DE2158825C3 - Catalysis of organopolysiloxane compositions curable to form solid elastomers - Google Patents

Description

Hydrogen atoms be bonded to terminal silicon atoms. Component (2) can therefore be, for example, a copolymer of (CH ₃ ) ₂ SiO and / or (CH ₃ ) -HSiO units and (CH ₃ ) ₂ HSiO £ units. The copolymers of methylhydrogensiloxane units and trimethylsiloxane units are particularly preferred.

The sum of the vinyl radicals per molecule in component (1) and the silicon-bonded hydrogen atoms per molecule in component (2) should be at least five. So if two vinyl residues per molecule present in component (1), the organosiloxane (2) should have at least three s. ^. bound hydrogen atoms per molecule and vice versa.

Components (1) and (2) are preferably used in proportions in such proportions applied that there is a ratio of at least one silicon-bonded hydrogen atom per unsaturated radical in component (1) results. An excess of silicon-bonded hydrogen normally leads to a more effective hardening of the mass. A ratio of silicon-bonded is particularly preferred Hydrogen atoms in component (2) to unsaturated groups in component (1) of 2: 1 to 10: 1.

Component (3) of the mass consists of platinum acetylacetonate _{, Pt (CH 3 COCHCOCH 3} ) ₂ . For some applications, this component can be used in amounts which are customary for platinum catalysts in this reaction, ie in amounts of about 2 to about 20 parts by weight of platinum as metal per milhon parts by weight of component (1) and (2) in total. If the molding composition is intended for processing by extrusion, the platinum compound (3) is preferably used in larger amounts, e.g. B. m amounts up to 40 or more parts by weight of the metal per million parts of the total weight of (1) and (2)

The masses can be used for the production of elastomers be prepared for different purposes and contain one or more fillers and / or other additives that modify the properties of the end product may be required. Examples of fillers that can be used are pyrogenic silicon dioxide types produced, precipitated silicon dioxide types, diatomaceous earths, ground quartz, pyrogenic produced aluminum and titanium oxides, zinc oxide, graphite, zirconium silicate, calcium carbonate, metal powder, Asbestos fibers, titanium dioxide and types of carbon black. The fillers can be used in conventional amounts, e.g. B. 5 to 150 parts by weight based on the weight of (1) and (2) can be used.

Other additives that can be contained in the compositions are, for example, pigments and plasticizers and heat stabilizers.

The masses can by exposure to elevated temperatures, for. B. 150 to 275 ° C, can be converted into the solid elastic state. However, they are resistant to premature curing even at temperatures of about 40 to 50 ^° C. for times of 10 hours or more. This time can be extended by introducing a compound into the mass which inhibits the activity of the platinum catalyst at such temperatures, e.g. B. benzotriazole or triphenylphosphine. A preferred compound for this purpose is methyl ethyl ketoxime.

The masses are particularly suitable for the production of products that duich an extrusion process be shaped, e.g. B. sheathing or electrical insulation, but they can also be found for the Manufacture of seals and as a sealing compound !! Use.

Through the following examples, in which parts are based on weight, the Invention explained in more detail.

example 1

The following substances are _{mixed with a rubber m} ^ _ünd , i.

trimethylsilyl endblocked copolymer of 99.72 mol percent (CH ₃ ) _a -SiO units and 0.28 mol percent
(CH ₃ ) CH ₂ = CHSiO units
(Molecular weight 2 · 10 ⁵ ) 100 parts

»° Pyvogenically generated SiO ₂ (surface

300 m ² / g) 50 parts

Polydimethylsiloxane with hydroxyl end groups (50 cSt. At 25 ° C) 15 parts

150 parts of this mass are combined with 0.75 parts of a

^a5 Methylhydrogenpoly trimethylsilyl _{siloxane having a Mo} i _e weight of from about 3000 _{and Sovie]} pi _at i _n acetylacetonate added that a

_{Content of 40 Tdlen p} , _{atm Mi} " _{ion Td) e des}

_Me thylvinylsiloxane copolymers results. The platinum _{connection wJrd alg Löjn e [what dichloromethane to} .

