Law molecular siloxane rubber-based sealing compound

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

 

The invention relates to sealing compositions based on low-molecular siloxane rubber, namely, one-component hermetics, used in the automotive industry for sealing various compounds that require high oil-benzothioate and operated in the temperature range from -50 to +300°C.

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

The composition of the sealing composition:

Compound based on low-molecular

siloxane rubber, wt.% 75-96

Oligomerisation

the viscosity at 20°5-150 mm2/s 4-25

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

Known sealing composition comprising organopolysiloxane, ethyl silicate, carboxylate dialkylamino, 8-oksihinolina used for sealing of sheet gasket materials,such as gasket junction block and heads of internal combustion engines (As, 1992).

The purpose 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:

Organopolysiloxanes, parts by weight 100

Ethyl silicate 2,0-4,0

Carboxymethylcellulose of 0.9 to 3.0

8-Oksihinolina 0,7-2,0

The disadvantage of this sealing composition is non-resistant to solvents, high temperature curing (170°s)time before vulcanization (80-200 hours).

Known sealant, including rubber, zinc oxide, ethyl silicate and the vulcanization accelerator, and optionally containing polymethylsiloxane, and as an accelerator of vulcanization - NN-dimethyl-N-triethoxysilylpropyl (RF patent No. 2188841, 2002), designed for sealing 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:

The rubber (or crasneanscki elastomer,

or polysulfide elastomer) 100

Zinc oxide 100-200

Ethyl silicate 5-16

Polymethylhydrosiloxane 1-1,4

NN-dimethyl-N-triethoxysilylpropyl 2-7

The disadvantage of this sealant is a great time to start vulcanization (3-4 hours) and a great time full of vulcanization (24-48 hours), so you cannot use it when REM is NTE.

The closest in composition is a sealant based on dimethylsiloxane rubber, zinc oxide, ethyl silicate and of a vulcanization accelerator of diethylaminoethylmethacrylate (A.S. No. 456820, 08 D 47108, From 09 To 3110).

This sealant is as follows:

Dimethylsiloxane rubber, 100 parts by weight of

Zinc oxide 100-200

Ethyl silicate 1-10

Diethylaminoethylmethacrylate 2-6

This sealant is water resistant, has satisfactory physical and mechanical properties, and also has good adhesion to the metal surface.

The disadvantage of this sealant is a lower limit of tensile strength, long time before vulcanization (5 hours) and a great time complete cure (72 hours), which does not allow to use it for repairs, a small range of operating temperatures (-30···+250°).

The present invention is the creation of a sealant, vulcanizing when interacting with air moisture and has a higher performance, and lower the cost of its components.

The problem is solved so that the sealant based on low-molecular siloxane rubber containing zinc oxide, ethyl silicate, diethylaminoethylmethacrylate additionally contains quartz powder pulverized during the next aspect] is the solution components parts by weight of:

Low molecular weight siloxane

rubber 100

Zinc oxide 5-30

Quartz powder pulverized 40-180

Ethyl silicate 1-3

Diethylaminoethylmethacrylate 1-3

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

As main components take:

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

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

- diethylaminoethylmethacrylate (AD-3), THE 6.02-573-87;

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

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

- zinc oxide, GOST 202-84;

quartz powder, pulverized, GOST 9077-72.

Sealant is prepared in stages. First mixer prepare a mixture of starting components. Then the mixture is subjected to heat treatment (drying to remove moisture). After heat treatment, the mixture overload in the reactor and in a stream of dry nitrogen add diethylaminoethylmethacrylate and ethyl silicate. In the reactor the mixture is stirred until a homogeneous mass within 1.5-2 hours and Packed in airtight packaging (tubes, cartouches).

To prove the conformity of the composition of the criterion of “industrial applicability” are examples of receiving sealant (table 1).

95


Table 1
Name of the componentStandards download, no examples, parts by weightPrototype

7
 123456 
SCTN “”100---100--
SCTN “G”-100---100-
SCTN “D”--100---100
SILOPREN E18---100---
Zinc oxide20202052030100-200
Chalk-6035--60-
Dolomite--35-95--
Quartz powder pulverized180951808095-
Ethyl silicate2222221-10
Diethylaminoethylmethacrylate1,81,81,81,81,81,82-6

The procedure for obtaining the sealant will look at example 1.

In a special mixer with z-shaped mixing device load 100 kg of low molecular weight siloxane rubber (SCTN grades of “B”, “G”, “D” or Silopren E 18). Then added with constant stirring to 20 kg of zinc oxide and 180 kg of ground quartz dust. After thorough mixing the mixture is subjected to heat treatment in order to remove moisture. The mixture is then reloaded into the reactor and under the guise of dry nitrogen in the mixture fed 2 kg of ethyl silicate and 1.8 kg of diethylaminoethylmethacrylate (AD-3). The resulting mixture was stirred for 1.5-2 hours. Ready sealant packaged in tubes or cartridges.

Sealant that matches the composition of examples 2-6, get a similar manner as in example 1. Change only the quantitative and qualitative composition of the sealant.

Obtained in the examples, the product is a thick pasty mass of light-ser is th color characteristics, listed in table 2.

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

1. The tensile strength of the sample under tension was determined using a bursting machine marks RM-50 in accordance with GOST 21751-76.

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

3. Tensile strength at breaking the sample was determined in accordance with GOST 21981-76.

4. The shore hardness was determined by measuring the TM according to GOST 263-75.

5. Resilient sealant was determined by THE 2513-003-50643915-02.

6. Time complete cure was defined by THE 2513-003-50643915-02.

7. Oil-gasoline was determined by THE 2513-003-50643915-02 and GOST 9.030-74 in oil and antifreeze.

8. Operating temperature range was estimated from the weight loss of in accordance with GOST 19338-90.

Table 2
no examplesPhysico-mechanical propertiesViability, hTime full Vulcans., hourMacrobertsonsOperating range temperature : -p, °
 Limit. stre. when Rast., kgf/cm2/td> The maximum relative. odlin., %Limit etc. when odlaw.,

kgf/cm2
The shore hardness    
       oilAntifreeze 
1221201,5580,5180,510,5-60 to +300
2191101,4520,752031-60 to +300
3211151,4500,752031-60 to +270
4211201,5560,5180,60,5-60 to +300
5201101,4540,61832-60 to +270
6211201,4 520,75202,51-60 to +270
717,61201,5-572---30 to +250

Presented in table 1 and table 2 data shows that in the specified range of variation of the ratio of components receive sealant with characteristics that exceed the performance of the sealant of the prototype.

1. Sealant based on low-molecular siloxane rubber, including zinc oxide, ethyl silicate, diethylaminoethylmethacrylate, characterized in that it additionally contains quartz powder pulverized in the following ratio of components, parts by weight:

Low molecular weight siloxane rubber 100

Zinc oxide 5-30

Quartz powder pulverized 40-180

Ethyl silicate 1-3

Diethylaminoethylmethacrylate 1-3

2. Sealant according to claim 1, characterized in that it also contains chalk 2-60 parts by weight and/or dolomite 2-95 parts by weight of



 

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15 cl, 2 tbl, 11 ex

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