Untitled record

Process for the polymerization of essentially diorgano-substituted siloxanes High molecular weight liquid or gel siloxanes, especially dimethylpolysiloxanes, which are starting materials for the production of silicone rubber, are obtained either by polycondensation of low molecular weight hydroxyl-containing dimethylsilicone oils with so-called condensation catalysts or by polymerization of cyclic dimethylsiloxanes with rearrangement catalysts. The rearrangement catalysts cleave the S: i-O'-Si bond and cause rearrangement to linear, high molecular weight siloxanes. The experimental observations suggest that a sufficiently high degree of polymerization can not be achieved by pure condensation reactions, ie alone with condensation catalysts, so that a good catalyst must catalyze the rearrangement at the same time. At higher temperatures, however, rearrangement catalysts often have a depolymerizing effect. Therefore, they usually have to be completely removed from the polymer after the polymerization, so that the heat resistance of the products obtained does not suffer. The experimental results further show that the nature of the polymerisation catalyst and its mode of application have a great influence on the properties of the silicone rubber obtained from the polymer. For unsuitable catalysts, e.g. As a result of wetting difficulties, the incorporation of the fillers in the polymer to be severely difficult. or too much "cold flow" can occur during molding of the products. From the literature, although a large number of substances is already known, the low molecular weight, essentially. Diorganosubstituierte Si.loxane in high molecular, .for further processing on S.ilikonkau.tschuk suitable siloxanes, in particular, in Siloxangele transfer. However, all catalysts used to date for this purpose have a number of disadvantages. Sulfuric acid or chlorosulfonic acids are sparingly soluble in low molecular weight siloxanes and, as a result of their too rapid action, tend to lead to uneven polymers. Although a number of catalysts, such as boric acid and its esters, boron fluoride, silylborate, phosphorus pentoxide, phosphoric acid, phosphorus trichloride, phosphorus pentachloride, have good polymerizing properties, the mixtures prepared from the polymers show too much cold flow when vulcanized under pressure. Compounds such as sulfuryl chloride and antimony pentachloride provide non-uniform polymers that have strong discoloration. Ferric chloride, which represents a very good catalyst., Has the disadvantage that it has to be carefully washed out after polymerization from the polymer. Alkalihydroxy.de, alkali metal salts of silanols or. Siloxanes and alkali metal alcoholates only contribute. very careful application to success, since alkalis easily cause cleavage of the Si-C bond and thus undesirable crosslinking. In many cases, the alkali-polymerized siloxanes also poorly wet the fillers. Good catalysts are phenoxyphosphoric acid dibenzloride and phenylphosphoric acid dichloride. Disadvantageous, however, is their decomposability at high temperature and in the action of water and their readily depolymerizing action. It has now been found that low molecular weight, substantially diorgano-substituted sidoxanes can be easily or mass-produced in a high molecular weight by means of a novel group of catalysts can convert gelatinous siloxanes, the most of which no longer have the disadvantages caused by the catalysts used so far and are therefore very suitable for the production of silicone rubber.

According to the invention, the polymers to be polymerized are treated with phosphorus nitrogen compounds which represent either phosphonitrile halides or derivatives of phosphorous acid or phosphoric acid substituted by organic radicals on the nitrogen, which may optionally be halogen-substituted.

Particularly suitable phosphonitrile halides are, in particular, the phosphonitrilic chlorides and, in this group, in particular the polymeric phosphonium nitrite chlorides (PN Clz), where in the formulas an integer and suitably at least 3 mean. The best suitable catalyst is a mixture of phosphonitrile chlorides of various degrees of polymerization, in which compounds in which n is 3 to 6; are included.

For example, the organic phosphorus-nitrogen compounds derived from the phosphoric or phosphorous acid may have the following constructions: In these formulas, R, R ', R "represent alkyl, aryl, aralkyl, or H, while X is halogen ,

Suitable organic phosphorus-nitrogen compounds are, for. B.

Phosphorous acid dichloride-anilide, phosphorothioic acid dichloride-methylanilide; Phosphorous acid dichloro; d-ethylanilide, phosphorous acid d-dichloride diphenylamide, P. phosphorous acid dichloride methylamide, phosphorothioic dichloride isopropylamide, phosphorous acid dichloride benzylamide, P: phosphorous acetic acid anilide. anil, phosphoric acid methylamide anilide, phosphoric acid dichloride anilide, phosphoric acid dicluric a-naphthylamide, phosphoric acid dichloride methylamide, phosphoric acid dfchloride isopropylamide, phosphoric acid dichloride ethylamide, phosphoric acid e-anilide anil, Phosphoric acid-a-1) aphthylamid-anil,. Phosphoric acid methylamide anil and phosphoric acid isopropylamide anil. The phosphorus-nitrogen compounds act on .all. Types of siloxanes, including resinous, polymerizing .. With particular advantage, however, they are used in such siloxanes, the.-hochgeben in the polymerization hochmolekulare linear, liquid or gelartige.-, as they usually serve for the production of silicone rubber. Such siloxanes are especially the diorganosiloxanes. However, the siloxanes to be polymerized may also contain small amounts of siloxanes of the type RS: i O1.5 and R3 Si 00.5, where R may be any organic radicals. In general, the siloxanes to be polymerized expediently have a substitution ratio which is between 1.9 and 2.1 organic radicals per silicon atom.

