CH469768A - Process for the production of a silicone rubber - Google Patents

Description

       

  



  Process for the production of a silicone rubber
The present invention relates to a method for producing a new type of silicone rubber.



   While excellent silicone elastomers are commercially available today, they are not as resilient or rebounding to their original shape as is desirable for a variety of uses. A measure of the elasticity or snappiness of a rubber is the difference between the energy required to stretch the sample and the energy recovered during relaxation, the same speed being assumed in both cases.



  The smaller this difference, the more elastic the rubber. The elasticity of a rubber can also be measured by determining the complex dynamic shear modulus and vectorially dividing it into two components, one of which is in phase with the tensile stress and the other is shifted by an angle of 90. The component in phase with the tensile load (real module) is comparable to a spring, while the phase-shifted component (imaginary module) is comparable to a complete damper. The greater the real module (G ') in relation to the imaginary module (G "), the more similar the properties of the material are to those of a steel spring.

   In the case of rubber which can be produced according to the invention, the ratio G '/ G "is high, and it is therefore very elastic and more elastic than previously known silicone rubbers.



   The resistance of the previously known silicone rubber to fatigue is not as great as desired.



  A rubber with high fatigue resistance is inevitably resistant to the formation of defects under repeated tensile stress and, moreover, requires a force in repeated stretching which is only slightly less than the force required in the first stretching. The elastomers obtainable according to the invention have extremely good fatigue resistance.



   There are already known silicone elastomers with good tensile strength properties, all of these elastomers contain a filler, e.g. B. a reinforcing silica filler. None of the unfilled silicone elastomers previously commercially available had good tensile strength. However, the production of a non-filled silicone rubber with high tensile strength is desirable, since in certain applications an unfilled rubber is preferable. It is also advisable to eliminate the filler for economic and manufacturing reasons.



   The aim of the present invention is therefore to produce a non-filled silicone rubber with improved elastic properties, improved fatigue resistance and good tensile strength, this rubber being achieved by an economical process with high efficiency.



   The invention relates to a process for producing a silicone rubber which is characterized in that (A) is mixed in an inert solvent to form a rubber thermosetting with peroxide (1) 100 parts by weight of organosiloxane polymer with an average of at least 200 silicon atoms per Molecule consisting essentially of units of the formula RnSi04-n
2, in which R is a methyl, phenyl or vinyl radical and n is the number 0, 1, 2 or 3, where n has an average value of 1.98 to 2.05, and in which an average of at least 0, 75 silicon-bonded methyl groups and an average of at most 0,

   15 silicon-bonded vinyl groups per silicon atom are present and no more than 50 mol% of the units mentioned (C6Hs) are eSiO units and which furthermore contains on average at least 2 silicon-bonded hydroxyl groups per molecule, (2) 40 to 175 Parts by weight of (a) siloxane whose siloxane units of the formula (C6H5) xR'ySio4-xy in the C6H5 the phenyl radical, R'ein a monovalent hydrocarbon radical different from the phenyl radical, x the number 0, 1 or 2, y the number 0 , 1 or 2 and the sum of x and y is 0, 1, 2 or 3, and that on average per molecule at least 2 silicon-bonded groups of the formula MO-, in which M is hydrogen,

   represents an alkali metal or a quaternary ammonium group, where x has an average value of 0.65 to 1.3, y has an average value of less than 0.4 and the sum x + y has an average value of 0.95 to 1.3, and where at least 60 mol% of the siloxane units are (C6H5) SiOl, 5 units, or (b) silanol of the formula (CHS) aR'bSi (OH) 4¯¯, "in the CsHs the phenyl radical, R'ein monovalent hydrocarbon radical different from the phenyl radical, a is the number 0, 1 or 2, b is the number 0, 1 or 2 and the sum of a and b is at least 1, which on average is 0.65 to 1.3 Contains phenyl groups per silicon atom, and in which the average value of b is less than 0,

   4 and the average value of the sum of a and b is between 1.0 and 1.3, with at least 60 mol% of the silanol having the formula (C6Hs) Si (OH) 3, and (3) a catalytic amount of one Condensation catalyst for silicon-bonded hydroxyl groups, the concentration of the starting materials in the solvent being such that no noticeable gelation takes place during heating, a reaction product being formed in which components 1) and 2) are mutually formed by the formation of a Si-O -Si bond are bound, and (B) the solvent is removed from the reaction product obtained in step (A), the product being sufficiently processed during this working step so that it remains essentially homogeneous.



   The silicone rubbers produced according to the invention are copolymers in which two main constituents are formed beforehand and linked to one another under conditions under which there is no excessive displacement of the siloxane bonds in (1). These compositions are essentially block copolymers in which blocks or segments of (1) RnSiO-n- 2 units can be linked to (2) either the phenylsiloxane or phenylsilanol. One of the most important features is that the blocks or segments of RnSiO4-n units must have at least 200 silicon atoms per block on average.



   Component 1 can be a dimethylsiloxane, so that the blocks have the formula [(CH3) SiO] Z, in which z has a value of at least 200. A characteristic formula of the block copolymers is, for example, [RnSiO. f-nLKCoHsR'ySiO. t-x-y] ,,), in which z is at least 200 and m is an integer and R, R ', n, x and y have the above meanings.



   It is clear that the copolymers obtainable according to the invention differ from co-hydrolysates which were obtained by simultaneous hydrolysis and condensation of methylsilanes with phenylsilanes. The latter products have completely random structures and do not show the properties of the block copolymers according to the invention.



   An essential reactant in the present process is (1) an organosiloxane of the unit formula R11SiO4n, in which R denotes a silicon, methyl, phenyl or vinyl radical. It is essential that there be on average at least 0.75 methyl groups per silicon atom and on average not more than 0.15 vinyl groups per silicon atom in this siloxane.



  All groups R are preferably methyl radicals. The siloxanes 1 used are generally diorganosiloxanes in which n has an average value between 1.98 and 2.05. It is essential that the siloxane 1 has no more than 50 mol% (CeHS) zSiO units and preferably contains on average at least 2 silicon hydroxyl groups per molecule. Of course, the siloxane 1 can also contain some residual reactive groups such as alkoxy radicals, which are frequently present in siloxanes.

   These reactive groups can condense with SiOH or SiOM groups in (2) or react in situ with water to form SiOH groups in the siloxane 1.



  Examples of residual alkoxy groups are the methoxy, ethoxy, isopropoxy and butoxy groups. Preferably, however, all of these radicals are hydroxyl groups. Although the siloxane can contain more than 2 such radicals, it should preferably have an average of 2 hydroxyl groups per molecule.



   It is essential that the siloxane 1 has an average of at least 200 silicon atoms per molecule. The siloxane 1 preferably has an average of 300 to 3500 silicon atoms per molecule. The best results are obtained with a hydroxyl-endblocked dimethylsiloxane with an average of 300 to 3500 silicon atoms per molecule. The hydroxyl-end-blocked dimethylsiloxanes with 5-10 mol% (CGH5) (CH3) SiO units and less than 5 mol-7, methylvinylsiloxane units produce elastomers with excellent properties at low temperatures.



   The siloxane 1 is reacted either with a siloxane containing phenyl radicals or a silanol containing phenyl radicals. The use of a siloxane containing phenyl radicals is preferred. Such a unit has the unit formula (CfiS) xR'ySiOg¯,; -y, in which R 'represents a monovalent hydrocarbon radical. Examples of such monovalent hydrocarbon radicals which are suitable in the present case are alkyl radicals such as the methyl, ethyl, tert-butyl or octadecyl radical; Alkenyl radicals such as the vinyl, allyl or butadienyl radical; Cycloalkyl radicals such as the cyclobutyl, cyclopentyl or cyclohexyl radical; Cycloalkenyl radicals such as the cyclopentenyl or cyclohexenyl radical; Aryl radicals such as

   B. the xenyl radical; Aralkyl radicals such as the benzyl or xylyl radical; and alkaryl radicals such as the tolyl radical. The siloxane containing phenyl radicals can only contain phenyl substituents, in which case x can be 0, 1 or 2 and preferably has an average value between 0.8 and 1.3; however, the siloxane can also contain phenyl radicals and other monovalent hydrocarbon radicals. The latter are then present in amounts of less than 0.4 radicals per silicon atom.

   At least 60 mol% of the phenyl radical-containing siloxane consists of (CcHs) SiOi. s units, while the rest can consist of SiO2 units and units such as R'SiOl 5, R'eSiO and (C6H5) R'SiO.



