AU613807B2 - Coating composition - Google Patents

Description

COMMONWEALTH O Us'R. A8 Patents Act 1952 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number Lodged Complete Specification Lodged Accepted Published

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Priority Related Art Name of Applicant Address of Applicant Actual Inventor Address for Service Complete Specification for the Invention entitled: The following statement is a invention including the best me:- HERON TECHNICS PTY LTD, a New South Wales company 4 Jonathon Place, Frenchs Forest, New South Wales, 2086, Commonwealth of Australia Ronald Peter Hansen H. R. HODGKINSON CO.

Patent Trade Mark Attorneys Alfred Street MILSONS POINT NSW 2061 COATING COMPOSITION full description of this method of performing it known to S0 B112397 10/1 1/89 p uI id m oi THIS INVENTION relates to a coating composition and in particular to a composition for coating and waterproofing buildings, surfaces and the like.

It is well recognised that adequate coating and waterproofing of building surfaces, wall surfaces and the like, is one of the most pressing problems for builders, architects, developers and the like. In particular, prevention of damp borne pollutants, requires that generally porous substrata and surfaces be coated and rendered as water repellent and waterproof as possible.

This can be achieved by way of painting, or overcoating, such as by using polymeric membranes and coatings. However, it is often preferred that the natural appearance of the surface concerned, such as the natural appearance of stone, concrete, masonry and the like be retained.

Various methods and compositions for coating such surfaces have been suggested and available up until this time. However many of these have substantial problems associated therewith.

In some cases, hydrophobic silicone films, although invisible, are effective over a relatively limited period of from one to three years. This however depends on the concent-ation of silicone applied, the depth of penetration, the exposure to sunlight and weather. However, such hydrophobic silicone films must be applied in carrier fluids of hydrocarbon solvents, such solvents at present being under severe criticism from health, safety and environmental authorities. As well as being highly flammable, and thus a safety risk in use, such hydrocarbon solvents cause the release to the atmosphere, of vapours of the solvents, and this is alleged to be a major factor in the depletion of the earthos ozone layer.

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t -1 Some such solvents also contain carcinogenic agents. Further, fumes from such solvents frequently cause industrial disputes, strikes and the like on construction sites.

Attempts have been made to avoid or minimise mineral-solvent problems, by using water solutions of sodium or potassium methyl siliconates, but these have been found to be only partially successful. In application, such compounds tend to react with atmospheric C0 2 in order to produce a hydrophobic silicon compound which does in fact provide water repellency and water proofing for a period of time. However, there are several disadvantages with using methyl siliconates. Apart from the fact that they have a rather limited durability when weather exposed, the silicone-forming reaction creates a byproduct of carbonate salts. This in turn results in a whitish efflorescence on the surface, which is frequently of disfiguring and aesthetically displeasing proportions.

An alternative to using silicone coatings is to treat the surfaces with pore-filling substances such as for example an acrylic polymer either as a solution in hydrocarbon solvent or as an aqueous emulsion. Although such are found to be relatively durable, the acrylic polymer substances do not have the same advantages and hydrophobic features as silicones. Consequently they are lass effective. If applied in sufficient concentration to be totally effective, a disadvantage with such acrylic polymers is that a visible lacquer-darkening and/or gloss appearance results, which is usually unacceptable and aesthetically displeasing for natural surfaces and substrate.

It has also been suggested to combine silicons with lowconcentration acrylics, and this has been relatively effective. However, this has only been possible in hydrocarbon solutions which involve the dangers and 3 Ln -1 L ~LPP-p_ rra disadvantages referred to above, relative to silicones being applied in hydrocarbon solutions.

It has previously been suggested that siloxanes (siliconeforming substances) should be combined with acrylics or other polymers, in water-emulsion form. However, this has been considered impossible, due to the normal curing reaction of the siloxanes, etc. These normally react quickly with moisture either from the substrate or from the atmosphere, to produce the hydrophobic property for which they are used.

Thus, attempts to insert silicones into water-carried acrylic emulsions have been self-defeating. The silicone component has been converted by the water fraction of the emulsion into an insoluble precipitate. The use of water-compatible methyl siliconates, which has also been explored, suffers from the i 5 efflorescence-forming problem referred to above.

It is therefore an object of this invention to go some way towards overcoming or at least minimising the problems and disadvantages set out above.

It is a further object of this invention to provide a straight-forward and efficient coating composition.

040009 According to one aspect of this invention there is provided a coating composition comprising a mixture of alkyl-alkoxysilane and non-aqueous, non-hydrolysed coalescent agent, mixed with aqueous acrylic emulsion.

According to a further aspect of this invention there is provided a method of forming a coating composition, said method including mixing together alkyl-alkoxy-silane and nonaqueous non-hydrolysed coalescent agent, and thereafter combining and mixing said mixture with aqueous acrylic emulsion by substantial and positive stirring and mixing.