The organic, carbon-bonded to silicon radicals of the S-iloxane to be polymerized, any alkyl radicals, eg. As methyl ethyl, propyl, butyl or octadecyl, any aryl radicals, especially monocyclic, such as phenyl, tolyl, xylyl or aralkyl or alkaryl radicals, halogenated phenyl radicals or Trimethylsilmethy lenre.ste be. The siloxanes may also have two different radicals: on the Si atom. Suitable siloxanes are for. B. Dimethylsiloxane, ethylmethylsiloxane, dibutylsiloxane, methyloctadecylsiloxane, methylphenvlsiloxane, niethylchlorophenylsiloxane, diphenylsiloxane, tolylmetbylsiloxane, benzylmethylsiloxane, trimethylsilm.ethylene methylsiloxane, phenyltrimethylsilmethylsiloxane, and the like. like.

The siloxanes to be polymerized may be homopolymer copolymers of two or more siloxane incorporates. The low molecular weight .Ausgangsstoffe may have cyclic or linear structure. They can also be a mixture of siloxanes of different constitution and structure type. In such cases, in the polymerization, copolymers are obtained which contain the structural units of the starting siloxanes. Of course, already largely condensed or polymerized siloxanes can be converted into the corresponding high molecular weight products.

The new polymerization catalysts have both condensing and redistributing effects. They may be used in an amount of from 0.1 to 1% by weight calculated on the silver value. Generally, they are preferably used in an amount of 0.1 to 1% by weight. They may be added either dissolved in an organic solvent or undiluted state to the siloxane to be polymerized. The polymerization is usually carried out after addition at room temperature and even at temperatures below. To accelerate the polymerization, however, it is often convenient to operate at elevated temperature to about 15 °.

The use of the new catalysts achieves a number of advantages: i. The catalysts have a very good dispersibility in low molecular weight Si loxanes, therefore, there is a uniform, good and easy to control polymerization; 2. the polymerization is already quite fast at room temperature; 3. the catalysts do not cleave Si-C bonds even at higher temperatures, ie no unwanted crosslinking takes place; 4th the catalysts do not need to be removed from the system after polymerization because they have no depolymerizing effect; probably they are inactivated during the vulcanization of the siloxane to siloxane rubber; 5. the polymers obtained according to the invention show no cold flow when pressed into silicone rubber, in addition they have a good absorption and wetting capacity for fillers; 6th the products are more heat-resistant, as the phosphorus-nitrogen compounds act as antioxidants at the same time. EXAMPLE 1 To 100 g of a dimethylsiloxane oil of 50 ° C., obtained by hydrolysis of a highly purified dimetbyldichlorosilane in known manner, are added with vigorous stirring o, ig (PN C12) 4, dissolved in 5 cc of trichlorethylene, and the mixture is heated up 12o 'until the mass has reached a toughness that makes further stirring impossible. After cooling, a soft, rubbery polymer is obtained. This polymer results in further processing a S'iloxankäutschuk with good mechanical properties, as can be seen from the following experiment: 100 g of the polymer are kneaded in a mixer with 150 g of titanium dioxide and 2.5 g of benzoyl peroxide. The mass obtained is rolled to a coat on a rolling mill, vulcanized in a Vulkani.sationspresse io minutes at 125 'and then baked io hours at 15o ° and io hours at 20o °. This gives a siloxane gum having a tensile strength of about 30 kg / cm 2 at an elongation at break of 100% and a Shore hardness of 55.

EXAMPLE 2 A solution of 0.5 g of Ca H5-NH-P =N-C6H5 in 5 cc of toluene is added to 100 g of a liquid, customarily prepared and largely condensed dimethylsiloxane having a viscosity of 100,000 g of sodium and the mixture is heated 24 hours at i50 °. An elastic siloxane gum is obtained: gel, which is very well suited for working on Si @ l'oxankautschulc. EXAMPLE 3 100 g of dimethylsiloxane of Example 1 are added with good stirring to a solution of 0.5 g of phosphorous acid dichloride anilide in 4 cc of chloroform and allowed to stand at room temperature for 2 days. It forms a plastic-elastic Siloxangummigel.

If this polymer is tert with 8o g of diatomaceous earth and 4 g. Butyl perbenzoate rolled, pressed in a vulcanization for T5 minutes at 15o ° and then heated for 4 hours at 25o °, we obtain a siloxane gum with a tensile strength of 45 kg / cm2 at an elongation at break of 130 '/ o and a Shore hardness of 6o.

EXAMPLE 4 100 g of the dimetylsiloxane of Example 1 are heated to 100 ° C. and, while stirring well, ig of phosphoric acid dichloride anilide is added. After the addition, the temperature is increased to 12o ° and obtained after 2 hours, a suitable for the production of siloxane rubber polymer.

EXAMPLE 100 g of dimethylsiloxane of Example 1 are treated with a solution of 0.2 g of phosphoric acid anilide-anil in 10 ml of alcohol. After thorough mixing, the mass is heated to 15 °, until a viscous polymer is obtained on cooling. From this, a siloxane rubber with good mechanical properties can be produced.

Example 6 A metbylphenylsiloxane oil, obtained by conventional hydrolysis of methylphenyldichlorosilane and having a viscosity of about 100 ° C., is treated with 0.3% of phosphorous acid dichloride ethylanilide and heated to 13 ° C. with stirring for 5 hours. After cooling, a tough polymer is obtained. the processing with fillers and peroxides gives a Si.lbxankautschulc with good strength properties.

Example? In: same as dimethyl and Methylphenyls.iloxan can also ethylmethyl-dibutyl, diphenyl, Trimethyle.ilmethylenmethyl-, Methylchlorphenylsiloxan or mixtures of the individual siloxanes with the above-mentioned examples P'hosphor-nitrogen compounds in high molecular weight liquids or Transfer gels suitable for processing on siloxane gum.