MXPA99010371A - Release agent - Google Patents

Abstract

The present discloses a mold release agent comprising an aqueous emulsion containing a condensation- or addition-crosslinking silicone system (A or B respectively) with at least 2 components and (C) aqueous colloidal silicic acid (silica sol). An Independent claim is also included for a process for vulcanizing pneumatic tires in which a mold release agent as described above is applied to the bladder and/or the tire blank before vulcanization.

Description

-.- a j REMOVING AGENTS FIELD OF THE INVENTION The invention relates to a releasing agent free of fillers comprising an aqueous emulsion of silicone systems and of silica crosslinking with each other, which also provide the treated surfaces with good lubricating properties. The release agent is especially suitable as a separating agent in the manufacture of tires and other rubber articles and is used therein for molding and vulcanizing these articles.

BACKGROUND OF THE INVENTION According to the state of the art, the tires are molded and vulcanized by introducing the preform of the tire into a mold and pressed against this mold with a heating membrane (bladder, bubble) vulcanizing to the action of the heat. The heating membrane must slide in the preform and be able to be separated from the tire after vulcanization. For the R? F-: 32025 both the preforms of the tires are arranged in a spray booth, in which they are put into rotation with the aid of a mechanical device. A spray gun is applied to this preform in rotation, with which a solution of the separation agent is distributed in the preform. The floating mist is removed most often by means of a stop of water and collected in the water. The molding and vulcanization of the preform is then carried out in a vulcanization press by means of a heating membrane b, whose task is to heat the preform of the tire and compress the tire with high pressure in the negative form. The aqueous emulsions of organopolysiloxanes and their use as separation agents in the molding and vulcanization of tires are known from the prior art. US-A-4 184 880 discloses emulsions of release agents which, however, contain large amounts of inorganic silicates as fillers, which-to hydrophobize their surface-have been treated with organosiloxane compounds. US-A-4 431 452 discloses an aqueous composition of the separating agent consisting of: 1) a polydimethylsiloxane closed at the ends by SiOH with a viscosity of up to 25,000,000 Centistokes at 25 ° C; 2) a polydimethylsiloxane closed in the end groups by SiOH with a viscosity of up to 120,000 Centistokes at 25 ° C; 3) a polyalkylene glycol; 4) a bentonite; and 5) a surfactant.

US-A-4 359 340 discloses aqueous compositions of separation agents for use in the molding of tires. The emulsions consist of: 1) a polydimethylsiloxane with a viscosity of up to 25,000,000 Centistokes at 25 ° C; 2) a methylhydrogensilane with a viscosity of 20 to 40 Centistokes or a dimethylhydrosilane with a viscosity of 80 to 120 Centistokes; 3) a metal salt of an organic acid; and 4) a surfactant. EP-A-0 279 372 discloses aqueous emulsions of organopolysiloxane, which can be used as separating agents in the molding and vulcanization of tires and especially for the bladder lining and which are constituted by: 1) a polydimethylsiloxane polymer closed in the end groups with SiOH with a plasticity of 50 to 100; 2) an organohydrogenpolysiloxane with, on average, at least 2 hydrogen atoms per molecule bonded with Si; 3) a lubricating agent with a melting point of 25 to 80 ° C; 4) an inorganic silicate (mica); 5) a thickening agent; 6) a surfactant; 7) water. The drawback of the compositions of the aqueous separation agents described up to the present consists, on the one hand, in that they contain relatively large quantities of inorganic silicates as fillers, which have a negative effect on the stability of the emulsions, on the other hand in which they are crosslinked by means of a reaction of a SiOH group with SiH with hydrogen dissociation, which is undesirable due to the danger of expulsion.

EP-A-0 635 559 discloses a composition of separation agents for the molding of tires, which acts without the undesirable release of hydrogen. The described emulsion is used for the bladder lining and consists of 1) at least one reactive polydimethylsiloxane with a kinematic viscosity comprised between 50 and 30,000,000 mm s-1 at 25 ° C; 2) at least one reactive polydimethylsiloxane with a kinematic viscosity comprised between 15 and 5,000,000 mm s-1; 3) a crosslinker; 4) a surfactant; and 5) water. EP-A 0 111 100 describes a separation agent for the manufacture of silicone-based tires, which is not only dissolved in an organic solvent and must be used in this state, but also has to contain kaolin, chalk, mineral flour , silicic acid, soot or graphite, in the event that the heating membrane does not already have a roughness in advance such as to ensure sufficient air escape. A sufficient lubrication and separation effect can be achieved simply with lubricants, for example Si oils or Si oil emulsions but nevertheless total ventilation can be achieved by eliminating the air between the heating bellows and the shape of the tire. The occluded air means tires rejected since no sufficient vulcanization takes place under the air bubbles. Loads (mineral or otherwise) are required as disconnectors between the bladder and the tire reform so that the air can escape before vulcanization. Fundamentally due to the ventilation, it was not possible to use internal solutions, free of charges, which were constituted only by combinations of the separating agent or the lubricant. In this case, the loads fulfill the function of a separator between the inner lining of the tire preform and the heating bellows. When using traditional silicone oils up to now annoying separations were produced in the tire pushers. Thus, there was a need for an aqueous separation agent, free of solvents, which could be sprayed on the inner side of the tire preform and / or on the surface of the heating bellows and which fulfilled all the requirements for vulcanization, namely the lubrication, separation and ventilation and, at the same time, do not present the drawbacks described above - such as content in charges and / or cross-linking by hydrogen cleavage. In addition, separations in the tire pushers should be avoided.

