DK157605B - PROCEDURE FOR PREPARING A STABLE SUSPENSION OF FINISHED SOLID PARTS IN THE OIL PHASE IN AN OIL-IN-WATER EMULSION, AS A PIGMENTED POTENTIAL - Google Patents

Description

DK 157605 B

The present invention relates to a process for preparing a stable suspension of finely divided solid particles in an oil-in-water emulsion. Thus, by this method, a stable suspension of solid particles in a liquid liquid can be provided. The invention is further explained in the following with reference to penetrating pigmented stains for the protection of wood and wood products, and which do not or only negligibly tend to lay or settle pigments or other suspended solid particles, but can e.g. also find application in the manufacture of pigmented paints, abrasives, polishes, cleaners etc.

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When applying stains to a porous surface, such as a wood surface, one of the conditions for obtaining good penetration is a relatively low viscosity of the liquid in relation to the rate of evaporation. Therefore, since in practice a short drying time is desired, the absolute viscosity must be low. If the stain is stained in whole or in part by pigment particles, these will, upon standing, settle according to Stoke's law, which is applicable in the practically interesting area, i.e., that the sedimentation rate is a function of particle size and viscosity. This means that the pickling must be subjected to vigorous agitation before use, which is why such agents are most often negotiated in buckets and the like with good agitation. If the stirring does not occur thoroughly enough, color defects occur with respect to hue and color strength when using the product.

There are several ways to address this problem:

The simplest method is to reduce the particle size to colloidal dimensions, so that the sedimentation becomes negligible even over long periods of time. This method can only be applied to specially expensive products, as preparing such a pigment dispersion is very costly.

Another widely used method is to flocculate the pigment by adding so-called "anti-bond additives", such as various polar compounds. This does not prevent the precipitation, but the precipitate becomes such that it can be particularly easily stirred again. In extreme cases, the pigment is then flocculated. strongly that the product can even be negotiated on cans that simply require a brief shake before use, however, in this flocculation of the pigment the treated surface gives a gritty, unattractive appearance and the penetration potential of the pigment itself is greatly reduced.

A third option, which is also applicable, is to make the viscosity shear force dependent and time dependent by the addition of agents which provide the rheological property termed thixotropy such as polyamide derivatives, colloidal silicic acid, etc. for pickling types based on organic solvents.

In this way, the viscosity can be kept high on standing while receiving it; for penetration favorable low value at the moment of application and for a very short period thereafter. This method limits - however, to cases where very high shear rates occur -

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forces at application, e.g. by brush application, and since the viscosity reduction in practice is very short-lived, does not allow for a sufficiently deep penetration.

The object of the present invention is to provide a method which does not suffer from the aforementioned disadvantages, whereby in the case of pickling a product with a good penetration and good protective effect can be obtained and which has no appreciable tendency to lay or settle the pigment itself. on long standing. More generally, it is the object of the invention to provide stable suspensions of finely divided solid particles in the oil phase in an oil-in-water emulsion with no tendency for appreciable precipitation.

This is achieved by the method according to the invention, characterized in that the finely divided solid particles are expelled in an oil phase in the presence of one or more dispersing aids which can make the surface oleophilic, and one or more sterically and / or electrostatically stabilizing dispersing agents for forming a stabilized suspension, after which it is emulsified in an aqueous medium in the presence of one or more emulsifiers known per se which are compatible with said dispersing agent (s) and aids. The particles are thus incorporated and retained in the inner phase by a stable oil-in-water emulsion, the outer continuous phase thus being constituted by a light flowing liquid.

Surprisingly, it has been found that by thus imparting suitable oleophilic surface properties to the particles, and partly providing appropriate steric and / or electrostatic forces between the particles between themselves and between the particles and the interface layer of the aqueous phase of the emulsion, stable suspensions can be obtained without or only with a extremely low tendency to settle the particles upon standing.

Methods which, upon immediate consideration, have certain similarities to the present invention, but which, upon closer analysis, are found to exhibit decisive differences, and which in particular do not aim or lead to products of the method according to the invention.