  In any case, the ratio of organic groups to silicon in this siloxane must fall within the range given above.



   R 'is preferably an aliphatic hydrocarbon radical having 1-6 carbon atoms, in particular a vinyl radical. The siloxane containing phenyl radicals preferably has 0.9-1.2 phenyl radicals per silicon atom where y = less than 0.15. An average of phenyl and R 'radicals per silicon atom of 0.95 to 1.2 including (x + y) and a content of (C5H5) SiOl, s units in the siloxane of at least 80 mol%. The best results are obtained with a hydroxyl containing siloxane which has an average of 0.98 to 1.05 phenyl groups per silicon atom and has no R 'groups (i.e., y = 0).



   The siloxane containing phenyl radicals preferably contains an average of at least 2 silicon hydroxyl groups or -OM groups per molecule. As in the case of the siloxanes 1, the phenyl radical-containing siloxane 2 can contain other reactive groups such as. B. have alkoxy groups. Preferably, however, all reactive groups are hydroxyl groups.



   Either of the two siloxanes used in the present process (i.e., both 1 and the phenyl containing siloxane) can be a homopolymer, a copolymer, or a mixture of siloxanes; furthermore, all organic radicals bonded to a silicon atom can be identical or different. Preferably, however, these siloxanes are either homopolymers or copolymers and not mixtures.



   Although siloxanes containing phenyl radicals are preferred as component 2, component 2 can also be a phenylsilanol or a mixture of silanols containing phenyl radicals. The silanols can be represented by the formula (C3Hs) nR'bSi (OH) 4 a b, in which R 'represents a monovalent hydrocarbon radical as defined above. A represents the number 0, 1 or 2 with a mean value of 0, 65-1, 3, b the number 0, 1 or 2 with a mean value less than 0, 4, while the sum of a + b averages 1 -1, 3 inclusive.



  It is essential that at least 60 mol% of a silanol mixture correspond to the formula (CGH5) Si (OH) 3.



  The silanol mixture preferably consists of at least 80 mol% of (CGHs) Si (OH) 2, while a has an average value of 0.9-1.2, b has an average value of less than 0.15 and the sum of a + b is between 1 and 1, 2. The best results are obtained with (C6H5) Si (OH) 3.



   40-175 parts by weight of the organosilicon compound 2 can be used per 100 parts by weight of the siloxane 1. It is preferred to use 50-160 parts by weight of (2) per 100 parts by weight of (1). Even better results are obtained with 60-140 parts by weight (2), and the most excellent results are achieved with 70-125 parts by weight of siloxane per 100 parts (1). The best results are achieved with 70-125 parts by weight of a monophenylsiloxane containing hydroxyl groups per 100 parts of a hydroxyl-endblocked dimethylsiloxane with 300-3500 silicon atoms per molecule.



   It is essential that the silicon hydroxyl group condensation catalyst (3) is used to catalyze the reaction between the organosilicon compound (2) containing phenyl groups and the diorganosiloxane (1). If you work with a siloxane containing phenyl radicals, which contains a catalytic amount of residual -OM groups, you do not have to add any further catalyst. In this case, components (2) and (3) of the reaction mixture coincide.

   Examples of suitable -OM radicals are -OK, -ONA, -OLi, -OCs and -ONR "4, where R" is an organic radical such as benzyl, ethyl, ss-hydroxy ethyl, methyl, - phenylethyl , Octadecyl or cyclohexyl radical. If (2) does not contain any -OM groups or an insufficient amount thereof, the catalyst is added separately.



   Preferred condensation catalysts are the alkali metal hydroxides KOH, LiOH, NaOH, CsOH and RbOH, KOH being particularly preferred. Potassium hydroxide is preferably used in an amount sufficient to provide one potassium atom per 100-100,000 silicon atoms. The best results are obtained with 1 potassium atom per 500-10,000 silicon atoms. This ratio is also preferred if the siloxane containing phenyl radicals contains (2) -OK groups. Organosilicon salts of such alkali metal hydroxides can also be used, for example (CH3) 3SiOK, (C6H5) (CH3) 2SiOLi, NaO [(CH3) 2SiO] 3Na, (CH3CH2) 3- -SiONa and (C3H5) 3SiOK.



   Dioxides of barium, strontium and calcium are also suitable as condensation catalysts. Acids such as hydrochloric acid and sulfuric acid can also be used.



   Furthermore, you can use alkali metal phenates and phenate derivatives as catalysts such. B. potassium phenolate, sodium p-phenolate methylphenolate, CsOC6H4- -C. Hs, [(CHs). NO], QH. (CH3) (CF.), (C.H.). (CH.,) POC6- -H4C6H11, ClC6H4OLi, (RbO) 2C6H3ONa and lithium phenate. These compounds correspond to the general formula
EMI3.1
 in which R "contains up to 10 carbon atoms and represents a monovalent, hydrocarbon radical, halogenated hydrocarbon radical or hydrocarbonoxy radical or a halogen atom, M 'is a tetraalkyl or tetraaryl nitrogen radical or a tetraalkyl or tetraaryl phosphorus radical, m is 0, 1, 2 or 3, z is 1, 2 or 3 and m + z = 1, 2, 3 or 4.

   Further condensation catalysts are the quaternary ammonium hydroxides and the organosilicon salts of such hydroxides. The organosilicon salts of quaternary ammonium hydroxides can be represented by the general formula YaSi (OQ) b04-a-h, in which Y is an alkali-resistant organic radical such as. B. a monovalent hydrocarbon radical or a fluorinated monovalent hydrocarbon radical and Q is a quaternary ammonium ion, a = 1, 2 or 3 and b has an average value of 0.1-3.



  Specific examples of such catalysts are β-hydroxy-ethyltrimethyl-ammonium hydroxide, benzyltrimethyl-ammonium hydroxide, didodecyldimethyl-ammonium hydroxide, (CH3) 3SiON (CH3) 4, (CsH) (CH3) 2SiON (CH3) 3 (CH2- -CH20H-, benzyltrimethyl) ammonium salt of dimethylsilanediol, octadecyltrimethylammonium hydroxide, tetradodecylammonium hydroxide, tritetradecylmethylammonium hydroxide and hexadecyloctadecyldimethylammonium hydroxide. Primary, secondary and tertiary amines, which preferably have at least a dissociation constant of 10-1 ″, can be used as catalysts.

   Suitable amines are e.g. B. the following: brucine, sec-butylamine, cocaine, diethylbenzylamine, diethylamine, diisoamylamine, diisobutylamine, dimethylamine, dimethylaminomethylphenol, dimethylbenzylamine, dipropylamine, ethylamine, ethylenediamine, hydrazine, isoamylamine, methylamine, methyl tertiamylamine, methyl isopropylamine, methyl isopropylamine, hand. -Octylamine, tert.

   Nonylamine, piperidine, n-propylamine, tert-octadecylamine, quinine, tetramethylenediamine, triethylamine, triisobutylamine, trimethylamine, trimethylenediamine, tripropylamine, L-arginine, L-lysine, aconitine, benzylamine, cinchonidine, codeine, conine, emetine, -Methoxybenzylamine, m-methoxybenzylamine, p-methoxybenzylamine, N, N-methoxybenzylamine, o-methylbenzylamine, m-methylbenzylamine, p-methylbenzylamine, N, N-methylbenzylamine, morphine, nicotine, novocaine base, # -phenylamylamine, A-phenylamine, ss-phenylethylamine, ss-phenylethylmethylamine,?

  -Phenylpropylamine, N, N-isopropylbenzylamine, physo stigimin, piperazine, quinidine, solamine, sparteine, tetramethylquanine, thebaine, tert-butyl-2, 4-dinitrophenylamine, tert-butyl-2-hydroxy-5-nitrobenzylamine, tert. -Butyl-4-isonitrosoamylamine, tert-octylamylamine, tert-octyl-2- (P- -butoxyethoxy) -ethylamine, 2, 4, 6-tris- (dimethylamino) -phenol, aniline, phenylhydrazine, pyridine, quinoline, p bromophenylhydrazine, p-nitro-o-toluidine, ss-ethoxyethylamine, tetrahydrofurfurylamine, m-aminoacetophenone, iminodiacetonitrile, putrescine, spermine-N, N-dimethylaminoprophylpentamethyldisiloxane, p-toluidine and veratrine.