DESCRIPTION OF THE INVENTION The invention relates to release agents comprising, in an aqueous emulsion - a system consisting of at least two silicone components that react with each other under crosslinking, this system being selected from the group consisting of (A) at least silicone components that react under condensation or (B) at least silicone components that react under addition, and an aqueous-colloidal silicic acid (silica sol). The invention therefore also relates to a method for vulcanizing tires, characterized in that, as a step prior to vulcanization, the composition of the release agent according to the invention is applied on the heating bellows and / or on the surface of the tire. The process according to the invention is also environmentally friendly since it acts with approximately 10% of the solid active substance in active substance compared to the traditional state of the art and, therefore, is more economical as a whole. The silicone systems (A) or (B), which react under crosslinking according to the invention, are constituted by mixtures of emulsions of silicone components (A) which react with each other under condensation (crosslinking agents) or are constituted by mixtures of emulsions of silicone components (B) which react with each other under addition (crosslinking agents), which will be described in more detail below. Both reaction systems are catalyzed by means of suitable catalysts.

A. Silicone systems crosslinking each other under condensation.

These systems are constituted by mixtures of aqueous emulsions of polydimethylsiloxanes (A-1) closed in the end groups with Si-OH and alkoxy-functional silicones (A-2). The emulsion of the polydimethylsiloxane (Al) closed in the end groups with Si-OH contains the siloxane in an amount of from 20 to 80% by weight, preferably from 30 to 60% by weight, based on emulsion A-1. The emulsion of the silicone (A-2) alkoxy-functional, capable of cross-linking, contains the siloxane in an amount of 20 to 80% by weight, preferably 25 to 60% by weight, based on the emulsion A- 2. The two emulsions are mixed together in a quantitative ratio A-1: -2 from 20:80 to 80:20, preferably from 40:60 to 60:40. Obviously both emulsions contain the suitable emulsifiers, conditioned by their obtaining. Emulsion A, prepared from emulsion A-1 and emulsion A-2, contains from 20 to 80% by weight, preferably from 30 to 60%. in weight. silicone, referred to emulsion A.

A-l: Emulsions of polydimethylsiloxanes closed at the ends with Si-OH: The end-capped polydimethylsiloxanes with Si-OH are constituted by polymers of the general formula I HO [Yes (CHJ: -OLH (I) with p = 4000 to 3,000, preferably 800 to 2,000. Obtaining the emulsions of an oil of Silicone closed at the ends with OH-, long chain, by emulsion polymerization, is known to the person skilled in the art for example by US-A-2 891 920, or by GB-A-1 0204 024. It is It is particularly preferred to use an alkylbenzene sulphonic acid as a catalyst in the process disclosed in GB-A-1 024 024, since in this case the emulsifier and the polymerization catalyst are a simple one. Once the polymerization is carried out, the acid is neutralized so that finally the properties of the catalyst are blocked, while the properties of the emulsifier are fully maintained or even improved. Therefore, the concentration of the emulsifier can be kept low and, after finishing the emulsion, there are no interfering foreign molecules, coming from the catalyst, in the finished product. Instead of the alkylbenzenesulfonic acids mentioned, however, n-alkylsulfonic acids can also be used. It is also possible to use additional emulsifiers in addition to the sulfonic acids having a catalytic action in the form of co-emulsifiers. Such co-emulsifiers can be non-ionic as well as anionic in nature. Suitable anionic co-emulsifiers are salts of the aforementioned n-alkyl-alkylbenzenesulphonic acids. The non-ionic coemulsifiers are polyoxyethylene derivatives of fatty alcohols, fatty acids and the like. Examples of such emulsifiers are POE (3) -lauryl alcohol, POE (20) oleyl alcohol, POE (7) -nonylphenol or POE (10) -stearate (the POE (3) -lauryl alcohol form means that they have been added on a molecule of lauryl alcohol 3 units of ethylene oxide, the number 3 representing a mean value). Such nonionic emulsifiers are known in principle by the person skilled in the art. The added co-emulsifiers increase, on the one hand, the stability of the resulting emulsion after the emulsion polymerization, on the other hand they nevertheless exert an effect on the chain lengths of the closed silicone oil at the end groups with OH -, long chain, which are formed during the polymerization. In general, such silicone oils, which are formed by emulsion polymerization in the presence of non-ionic co-emulsifiers, have a lower molecular weight than those in which coemulsifier has not been used. In addition, a molecular weight control of the silicone oil is carried out, closed in the end groups with OH-, formed by the polymerization) by emulsion, through the temperature in the formation of the balance between siloxane water and the silanol that is first formed by opening the siloxane ring. In obtaining an emulsion of a silicone oil closed in the end groups with long chain OH-, the procedure described below is particularly preferred. As a monomer, it employs octamethylcyclotetrasiloxane (D 4) in an amount such that a 40 ° emulsion results. The sulfonic acid, of catalytic action in the emulsion polymerization is an n-alkylsulfonic acid. A 4%, based on the amount of D4, of this sulphonic acid will be used. As coemulsifiers, the Na salts of the sulphonic acids used as catalyst and the POE (5) -lauryl alcohol are used. The temperature of the emulsion polymerization is 60 ° C, neutralizing with triethanolamine. A particularly preferred emulsion of a polydimethylsiloxane, closed in the end groups, is constituted by a 40'J by weight emulsion of a polydimethylsiloxane of the formula I, in which p is between 800 and 2,000.

