IL23212A - Surface coating compositions - Google Patents

Description

C O H E N Z E D E & S P I S B A C H REGD. PATENT ATTORNEYS 24, LEVONTIN SIR., P. O. B. 1169 P A T E N T S & D E S I G N S O R D I N A N C E 13044/65 SPECIFICATION IMROVElpHTS UJ OR RELATING TO SURFACE- COATING COMPOSITIONS Tn "?t on ■»:»"» D"»no»o 'la's1? nnnyna D'Vi aw WE, VIHYL PRODUCTS LIMITED, a British ompany, of -Gu ter Hill, Carshalton, Surrey, England, DO HEREBY DECLARE ihe nature of this invention and in what manner the same is to be performed to be particularly described and ascertained in and by the following statement: This invention relates to surface-coating compositions and* in particular, to compositions containing a vi yl polymer as a binder, the compositions being of the kind which are especially useful as flooring and plastering compositions.

Polyvinyl acetate has been frequently used in the past as the sole hinder in euch flooring and plastering compositions, although it has been found in practice that where a surface coated with such a composition Is subjected to conditions in which water is able to lie on the coated surface, the coatings tend to soften and break away from the substrate.

With this problem in view, our investigations have bean concerned with the preparation of coating compositions suitable for use as floorin and plastering compositions and containing, as binder, a film-forming vinyl polymer which contains funet-ional groups capable of forming cross-linkages* with or without the aid of a c oss-linking agent* and/or is film- formin only at elevated temperatures.

Throughout this specification the term ·vinyl polymer* includes homopolymers and copolymers of vinylidene monomers as well as copolymers of vinyl and/or vinylidene monomers with 1,2-disubstituted ethylenes* such as malele and crotonic acids.

According to the present invention there is provided a surface-coating composition comprising, as a binder, a film-forming vinyl polymer which contains functional groups capable of forming cross-linkages, with or withou the aid of a cross-linking agent* and/or is film-forming only at elevated temperatures* and a filler material at least a part of which is of such a particle else that It is retained by a 60 mesh sieve* throughout this specification the particle sizes are The compositions may additionally contain other filler material, which may be of various particle sizes and other conventional ingredients of surface-coatin compositions, such as pigments, may also be included in the compositions of the invention as well as other binders to modify the properties of the compositions.

The ability of vinyl polymers to undergo cross-linking depends upon the nature of the functional groups present as substituents in the polymer and examples of groups which can render a polymer capable of cross-linking are hydroxyl and carboxyl groups.

One convenient method of preparing the vinyl polymers is by polymerising a vinyl monomer containing the desired functional group, with or without other vinyl monomers which may or may not contain the same functional group.

Alternatively some or all of the desired functional groups may be introduced into a preformed vinyl polymer by reacting the polymer with one or more xx3B¾z4 compounds which contain the desired functional group or groups.

- A vinyl polymer which is capable of cross-linking may, for example, be prepared by inter-polymerising one or more vinyl monomers containing free hydroxyl and/or carboxyl groups, preferably in the presence of one or more vinyl monomers which do not contain functional groups which in the final polymer are capable of forming cross-linkages.

Examples of suitable monomers containing free carboxyl maleic acid, crotonic acid groups are methacrylic acid, acrylic acid/and itaconic acid and examples of suitable monomers containing free hydroxyl groups are N-methylolacrylamide and 2-hydroxy-ethyl into the polymer, functional groups which are capable of forming cross-linkages may be mentioned styrene and the alkyl esters of acrylic acid and methacrylic acid and such monomers are advantageously used to modify the pro-perties of the final polymers by copolymerisation with the monomers containing free carboxyl and/or hydroxyl groups.

The polymers which are employed in the compositions of the invention may be divided into two broad groups, namely those which are film-forming at room temperature and are also capable of cross-linking at room temperature and, secondly, those which require heating to induce film-formation and/Or cross-linking. Compositions containing polymers of the first-mentioned group may be coated onto a wall or floor and, after any solvent present in the coat-ing has been allowed to evaporate4 the composition will cure at normal ambient temperatures, although the coating may be heated, if desired, to flash off the solvent or to increase the rate of cure. In the case of compositions containing polymers in the second group, heating is essen-tial to bring about a curing of the composition by cross-linking the polymer or by raising the temperature above the film-forming temperature of the polymer. Polymers of both groups may require the presence of a cross-linking agent to enable the polymer to cure. Throughout this specification the term "curing" is used to describe the coalescence of the particles of a vinyl polymer under the influence of heat without the accompanying formation of cross-linkages in the polymer as well as the formation of cross-linkages in a polymer either at normal ambient all cases "being the production of a coherent and adherent coating.

