MXPA96002922A - Microemulsions of polymers exempt from - Google Patents

Abstract

The present invention relates to a method for preparing organopolysiloxane microemulsions, achieved by the copolymerization of a cyclic siloxane and a polyfunctional silane, in an aqueous medium containing a nonionic surfactant, an anionic or cationic surfactant and a catalyst, until obtaining the desired increase in molecular weight. The invention lies in controlling the gel content of the organopolysiloxanes in the microemulsion by controlling the concentration of silane and the concentration of the silanol in the resulting organopolysiloxane, such that the ratio of functionality results in the formation of a molecular weight distribution. of the gel-free polymer of finite organopolysiloxane species in the microemulsion

Description

MICROEMULSIONS OF GEL EXEMPT POLYMERS BACKGROUND AND FIELD OF THE INVENTION The present invention is directed to microemulsions of gel-free polymers and to a method for preparing polysiloxane emulsions using what is commonly known as emulsion polymerization. The microemulsions are produced from a mixture of a siloxane oligomer, a water-soluble, hydrolyzable alkoxysilane, a cationic or anionic surfactant, a non-ionic surfactant, a catalyst and water. The reagents containing silicon react in the presence of water and surfactants to form polysiloxane emulsions. By using the present method, it is possible to produce microemulsions of gel-free polymers. DESCRIPTION OF THE INVENTION The present invention is an improvement of methods described in EP-A 0 459 500, published on December 4, 1991 and designated to the agent of the present invention. Although similar techniques for preparing microemulsions are shown therein, it is not explained how to avoid gel formation of the non-linear siloxane polymers. Polysiloxane emulsions are classified by the size of the polysiloxane particles and the appearance of the emulsion. The material recognizes three categories of silicone emulsions, (i) standard emulsions, (ii) fine emulsions and (iii) microemulsions. Standard silicone emulsions have a large particle size greater than 300 nanometers and for the human eye appear to be opaque and impenetrable to light. Standard silicone emulsions have an intense white appearance. The thin silicone emulsions have a smaller particle size of 140 to 300 nanometers and visually are slightly opaque to very slightly translucent. Fine emulsions transmit light but with distortion. Silicon microemulsions have a particle size of less than 140 nanometers and visually appear translucent to transparent and transmit light without distortion. The most desired are the microemulsions due to their smaller particle size, greater stability and their translucent to transparent appearance.

The emulsions of the polysiloxanes in water are prepared mechanically or by means of. emulsion polymerization. Mechanically it means taking the preformed polysiloxane and using a mechanical apparatus such as a homogenizer or vigorous stirrer to emulsify the siloxanes in water. A surfactant can be added to either the polysiloxane or water to aid in the emulsification process.

The emulsion polymerization, to which the present invention pertains, comprises combining reagents containing silicone, surfactants, polymerization catalyst and water. This mixture is stirred and the reagents containing silicone are allowed to polymerize until a microemulsion is formed. Alkoxysilanes, cyclic siloxanes and combinations of alkoxysilanes and cyclic siloxanes are used as reagents to form the microemulsion.

Although the techniques in EP-A 0 459 500 have been quite successful in the production of suitable microemulsions of linear siloxane polymers, they do not prevent gel formation of the polymer when the production of a microemulsion of siloxane polymer is desired. non-linear This is the essence and contribution of the present invention.

This invention introduces a composition and a process for producing polysiloxane microemulsions containing a molecular weight distribution of the gel-free polymer. According to the present process, the polyfunctional alkoxysilanes and the permethylcyclic siloxanes are copolymerized in the presence of nonionic, anionic or cationic surfactants. A molecular weight distribution of the gel-free polymer is observed within a specific range of the functionality ratio, with the proviso that the polyfunctional monomer is dispersed through the polymer in a very random relationship. The functionality ratio f is the molar ratio of the initial polyfunctional syllable to the total remaining syllable.

The present process is illustrated by reference to the following three schemes wherein DBSA is dodecylbenzenesulfonic acid: (I) Alcoxysilane Alkylsilane Triol Branched Unit (II) shown later as Siloxane Cyclic Siloxane Finished by Silanol (III) (I) (I) Gel Exempt Finite Polymer Species The concentration of the polyfunctional monomer (alkoxysilane) is controlled by the initial charge of the ingredients to the reactor (model), while the concentration of the silanol is controlled by the prevailing reaction temperatures or effective and particle sizes. The specific functionality range, which results in a molecular weight distribution of the gel-free polymer of "finite" polymer species is theoretically defined in relation to a gel point or a point of incipient heterogeneity in the molecular weight distribution of the polymer . The relation of functionality in the gel point fg is defined theoretically as: theoretical fg = p / (l-Pg) p and Pg are in turn defined by the following equation where ag has the value of 0.5. A) Yes: ag = 0.5 = Pg p l-Pg (l-p) where: ag is the branch coefficient that relates to the structure of the polyfunctional monomer, present in the formulation) with respect to the initial total silanol (ie complete hydrolysis of all the alkoxysilane groups present in the formulation plus the complete hydrolysis of all the cyclosiloxane species), and Pg is the molar conversion of the silanol at the gel point or the moles of the total = SiOH consumed at the gel point divided by the initial total silanol.

It is understood that the simplest theoretical prediction of the gel point requires that all condensation reactions are intermolecular and the reactivities of HO (Me2SiO) H and MeSi (OH) 3 are the same. In view of both of these requirements apply equally to the emulsion copolymerization of a permethylcyclic siloxane and a polyfunctional silane, f can be determined empirically from the following equation: f observed SiOH (MWRnSÍO (-n) / 2) where; f is the silane functionality, ie 3 for MeSi (OMe) 3 and 4 for Si (OEt) 4.