A-2: Emulsions of alkoxy-functionalized silicone oils: The Sixone, alkoxy-functionalized, oil contained in the emulsion A-2 according to the invention and which is capable of crosslinking, is constituted by units of the general structure RrR, p, SiO (4 ^ -m) r (H) wherein R means hydrocarbon radicals or oxyhydrocarbon radicals equal or different, optionally substituted, with 1 to 18 carbon atoms, R 'mean substituted hydrocarbon radicals, containing polar groups, linked with Si-C, equal or different, n means an integer with the value of 0, 1, 2 or 3, m means an integer with the value of 0, 1, 2, or 3, and the sum n + m has a mean value of 1.8. at 2.2 and m is chosen in such a way that the polyorganosiloxane has at least one radical R '. Preferably, the sum n + m has a mean value of 1.9 to 2.1. Examples of hydrocarbon radicals R are alkyl radicals, such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, isobutyl, tere. -butyl, npentyl, so-pentyl, neo-pentyl, tere, -pentyl; hexyl residues such as the n-hexyl moiety; heptyl residues, such as the n-heptyl moiety; octyl radicals, such as the n-octyl moiety and the iso-octyl moiety, such as the 2,2-trimethylpentyl moiety; nonyl residues, such as the n-nonyl moiety; decile residues, such as the n-decyl moiety; dodecyl moieties, such as the n-dodecyl moiety; octadecyl moieties such as the n-octadecyl moiety; alkenyl residues, such as vinyl, allyl and 5-hexen-1-yl residues; cycloalkyl radicals, such as cyclopentyl, cyclohexyl, cycloheptyl and methyl-cyclohexyl radicals, aryl radicals such as phenyl, naphthyl and anthryl radicals and phenanthryl radicals; aralkyl radicals, such as o-, m-, p-tolyl radicals, xylyl radicals and ethyl phenyl radicals; aralkyl radicals, such as the benzyl residue, the a- radical and the p-phenylethyl radical. Examples of optionally substituted oxyhydrocarbon radicals R are substituted and unsubstituted hydrocarbon radicals R, linked through an oxygen atom bonded directly to the silicon atom, according to the aforementioned examples, especially alkoxy radicals with 1 to 18 carbon atoms. and phenoxy moieties, especially the methoxy, ethoxy, n-propoxy, iso-propoxy and phenoxy moiety. Preferably, at most 10 T of the radicals R are optionally substituted oxyhydrocarbon radicals. R radicals methyl, ethyl, phenyl, methoxy and / or vinyl are preferred. Due to its easy accessibility, 50 J of the radicals R preferably, and particularly preferably 80% of the radicals R, are methyl radicals. R 'can be selected from the group of radicals R. Preferably R' is chosen from the group of amino-functional hydrocarbon radicals, for example aminoalkyl radicals, such as the Y-aminopropyl radical and the b-aminoethyl-Y-aminopropyl radical; aminoaryl residues; amino functional, cyclic residues, linked with Si-C. Examples of preferred amino functional residues R 'are radicals of the general formula -R '- [R: (CH,) bNHR: (lili where R 1 is a hydrocarbon residue equivalent to 1 to 18 carbon atoms, R ~ represents a hydrogen atom or a hydrocarbon radical with 1 to 18 carbon atoms, optionally substituted, a has the values 2, 3, 4 , 5 or 6 and b have the values 0, 1, 2, 3 or 4. Examples of divalent hydrocarbon radicals with 1 to 18 carbon atoms R 1 are saturated, straight-chain or branched-chain or cyclic alkylene radicals such as methylene radicals and ethylene as well as the propylene, butylene, pentylene, hexylene, 2-methylpropylene, cyclohexylene and octadecylene or unsaturated alkylene or alkylene moieties such as the hexenylene moiety and the phenylene moiety, the n-propylene moiety and the moiety 2 being particularly preferred. methyl propylene. Examples of hydrocarbon radicals with 1 to 18 carbon atoms, optionally substituted R 2, are the examples given for R. In the general formula (III), indicated above, R 1 preferably denotes a divalent hydrocarbon radical having 2 to 6 carbon atoms. carbon, R ^ a hydrogen atom, a methyl or cyclohexyl radical, at the values 2 or 3 and b the values 0 or 1. As alkoxy functional silicones, capable of crosslinking, especially preferred, which also contain amino groups, are partially branched polydimethylsiloxanes with the structure with R "= H2N (CHJ, NH (CHJ3- or H, N (CH,) as well as Me = CH .. x = 20 to 200. For the preparation of such compounds as well as of the suitable emulsifiers, reference is made to EP-A-0 646 618. The emulsion containing the alkoxy-functional silicone, capable of crosslinking, can have plus a 2 to a 20,. by weight, preferably from 5 to 15 by weight of an alkoxy functional silicone resin of the formula V R'dSKOR-je '-' Md-rtl (V) where R * means a monovalent hydrocarbon radical with 1 to 14 carbon atoms carbon, preferably means the methyl moiety, R'1 means a monovalent hydrocarbon radical with 1 to 18 carbon atoms, preferably means the methyl moiety, and d means a value of 0.75 to 1.5, preferably means a value of about 1. , e e means a value of 0.2 to 2, preferably of 0.4 to 1.2. The viscosity of this resin is from 2 to 2,000, preferably from 20 to 200 mPa-s. The preparation of this alkoxy functional silicone resin is known and is carried out by reaction of the corresponding alkyl- and / or arylchlorosilanes with alcohol and water (see GB-A-685 173, DE-A-958 702, FR- 475 709, US-A-3 668 180, DE-A-2 061 189, DE-A-2 444 529, DE-A-2 532 887, EP-A-0 003 610, DE-A-3 000 782) The especially preferred methyl methoxy silicone resin is prepared by reaction of methyltrichlorosilane with methanol and water. If appropriate, mixtures of methyltrichlorosilane and other alkyl- and / or arylchlorosilanes and / or tetrachlorosilane can also be used for the preparation of the alkoxy-functional silicone resins, without undergoing the stability of the emulsion according to the invention. In the same way, mixtures of various alcohols can be used to obtain the resin and / or various functional alkoxy silicone resins can be mixed together without adversely affecting the stability of the emulsion. It is known to obtain the emulsions from the alkoxy functional silicone resins described by DE-A-3 323 909. As catalytically active substances (catalyst emulsion) for the crosslinking reaction between the closed polydimethylsiloxanes in the groups With Si-OH and the amino functional silicone emulsions are suitable those described in the cited literature for the condensation and esterification reactions. The catalysts are used in the usual concentrations described in this literature.

