed in any one of the preceding claims, wherein the colloidally-sized particles have a particle size in the range 1 - 100 nm, being capable of forming a stable colloidal suspension in water.

18. A process for formulating a single-pack water-based cement paint according 20 to any one of the preceding claims, wherein the process includes the steps of: suspending the colloidally-sized polymer particles in water to form a colloidal suspension; and admixing the cement particles with the colloidal suspension to form a single-pack 25 paint which is a blend of the water, cement and colloidally-sized polymer particles.

19. A process as claimed in Claim 18, wherein it includes the step of admixing the elastomer particles with the water to form the colloidal suspension, before the admixing of the cement particles with the suspension. 15

20. A water-based cement paint formulated by the process of claim 18 or 19.

21. A water-based cement paint according to claim 1 substantially as hereinbefore described with reference to any one of the examples.

22. A process for formulating a water based cement paint according to claim 19 5 substantially as hereinbefore described with reference to any one of the examples.