DE2307050B2 - Thermosetting organopolysiloxane molding compound - Google Patents

Description

The invention relates to thermosetting organopolysiloxane molding compositions containing SiO ₂ fillers, mixtures of flame retardants and curing agents, for the production of elastomers that are flame-resistant or self-extinguishing after the ignition condition has been removed, and also high elasticity or ductility with little permanent distortion after removal of the Exhibit load.

Silicone elastomers are widely used, but have the disadvantage of having the property of Flammability. In order to make them incombustible, it is known, for example, from US Pat. No. 2,891,033 a silicone compound containing methylphenylpolysiloxane and a filler, a finely divided one containing copper Adding substance. From US-PS 31 54 515 flame-retardant polysiloxane elastomers are known from Dimethylpolysiloxane, organic silicates, chlorinated polyphenyl, copper-containing substances, fillers and monocarboxylic metal salts are obtained. According to US-PS 35 14 424, the incombustibility by adding a platinum-containing substance to a silicone compound, the ordinary organopolysiloxane and contains a filler. However, these known silicone elastomers do not meet the requirements in terms of self-extinguishing and elastic deformability. Especially those in the first place said elastomers with a copper-containing substance are not obtained uncolored, so that they for Coating wires with different colored coatings are not suitable. The last one named elastomers with a content of a platinum-containing substance is the heat resistance, so one of the characteristic properties of a silicone elastomer, and also the flame retardancy unsatisfactory.

It is also known to add flame retardants such as antimony oxide to various molding materials. However, the addition of such known flame retardants to silicone compositions would result in end products supply which no longer have the desired typical properties of the silicone elastomers.

The invention is based on the object of a heat-curable, flame-retardant organopolysiloxane molding compound to create which fittings with excellent mechanical strength and heat resistance supplies.

This object is achieved by a molding compound of the type specified at the beginning, which has the properties described in claim 1 Has specified composition.

The invention is explained below.

It has been found that when a mass containing the above ingredients is heated and vulcanized the same in the presence of a known crosslinking agent the mass as usual hot vulcanizable Silicone rubber into an elastomer excellent in heat resistance and tear resistance is converted and, when this elastomer is formed into a tape, held and vertical the lower end is exposed to fire, it burns, but after the fire is removed from itself disappears, and that the disadvantage of permanent distortion when using certain types of Crosslinking agents occurs, is largely avoided.

An organopolysiloxane contained as the component (a) in the present invention is usually used as the main component of the matrix and is a straight-chain polysiloxane having the following unit formula

R "SiO ₄ -"

wherein R is a substituted or unsubstituted monovalent hydrocarbon radical, namely a methyl,

4 »ethyl, propyl or phenyl, halogen-substituted hydrocarbon group, vinyl or allyl group or the like, and a is a number from 1.90 to 2.05.

For the purposes of the invention, component (a) should have a viscosity of over 1,000,000 cSt (measured at 25 ° C.), particularly preferably over 1,000,000 cSt. This constituent can _{contain CH 3} SiOl ₅ units in its structure, provided that their amount is small, namely less than 5 mol%. In addition, this component can be hydroxyl or trimethylsilyl end groups

w have.

As constituent (b), finely divided silicon dioxide filler, known usually for silicone rubbers fillers used, such as fumed silicon dioxide, precipitated silicon dioxide, quartz powder and kieselguhr,

■ 5 ^r ) can be used. The filler (b) is preferably so finely divided that at least 90% have a grain size below 50 μm (microns). If too large an amount of the component (b) is added, the physical properties of the compound will be reduced by vulcanizing the composition

bo obtained elastomers deteriorated.

If the amount of the component (b) is too small, the mechanical properties such as tensile strength, of the elastomer obtained. Accordingly, according to the invention, component (b) in

b5 in an amount of 20 to 200 parts by weight per 100 parts by weight of the component (a), as stated above.
That contained according to the invention as component (c)

finely divided manganese carbonate, in combination with component (d) mentioned below, gives the Elastomers have excellent self-extinguishing and flame-retardant properties, as it is when heated Develops carbon dioxide and acts catalytically. It has been found that this component (c) also the elastic deformation of the products obtained greatly improved. As in the case of component (b), this is Component (c) is preferably so finely divided that at least 90% of it has a particle size below ι ο 50 μΐη (microns). To such a high flame resistance and high elasticity without deteriorating characteristic properties of the elastomers obtained, this component (c) must be in an amount of 5 to 100 parts by weight per 100 parts by weight of the r, Component (a) are used.