The brackets J are units of concentration (w / w) for Rn SiO (-n) / 2 and SiOH, MWSiOH is the number average molecular weight of silanol, MWRnSiO (4-n) / 2 is the number-average molecular weight of the branched site, n is 0 or 1, and R is CH3-, CH3 (CH2) 2-, CH3 (CH2) 7- or CH3 (CH2) u-, for example.

If the functionality ratio f is less than the functionality ratio at the gel point fg, the molecular weight distribution of the polymer will be gel-free (unimodal) and will contain only "finite" species. If the functionality ratio f is in the functionality ratio at the gel point fg, the molecular weight of the polymer will not be gel-free (unimodal); but it will contain a fraction of the soluble polymer and a gel fraction (bimodal). Since the functionality ratio f increases beyond the functionality ratio at the gel point fg, the gel fraction will become more predominant until a complete network or mesh is formed. The average size of the mesh will be confined or limited by the average diameter of the polymer particles.

It is not considered that the functionality ratio f has been previously used for the control of the gel content, ie, the molecular weight distribution of non-linear silicone emulsion polymers. According to the present invention, the relative speed at which the two monomers of (alkoxysilane and cyclic siloxane) are introduced into the reactor is not critical, as long as the irreversible homopolymerization of the polyfunctional monomer (alkoxysilane) does not occur. The functionality ratio f of a highly non-random copolymer would have an unpredictable value. It is considered that the unique extremely high surface area for the microemulsions facilitates mass transfer of the water-soluble siloxane species between the particles, thereby providing a mechanism for a rapid redistribution of the siloxane within the entire system. Thus, if the reversible homopolymerization of polyfunctional monomer occurs, the rearrangement reactions will ensure a random distribution of the branching within the polymer.

Due to the reversible nature of ionic siloxane polymerizations, a slightly cross-linked siloxane gel in the form of a microemulsion can be rearranged to form 100% sol. For purposes of this application, the term "sol" is used in the sense of denoting a finite polymer species, ie, gel-free. "This is accomplished by manipulation of the polymerization temperature. The equilibrium concentration of the silanol in the polymer is directly proportional to the reaction temperature, so f is inversely proportional to the reaction temperature, if a given group of process conditions results in f being greater than fg, then f can be reduced to a value less than fg by simply increasing the reaction temperature after all the microemulsion particles have formed.The ability to recover the sun would, of course, depend on the physical parameters or constraints of the system. a reaction temperature of 200 ° C would be completely impractical.

The viscous dissipation factor of gel-free non-linear emulsion polymers is greater than that of similar viscosity polymers containing a gel fraction. Therefore, gel-free polymer emulsions are useful in applications that require lubricating properties without excessive tackiness. For example, anionic or cationic emulsions of gel-free, but high-viscosity branched, silicone polymers are useful as hair conditioning agents.

Generally the present method comprises preparing microemulsions containing particles with a size of 25 to 70 nanometers (0.025-0.070 microns), using a nonionic and a cationic or anionic surfactant, cyclic siloxane monomers such as octamethylcyclotetrasiloxane and alkyltrialkoxysilanes or tetralkoxysilanes of 1 to 12 carbon atoms. With a molar ratio of silane to cyclic siloxane of 0.0001-0.02, a polymer with a viscosity of 1,000 to 5,000,000 centistokes (MI / s) can be produced. f must vary from 0.0001 to the gel point fg determined experimentally.

The emulsions of this invention are prepared from a siloxane oligomer, a water-soluble hydrolyzable alkoxysilane, either a cationic or anionic surfactant, a non-ionic surfactant, a catalyst and water. In some cases, an anionic surfactant can also act as a catalyst thereby eliminating the need for a catalyst. In other cases, some cationic surfactants have non-ionic characteristics, eliminating the need for a non-ionic surfactant.

Polymerization, according to the method of the present invention, involves opening a cyclic siloxane ring using an acidic or basic catalyst in the presence of water. When the ring is opened, the polysiloxane oligomers with hydroxy end groups are formed. These polysiloxane oligomers then react with each other or with another reagent containing silicone in the reaction medium, through a condensation reaction to form polysiloxane polymers or copolymers.

The siloxane oligomers are cyclic siloxanes of the formula: wherein each R is a saturated or unsaturated alkyl group of 1 to 6 carbon atoms, an aryl group is 6 to 10 carbon atoms and x is 3 a. R may optionally contain a functional group which is non-reactive at ring opening and in the polymerization reaction.

Suitable R groups are methyl, ethyl, propyl, phenyl, allyl, vinyl and -R F. R is an alkylene group of 1 to 6 carbon atoms or an arylene group of 6 to 10 carbon atoms and F is a group functional such as an amine, diamine, halogen, carboxy or mercapto. R may also be -R1F1R wherein R1 and R are as defined above and F1 is an atom other than carbon, such as oxygen, nitrogen or sulfur.

Cyclic siloxanes useful in our invention include compounds such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethyltetravinylcyclotetrasiloxane, tetramethyltetraphenyl cycletotetrasiloxane and mixtures thereof.

Copolymers were prepared in our emulsion polymerization reaction to have a small portion of other reagents containing silicone present in the reaction medium. These reagents can be any compound that contains a hydrolysable group or silanol and that is capable of polymerizing in emulsion. The other reagents must be water soluble and included at a level less than 2 mole percent of the total silicone content.

Examples of other silicon-containing reagents include organofunctional siloxanes such as polysiloxanes blocked at their end with hydroxy, exemplified by polydimethylsiloxanes terminated with silanol with a degree of polymerization between 1 to 7.