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long-term stability, is described in a number of printed matter:

De-OS 22 12 521 discloses a process for preparing an electrophoresis bath in emulsion form, under which, for example, a pigment suspension is added to a water-dissolved fully neutralized carboxylic acid. However, the precautions stated aim at retaining the pigment in the aqueous phase and the method does not aim at producing long-term stable products.

Swedish Patent No. 139 * 292 discloses a process for producing plastic emulsions which, e.g. are useful as glue or for fixing pigments on textiles. In Example 5, copper phthalocyanine blue is partitioned into a concentrated emulsifier solution, which is further added to emulsifier, water and an amino-plastic emulsion. This emulsion, thus not containing the pigment in the inner phase of the emulsion, as the aminoplast emulsion is prepared and added separately, is further thickened with an o. w-emulsion of gasoline in an emulsifier solution of the aforementioned kind. Again, the pigment is in no way expected to bind to the emulsion phase. The features of the invention are thus not present at all.

Swedish Ace No. 135 * 667 describes a process for preparing an emulsion concentrate to be diluted immediately before use, so long-term stability is immaterial. More specifically, the purpose is to prepare emulsions where water-insoluble protective agents are dissolved in the inner phase by a process in which their possible negative influence on the emulsion stability due to interaction with the outer phase is sought to be eliminated through a cumbersome step-by-step correction for these various electrical effects.

The possibility of dispersed active substances is not described in more detail anywhere, and nothing is mentioned about the conditions for possibly stabilizing a dispersed substance in the inner phase. Thus, there are no similarities with the features of the invention.

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DE-OS 22 56 757 describes a particularly emulsion-useful emulsion which can be both water-in-oil and oil-in-water type, and in which one particle of a substance with antibacterial insecticide is dispersed. herbicide or plant growth modifying effect.

These liquids are reportedly more stable than known products of the same kind, but the stability has only been documented for 48 hours, and it is particularly emphasized that the products are well redispersible, unlike the known products.

The characteristic of the spray liquid is partly that the density ratio and the volume ratio of the phases are set within defined limits and partly that one chooses a suitable nonionic or anionic surfactant which is hydrophobic or hydrophilic, depending on whether the particles are desired. must be in the oil or water phase.

It cannot be ruled out that for particles of substances of the kind mentioned in this way sufficient stability or at least redispersibility can be provided, but the inventor's experiments have shown that the said measures are completely insufficient for long-term stabilization of pigmented oil-in-water emulsions.

Thus, none of the aforementioned writings discloses the distinctive combination of a process of the invention that can make the particle surface oleophilic, a dispersant capable of stabilizing the inner phase of the emulsion, and a compatible emulsifier system capable of stabilizing the emulsion itself.

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Specifically, in an oil-in-water emulsion of the present invention, the retention of the particles in the inner phase and thus the stability of the suspension according to the invention can be provided as follows:

In order to obtain that the particles, for example the pigment particles, are made oleophilic, i.e. are wetted better by oil than by water, they are expelled according to the invention in the presence of suitable surfactants so that they are brought into this state, which is a prerequisite for incorporation into the oil phase itself. These agents are herein and hereinafter referred to as dispersing aids, and may, in the case of pigments, also be termed pigment humidifiers.

This can be done according to the invention by treatment with one or more surfactants selected from nonionic agents such as alkyl polyethoxylates and alkylaryl polyglycol ethers; ampholytic agents such as electron neutral salts of cationic and anionic groups, e.g. salts of fatty amines with fatty acids or polycarboxylic acids; anionic agents such as fatty alcohol sulphates, sulphimides, alkylaryl sulphonates, especially alkylbenzene and naphthalene sulphonates, phosphate esters, metal naphthenates and metal salts of fatty acids; and cationic agents such as quaternary ammonium compounds, alkylimidazole salts and lecithin. These agents can also impart to the individual particles an electrical surface charge which, if the initial potential (zeta potential) of the particle is not sufficiently large, contributes to an anti-flocculant effect due to electrostatic repulsion. Thus, e.g. the pigment particles from the manufacturing process or storage are often surrounded by a water membrane which, in order to obtain a good dispersion, must be displaced by the tearing in the presence of the surfactant (s). In addition to this change in the surface properties of the particles themselves, the resulting suspension of the particles in the oil phase of the invention can be further stabilized by adding agents which provide electrostatically acting forces between the particles during the tearing. These can be selected from the same types as the aforementioned oleophilizing dispersing aids, except for the nonionic ones.

