GB2121424A

GB2121424A - Waterproofing compositions, their preparation and their use

Info

Publication number: GB2121424A
Application number: GB08311793A
Authority: GB
Inventors: Rene Arpin; Louis Bourdon; Damien Radtke
Original assignee: Rhone Poulenc Specialites Chimiques
Current assignee: Rhone Poulenc Specialites Chimiques
Priority date: 1982-05-03
Filing date: 1983-04-29
Publication date: 1983-12-21
Also published as: CH655939A5; DE3315787A1; GB8311793D0; IT8320909A0; GB2121424B; NL8301536A; IT1163291B

Abstract

The invention provides a waterproofing composition containing an aqueous dispersion, stable at basic pH, of a film-forming copolymer of an alkyl acrylate and a vinylaromatic monomer, and a specified proportion of an alkali metal alkylsiliconate. The composition is prepared by mixing a dispersion of the copolymer with an aqueous solution of alkali metal alkylsiliconate. It is used for waterproofing and protecting various surfaces such as facades made of hydraulic binders, tiles, wood and the like. The composition can also contain fungicides and/or insecticides if it is used for protecting wood.

Description

SPECIFICATION Waterproofing compositions, their preparation and their use The present invention relates to compositions for waterproofing and protecting various surfaces such as facades, tiles, wood and the like, to their preparation and to their use for treating the said surfaces.

It is known from German Application No. 2,355,813 to use an aqueous dispersion containing: - a polymer of butyl, ethyl or methyl acrylate or a copolymer based on acrylic and/or methacrylic acid or their esters, and - from 2 to 5% of the weight of the dispersion of a silicone in aqueous phase, in particular of sodium methylsiliconate, as a binder for the preparation of pigmented exterior or interior coverings having an improved water resistance.

It is also known from U.S. Patent No. 4,012,355, to protect the surface of finely divided materials against erosion by treatment with a composition containing: - an aqueous dispersion of film-forming polymers such as styrene/butadiene/acrylic acid or acrylate terpolymers, polyolefines, polyvinyl acetate, polyalkyl acrylates or methacrylates, or the like, and - a silicone in aqueous or hydrocarbon solution, in particular a siliconate in aqueous solution, with a weight ratio of film-forming polymer/silicone of between 12/1 and 1/1.

It is particularly advantageous if compositions based on synthetic polymers, used for treating surfaces such as facades based on hydraulic binders, tiles and the like, possess the following characteristics in addition to waterproofing properties: - a good film-forming ability, - a good stability to ultraviolet and - a good stability in an alkaline medium, that is to say are of low viscosity and are not saponified in an alkaline medium, in particular at a pH above 1 O.

It has been found that polymers containing carboxyl units derived from ethylenic monocarboxylic or dicarboxylic acids, for example, must be excluded because of their poor stability in an alkaline medium.

We have now found that copolymers of the styrene/alkyl acrylate type, dispersed in an aqueous medium stable at alkaline pH, possess the desired characteristics and can be associated with an amount of waterproofing agent which is substantially greater than that present in the compositions of the prior art based on alkyl acrylate copolymers.

The compositions of the present invention are stable on storage and: - easy to apply to facades based on hydraulic binders, by the conventional processes (roller, pneumatic gun or the like), which compositions, after drying, form a film possessing the characteristics of adhesion and of resistance to ultraviolet of acrylic resins, and the surface properties of silicone resins, and permitting improved waterproofing of the facades, - and also capable of waterproofing and treating wood on and below the surface.

The compositions of the present invention comprise an aqueous dispersion of a film-forming copolymer of alkyl acrylate and a vinylaromatic monomer in an aqueous medium stable at basic pH, the said vinylaromatic monomer being such that the homopolymer corresponding - to the said vinylaromatic monomer has a glass transition temperature of between 70 and 1 700C, and an alkali metal alkylsiliconate in an amount from 0.05 to 0.17 mol of alkylsiliconate per 100 g of dry copolymer, the elementary entity corresponding to the term "mol" of alkylsiliconate being the group:

0 0 - si - o Alkyl Examples of vinylaromatic monomers which may be mentioned are styrene and methylstrenes.

