CA1112537A

CA1112537A - Method of preparing a stable suspension of micronized solid particles in the oil phase of an oil-in-water emulsion such as a pigmented stain

Info

Publication number: CA1112537A
Application number: CA281,295A
Authority: CA
Inventors: Aksel T. Bentsen
Original assignee: Gorivaerk As
Current assignee: Gorivaerk As
Priority date: 1976-06-25
Filing date: 1977-06-23
Publication date: 1981-11-17
Also published as: DK288676A; GB1589605A; DK157605C; SE7707189L; IE45347L; LU77594A1; BE856119A; ZA773814B; FR2355555A1; NO772204L; IT1081501B; AU515153B2; DE2728357A1; JPS531690A; FI771981A; AU2638877A; NZ184475A; NL7707039A; FR2355555B1; IE45347B1

Abstract

ABSTRACT OF THE DISCLOSURE
The disclosure describes a method of preparing a stable suspension of micronized solid particles in the oil phase of an oil-in-water emulsion. The micronized solid parti-cles are ground in an oil phase in the presence of one or more dispersion aids capable ? rendering the surface of the parti-cles oleophilic and one or more sterically and/or electrosta-tically stabilizing dispersion agents to form a stabilized suspension. Then the suspension is emulsified in an aqueous medium in the presence of one or more emulsifiers of a type that does not affect the stability of the oil phase produced by the dispersion agent or agents and dispersion aid or aids.
In this manner there is obtained, as far as stains are concerned, a product having good penetration ability and good protective effect.

Description

53~7 The present invention relates to a method of preparing a s-table suspension of micronized solid particles in an oil-in-wa-ter emulsion. This method thus provides a stable suspension of solid particles in a low-viscosity liquid. The invention will be explained in greater detail below with reference to penetrating pigmented stains for protection of wood and wood products, said stains showing no tendency or only a slight -tendency towards strati~ication or sedimen-tation of the pigments or other suspended solid particles, but may also be applied for example in the A` preparation of pigmented paints, abrasives, ~ili~h~
agents, cleaning agents, etc.
~' ' .
When applying stain to a porous surface, such as a wood surface, one of the conditions of obtaining good penetration is a relatively low viscosity of the liquid compared to the rate of evaporation.

In practice, a short drying time is desired, and the absolute viscosity must consequently be low. If the stain is coloured wholly or partly by means of pigment particles, these particles will precipitate on standing according to Stokes' law which applies approximately to the filed which is interesting in practice, i.e. that the rate of sedimentation is a function of particle size and viscosity. This implies that the stain must be strongly stirred before use, and such compositions are therefore usually sold in buckets and similar containers offerings good s-tirring possibility. If the stain is not sufficiently stirred, colour faults will

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occur with regard to the tint and colour intensity when the product is used.

It is known to obviate this problem in several ways:

The simplest me-thod is a reduction of the particle size to colloidal dimensions whereby the sedimentation will be insignificant even after long periods of time. Said method is only applicable to specific expensive products as the preparation of such a pigment dispersion is very costly.

Another, widely used method is flocculation of the pigmen-t by addition of so-called "anti~settlingagents", like various polar substances. By said method sedimentation is not eliminated, but the sediment will be of such a nature as to be particularly easily stirred up again. In extreme cases ' the pigment is ~locculated so strongly that the produc-t may ' ,even be sold in cans requiring only bri~ shaking be~ore use.
By said flocculation of the pigment, however, the treated sur~ace gets a grainy, unattractive appearance and the actual penetration possibilities o~ the pigment are greatly reduced.

A third possibility which is also used is to render the A~ è sh~r viscosity dependent on ~h~ force and time by addition o~
agents producing the rheological property named thixotropy 9 such as polyamide derivatives, colloidal silicic acid, etc.
for types of stain based on organic solvents. In this manner viscosity may be kept hlgh on stan_ing while attaining the ... , . . , . . , . .. . ,, ... ... . , : . . . . . ..

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low value favourable -to the penetration at the very moment of application and for a very short period thereafter. This method, however, is limited to the cases where very high shear forces arise during the application process, for example in applica-tion by brush, and provides no possibility o~ obtaining sufficiently deep penetration, as the lowering of viscosity is in practice of very short duration.