_{m is gefundenj that the} Pro _{domestic product} obtained _{at least 24} hours when stored at 22 ° C and even at 40 "C is stable and that during _{this no} change _{or virtually} the _{zdt kdne}

_Plasticity takes place. The composition cures on the position _{run bd 30 sec} exposure to a temperature about 250 _V on ⁰ C to form an elastomer. For comparison purposes, a similar _{composition is used} , but using chloroplatinic acid (10 ppmPt) in place

_des pi _atinacety , _acetonatSi produced and stored. _{This mass hardens} · _{η 1Q h bd 22} o _{C to dnem} rubber

eispi

The following substances are mixed thoroughly with a rubber compounding device:

vinyl-containing copolymer SiO ₂ 'produced by secondary pyrogen (surface
300 m ² / g) 50 parts

Polydimethylsiloxane with hydroxyl end groups (viscosity 50 cSt. At
25 ⁰ O 17 5 parts

A dichloromethane solution is prepared, the ratio of platinum acetylacetonate and methyl ethyl ketoxime of 10 moles of ketoxime dissolved to 1 mole of platinum complex. Part of the solution is then using 0.75 parts of a trimethylsilylendblocked Methylhydrogenpolysiloxans mixed and the mixture is introduced into the mass described above. So much solution is used that the mass obtained Contains 5 parts of platinum as metal per million parts of vinyl-containing copolymer.

The mass is stable for at least 3 days if it is kept at 22 ° C, and during this

This time there is no noticeable change in plasticity. When the mass inter-pressure molded for 10 minutes at 170 ⁰ C, it is converted into an elastomer having the following properties.

Tensile Strength, kg / cm ² (psi) 80 (1140)

Ionization at break% 370

Hardness (IRHD) 63

Tensile strength, kg (Ib.) 7.3 (16)

The physical properties were determined according to British Standard 903, Part A2, 1956 (Type E dumbell), British Standard 903, Part A26, - 1960 and British Standard 903, Part A3., Measured in 1956.

Claims (1)