The alkyl acrylates which can be used are those of which the corresponding homopolymer has a glass transition temperature of between + 1 00C and -600C. The alkyl acrylates in which the alkyl group contains from 1 to 8 carbon atoms and preferably from 1 to 4 carbon atoms, may be used.

The respective amounts of vinylaromatic monomer and of alkyl acrylate used are chosen so that the copolymer obtained has a glass transition temperature of between -50C and +250 C.

The amounts of monomers to be used depend on the nature of the said comonomers and on the desired glass transistion temperature of the copolymer. The said amounts can easily be determined, for example by applying the formula of FOX given in Bull. An. Phys. Soc. 1956, 1, 123.

Thus: - a styrene/ethyl acrylate copolymer has a glass transition temperature varying between OOC and 200C when the ratio of styrene/ethyl acrylate varies between 26/74 and 45/55, and - a styrene/propyl acrylate copolymer has a glass transition temperature varying between OOC and 200C when the ratio of styrene/propyl acrylate varies from 36/64 to 52/48, polystyrene having a glass transition temperature of +1 000C, polyethyl acrylate of -240C and polypropyl acrylate of-370C.

The indicated values of glass transition temperatures are those measured by the so-called "Differential scanning calorimetry" method described, for example, by A. Lambert in "Polymer 10, 319, 1969".

The aqueous dispersions of copolymers of vinylaromatic monomer and alkyl acrylate are obtained by polymerisation of the said monomers in aqueous emulsion, in a medium stable at alkaline pH.

In addition to the said monomers, the said polymerisation medium comprises an aqueous phase and various adjuvants conventional for polymerisation in emulsion (catalysts, emulsifiers and the like), the latter being chosen from among those which are stable in an alkaline medium.

Examples of catalysts which may be mentioned are: organic hydroperoxides such as those of cumene, diisopropylbenzene, paramenthane and the like, and persulphates such as those of sodium, potassium or ammonium.

Amongst the emulsifiers which can be present, there may be mentioned anionic agents such as: alkali metal salts of fatty acids and alkali metal aklyl-sulphates, alkylsulphonates, aryl-sulphates, arylsulphonates, alkylaryl-sulphates, alkylarylsulphonates, sulphosuccinates and alkyl-phosphates, and non-ionic agents such as: polyoxyethyleneated fatty alcohols, polyoxyethyleneated alkylphenols and polyoxyethyleneated fatty acids.

The aqueous dispersion of copolymer of vinylaromatic monomer and alkyl acrylate can contain from 20 to 60% by weight of solids and preferably from 40 to 55% by weight of solids, with a particle diameter of between 0.05 and 0.5 ssm. If appropriate, the said dispersion can be diluted according to the nature of the surface to be treated.

The alkali metal alkylsiliconates which can form part of the waterproofing compositions forming the subject of the invention are those having a C1-C3-alkyl group. The preferred amount of alkylsiliconate which can be used is 0.065 to 0.1 mol of alkylsiliconate per 100 g of dry copolymer. The alkylsiliconates preferably used are: - sodium methylsiliconate, in an amount of 4.8 to 1 6.3 parts by weight of dry methylsiliconate, and preferably of 6.4 to 9.8 parts, per 100 parts by weight of dry copolymer, and - a potassium methylsiliconate, in an amount of 5.6 to 19 parts by weight of dry methylsiliconate, and preferably of 7.44 to 11.4 parts, per 100 parts by weight of copolymer.

The waterproofing compositions of the invention can also contain various additives such as pigments, anti-foam agents (of the dimethylpolysiloxane oil type) for preventing the possible formation of foam following mechanical agitation, and in particular unsaponifiable coalescene agents such as the monobutyl ether of ethylene glycol or diethylene glycol or the phenyl ether of ethylene glycol, of propylene glycol or of dipropylene glycol, or products of the "white spirit" type having a small content of aromatic compounds, in order to lower, if necessary, the minimum film-formation temperature of the copolymer of vinylaromatic monomer and alkyl acrylate. The amounts of the said coalescence agents to be used can be of the order of 3 to 4 parts by weight per 1 00 parts by weight of dispersion of the said copolymer.