Most preferred, however, are the water-soluble alkoxysilanes RSi (OR ') 3 or (R') 4Si wherein R is an organic group, preferably containing from 1 to 12 carbon atoms, such as an unsubstituted alkyl group CnH2n +? or an aryl group. R 'is a hydrolysable group and - (OR') is an alkyl group containing from 1 to 6 carbon atoms. The silanes RSi (OR ') 3 are therefore alkoxysilanes with organic neutral groups R.

Tetraalkoxysilanes (R'0) 4 Si are best exemplified by tetramethoxysilane, tetraethoxysilane, tetrapropoxy silane and tetrabutoxy silane, Water-soluble, hydrolysable RSi (OR ') 3 alkoxysilanes with neutral organic groups R are exemplified by methyltrimethoxysilane, ethyltrimethoxysilane, propyltri-methoxysilane, n-butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxy-silane, dodecyltriethoxysilane and phenyltrimethoxysilane.

Water-soluble alkoxysilanes RSi (0R ') 3, with groups R cationic organofunctionals and exemplified by aminofunctional silanes are not included in our invention.

The emulsions of the present invention contain a silicone concentration of 10 to 70% by weight of the total emulsion solution, preferably 25 to 60% by weight. Although emulsions with less than 10% silicone content can be prepared, such emulsions maintain little or no economic value.

The reaction for polymerizing our silicon-containing reagents and forming emulsions is carried out in a reactor containing a reaction medium of water, at least one cationic or anionic surfactant, at least one nonionic surfactant and a catalyst. Any catalyst capable of polymerizing cyclic siloxanes in the presence of water is useful in our method. The catalysts include condensation polymerization catalysts capable of cleaving siloxane bonds, for example strong acids such as substituted benzenesulfonic acids, aliphatic sulfonic acids, hydrochloric acid and sulfuric acid: and strong bases such as quaternary ammonium hydroxides and metal hydroxides. Surfactants such as dodecylbenzenesulfonic acid (DBSA) can additionally function as catalysts. Other useful catalyst systems include phase transfer catalysts such as tetrabutylammonium hydroxide or cation exchange resins wherein the catalysts are formed in situ.

The catalyst is present in our reaction medium at levels of 0.01 to 30% by weight of the total silicone. Strong acids and basic metal hydroxides may be within the lower end of this range, while surfactants that also function as catalysts will be present in concentrations above the upper end of the range.

It is important that the reaction medium contains both anionic and nonionic surfactants to stabilize the polysiloxane in the emulsion. The ionic surfactants can be cationic or anionic, both surfactants are known in the art as useful in emulsion polymerization.

Suitable anionic surfactants include but are not limited to sulfonic acids and their salt derivatives. Useful anionic surfactants are alkali metal sulfosuccinates, esters or sulfonated glyceryl fatty acids such as sulfonated monoglycerides of coconut oil; salts of sulfonated monovalent alcohol esters such as sodium oleyl isothionate; amides of amino sulfonic acids such as the sodium salt of oleyl methyl tauride, sulphonated products of nitrile fatty acids such as palmitonitrile sulfonate; sulfonated aromatic hydrocarbons such as sodium alpha-naphthalene monosulfonate, condensation products of naphthalenesulfonic acids with formaldehyde; sodium octahydro anthracene sulfonate; alkali metal alkyl sulphates; ether sulfates having alkyl groups of eight or more carbon atoms; and alkylaryl sulfonates having one or more alkyl groups of eight or more carbon atoms. commercial anionic surfactants useful in the present invention include dodecyl-benzenesulfonic acid (ADBS) sold as BIOSOFT® S-100 by Stepan Company, Northfield Illinois); and the sodium salt of dodecylbenzenesulfonic acid sold as SIPONATE® DS-10 by Alloys Inc., Baltimore, Maryland.

Useful cationic surfactants are the various fatty acid amines, amides and derivatives and salts of amines and fatty acid amides. Cationic surfactants are exemplified by fatty aliphatic amines and derivatives such as dodecyl amine acetate, octadecyl amine acetate and tallow fatty acid amine acetates; the homologs of aromatic amines that have fatty chains of dodecyl aniline; fatty amides derived from aliphatic diamines such as undecyl imidazoline; fatty amides derived from di-substituted amines such as oleylamino diethylamine; ethylenediamine derivatives; quaternary amino compounds such as tallow trimethylammonium chloride, dioctadecyldimethylammonium chloride, didodecyldimethylammonium chloride and dihexadecyl dimethylammonium chloride, amide derivatives of amino alcohols such as beta-hydroxyethyl stearyl, amine salts of long chain fatty acids, bases of quaternary ammonium derived from fatty amides of di-substituted diamines such as oleylbenzylamino ethylene diethylamine hydrochloride; quaternary ammonium bases of benzimidazolines such as the methylheptadecyl benzimidazole hydrobromide; basic pyridinium compounds and derivatives such as cetyl pyridinium chloride; sulfonium compounds such as octadecyl sulfonium methyl sulfate; betaine quaternary ammonium compounds such as diethylamino acetic acid betaine compounds and octadecylchloromethyl ether; urethanes and ethylenediamine such as the condensation products of stearic acid and diethylenetriamine; polyethylene diamine and polypropanol polyethanol amines. Commercial cationic surfactants include products sold as ARQUAD® T-27W, 16-29, C-33, T-50; and ETHOQUAD® T / 13 and T / 13 ACQUIT; by Akzo Chemicals Inc., Chicago Illinois. The anionic or cationic surfactant is present from 0.05 to 30% by weight of the total emulsion, preferably from 0.5 to 20%.