4 AAY7t This invention will now be described by way of example only and it should be appreciated that modifications and improvements may be made to the invention without departing i from the scope or spirit thereof.

The present invention sets out to provide a coating composition and a method of forming a composition, whereby the composition provides a means for coating wall surfaces and the like, in an efficient and straight-forward manner, but without the disadvantages, site problems and the like which have been associated with various coating compositions used up until this time.

Thus, the present invention has found that alkyl-alkoxysilanes (being a base for silicone) may be mixed and blended with non-aqueous, non-hydrolysed coalescent agents, without any chemical action therebetween and while remaining stable in storage. It has also been found that by mixing together the mixture of alkyl-alkoxy-silane and non-aqueous, nonhydrolysed coalescent agent, with aqueous acrylic emulsion, a particularly efficient and straight-forward coating composition is formed. It has been found that by mixing the mixture of alkyl-alkoxy-silane and non-aqueous, nonhydrolysed coalescing agent, with an aqueous acrylic emulsion, the coalescent agent acts to carry the silicone into the acrylic particles, to become an integral part thereof, and to retard and inhibit the hydrolysing of the silicone as normally takes place when silicone is mixed with an aqueous medium. The remainder of the composition is in the

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i form of an appropriate bearer or carrier tluid such as water.

Thus, the resultant mixture acts to effectively shield the 30 silicone from excess contact with the water of the emulsion, this retarding the usual reaction between silicone and water, long enough for the water to evaporate in application and for coalescence and cross-linking to proceed following application of the coating composition.

The composition of the present invention is preferably formed as a two-pack or binary system. One pack or container carries the mixture of alkyl-alkoxy-silane and non-aqueous, nonhydrolysed coalescent agent, while the other pack or container carries aqueous acrylic emulsion. The two are mixed together and as the mixture of alkyl-alkoxy-silane and nonaqueous, non-hydrolysed coalescent agent is relatively viscous and oily, substantial and positive stirring and mixing between the two is necessary, before the resultant composition can be used for coating to bring about waterproofing and the like.

It has been found that the most appropriate alkyl-alkoxysilanes to be used in the present invention are, by way of example, oligomeric alkyl-alkoxy-silanes and polymeric alkylalkoxy-silanes.

It has been found that the coalescent agent, such as might normally be used in acrylic emulsions, for coalescence, is appropriate to act as a coalescent agent in the present invention. It has been further found that appropriate nonaqueous and non-hydrolysed coalescent agents, for use in the present invention, are non-aqueous organic solvents, for example, dodecyl butyrate, 2,2,4,trimethyl 1,3, pentandiol monoisobutyrate, ethylene/diethylene glycol monobutyl ether, n-propoxypropanol and phenyl cellosolve.

It has been found that the above may be mixed together without a chemical reaction taking place and that they have a relatively long shelf life and will remain stable in storage.

Prior to use of the coating composition the mixture is added to an aqueous acrylic emulsion which is preferably an acrylic emulsion which can be further cross-linked, by interaction with polyfunctional aziridine. As indicated hereinbefore, 6 .4 substantial stirring is necessary to allow for complete dispersion of the mixture into the aqueous acrylic emulsion.

Throughout the specification and claims reference to the term "acrylic emulsion" is defined as being reference to an acrylic film forming emulsion which will coalesce and crosslink to form continuous film when dried at temperatures of between 3°C and 50 0

C.

It has been found that emulsions which are particularly, although not exclusively, appropriate to the present invention are DURAMUL 641; DURAMUL 637; DURAMUL 603 and DURAMUL 609 (trade marks) of Albright Wilson Australia Limited; VINACRYL 4009 (trade mark) of Vinyl Products Limited of the United Kingdom; ACROCRYL 63-941 (trade mark) of A.C.

Hatrick Chemicals of Australia; RHOPLEX WL-81 (trade mark) of Rohm Haas of the United States of America and South Africa; NEOCRYL A623 (trade mark) of Polyvinyl Chemie of The Netherlands and CARBOSET 525 (trade mark) of B.F. Goodrich Chemical of the United States of America. These acrylic emulsions have been found to be particularly useful in the present invention, but it should be appreciated that they are referred to by way of example only and that other appropriate acrylic emulsions, as defined above, can be used to equal advantage.

In one form of the invention it has been found that a preferred coating composition includes at least 2% (by weight) and preferably between 2% (by weight) and 10% (by weight) silaie; at least 6% (by weight) and preferably between 6% (by weight) and 15% (by weight) aqueous acrylic emulsion and from 1% (by weight) to 13% (by weight) coalescent agent. The remainder of the composition is in the form of a carrier or bearer fluid, such as water. In one preferred form of the invention, the amount of silane is 7 L I L 111 00 preferably between 2% (by weight) and 9% (by weight).

