DE1176853B - Process for the production of elastomers from organopolysiloxanes - Google Patents

Description

Process for the production of elastomers from organopolysiloxanes Organopolysiloxane elastomers are known and because of their heat resistance, their chemical inertness and their flexibility at low temperatures versatile usable. They are usually made from an organopolysiloxane found in the solid, hardened, elastic state can be converted from a filler and a metal catalyst. These organopolysiloxanes are common Substances that contain an average of about two organic residues per silicon atom, wherein the organic radicals through carbon-silicon bonds to the silicon atom are chained. Usually the organic radicals are monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals. Contain the usual polysiloxanes organic residues, which consist predominantly of methyl residues, in some cases a smaller proportion of phenyl radicals, vinyl radicals, chlorophenyl radicals or cyanoalkyl radicals contain.

The usual curing catalysts for the known organopolysiloxanes are organic peroxides. The organic peroxides give a very satisfactory one Curing of the organopolysiloxanes, however, also cause some disadvantages. When hardening For example, various organic acids are formed as reaction products. the Presence of these organic acids is common for the properties of the organopolysiloxanes disadvantageous, especially when the organopolysiloxanes at elevated temperatures be used in a damp or closed environment. The acidic reaction products increase the rate of hydrolytic decomposition of the cured organopolysiloxane. In addition, organic peroxides are not sufficient hardeners when finely divided Carbon is added as a filler.

The invention is now based on the object of creating a method in which these disadvantages do not occur and which are also used for masses where carbon is used as a filler.

The invention relates to a process for the production of elastomers of organopolysiloxanes with a viscosity of at least 100,000 cSt, fillers and metal salt catalysts under shaping, which is characterized in that as organopolysiloxanes those of the general formula (HOOCC7n-I2m) a (R) bSiO-a-b (1) 2 can be used, where a has a value between 0.001 and 0.1, m den Has a value of 2 or 3, the sum a + b has a value between 1.999 and 2.001 and R is a monovalent hydrocarbon radical, monovalent halogenated hydrocarbon radical or cyanoalkyl radical.

The radicals indicated by R in the formula (1) include, for. B. Alkyl radicals, such as methyl, ethyl, propyl, butyl or octyl radicals, aryl radicals, e.g. B.

Phenyl, diphenyl, naphthyl, toluyl or xylyl radicals, aralkyl radicals, z. B. benzyl, phenylethyl or styryl radicals, cycloalkyl radicals, for. B. cyclohexyl or Cycloheptyl radicals, alkenyl radicals, e.g. B. vinyl or allyl radicals, cycloalkenyl radicals, z. B. cyclohexenyl or cycloheptenyl radicals, halogenated aryl radicals, e.g. B. chlorophenyl, Dibromophenyl or tetrachlorophenyl radicals, halogenated alkyl radicals, e.g. B. chloromethyl, Bromomethyl or β-chloroethyl radicals, alkynyl radicals, e.g. B. the ethynyl radical or cyanoalkyl radicals, z. B. ß-cyanoethyl, ß-cyanopropyl or γ-cyanopropyl radicals.

Since the carboxyalkylorganopolysiloxane of the formula (1) is an average contains about two organic radicals per silicon atom, it is obvious that the Organopolysiloxane predominantly diorganosiloxane units of the formula: (R) 2SiO (2) comprises and difunctional Carboxyalkyl groups of the formula: (HOOCCmH27n) (R) SiO (3) in which R and m are the same Have meaning as above.

In addition to these two predominant components, the carboxyalkylpolysiloxanes can be used also smaller amounts of monoorganopolysiloxane units of the formula RSiOl. 5 (4) and contain triorganosiloxane units of the formula RsSiO (5). Although the carboxyalkyl groups usually into the carboxyalkylorganopolysiloxane in the form of units of the formula (3) are introduced, some may in certain embodiments of the invention or all of these carboxylalkyl groups as siloxane units of the formula (HOOCCmH2 SiO (6) (HOOCCH) (R), SiO,., (7) may be introduced. Are mono- or trifunctional Siloxane units of the formulas (4) to (7) in the carboxyalkylorganopolysiloxane of the formula (l), then the number of these units must be restricted so that the Total number of silicon-bonded organic residues between 1.999 and 2.001 organic Radicals per silicon atom.