B. Silicone systems crosslinking with each other, under addition.

These systems are constituted by an emulsion B, which comprises a mixture of an emulsion, containing a polysiloxane organ B-1, having at least two unsaturated hydrocarbon groups and an emulsion containing a methylhydrogenpolysiloxane B-2 together with a catalyst. Emulsion B, prepared from emulsions Bl and B2, contains from 20 to 80 by weight, preferably from 30 to 60% by weight of silicone, based on emulsion B. The polysiloxane organ Bl, which has at least two unsaturated hydrocarbon groups, in the sense of the invention is preferably a linear or branched cyclic polysiloxane having units of the general formula (R'WR-JHSÍO, ^ (VI). with R '= alkenyl having 2 to 8 carbon atoms and / or ether radicals with 3 to 10 unsaturated carbon atoms, such as, for example, allyl, 1-butenyl, 1-hexenyl and / or -CH-CH.CH.0CH .CH = CH. etc., R6 = monovalent, saturated, optionally substituted, hydrocarbon radical with up to 10 carbon atoms from the group of substituted and unsubstituted alkyl, aryl and arylalkyl radicals, where a and b mean integers within the following limits: <0. f < 3 well 0 < h < 3 or 0 < f + h < 4 and they can be identical or different within the molecule Rf 'or R "respectively individually, preferably R5 vinyl or allyl, particularly preferably vinyl, Examples of R1" are methyl, ethyl, propyl, isopropyl, butyl, octyl, etc., cyclobutyl, cyclopentyl, cyclohexyl, etc., phenyl, tolyl, xylyl, naphthyl, etc., benzyl, phenylethyl, phenylpropyl. In one embodiment of the invention, some or all of the hydrogen atoms of the alkyl, aryl and arylalkyl radicals R 'are replaced by fluorine and / or chlorine atoms, bromine or iodine atoms and / or cyano radicals. In this case, R * corresponds, for example, to chloromethyl, trifluoropropyl, chlorophenyl, dibromophenyl, β-cyanoethyl, β-cyanopropyl or? cyanopropyl Preferably, however, at least 90 Z of the radicals R 'are methyl.

