DE1105162B - Compounds based on organopolysiloxanes which can be hardened to give elastomers - Google Patents

Description

Compounds curable to elastomers based on organopolysiloxanes It is known to boric acid, boric anhydride and boric acid alkyl esters in very small amounts To incorporate quantities into compounds based on organopolysiloxanes that can be hardened to give elastomers, to facilitate their processing, for example by extrusion.

The retarding effectiveness of a boron compound, i. H. preventing stiffening of reinforcing fillers uncured organopolysiloxane during storage, although it rises above a certain minimum amount of boron present, but generally has an effect an increase in the amount of the boron compound also adversely affects other physical ones Properties from; it increases, for example, the permanent elongation with a reduction of elasticity.

The invention now relates to boron-containing compounds which can be hardened to give elastomers Compounds based on organopolysiloxanes and reinforcing silica fillers, which do not tighten up during storage and those made from them Elastomers have a lower permanent elongation than previously usual.

The new masses are characterized by the fact that a smaller amount of boron, than previously necessary, is used, namely catalytic amounts' namely 0.01 to 0.16 part, preferably 0.02 to 0.06 part, of boron in the form of tristriorganosilyl borate to 100 parts of the mixture of organopolysiloxane and filler.

The organopolysiloxane can have a viscosity of as little as 10,000 cSt / 25 "C and must contain at least 50 mole percent dimethylsiloxane units. in the essential are all units of polysiloxanes that can be processed into elastomers Diorganosiloxane units, but it is known that small amounts of triorganosiloxane and monoorganosiloxane units and SiO2 units are present; the remaining organic radicals and the organic radicals in the triorganosilyl groups of the invention Borates used can be monovalent, optionally halogenated hydrocarbon radicals be.

Examples include: alkyl radicals such as methyl, ethyl, Isopropyl, telt.-butyl and octadecyl, alkenyl radicals such as vinyl, allyl, methallyl, Dodecenyl and butadienyl, cycloalkyl radicals such as cyclopentyl and cyclohexyl, cycloalkenyl radicals such as cyclopentenyl and cyclohexadienyl, aryl radicals such as phenyl, xenyl and naphthyl, Aralkyl radicals such as benzyl, alkaryl radicals such as toluyl and xylyl and the corresponding halogenated derivatives such as chloromethyl, 3,3,3-trifluoropropyl, α-chloro-α, β, β-tri fluorocyclobutyl, 2-bromovinyl, 2,3-dibromo-2-cyclopentenyl, a, a-difluorobenzyl, perchlorophenyl, a, a, a-Trifluorotoluyl and 2,4,6-Tribromobenzyl.

The diorganopolysiloxane is preferably dimethylpolysiloxane or also a mixed polymer containing at least 500 / o dimethylsiloxane units in addition to others, diorganosiloxane units composed of any of the aforementioned types of radicals. Examples include: A copolymer made from 50 mol percent dimethylsiloxane, 40 mole percent phenylmethylsiloxane and 10 mole percent methylvinylsiloxane units, a mixed polymer of 70 mol percent dimethylsiloxane and 30 mol percent 3,3,3-trifluoropropylmethylsiloxane units, a mixed polymer of 80 mol percent dimethylsiloxane, 5 mol percent phenyl-a, a, a-trifluorotolylsiloxane, 5 mol percent a-chlorine-a, ß, S-trifluorocyclobutylmethylsiloxane, 5 mol percent phenylmethylsiloxane, 3 mole percent diphenylsiloxane, 1.9 mole percent bis-2-bromoethylsiloxane, 0.04 mole percent Dimethyl-2-bromovinylsiloxane, 0.04 mole percent monophenylsiloxane, and 0.02 mole percent SiO2 units. These copolymers are only examples of those according to the invention suitable types of diorganopolysiloxanes.

If less than 50 mole percent of the siloxane is made up of dimethylsiloxane units exist, the effectiveness of the boron compound used in the present invention is so far reduced, that no advantage over the previously used tampering delay Means is given more. There are too many triorganosiloxane or monoorganosiloxane units or SiO2 units are present in any combination, then the physical Properties of both the uncured, highly viscous mass and the elastomer adversely affected.

The tristriorganosilyl borate used in the present invention has the general Formula (R3SiO) 8B, where R any of the monovalent, optionally halogenated hydrocarbon radicals in the units of the organopolysiloxane may be present means. The production is generally carried out by 24 hours or even longer heating of R3 Si Cl and boric acid under reflux followed by Distillation. R is preferably the methyl radical in order to reduce the proportion of other organic To keep substances in the organopolysiloxane elastomer as low as possible. According to the invention used boron compound is, however, regardless of which of the described halogenated or non-halogenated monovalent hydrocarbon radicals as R are contained therein, effective in any case.