It is found that infra-red heaters are particularly effective for heating coatings of the compositions of the invention, although an oven may be used, if desired, where the coatings are applied to surfaces of convenient size, such as in the case of building panels or tiles.

In practice, the vinyl polymers are normally prepared by solution or emulsion polymerisation and the polymer solution Or emulsion is conveniently used directly in the formulation of the surface-coating compositions of the present invention by mixing the required quantity of filler into the polymer solution or emulsion. The compositions may, of course, be thinned with water in the case where an emulsion polymer is employed or thinned with the appropriate solvent where a solution polymer is used. The application properties of the compositions can be further modified by the addition of a thickener such as a bentonite clay or a water-soluble cellulose derivative, e.g. ethyl hydroxy ethyl cellulose, although the preferred thickener is an ammonium acrylate polymer.

The vinyl polymer is preferably employed in an amount of from to 10% of solid polymer by weight of the filler although the preferred proportion of polymer in a particular case will depend on the particle size of the filler. Because the surface area of the filler increases as the particle size decreases, the optimum proportion of polymer will increase as the particle size decreases. mix having a particle size range of from -10 to +22 mesh.

The invention includes a method of coating a substrate which comprises applying to a substrate a coating of a composition in accordance with the invention and then allowing the vinyl polymer component of the composition to cure at normal ambient temperature or curing the polymer by the application of heat. Preferably a primer coat comprising a solution or emulsion of the vinyl polymer component of the composition is applied first to the sub- the water and/or organic solvents are allowed to flash off strate and/¾g¾gatra¾:aggxaTkTtmtKtetrnxamne prior to the application of the coating of the composition. The primer coat preferably comprises a solution or emulsion of the polymer at about 2% solids content.

The method of application of the compositions of the invention depends upon the viscosity of the particular composition and the size of the filler particles. The method employed in a particular case may be selected from any of the conventional methods, for example spraying or trowelling or, where large vertical surfaces are to be coated, using a machine which hurls the composition at the surface by means of a rotating paddle-wheel device, a suitable machine being that known as a Tyrolean applicator.

The compositions of the invention may be used to coat a large number of different materials of which the following are examples; asbestos-cement, asbestolux, hardboard, plywood, chipboard, steel, wood, foamed polystyrene, concrete, plasterboard and other common materials used in building construction.

T e followin Exam les in which the arts ercent- given to illustrate the manner in which the invention may be carried into effect :- The following two Examples illustrate compositions containing polymers which are capable of being cured at room temperature.

Example I Parts Derbyshire spar (calcite spar) (-10 to +22 mesh) 2 .3 White calcined flint (-10 to +22 mesh) 56.7 ^0 aqueous solution of oxalic acid 2.

Emulsion copolymer of methyl meth- acrylate, butyl acrylate and N-methyl- ol acrylamide in the proportions of 40:55:5 at 5% solids content 2,6 Ammonium polyacrylate 1.0 Water 2.9 100.0 The above ingredients are mixed together to form a paste, the ammonium polyacrylate serving to improve the trowelling properties of the composition. The resulting composition, which has an indefinitely long pot life, can be thinned by adding water. When applied to a substrate and dried, the composition will cure in a few days at room temperature, the oxalic acid acting as a cross-linking agent, and the curing can be accelerated by heating, Example 2 Parts Derbyshire spar (-10 to +22 mesh) 20.8 White calcined flint (-10 to +22 mesh) 48.4 Toluene di-isocyanate 9.9 Copolymer of ethyl acrylate, styrene and 2-hydroxy-ethyl methacrylate in the proportions of 80:10:10 9.9 2-Ethoxy-ethyl acetate 2.4 Santocel FRO 0.4 1:1 by vol. xylene/n-butanol mixture 8.2 100.0 The above ingredients, except for the solvent mixture, are mixed together and then the solvent mixture is added to thin the composition to a trowellable consistency, the Santocel FRG (a finely divided silica aerogel having an average particle size of from 0.5 to 3 microns) being added, if desired, to improve the application properties of the composition. The isocyanate acts as a cross-linking agent and the composition will cure at room temperature, the pot life of the composition being about 8 hours. 2-Ethoxy ethyl acetate is a high-boiling solvent which assists the evaporation of the xylene and butanol.