It is the object of the present invention to provide a method that does not suffer from the above-mentioned drawbac~s and where, as far as stains are concerned, a produc-t having good penetration ability and good protective effect can be obtained, said product showing no appreciable tendency towards stratification or sedimentation of the pigment even on prolonged standing. More generally, it is the object of the invention to provide stable suspensions of micronized solid particles in the oil phase of an oil-in-water emulsion without noticable tendency towards sedimentation.

This object is achieved by the method according to the invention which is characteristic in tha-t the micronized solid particles are ground in an oil phase in the presence of one or more dispersion aids capable of rendering the surface of the particles oleophilic and one or more sterical and/or electrostatically stabilizing dispersion agen-ts to obtain a stabilized suspension, after which said suspension is emulsifiéd in an aqueous medium in the presence of one or more emulsifiers of a -type that does not affect the stability of the oil phase product by said dispersion agent or agents 1~<~

and said dispersion aid or aids. Thus, the particles are incorporated and re-tained in the internal phase of a stable oil-in-water emulsion whose external continuous phase is thus composed of a liquLd of low viscosity.
.
It has thus surprisingly been found that partly by imparting suitable oleophilic surface properties to the particles and partly by providing suitable steric and/or electrostatic forces between the particles and between the particles and the bo~dary layer of the water phase of -the emulsion, stable suspensions may be obtained showing no tendency or only an extremely slight tendency towards sedimentation of the particles on standing.

Methods having, on the face of it, certain points of similarity to that described, but proving on close analysis to display decisive differences and which especially do not aim at or lead to products having the long-term stability obtainable by the method according to the invention are described in a number of publications:

German Offenle~un~sschrift No 22 12 521 describes a method of preparing an electrophoresis bath in emulsion form in which i.a. a pigment suspension in a water-dissolved completely neutralized carboxylic acîd is added to the bath.
However, the measures stated aim at re-taining the pigment in the water phase, and the method is not aimed at the preparation of products wlth long-term stability.

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Swedish Paten~ ,292 teaches a method of preparing resin emulsions applicable for example as glue or for fixation of pigments on -textiles. In Example 5 copper-ph-thalocyanine blue is distributed in a concentrated emulsifier solution to which is further added emulsifying agent, wa-ter, and an amino resin emulsion. Said emulsion, thus containing no pigment in the internal phase of the emulsion as the amino resin emulsion is prepared and added separately, is further thickened by an o/w emulsion of petrol in an emulsifier solution of the kind mentioned above. Neithe-r in this case must the pigment be expec+ed in any way to become incorporated in -the emulsion internal phase. The features characteristic of the inventi~n are thus not at all present here.

Swedish Paten-t No 135~66I teaches a me-thod of preparing an emulsion concentrate which must be thinned immediately before use, -and the long-term stability is consequently unimportant.
More exactly9 the object is to prepare emulsions where water-insoluble protectants are dissolved in -the internal ., phase by a me-thod which endeavours -to eliminate their possible negative impact on the emulsion stability on account of interaction with the external phase by means of a delica-te stepwise correction for these interactions.

The possibility of dispersed active substances is nowhere described more specifically, and there is no mention os the conditions of possibly stabilizing a substance in the internal phase agains-t sedimen-tationO Hence, there are no points of similarity to the characteristic features of the invention.

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5~3~7 German Offenle~ungsschrift No ?2 56 757 discloses an emulsion which is particularly applicable as spray and which may be of the water-i.n~oil -type as well as -the oil-in-water type, particles of a substance wi-th antibacterial, insecticide, herbicide or vegetation-modifying activity being dispersed in one phase.

These liquids are ostensibly more stable than known products of the same kind, however their stability has only been documented for ~8 hours, and it is particularly emphasized that the products are readily redispersible in contrast to the known products.

The specific feature of the spray is partly the adjustment of the density ratio and volume ratio between the phases within precisely defined limits, and partly the selection of a suitable non-ionic surfactan-t which is hydrophobic or hydrophilic, depending on whether the particles are desired to be present in the oil phase on in the water phase.