Useful nonionic surfactants have a hydrophilic-lipophilic balance (HLB) of 10 to 20. Nonionic surfactants with a HLB of less than 10 may be used, but imprecise solutions may result due to the limited solubility of the nonionic surfactant in water. When using a nonionic surfactant with an HLB less than 10, a nonionic surfactant with an HLB greater than 10 must be added during or after the polymerization. Commercial nonionic surfactants are exemplified by 2,6,8-trimethyl-4-nonyloxy polyethylene-oxyethanol (6EO) and (10EO) sold as TERGITOL® TMN-6 and TERGITOL®-10; alkylenoxy polyethylene oxetatanol (secondary alcohol ethoxylates of 11 to 15 carbon atoms 7E0, 9EO and 15EO) sold as TERGITOL® 15-S-7, TERGITOL® 15-S-9 and TERGITOL® 15-S-15; other secondary alcohol ethoxylates of 11 to 15 carbon atoms 7E0, 9EO and 15EO) sold as TERGITOL® 15-S-12, 15-S-30 and 15-S-40; and octylphenoxy polyethoxyethanol (40EO) sold as TRITON® X-405. All of these surfactants are sold by Union Carbide Corporation, Danbury Connecticut. Other commercial nonionic surfactants are nonylphenoxy polyethoxyethanol (10EO) sold as MAKON ® 10 by Stepan Company, Nothfield Illinois. An especially useful surfactant is polyethylene 23 lauryl ether (Laureth-23) sold commercially as BRIJ ® 25 by ICI Surfactants, Wilmington Delaware. The level of nonionic surfactant is from 0.1 to 40% by weight based on the total weight of the emulsion preferably from 0.5 to 30%.

Some commercially available ionic surfactants have characteristics of both ionic and nonionic surfactants combined, such as methyl polyoxyethylene (15) octadecylammonium chloride sold as ETHOQUAD ® 18/25 by Akzo Chemicals Inc., Chicago, Illinois. It is a cationic quaternary ammonium salt with polyethylene oxide tails. When this type of ionic surfactant is used in the present invention, it is not necessary to have both ionic and nonionic surfactants in the reaction medium. Only the ionic surfactant having non-ionic characteristics is needed. If the ionic surfactant does not have characteristics of both ionic and nonionic surfactants, it is necessary to use both types of surfactants in the method of the present invention. Surfactants such as ETHOQUAD ® 18/25 are generally used in the emulsion at levels equal to the level of the ionic surfactant used.

The present method is preferably carried out by creating a mixture comprising a cyclic siloxane, a water-soluble hydrolyzable alkoxysilane, an ionic (cationic or anionic) surfactant, a non-ionic catalyst surfactant and water. The mixture is then heated with stirring to a polymerization reaction temperature until essentially all of the cyclic siloxane and the water-soluble hydrolyzable alkoxysilane silane, an ionic (cationic or anionic) surfactant, a nonionic catalyst surfactant and water. The mixture is then heated with stirring to a polymerization reaction temperature until essentially all of the cyclic siloxane and the silane have reacted and a stable oil free emulsion of a gel-free polymer is formed. The time required for the formation of the stable oil-free emulsion of a gel-free polymer will vary depending on the reactants and the reaction conditions.

The mixture of cyclic siloxane, silane, ionic surfactant, nonionic surfactant, water and catalyst is not stable and will separate without some agitation means. It is not necessary to have all the cyclic siloxane and the silane fully dispersed within the mixture during the reaction; however, some means of agitation must be provided throughout the course of the reaction.

Combining the cyclic siloxane, the silane, the ionic surfactant, the nonionic surfactant, the catalyst and water and subsequently reacting the cyclic siloxane and the silane to form the emulsion can take place in different ways. The first thing is to combine all the ingredients with agitation, in some given order, and heat until reaching the polymerization temperature and then heat and stir at the desired polymerization temperature, thereby allowing the cyclic siloxane and the silane to react and form an emulsion . A third way is to combine all the ingredients with agitation, except the cyclic siloxane and the silane, heat until the desired polymerization temperature is reached, add or feed the cyclic siloxane and the silane and then heat and stir at the desired polymerization temperature, thereby allowing the cyclic siloxane and the silane to react and form an emulsion. It is not essential that the ingredients be combined in any given order. However, it is essential to have agitation during and after the addition of the ingredients and to have reached, or to warm to, the polymerization temperature when all the ingredients have been combined.

The preferred method for forming emulsions is to create a mixture by combining the cyclic siloxane, mixture of cyclic siloxanes, silane, at least one nonionic surfactant, at least one ionic (cationic or anionic) surfactant and water; providing agitation such that the cyclic siloxane and the silane are completely dispersed in the mixture; heating to the polymerization temperature; and then add the catalyst. Next, the mixture is maintained at the polymerization temperature with stirring until a stable, oil-free polymer gel-free emulsion is formed.

The present method can also be carried out by combining and mechanically emulsifying at least the cyclic siloxane and the silane reagents, the nonionic surfactant and part of the water. Subsequently, additional water, the ionic surfactant and the catalyst are added to the pre-emulsion with stirring. The mixture is then heated to the polymerization reaction temperature and optionally maintained with stirring until the monomers are consumed in the formation of the emulsion. Due to the formation and stability of the pre-emulsion, it is not necessary to have agitation during the course of the polymerization reaction.

The temperatures of the polymerization reaction are generally higher than the freezing point but lower than the boiling point of the water. Pressures above or below atmospheric pressure allow the reaction to leave this range. At temperatures below room temperature, the polymerization reaction can proceed more slowly. The preferred temperature range is 50 to 95 ° C.