In a preferred embodiment of the invention f is equal to 0 or 1. With the nomenclature known to the person skilled in the art with M = (CH3)., Si0? / 2 D = (CH3) _Si0 /. T = (CH3) YES? 3 / MV1 = (CH; = CH) (CH3) 2Si01 / 2 and Dv ~ = (CH ^ = CH) (CH3) Si0;, 2 the following examples for component B-l can be given: VI T3D500M 2M3 and / or T6D300DVÍM4MVX4 The molar ratio in unsaturated radicals of type R can be chosen arbitrarily. In component B-1 the molar ratio in unsaturated residues of type R should be from 0.01 to mmol / g, particularly preferably 0.05-1 mmol / g and very preferably 0.1-0.7 mmol / g of component B-1. The viscosity of component B-1 is preferably between 10 and 100,000 mPa.s, particularly preferably 150-10,000 mPa.s, at 25 ° C. A preferred embodiment of the invention will be used as the component Bl the organopolysiloxanes described in De-A-43 28 657, since these are branched, the proportion indicated therein between the number of units of dioganosiloxane (units D) and the number of the branching points averages between 15 and 40, with at least one triorganosiloxane unit (unit M) and at most half of all the M units of unsaturated residues, with the remainder of the M units bearing only an unsaturated residue respectively and the content in unsaturated moieties being from 0.1 to 1 mmol / g. The branching points of component B-1 are preferably mono-organosiloxy units, ie trifunctional siloxy units (units T), which, however, can also be partially replaced by tetrafunctional siloxy units (Sio units, Q units). The end groups, free of saturated residues, of the branched organopolysiloxane serve as a 5 internal plasticizer. By means of the number of free end groups of unsaturated moieties (M units) the flexibility of the crosslinked film can be controlled. Examples of preferred B-1 components are the compounds of the formulas * V1 T5D200M 15M2 'T7D280MVX5M4' T6D180DVÍ2MVÍ4M4 Y 0 T8D250MVÍ7M3 Branched B-1 organopolysiloxanes having at least two unsaturated hydrocarbon groups can be prepared by customary methods, for example by hydrolysis of chlorosilanes and subsequent polymerization with low molecular weight cyclic diopho polysiloxanes. Methylhydrogenpolysiloxane B-2 preferably contains units of the general formula Hj (R7) kSiO (4 -? - k) / 2! VII) with R7 = monovalent hydrocarbon radicals, saturated, optionally substituted, with up to 10 carbon atoms from the group of alkyl, aryl, arylalkyl and / or alkenyl radicals having 2 to 8 carbon atoms, substituted and unsubstituted, where j and k are numbers integers with 0 < k = 3 and 0 = j = 2 as well as 0 < j + k < 4, preferably 0 < j < 1. Methylhydrogenpolysiloxanes B-2 are preferably linear. At least half of the D units preferably have hydrogen atoms directly bonded by the silicon (H (CH3) SiO groups) - Preferably the number of groups having hydrogen atoms directly bonded on the silicon is between 70 and 85% of the difunctional units. The molar ratio of the hydrogen atoms, bonded directly on a silicon atom, in the B-2 component can be chosen arbitrarily - within the scope of the structural limitations indicated above In component B-2 the molar ratio of the hydrogen atoms directly bonded to a silicon atom is between 0.01 and 17 mmoles, more preferably between 0.1 and 17 mmoles, and very particularly preferably between 1 and 17 mmoles / g of component B-2.