The following Examples illustrate compositions which require heating to effect cross-linking and/or film-formation of the polymer.

Example 5 Parts Derbyshire spar (-10 to +22 mesh) 24.2 White calcined flint (-10 to +22 mesh) 56. 5 Ammonium acrylate copolymer 1.0 Emulsion copolymer of styrene , butyl acrylate and acrylic acid in the proportions of 48:48:4 at 40% solids content 14.4 Water 1 100.0 The above ingredients are mixed together and, after applying the mixture to a substrate, the coating so produced is dried and heated to 0°C for half an hour, for example, in an air-circulating oven or by means of an infra-red heater, to induce film-formation of the copolymer.

Example 4 Parts Derbyshire spar (-10 to +22 mesh) 24.1 White calcined flint (-10 to +22 mesh) 6.3 Vinyl copolymer mixed with a melamine- formaldehyde precondensate in the proportions of 100 : 50 by weight 11 .3 Water 8 100.0 The above ingredients are mixed together and the composition so produced may be diluted with water.

No thickening agents are necessary as the composition itself increases in viscosity with dilution. After application to a substrate as a coating, the composition is dried and then heated to 150°C for half an hour to cure the vinyl copolymer, for which the melamine-formaldehyde The vinyl copolymer used in this Example is a solution copolymer of methyl methacrylate, butyl acrylate and methacrylic acid in the proportions of 50:40:10 which was prepared in 2-methoxyethanol at 45% solids content.

Dimethylaminoethanol was added to the copolymer to neutralise the methacrylic acid and to render the copolymer solution water-thinnable.

Example 5 Parts Derbyshire spar (-10 to +22 mesh) 56.7 White calcined flint (-10 to +22 mesh) 24.3 % aqueous solution of oxalic acid 2*5 Ammonium polyacrylate 1,0 Emulsion copolymer of methyl methacrylate, butyl acrylate and N-methyl- ol acrylamide in the proportions of 60:35:5 at 45% solids content 12.6 Water 2.9 100.0 The composition produced by mixing together the above ingredients is coated on to a substrate and cured in the same manner as that described in Example 4.

The vinyl polymer employed in this Example is similar to that used in Example 1 but its properties differ in that its film-forming temperature is about 60°0 and it forms harder films.

Example 6 Parts Derbyshire spar (-10 to +22 mesh) 23.4 White calcined flint (-10 to +22 mesh) 54.5 Vinyl copolymer composition 10.9 Pine oil 3.3 Santocel FRC 0.4 Xylene 7.5 100.0 The vinyl copolymer composition is prepared by mixing together 81.3 parts of a vinyl copolymer, 7.3 parts of xylene, 8.1 parts of the epoxy resin sold under the trade name Epikote 828 (the word "Epikote" is a Registered Trade Mark) and 3.3 parts of dimethylamino-ethanol. 10.9 parts of this mixture are then mixed with the other ingredients noted above. The vinyl copolyme employed in this Example is a copolymer of styrene, ethyl acrylate, acrylic acid and itaconic acid in the proportions of 62:30:4:4.

The resulting composition has a pot life of about 4 hours and, when applied to a substrate as a coating, is cured in the same manner as described in Example 4.

The following composition is based on a polyvinyl acetate resin and is typical of conventional polyvinyl acetate-based plastering compositions.

Composition A Parts Derbyshire spar (-10 to +22 mesh) 24.0 White calcined flint (-10 to +22 mesh) 56.0 Polyvinyl acetate emulsion plasticised with dibutyl phthalate 10.6 % aqueous solution of ethyl hydroxy ethyl cellulose 5.5 Water 3.9 100.0 The above ingredients are mixed together and form a composition of trowellable consistency, the cellulose derivative serving as a thickener. The resulting composition may be applied to a substrate using a trowel and will form a coherent and adherent coating at room temperature.