The possibility of establishing in this way, for particles of substances of the type mentioned, a stability or at least redispersibility sufficient for the purpose of application cannot be precluded, but the tests of the applicant have pro~ed tha-t said measures are quite inadequate for a long-term stability of pigmented oil-in-water emulsions.

Thus, none of the above-mentioned publications mention the combination characteristic of the method according to the .. ,, , .. . . . . ~ ~ , .. . . . . , . .. . . . . . . . . , . ~ ... . ... . . .... ... .. .

*~ 7 invention of a dispersion aid capable of rendering the particle surface oleophilic, a dispersion agent capable o~
stabilizing -the internal phase of -the emulsion, and an emulsifier system compatible therewith which is capable of stabilizing the emulsion i-tself.

In an oil-in-water emulsion of the kind described in the present invention -the retention of the particles in the internal phase and hence the stability of the suspension may be obtained, according to the invention, more specifically in the following manner:

To render the particles, for example the pigment particles, oleophilic, i.e. they are ~ by oil than by water, they are ground according to the invention in the presence of suitable surfactants so tha-t they are brough-t into said oleophilic state, which is a condition of the actual incorporation into the oil phase.

.
In this place and in the following these agents are called dispersion aids and may also, as far as pigments are concerned, be called pigment wetting additives According to the invention this may be effected by treatment with one or more surfactants selected from the group of non-ionic agents, such as alkyl polyethoxylates and alkyl arylpolyglycol ethers; ampholytic agents, such as electron-neutral salts of cation-active groups, e.g`. salts of fatty amines with fatty acids or polycarboxylic acids, anion-active agents, such as ~atty alcohol sulphates, sulfimides, alkyl-arylsulfonates, especially alkylbenzene sulfonates and alkyl naphthalene sulfonates, phosphate este~s, metal naphthenates and metal salts of fatty acids; and cation-activ~
agents, such as quaternary ammonium compounds, alkylimidazole salts and lecithin. These agents may also impart to the individual particles an electric surface charge which will contribute, if the original potential (zeta potential) of the particle is not sufficiently great, to an anti-flocculating effect owing to electrostatic repulsion. Thus, for example, the pigment particles from the preparatory process or the storing are often surrounded by a water film which must be displaced at the grinding process in the presence of the urfactant or surfactants to obtain good dispersion. In a~e~
addition to this ehff~ge'of the surface properties of the particles, the formed suspension of particles in the oil phase may be further s-tabilized according -to the invention by adding to the oil phase during the grinding agents producing electrostatically active forces between the particles~
These may be selected from the same types as the above-mentioned dispersion aids imparting oleophilic properties, apart from the non-ionic.

It has been found, however, that the best stability o~ the ~SF~n~o~
~pon~i~n is obtained if adding to the oil phase during the grinding oll-soluble agents which may also perform steric stabilization. Such agents are for example surface active soluble polymers with polar character, such as polymers of oxidized, unsatura-ted fa-tty acids and esters or ethers .

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thereof, partly polymerized esters of polycarboxylic acids, such as alkyds, and s-tyrene-, isocyanate- and silicone-modified ~arieties hereof, acryl-modiied and/or epoxidized oils and resins, aldehyde condensation products with amines and/or phenols, and polyethers a~ld polyvinyl derivatives.~It has been found that e~ective s-tabilization is generally first observed in polymers having a molecular weight of about 1500 and increases with increasing molecular welght up to about 10,000, after which the effect may diminis'n.

It should be noted that a number of the said types of sur-factants perform both electrostatic and steric stabilization, just as they may affect the particle surface itself, and according to circums-tances -the same or several di~feren-t surfactan-ts may therefore be used in addition to the dispersion aid.

The concrete selection of surfactants depends i.a. on the type of particles and the desired end product and may b~
determined by the person skilled in the art through tests. A
preferred combination in the preparation og pigmented stains is a dispersion aid containing a hydrophobic group of cation-active character, such as an amine, possibly in the ~or.m of an amine salt, especially wi-th a hydrophobic anion (electron-neutral salt), or in the form ofcn amine ester, such as a lecithin, in combination with a sterically s-tabilizing surface polymer mentioned above.
.

It is of vital importance to the favourable progress of the , ~ . ... ..... .. . . . . . . ... .. .. . .. ... . . . . . . . . . . . . . .. . . . . .