Examples of components B-2 are the compounds of the formulas D10 Mvi2DH ?: L and / or 2DV13DH8 with MH = H (CH3) 2SiO1 2 Y Preferably components Bl and B-2 are present in emulsion B in a quantitative proportion such that the molar ratio of the hydrogen atoms directly bonded to a silicon atom (SiH) in component B-2 with respect to the unsaturated moieties (Si-vinyl) in the component Bl is between 0.05 and 20, particularly preferably between 0.5 and 10 and very particularly preferably between 1 and 3. The emulsion B can also contain an organopolysiloxane, containing units of the general formula (R7) rSiO (4-r) / 2 (VIII) 8 where R7 is a monovalent, optionally saturated hydrocarbon radical substituted with up to 10 carbon atoms of the group of substituted and unsubstituted alkyl, aryl and arylalkyl radicals, which may be the same or different in the interior of the molecule and r takes whole values between 0 and 3. As the organopolysiloxane, a linear polydimethylsiloxane, closed in the end groups with trimethylsiloxy groups, is preferred, such as that marketed, for example, by Bayer AG under the name Baysilone @ M oil. The use of Baysilone M oils having a viscosity between 50 mm 2 S-1 and 5,000 mm 2 s-1 is especially preferred. Emulsion B also contains a catalyst from the platinum group, preferably from the elements platinum, rhodium, iridium, nickel, ruthenium and / or palladium, elemental on a support substance or in the form of its compounds. Preferably they are platinum compounds or platinum complexes such as for example H2 Ptclß, platinum-olefin complexes, platinum-alcohol complexes, platinum-vinylsiloxane complexes or even elemental platinum on a support substance, such as, for example, active carbon A1 0 0 Si02. A platinum vinyl siloxane complex is especially preferred as a catalyst. The platinum-vinyl siloxane complex then preferably has at least 2 olefinically unsaturated double bonds in the siloxane. These have been described, for example, in US-A-3 715 3 34. In this case, polysiloxanes, ie, for example, vinyl polysiloxanes, are included under the siloxane expression. The proportion of the catalyst, based on the sum of all the components, is preferably between 1 and 1,000 ppm, more preferably between 1 and 500 ppm and very particularly preferably between 25 and 250 ppm. The platinum group catalyst can also be dissolved in a part of polymer B-1. The emulsion B may also contain an inhibitor, suitable emulsifiers, thickeners and / or additives and customary auxiliaries (however it must not contain fillers). For the rest, reference will be made for obtaining emulsion B to EP-A-0 819 735.

Aqueous-colloidal silicic acid The aqueous-colloidal silicic acid (silica sol) consists of an aqueous colloid containing from 15 to 40% by weight, preferably from 25 to 35% by weight, of silicic acid with an average diameter of the particles of silicon. 6 to 50 nm, preferably from 7 to 15 nm. Such colloidal silicic acid systems are known to the person skilled in the art from the literature and can be obtained commercially. The aqueous emulsion of the separating agent according to the invention contains from 5 to 35% by weight, preferably from 8 to 24% by weight. by weight of the above-described silicone emulsion, A or B, as well as from 0.5 to 5% by weight, preferably from 0.8 to 4% by weight of the above-described aqueous-colloidal silicic acid, based on the total weight of the emulsion. The total silicone content of the release agent according to the invention is 2 to 20% by weight, preferably 5 to 15% by weight, based on the release agent. Additionally, the emulsion according to the invention can contain, independently of each other, agents for the preservation against germs or agents that prevent fermentation (bactericides), additional humectants, thickeners, stabilizers, additional emulsifiers, defoamers, corrosion inhibitors as well as dyes, preferably organic dyes partially hanging UV-activable. In particular, the emulsion according to the invention can contain from 0.01 to 0.1% by weight, preferably from 0.03 to 0.06% by weight, of the usual protective agents against germs, from 0.1 to 2% by weight, preferably from 0.3 to 0.6% by weight of thickeners / stabilizers, especially polysaccharides, from 0.1 to 2 by weight, preferably from 0.3 to 0.6% by weight of humectants , preferably nonionic humectants, which cause a homogeneous distribution (spray table) at the time of spraying on the surfaces by means of a better wetting, from 0.5 to 4 f by weight, preferably from 0.8 to 2. % by weight of polyethylene waxes, in particular of hard polyethylene waxes with an average particle size of 1 to 9 μm and with a melting point of between 90 and 110 ° C. • of 0.1 to 4 I by weight, preferably from 0.3 to 2% by weight of polytetrafluoroethylene in the form of micro-powder ( wax) which are known, for example, from DE-A-40 24 565 and which have a molecular weight between 30,000 and 200,000 and an average particle size of 1 to 20 μm.