The new waterproofing compositions of the invention are very particularly suitable for waterproofing wood. The tern "wood" is understood as meaning both solid wood and wood derivatives such as chips, thin boards, plywood, laminated/glued structures, hardboard or chipboard and various composite articles based on cellulose materials.

For this particular application, the said water-proofing compositions can also contain up to 7% of the total weight of the said compositions of an active ingredient for protecting wood, of the fungicide and/or insecticide type.

The fungicides which may be present can be chosen from amongst those normally used for treating wood against attack by fungi, mildews and rot. Examples of insecticides which may be mentioned are: halogen derivatives of phenol, such as, for example, tetrachlorophenol and pentachlorophenol; metal salts, in particular copper, manganese, cobalt, chromium and zinc salts, derived from carboxylic acids such as, for example, heptanoic, octanoic and naphthenic acids; organic tin complexes such as, for example, bis-tributyltin oxide and tributyltin fluoride, phosphate, benzoate or acetate; methylene-bis-thiocyanate; mercaptobenzothiazole; and dichlorfluanid (N dichlorofluoromethylthio-N',N'-dimethyl-N-phenylsulphamide).

They can be present in amounts which can range up to 5% by weight, relative to the weight of the treatment composition; of course, this amount depends on the activity of the fungicide or fungicides used.

The insecticides which may be present can be chosen from amongst those normally used for treating wood against xylophagous insects. Examples which may be mentioned are organohalogen compounds such as, for example, DDT (dichlorodiphenyltrichloroethane), methoxychlor (dimethoxydiphenyltrichloroethane), lindane (hexachlorocyclohexane isomer), chlordane (octachlorohexahydromethanoindene), aldrin (endo-hexachlorohexahydrodimethanonaphthalene) and Toxaphene; organophosphorus compounds such as, for example, diethion (O,O,O',O'-tetraethyI-S,S'- methylenedithiophosphate), parathion (O,O-diethyl-paranitrophenylthiophosphate) and phosalone (0,0 diethyl-3-dithiophosphoryl methyl-6-chlorobenzoxazolone); carbamates such as, for example, Sevin (naphthyl N-methylcarbamate) and carbofuran (dimethyldihydrobenzofuranyl N-methylcarbamate); and synthetic pyrethrinoids such as, for example, decamethrin (a-cyanophenoxybenzyldibromovinvl dimethylcyclopropanecarboxylate), permethrin (phenoxybenzyl-cis/transdimethyldichlorovinylchloro- propanecarboxylate) and fenvalerate (cE-cyanophenoxybenzylchlorophenylmethylbutylbutyrate).

They can be present in amounts ranging up to 2% by weight, relative to the weight of the treatment composition; this amount of course depends on the activity of the fungicide or fungicides used.

A particularly advantageous active ingredient consists of the association (per 100 parts by weight of active ingredient) of: - 70 to 98 parts by weight of fungicide(s) consisting of: tetrachlorophenol and/or pentachlorophenol and/or an organic tin complex, if appropriate mixed with dichlorofluanid, with - 30 to 2 parts by weight of insecticide(s) consisting of: lindane and/or phosalone and/or Sevin and/or permethrin and/or fenvalerate.

The waterproofing compositions forming the subject of the invention, which optionally contain fungicides and/or insecticides as additives, have a solids content which can range from 2 to 50% by weight and preferably from 4 to 25%, depending on the nature of the surface to be waterproofed.

The present invention also relates to the process for the preparation of the waterproofing composition described above.

The said process consists in mixing the various constituents and, if appropriate, the various fillers and additives, observing the proportions indicated above.

The alkali metal alkylsiliconate is preferably introduced in the form of an aqueousa solution which can contain up to 50% by weight of solids.

The fungicides and insecticides which may be used are introduced into the aqueous medium consisting of the aqueous dispersion of copolymer and the alkali metal alkylsiliconate, either as such if they are liquid, or, preferably, in the dissolved state in an organic solvent or in a mixture of organic solvents.