   Also suitable as catalysts are the condensation products of aliphatic aldehydes and aliphatic primary amines such as. B. the condensation products of formaldehyde and methylamine, actaldehyde and allylamine, crotonaldehyde and ethylamine, isobutyraldehyde and ethylamine, acrolein and butylamine, a, p-dimethyl acrolein and amylamine, butyraldehyde and butylamine, acrolein and allylamine and formaldehyde and heptylamine.



   Aromatic sulfonic acids such as. B. Ben zolsulfonsäure and p-toluenesulfonic acid are used as catalysts. Sulfonic acid catalysts of the general formula XSOsH, in which X is a perfluoroalkyl radical with fewer than 13 carbon atoms, an H (CF2) eCF2 radical or an F (CFz) e -CFHCF2 radical with c = 0, are particularly suitable , 1 or 2, for example CFsSO3H, C2FsSO3X C4F9S03H, C8F1TS03H, HCF2-CF2- -SO3H, CF ^ HSO3H and CFsCFHCF2S03H.



   Another type of catalyst for the condensation of silicon hydroxyl groups are the alkali metal alkylene glycol monoborates such. B. amine or ammonia. The amine can contain one or more amino groups as well as organic functional groups which have no free active hydrogen. Preferred salts are the aminocarboxylic acid salts with at least 6 carbon atoms. Polycarboxylic acid salts can also be used. The amine salts can be normal, acidic or basic.

   Suitable examples are the following: bis-2-ethylhexylamine acetate, triphenylsilpropylamine formate, trimethylsiloxydimethylsilhexylamine hexoate, 4,4-diaminobenzophenone butyrate, 4, 4 'diaminodiphenyl ether decanoate, tri-n-butylamine-acrylate, 3, 4-di-butylamine-acrylate -caproate, aniline octanoate, didodecylamine-o-chlorophenoxyacetate, ethylamine-3-ethoxypropionate, diethylenetriamine monooleate, diisopropylamine palmate, trimethylamine stearate, benzylhydrazine hexoate, 2.5 dimethylpiperazine tetramethylguanate, 2-ethyl hexoate, bis (octadecylamine) sebacate, ethylenediamine di-hexoate, tetraethylene pentaamine diphosphate, 1,

   2-aminopropane phenyl phosphate and ammonium stearate together with the salts of other of the above amines and acids.



   The catalysts described in Canadian Patent No. 601 296 can also be used in the process according to the invention. The catalysts described there are β-aminobutyric acids of the general formula
EMI4.1
 Lactams of such acids of the formula
EMI4.2
 and cc-amino acids of
EMI4.3

Organic isocyanates without active free hydrogen, which have only one isocyanate group per molecule, are also suitable as condensation catalysts.



  Such isocyanate catalysts are described in Canadian Patent 591,630. Specific examples of isocyanates which can be used in the present invention are the aliphatic isocyanates such as methyl isocyanate, butyl isocyanate, octadecyl isocyanate and hexenyl isocyanate; cycloaliphatic isocyanates such as cyclohexyl isocyanate and cyclohexenyl isocyanate; and aryl isocyanates such as xenyl isocyanate, bromophenyl isocyanate, anthracyl isocyanate, p-dimethylaminophenyl isocyanate and p-methoxyphenyl isocyanate.



   Certain amine salts can also be used as catalysts in the present process. These amine salts are the reaction products of basic amino compounds; H. Ammonium compounds or organic amines (including organosilyl amines) and phosphoric or carboxylic acids. Such amine salts are described in Canadian Patent 652 165 be. The term basic amino compound is to be understood as meaning compounds having at least 1 nitrogen atom on more than 3 carbon atoms.

   The basic amino compound can be a primary, secondary or tertiary amine, a silyl organic amine, a poly formula
EMI4.4
 in which R "'represents a monovalent aliphatic hydrocarbon radical with 5-30 carbon atoms, R" "represents an aliphatic hydrocarbon-acyl group with 5-30 carbon atoms and Y'-methyl or hydrogen. Specific examples of such compounds are N-caproylglycine, N-caproylsarcosine, N Palmityl sarcosine, N-oleylglycine, N-benenylglycine and N-linoleylglycine.



   The carboxylic acid salts of certain metals can also be used as catalysts. Examples of metals that can be used are lead, tin, nickel, cobalt, iron, cadmium, chromium, zinc, manganese, aluminum, magnesium, barium, strontium, calcium, cesium, rubidium, sodium and lithium. Particularly suitable salts are the naphthenates of the above metals such as. B. lead naphthenate, cobalt naphthenate and zinc naphthenate; Salts of fatty acids such as B. iron 2-ethyl hexoate, tin (II) -2- ethyl hexoate and chromium octoate; Salts of aromatic carboxylic acids such as dibutyltin dibenzoate; Salts of polycarboxylic acids such as dibutyltin adipate and lead sebacate; and salts of hydroxycarboxylic acids such as dibutyltin dilactate.



   The amount of catalyst required to achieve the conversion depends on numerous factors such as temperature and reaction time, type of catalyst and the reactants. For this reason, no numerical limits can be given for the catalyst concentration. However, the optimum concentration for any given system can easily be determined by heating a mixture of (1) and (2) in solution and determining the time required to give a peroxide vulcanizable product.



  In general, the condensation catalyst for silicon hydroxyl groups is used in the same amounts in which it is used in siloxane condensations in general.



   The organosilicon compounds (1) and (2) described above are mixed in a suitable solvent and heated at a temperature sufficient to give a product vulcanizable by peroxide. The temperature and the heating time required depend on the organosilicon compounds, the catalyst and the concentration of the organosilicon compounds in the solvent. If the mixture is heated too long, the vulcanized product will flow too much at 150-250 and the physical properties cannot be measured. On the other hand, if the mixture is not heated long enough, the resulting rubber will have poor physical properties.

   It is preferred to heat the mixture at the reflux temperature for a sufficient time to obtain a product which can be vulcanized by peroxide. Cooking times of 0.5 to 20 hours are generally sufficient. Here, too, no generally applicable numerical limit for heating time and temperature can be specified. The optimum reaction time is determined by observing the time which leads to a product vulcanizable by peroxide, this time depending on the organosilicon compounds, the catalyst used and the solids concentration. Although it is not necessary to remove the byproducts from this reaction, it is preferred that a substantial proportion of these byproducts be removed during the heating step.

   The by-products can be removed at the moment of their formation or towards the end of the heating stage; preferably the former method is used.



   Although it is advisable to add the entire amount of the organosilicon compound (2) before heating, a small amount of this material can be added after heating and deactivating the catalyst, but before removing the solvent. However, it is essential that at least 40 parts by weight of the organosilicon compound 2 per 100 parts by weight of the siloxane 1 is present before the heating.



  Although up to 135 parts by weight of organosilicon compound 2 is added after heating and deactivation of the catalyst, it is preferred to add only 80 parts or less at this point.



   Any inert solvent in which both siloxane 1 and organosilicon compound 2 are soluble at the reaction temperature can be used. The term inert means that the solvent does not noticeably react with the siloxanes or the catalysts. Aromatic solvents such as xylene, benzene or toluene are preferred. However, other solvents such as aliphatic hydrocarbons, e.g. B. petroleum ether, halogenated hydrocarbons, dichlorobenzene or esters. The reaction product should also be soluble in the solvent used, so that the product remains essentially homogeneous during the removal of the solvent.



   The only limitation on the concentration of organosilicon solids in the solvent is that no noticeable gelation should occur during heating. The maximum permissible solids concentration depends on the solvent, the organosilicon compound and the catalyst. The solids concentration is preferably less than 40-50% by weight, based on the total weight of the mixture.



  There is no lower limit to the solids concentration, since gelation is not a problem at lower concentrations. However, the economy of the system decreases at solids concentrations below 10% by weight.



   Although it is not of critical importance, better results are obtained if the catalyst is deactivated after the heating step, especially if the rubber is to be stored for a long time before vulcanization, since the reaction continues and the physical properties are impaired. Methods for deactivating catalysts are known and generally consist in removing and / or neutralizing the catalyst. Preferably at least a substantial part of the catalyst is removed from the reaction product. When using alkali metal hydroxides, the reaction product is preferably saturated (carbonated) with CO = saturated (carbonated) after the end of the heating and then filtered off or decanted off from the precipitate formed. The best results are obtained when the reaction product is carbonated and filtered.