When the amount of the boron is less than 0.01 part per 100 parts of the organopolysiloxane the boron has practically no more anti-clogging effect. Amounts to the amount of boron more than 0.16 part per 100 parts of the organopolysiloxane so causes the additional boron does not increase the tightening resistance of the Mixture and affect other physical properties. The boron compounds can also be added as mixtures.

The borates used according to the invention are only effective when reinforcing Silica fillers are used in the elastomers. Is considered reinforcing a filler with a surface area of at least 50 m2 per gram. According to the invention there is no critical upper limit for the surface area; the latter can for example 900 m2 or more per gram. Such fillers are about under preservation the structure dehydrated silica hydrogels, obtained pyrogenically in the gas phase Silicas and silicic acid xerogels; they can be used in amounts of, for example, 5 up to 100 parts, preferably from 15 to 80 parts, per 100 parts of the siloxane to be available.

Reinforcing fillers are also suitable USA. Patent 2610167 described processes were treated. The treatment the silicas described there consists in the reaction with reactive ones Silanes, such as hydrolyzable organosilicon halides or silazanes, or up to to some extent with organosilicic acid esters in vapor form, as liquids or in an inert solvent.

As examples of Organosilvlgruppen, which via SiOSi bonds to the surface of the silica can be bound, are mentioned: Monomethyl-, Monooctade Qvl, monophenyl, diethyl, monovinyl, triphenyl silyl groups as well Mixtures of dimethylsilyl and trimethylsilyl groups. Those used to treat Organosilicon compounds used in fillers carry any monovalent hydrocarbon radicals with preferably up to 18 carbon atoms, for example alkyl radicals such as methyl, butyl, Isopropyl or tert-butyl, alkenyl radicals such as hexenyl, oleyl or allyl, cycloaliphatic Residues such as cyclohexyl, cyclohexenyl, cyclopentyl or methylcyclohexyl, aromatic Hydrocarbon radicals such as toluyl, xenyl, naphthyl or anthracyl and aralkyl radicals like benzyl.

Hydroxyl compounds of hydrocarbons can also be used as fillers treated colloidal silicas can be used.

As examples of hydrocarbonoxy groups with which the surface the silicic acid is esterified in this case: methoxy, ethoxy, butoxy, Octadecyloxy, allyloxy, cydohexyloxy, phenoxy, 2,2,4 trimethylhexyloxy, isopropoxy, Benzyloxy, cinnamyloxyl, propargyloxy and oleyloxy.

Optionally, the inventive use of the designated boron compounds Mixtures provided also contain fillers, whose surface is less than 50 m2 per gram, like ground diatomaceous earth Quartz, sand, or metal oxides, for example titanium dioxide or zinc oxide.

The mixtures can optionally also contain curing catalysts. Two types of catalysts can be used. If the mixture does not contain any SiH groups or silicic acid esters are organic peroxides such as benzoyl peroxide and bisdichlorobenzoyl peroxide or dicumyl peroxide to be preferred. The hardening then takes place through the action of the peroxide on the organic group in the organopolysiloxane. Contains the organopolysiloxane SiH groups or is it with polysilicic acid alkyl esters or with a SiH-containing one Organopolysiloxane mixed, then salts of carboxylic acids, such as lead-2-ethylhexoate, Dibutyltin dilaurate, tin octoate and iron naphthenate are suitable as catalysts.

The mixtures according to the invention can also be cured by irradiation take place, for example by electrons with high energy, gamma rays or X-rays. A curing catalyst is then superfluous.

The mixtures are prepared by adding the constituents mixed in a manner known per se, preferably by rolling. Possibly A hardener can be added at the same time if the latter is not under the mixing conditions reacted; however, the hardener can also only be added when the mixture is used.

The mixtures can also contain other additives, such as pigments and oxidation inhibitors or additives to reduce permanent deformation.

The mixtures can be extruded and rolled very well; she have good resistance to moisture both before and after Hardening, high tensile strength and excellent electrical properties in comparison to similar mixtures containing boric acid esters and the like. Besides, they can volatile constituents can be removed by heating without impairing the resistance of the stick decreases noticeably against tightening. They are used to manufacture everyone Products to which organopolysiloxane elastomers are commonly used, for example insulating tapes are suitable.

Example A base material is used which contains the following components: 100 parts by weight of a highly viscous dimethylpolysiloxane composition with a plasticity according to Williams of 1 cm with 0.142 mole percent methylvinylsiloxane units and additional end-blocking vinyldimethylsiloxane units in the ratio of one vinyl group in an end-blocking unit for each 5000 Si atoms, 35 parts by weight of a pyrogenic Silica obtained in the gas phase with a surface area of about 150 to 200 m2 per gram, 0.5 part by weight of iron oxide, 1.0 part by weight of bisdichlorobenzoyl peroxide.