As already mentioned, the carboxyalkylpolysiloxanes of the formula (1) be formed by well-known methods. A very suitable one The method for forming these substances is the hydrolysis of a cyanoalkylorganodichlorosilane with the formula (NCCnH2m) (R) SiCl, (8) in which m and R have the same meaning as have up.

This method corresponds to U.S. Patent 2900363.

The finely divided silica fillers used in accordance with the invention are used are known and are the usual fillers for organopolysiloxanes.

Usually these silica fillers greatly comprise fine particles providing a large surface area per unit weight, e.g. Legs Surface from 50 to 500 m2 or more per gram. These fabrics are sold as sublimed silica, precipitated silica or silica airgel, or the like. Available.

These fillers can be untreated or with methylpolysiloxanes treated as disclosed in U.S. Patent 2,938,009.

The carbon used as a filler in the mass according to the invention can be incorporated is any commercially available, finely divided carbon, e.g. B.

Lamp soot.

Those used for the elastomers made in accordance with the invention Amounts of carbon or silica fillers can vary depending on the desired properties of the end product can be varied within wide limits. Usually the elastomers contain between 20 and 300 parts of finely divided filler to 100 parts of the carboxyalkylorganopolysiloxane of the formula (1).

The polyvalent metal compounds that act as curing catalysts can be used for the elastomers produced according to the invention are numerous and varied. Usually these are polyvalent metal compounds Metal oxides or metallic compounds consisting of a metal ion and a volatile one Anion exist. Preferred groups of polyvalent metallic compounds, the that can be used as effective catalysts are: oxides, hydroxides, Carbonates, salts of carboxylic acids with I to 1 I carbon atoms, alcoholates of the Alcohols with I to I I carbon atoms or salts of the enols with I to I I carbon atoms.

The range of polyvalent metals that are part of the metallic Forming compound which is used for the process of the invention is extraordinary great. No metals have been proven that are useless for the invention, as long as they are polyvalent metals, d. H.

Metals with a valence of at least 2. Among the metallic Compounds that are particularly useful in the method of the invention include the metals of groups Ib, Ha, IIb, IIIa, IVa, IVb, Va, VlIb or VIII of the periodic System of elements. Among the metals of the specified groups, for the The method according to the invention preferably uses those listed below : Magnesium, calcium, strontium, barium, titanium, zircon, manganese, iron, cobalt, nickel, Copper, zinc, cadmium, aluminum, tin, lead or antimony.

Characteristic polyvalent metal compounds that act as a curing catalyst can be added are: magnesium, calcium octoate, calcium propionate, strontium carbonate, Barium decanate, zinc naphthenate, tetrabutyl titanate, zirconium acetate, zirconium octoate, manganese dioxide, the iron salt of the enol of acetylacetone, cobalt oxide, nickel hydroxide, cupricarbonate, Zinc oxide, zinc octoate, zinc isopropylate, zinc acetate, cadmium butyrate, the aluminum salt of the enol of acetylacetone, stannous octoate, stannous octoate, aluminum butyrate, lead oxide, Antimony acetate or the like.

The amount of the polyvalent metal compound used can be wide Limits can be varied.

Usually, when 0.1 to 10 is added, sufficient hardening will be achieved Parts by weight, preferably from 0.3 to 5 parts by weight, of the polyvalent metal compound achieved on 100 parts of the carboxyalkylorganopolysiloxane of formula (1). The application of more than 10 parts by weight of the polyvalent metal compound to 100 parts of the Carboxyalkylorganopolysiloxane did not provide improved cure of the silicone elastomer.

The polyvalent metal compounds used according to the invention as curing catalysts are commercially available in various forms. Most Metal compounds are available in solid form and are the preferred embodiment of the invention uses the curing catalyst also in this one Shape. In other cases, however, these octoates are available as a solution or dispersion, in a suitable solvent or dispersant, e.g. B. turpentine oil substitute, solved, available. In the method according to the invention, these solutions or Dispersions applied satisfactorily without the polyvalent metal compound is separated.