However, if such high concentrations of catalyst Claim: can be applied, the hardening rate of the Pro at the temperatures that are inside the extru- Use of platinum acetylacetonate as a catalyst prevail, reach a considerable extent. In the case of organo- 5 continuous operation of the extruder, which can be hardened into solid elastomers, polysiloxane compositions from (1) a polydiorganosi- no difficulties arise from the use of the loxane with 1.95 to 2.01 organic residues per elastomeric substance, an interruption of the silicon atom In which at least 50% of the organic extrusion process can, however, result in at least parnic residues in the polydiorganosiloxane methyl tial hardening and solidification of the product inside residues and at least two organic residues per io of the extruder.
Molecule are vinyl radicals and all other radicals The Platmacetylaceto- used according to the invention from alkyl radicals with 2 to 18 carbon atoms, nat is surprisingly a particularly advantageous one Phenyl radicals, fluoroalkyl radicals or cyanoalkyl catalyst for use for the masses mentioned and (2) an organosiloxane with type intended for processing by extrusion are at least two silicon-bonded hydrogen-15. The use of platinum acetylacetonate as a atoms per molecule, where the sum of the vinyl catalyst results in elastomer-forming masses, residues per molecule in component (1) and those at the temperatures normally found in the silicon-bonded compound Hydrogen atoms per molecule can be achieved by extruders, not prematurely in component (2) is at least 5. harden. ao At least 50% of the organic residues in the polydiorganosiloxane (1) are methyl radicals and at least two silicon-bonded radicals per molecule are vinyl leftovers. All other radicals are made up of alkyl radicals 2 to 18 carbon atoms, e.g. B. ethyl, propyl, »5 butyl, decyl or octadecyl residues, phenyl residues as well as fluoroalkyl or cyanoalkyl radicals, e.g. B. 3,3,3- The invention relates to the use of trifluoropropyl or cyanopropyl radicals.
Platinum acetylacetonate as a catalyst in too solid Elastomer curable organopolysiloxane compositions made from polydiorganosiloxanes are preferred, in which the orga- (1) a polydiorganosiloxane with 1.95 to 2.01 organic radicals composed of methyl and vinyl radicals with or niche radicals per silicon atom, wherein at least without phenyl and / or 3,3,3-Trifluorpropylresten be-50% of the organic residues in the Polydiorgano- stand. Furthermore, the vinyl radicals preferably make up siloxane methyl radicals and at least two organic 0.05 to 1.00% of the total organic radicals in (1) radicals per molecule are vinyl radicals and all the others are present as methylvinylsiloxane units. Rests composed of alkyl radicals with 2 to 18 carbon atoms, 35 but they can also be present in the form of units of other phenyl radicals, fluoroalkyl radicals or cyanoalkyl radicals, e.g. B. ethylvinylsiloxane units exist, and (2) an organosiloxane with at least and dimethylvinylsiloxane units.
two silicon-bonded hydrogen atoms per mole - examples of the preferred polydiorganosiloxanes kül, where the sum of the vinyl radicals per molecule (1) are therefore copolymers of dimethylsiloxane units Component (1) and the silicon-bonded 40th and methylvinylsiloxane units, copolymers from Hydrogen atoms per molecule in component (2) at least dimethylsiloxane, methylvinylsiloxane and phenyl 5 is. methylsiloxane units or copolymers from di- Various organosiloxane compositions are known for the methylsiloxane, methylvinylsiloxane and methyl (3,3,3 production of elastomers. In the poly-trifluoropropyl) -siloxane units. If desired, number of cases takes place the conversion of the mass into 45, the Copo'ymeren end groups from Triorganoden cured elastomeric state with the help of siloxane units, z. B. trimethylsiloxane units or one or more vulcanizing agents, hardening dimethylphenylsiloxane units,
catalysts and / o ^ he crosslinking agents instead. For most purposes, the of such a class of compositions are the essential polydiorganosiloxanes having a molecular weight of over borrowed active components from an organo-5 ° 50000 and are usually rubbery solids, silicon polymer, the olefinically unsaturated sub- component (2) can be composed of any contains tuenten, an organosilicon compound, the organosiloxane with at least two silicon-bonded contains silicon-bonded hydrogen atoms and one hydrogen atom. Linear ones are preferred Metal of the platinum group or certain compounds, however, can also include siloxane polymers, cyclic siloxanes or complexes thereof can be used as a catalyst for conveyance. The organic residues that are in tion of the reaction between the organosilicon component (2) are preferably alkyl polymers and the organosilicon compound. residues with fewer than 19 carbon atoms, e.g. B. The known elastomerbüdenden masses of this type of methyl, ethyl, propyl, decyl or tetradecyl radicals are satisfactory for some purposes. or phenyl radicals. The preferred organosiloxanes (2) If, on the other hand, it is necessary to process the compositions by a linear or practically linear siloxane poly extrusion process, these compositions, which have methyl and / or ene as organic substituents, have a considerable disadvantage. Processing or containing phenyl residues. You can make homopolyder masses by extrusion, it requires in the mers or copolymers se <n and, for example, only from practice that they are converted in a short time into the hardened (CH ₃ ) HSiO units or from these units to an elastic state. Short curing 65 together with copolymer units, such as dimethylation times, e.g. B. from 20 to 60 see at 180 to 300 ⁰ C siloxane units, phenylmethylsiloxane units and can easily exist by using a suitably high trimethylsiloxane units. Desired concentration of the platinum catalyst can be achieved. if at least some of the silicon-bonded