Amongst the solvents which can be used, the following may be mentioned in particular: liquid aromatic hydrocarbons such as, for example, chlorobenzene, dichlorobenzene, toluene, xylenes or mixtures of aromatic hydrocarbons originating directly from petroleum distillation, such as kerosenes, which are distillation cuts boiling in the temperature range from 1 500C to 3000 C; monoalcohols such as, for example, cyclohexanol; glycols or polyols or their alkyl ethers, such as, for example, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, hexylene glycol, diglyme and butoxyethanol; aliphatic ketones such as, for example, ethyl amyl ketone and diisobutyl ketone; esters such as, for example, butyl or nonyl phthalate and dimethyl or diethyl succinate, adipate, oxaiate and malonate; and amides such as, for example, dimethylformamide or dimethylacetamide. It must be understood that it is possible to use a single solvent or a mixture of two or more than two solvents.

A very particularly advantageous method of introducting the active ingredient into the aqueous medium consisting of the aqueous dispersion and the alkali metal alkylsiliconate consists in introducing the said active ingredient by way of a liquid concentrate emulsifiable in water, the said concentrate comprising: - the active ingredient consisting of fungicide(s) and/or insecticide(s), and - a liquid dissolution medium consisting of at least one organic solvent for the active ingredient, an anionic surface-active emulsifying agent and, if appropriate, at least one oil and/or at least one fixing agent.

One type of liquid concentrate which is particularly suitable is that described in the French Patent Application published under No. 2,498,419; it comprises, per 100 parts by weight of concentrate: - from 1 5 to 40 parts by weight of active ingredient, - from 30 to 75 parts by weight of solvent(s) for the active ingredient, - from 0 to 20 parts by weight of oii(s) a d/or fixing agent(s), and -from 5 to 25 parts by weight of anionic surface-active emulsifying agent.

The surface-active agents forming part of the composition of the said liquid concentrate are chosen from amongst: a) sulphuric acid esters of the formula: R(OCH2CH2)nOSO3M (I) in which: - the substituent R represents a saturated or unsaturated hydrocarbon radical which can contain one or more heteroatoms and which is of aliphatic (linear or branched), cycloaliphatic or aromatic origin; - n represents a number fixed at a value such that the HLB of the surface-active agent corresponds to a number ranging from 10 to 16; and - M is a radical of inorganic or organic origin, chosen so that the surface-active agent is soluble in the concentrate to be emulsified and in water, and b) orthophosphoric acid esters of the formula:

in which: - the substituents R and n have the meanings given above in the formula (I); -- R, represents either a radical M, or one of the radicals R(OCH2CH2)n, it being possible for the radicals R1 and R-(OCH2CH2)n-to to be identical or different; and -- M, is a hydrogen atom or a radical having the meaning given above for M in the formula (I), it being possible for the two radicals M, (when R, = M,) to be identical or different.

The HLB (Hydrophilic/Lipophilic Balance) is a well-known parameter in the field of emulsifying agents. For further details, reference may be made to KIRK-OTHMER, Encyclopedia of Chemical Technology, 3rd edition, 1979, Volume 8, pages 910 to 915.

Preferably, the emulsifying agents are chosen from amongst those corresponding to the formulae I and II in which: - the substituent R represents: a linear or branched alkyl radical containing from 1 to 20 carbon atoms and optionally substituted by one or more alkoxy radicals containing from 1 to 5 carbon atoms or phenyl radicals; an alkylcarbonyl radical in which the alkyl radical corresponds to the definition given above; a cycloalkyl radical containing from 5 to 8 carbon atoms and optionally substituted as indicated above for the alkyl radical; or an alkylphenyl radical in which the linear or branched alkyl radical contains from 1 to 20 carbon atoms; - M (formula I) is an ammonium radical or an alkali metal atom; and -- M, (formula II) is a hydrogen atom, an ammonium radical or an alkali metal atom.

The expression "ammonium radical" is understood as meaning a compound of the formula: N(R2R3R4R5), in which R2, R3, R4 and R5, which are identical or different, represent hydrogen, alkyl radicals or hydroxylkyl radicals, it being possible for two of the alkyl radicals together to form a single divalent radical optionally containing an oxygen atom. The total number of carbon atoms in the ammonium radical is less than or equal to 6.

