RU2356117C2 - Low-viscosity siloxane composition - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention concerns low-viscosity siloxane compositions which can be solidified at room temperature and form elastomer materials applicable as dielectrics and insulators. Invention claims low-viscosity siloxane composition including, weight parts: polyorganosiloxanediol - polydimethylsiloxanediol or polydimethyl(methylphenyl) siloxanediol or their mix at the molar weight ratio of (2÷1):1, 15÷100 thousand - 100, partial tetraethoxysilane hydrolysis product - 4.0÷7.2, amonisilane selected out of group including γ-aminopropyltriethoxysilane or its mix with (3-aminoisopropyltriethoxysilane or diethylamonipropyltetraethoxysilane - 0.5÷1.0. Composition can include fine-dispersed filler quartz, silicon dioxide or dolomite powder, iron, titanium, aluminium, chrome or zinc oxides or their mixes, boron or aluminium nitrides, or mixes of carbon black with metal oxides, oligodimethylsiloxane.

EFFECT: low-viscosity siloxane composition for obtainment of elastic dielectric material without corrosion effect on non-ferrous metals, with high dielectric properties, enhanced substrate adhesion and reduced toxicity, at room temperature.

8 cl, 2 tbl, 2 ex

Description

The invention relates to the field of low-viscosity siloxane compositions capable of curing at room temperature with the formation of elastomeric materials that can be used as dielectrics and insulators used in the form of sealants, compounds, coatings in mechanical engineering, including in instrumentation and electronics.

Known compositions based on liquid siloxane rubbers with terminal silanol groups, obtained by mixing rubbers, crosslinking agents containing hydrolyzable alkoxy or acyloxy groups, and cold vulcanization catalysts, which are usually used organotin (Ukrainian patent No. 54005, author certificate. USSR No. 496293, 1685962) or organotitanium compounds (patent JP 11228700).

The disadvantages of the known compositions are increased corrosion activity and toxicity due to the use of organotin and organotitanic compounds.

The closest in composition analogue adopted for the prototype is a low viscosity siloxane composition, including, by weight:

liquid siloxane rubber with end silanol groups one hundred ethyl silicate 30-80 organotin catalyst 3.0-12.0 alkyl (aryl) acetoxysilane 0.5-1.5

(RF patent No. 2052475).

The disadvantages of the prototype composition are: increased corrosion activity due to the content of a significant amount of acid components in it, since during the vulcanization process an acid is released that causes corrosion of metals, especially non-ferrous (copper, silver, their alloys), which makes it unsuitable for use in instrumentation, the ability to cure only in a thin layer, low dielectric properties. In addition, the used organotin catalysts are highly toxic substances.

The technical task of the invention is the development of a low-viscosity siloxane composition to obtain at room temperature an elastic material that does not cause corrosion of non-ferrous metals, having high dielectric properties, increased adhesion to substrates and reduced toxicity.

To solve this problem, a low-viscosity siloxane composition is proposed, including liquid siloxane rubber with terminal silanol groups, a product of partial hydrolysis of tetraethoxysilane and a catalyst, characterized in that it contains polyorganosiloxane diol mol. M as liquid siloxane rubber with terminal silanol groups. 15-100 thousand, and as a catalyst - aminosilane in the following ratio of components, parts by weight:

polyorganosiloxanediol mol.m. 15-100 thousand one hundred product of partial hydrolysis of tetraethoxysilane 4.0-7.2 aminosilane 0.5-1.0

As a polyorganosiloxanediol, the composition contains polydimethylsiloxanediol or polydimethyl (methylphenyl) siloxanediol or a mixture thereof in a ratio of (2-1): 1.

As an aminosilane, the composition comprises an aminosilane selected from the group consisting of γ-aminopropyltriethoxysilane or a mixture thereof with β-aminoisopropyltriethoxysilane or diethylaminopropyltetraethoxysilane.

In order to increase the mechanical properties, the composition may additionally contain a finely divided filler in an amount of 25.0-263.0 wt.h. As a filler, the composition may contain quartz, silicon dioxide or dolomite flour, oxides of iron, titanium, aluminum, chromium or zinc, or a mixture thereof, boron or aluminum nitrides, or a mixture of carbon black with metal oxides.

In order to control the viscosity, the composition may additionally contain oligodimethylsiloxane in an amount of from 10-30 parts by weight.

The correct qualitative and quantitative selection of the catalyst and the crosslinking agent in the composition ensures that, after curing at room temperature, an elastomeric dielectric material is obtained with minimal release of non-aggressive by-products (water, ethyl alcohol), which explains the absence of the corrosive effect of the composition on non-ferrous metals.

The chemical nature of the siloxane rubber used, the correct selection of fillers and the absence of by-products of vulcanization with electrolytic properties provides a high level of dielectric properties of the vulcanizates of the claimed composition.

The combination of active groups of the components of the composition allows to obtain an elastomeric material with increased adhesion to various substrates.

As the organopolysiloxane diol in the present invention can be used various organopolysiloxane diols mol.m. 15-100 thousand, but the best technical result is achieved when using polydimethylsiloxanediol of the grades SKTN "G", SKTN "B", SKTN "A" (GOST 13835-73), polydimethyl (methylphenyl) siloxanediol grade SKTNF "B" with a content of 4- 50 mol% of methylphenylsiloxane units (TU 38.108129-77), as well as mixtures thereof in a ratio of (2-1): 1.

The product of partial hydrolysis of tetraethoxysilane - ethyl silicate-40 with a SiO ₂ content _of 38-43% (GOST 26371-81) was used as a crosslinking agent.