However, it has been found that the best stability of the suspension

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sion is obtained if oil soluble agents are added to the oil phase during tearing which can also exert steric stabilization. Such agents are e.g. polar active surface soluble polymers such as polymers of oxidized unsaturated fatty acids and esters or ethers thereof, partially polymerized esters of polycarboxylic acids such as alkyds, and styrene, isocyanate and silicone modified versions thereof, acrylic modified and / or epoxidized oils and with amines and / or phenols, as well as polyethers and polyvinyl derivatives. It has been found that effective stabilization is usually first observed with polymers having a molecular weight of approx. 1500 and increases with increasing molecular weight up to approx. 10,000, after which the effect may decrease.

It should be noted that a number of the aforementioned types of surfactants exert both electrostatic and steric stabilization, as well as may affect the particle surface itself, so the same or more different surfactants may be used in addition to the dispersing aid.

The specific choice of surfactants depends, among other things, on the nature of the particles and the desired final product and can be determined by one of ordinary skill in the art by experiment. A preferred combination in the preparation of pigmented stains is a dispersing aid containing a cation-active hydrophobic group such as an amine, optionally in the form of an amine salt, especially with a hydrophobic anion (electron neutral salt), or in the form of an amine ester such as a lecithin. , in combination with a sterically stabilizing surfactant polymer discussed above.

It is essential for the favorable course of the process that the particles be incorporated into a stable emulsion. This stability is provided by the addition of one or more emulsifiers which produce steric and / or electrostatic forces between the individual particles of the inner phase (the oil phase) of the emulsion. In this connection, it is crucial that this stabilization of the emulsion does not occur at the expense of the stability of the suspension in the inner phase, which is why

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such emulsifiers are chosen which do not affect the stability of the oil phase induced by the dispersants and adjuvants.

These emulsifiers which may be of ionic or nonionic type may be added to one or both phases of the emulsion. For ionogenic (cat or anionic) types, electrostatic repulsion between the inner phase droplets plays a significant role in stabilization, whereas the effect of nonionic types mainly depends on steric repulsion and is far pH independent. Furthermore, the stability is influenced by the distribution of the surface active agent between the 2 phases, and especially for nonionic types, a so-called HLb value (hydrophilic-lipophilic balance) is often calculated to select the most suitable emulsifier for a given oil type.

To obtain electrostatic forces in stabilizing the emulsion, one or more surfactants acting in the outer phase and in the boundary layer of the inner phase, selected from ionic emulsifiers and protective colloids such as alkylaryl and alkyl sulfonates, amine, can be added. and metal salts thereof, such as calcium alkylarylsulfonates, carboxylic acids and polycarboxylic acids and their salts (soaps), such as polyacrylic acid salts with ammonia, amines and alkali metals, polyvinylcarboxylic acids and partial esters and / or salts thereof, cellulose salts and polycondensates and polycondensates , such as sodium hexametaphosphate and lithium polysilicate.

To obtain sterically acting forces in the stabilization of the emulsion, one or more ionogenic surfactants of the species and electrostatic stabilization listed above, such as fatty acid and fatty 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 thereof.

It has been found that a combination of a nonionic emulsifier with the correct HLL value (e.g., of the alkylphenol polyethylene oxide adduct type) added to the inner phase and a smaller amount of anionic surfactant of the type colloidal type, e.g. a poly-

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acrylate or a polyvinylmaleinate added to the outer phase is particularly suitable for stabilizing the emulsion itself, e.g. functions satisfactorily in suspending pigments in the inner phase of emulsions of vegetable oils and their synthetic analogs or derivatives thereof, and does not adversely affect particle stability in the inner phase. Said anionic component may also function to adjust an appropriate viscosity and to complex heavy metal ions which otherwise may contaminate the electrostatic stabilization, but these functions may also be performed by separate cationic, anionic or nonionic components, such as eg. sodium trip o lyphosphate.