The latter two ingredients were in dimethylpolysiloxane pastes dispersed added to the dispersion in the highly viscous mass and in the filler to facilitate.

Six samples were made from this stick. Boron in the form of tristrimethylsilyl borate according to the invention was added to samples 1 to 4 inclusive in the amounts given below; triethyl borate was added to sample 5; Sample 6, which did not contain a boron compound, served as a comparative sample. A part of each sample was stored for 3 days and then "softened", ie rolled until it formed a smooth skin on the roller. The remainder of each sample was not rolled for 2 weeks. The time required for the stored stick to "soften" was recorded. Each sample was then molded in a press for 5 minutes at 125 ° C. The cured samples were then tested for permanent elongation. The specimens, which had been stored for 2 weeks before the deformation, were then cured for 24 hours at 250 ° C. and, after being heated for 22 hours at 1500 ° C., the permanent deformation was measured with compression. The table shows the results. Permanent Permanent deformation (%) Prabe Boe "ge softening time Remaining softening time Elongation (01,) (after after deformation after with stretching (0/0) after 2 weeks with deformation 22 hours at 150 ° C Deformation after 3 days after storage after 2 weeks (hardening Storage Storage for 3 days 24 hours / 250 ° C) 1 0.04 60 seconds 10 305 seconds 3 19.7 2 0.08 30 seconds 28 140 seconds 20 36.0 3 0.12 15 seconds 24 75 seconds 17 39.0 4 0.16 0 seconds 20 30 seconds 24 47.8 5 0.11 90 seconds 20 295 seconds 10 29.6 6 0 900 seconds 12 was not not - softly deformable It turns out that the softening time of the sample containing boron in the form of triethyl borate, ie sample 5, corresponds approximately to the softening time of that sample which, according to the invention, contains a third of the amount of boron as tristrimethylsilyl borate (sample 1). The softening time is a measure of the hardening that has occurred during the specified aging times and thus also a measure of the resistance of the boron-containing organopolysiloxanes to hardening.

This experiment shows that boron, which is in the form of tristrimethylsilylborate an organopolysiloxane was added, results in a mixture whose permanent elongation the half or a third is and their resistance to rigging as well is as large as a stick that has almost three times the amount of boron in the form of Contains triethyl borate.

Masses with similar excellent properties are obtained, when the highly viscous dimethylpolysiloxane composition is replaced by one of the following highly viscous Polysiloxane masses are replaced: one end-blocked with vinyldimethylsiloxy groups Dimethylpolysiloxane with a viscosity of 11,000 cStl2S "C, one with hydroxyl groups end-blocked, highly viscous dimethylpolysiloxane with Williams plasticity of 2 cm, a copolymer of 55 mol percent dimethylsiloxane, 27 mol percent 3,3,3-trifluoropropylmethylsiloxane, 9 mole percent methylvinylsiloxane, 5 mole percent a, a, a-trifluorotolylbenzylsiloxane, 3.9 mole percent diphenylsiloxane and 0.1 mole percent trimethylsiloxy units copolymer end-blocked with hydroxyl groups made of 85 mol percent dimethylsiloxane, 5 mole percent chlorophenyl-2,2-dibromoethylsiloxane, 5 mole percent bischloromethylsiloxane, 3 mole percent cyclo- hexylcyclopentenylsiloxane and 2 mole percent octadecylmethylsiloxane units with a Williams plasticity of 1.5 cm, one end-blocked with hydroxyl groups Mixed polymer of 70 mol percent dimethylsiloxane and 30 mol percent phenylmethylsiloxane units with a Williams plasticity of 1.75 cm, one end-blocked with hydroxyl groups Mixed polymer of 65 mol percent dimethylsiloxane, 30 mol percent phenylmethylsiloxane and 5 mole percent methylvinylsiloxane units having Williams plasticity of 0.5 cm.

The tristrimethylsilyl borate can be replaced by the following borates: Tristriethylsilylborate, tris-3, 3,3-trifluoropropyldimethylsilylborate, trisphenyldimethylsilylborate, Triethylsilyl bis-tri-t-butylsilyl borate, trischlorophenyldimethylsilyl borate Mixture of 90 percent by weight tristrimethylsilyl borate and 10 percent by weight tristrioctadecylsilyl borate, Tris-dimethyl vinylsilyl borate.

Claims (1)

PATEXT.tNSPPTI CH Compound curable into elastomers based on Organopolysiloxanes, reinforcing silica fillers and boron compounds in catalytic amounts containing a tristriorganosilyl borate as boron compound, wherein the organic radicals are monovalent, optionally halogenated hydrocarbon radicals are. ~~~~~~~ Publications considered: Office Patent No. 9957 for inventions and patents in the Soviet zone of occupation in Germany.