As aminosilane, it is most preferable to use γ-aminopropyltriethoxysilane or its mixture with β-aminoisopropyltriethoxysilane (TU 6-02-724-73) or diethylaminopropyltetraethoxysilane (TU 6-02-586-86).

As a viscosity regulator, oligodimethylsiloxanes with kinematic viscosity at 20 ° C from 5 to 150 mm ² / s, preferably with a viscosity of 10-150 mm ² / s, grades PMS-10, PMS-50, PMS-150 (GOST 23175) can be used -78).

Silica (TU 2168-016-002048-72-2003), quartz, metal oxides - iron (GOST 4173-77), zinc (GOST 202-84), titanium (TU 6-10-1252) were used as finely dispersed inorganic fillers. -86), aluminum, chromium (GOST 2.912-79) or a mixture thereof, boron nitrides (TU 2-036-707-77), aluminum or a mixture of carbon black, for example, grade P-803 (GOST 7885-86) with oxides metals.

Examples of implementation

Example 1

To 100 parts by weight polydimethylsiloxanediol with a molecular weight of 15 thousand (SKTN "A") was added 4.5 wt.h. ethyl silicate - 40 and 0.5 parts by weight γ-aminopropyltriethoxysilane. The composition was mixed for 5 minutes and used to fill the prepared products. A control sample for studying the properties of the compound was formed in the form of a plate ~ 2 mm thick. The tests were carried out after three days of exposure of the samples at room temperature.

Example 2

K 66.7 parts by weight polydimethylsiloxanediol with a molecular weight of 50 thousand (SKTN "G") was added 33.3 wt.h. polydimethyl (methylphenyl) siloxanediol with a molecular weight of 20 thousand (SKTNF "B"), was introduced 200 wt.h. zinc oxide and 6 parts by weight iron oxide, was stirred for 2 hours on a glue mixer until a homogeneous paste. 6.5 parts by weight of the paste were introduced. ethyl silicate-40, 0.5 parts by weight γ-aminopropyltriethoxysilane and 0.2 parts by weight β-aminoisopropyltriethoxysilane. The mixture was stirred for 5 minutes and used to fill the prepared products.

The compositions of examples 3-9 are prepared in a similar manner.

The invention is not limited to these examples.

Table 1 shows the compositions of the claimed composition, table 2 - comparative properties.

From the data presented in table 2, it can be seen that the proposed low-viscosity siloxane composition has significant advantages both in technological parameters - it contains components of at least 4 toxicity classes instead of the 1-2 class of the prototype, has a pot life (in layers of at least 3 cm) from 40 minutes to 6 hours instead of 5-10 days in the prototype, and in terms of performance, it has its own adhesion to metal substrates (it has a cohesive peeling when peeling instead of the adhesive in the prototype), does not cause non-ferrous metals in contrast to the prototype and has high dielectric characteristics (ρ _v , ρ _s - several orders of magnitude higher) compared to the prototype.

The application of the invention allows reliable sealing and electrical insulation of products with materials that retain elasticity and dielectric properties during long-term operation in the temperature range from minus 120 ° C to plus 300 ° C, while the prototype compositions lose their elasticity during long-term storage even at room temperature due to the high content of structuring agents.

High technological properties, low toxicity, high dielectric characteristics, intrinsic adhesion to various metals, and operability in a wide temperature range make it possible to apply the invention in various fields of instrumentation with a significant reduction in labor intensity and energy intensity of the production process, as well as to ensure the environmental safety of sealing processes.

Claims (8)

1. A low viscosity siloxane composition comprising liquid siloxane rubber with terminal silanol groups, a product of partial hydrolysis of tetraethoxysilane and a catalyst, characterized in that it contains polyorganosiloxane diol with a mol.m as liquid siloxane rubber with terminal silanol groups. 15 ÷ 100 thousand, and as a catalyst - aminosilane in the following ratio of components, parts by weight:
polyorganosiloxanediol, mol.m. 15 ÷ 100 thousand one hundred product of partial hydrolysis of tetraethoxysilane 4.0 ÷ 7.2 aminosilane 0.5 ÷ 1.0 2. The low-viscosity siloxane composition according to claim 1, characterized in that it contains polydimethylsiloxane diol or polydimethyl (methylphenyl) siloxane diol, or a mixture thereof in a ratio of (2 ÷ 1): 1 as polyorganosiloxane diol. 3. The low viscosity siloxane composition according to claim 1, characterized in that it contains aminosilane as an aminosilane selected from the group consisting of γ-aminopropyltriethoxysilane or a mixture thereof with β-aminoisopropyltriethoxysilane or diethylaminopropyltetraethoxysilane. 4. The low-viscosity siloxane composition according to claim 1, characterized in that it further comprises a filler in an amount of 25.0 ÷ 263.0 wt.h. 5. The low-viscosity siloxane composition according to claim 4, characterized in that it contains quartz, silicon dioxide or dolomite flour as a filler. 6. The low viscosity siloxane composition according to claim 4, characterized in that it contains oxides of iron, titanium, aluminum, chromium or zinc, or mixtures thereof, or mixtures thereof with carbon black as a filler. 7. The low viscosity siloxane composition according to claim 4, characterized in that it contains boron or aluminum nitrides as a filler. 8. The low-viscosity siloxane composition according to claim 1, characterized in that it further comprises oligodimethylsiloxane in an amount of 10.0 ÷ 30.0 wt.h.