   Another method for deactivating the catalyst consists in adding fumed silica to the reaction product with subsequent decantation of the precipitate. The reaction product can also be briefly boiled before decanting. The deactivation of the catalyst is a preferred but not a necessary step in the present process. The method of deactivation depends, of course, on the specific catalyst.



   The solvent must be removed from the reaction product prior to vulcanization of the rubber.



  During this process step, the reaction mixture must be agitated enough to obtain the product essentially homogeneous. This result is achieved e.g. B. by hot rolling, the temperature and treatment time should of course be sufficient to drive off substantially all of the solvent.



  The conditions of this process, e.g. B. The speed and pressure of the rollers should be selected so that the product remains essentially homogeneous during the process. Besides this method, however, the solvent can also be used in other ways, e.g. B. removed during a mixing operation, provided that the conditions are such that a substantially homogeneous product is maintained. The solvent is preferably removed at a temperature close to its boiling point.



   As set out in Example 10, a small amount of a low molecular weight liquid hydroxyl endblocked diorganosiloxane (less than 200 silicon atoms per molecule) can be added to the reactants after removal of the solvent, which can be a conventional liquid diorganosiloxane. Examples of such siloxanes are dimethylsiloxane, phenylmethylsiloxane, methylpropylsiloxane and a copolymer of 95 mol% phenylmethylsiloxane and 5 mol% methylvinylsiloxane.



   The rubber obtainable according to the invention is vulcanized by heating it to a temperature which is above the decomposition point of the peroxide vulcanizing agent. Organic peroxides suitable as vulcanizing agents are e.g. B. benzoyl peroxide, tert-butyl perbenzoate, dicumyl peroxide, di-tert-butyl peroxide, tert-butyl peracetate, 2,5-dimethyl-2,5-dihydroperoxyhexane, bis (2,4-dichlorobenzoyl) peroxide. These peroxides can be used in amounts of 0.1-10 parts by weight per 100 parts of the siloxane.



   This rubber is preferably cured by vulcanization under pressure, usually at temperatures between 120 and 200, with vulcanization times of 5-15 minutes being sufficient. Post-curing at 150-250 for 24 hours is generally an advantage.



   If SiO2-containing fillers with organosilyl units on the silica substrate are incorporated into the rubber compound, a small amount of cyanoguanidine can be used in addition to the peroxide vulcanizing agent. The use of cyanoguanidine as a vulcanizing agent is described in Swiss Patent No. 443,673.



   The rubber products obtainable according to the invention can be used for the production of elastomers with high tensile strength without the addition of fillers.



  Small amounts of filler are permitted, however. B. those as described in Canadian Patent 538,973 are suitable.



   The compositions of the present invention may also contain other additives such as anti-deformation additives, heat stabilizers, antioxidants, pigments and other materials normally used in the manufacture of silicone rubber.



   The elastomers obtainable according to the invention have excellent elasticity and high fatigue resistance, such as B. shown in Examples 8 and 9. They also have high tensile strength at normal and elevated temperatures. It was surprising that these strengths could be obtained with a rubber which does not contain a silica filler.



   The elastomers according to the invention can be used where conventional silicone elastomers are used, since they have excellent thermal properties. Their elasticity and / or high fatigue resistance make them particularly suitable for many purposes.



   In the following examples, the viscosities were measured at 25, unless otherwise stated.



   The following materials were used in the examples:
A. a hydroxyl-containing monophenylsiloxane
B. a hydroxyl-free monophenylsiloxane
C. [(CsH5) SiOl, 5] 8 and D. a hydroxyl-free monophenylsiloxane with bound potassium.



   example 1
The composition, reaction conditions and elastomeric properties of the samples prepared in this example are shown in Table 1. 100 parts by weight of a hydroxyl end-blocked dimethylsiloxane and 100 parts by weight of a monophenylsiloxane of the type shown in Table 1 were mixed in toluene and placed in a three-necked flask provided with a stirrer and a trap to trap the azeotrope. The mixture was refluxed for the specified time with stirring and removal of the water formed. The reaction mass was then carbonated with dry ice at room temperature and filtered.



  Then the solvent was removed on a two roll system. Unless otherwise stated, 2 parts of tert-butyl perbenzoate and 100 parts of dimethylsiloxane were then added, vulcanized at 150 for 10 minutes under pressure and then heated for one hour at 150 in a hot air oven. The sample was then post cured at 250 for the specified time. Tensile strength and elongation at break were determined after curing at 250 for 24 and 72 hours. The catalyst concentration is given as the ratio of potassium atoms to the total amount of silicon atoms in the siloxane. Potassium hydroxide, potassium phenylate and potassium hexylene glycol monoborate were added in the appropriate amounts to achieve the desired ratio.

   The following formula is used for potassium hexylene glycol monoborate
EMI6.1
 to understand. The percentage of solids in the toluene is given in Table 1 for each sample. The stated viscosity of the reaction mass is the viscosity of the overall composition including the solvent.



   Example 1 illustrates the results obtained by changing the average molecular weight, measured via the viscosity of the hydroxyl endblocked dimethylsiloxane. Sample No. 1 could not be vulcanized. The example also shows the results obtained by changing the cooking time. If the sample is refluxed too long, the flow of the vulcanized product at 150 will be so strong that the physical properties cannot be measured. On the other hand, if the sample is not refluxed long enough, the physical properties of the product are poor.



  Example 1 also shows that a hydroxyl group-free monophenylsiloxane cannot be used, cf. B. Samples 11, 12, 13 and 14. It can also be seen that a hydroxyl-group-free monophenylsiloxane which contains potassium is useful, see Sample II 15.



   Example 2
This example compares the results obtained by varying the weight ratio of hydroxyl-endblocked dimethylsiloxane to hydroxyl-containing monophenylsiloxane. The hydroxyl endblocked dimethylsiloxane had a viscosity of 14,100 cSt in this example. The monophenylsiloxane had hydroxyl groups. The results of the experiments of Example 2 are summarized in Table II; in each case, 20% by weight of organosilicon solids in toluene were present before refluxing. Potassium hydroxide was used in amounts such that there was one potassium atom for every 2000 silicon atoms. Unless otherwise stated, 2 parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane were used for vulcanization.

   The procedural measures were the same as in Example 1.



   Example 3
This example compares the results that are obtained when adding additional monophenylsiloxane after refluxing and filtering, but before removing the solvent on the one hand and on the other hand when adding this additional amount of monophenylsiloxane before refluxing. As shown under Sample No. 6 in Table III, it is necessary to use at least 40 parts of monophenylsiloxane per 100 parts of dimethylsiloxane in the reflux stage. The procedural measures and test methods are already described in Example 1. In each case, 100 parts by weight of a hydroxyl group-containing dimethylsiloxane having a viscosity of 14,100 cSt. and a hydroxyl group-containing monophenylsiloxane is used.



   The term initial parts by weight denotes the amount of monophenylsiloxane added before refluxing. More monophenylsiloxane was added after boiling and filtering, but before the solvent was removed on a hot roller. The amount of toluene used was such that a concentration of siloxane solids of 20% was achieved. Unless otherwise stated, vulcanization was carried out with 2 parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane. The K / Si ratio was 1/2000.



   Example 4
The results summarized in this example were made by changing the solvent and the
Received catalyst. In each case, 100 parts of a hydroxyl endblocked dimethylsiloxane having a viscosity of 14,100 cSt. used per 100 parts of a hydroxyl group-containing monophenylsiloxane. Catalyst and catalyst concentration are given in Table IV. The viscosity of the reaction mass (including solvent) before and after refluxing is also given in Table IV. Unless otherwise stated, 2 parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane were used for vulcanization. The procedural measures and test methods are already described in Example 1.



   Example 5
In this example, the elastomeric properties of samples perforated at different solids concentrations at the reflux are compared. 100 parts by weight of a hydroxyl endblocked dimethylsiloxane having the viscosity given in Table V were used per 100 parts of a hydroxyl-containing monophenylsiloxane. The catalyst consisted of potassium hydroxide in quantities sufficient to make one
Ratio of 1 K / 2000 Si. The viscosity of the samples was determined after refluxing but before removing the solvent. In each case, vulcanization was carried out with 2 parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane. Procedural measures and test methods see example l.