In this preferred group of emulsifying agents, the surface-active agents of the formulae (I) and (il) in which: - the substituent R represents: a linear alkyl radical containing from 6 to 20 carbon atoms; or an alkylcarbonyl radical in which the alkyl radical has a linear structure containing from 6 to 20 carbon atoms; - M (formula I) is an ammonium radical or a sodium atom; and -- M, (formula II) is a hydrogen atom, an ammonium radical or a sodium atom, are suitable.

Examples which may be mentioned are: a) in the case of the sulphates: CH3-(CH2) ,0CH2(OCH2CH2)nOSO3NH4 CH3-(CH2)10-CH2-(OCH2CH2)n-OSO3Na CH3-(CH2)11-CH2-(OCH2CH2)n-OSO2NH4 CH3-(CH2)12-CO-(OCH2CH2)n-OSO3NH4

with n ranging from 1 to 10.

b) in the case of the phosphates: CH3-(CH2)10-CH2-(OCH2CH2)n-OPO3(M1)2 [CH3(CH2),0CH2(OCH2CH2)n0]2PO2M, CH3(CH2)11CH2(OCH2CH2)OP03(M1)2 [CH3-(CH2)11-CH2-(OCH2CH2)n-O]2PO2M1

with n ranging from 1 to 10 and the various radicals M1, which are identical or different, representing the following in each of these compounds: H, NH4, NH2(C2H4OH)2, NH(C2H4OH)3, Na.

The solvents for the active ingredients which can be used are those already described above.

Amongst the oils which can be used to make up the dissolution medium, the following may be mentioned in particular: a vegetable oil such as, for example, linseed oil, soya oil, pine oil, tall oil or a mixture of terpineols; or a mineral oil such as, for example, spindle oil, which is a petroleum distillation fraction intermediate between kerosenes and paraffins.

Examples which may be mentioned of adhesives suitable for fixing the treatment agent to wood are: starch, carboxymethylcellulose, colophony or colophony esters, gum arabic, polyvinyl alcohol, humic acid, glycerophthalic resins and the so-called hydrocarbon resins composed of low polymers of unsaturated aliphatic and/or aromatic hydrocarbons derived from the cracking of petroleum fractions rich in indene.

The present invention also relates to the use of the composition described above for the waterproofing treatment of various surfaces of the types comprising facades made of hydraulic binder, tiles and wood.

The treatment of facades and tiles can be carried out in a particularly simple manner by applying the said composition, as such or after dilution with water, using a paint roller or by spraying with a pneumatic gun.

The amounts of composition to be deposited on these surfaces in order to obtain good waterproofing and protection are generally of the order of 20 to 80 g/m2. The treated substrate acquires waterproofing properties very rapidly, approximately one hour after application.

The processes used for applying the waterproofing composition, if appropriate containing a fungicidal and/or insecticidal active ingredient, to wood are those usually employed for treating wood and its derivatives, for example soaking, coating and the processes involving impregnation in an autoclave in vacuo and/or under pressure. A very suitable process in the so-called double vacuum process.

The amount of the said compositions used for treating wood depends on the chosen method of impregnation.

Thus, if the impregnation is carried out by soaking, the amount of composition used is of the order of 50 to 300 g/m2, expressed in g of total composition per m2 of surface to be treated. If the impregnation is carried out by surface coating, an amount of composition of the order of 20 to 80 g/m2 is sufficient. If the impregnation is carried out in an autoclave under a double vacuum, an amount of composition of the order of 8 to 40 kg/m3 is favourable.

The examples which follow illustrate the invention.

EXAMPLES 1 to 6 Preparation of the waterproofing composition The following are mixed: - 100 parts by weight of an aqueous dispersion of styrene/butyl acrylate copolymer having the following characteristics: weight ratio of styrenejbutyl acrylate: about 50/50 solids content: about 50% emulsifiers: sodium alkylsulphonate and oxyethyleneated alkylphenol catalyst: ammonium persulphate particle diameter: between 0.05 and 0.40 ,um minimum film formation temperature: 1 60C viscosity: 50 mPa.s (measured at 200C in a BROOKFIELD viscometer at 50 rpm) - and an amount, shown in Table I, expressed in parts by weight, flf an aqueous solution of potassium methylsiliconate having the following characteristics: solids content: about 47% specific gravity at 20'C: 1.34 alkalimetric strength: 18% (as K20) The viscosity of the mixture thus obtained in shown in Table I (meausred at 200C on a BROOKFIELD viscometer at 50 rpm).