The emulsions of the separating agent according to the invention can be mixed together according to customary methods, known to those skilled in the art, from the corresponding individual components. The emulsion used has a viscosity (DIN 53211, Ford 4mm vessel) of 20 to 80 seconds, preferably 30 to 60 seconds. The composition according to the invention is preferably used as a ase agent in vulcanization. In this case the ase agent is sprayed, before the insertion of the heating bellows (bladder) inside the preform (green) of the tire, on the heating bellows (heating membrane) and / or on the internal lining of the tire. the preform of the tire. . The amount of ase agent applied is in this case between 8 and 50 g / m2, preferably between 11 and 25 g / m2 of the sprayed surface. The required amount of pulverized mold ase agent per tire for traditional motor vehicle was from 6 to 40 g, preferably from 8 to 18 g. The heating bellows is then inserted into the tire. The heating membrane heats the preform of the tire and compresses it at the same time under high pressure in the negative mold, with which vulcanization occurs. The heating bellows of the tire are then removed again. The use of the composition according to the invention in the tire vulcanization process, described above, as a ase agent has the advantage that not only must the heating bellows be introduced and removed again slightly in the tire preform, but also that it be completely removes the air between the heating bellows and the inner lining of the tire from the intermediate cavity, caused by the formation of fine cracks in the semi-elastic coating that is formed. Occluded air means the rejection of the tires since there is no sufficient vulcanization under the air bubble. In addition, the heating bellows can easily be separated from the vulcanized tire. It is also possible with the composition of the separating agent according to the invention not to have to pulverize each tire in the case of a variable spray. Depending on the use of the silicone components that are crosslinked under the vulcanization conditions, the separations on the tire pushers can be removed. In addition, a part of the lining was installed on the heating bellows and positively influenced the life time of the bellows. Thus, it is possible to additionally cover the heating bellows with the separating agent to facilitate the start of new heating bellows in the presses. As a whole, not only the quality of the tires and the rejection of the tires can be improved by using the separating agent according to the invention, but also the costs per tire and the impurities (deposited dirt / reduction of waste) are drastically reduced, such as immediate consequence of the lower amount of spray solution used. The invention is explained in more detail by means of the following examples.

Examples Composition of the sealing agent according to the state of the art - aqueous dispersions of a solution for the internal pulverization of tires: Emulsions of Si-oil% in Peso Yes-oil, viscosity (1-1,000 m2 / S) 100 - 100,000 cst 5 - 15% Loads: Soot 1 2% Mica, talcum and similar 20 40% Glycols, humectants, 10 20% Water rest Quantity pulverized by tire preform for automobile 16-30 g. According to the state of the art, on average, 22 g of aqueous internal spray solution containing approximately 40 to 60 l of active compound (all components, except water) are pulverized simultaneously in a motor vehicle tire preform. This corresponds to approximately 11 g of active / pneumatic product for a motor vehicle. If the amount of the supernatant mist is calculated with approximately 25 to 30%, which does not reach the preform of the tire, then approximately 8 g of active / pneumatic product for motor vehicle remain. The individual components, which are indicated below in the table in g / preform for motor vehicle tire, meet the following requirements: In the following experiments the following components were used: Proxel GXL is a bactericide (commercial product of the ICI Firm). Kelzan D is a polysaccharide that acts as a thickener and stabilizer (commercial product of the firm Langer &Co.) Levasil 20OA30 (commercial product of the Bayer AG) is constituted by a silica sol with 30 ° by weight of SiO; and a specific surface of 2 00 MVg The size of the particles is from 7 to 15 nm. The Levasil 200 A309 causes a better hardening in the formulation and contributes, by dilation, to the formation of cracks in the coating, which in turn has a positive effect on ventilation. Lanco Wachs PE 1555 (commercial product of the firm Langer &Co.) is a hard polyethylene wax with an average particle size of 2.5 μm, melting point 102 ° C. Re opal LA 6 (commercial product of the Firm Re o) is a non-ionic humectant, which provides a homogeneous distribution (spray table when sprayed due to improved wetting on the inner lining-mix.

The oleaginous emulsion 1 (see comparative example 1, is Baysilon N (Bayer AG) The oleaginous emulsion 2 (see comparative example 2 is Baysilon VP AI 3632 (Bayer AG) The oleaginous emulsion 3 (see comparative example 2) is Baysilon VP AI 3628 Z 343 (Bayer AG) The oleaginous emulsion 4 (see comparative example 2) is Baysilon VP AI 3629 Z 344 (Bayer AG).

Example 1: Test with the crosslinking system by condensation.

In the case of tests with the composition according to example 1, approximately 13 g of product were sprayed. The content in active product (part in percentage of all the components in the composition minus water) is approximately 10%. If the amount of the supernatant mist of approximately 25-30% is taken into account, approximately 1.09 of active product / preform remains for tire.