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of the method that -the particles are incorporated in a stable emulsion. This stability is provided by addition of one or more emulsifiers which produce steric and/or electrostatic forces between the individual particles of the internal phase (the oil phase) of the emulsion. In this connection it is of vital importance that said stabilization of the emulsion is not effected at the expense of the stability of the suspension in the internal phaseJ and it is therefore necessary to select emulsifiers that do not affec-t -the stability of the oil phase produced by the dispersion agents and dispers~on aids.

These emulsifiers, which may be of ionogenic or non-io-nic type, can be added to one or both phases o:E the emulsion. As far as ionogenic (cationic or anionic) types are concerned, the electrostatic repulsion between the internal phase drops is of substantial importance to the stabilization, while -the~
effect of non-ionic types depends primarily on steric repulsion and is extensively pH-independent. The stability is further affected by the distribution of the surfactant between the two phases, and especially in -the case oi non-ionic types a so-called HLb value (hydrophilic-lipophilic balance) is often calculated for selection of the emulsifier which is best suited for a given type of oil.

To obtain electrostatically activei forces in the stabilization of the emulsion there may be added one or more surfactants acting in the external phase and in the boundary layer to the internal phase and selected from the group of ionogenic .

emulsifiers and protective colloids, such as alkyl- aryl- and alkylsulfo~ates, amine and metal salts hereof, such as ~4 IGIU~ IKYI2~I ~ /40n~S~
1l~ar~aæulfonates, carboxylic acids and polycarboxylic acids and their salts (soaps), such as polyacrylic acid salts with ammonia, amines and alkali metals, polyvinyl carboxylic acids and partial esters :andtor salts thereof, cellulose derivatives as well as polycondensed inorganic acids and salts hereof, such as sodium hexametaphosphate and lithium polysilicate.

To obtain sterically acting forces when stabilizing the emulsion there may be added one or more ionogenic surfactants of the type described above under electrostatic stabilization and/or non-ionic agents, such as fatty acid- and fatt~ alcohol polyglycol ethers, polyethoxylated alkyl phenols, polycarboxylic acid esters and ethers, such as fatty alcohol succinates, sorbitol esters and ethers, sorbitan ether polyethoxylates, .
polyvinyl alcohols, polyethylene oxide and ethers and esters hereof as well as cellulose derivatives, such as hydroxyethyl cellulose.
. .
It has been found that a combination of a non-ionic emulsifier of the correct HLb value (for example of the alkylphenol polyethylene oxide adduct type) added to the internal pnase, and a minor amount of anionic surfactant of the protective colloid type, for example a polyacrylate or a polyvinylmaleinate, added to the external phase is particularly suitable for stab-ilization of the emulsion itself as it functions satisfactorily for example in the suspension of pigmen~ts in the in~ternal . -12-phase of emulsions of vegetable oils and their synthetic analogs or derivatives thereof and does no-t affect the particle s-tability in the inner phase adversely. Said anionic component may also act to adjust a suitable viscosity and for chelation of heavy metal ions ~Jhich may otherwise as contaminants destroy the electrosta-tic stabilization, however these functions may also be performed by separate components o~ cationic, anionic or non-ionic na-ture, such as sodium tripolyphosphate.

To improve stabili-ty, especially when the suspension is employed in highly diluted state involving a risk o~
stratification in the case of great differences in density, there may also according to -the invention be added to the oil phase one or more density-equalizing agents, including light liquids, such as aliphatic and aromatic hydrocarbons, and heavy liquids, such as halogenated hydrocarbons, for exarnple ethylene dichloride, tris-2,3-dibromo propylphosphate and chloro paraffins. It is also possible to add solid substances, for example light substances, such as wax and microscopic hollow glass balls (microballoons), and heavy substances, such als solid chloro paraffin and antimony trioxide. These may ser~e at the same time as flameretardan-ts.