   Example 6
This example compares the results obtained by changing the amount of vulcanizing agent. The present example further illustrates the use of a reinforcing filler. In each case, 100 parts of a hydroxyl endblocked dimethylsiloxane having a viscosity of 14100 cSt were used per 100 parts of a hydroxyl group-containing monophenylsiloxane. The viscosity of the reaction mixture (including solvent) before and after refluxing is given in Table VI; Process measures and test methods compare Example 1. The amount of reinforcing filler is given in parts by weight, based on 200 parts by weight of the rubber composition.

   The filler was incorporated into the rubber while it was being mixed on the roller.



  In Table VI, the organosilicon solids concentration in the toluene prior to refluxing was in each case 20% by weight. The parts by weight of tert. Butyl perbenzoate refers to 100 parts of dimethylsiloxane.



   Example 7
In this example the results are compared with varying catalyst concentrations. In each case, 100 parts of a hydroxyl endblocked dimethylsiloxane having a viscosity of 14,100 cSt per 100 parts of a hydroxyl-containing monophenylsiloxane were used. The organosilicon solids content of the toluene before refluxing was 20% by weight. The potassium hydroxide concentration is given in Table VII. The viscosity of the reaction mass (including solvent) after refluxing is also listed in the table mentioned; For procedural measures and test methods, see Example 1. In each case, vulcanization was carried out with two parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane.



   Example 8
The elasticity and high fatigue resistance of the rubber obtainable according to the invention is demonstrated in the following example. The rubber obtainable according to the present invention has less energy loss (i.e., higher fatigue resistance) upon repeated tension than the conventional silicone rubber. The elastomers obtainable in accordance with the invention are also very elastic, as can be seen from the low energy loss that occurs during relaxation after tension.



   Two of the samples prepared in the preceding examples were compared with conventional silicone rubber with regard to their fatigue resistance and elasticity properties.



   The comparison rubber was prepared by adding 60 parts by weight of a trimethylsilyl-treated cogel with a surface area of at least 300 m2 / g with 100 parts by weight of a dimethylsiloxane rubber with 0.142 mol% vinylmethylsiloxane and 7.5 mol .-% phenylmethylsiloxane mixed and treated on a hot roller. The remaining solvent was removed by heating to 150 for one hour. The rubber was then rolled with the addition of 0.5 parts by weight of tert-butyl perbenzoate and molded under pressure at 150 for 10 minutes, then heated to 150 for one hour and 250 for 24 hours.

   This rubber is labeled E in Table VIII.



   The samples were tested by stretching each at a constant rate of 5.1 cm per minute until the tensile stress indicated in Table VIII was reached. The tension was then released in such a way that the sample relaxed at a constant rate of 5.1 cm per minute. The stress relaxation cycle was then repeated as indicated in Table VIII (n). With successive pulls, the sample was stretched to the same tension that was achieved in the first pull. The tensile stress at each renewed pull is given in the table in the form of the percentage elongation. The expansion energy E is determined by the area under the expansion curve and can be summed up for the desired level of tension or tension.

   The column El-E "indicates the difference between the energy required for tensioning the sample in the first pull (E1) and the energy in the following pull (En). N denotes the number of tensioning processes. The smaller the energy difference, the more The relaxation energy R represents the force that is recovered when the sample is relaxed from the tensioned to the untensioned state at a constant speed of 5.1 cm / min.

   The energy loss during a stress-relaxation cycle (En-Rn) is the difference between the energy required to expand the sample (En) and the amount of energy recovered during relaxation, both of which are measured at constant speed. In general, the lower the energy loss during such a cycle, the more elastic a rubber is. The percentage of energy lost during a stress relaxation cycle [100 (En-Rn)] is a measure of the elastic properties of rubber. In general, the lower this energy loss, the more elastic the rubber.



   As can be seen from Table VIII, the Ei-En values for the elastomers obtainable according to the invention are lower than for conventional silicone elastomers. This proves the increased fatigue resistance of the rubber according to the invention. The lower energy loss during the stretch-relaxation cycle proves the increased elasticity properties.



   Example 9
In this example, the elastomers obtainable according to the invention are compared with known silicone elastomers with regard to the complex dynamic shear modulus, as can be seen in Table IX. The properties of the elastomers according to the invention are comparable to those of a helical spring. A steel coil spring is almost ideally elastic, which is determined by the fact that loading and deformation are in phase with each other. On the other hand, with a perfect damper there is a phase shift of 90 between deformation and force.



  Since all elastomers (both silicones and organic elastomers) are viscoelastic materials, the deformation lies behind the tension by a certain angle. The smaller this angle, the more elastic or spring-like the material is. The voltage can be broken down vectorially into two components, one of which is in phase with the deformation, the other 90 out of phase. If one divides each of these vector components of the stress by the deformation, one obtains the real and the imaginary module. This can be represented vectorially as follows
EMI8.1
 G is the complex dynamic shear modulus, G 'is the real or elastic component of the complex modulus, while G "is the imaginary part of the complex modulus.

   The relationship between real and imaginary module can be represented either by the tangent or the cotangent of the angle. The greater the cotangent of (G '/ G "), the greater the real modulus and the more elastic or spring-like the material. The elastomers according to the invention are extremely elastic, as can be seen from the large values for cotangent / \. The real modulus of these products is greater than that of the previously known silicone rubber.



   An electronic measuring device was used to determine these properties. The device and the calculations for evaluating the measurement results are described in:
1. Measurements of Mechanical Properties of Poly isobutylene at Audiofrequencies by a Twin Transducer, R. S. Marvin, E. R. Fitzgerald and J. D. Ferry,
J. Applied Physics 21, 197 (1950).



   2. Dynamic Properties of Rubber, S. D. Gehman, D. E.



   Woodford and R.B. Stambough, Ind. Eng. Chem, 33, 1032 (1941).



   The device comprises a metal lamella which is suspended between two voice coils (loudspeaker units with the core removed). One of the voice coils is operated by a suitable electronic device which causes the metal lamella to vibrate. This induces a voltage in the other coil. The real modulus G ', the imaginary modulus G "and the cotangent / of a material attached to the center of the metal lamella and a stationary part of the device can be determined by suitable control of the two signals and appropriate calculations. Experiments were carried out at various percent bending or Deformation of the specimen, the results differing depending on the degree of bending.

   Percent deflection is the amplitude of the vibration induced on the lamella divided by the thickness of the test sample and multiplied by 100. Comparisons can then be made between the various materials tested in Table IX or the cotangent at a given percentage Bend. The higher the cotangent, the more elastic the material.



   The following silicone rubber was produced:
100 parts by weight of a high molecular weight hydroxyl endblocked copolymeric siloxane of 99.858 mol .-% dimethylsiloxane and 0.142 mol .-% methylvinylsiloxane were acid filler with 60 parts by weight of a reinforcing silica, 8 parts by weight of a hydroxylated liquid dimethylsiloxane with a hydroxyl group content of 3 to 4 wt .-% and 0.5 parts by weight of tert-butyl perbenzoate mixed on a roller. The rubber was then molded under pressure at 150 for 10 minutes and then heated at 150 for one hour and at 250 for two hours.

   The filler used was silica, produced by converting sodium silicate in solution to a silica sol in the presence of an ion exchange resin, refluxing the sol with HCl to form a silica with an average surface area of 250-500 μm and treating this silica with saturation of the surface with Dimethylsilyl units through SiOSi bonds. This rubber sample is labeled F in the table.



   Example 10
This example shows that various vulcanizing agents can be used for vulcanizing the rubber according to the invention. The addition of a small amount of a low molecular weight hydroxyl endblocked liquid diorganosiloxane after removal of the solvent together with 100 parts of a hydroxyl endblocked dimethylsiloxane (14100 cSt) and 100 parts of a hydroxyl group-containing monophenylsiloxane is also illustrated. The samples were vulcanized under pressure at the times and temperatures given in Table X. For procedural measures and test methods, see example l. The low molecular weight hydroxyl endblocked diorganosiloxane was added in each case after the solvent had been removed.

   Furthermore, the organosiloxane solids content in the toluene before reflux was in each case 20% by weight and the amount of vulcanizing agent was two parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane. The following materials were used in this example:
G.

   A hydroxyl endblocked liquid dimethylsiloxane with a hydroxyl content of about 3.5
Wt%; H. A hydroxyl endblocked liquid Phenylme thylsiloxan with a hydroxyl content of about
3.5% by weight; I. A hydroxyl endblocked liquid siloxane copolymer with a hydroxyl content of about 3, 5 wt .-%, with a content of about 40 mol .-% phenylvinylsiloxane and 60 mol .-% phenylmethylsiloxane.