The polymerization reaction is stopped at the desired level of cyclic siloxane / silane conversion and / or particle size using known methods. It is preferred to stop the reaction when the larger amount of the cyclic siloxane and silane have reacted or when the ring / chain equilibrium for the system and the desired particle size have been obtained. Reaction times less than 24 hours, typically less than 5 hours, are sufficient to achieve our desired particle size and / or conversion level. Methods for stopping the reaction comprise neutralizing the catalyst by adding equal, slightly higher stoichiometric amounts of acid or base depending on the type of catalyst. It can be used either a strong or weak acid / base to neutralize the reaction. Care should be taken when a strong acid / base is used so as not to neutralize, as is possible to re-catalyze the reaction. It is preferred to neutralize with sufficient amounts of acid or base such that the resulting emulsion has a pH of less than 7 when a cationic surfactant is present and pH greater than 7 when an anionic surfactant is present.

The equilibrium molecular weight of the emulsion polymers is inversely proportional to the temperature. Therefore, if a higher degree of polymerization (DP) is desired, a reduction in temperature in accordance with the particle formation will result in a polymer of higher molecular weight.

A useful temperature range for this procedure is 10 to 50 ° C.

A small amount of alcohol can be added to the reaction medium before or after the catalysis to increase the particle size of the emulsion. Alcohols useful in the method include methanol, ethanol and isopropanol. Because alcohols are generally used to break emulsions, it is preferred to keep the alcohol concentration at low levels, preferably below 5% by weight. In order to have the largest effect on the particle size, it is preferred to keep the alcohol present through the course of the polymerization reaction.

To illustrate the present invention as an improvement over EP-A 0 459 500, the following example is established for comparison purposes.

Comparative Example 1 This example shows the use of cyclic siloxanes and an organosilane such that copolymerization exists between the cyclic siloxanes and the silane. This example is, in principle, comparable to Example 11 of EP-A 0 459 500, in which the cyclic siloxanes and a trialkoxysilane are copolymerized in the presence of an ionic surfactant, a nonionic surfactant and water. In example 11 of EP-A 0 459 500, the cyclic siloxanes and a silane with cationic functionality N- (2-aminoethyl) -3-aminopropyltrimethoxysilane are copolymerized in the presence of a cationic surfactant (ARQUAD ® T-27W) a surfactant non-ionic (MAKON ® 10) and water. In this comparative example the cyclic siloxanes and a silane with a non-functional neutral organic group, ie methyltrimethoxysilane, are copolymerized in the presence of an anionic surfactant (dodecylbenzenesulfonic acid), a nonionic surfactant (BRIJ ® 35 L) and water. This comparative example does not describe how to avoid gel formation of the resulting siloxane polymer, nor is it considered in EP-A 0 459 500. 644. 0 g of water, 131.6 g of dodecylbenzenesulfonic acid (DBSA) and 10.5 g of BRIJ ® 35L were added to a reaction flask and the contents heated to 80 ° C. 350.0 g of cyclic siloxane, which have an average of 4 silicone atoms per molecule, were added with stirring to the mixture in the reaction flask at a rate of 1.94 g per minute. Subsequently, 30 minutes after the start of feeding the cyclic siloxane, 7.0 g of methyltrimethoxysilane MeSi (OMe) 3 was added to the mixture in the reaction flask at a rate of 0.467 g per minute. The reaction was maintained at 80 ° C for an additional three hours after completion of feeding the cyclic siloxane to reach equilibrium. 79.9 grams of an 85% aqueous solution of triethanolamine were added to neutralize the catalyst, which, in this case, was the DBSA that worked as a catalyst and as an anionic surfactant. The resulting product was an oil-free microemulsion with a particle size of 36 nanometers (nm) as measured by a particle size meter Nicomp ® model 370 Submicron. The monomer conversion was about 96.0% by weight. The polymer was extracted from the emulsion by adding 10 grams of emulsion, 1.5 g of anhydrous CaCl2, 20 ml of methanol and 25 ml of pentane in an appropriate container. The mixture was stirred vigorously, added to a plastic centrifuge tube and centrifuged at 3000 r.p.m. (314 rad / s) for 15 minutes. The top layer was removed from the tube and removed to obtain only the siloxane polymer, the cut viscosity of the extracted polymer was approximately 53,000 (ml2 / s) at a cutting speed of 20..0 1 / sec (reciprocal seconds) ) using a Brookfield ® Model HBDV-III viscometer. The molecular weight distribution of the polymer as measured by Gel Permeation Chromatography (GPC) was comprised of a broad peak of low molecular weight corresponding to the sun(finite polymeric species) and by a narrow peak of high molecular weight corresponding to the gel.