Applicable pigments are ~or example oxides and insoluble salts of earth alkali metals and metals in the transition series, for example iron oxides, chromium oxides, zinc oxide, barium sulphate, titanium dioxide, calcium carbona-te, aluminium and magnesium silicate; other oxides and elements, ~or ~ . ...... , .. , .. .. . . . . ., ., , .. . ..... . . . . . , . . ., . , , . . ~

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example silicon dioxide, carbon black, aluminium powder and zinc dust, as well as organic compounds, ~or instance heliogen green, phthalocyanine blue, beMzidine yellow and perylene red. The type of pigment, however, is not critical to -the invention.

Finally, o-ther protec-tan~s of various kinds may be added to the oil or water phase, and -these may for exampLe also be in -the form of micronized solid particl.es, for instance biocides, such as fungicides, for example tetrachloroi.so-phthalonitrile, copper-8-hydroxyquinoline, -tributyl -~in oxide and derivatives thereof; preservatives, such as sodium pyridin-thion-l and Z,2 dibromoglutarodinitrile;
insec-ticides, such as lindane or endosulfane, IR-reflecting agents and specific W -absorbing agents, just as oil soluble pigment binders may be added to the oil phase, for instance oxidative drying, possible modified oils. However, it has surprisingly been found that the requirement for ~ ~ c;~ic W -absorblng agents in the pigmented stains described is very small as they cause extremely good penetration and distribution of the pigment in the trea-ted wood sur~aces.

1~

To the water phase can be added water soluble or water dispersible binders, for example polyacryla-te dispersions, styrene-butadiene-polymer dispersions or polyvinylacetate dispersions. If desired, there may also be added an oxidation catalyst (siccative) which is complexed in a form so that the equilibrium concentration of -the free catalyst in -the external phase is so small tha-t the stabilizing system of the emulsion is not affected noticeably hereby, and, if desired, a s-tabilizer and/or an antioxidant to stabilize the siccative.

The stable pigment suspensions prepared according to the invention present -the additional advantage that they are well suited for obtaining reproducible colour -tints. ~en co-grinding pigments of differen-t colours in the oil phase a co-~locculation has previously been observed, which impedes a precise and reproducible shading. It has been found that by mixing finished pigment suspensions of the type described as well as by grinding toge-ther the pigments in the oil phase by the method according to the invention, this co-floccula-tion is eliminated, whereby a desired tint can be obtained in a simple manner.
~' ' ' .
The mixture proportion between the constituents may vary within wide limits depending on the desired end product and not least on the kind of solid particles~

The oil-in-water emulsion may thus contain Prom 1 to 70 percent by weight of oil, but will usually contain from about 20 to 30 percent by weight.

~ i7 For preparing, by way of example, a pi~mented stain, a paste of the following composition will generally be ground first;

1 - 75 parts by weight of pigment 0.1-10 " " " " dispersion aid (pigment wetting agent)f 5 - 45 " " " - " dispersion agent tstabilizer) 0 - ~5 " " " " density-equalizing agent the sum of the consti-tuents being 100 parts by weight.

For 50 parts by weight of this paste the following is sub-sequently used:

.' 0 - 650 parts by weight of pigment binder 10 - 50 " " " " emulsifier (stabilizing agent ~or the emulsion) 0 - 5 " " " " siccative and stabilizer -therefor 0 - 10 " " " " biocides and other secondary materials.

This oil phase is emulsified in a water phase which may contain:
Il 0.1 - 50 parts by weight of stabilizer which may also perform other functions (calculated as active substance) 0 - 400 " " " " pigment binder, however not exceeding 50 percent by weight of the water phase, 0 - 10 " " " " biocides and other secondary materials as well as demineralized wa-ter up to 1000 parts by weight.

The in~ention is illustrated in greater de-tail by means of the examples stated below:

Preparation of a pigmen-ted stain.

By dispersion on a pearl mill there was prepared an orange paste by grinding 40 parts by weigh-t of transparent iron oxide red (e.g. "VN 188", which is an orange hydrophilic pigment sold by Siegle & Co.), 5 parts by weight of dispersion aid (pigment wetting agent) e.g. "Disperbyk", which is an electro-neutral salt prepared by reacting an alk~lol amine salt with a polycarboxylic acid, sold by ~yk-Mallinckrodt, and 55 parts by weight of soybean oil alkyd having an oil length of 65%
(sterically stabilizing dispersion agent for the pigment).
The dispersion took place at ambient temperature to a particle size of max 20 /u.