The compositions to be cured according to the invention, which consist of the carboxyalkylorganopolysiloxane of formula (1), the carbon or silicon dioxide filler and the polyvalent Metal compound as a curing catalyst are made by simply mixing formed of these three components. Any conventional method can be used will. It can be done in a standard rubber mill or in a Banbury mixer Mix. Each of these methods gives a satisfactory result, without distinction, whether the polyvalent metal as a curing catalyst in solid form or in the form of a Solution or dispersion is added. It is crucial that the mix of the three ingredients is mixed so thoroughly that it is homogeneous.

The mass to be hardened according to the invention from the three components can be cured in the same way as the usual curable organopolysiloxane compositions. The masses can therefore be pre-hardened or shaped in a heated press which supplies a temperature of 150 ° C for 5 minutes, for example, and are subsequently post-cured at a temperature between approx. 150 and 250 ° C, the time can be varied between about 16 and 72 hours. Although the Masses can be hardened with the aid of the heat treatments described It is an unusual and unexpected feature of the invention that the masses Cure at room temperature if you take them for a period between about 48 hours leaves at room temperature for up to a week. The hardening time depends on the respective composition, the catalyst level and the ratio of Carboxyalkyl groups to the silicon atoms in the carboxyalkylorganopolysiloxane of the formula (1).

The following exemplary embodiments are intended to illustrate the invention in greater detail explain, but are not to be regarded as a limitation. All information relate on weight units.

Example I a) Preparation of the polysiloxane to be used This Embodiment describes the preparation of a methyl-p-carboxyäthylpolysiloxans in the context of formula (1) with a viscosity of about 500000cSt at 25 ° C, in which a has a value of 0.001 and the sum of a and b is 2.00. 100 parts Methyl-ß-cyanoethyldichlorosilane were concentrated to about 225 parts with stirring, given aqueous HCl containing approximately 35 weight percent HCl. This addition was added within 10 minutes, the mixture boiled for several hours and get a clear solution. 200 parts of water were added and the resulting, separated liquid precipitated. It was made by repeatedly dissolving it in 200 parts Purified boiling water and precipitated from the cooled solution.

The methyl-p-carboxyäthylpolysiloxan was 8 hours in a Oven dried at 120 ° C and gave a low molecular weight liquid, which consisted predominantly of methyl-jS-carboxyethylsiloxane units. This methyl, B-carboxyäthylpolysiloxan was sufficient with octamethylcyclotetrasiloxane Amount mixed so that 0.1 mol of methyl-ß-carboxyethylsiloxane units to 99.9 mol Dimethylsiloxane units came. For 100 parts of the mixture, 10 parts were 87% Added sulfuric acid and the mixture was stirred for 20 hours.

After this time, the resulting product was cut into 500 pieces Benzene dissolved and washed repeatedly with water to remove all traces of sulfuric acid were removed and the acid-free product dried over calcium sulfate. That dried product was stripped off under vacuum so that the benzene was removed, and gave a methyl-ß-carboxyethylpolysiloxane with methyl-ß-carboxyethylsiloxane units and dimethylsiloxane units in the ratio of 0.1 mole percent to 99.9 mole percent. This compound had a viscosity of about 500,000 cSt at 25 ° C. b) According to the invention Use 100 parts of the polysiloxane from Example 1, the 0.1% methyl-jS-carboxyethylsiloxane units Was containing 40 parts of precipitated silica and 1, 0 or 5.0 parts Stannous octoate (as a 28% solution of stannous octoate in turpentine oil substitute) in mixed in a rubber mill. A number of films made from these blends have been made then molded in a press for 5 minutes at 125 ° C, and these sheets were at post-cured at different temperatures for different times; Hardness, tensile strength and elongation were measured. Table I gives the parts of tin octoate per 100 parts of the polysiloxane after curing is complete, the hardness of the finished films in » Shore A «, the tensile strength in kg / cm2 and the elongation in" /.