Storage stability of the composition thus prepared No change in the viscosity is observed after storage for 1 year at ambient temperature.

Stability in an alkaline medium The composition prepared in Example 5 is heated at 400C for one month.

It is found that: - its viscosity has not changed, and - the proportion of saponified butyl acrylate, expressed in % by weight, relative to the weight of butyl acrylate, is less than 0.1% (measurement carried out by determination of the butanol released).

Waterproofing property of the film This property is determined by measuring the contact angle 0, in degrees, of droplets of water deposited on the surface of the sample to be tested (glass), according to the method described in "Physical Surfaces" by J.J. BIKERMAN -- Academic Press NY 1970, page 251.

The results of this measurement are shown in Table I.

EXAMPLE 7 A composition similar to that of Example 5 is prepared, the aqueous dispersion of styrene/butyl acrylate copolymer being replaced by a similar aqueous dispersion of styrene/ethyl acrylate copolymer having: a ratio of styrene/ethyl acrylate of: 41/59 a solids content of: about 50% a minimum film formation temperature of: about 1 60C The properties of this composition are shown in Table I.

Comparative examples 8 to 11 A composition is prepared which contains: - 100 parts by weight of an aqueous dispersion of a styrene/butyl acrylate/acrylic acid terpolymer having a weight ratio of styrene/butyl acrylate/acrylic acid of about 47/49/4, a solids content of about 50% and a minimum film formation temperature of about 1 60C.

- and an amount, shown in Table I, expressed in parts by weight, of the aqueous solution of potassium methylsiliconate described in Examples 1-5.

The properties of this composition are shown in Table I. It is observed that a composition of this type is difficult to use, or even unusable for the desired application, because of its excessive viscosity. TABLE l

Parts by weight Composition of dispersion Parts by weight viscosity in # in Example of of Me siliconate pH mpa.s degrees Styrene/Bu acrylate copolymer 1 100 0 7 about 50 55 2 100 2 11.8 " 67 3 100 5 12 " 72 4 100 7.5 12 " 93 5 100 10 12 " 95 6 100 20 13 " 96 Styrene/Et acrylate copolymer 7 100 10 12 " 95 Styrene/Bu acrylate/acrylic acid terpolymer 8 100 0 8 about 1,000 45 9 100 2.5 10 about 14,000* 60 10 100 5 > > 20,000* ** 11 100 10 solidified * Products which change and solidify during storage.

** Beyond the measurement capabilities of the instrument.

Product not spreadable by the conventional methods.

EXAMPLES 12 and 13 Preparation of the waterproofing composition The following are mixed: - 100 parts by weight of an aqueous dispersion of styrene/butyl acrylate copolymer having the following characteristics: weight ratio of styrene/butyl acrylate: about 50/50 solids content: about 50% emulsifiers: sodium alkylsulphonate and oxyethnyleneated alkylphenol catalyst: ammonium persulphate particle diameter: between 0.05 and 0.40 ,um minimum film formation temperature: 1 60C viscosity: 50 mPa.s (measured at 200C on a BROOKFíELD viscometer at 50 rpm) - 10 parts by weight of an aqueous solution of potassium methylsiliconate having the following characteristics: solids content: about 47% specific gravity at 200C: 1.34 alkalimetric strength: 1 8% (as K2O) - 3.5 parts by weight of butyldiglycol, - 0.1 5 part by weight of RHODORSIL 416 marketed by Rhone-Poulenc, as an anti-foam agent, - and water in an amount sufficient to obtain a solids content of 20% in Example 12 and 4% in Example 1 3.

Waterproofing test Pieces of chestnut wood, the dimensions of which vary from 40 x 1 5 x 4 mm to 60 x 30 x 6 mm (untapped bulk specific gravity of 0.15 to 0.2), are subjected to the controlled peripheral impregnation test according to French Standard Specification X 40-500 (page 26, paragraph 3.3.4).