50 g of this paste was mixed at ambient temperature for about 10 minutes with 200 g of 100 percent (solvent-free) llnseed;
oil alkyd having an oi1 length of about 80% which acts as binder, 12 g of nonylphenoldodecaethoxylate (sterically stabilizing non-ionic emulsifier), 1.2 g of cobalt naphthenate ( 6% Co - siccative), 0.8 g of a 38% solution of o-phenanthroline in butyl glycol, sold by Vanderbilt Co. under the trade name "Activ 8'~(stabilizer for siccative against hydrolysis) as well as 2 g of methylethylketoxime (volatile antioxidant acting as anti-skinning agent).

The 266 g mixture thus obtained, which may be regarded as a fluid oil paint~ was dispersed at ambient temperature for about 10 minutes in a mix-ture of 210 g of demineralized water k Z53'7 and 30 g o~ 15% polyvinylmaleic acid alkylglycolesterammonium salt ("Thickner LN"), which is an anion1c stabilizer ac-ting also as chelating agent and thickener and which was ~irst mixed for about 5 minutes with another 60 g of demineralized wa-ter. By said process there was obtained 566 g of pigment dispersion having the character of anjemulsion paint to which was added while stirring 434 g of demineralized water, to which biocides and other protective agents rnay have been added.

The stain (1000 g) thus obtained has at 20C a viscosity of 12 cP, pH 7.8, specific gravity 1.083. It is easily prepared and at low cost, it has excellent penetration ability when applied to wood surfaces and causes no air pollution in use.
It is stable on standing and shows no -tendency towards sedi-mentation of -~he pigment, even after a storing period of: 14 months. The stain also has excellent freeze-thaw sta~ility.
For example, no product changes were observed after a standard test comprising 3 freezings to -18C with in-termediate thawings.

In the same manner stains have been prepared using pigments with other colours, such as "VN 088", yellow iron oxide pigment and "VN 288" red iron oxide pigment, carbon black and phthalocyanine blue, and other dispersion aids, such as "Texaphor 96~", electro neutral pigment wetting age~t~
and lecithin, as well as other dispersion agents, such as tall oil alkyds. Stains of the same excellent qualit~ were obtained.

,, .. , . , . ~ . . .. ,, . . ,, .. . .. . ., .,, . . . , , .... ... . ... , , ... ... ... . , , . , . . . , .
. . , , ~ ... . , . ,, , ~ . . .... . .. . . ... .

By way o~ comparison identical stains have been prepared, the dispersion aid characteristic of the invention, however, being omitted. In all cases the pigments were precipi-tated a~ter s-tanding for a short period.

.
The protective e~fect of a number of stains prepared as s-tated above for treatment of wood surfaces has also been tested.
Under accelerated test conditions as regards weather -the products described have exhlbited a surprisingly high degree of weather resistance and have i.a. proved to be superior to current types o~ stain on alkyd-solven-t base as well as on acryl dispersion base under otherwise identical condi-tions as regards degree o~ pigmentation, concentration of binder, etc.

Preparation of a pigmented stain.

By dispersion on a pearl mill a black paste was prepared from 15 parts by weight o~ carbon black ("Prin-tex 300"), 4 parts by weight of bentonite (thickener, 10% in white spirit), 1 part by weight of dispersion aid ("Disperbyk"~, 35 parts by weight of linseed oil alkyd (dispersion agent), and 45 parts by weigh-t o~ white spirit (density-equalizing gent3.

50 g o~ this paste was treated analogously with the paste prepared in Example 1, and there was obtained a stable stain having a speci~ic gravity of 1.03, pH 7.8, and viscosity 12 cP. Said stain also showed excellent penetration ability i~3~
and was stable even in case of great additional thinning.

A polish was prepared by grinding together 1 part by weight of diatomite, 8 parts by weight of dearomatized white spirit 1 part by weight of alkyd, 0.1 parts by weight of linoleyl-trimethylene diamine-dioleate (dispersion aid), Q.5 parts-by weight of polyethylene glycol diolea-te (PEG 400-dioleate), which was subsequently emulsified in 89.4 parts by weight of water containing 0.0025 parts by weight o~ polyacrylic acid ammonium salt "Acrysol ASE95" (anionic stabilizer). The obtained odourless composition was stable on prolonged stand-ing with no tendency towards sedimentation.