The oil phase may also be added to one or more density-leveling agents, including light fluids such as aliphatic and aromatic hydrocarbons, to improve stability, especially when the suspension is used in a highly diluted state, where there may be a risk of stratification according to the invention. heavy liquids such as halogenated hydrocarbons, e.g. ethylene dichloride, tris-2,3-dibromopropyl phosphate, and chloro paraffins. Solids can also be added, e.g. light substances such as wax and microscopic hollow glass balls (microballoons), and heavy substances such as solid chloro paraffin and antimony trioxide. These can simultaneously serve as flame retardants.

As useful pigments, e.g. mention is made of oxides and highly soluble salts of alkaline earth metals and metals in the transition series, e.g. iron oxides, chromium dioxide, zinc oxide, barium sulfate, titanium dioxide, calcium carbonate, aluminum and magnesium silicate; other oxides and elements, e.g. silica, carbon black, aluminum powder and zinc dust, as well as organic compounds, e.g. heliogen green, phthalocyanine blue, benzide yellow and perylene red. However, the nature of the pigment is not critical to the invention.

Finally, for the oil or water phase, other protective substances of different kinds may be added which may also take the form of finely divided solid particles, e.g. biocides such as fungicides, e.g. tetrachloroisophthalonitrile, copper-8-hydroxyquinoline, tributyl-10

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tin oxide and its derivatives; preservatives such as sodium pyridine-thione-1 and 2,2-dibromo-glutarodinitrile; insecticides such as lindane or endosulfan, IR reflectors and special UV absorbents, as well as oil-soluble pigment binders, e.g. oxidatively drying possibly modified oils. However, it has surprisingly been found that the need for UV absorbents in the pigmented stains in question is very low as they result in a very good penetration and distribution of the pigment in treated wood surfaces.

To the aqueous phase can be added water-soluble or water-dispersible binders, e.g. polyacrylate dispersions, styrene-butadiene polymer dispersions, or polyvinyl acetate dispersions. Additionally, if desired, an oxidation catalyst (zincative) complexed in such a form that the equilibrium concentration of the free catalyst in the outer phase can be so small that the emulsion stabilization system is not appreciably affected, and optionally a stabilizer and / or a antioxidant for stabilizing the siccative.

The stable pigment suspensions of the invention have the additional advantage that they are suitable for obtaining reproducible color shades. In the coalescence of different-colored pigments in the oil phase, a co-flocculation has been previously observed which makes accurate and reproducible color tinting difficult. It has been found that by mixing finished pigment suspensions of the kind in question and by tearing the pigments in the oil phase of the process according to the invention, this co-flocculation is avoided and thus a desired color nuance can be obtained in a simple manner.

The mixing ratio of the constituents may vary within wide limits depending on the end product desired and not least the nature of the solid particles.

The 1ie-in-water emulsion may thus contain from 1-70% by weight. oil, but will usually contain approx. 20-30% by weight

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For the preparation of, for example, a pigmented stain, a paste of the following composition will usually be applied first: 1-75 parts by weight of pigment 0.1-10 "dispersing aid (pigment humidifier) 5-45" dispersant (stabilizer) 0-45 "density smoothing agent, where the slime of the constituents is 100 parts by weight.

To 50 parts by weight of this paste are added 0 - 650 parts by weight of pigment binder 10 - 50 "emulsifier (stabilizer for the emulsion), 0-5" sicative and stabilizer therefor.

0-10 "biocides and other excipients.

This oil phase is emulsified in an aqueous phase which may contain: 0.1 - 50 parts by weight stabilizer, which can also perform other functions (calculated as active substance) 0 -400 "pigment binder, but not more than 50% by weight.

of the aqueous phase, 0-10 "biocides and other excipients as well as demineralized water by 1000 parts by weight.