   Example 11
This example shows that the process according to the invention can be modified by refluxing the reaction mixture either without removing water or with removing water only in the last stages. 100 parts by weight of a hydroxyl endblocked dimethylsiloxane with a viscosity of 2250 cSt were used per 100 parts of a hydroxyl group-containing monophenylsiloxane.



  Before refluxing, there was 20% by weight organosiloxane solids in toluene. Potassium hydroxide was used as the catalyst in an amount sufficient to produce a ratio of one potassium atom to 2000 silicon atoms. The viscosity was measured after the reaction mixture (including solvent) was boiled. For procedural measures and test method, see Example 1, with the exception that the reaction mixture was refluxed in each individual case for the time indicated in the table without removing water. In some cases, the boiling was continued to remove the water formed. In each case, vulcanization was carried out with two parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane.



   Example 12
100 parts by weight of a hydroxyl endblocked siloxane copolymer with a viscosity of about 51,700 cSt at 25, which contained about 92 mol% dimethylsiloxane, about 7.5 mol% phenylmethylsiloxane and 0.5 mol% methylvinylsiloxane, 120 parts of a hydroxyl group-containing monophenylsiloxane and sufficient amounts of KOH to produce a ratio of one atom of potassium to 2000 silicon were dissolved in toluene at a solids content of siloxane of about 25% by weight. The mixture was then placed in a three-necked flask equipped with a stirrer and a trap for the azeotrope and refluxed for three hours with stirring and removal of the water formed.

   The reaction mass was then carbonated with dry ice at room temperature and filtered. The solvent was removed on a hot roller, after which two parts by weight of tert-butyl perbenzoate per 100 parts of diorganosiloxane copolymer were vulcanized under pressure for 10 minutes at 150, then heated to 150 in a forced-air oven for one hour, after which the sample was post-cured at 250 has been. The tensile strength and the elongation at break were determined after curing for 24 and 72 hours at this temperature. The sample had the following physical properties.



   Table XII
Elastomeric properties
24 hours at 250 C 72 hours at 250 C tensile strength% tensile strength% kglmm2 elongation kg / mm2 elongation
0, 89 160 0, 93 125
Example 13
100 parts of a hydroxyl end-blocked dimethylsiloxane with a viscosity of about 14 100 cSt at 25, 100 parts by weight (CsH.,) Si (OH) 3 and a sufficient amount of KOH to achieve a ratio of 1 atom of potassium to 2,000 silicon atoms were added in 800 parts by weight Parts of toluene mixed. The mixture was then refluxed for 2 hours with stirring and removal of water in a three-necked flask equipped with a stirrer and an azeotrope.

   The reac tion mass was then saturated with carbon dioxide at room temperature with the aid of dry ice and filtered.



  The solvent was removed on a hot roller, after which 2 parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane were added and the sample was vulcanized under pressure for 10 minutes at 150, then it was heated to 150 for one hour in a forced-air oven then post-cured at 250 for the specified time. The tensile strength and elongation at break were measured after curing for 24 and 72 hours at this temperature. The sample shows the physical properties given in the following table.



   Table XIII
Elastomeric properties
24 hours at 250 C 72 hours at 250 C tensile strength% tensile strength% kg / mm2 elongation kg / mm2 elongation
0, 57 345 0, 63 240
Example 14
100 parts by weight of a hydroxyl endblocked dimethylsiloxane and 100 parts of the designated hydroxyl group-containing monoorganosiloxane and catalyst were mixed in toluene at a siloxane solids concentration of 20% by weight. The viscosity of the dimethylsiloxane and the type of monoorganosiloxane and catalyst are given in Table XIV. The mixture was placed in a three-necked flask equipped with a stirrer and a trap for the azeotrope.

   It was then refluxed for one hour with stirring and removal of the water formed, cooled to room temperature, saturated with carbon dioxide with the aid of dry ice and filtered. The solvent was removed on a hot roller mill, after which 2 parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane were added. The rubber was then vulcanized under pressure at 150 for 10 minutes and heated at 150 in a forced air oven for 1 hour.



  The sample was then post-cured at 250 with the cure times given in Table XIV. For test procedure see example 1.



   Table 1 Siloxane-2; Compilation of reaction elastomer properties conditions
24 hours at 250 C 72 hours at 250 C
E Mo-'t! -T! Visc. in cSt concentrate (K / Si-Verb @% solids @ in toluene hours on
Reflux visc. Sugfestigke in cSt at the end of the cooking area
Tensile strength% elongation
1. 24.5 A KOH 1 / 2,000 40 1 2.2 not vulcanizable, sample flowed at 250
2.2, 250 A KOH 1/2, 000 20 0, 5 5, 4 0, 64 370 0, 77 180
3. 2, 250 A KOH 1/2, 000 20 1 4, 9 non-vulcanizable, sample float at 250 4. 12, 900 A KOH 1/2, 000 20 1-0, 85 450 0, 95 260
5. 12, 900 A KOH 1/2, 000 20 3-not vulcanizable, sample flowed at 250
6. 13, 100 A KOH 1/4, 000 20 1-0, 91 410 0, 94 205
7. 14, 100 A KOH 1/2, 000 20 1 7, 4 0, 73 360 0, 77 300
8th.

   1.29 X 106 A KOH 1/2, 000 20 2 6, 9 0, 91 390 0, 75 210
9. 15 X 106 A KOH 1/2, 000 20 0, 5 18 0, 13 160 0, 15 140 10. 15 X 106 A KOH 1/2, 000 20 3 5, 3 0, 67 270 0, 64 290 11. 13, 728 B KOCeHs 1/2. 000 20 0, 5 not vulcanizable, sample is soft and sticky 12. 13, 728 B KOC6H5 1/2, 000 20 4 not vulcanizable, sample is soft and sticky 13. 13, 728 B Potassium 1/2, 000 20 1 not vulcanizable, sample is soft and sticky hexylene glycol monoborate 14. 13, 100 C KOH 1/2, 000 20 2, 5 not vulcanizable, sample is liquid 15. 14, 100 D OK1 1/2, 000 21, 5 4 0, 40 410 0, 66 205 16.

   1, 5 X 10, -1 / 2, 000 20 1, 5 0, 61 195 0, 67 175 17.99, 200 A 1/2, 000 20-0, 50 390 0, 83 350 1) Potassium was im Monophenylsiloxane in amounts that gave the specified K / Si ratio.



     2) 4 parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane.



   Table II
Siloxane composition elastomer properties
24 hours at 250 C 72 hours at 250 C
Parts by weight parts by weight hours on tensile strength% tensile strength%
Dimethyl monophenyl return kg / Mn12 elongation kg / 1r1M2 elongation siloxane siloxane I. 100 40 2 0, 24 265 0, 17 140
2. 100 60 1 0, 54 330 0, 52 190
3. 100 80 3 0, 70 365 0, 74 245
4. 100 100 1 0, 72 360 0, 82 195
5. 100 120 2 0, 76 345 0, 93 195
6. 100 140 1 0.69 145 0.75 120
7. 100 140 3 0, 74 180 0, 97 185
8. 100 160 3 0. 64 110 0. 78 90
9. * 100 125 1 0.50 170 0.33 180
10. 100 140 2 0.74 170 0.90 160 11. * 100 75 1 0. 53 460 0.60 350
12. * 100 100 1 0.61 390 0.73 310 * 3 parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane.



   Table III
Monophenylsiloxane elastomer properties
24 hours at 250 C 72 hours at 250 C
Parts by weight parts by weight hours on tensile strength% tensile strength cAc initially added after reflux kg / mm2 elongation kg / mm2 elongation after boiling
1. 100 10 2 0, 73 320 0, 97 205 2. 100 20 2 0, 72 300 0, 99 225
3. 120-2 0, 76 345 0, 93 195
4. 100 40 2 0.63 215 0.95 165
5. 140-3 0, 74 180 0, 97 185
6. 10 90 2 0.45 180 0.25 115
7. 100 * 20 2 0, 46 270 0, 64 250 * 1 part of cyanoquanidines and 1 part of tert-butyl perbenzoate per 100 parts of dimethylsiloxane as vulcanizing agents.