A 20 litre autoclave, 1,500 g of pieces and the waterproofing composition prepared above are used.

a) the impregnation cycles are as follows: initial vacuum: 650 mbars for 10 minutes impregnation: 10 minutes final vacuum: 650 mbars for 45 minutes.

The amounts of composition absorbed per 100 g of wood are given in Table II.

b) water uptake cycles The pieces treated in this way are dried in the air for 4 days and then immersed in water for 2 hours.

The pieces are drained and the water uptake is measured by the change in weight. The results obtained are given in Table II.

c) washing-out tendency After the water uptake cycle, the pieces are dried again for 1 week and then immersed in water for 2 hours.

The pieces are drained and the water uptake is measured.

The results obtained are given in Table II.

This table also shows, by way of comparison, the results obtained on untreated (control) pieces and also on pieces treated with a 10% strength solution, in white spirit, of a silicone oil 47 V 100 marketed by Rhône-Poulenc.

It is found that: - the pieces treated with the silicone oil show a slight washing-out in cycle c), - the pieces treated with the composition forming the subject of the invention not only show no washing-out in cycle c), but also give further improved waterproofing, and swithin experimental limits, the influence of the solids concentration of the waterproofing composition on the water uptake seems to be small.

EXAMPLE 14 The waterproofing test described in Example 13 is repeated using a waterproofing composition containing 1 5 parts of potassium methylsiliconate solution instead of 10 parts, the said composition containing an amount of water sufficient to obtain a solids content of 4%.

The results of the waterproofing test are shown in Table II.

It is found that the waterproofing obtained is improved compared with that obtained in Example 2 EXAMPLE 15 Preparation of the waterproofing composition.

The following are mixed, per 1 00 g of total composition: 8.25% by weight of a waterproofing dispersion containing 48.5% of solids and prepared from: 100 parts of styrene/butyl acrylate latex used in Examples 12 and 13; 10 parts of methylsiliconate solution used in Examples 12 and 13; 3.5 parts of butyldiglycol; and 0.15 part of RHODORSIL 416; -- 9% by weight of an emulsifiable concentrate prepared from: 27.3 parts by weight of pentachlorophenol; 4.8 parts by weight of lindane; 22.7 parts of ortho-dichlorobenzene; 25.8 parts of hexylene glycol; 8.1 parts of an ester of colophony and pentaerythrol, marketed by the Company called Derives Résiniques et Terepéniques under the name DERTOLINEP; and 11.3 parts of an emulsifying agent of the formula: CH3-(CH2)11-CH2-(OCH2CH2)3-OSQNH4 - and 82.75% by weight of water, which corresponds to about: 4% of solids of waterproofing dispersion; 2% of pentachlorophenol; and 0.4% of lindane per 100 g of total composition.

The waterproofing composition prepared in this way is stable under normal use conditions.

Waterproofing test Test-pieces of Scotch pine, having a cross-section of 5 x 5 cm and a length of 30 cm, are immersed for 3 minutes in the composition prepared above.

The average absorption is about 30 kg/m3.

water uptake cycle The test-pieces are dried in the air for 4 days, immersed in water for 2 hours and then drained.

The water uptake observed is 12%.

The result of the same test carried out on untreated test-pieces is 20%.

washing-out cycle The test-pieces are then dried in the air for 1 week, immersed in water for 2 hours and then drained.

The water uptake of the treated test-pieces is 8%.

The water uptake of the untreated test-pieces is 25%.

Fungicide test Test-pieces of Scotch pine on the one hand and beech on the other hand are subjected to the test of French Standard Specification X 41-552, corresponding to European Standard Specification 113, which provides a basis for assessing a product for preserving wood against wood-eating basidiomycetes fungi.