The invention is further illustrated by the following examples: EXAMPLE 1

Preparation of a pigmented stain.

When dispersing on a bead mill, an orange-red paste was prepared by tearing off 40 parts by weight of transparent iron oxide red (e.g., "VN 188", which is an orange-red hydrophilic pigment sold by Siegle & CoJ, 5 parts by weight of dispersing aid, (pigment humidifier) e.g. Disperbyk ", which is an electron neutral salt prepared by reacting an alkylolamine salt with a polycarboxylic acid, sold by Byk-Mallinckrodt, and 55 parts by weight 12

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soya oil repellent with an oil length of 65% (steric stabilizing dispersant for the pigment). The dispersion took place at ambient temperature to a particle size of maximum 20 µm.

50 g of this paste is mixed at ambient temperature for approx. 10 minutes with 200 g of 100% (solvent-free) linoleum oil oil length approx. 80% acting as a binder, 12 g of nonylphenol dodeca ethoxylate (steric stabilizing nonionic emulsifier), 1.2 g of cobalt naphthenate (6% Co-ciccative), 0.8 g of a 38% o-phenanthroline solution in butyl glycol "Activ 8 "- sold by Vanderbilt Corp. (stabilizer for siccative against hydrolysis) as well as 2 g of methyl ethyl ketoxime (volatile antioxidant acting as anti-skinning agent).

The 266 g mixture thus obtained, which may be perceived as a thin oil paint, is dispersed at ambient temperature and at a peripheral speed of 1.5 m / sec. for approx. 10 min. in a mixture of 210 g of demineralized water and 30 g of 15% poly (vinylmaleic acid alkyl glycol ester) ammonium salt ("Thickner LN"), which is anionic stabilizer, further acting as a complexing agent and protective colloid which is first mixed for approx. 5 min. with an additional 60 g of demineralized water. Thereby, 566 g of pigment dispersion is obtained, which has the character of an emulsion paint, and with stirring 434 g of demineralized water are added to which biocides and other protective agents may be added. ·

The stain thus obtained (1000 g) at 20 ° C has a viscosity of 12 cP, pH 7.8, density 1.083. It is inexpensive and easy to manufacture, has excellent penetration ability when applied to wood surfaces and does not cause any air pollution during use.

It is stable on standing and shows no tendency for the pigment to settle, even after a storage period of 14 months. The pickle also has excellent freeze-thaw stability. Thus, no changes to the product are observed after a standard test comprising three freezes to -18 ° C with intermediate thaws.

Similarly, stains have been prepared using pigments of other colors, such as "VN 088", yellow iron oxide pigment, and "VN 288" red iron oxide pigment, carbon black and phthaloic acid.

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13 cyanine blue, and other dispersing aids such as "Texaphor 963", electron neutral pigment humidifier, and lecithin, as well as other dispersing agents such as other alkyds, and other emulsion stabilizers (protective colloids) such as polyacrylates. Stains of the same excellent quality are obtained.

By comparison, identical stains have been produced, however, excluding the dispensing aid distinctive to the invention. In all cases, the pigments precipitated after a short time.

Furthermore, the protective effect of a number of stains made as stated above has been tested in the treatment of wood surfaces. Under accelerated weather conditions, the products in question have a surprisingly high degree of weather resistance. It has been found to exceed conventional pickling types on both the alkyd solvent basis and on the acrylic dispersion basis, under the same conditions as to the degree of pigmentation, binder concentration, etc.

EXAMPLE 2

Manufacture of pigmented stain.

When dispersing on a pearl mill, a black paste is prepared from 15 parts by weight of carbon black ("Printex 300"), 4 parts by weight of bentonite (thickening agent, 10% in mineral turpentine), 1 part by weight of dispersing aid ("Disperbyk"), 35 parts by weight of linoleum alkyd (dispersant). ) and 45 parts by weight of mineral turpentine (weight fill leveling agent).

50 g of this paste are treated analogously to the paste prepared in Example 1 and a stable pickle having a density of 1.03, pH 7.8 and viscosity 12 cP was obtained. This pickle also exhibits excellent penetration ability and is stable even at further large dilution.