   Table IV
Viscosity in cSt. * Elastomer properties g 24 hours at 250 C 72 hours at 250 C .. w concentrati @% solids @ solvents hours at the reflux before the after
Cooking tensile elongation
1. KOH 1K / 2000Si Benzene 20 1 - - 0.83 250 0.87 185
2. Potassium 1K / 3600Si Benzene 20 1 - - 0.73 210 0.70 180 hexylene glycol monoborate
3. KOH 1K / 2000Si toluene 20 1 5, 95 8, 47 0, 68 335 0, 84 270
4. KOCEHS 1K / 2000Si toluene 20 1 5, 95 7, 45 0, 61 320 0, 82 300
5. KOH lK / 2000Si xylene 20 1 6, 47 7, 73 0, 55 300 0, 63 195
6. Tetramethyl-0.2% by weight - 9, 57 0, 66 340 0, 73 300 guanidine-di-based on 2-ethylhexoate siloxane solids 7. NaOH 1 Na / 2000 Si toluene 20 4-7, 86 0, 73 300 0.71 175
8th.

   Tetramethyl-0.2% by weight toluene 20 4-11 0.70 335 0.33 300 guanidine-di-based on 2-ethylhexoate siloxane solids
9. LiOH lLi / 2000Si toluene 20 72--0, 70 219 0, 80 227 10.LiOH lLi / 2000Si toluene 20 288-0, 73 303 0, 77 207 11.

   LiOH lLi / 2000Si toluene 20 456-0, 76 308 0, 64 183 12. n-hexylamine 2% by weight bezo-toluene 20 96-0, 86 238 0, 64 141 gen on the weight of the siloxane solids 13. Tetramethyl-2 wt .-% bezo-toluene 20 5, 5-8, 32 0, 81 365 0, 82 325 guanidine-2-gene by weight ethyl hexoate of the siloxane solids viscosities at 20% solids in toluene.



   T a b e 11 e IV (continued)
Viscosity in cSt. * Elastomer properties
24 hours at 250 C 72 hours at 250 C
catalyst
Catalyst concentration
Solution% solids in solvent hours on reflux before after
Tensile strength elongation
14. as 13 as 13 toluene 20 11.5 - 8.7 0.77 338 0.79 305
15. Toluene 20 22-8, 18 0.83 360 0.86 355
16.> y 0.8% by weight bezo-toluene 20 1-7.7 0.65 345 0.71 380 based on the weight of the siloxane solids
17. Toluene 20 3-6, 9 0, 69 315 0, 81 340
18th

   Toluene 20 5, 5-5, 88 0, 74 390 0, 79 365 19. Toluene 20 11, 5-5, 12 0, 66 365 0, 74 410
20. 2% by weight based on toluene 20 0, 5-7, 43 0, 64 415 0, 64 245 based on the weight of the siloxane solids
3 parts by weight of tert-butyl perbenzoate per 100 parts of dimethylsiloxane.



   21. p-Toluene-0.75% by weight be-toluene 17 12-0.58 254 0.64 220 sulfonic acid added to siloxane solids 22. Tin (II) -0.0138% by weight toluene 20 23 --0.43 270 0.35 228 octoate based on siloxane solids * Viscosities at 20% solids in toluene.



  2 The catalyst was deactivated at the end of the reflux time by adding excess LiOH, which was then filtered before adding dry ice. The rubber was then applied as described in Example 1
Rolling treated.



  3 The catalyst was deactivated at the end of the reflux time by adding an equivalent amount of LiOH and then dried with Na2 SO4 before adding COo in the form of dry ice. The rubber was then treated on rollers as described in Example 1.



   Table V
Viscosity in cSt. * Elastomer properties
24 hours at 250 C 72 hours at 250 C speed - <- '<SS -SSMM visc. de
Dimeth @ oxans in% Fests in Folu @ hours on the reflux before the
Tensile strength Dehnur 1. 2250 20 0, 5-5, 4 0, 64 370 0, 77 180
2.250 40 1-80 0.83 360 0.85 170
3. 14, 100 10 3 5, 3 1, 9 0, 53 280 0, 76 250
4. 14, 100 30 2 5, 3 10, 5 0, 71 290 0, 79 190 5. 14, 100 50 3 5, 3 281 0, 72 210 0, 57 120
6.1, 29 # 106 10 2 28 3--0, 52 240
7. 15 # 106 25 2 425 11 0, 65 260 0, 67 210
8. 14, 100 33, 3 1 5, 3 43, 7 0, 79 320 0.82 200
9. 14, 100 25 1 5, 3 9, 8 0, 77 325 0, 85 210
10.

   14, 100 15 1 5, 3 3, 69 0, 63 380 0, 77 235 * The viscosities before boiling were measured at 20% solids content in toluene.



   The viscosities after boiling were measured at the solids content shown in the table.



   Table VI
Reaction conditions elastomeric properties
24 hours at 250 72 hours at 250 G o ": 'as"' µ'S.SP.S "jg'ss.c! .Sässss aBM tert. Cent.



   Draft kg / m%
Deh @
1.2-1.5 KOH 1K / 2000Si 0.41 140 0.98 205
2.4-1.5 KOH lK / 2000Si 0.55 140 0.84 180
3.4-1.5 KOH lK / 2000Si 0.59 290 0.77 240
4.2-1, 5 KOH 1K / 2000Si 0, 44 330 0, 71 310 5. 2 20 * 7 11, 52 Tetrame-2% wt .-% 0, 69 215 0, 77 205 thylgua-based on nidine- 2 wt. the ethyl siloxane hexoate solids *) Reinforcing SiO2 filler, made from sodium silicate in solution- <-SiOa-Sol in the presence of an ion exchange resin and mixing the sol with HCl. This gives silica with an average surface area of 250-500 m2 / g, the surface of which is saturated with trimethylsilyl groups linked to the SiOSi bonds.



   Table VII
Reaction conditions elastomer properties
24 hours at 250 72 hours at 250
Catalyst hour at the visc. in cSt tensile strength% tensile strength% conc. Reflux after boiling * kg / mm2 elongation kg / mm2 elongation 1K / 500Si 2 4, 8 0, 68 300 0, 85 250 IK / lOOOSi 3 4, 2 0, 67 285 0, 79 185 lK / 5000Si 3 4, 2 0, 65 345 0, 81 215 1K / 10000S1 3 4, 6 0, 62 365 0, 77 235 *) Viscosities at 20% solids in toluene.



   Table VIII
Test Test Tensile Tn,% Stress-Relaxation Energy-% Energy
No. No. (n) kglmm2 expansion energy (E) 2 E, -E "energy (R) 2 loss loss during the cycle
Cycle 100 (En-Rn) En-Rn En
E 1 0, 66 316 2, 57 0 0, 88 75, 88 67, 8
2 0, 66 330 1, 59 42, 68 0, 93 30, 85 41, 4
3 0, 66 349 1, 50 46, 91 0, 98 23, 99 34, 1
4 1 0, 48 123 0, 52 0 0, 35 7, 83 32, 0 Tab. II 2 0, 46 123 0, 41 5, 26 0, 34 2, 99 15, 7
3 0, 45 123 0, 38 6, 67 0, 31 3, 08 17, 3
10 1 0, 63 119 0, 61 0 0, 36 11, 5 40, 3 Tab.

   II 2 0, 58 119 0, 41 9, 12 0, 36 2, 39 12, 3
4 0, 57 119 0, 39 10, 06 0, 31 3, 73 20, 2
Table IX
Sample percentage G'in dyn / cm2 G "in dyn / cm2 contangent
Bend A (G '/ G ") 1st sample 11 0, 1 6, 13 X 106 0, 349 X 106 17, 6 Table 11 1 5, 88 X 106 0, 473 X 106 17, 1
5 5, 75 X 106 0, 348 X 106 16, 5
20 5, 45 X 106 0, 408 X 106 13, 4 2nd sample 12 0, 1 8, 51 X 106 0, 561 X 106 14, 9
Table II 1, 0 8, 37. X 106 0, 517 # 106 16, 2
5, 0 8, 09 X 106 0, 492 X 106 16, 4
20, 0 7, 88 X 106 0, 575 X 106 13, 7 3.

