RU2249027C1 - Law molecular siloxane rubber-based sealing compound - Google Patents

Abstract

FIELD: hermetic based on law molecular siloxane rubber, in particular sealing composition.

SUBSTANCE: invention relates to sealing composition vulcanized by reaction with air moisture. Claimed rubber-based composition comprising zinc oxide, ethyl silicate, and diethylaminomethyltriethoxysilane, contains additionally pulverized grinded quartz. As a variant hermetic also contains chalk and/or dolomite. Composition of present invention is useful in sealing of various conjunctions operating in wide temperature limits where oil and gasoline resistance is required.

EFFECT: hermetic with low-cost components and excellent in operating characteristic.

1 cl, 2 tbl, 7 ex

Description

The invention relates to sealing compositions based on low molecular weight siloxane rubber, and in particular to one-component sealants used in the automotive industry to seal various compounds that require high oil-gas resistance and are used in the temperature range from -50 to + 300 ° C.

Known sealing composition comprising a compound based on low molecular weight siloxane rubber and oligodimethylsiloxane, designed to seal electronic products operating in conditions of high humidity (A.S. 2028361, 1995). The aim of this invention is to increase the stability of the electrical resistance of the vulcanizate in conditions of high humidity and high supply voltage.

The composition of the sealing composition:

Low molecular weight compound

siloxane rubber, wt.% 75-96

Oligodimethylsilaxane

viscosity at 20 ° С 5-150 mm ² / s 4-25

The disadvantage of this sealing composition is the instability in solvents and oils, low (<250 ° C) operating temperature range.

Known sealing composition, including organopolysiloxane diol, ethyl silicate, dialkyltin carboxylate, 8-hydroxyquinoline, used to seal sheet gasket materials, such as gaskets of the joint of the block and head of internal combustion engines (A.p. 1460985, 1992).

The aim of this invention is to increase the viability of the composition and reduce the time and temperature of curing.

The composition of the sealing composition:

Organopolysiloxanediol, parts by weight 100

Ethyl silicate 2.0-4.0

Carboxylated dialkyltin 0.9-3.0

8-hydroxyquinoline 0.7-2.0

The disadvantage of this sealing composition is instability to solvents, high curing temperature (170 ° C), a long time before vulcanization (80-200 hours).

Known sealant, including rubber, zinc oxide, ethyl silicate and a vulcanization accelerator and additionally containing polymethylhydroxysilane, and as a vulcanization accelerator - NN-dimethyl-N-triethoxysiline methylhydrosine (RF patent No. 2188841, 2002), designed to seal various units of aircraft structures operated in a wide temperature range from -60 to + 300 ° C. The composition has the following ratio of components, parts by weight:

Rubber (or organosilicon elastomer,

or polysulfide elastomer) 100

Zinc oxide 100-200

Ethyl silicate 5-16

Polymethylhydrosilane 1-1,4

NN-dimethyl-N-triethoxysiline methylhydrosine 2-7

The disadvantage of this sealant is the long time before the start of vulcanization (3-4 hours) and the long time of complete vulcanization (24-48 hours), which does not allow its use in repair.

The closest in composition is a sealant based on dimethylsiloxane rubber, zinc oxide, ethyl silicate and a vulcanization accelerator diethylaminomethyltriethoxysilane (AS No. 456820, C 08 D 47108, C 09 K 3110).

The composition of this sealant is as follows:

Dimethylsiloxane rubber, parts by weight 100

Zinc oxide 100-200

Ethyl silicate 1-10

Diethylaminomethyltriethoxysilane 2-6

This sealant is waterproof, has satisfactory physical and mechanical properties, and also has good adhesion to the surface of metals.

The disadvantage of this sealant is a reduced tensile strength, a long time before vulcanization (5 hours) and a long time of complete vulcanization (72 hours), which does not allow it to be used for repair work, a small range of operating temperatures (-30 ··· + 250 ° C).

The objective of the present invention is to provide a sealant that cures when exposed to air moisture and has higher performance and lower cost of its constituent components.

The problem is solved in such a way that the sealant based on low molecular weight siloxane rubber containing zinc oxide, ethyl silicate, diethylaminomethyltriethoxysilane additionally contains powdered silica in the following ratio, wt.h .:

Low molecular weight siloxane

rubber 100

Zinc Oxide 5-30

Ground silica dust 40-180

Ethyl Silicate 1-3

Diethylaminomethyltriethoxysilane 1-3

In an embodiment, the sealant further comprises 2-60 parts by weight of chalk. and / or dolomite 2-95 parts by weight

As the main components take:

- low molecular weight siloxane rubber, for example: SKTN grades “B”, “G” and “D”, TU 2294-002-00152000-96, GOST 13835-73; or Siloprene E 18 (passport of the company "Bauer");

- ethyl silicate, TU 6.02-895-78, GOST 26371-84;

- diethylaminomethyltriethoxysilane (ADE-3), TU 6.02-573-87;

- dolomite (dolomite flour), TU 21 BSSR 166-86;

- chalk (calcium carbonate), GOST 8253-79, TU 95-2317-91;

- zinc oxide, GOST 202-84;

- powdered quartz, GOST 9077-72.