A series of tests have been carried out on the compositions described in the foregoing Examples as well as on Composition A above in order to determine the effect on cured coatings formed from them of prolonged exposure to water. The tests were carried out by coating eacji composi-tion onto a variety of different substrates, the substrates being sealed in each case by the application of a primer coat of the vinyl polymer component of the composition which is to form the main coating. The primer coat was applied in each case at a solids content of 2 % and was allowed to dry in air at about 60°F (in the case of Examples 1 and 2 and Composition A) for three days or was stbved ¾fcc¾pc¾l at 0°C in an air-circulating oven (in the case of Examples 3 to 6 after allowing the solvent to evaporate for half an hour at room temperature). After the primer a thickness equal to the particle size of the filler and this coating was cured or allowed to cure under the same conditions as the primer coat.

The coated substrates were then totally immersed in a tank of water at 20°C and after a series of intervals of time the coatings were prodded with a sharp instrument to determine to what extent, if any, the coating had deteriorated. The results are shown in the following table in which the numbers represent the hardness and adhesion of the coatings on an arbitrary scale where 10 represents a hard tough coating with good adhesion to the substrate while 0 represents a coating whose adhesion and cohesion is so poor that it immediately disintegrates and falls off the substrate when prodded. The nature of the substrate is indicated in the table by the abbreviations A/C, P/W, S, F/C which refer respectively to asbestos-cement sheet, marine plywood, mild steel sheet and foamed concrete block and the symbol 'Ε' in the table means that the substrate became corroded.

As will be seen from the above tabulated results, coatings prepared from the compositions described in the Examples in general show little deterioration in hardness and adhesion in spite of prolonged immersion in water and their performance is net affected to any significant extent by the nature of the substrate. The only case in which the nature of the substrate resulted in any difference in performance was in the case of the composition of Example 4-, where the adhesion of the coating to plywood failed after 48 hours immersion. By contrast with the excellent performance of the compositions described in the Examples, it will be seen that a coating of Composition A completely disintegrated after only one hour immersion.

Prom a consideration of the performance of the polyvinyl acetate-based composition (Composition A), it will be appreciated that the test procedure to which the coatings were subjected is very severe, since a conventional polyvinyl acetate-based composition of the type represented by Composition A will withstand x&rtx&atxammB&xBxweathering by rain when coated on a substrate and exposed to a normal outdoor environment, provided that water is not able to lie on the coating. Thus, although the compositions of Examples 1 and 3 did not equal the performance of those of the remaining Examples, the results obtained for these two Examples nevertheless represents excellent performance when considered in terms of resistance to natural weather conditions. The polymer employed in Example 1 is perhaps a little too soft for optimum performance in a plastering composition since it had an initial with, the results given in connection with the composition of Example 5 that an increase in the proportion of methyl methacrylate in the vinyl polymer results in significantly improved hardness. It should be noted that, despite the fact that the polymer employed in Example 3 is of the non-cross-linking type which forms a coherent film by coalescence of particles of polymer at elevated temperatures, its performance in wet conditions is excellent when compared with polyvinyl acetate-based compositions.

It was also found that coatings produced in accordance with the foregoing Examples, exhibited good adhesion on exterior exposure to many substrates, that their dirt retentio /was lew and that they had hard surfaces(except for the coating produced in Example 1 ) , although they were flexible enough to with-stand a certain amount of thermal movement of the substrate. The property of the vinyl copolymer composition used in Example 4- of increasing its viscosity with dilution, which depends upon the proportions of the monomers and the nature of the solvent in which the polymerisation is carried out, is a valuable property in the compositions of the invention and it is a feature of the invention that the vinyl polymer component of the compositions is a vinyl copolymer of the kind employed in Example 4·.

Although the same filler material is employed in each of the foregoing Examples, it will be appreciated that any filler material may be employed in lieu of some or all of the Derbyshire spar and calcined flint, provided that at least a part of the filler material has a particle size such that it is retained by a 60 mesh sieve. Examples compositions of the invention are Leemoor sand, Zone 2 (-10 to +22 mesh); Windsor rose sand (-10 to +5 mesh) and 20 Gore sand (-10 to +100 mesh).