It is found that the test-pieces treated with the above composition show average weight losses of less than 3% when they are exposed to attack by: Coniophora puteana Coriolus versicolor Poria placenta Gloeophyllum trabeum TABLE II

Untreated Control treated EXAMPLE control with 47 V 100 12 13 14 cycle a) absorption per 100 g of wood - N35 N60 N55 N55 cycle b) % increase in weight N55 N45 -25 N30 N30 cycle c) % increase in weight N65 N47 N20 N25 N20

Claims

1. A waterproofing composition comprising an aqueous dispersion of a film-forming copolymer of alkyl acrylate and a vinylaromatic monomer in an aqueous medium stable at basis pH, the said vinylaromatic monomer being such that the homopolymer corresponding to the said vinylaromatic monomer has a glass transition temperature of between 70 and 1 700 C, and an alkali metal alkylsiliconate in an amount of from 0.05 to 0.17 mol of alkylsiliconate per 100 g of dry copolymer.

2. A composition according to claim 1, in which the alkyl acrylate of the said copolymer is such that the corresponding homopoiymer has a glass transition temperature of between + 1 00C and 600 C.

3. A composition according to claim 1 or 2, in which the alkyl acrylate has an alkyl group containing from 1 to 8 carbon atoms.

4. A composition according to claim 3, in which the alkyl group contains from 1 to 4 carbon atoms.

5. A composition according to any one of the preceding claims, in which the vinylaromatic monomer is styrene or a methylstyrene.

6. A composition according to any one of the preceding claims, in which the copolymer of alkyl acrylate and vinylaromatic monomer has a glass transition temperature of between -50C and +250C.

7. A composition according to any one of the preceding claims, in which the aqueous dispersion of copolymer of vinylaromatic monomer and alkyl acrylate contains from 20 to 60% by weight of solids, with a particle diameter of between 0.05 and 0.5 ym.

8. A composition according to claim 7, in which the said aqueous dispersion of copolymer contains from 40 to 55% of solids.

9. A composition according to any one of the preceding claims, in which the alkylsiliconate is a sodium or potassium alkylsiliconate in which the alkyl group contains from 1 to 3 carbon atoms.

10. A composition according to any one of the preceding claims, in which the amount of alkylsiliconate present is 0.065 to 0.1 mol of alkylsiliconate per 100 g of dry copolymer.

11. A composition according to any one of the preceding claims, which contains from 2 to 50% by weight of solids.

12. A composition according to claim 11, which contains from 4 to 25% by weight of solids.

1 3. A composition according to any one of the preceding claims, which also contains up to 7% by weight of an active ingredient consisting of fungicide(s) and/or insecticide(s), based on its total weight.

14. A composition according to claim 13, in which the active ingredient consists of an association of: 70 to 98% by weight of fungicide consisting of: tetrachlorophenol and/or pentachlorophenol and/or an organic tin complex, if appropriate mixed with dichlorofluanid; with 30 to 2% by weight of insecticide consisting of lindane and/or phosalone and/or Sevin and/or permethrin and/or fenvalerate.

1 5. A composition according to claim 1 substantially as described in any one of the foregoing Examples 1 to 7 or 12 to 15.

1 6. Process for the preparation of a composition as claimed in any one of claims 1 to 12, which comprises mixing the aqueous dispersion of copolymer of alkyl acrylate and vinylaromatic monomer with the alkali metal methylsiliconate in aqueous solution, the said solution containing up to 50% by weight of solids.

1 7. Process for the preparation of a composition as claimed in claim 1 3 or 14, which comprises introducing the active ingredient in the liquid state, as such or dissolved in an organic solvent, into the aqueous medium consisting of the aqueous dispersion of copolymer and the alkali metal alkylsiliconate.

1 8. Process for the preparation of a composition as claimed in claim 13 or 14, which comprises introducing the active ingredient into the aqueous medium consisting of the aqueous dispersion of copolymer and the alkali metal alkylsiliconate, as a liquid concentrate emulsifiable in water, the said concentrate comprising: the active ingredient consisting of fungicide(s) and/or insecticide(s), and a liquid dissolution medium consisting of at least one organic solvent for the active ingredient, an anionic surface-active emulsifying agent and, if appropriate, at least one oil and/or at least one fixing agent.

1 9. A method of waterproofing and protecting surfaces which comprises applying thereto a composition as claimed in any one of claims 1 to 1 2.

20. A method of waterproofing and protecting wood which comprises applying thereto a composition as claimed in any one of claims 1 to 1 5.