._ .
Preparation of a pigmented stain 15 parts by weigh-t of black pigment ("Printex 300") were ground analogously with Example 1 with 37.3 parts by weight of tall oil alkyd "S 84" (sterically stabilizing dispersion agent) 7 prepared by esterification of-tall oil fatty acids with pentaerythri-tol and 11% of isophthalic acid, 2 parts by weight of purlfied soybean lecithin (dispersion aid), 3 parts by weight of alkylphenolpolyglycol ether ("Wasc", sold by Berol Kemi)~ 6 parts of Bentonite paste (10% bentonite, 85% white spirit and 5% ethanol), 1.5 parts of methylethylketoxime and 35.2 parts of white spirit ("Varnolene").

r~l e ~k .

~ - - - - ........ .. ... .. .

Analogously, a blue paste was prepared from "Hostapermblau BFL" (phthalocyanine blue) and the same constituents in the same quantities except that there was used 44 parts by weight of "Varnolene" and 28.5 parts by weight of "S 84".

0.35 parts by weight of this black paste and 4.65 parts by weight of this blue paste were mixed in a Cowless dissolver for about 10 minutes in 20 parts by weight of "S 84", 2 parts by weight of "Wasc", 0.4 parts by weight of methylethyl-ketoxime, 0.25 parts by weight of "Co-activ" (which is a mixture of 40 parts by weight of "Activ 8", cf. Example 1, 20 parts by weight of cobalt naphthenate (18 percent C0) and 40 parts by weight of butylglyco~) as well as 1.8 parts of "N 54 D" which is a dispersion of 2,3,4,6-tetrachloroiso-phthalonitrile in a gl col ether.

Further, 20.9 parts by weight of water, 0.2 parts by weight of NH3 and 7.5 parts by weight of 33% "mickner LN" were mixed for 5 minutes.

me first prepared mixture was then poured into said mixture and was mixed for 8 minutes, after which 39.95 parts by weight of water and 2 parts by weight of monopropyleneglycol (freeze-thaw stabilizing agent) were added.

mere was obtained a dark blue pigmented stain having the same excellent properties as obtained in Example 1.

`"I`;

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A method of preparing a stable suspension of micronized solid particles in the oil phase of a low viscosity oil-in-water emulsion, wherein the micronized solid particles are ground in an oil phase in the presence of one or more dispersion aids capable of rendering the surface of the particles oleophilic and one or more sterically and/or electrostatically stabilizing dispersion agents to form a stabilized suspension, after which said suspension is emulsified in an aqueous medium in the presence of one or more emulsifiers of a type that does not affect the stability of the oil phase produced by said dispersion agent or agents and dispersion aid or aids.

2. A method according to claim 1, wherein said dis-persion aid imparting oleophilic properties comprises one or more surfactants selected from the group of non-ionic agents, ampholytic agents, anion-active agents, and cation-active agents; and said stabilizing dispersion agent comprises one or more of the above-mentioned surfactants or one or more surface active soluble polymers with polar character.

3. A method according to claim 2, wherein said non-ionic agents are selected from the group consisting of alkyl-polyethoxylates and alkylarylpolyglycol ethers, said anion-active agents are selected from the group consisting of fatty alcohol sulfates, sulfimides, alkylarylsulfonates, phosphate esters, metal naphthenates and metal salts of fatty acids;
said cation-active agents are selected from the group consist-ing of quaternary ammonium compounds, alkylimidazole salts and lecithin; said surface active soluble polymers with polar character are selected from the group consisting of polymers of oxidized unsaturated fatty acids and esters or ethers thereof, partly polymerized esters of polycarboxylic acids, acryl-modified and/or epoxidized oils and resins, aldehyde condensation products with amines and/or phenols and polyethers and polyvinyl derivatives.

4. A method according to claim 3, wherein said alkyl-arylsulfonates are selected from the group consisting of alkylbenzene sulfonates and alkylnaphthalene sulfonates.

5. A method according to claims 3 or 4, wherein said partly polymerized esters of polycarboxylic acids are selected from the group consisting of alkyds, and styrene-, isocyanate-, and silicone-modified varieties thereof.