The sealant is prepared in stages. First, a mixture of the starting components is prepared in the mixer. Then the resulting mixture is subjected to heat treatment (drying to remove moisture). After heat treatment, the mixture is transferred to a reactor and diethylaminomethyltriethoxysilane and ethyl silicate are added in a stream of dry nitrogen. In the reactor, the mixture is stirred until a homogeneous mass for 1.5-2 hours and packaged in airtight packaging (tubes, cartridges).

To prove the conformity of the claimed composition to the criterion of “industrial applicability”, specific examples of the production of sealant are given (Table 1).

Table 1 Name of components Loading rates, example no., Parts by weight Prototype
7 1 2 3 4 5 6 SKTN “B” 100 - - - 100 - - SKTN “G” - 100 - - - 100 - SKTN “D” - - 100 - - - 100 SILOPRENE E18 - - - 100 - - - Zinc oxide twenty twenty twenty 5 twenty thirty 100-200 a piece of chalk - 60 35 - - 60 - Dolomite - - 35 - 95 - - Powdered ground quartz 180 95 95 180 80 95 - Ethyl silicate 2 2 2 2 2 2 1-10 Diethylaminomethyltriethoxysilane 1.8 1.8 1.8 1.8 1.8 1.8 2-6

The procedure for obtaining sealant will be considered in example 1.

In a special mixer with a z-shaped mixing device load 100 kg of low molecular weight siloxane rubber (SKTN grades “B”, “G”, “D” or Siloprene E 18). Then, with constant stirring, 20 kg of zinc oxide and 180 kg of powdered silica are added. After thorough mixing, the mixture is heat-treated to remove moisture. Then the mixture is transferred to the reactor and under the cover of dry nitrogen 2 kg of ethyl silicate and 1.8 kg of diethylaminomethyltriethoxysilane (ADE-3) are fed into the mixture. The resulting mixture was stirred for 1.5-2 hours. Ready sealant is packaged in tubes or cartouches.

The sealant corresponding to the composition of Examples 2-6 is obtained in a similar manner as in Example 1. Only the quantitative and qualitative composition of the sealant is changed.

The product obtained in the examples is a thick pasty mass of light gray color with the characteristics indicated in table 2.

The sealant compositions presented in the examples were tested for compliance with quality indicators using standard methods in accordance with GOST:

1. The tensile strength of the sample in tension was determined using a tensile testing machine brand PM-50 in accordance with GOST 21751-76.

2. The maximum elongation of the standard sample at break was determined in accordance with GOST 21751-76.

3. The tensile strength upon peeling of the sample was determined in accordance with GOST 21981-76.

4. Shore A hardness was determined using a TM meter according to GOST 263-75.

5. The viability of the sealant was determined according to TU 2513-003-50643915-02.

6. The time of complete vulcanization was determined according to TU 2513-003-50643915-02.

7. Oil and gas resistance was determined according to TU 2513-003-50643915-02 and according to GOST 9.030-74 in oil and antifreeze.

8. The operating temperature range was estimated by weight loss in accordance with GOST 19338-90.

table 2 No. of examples Physical and mechanical properties Vitality, hour Full vulcanization time., Hour Oil resistance Operating temperature range, ° С Limit. durable at growth., kgf / cm ² Max Rel elongation.,% The limit of the rest. when exfoliating.,
kgf / cm ² Shore Hardness oil Antifreeze 1 22 120 1,5 58 0.5 eighteen 0.51 0.5 -60 to +300 2 19 110 1.4 52 0.75 twenty 3 1 -60 to +300 3 21 115 1.4 fifty 0.75 twenty 3 1 -60 to +270 4 21 120 1,5 56 0.5 eighteen 0.6 0.5 -60 to +300 5 twenty 110 1.4 54 0.6 eighteen 3 2 -60 to +270 6 21 120 1.4 52 0.75 twenty 2,5 1 -60 to +270 7 17.6 120 1,5 - 5 72 - - -30 to +250

From the data presented in tables 1 and 2, it can be seen that in the specified range of changes in the ratio of components receive sealant with characteristics that exceed the performance of the sealant of the prototype.

Claims (2)

1. Sealant based on low molecular weight siloxane rubber, including zinc oxide, ethyl silicate, diethylaminomethyltriethoxysilane, characterized in that it further comprises powdered silica in the following ratio, wt.h .: Low molecular weight siloxane rubber 100 Zinc Oxide 5-30 Ground silica dust 40-180 Ethyl Silicate 1-3 Diethylaminomethyltriethoxysilane 1-3 2. The sealant according to claim 1, characterized in that it additionally contains chalk of 2-60 wt.h. and / or dolomite 2-95 parts by weight