The present invention, in contrast, is represented by the following examples EXAMPLES OF THE INVENTION EXAMPLE 1 PROCEDURE A The following procedure illustrates the method used to collect the subsequently established data separately for each of the individual examples 1 to 6 and 8. This procedure, even though it is specific for example 1, was used in examples 2 to 6 , 8 and comparative example II. Subsequently, in Example 7, a separate procedure is described. Thus, 644.0 grams of water, 131.4 grams of dodecylbenzenesulfonic acid and 10.5 grams of BRIJ® 35L were added to a reaction flask and the contents were heated to 80 ° C. Once the temperature reached 80 ° C, 343.14 g of cyclic siloxanes, having an average of four silicone atoms per molecule, were added with agitation to the mixture in the reaction flask at a rate of 1906 grams per minute. . Approximately 30 minutes after the start of the cyclic siloxane feed, 7.0 grams of a mixture of methyltrimethoxysilane MeSi (OMe) 3 in cyclic siloxane (2.0% silane by weight) was added to the mixture, in the reaction flask, in a proportion of 0.467 grams per minute. The reaction was maintained at 80 ° C for an additional three hours after completion of feeding the cyclic siloxane to reach equilibrium. Subsequently, the temperature of the reaction flask was reduced to 10 ° C to increase the molecular weight of the polymer. The contents of the flask were maintained at 10 ° C for about 4 hours until the equilibrium concentration of the silanol was reached. Then, 79.9 g of an 85% aqueous solution of triethanolamine were added to neutralize the catalyst. The resulting product was an oil-free microemulsion with a particle size of 37 nanometers (nm) as determined by a particle size meter Nicomp® Model 370 Submicron. The monomer conversion was about 93.5% by weight. The polymer was extracted from the emulsion by adding 10 grams of emulsion, 1.5 grams of anhydrous CaCl2, 20 ml of methanol and 25 ml of pentane in an appropriate container. The mixture was stirred vigorously, added to a plastic centrifuge tube and centrifuged at 3000 r.p.m. (314 rad / s) for 15 minutes. The upper layer was removed from the tube and was removed to obtain only the siloxane polymer, the cut viscosity of the extracted polymer was approximately 250,000 (mm2 / s) at a cutting speed of 6.0 s "1 (reciprocal seconds 1 / s) , using a Brookfield® Model HBDV-III Viscometer The concentration of the silanol in the polymer was approximately 454 ppm as determined by an Fourier Transform Infrared Spectroscopy (FTIR) technique. The FTIR Deuteration method was carried out by subtracting the FTIR spectrum from a deuterated diluted solution of polydimethylsiloxane in carbon tetrachloride CC14 from a spectrum of the same solution without deuteration After correcting the spectrum for the presence of water, The absorbance was correlated to 3693 cm-1 for the concentration of SiOH.The concentration of MeSi? 3/2 in the polymer was approximately 2. 56 ppm determined by equilibrium of the polymer sample with a large excess of hexamethyl disiloxane in the presence of a trifluoromethanesulfonic acid catalyst to produce the corresponding triorganosiloxy derivatives. The resulting solution was analyzed by internal standard gas chromatography to determine the concentration of the silicone substituents in smaller proportion. The molecular weight distribution of the polymer determined by GPC was comprised of a single broad peak and therefore this polymer contained only sol, denoting a finite polymeric species, ie free of gel.

EXAMPLE 1 PROCEDURE B To experimentally determine the gel point, the reaction temperature is lowered if it is known that the polymer contains only sol (finite polymer species) or is increased if it is known that the polymer contains sol and gel. This is then maintained until a static concentration of silanol is reached. The polymer is extracted from the sample of the emulsion and a chromatogram of the molecular weight distribution is obtained. The reaction temperature is adjusted systematically until the molecular weight distribution is only slightly bimodal (containing a soluble fraction of polymer and a gel fraction) and this transition is defined as the gel point. This procedure was used to identify the gel spot in Examples 2 to 7 and Comparison Example II.

EXAMPLE 1 Functionality Silane f = 3 (eg methylsilylosquioxane CH3SIO3 / 2) % by weight of Water 56.68 * % by weight of dodecylbenzenesulfonic acid (anionic) 11.58 * % by weight of Polyoxyethylene Lauryl Ether (23) (non-ionic) 0.92 * % by weight of Octamethylcyclotetrasiloxane 30.80 * ppm of Methyltrimethoxysilane 123 * Reaction temperature (° C) to form particles 80 Reaction temperature (° C) to increase the molecular weight of the polymer 9-10 Reaction temperature (° C) in neutralization 9-10 Temp. of reaction (° C) in the formation of the polymer gel, for reference < 9 Particle size weight instrument of Gaussian intensity (nm) 36.5 Characterization of the polymer Tables 1 & 2 * = amounts added to the reaction flask In example 1, the value 1.1 of f was determined by f = (f) (RnSiO (-? ny (MWSiOH) = (3 ¥ 256 (45) = 34560 = 1.1 (SiOHJ (MWRnSiO (4-ny2) (454X67) 30418 where f is the silane 3 functionality for the concentration of MeSi (OMe) 3, [nSiO (4-n) / 2] is the concentration of CH3Si03 / 2 determined in the resulting polymer as 256 ppm, [SiOH] is the concentration of the silanol determined in the resulting polymer as 454 ppm , MWSiOH is the number average molecular weight of silanol SiOH (28 + 16 + 1), MWRnSiO (4-n) / 2 is the number average molecular weight of a branched site like CH3Si03 / 2 (12 + 3 + 28 + (3x16) / 2), n is 1 and R is CH3 - This same type of computation was used in determining the value of f in Examples 2 to 8, but they are not shown in detail.