   Sample 9 0, 1 11, 7 X 106 0, 827 X 106 14, 1
Table II 1, 0 11, 5 X 106 0, 812 X 106 14, 2
5, 0 11, 3 X 106 0, 794 X 10 "14, 3 20, 0 10, 8 X 106 0, 879 X 106 12, 3 4. K 0, 1 37, 1 X 10" 3, 19 19 X 106 11, 6 1 21, 2 X 10 5, 67 X 106 3, 75
5 9, 8 X 106 6, 24 X 106 1,
20 5, 41 X 106 2, 16 X 106 2, 5
Table X
Elastomer properties
Vulcanization under pressure for 24 hours at 250 C 72 hours at 250 C
Part by weight Part by weight Time Temp.

   Tensile strength% tensile strength%
Vulcanizing agent additive (min.) (C) kg / mm2 elongation kg / mm2 elongation 2 parts tert-butyl-3-G 10 150 0, 66 200 0, 82 130 perbenzoate 2 parts tert-butyl 3-H 10 150 0, 51 160 0, 71 140 perbenzoate 2 parts benzoyl peroxide 10 150 0, 35 180 0, 83 190 3 parts benzoyl peroxide 5 125 0, 65 200 0, 72 150 2 parts tert-butyl - 5 125 0, 59 200 0, 72 160 perbenzoate and 2 parts.



      Benzoyl peroxide 2 parts tert-butyl-1-G 10 150 0, 59 130 0, 70 160 perbenzoate 2 parts tert-butyl-3-G and 10 150 0, 59 100 0, 72 150 perbenzoate 1-I
Table XI
Reaction conditions Elastomer properties me 24 hours at 250 C 72 hours at 250 C e.c cru z
Hours on reflux and H2O-Reter
Hours on reflux with azeotropic
Visc. in cSt according to the Kocl tensile strength
strain
Tensile strength elongation
1. 4 0 4.1 0.71 290 0.7 205
2. 20, 5 0 4, 2 0, 71 410 0, 78 230
3. 20, 5 0, 5 4, 5 0, 80 345 0, 82 205
4. 20, 5 2 4, 7 0, 76 370 0, 81 245
Table XIV
Elastomer properties 24 hours at 250 C 72 hours at 250 C bu s * s cu N
Cl
M "" SM'S'SMMMM visc. of the D siloxane in
Monoorga @
Catalyst
Catalyst
Tensile strength
Tensile strength 1.

   13.00 Copolymer of 0.5 mol% KOH 1K / 2000Si 0.86 330 0.65 151 (CH2 = CH) SiO1.5 and 99.5 mol% (C6Hs) SiOl, 5 2. 13, 000 copolymer of 1 mol% KOH 1K / 2000Si 0, 95 345 0, 82 160 (CH2 = CH) SiO1.5 and 99 mol% (C6H5) SiO1, 5 3.13, 000 copolymer of 5 mol. % KOH 1K / 2000Si 0.96 195 0.75 110 (CH2 = CH) SiOl, 5 and 95 mol% (C6H5) SiO1.5 4. 13, 000 Copolymer of 1 mol% tetramethyl-0.2 Weight-X7O, be-0, 70 355 0.54 208 (CH2 = CH) SiO ,, 5 and 99 mol% guanidine-2-added to the (C6H5) SiOi. 5 ethyl hexoate by weight of siloxane solids 5.

   14, 100 mixture of 1 mol% Mono-KOH lK / 2000Si 0, 84 328 0, 82 200 tolylsiloxane and 99 mol%
Monophenylsiloxane 6.14, 100 Copolymer of 10 mol% mono-KOH lK / 2000Si 0.86 277 0.44 90 tolylsiloxane and 90 mol%
Monophenylsiloxane 7.14, 100 Copolymer of 1 mol% Mono-KOH lK / 2000Si 0.76 279 0, 50 121 tolylsiloxane and 99 mol%
Monophenylsiloxane 8,13,000 Copolymer of approx. 13 mol% KOH 1K / 2000Si 0.70 410 0.83 240
Monomethylsiloxane and approx. 87 mol% monophenylsiloxane


    

Claims (1)

PATENT CLAIM Process for producing a silicone rubber, characterized in that (A) is mixed in an inert solvent to form a rubber thermosetting with peroxide (1) 100 parts by weight of organosiloxane polymer with an average of at least 200 silicon atoms per molecule, which essentially consists of units of the formula RnSi04¯n, in which R is a methyl, phenyl or vinyl radical and n is the number 0, 1, 2 or 3, where n has an average value of 1.98 to 2.05, and in the average of at least 0.75 silicon-bonded methyl groups and an average of at most 0.15 silicon-bonded vinyl groups per silicon atom and no more than 50 mol% of the units mentioned are (C5H5) 2SiO units, and which further contains an average of at least 2 silicon-bonded hydroxyl groups per molecule, (2) 40 to 175 parts by weight of (a) siloxane, the siloxane units of which have the formula (C6H5) xR'ySiO4-xy, in the cash, the phenyl radical , R'ein 2 monovalent hydrocarbon radical different from the phenyl radical, x is the number 0, 1 or 2, y is the number 0, 1 or 2, and the sum of x and y is 0, 1, 2 or 3, on average per molecule at least 2 silicon-bonded groups of the formula MO-, in which M represents hydrogen, an alkali metal or a quaternary ammonium group, where x on average has a value from 0.65 to 1, 3, y on average has a value of less than 0, 4 and the sum x + y has an average value of 0.95 to 1.3, and where at least 60 mol% of the siloxane units (C6H5) are SiO1.5 units, or (b) silanol of the formula (C6Hs ) aR'bSi (OH) ab, in the CfiHe, the phenyl radical, R'ein a monovalent hydrocarbon radical different from the phenyl radical, a is the number 0, 1 or 2, b is the number 0, 1 or 2 and the sum of a and b at least 1, which contains on average 0.65 to 1.3 phenyl groups per silicon atom, and in which the average value of b is less than 0.4 and the average value of the sum of a and b is between 1.0 and 1.3, where at least 60 mol% of the silanol have the formula (C6H5) Si (OH) 3, and (3) a catalytic amount of a condensation catalyst for silicon-bonded hydroxyl groups, the concentration of the starting materials in the solvent being such that no noticeable Gelation takes place during heating, and a reaction product is formed in which components 1) and 2) are bonded to one another through the formation of a Si-O-Si bond, and (B) the solvent from the in step (A ) The reaction product obtained is removed, the product being processed sufficiently during this working stage so that it remains essentially homogeneous. SUBCLAIMS 1. The method according to claim, characterized in that the siloxane units of the siloxane polymer (1) are those of the formula (CH3) nSiO4-n and the component (2) is a siloxane polymer (a) whose siloxane units of the formula (C6H (CH2 = CH) ySiO., - xy ent- 2 speak, and which has at least 2 silicon-bonded hydroxyl groups per molecule. 2. The method according to claim, characterized in that in the siloxane polymer (2) (a) x has an average value of 0.9 to 1.2 and y has an average value of less than 0.15, the average value of the sum x + y between 0 , 95 and 1, 2 and at least 80 mol% of the siloxane units of the formula (C6Hs) SiOl, 5 correspond. 3. The method according to claim, characterized in that the heating is carried out by refluxing the reaction mixture in an aromatic solvent and removing a substantial portion of the by-products formed during boiling, the refluxing being carried out until a thermosetting rubber is formed is. 4. The method according to dependent claim 3, characterized in that an alkali metal hydroxide is used as a condensation catalyst, and the starting material concentration in the solvent is such that no noticeable gelation takes place during refluxing, the alkali metal hydroxide is deactivated before removing the solvent Solvent is then removed from the reaction product by treating the product on hot rollers, the duration and temperature of this treatment being selected so that substantially all of the solvent present in the reaction product is removed, and the treatment conditions are further such that the reaction product during the Removal of the solvent remains essentially homogeneous. 5. The method according to dependent claim 4, characterized in that the aromatic solvent used is toluene. 6. The method according to the dependent claim, characterized in that x has a mean value of 0.98 to 1.05 and y is equal to 0. 7. The method according to claim or one of the dependent claims 2-6, characterized in that the condensation catalyst used is potassium hydroxide. 8. The method according to dependent claim 7, characterized in that the potassium hydroxide is present in such amounts that one potassium atom per 100 to 100,000 silicon atoms is present. 9. The method according to dependent claim 8, characterized in that the potassium hydroxide is deactivated with carbon dioxide. 10. The method according to dependent claim 9, characterized in that there is one potassium atom for every 500 to 10,000 silicon atoms and the starting material concentration in the toluene is between 15 and 40% by weight.