Table I. Stannous octoate hardening degree of hardness tensile strength elongation in pieces 28 ° io tin ° C / hour o Shore A «kg / cm $ ° lo 1.0 150/16 24 8, 4 260 1.0 250/16 34 57, 4 550 1.0 250/72 41 55, 6 430 5.0 150/16 30-170 5.0 250/16 52 43, 4 260 5.0 250/72 65 58, 1 180 EXAMPLE 2 According to the method of Example 1, a polysiloxane with a viscosity of about 2,000,000 cSt at 25 ° C. was formed which consisted predominantly of 0.2% methylβ-carboxyethylsiloxane units and 99.8 mole percent dimethylsiloxane units. To 100 parts of this polysiloxane, 40 parts of sublimed silicon dioxide and various amounts of stannous octoate were added as a 28% solution in turpentine oil substitute or zinc oxide. Films made from these masses were molded in a press at 125 ° C. within 10 minutes, which were then cured in the oven for different lengths of time. The physical properties were determined. Table II lists the parts of the metal compound for every 100 parts of rubber, the cure, the degree of hardness, the tensile strength and the elongation.

Table II Parts of the hardening degree of hardness' .. elongation Metal connection ° C hrs. NShore Au k cm = " 0, 7 stanno- octoate (28 0 /, tin) 150/16 35 40. 6 410 250/16 41 57.4 480 250/72 45 44.8 480 1, 7 stanno- octoate (28 ° / o tin) 150/16 34 22, 4 350 250/16 40 53.9 460 250/72 40 51.8 440 0.32 ZnO ..... 150/16 25-150 250/16 40 26, 6 300 250/72 44 45.5 370 1, 0 ZnO ...... 150/16 22-120 250/16 37 31, 5 380 250/72 39 46.9 390 Example 3 Another amount of the polysiloxane from Example 2 was mixed with sublimed silicon dioxide and various additions of various metal compounds as a catalyst. In each case, 100 parts of polysiloxane and 40 parts of sublimed silica were used as fillers. After the addition of the curing catalyst and the formation of films by the method described, each film was cured for 16 hours at 150 ° C. and 16 hours at 250 ° C. and the physical properties were determined. Table III gives the parts of the curing catalyst per 100 parts of polysiloxane, the degree of hardness, the tensile strength and the elongation of the cured films.

Table III Curing catalyst Degree of hardness Tensile strength Elongation z "Shore A" I kg / cmz oJo 0.6 tetrabutyl titanate 49 42.7 400 0.25 stannous octoate (28 ° / o tin) 43 42.7 390 0.6 aluminum tert. butylate ......... 46 44.8 360 I, 0 zirconium acetate ... 50 40, 6 350 EXAMPLE 4 A polysiloxane having a viscosity of about 100,000 cSt at 25 ° C. containing 0.3 mole percent methyl-3-carboxyethylsiloxane units and 99.7 mole percent dimethylsiloxane units was prepared by following the procedure of Example 1. This polysiloxane was mixed with precipitated silicon dioxide and various metal compounds, 40 parts of silicon dioxide being added to 100 parts of polysiloxane and various amounts of the metal compounds. These blends were formed into films and cured according to the procedure of Example 3. Table IV below gives the parts of the metal compound as curing catalyst per 100 parts of polysiloxane, the degree of hardness, the tensile strength and the elongation of the cured films formed.

Table IV Curing catalyst Degree of hardness Tensile strength Elongation tShoreA «kg'cm" 3.3 stannous octoate (28 ° / o) 55 42.7 200 ], 0 calcium propionate ...... 44 40, 6 370 1, 0 zinc propionate .. 40 37, 8 270 1, 0 aluminum acetylacetonate .. 55 51, 1,290 EXAMPLE 5 A methyl-β-carboxyethylpolysiloxane was prepared by following the procedure of Example 1, which had a viscosity of about 100,000 cSt at 25 ° C. and contained 0.6 mol percent methyl-β-carboxyethylsiloxane units and 99.4 mol percent dimethylsiloxane units. Following the procedure of Example 3, a number of films were made consisting of 100 parts of polysiloxane, 40 parts of precipitated silica, and varying amounts of various metallic curing catalysts. After the films were formed from the compositions and cured according to the procedure of Example 3, the physical properties were determined. The parts of the metal compound as curing catalyst per 100 parts of polysiloxane, as well as the physical properties, are listed in Table V below.