While in the foregoing Examples the ingredients of the compositions are mixed together prior to application to a substrate, it is also possible in accordance with the invention to produce the compositions in situ on the substrate by applying the vinyl polymer, in admixture with other ingredients except for the filler material, as an adhesive coating and then scattering the filler material over the surface of the coating or projectin the filler material at the coating, followed by curing the polymer at elevated temperature or allowing it to cure at normal ambient temperature, depending on the particular polymer employed.

Claims (21)

1. WHAT IS CLASSED IS» t. A surface-coating composition which comprises, as the sole hinder o a major proportion of the binder, a film-forming vinl polymer as hereinbefore defined and a iller material at least a part of which is of each a particle else that it la retained by a 60 mesh sieve*

2. A eorapoeltion according to claim t wherein the -vinyl polymer la prepared by interpolymerlsing one or more vinyl monomers containing functional groups which in the final polymer are capable of forming cross- linkages, with or without one or more vinyl monomers which do not contain such functional groups

3. · A composition according to claim t wherein some or all of tire ^ntctlonal groups are introduced, into the vinyl polymer by reacting a preformed vinyl polymer with a vinylcompound containing the desired functional group or groups*

4. » A composition according to any of the preceding claims wherein the functional groups are hydroacyl andor carboxyl groups*

5. „ composition according to claim wherein the carboxyl groups are introduced into the vinyl polymer by polymerisation of one or more of me haeryllc acid* malelc acid, crotonic acid* acrylic acid and itaconic acid*

6. A composition according to claim 4· or claim 5 wherein the hydroxyl groups are introduced into the vinyl polymer by polymerisation of one or both of N-methylolacrylamide and 2-hydroxyethyl acrylate.

7. A composition according to any of the preceding claims wherein one or more acrylate or methacrylate alkyl esters are included in a polymerisation mixture from which the vinyl polymer, or a polymer from which it is derived, is formed.

8. I A composition according to any of the preceding claims wherein the vinyl polymer is present in the form of a solution or an aqueous emulsion.

9. A composition according to any of the preceding claims which includes a cross-linking agent for the vinyl polymer.

10. A composition according to claim 9 wherein the cross- citric acid, phosphoric acid hexa(methoxymethyl)melamine linking agent is oxalic acid/ toluene diisocyanate, an epoxy resin or a melamine-formaldehyde precondensate.

11. A composition according to any of the preceding claims which includes a thickener.

12. A composition according to claim 1 wherein the thick-r ener is a bentonite clay, a water-soluble cellulose derivative or an ammonium acrylate polymer.

13. A composition according to any of the preceding claims wherein the vinyl polymer is present in an amount ef from 5 to 10% of solid polymer by weight of the filler material .

14. A composition according to any of the preceding claims which includes a melamine-formaldehyde precondensate said composition having the property that its viscosity increases with dilution.

15. A surface-coating composition substantially as described with reference to any of Examples 1 to 6.

16. A method of coating a substrate which comprises applying to a substrate a coating of a composition claimed in any of the preceding claims and then allowing the vinyl polymer to cure at normal ambient temperature or curing the polymer by the application of heat.

17. A modification of the method according to claim 16 wherein an admixture of the ingredients of the composition other than the filler material are applied as a coating onto the substrate and the filler material is then scattered over or projected onto the coating, whereupon the polymer is allowed to cure at normal ambient temperature or is cure£ by the application of heat.

18. A method according to claim 16 or claim 17 wherein the polymer is cured by the action of infra-red heat.

19. 9. A method according to any of claims 6 to 18 wherein a primer coat comprising a solution or emulsion of the vinyl polymer is first applied to the substrate and, after the polymer has cured either at normal ambient temperature or at an elevated temperature, a coating of the composition (based on the same vinyl polymer) is applied to the primer coat.

20. A method of coating substrates according to claim 16 substantially as described herein.

21. A method of manufacturing a surface-coating composition which comprises mixing a filler material, at least a part of which is of such a particle size that it is retained by a 60 mesh sieve, into a solution or emulsion of a film-forming vinyl polymer which contains functional groups capable of forming cross-linkages, with or without the aid of a cross-linking agent, and/or is film-formin only at elevated temperatures* DATED THIS 21st day of Maro , 1965.