The above is by way of example only however.

It has been found that when the mixture of alkyl-alkoxysilane and non-aqueous, non-hydrolysed coalescent agent is mixed with the aqueous acrylic emulsion, the silicone substance (alkyl-alkoxy-silane) is carried by the coalescent agent into the acrylic particles of the aqueous acrylic emulsion, to become an integral part thereof and in the subsequent coalescence and cross-linking process. Thus, the silicone is effectively shielded from excess contact with the emulsion water, this retarding and minimising the usual reaction between water and silicone, long enough for the water to evaporate during application, and for coalescence and cross-linking to proceed in the applied coating.

In one form of the invention the composition may contain anti-gloss agents.

It has been found that it is desirable to use the composition within at Least 1-8 hours from the mixing or blending of the mixture of alkyl-alkoxy-silane ar.d non-aqueous, nonhydrolysed coalescent agent and aqueous acrylic emulsion, if a loss of hydrophobic performance is to be avoided. In one form of the invention it has been found that the composition should be applied and used within 1-4 hours of mixing. The actual time may vary however depending upon the temperature, weather conditions and type of silicone used.

The present invention provides a number of substantial advantages over previous coating compositions. In particular, the acrylic structure of the coating gives ultraviolet durability, which is particularly helpful and advantageous in sunlight. The composition has been found to have good compatibility with alkaline substrates such as for example concrete. It has been found that the composition is able to

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be easily applied over cement-based paints and can be applied over oil-based paints and enamels. The coating composition of the present invention has been found to reduce and minimise moisture penetration and the corrosion of reinforcement, and the like. The coating has also been found to reduce and minimise fungus growth by preventing dampness in pores of the surface being coated. The coating has therefore been found to have good penetration of the surface being coated and acts successfully as a water-proofing and water repellent coating.

It should be appreciated that modifications and improvements may be made to the invention without departing from the scope thereof as defined by the appended claims.

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Claims (10)

1. A coating composition comprising a mixture of alkyl- alkoxy-silane and non-aqueous, non-hydrolysed coalescent agent, mixed with aqueous acrylic emulsion.

2. A coating composition as claimed in claim 1, wherein said alkyl-alkoxy-silane includes oligomeric alkyl-alkoxy- silane.

3. A coating composition as claimed in claim 1, wherein said alkyl-alkoxy-silane includes polymeric alkyl-alkoxy- silane.

4. A coating composition as claimed in any one of the preceding claims, wherein said aqueous and non-hydrolysed coalescent agent is in the form of non-aqueous organic solvent. A coating composition as claimed in any one of the preceding claims, wherein said non-aqueous and non-hydrolysed coalescent agent is selected from dodecyl butyrate, 2,2,4,trimethyl 1,3, pentandiol monoisobutyrate, ethylene/diethylene glycol monobutyl ether, n-propoxypropanol and phenyl cellosolve.

6. A coating composition as claimed in any one of the preceding claims, including between 2% and 10% (by weight) alkyl-alkoxy-silane; from 1% to 13% (by weight) non-aqueous, non-hydrolysed coalescent agent and from 6% to 15% (by weight) aqueous acrylic emulsion.

7. A coating composition as claimed in any one of the preceding claims, including anti-gloss agent. -4 S8. A coating composition as claimed in claim 8, wherein said composition is used within one to 6 hours of the mixing of the mixture of alkyl-alkoxy-silane and non-aqueous, non- hydrolysed coalescent agent, with said aqueous acrylic emulsion.

9. A coating composition as claimed in the preceding claim, wherein said composition is used within one to four hours of said mixing. A method of forming a coating composition, said method including mixing together alkyl-alkoxy-silane and non- aqueous, non-hydrolysed coalescent agent, and thereafter combining and mixing said mixture with aqueous acrylic emulsion by substantial and positive stirring and mixing. 00 0 0 0 So 11. A method as claimed in claim 10, wherein said S composition is formed using a binary system; one pack or container carrying a mixture of alkyl-alkoxy-silane and non- oo aqueous, non-hydrolysed coalescent agent; a second pack or a. °container carrying said aqueous acrylic emulsion.

12. A method as claimed in either of the preceding claims t 10 and 11, including the addition of anti-gloss agent to said composition.

13. A method as claimed in any one of the preceding claims 10 to 12, wherein said composition is used witlin one to s..x hours of the mixing or blending of the mixture of alkyl-alkoxy-silane and non-aqueous, non-hydrolysed coalescent agent with said aqueous acrylic emulsion.

14. A method as claimed in claim 13, wherein said composition is used within one to four hours of said mixing. Dated this twenty-third day of May 1991 S11 S\ 7 '*VVl4 2 0o k. 22n j HERON~ TECHNIUCS PTY! LTD by. Its Patent Attorney 12