Table V Curing catalyst Degree of hardness Tensile strength Elongation tShoreA «kg / cm '° / 0.7 stannous octoate (28 ° / o tin) 46 47.6 290 1.7 stannous octoate (28 ° / a tin) .... 54 46.9 260 ], 8 stannous octoate (28 ° / o tin) 43 53.9 280 0.3 ZnO ........... 51 41. 3 240 1.0 49 42, 0 240 2.2 stannous octoate (22 ° / o tin) .... 52 60.9 250 2.7 zircon octoate (5 ° / 0 zircon) ... 70 27.3 120 EXAMPLE 6 A methyl-ß-carboxyethylpolysiloxane was prepared by following the procedure of Example 1, which had a viscosity of about 1,000,000 cSt at 25 ° C. and contained 1.8 mole percent methyl-ß-carboxyethylsiloxane units and 98.2 mole percent dimethylsiloxane units. Following the procedure of Example 3, films were formed from 100 parts of the polysiloxane, 40 parts of silica airgel and varying amounts of the various metal compounds as the curing catalyst. Table VI gives the parts of the metal compound per 100 parts of polysiloxane and the physical properties of the cured films.

Table VI Curing catalyst Degree of hardness Tensile strength Elongation Shore A «kg / cm» ° /. 1, 0 zinc acetate ...... 65 28 70 0.5 64 24, 5 70 EXAMPLE 7 A methyl-ß-carboxyethylpolysiloxane having a viscosity of about 1,000,000 cSt at 25 ° C. containing 3 mole percent methyl-ß-carboxyethylsiloxane units and 97 mole percent dimethylsiloxane units was prepared by the method of Example. According to the procedure of Example 3, films were formed from a composition consisting of 100 parts of this polysiloxane, 40 parts of finely divided carbon black and 4 parts of zinc oxide. The cured films had physical properties comparable to those of the Example 6 films.

The exemplary embodiments cited are, of course, based on one limited number of possible modifications within the scope of the invention. It is evident that in addition to the particularly mentioned metal compounds of the examples many others from the group described are also used as curing catalysts for the organopolysiloxanes of the exemplary embodiments, as for other organopolysiloxanes, given in the above description can be used. In addition, the proportions of the compositions to be cured according to the invention can be within wide limits can be varied, as already mentioned.

The organopolysiloxane elastomers of the invention are also versatile can be used like the usual organopolysiloxane elastomers. You can for application at elevated temperatures, for example as sealing sleeves, in the desired Mold have been cured. aside from that can use them over or around electrical conductors are extruded and cured at room or elevated temperatures so that insulated electrical conductors are formed. In addition permitted their unique property, d. H. the possibility of curing at room temperature, their use as coatings for electrical components that provide insulation that can withstand high operating temperatures but not require initial cure tolerates temperatures as required for the curing of the customary organopolysiloxanes.

For example, a miniature transformer with polyester insulation of the windings according to Example 2 and for about 96 hours at room temperature be left standing. After this time has elapsed, the coating is completely hardened and has excellent physical properties.

Claims (1)

Claim: Process for the production of elastomers from organopolysiloxanes having a viscosity of at least 100,000 cSt, fillers and metal salt catalysts under shaping, d a d u r c h marked that such as organopolysiloxanes of the general formula (HOOCCmH2 a) a (R) bSiO4-a-b can be used, where a is a Has a value between 0.001 and 0.1, m has the value 2 or 3, the sum a + b has a value between 1.999 and 2.001 and R is a monovalent hydrocarbon radical, is a monovalent halogenated hydrocarbon radical or cyanoalkyl radical. Documents considered: German Auslegeschrift No. 1,019,462; India Rubber World, September 1953, pp. 766-770.