6. A method according to claim 1, wherein said dis-persion aid imparting oleophilic properties comprises a compound containing a hydrophobic group of cation-active character, and said dispersion agent comprises a sterically stabilizing surface active polymer having a molecular weight of from about 1500 to 10,000.

7. A method according to claims 1 or 2, wherein said dispersion aid imparting oleophilic properties comprises a compound containing a hydrophobic group of cation-active character selected from the group consisting of an amine, an amine salt, an amine salt with a hydrophobic anion (electroneutral salt) and an amine ester.

8. A method according to claims 1 or 2, wherein said dispersion aid imparting oleophilic properties comprises lecithin.

9. A method according to claim 1, wherein a non-ionic emulsifier is added to the oil phase for stabilization of the emulsion and a minor amount of an anionic surfactant of the protective colloid type is added to the water phase.

10. A method according to claims 1, 2 or 9, wherein an agent equalizing the difference in density between the internal and external phases is further added to the oil phase.

11. A method according to claim 1, wherein one or more pigments are used as micronized solid particles.

12. A method according to claim 6, wherein an oil soluble pigment binder is further added to the oil phase.

13. A method according to claim 7, wherein an oxidative drying, possibly modified oil is used as pigment binder.

14. A method according to claim 6, wherein a water soluble or water dispersible pigment binder is further added to the emulsion.

15. A method according to claim 9, wherein a pigment binder on acrylic base is used.

16. A method according to any one of claims 1, 2 or 9, wherein there is further added an oxidation catalyst (siccative) which is complexed in a form so that the equilibrium concentra-tion of the free catalyst in the external phase is so small that the stabilizing system of the emulsion is not noticeably affected hereby.

17. A method of preparing a stable pigmented stain com-prising the steps of:
grinding 1-75 parts by weight of a micronized pigment in the presence of 0.1-10 parts by weight of one or more dis-persion aids capable of rendering the pigment surface oleophilic, 5-45 parts by weight of one or more sterically and/or electro-statically stabilizing dispersion agents, and 0-45 parts by weight of a density equalizing agent, to obtain a pigment paste, mixing 50 parts by weight of said paste with 0-650 parts by weight of a pigment binder, 10-50 parts by weight of one or more emulsifiers which do not adversely affect the stabilization produced by the dispersion aid or aids and dispersion agent or agents, 0-5 parts by weight of a siccative and a stabilizer therefor, and 0-10 parts by weight of biocides and other secondary materials to obtain a stabilized dispersion of the pigment in an oil phase, emulsifying said oil phase in a water phase compris-ing 0.1-50 parts by weight of stabilizer which does not adversely affect the stability of the oil phase, 0-400 parts by weight of a pigment binder, however not exceeding 50 parts by weight of the water phase, 0-10 parts by weight of biocides and other secondary materials, and water in an amount adding up to a total of 1000 parts by weight.

18. A method according to claim 17, wherein the dis-persion aid is lecithin, the dispersion agent is alkyd, the emulsifier is an alkylphenolpolyglycol ether and the stabilizer is a polyvinylmaleinate.

19. A stable suspension comprising micronized solid particles in the oil phase of an oil in-water emulsion, one or more dispersion aids capable of rendering the surface of the particles oleophilic, one or more sterically and/or electrostatically stabilizing dispersion agents and one or more emulsifiers of a type that does not affect the stability of the oil phase produced by said dispersion agent or agents and dispersion aid or aids.

20. The suspension of claim 19, with the proviso that the oil-in-water emulsion contains from about 20 to about 30 percent by weight of oil, based on the weight of the entire composition.

21. A stable pigmented stain comprising micronized pigment particles in the oil phase of an oil-in-water emulsion, one or more dispersion aids capable of rendering the surface of the pigment particles oleophilic, one or more sterically and/or electrostatically stabilizing dis-persion agents and one or more emulsifiers of a type that does not affect the stability of the oil phase produced by said dispersion agent or agents and dispersion aid or aids.

22. The stain of claim 21, with the proviso that the oil-in-water emulsion contains from about 20 to about 30 percent by weight of oil, based on the weight of the entire composition.