EXAMPLE 2 Functionality Silane f = 3 (eg methylsilylesquioxane CH3SÍO3 / 2)% by weight of Water 56.61 % by weight of dodecylbenzenesulfonic acid (anionic) 11.57% by weight of polyoxyethylene (23) lauryl ether (non-ionic) 0.92 % by weight of Octamethylcyclotetrasiloxane 30.77 ppm of Methyltrimethoxysilane 1230 Reaction temperature (° C) to form particles 81 Reaction temperature (° C) to increase the molecular weight of the polymer N / A Reaction temperature (° C) in neutralization 81 Temp. of reaction (° C) in the formation of the polymer gel for reference 23 Particle size (nm) 32.5 Polymer characterization Tables 1 & 2 EXAMPLE 3 Functionality Silane f = 3 (eg propyl silsesquioxane C3H7SIO3 / 2)% by weight of Water 56.61 % by weight of dodecylbenzenesulfonic acid (anionic) 11.57% by weight of polyoxyethylene (23) lauryl ether (non-ionic) 0.92 % by weight of Octamethylcyclotetrasiloxane 30.76 ppm of Methyltrimethoxysilane '1485 Reaction temperature (° C) to form particles 80 Reaction temperature (° C) to increase the molecular weight of the polymer N / A Reaction temperature (° C) in the neutralization 80 Temp. of reaction (° C) in the formation of the polymer gel, for reference 49 Particle size (nm) 33.4 Characterization of the polymer Tables 1 & 2 EXAMPLE 4 Functionality Silane f = 3 (eg octyl silsesquioxane CsHpSiOs ^)% by weight of Water 56.53 % by weight of dodecylbenzenesulfonic acid (anionic) 11.57 % by weight of Polyoxyethylene Lauryl Ether (23) (non-ionic) 0.94 % by weight of Octamethylcyclotetrasiloxane 30.72 ppm of Methyltrimethoxysilane 2500 Reaction temperature (° C) to form particles 80 Reaction temperature (° C) to increase the molecular weight of the polymer N / A Reaction temperature (° C) in neutralization 80 Temp. of reaction (° C) in the formation of the polymer gel, for reference 50-80 Particle size (nm) 40.6 Characterization of the polymer Tables 1 & 2 EXAMPLE 5 Functionality Silane f = 3 (eg dodecylsilyesquioxane C12H25SÍO3 / 2)% by weight of water 56.50% by weight of dodecylbenzenesulfonic acid (anionic) 1 1.55 % by weight of Polyoxyethylene Lauryl Ether (23) (non-ionic) 0.92% by weight of Octamethylcyclotetrasiloxane 30.73 ppm of Methyltrimethoxysilane 3010 Reaction temperature (° C) to form particles 80 Reaction temperature (° C) to increase the molecular weight of the polymer N / A Reaction temperature (° C) in the neutralization 80 Temp. of reaction (° C) in the formation of the polymer gel, for reference 50 Particle size (nm) 36.3 Polymer characterization Tables 1 & 2 EXAMPLE 6 Functionality Silane = = 4 (eg silicate SIO2)% by weight of Water 56.65 % by weight of dodecylbenzenesulfonic acid (anionic) 11.58 % by weight of Polyoxyethylene Lauryl Ether (23) (non-ionic) 0.93 % by weight of Octamethylcyclotetrasiloxane 30.78 ppm of Methyltrimethoxysilane 703 Reaction temperature (° C) to form particles 80 Reaction temperature (° C) to increase the molecular weight of the polymer 51 Reaction temperature (° C) in neutralization 51 Temp. of reaction (° C) in the formation of the polymer gel, for reference 23 Particle size (nm) 35 Characterization of the polymer Tables 1 & 2 EXAMPLE 7 - PROCEDURE In this example, the cationic surfactant is used and the procedure in this example differs from the procedure in Examples 1-6 and 8 where an anionic surfactant was employed. 630. 0 grams of water, 144.2 grams of cationic surfactant ETHOQUAD ® T / 13, 65.8 grams of nonionic surfactant TERGITOL ® 15-S-12 and 399.0 grams of cyclic siloxanes having an average of four silicon atoms per molecule, They were added to a reaction flask, and the contents were heated to 85 ° C. 4.9 grams of a 50% aqueous catalyst solution of NaOH were added to the mixture in the reaction flask. Next, 8 hours after the addition of the NaOH catalyst, 22.2 grams of a mixture of methyltrimethoxysilane MeSi (OMe) 3 in cyclic siloxanes (11.3% silane by weight) were added to the mixture, in the reaction flask, in a proportion of 0.37 grams per minute. The reaction was maintained at 85 ° C for an additional four hours after completion of feeding the cyclic siloxane to reach equilibrium. Subsequently, the temperature of the reaction flask was reduced to 23 ° C for about four hours. Subsequently, 3.8 grams of glacial acetic acid were added to neutralize the catalyst. The resulting product was an oil-free microemulsion with a particle size of 61 nanometers (nm) determined by a particle size meter Nicomp® Model 370 Submicron. The monomer conversion was not determined. The methods used to extract the polymer, measure the concentration of the silanol in the polymer, measure the concentration of the methylsquioxane in the polymer and to obtain the molecular weight distribution of the polymer were identical to the procedures described in Example 1.

EXAMPLE 7 Functionality Silane f = 3 (eg methylsilylosquioxane CH3SIO3 / 2)% by weight of Water 50.54% by weight Ethoquad® T / 13 (cationic) 11.57 % by weight of Tergitol® 15-S-12 (non-ionic) 5.28 % by weight of Octamethylcyclotetrasiloxane 32.01 % by weight of NaOH (50% aqueous solution) 0.39 ppm of Methyltrimethoxysilane 2000 Reaction temperature (° C) to form particles 85 Reaction temperature (° C) to increase the molecular weight of the polymer 23 Reaction temperature (° C) in neutralization 23 Temp. of reaction (° C) in the formation of the polymer gel for reference 6 Particle size 61 Characterization of the polymer Tables 1 & 2 EXAMPLE 8 Functionality Silane f = 3 (eg methylsilylsquioxane CH3SIO3 / 2)% by weight of Water 56.64% by weight of dodecylbenzenesulfonic acid (anionic) 11.57 % by weight of Polyoxyethylene Lauryl Ether (23) (non-ionic) 0.92% by weight of Octamethylcyclotetrasiloxane 30.80 ppm of Methyltrimethoxysilane 615 Reaction temperature (° C) to form particles 80 Reaction temperature (° C) to increase the molecular weight of the polymer 15 Reaction temperature (° C) in neutralization 15 Temp. of reaction (° C) in the formation of the polymer gel, for reference < fifteen Particle size (nm) 36 Characterization of the polymer Tables 1 and 2 Example 8 shows the preparation of a high viscosity polymer of 1 million mm2 / s without the presence of a gel fraction.

In each of examples 1 to 8 representing the methods of the present invention, the functionality ratio f had a value less than the functionality ratio at the gel point fg. This is shown in table 1.