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EXAMPLE 3

A polishing agent was prepared by tearing 1 part by weight of diatomaceous earth, 8 parts by weight of de-aromatized turpentine, 1 part by weight of alkyd, 0.1 part by weight of linoleyltrimethylenediamine dioleate (dispersant), 0.5 parts by weight of polyethylene glycol dioleate (PEG 400 dioleate), which was then emulsified in 89 4 parts by weight of water containing 0.0025 parts by weight of polyacrylic acid ammonium salt "Åcrysol A SE95" (anionic stabilizer). The odorless agent obtained was stable at prolonged standing with no tendency to precipitate.

Claims (14)

15 DK 157605 B L £ _LO-! LiLiLéJLi A process for preparing a stable suspension of finely divided solid particles in the oil phase of an oil-in-water emulsion, such as a pigmented stain, a pigmented paint, an abrasive or a polishing agent, characterized in that the finely divided solid particles are carefully rubbed into an oil phase in the presence of one or more dispersing aids which may render the particle surface oleophilic, and one or more sterically and / or electrostatically stabilizing dispersing agents to form a stabilized suspension, after which it is emulsified in an aqueous medium in the presence of one or more emulsifiers of such that they do not affect the stability of the oil phase induced by the dispersing agent (s) and dispersing aids mentioned. Process according to claim 1, characterized in that one or more surfactants selected from nonionic agents such as alkyl polyethoxylates and alkylaryl polyglycol ethers are used as oleophilizing dispersing aid; ampholytic agents such as electron neutral salts of cationic and anionic groups, e.g. salts of fatty amines with fatty acids or polycarboxylic acids; anionic agents such as fatty alcohol sulfates, sulfimides, alkylarylsulfonates, especially alkylbenzene and naphthalene sulfonates, phosphate esters, metal naphthenates and metal salts of fatty acids; and cationic agents such as quaternary ammonium compounds, alkylimidazole salts and lecithin, and as a stabilizing dispersant, one or more of the above surfactants or polar or surfactant soluble polymers, such as oxidized unsaturated fatty acids and esters or ethers thereof, are used. polymerized esters of polycarboxylic acids such as alkyds, and styrene, isocyanate and silicone modified versions thereof, acrylic modified and / or epoxidized oils and resins, aldehyde condensation products with amines and / or phenols, and polyethers and polyvinyl derivatives. DK 157605 B 16 Process according to claim 1 or 2, characterized in that as an oleophilizing dispersing aid, a compound containing a hydrophobic group of cation-active nature such as an amine is optionally used in the form of an amine salt, especially with a hydrophobic anion (electron neutral salt) or an amine ester. , such as lecithin, and as a dispersant, a sterically stabilizing surfactant polymer having a molecular weight of approx. 1500 - 10,000. Process according to claim 1, 2 or 3, characterized in that a nonionic emulsifier is added to the oil phase to stabilize the emulsion and to the aqueous phase a smaller amount of an protective colloid anionic surfactant. Process according to claims 1-4, characterized in that an agent is added to the oil phase which smoothes the density difference between the inner and outer phases. Process according to claims 1-5, characterized in that one or more pigments are used as finely divided solid particles. Process according to claim 6, characterized in that an oil-soluble pigment binder is additionally added to the oil phase. Process according to claim 7, characterized in that as an pigment binder an oxidatively drying optionally modified oil is used. Process according to claim 6, characterized in that a water-soluble or water-dispersible pigment binder is further added to the emulsion. Process according to claim 9, characterized in that an acrylic pigment binder is used. 17 DK 157605B Process according to any one of the preceding claims, characterized in that an oxidation catalyst (siccative) complexed in such a form is added that the equilibrium concentration of the free catalyst in the outer phase is so small that the stabilizing system of the emulsion is not affected. noteworthy of this. Pigmented stain, characterized in that it is made by the method of claims 1-11. Pigmented paint, characterized in that it is made by the method according to claims 1-11. A polishing or abrasive agent, characterized in that they are made by the method according to claims 1-3.