In the tire factory, approximately 3,000 tires for motor vehicles with all sizes of tires were produced in a production test in the condensation crosslinking system according to the invention. All the vulcanized tires had an optimum quality. It should be noted the total transparency in the internal tire that makes it possible to recognize characterizing signs (for example such as bar code) Also in the case of possible overspray on the outer side no marks of any type or other failures could be determined. The polymer Si constitutes a layer of thin skin that polymerizes during vulcanization, eliminating in part the separating effect (absence of separation on the joint). This effect is demonstrated by a separation test under load according to DIN 53539. The function of ventilation, which is achieved by means of loads according to the state of the art, on the other hand in the case of systems containing loads, is also verified by means of the separation layer formed by the condensation crosslinking system according to the invention.

Comparison of sprayed / pneumatic quantity For motor vehicle.

Solutions for the internal spraying of tires. (Solid content of the pulverized quantity / preform for motor vehicle tire).

State of the art Composition according to example 1 Solid product / prefor Solid product / preform pneumatic tire vehicle, vehicle motor vehicle Approximately 11 g approximately 1.0 g Si-oil / preform for Si-Polymer / preform for vehicle tire pneumatic vehicle Car automobile approximately 1.32 g approximately 0.8 g The proportion of solid matter that has to be sprayed per tire preform, to achieve the desired effect, is reduced by approximately 90 T (11. g to l, 0 g). If the proportion of Si-oil or Si-polymer is compared, a reduction of about 40%, 1.32 g over 0.8 g, is found to occur). This means that the water load caused by the supernatant mist (supernatant mist = approx. 30 of the total amount sprayed) in the spray facilities is reduced to the quoted amounts "90% total, < 40% Si-oil-polymer), that is to say that the load in harmful materials is reduced in the same proportion.

Example 2: Test with an addition system catalyzed with Pt.

About 200 tires for motor vehicles of various standard sizes were sprayed and vulcanized. The results corresponded to those that were also obtained for the crosslinking system by condensation. All the tires had an optimum quality. These examples clearly show that better results were achieved with the use of less active product with the silicone reticent system according to the invention in comparison compared to the system of separating agents of the state of the art.

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 manufacture of the objects to which it refers. Having described the invention as above, the content of the following is claimed as property.

Claims (13)

1. Release agent comprising in an aqueous emulsion - a system consisting of at least two silicone components that react with each other under crosslinking, this system being chosen from the group consisting of (A) at least silicone components that react under condensation or (B) at fewer silicone components that react under addition, and an aqueous-colloidal silicic acid (silica sol).

2. Release agent according to the claim 1, characterized in that the silicone component system (A), which reacts under condensation, in an aqueous emulsion comprises a polydimethylsiloxane (A-1) closed in the end groups with SI-OH and a silicone (A-2) capable of crosslinking.

3. Release agent according to claim 1, characterized in that the silicone component system (B) which reacts under addition in an aqueous emulsion comprises a polysiloxane organ (Bl) having at least two unsaturated hydrocarbon groups and a methylhydrogen-polysiloxane (B-2) ).

4. Release agent according to any of claims 1 to 3, characterized in that the aqueous-colloidal silicic acid comprises from 15 to 40% by weight, based on the silica sol, of silicic acid with an average particle diameter of 6 to 50 nm.

5. Release agent according to any of claims 1 to 3, characterized in that it comprises -5 to 35% by weight of an emulsion with silicone components (A) that react with each other by condensation or an emulsion of the silicone components (B) that react with each other, by addition and from 0.5 to 5 l in weight of the acid silica. aqueous-colloidal (C), referred respectively to the total amount of the mold release agent.

6. Release agent according to any of claims 1 to 5, characterized in that it additionally contains components that are selected from the group formed by the germ protection agents, agents that prevent fermentation, humectants, thickeners, stabilizers, defoamers, corrosion inhibitors and dyes .

7. Process for the vulcanization of pneumatic tires, characterized in that the release agent as defined in one or more of claims 1 to 6 is applied to the heating bellows and / or the tire preform prior to vulcanization.

8. Process according to claim 7, characterized in that the application is carried out by spraying or brushing.

9. Process according to claims 7 or 8, characterized in that the applied amount of the mold release agent is from 5 to 50 g / m2.

10. Use of a composition comprising, in an aqueous emulsion - a system consisting of at least two silicone components that react with each other under crosslinking, this system being selected from the group consisting of (A) at least silicone components that react under condensation or ( B) at least silicone components that react under addition, and - an aqueous-colloidal silicic acid, as a release agent.

11. Use according to claim 1, in the manufacture of pneumatic tires.

12. Use according to claim 11, for the coating of the heating bellows and / or of the internal coating before vulcanization of the tire preform.

13. Use according to any of claims 10 to 12, in an amount of up to 50 g / m2 of the surface to be coated. SUMMARY The invention relates to a release agent free of fillers comprising an aqueous emulsion containing silicone systems crosslinking with each other and are silica. The release agent is especially suitable as a separating agent in the manufacture of tires.