EXAMPLE OUT OF REACH OF THE PRESENT INVENTION EXAMPLE II - COMPARISON Functionality Silane f = 3 (eg methylsilylosquioxane CH3SIO3 / 2) % by weight of Water 56.6 % by weight of dodecylbenzenesulfonic acid (anionic) 11.6 % by weight of Polyoxyethylene Lauryl Ether (23) (non-ionic) 0.92 % by weight of Octamethylcyclotetrasiloxane 30.8 ppm of Methyltrimethoxysilane 1230 Reaction temperature (° C) to form particles 81 Reaction temperature (° C) to increase the molecular weight of the polymer 10 - 11 Reaction temperature (° C) in neutralization 10 - 11 Temp. of reaction (° C) in the formation of the polymer gel, for reference 23 Particle size (nm) 34.9 Characterization of the polymer Tables 1 & 2 In the comparison example, the functionality ratio f (4.26) did not have a value lower than the functionality ratio at the gel point fg (4.13). Therefore, the microemulsion polymer in Comparative Example II contained a soluble polymer fraction and a gel fraction. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property: Table 1. Aspects of Average Molecular Weight Distribution in Number of Polymer ppm RnSiO (4 - "/ 2> ppm SiOH in ppm RnSi <-./2) in ppm SiOH in Peak of Gel Peak of Sun in the polymer polymer from the polymer to the polymer point Present (?) Present (?) of the example example f gel point (*) of the (*) fg 1 No Yes 256 454 1.1 not available not available > 1.1 2 No Yes 1077 1274 1.7 1124 548 4.1 3 No Yes 2820 (a) 1114 3.8 2820 (a) 825 4.9 4 No Yes 4940 (a) 1238 3.3 4940 (a) 792-1238 3.3-5.1 5 No Yes 6600 (a) 1302 3.1 6600 (a) 911 4.4 6 No Yes 677 (a) 838 2.4 677 (a) 554 3- 7 ^ * - 7 No Yes 2580 1056 4.9 2580 749 6.9 8 No Yes 980 587 4.0 not available not available > 4.0 II No Yes 1044 1044 4.3 1124 548 4.1 c = determined by Gel Permeability Chromatography * = estimated value considering 100% incorporation of the silane * = The gel point corresponds to the incipient heterogeneity of the molecular weight distribution of the polymer Table 2. Additional Characterization Data Example Viscosity Conversion of Polymer Equilibrium Viscidity Equilibrium at the Cyclic Point% by weight Gel Example (s) 1 93.4 250,000 at a speed cut = 6.0 1 / s not available 97. 4 4,500 (cutting speed not noted) 128,000 at one speed. of cut = 6.0 1 / s 98. 9 14,000 at a speed cutting = 80.0 1 / s 112,000 at a speed cut off 8.0 1 / s 97. 9 16,000 at a speed cutting = 80.0 1 / s not available 00 97.8 6,300 at a speed. cutting = 200 1 / s 68,000 at a speed cutting = 16 1 / s 97. 3 not available not available not determined 5,500 at a speed Cutting = 200 J / s not available 92. 6 1,300,000 at a speed cut = 0.4 1 / s not available CEU 100 2, 100,000 at a speed cutting = 0.4 1 / s 128,000 at a speed cut = 6.0 1 / s es = centistokes = mm2 / sec 1 / s = s-1 = reciprocal seconds CEU = Comparison Example II

Claims (7)

1. A method for preparing microemulsions of gel-free organopolysiloxanes, characterized in that it comprises (i) copolymerizing a cyclic siloxane and an unsubstituted alkyltrialkoxysilane, an aryltrialkoxysilane or a tetraalkoxysilane, in an aqueous medium containing a nonionic surfactant, an anionic or cationic surfactant and a catalyst, until obtaining the desired increase in molecular weight, and (ii) controlling the gel content of the organopolysiloxane in the microemulsion by: to. the control of the silane concentration and the concentration of silanol in the resulting organopolysiloxane, as a function of a predetermined functionality ratio f b. The relationship of functionality being a relationship defined according to the following formula: (f) [RnSiO (4_n) / 2] (MWSiOH) [SiOH] (MWRnSiO (4_n) / 2) where f is the silane functionality, / RnSiO (4-n) /? and ¿ßiOKj are the concentrations of RnSiO (-n) / 2 and SiOH respectively in the resulting organopolysiloxane, MWSiOH is the number average molecular weight of silanol, MWRnSiO (4_n) / 2 is the number-average molecular weight of the branched site, n is 0 or 1, and R is an organic group.

2. A method according to claim 1, characterized in that the functionality ratio f is maintained at a lower value than the functionality ratio at the gel point fg, having the functionality ratio in The gel point is a value which is determined experimentally by gel permeation chromatography and forming a polymer with a molecular weight distribution of gel-free organopolysiloxane in the microemulsion.

3. A method according to claim 1, characterized in that the silane is selected from the group consisting of methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, n-butyltrimethoxy-silane, hexyltrimethoxysilane, octyltrimethoxysilane, octyltri-ethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, phenyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxylane and tetrabutoxy silane.

4. A method according to claim 1, characterized in that the cyclic siloxane has the formula: wherein R is a saturated or unsaturated alkyl group of 1 to 6 carbon atoms or an aryl group of 6 to 10 carbon atoms, R optionally contains a functional group which is not reactive at the ring opening and in the polymerization reactions and x is from 3 to 7.

5. A microemulsion characterized in that it is obtainable by the method defined in claim 1.

6. A microemulsion according to claim 5, characterized in that it contains a finite organopolysiloxane gel-free in the microemulsion, the organopolysiloxane having a viscosity of 1,000 to 5,000,000 mm 2 / s.

7. A microemulsion according to claim 6, characterized in that the organopolysiloxane has a particle size in the microemulsion of 25 to 70 nanometers.