If one only considers the function of the evolution of carbon dioxide gas, one might assume that that calcium carbonate, zinc carbonate, cobalt carbonate, sodium carbonate and the like for the purpose of Invention are similarly effective. However, by adding these carbonates, the self-extinguishing effect in Elastomers are not obtained, and in addition, these carbonates have an adverse influence on the heat resistance of silicone elastomers can therefore not be used for the purposes according to the invention to be used.

The component (d) is required to the molding composition in combination with the above component (c) to give the self-extinguishing property. As a platinum compound usable as component (d) are called platinum chloride or complexes of platinum chloride with alcohols, ethers, aldehydes, etc. It is also possible to use as component (d) products that contain platinum powder on a carrier, such as aluminum oxide, Silica gel or asbestos.

In order to achieve the purpose of the self-extinguishing property advantageously, according to the invention as Ingredient (d) amount added 5 to 1000 ppm (parts per million) calculated as platinum metals, preferably 10 to 100 ppm based on 100 parts by weight of the component (a).

The molding composition according to the invention can be processed into various shaped articles by molding, heating and vulcanization. Known crosslinking agents (vulcanizing agents), such as organic peroxides or organohydrogen-polysiloxanes, are preferably used to vulcanize the molding compositions according to the invention with heating. Examples of organic peroxides are benzoyl peroxide, tert-butyl perbenzoate, 2,4-dichlorobenzoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide or monochlorobenzoyl peroxide; Examples of the organohydrogenpolysiloxanes are methylhydrogenpolysiloxanes with at least two Si —Η bonds in one molecule. As in the case of the organic peroxide, they are preferably used in an amount of 0.3 to 6 parts by weight per 100 parts by weight of the component (a). Furthermore, in the case of using organohydrogenpolysiloxane, its amount should be chosen so that the number of = Si-H bonds is 0.8 to 1.5 per = Si-CH = CH ₂ bond in component (a), which is shown in in this case should contain at least two bonds = Si —CH = CH ₂ in an average molecule. t> 5

The molding composition according to the invention can be produced by adding the mentioned components (a) to (d) mixed and the mixture is homogenized by kneading on rollers or in a similar manner. Njch Such a mass may require the aforementioned organic peroxide or organohydrogenpolysiloxane and a low molecular organic silicone compound such as diphenylsilanediol, diphenylmethylsilanol or alkoxysilane, pigments and other additives are mixed in.

^{If the molding compound formed in this way is heated to about 100 to about 350 °} C. under elevated pressure or atmospheric pressure for several seconds to 1 h and, if necessary, is subjected to post-heating, it becomes a molded product, e.g. B. a film, a tape, a coated electric wire, vulcanized, which shows excellent properties in various respects such as heat resistance, self-extinguishing property and elasticity.

The invention is further illustrated by the following examples in which all "parts" are by weight relate. The values for hardness, elongation, tensile strength and permanent distortion are indicated by corresponding Measurements obtained according to the methods of Japanese Industrial Standard JIS K 6301. The extinction property was determined by the following method:

A sample of the mass was heated under pressure and vulcanized into a sheet with a thickness of 2 mm. Test pieces with a width of 0.5 cm and a length of 20 cm were cut from this film. That Test piece was attached almost vertically, and the flame an alcohol lamp was immediately with placed in contact with the lower part of the specimen for 15 seconds to ignite it. Then became the alcohol lamp was removed from the specimen and the time until the flame was extinguished was measured. the Extinguishing property is expressed as the time (see) that elapses before it is extinguished.

example 1

A matrix consisting of 100 parts of an organopolysiloxane with a content of 99.9 mol% of (CH ₃ J ₂ SiO units and 0.1 mol% of CH ₃ (CH ₂ = CH) SiO units, 25 parts fumed silicon dioxide, 20 parts of powdered manganese carbonate (chemical purity: 1st class), 2.5 parts of diphenylsilanediol as a silicon dioxide dispersant, 0.05 part of a solution of 2% (calculated as platinum metal) platinum chloride in butanol, 50 parts of quartz powder with a particle size of about 5 μίτι and 5 parts of titanium oxide of anatase type was mixed homogeneously to two rollers, and the mixed mass is heated for one hour at 150 ⁰ C. the mass thus obtained for each 100 parts of 0.7 parts of a silicone oil paste with a content of 50% benzoyl peroxide mixed in homogeneously by means of the two rollers mentioned, in order to obtain a molding compound.

The molding composition was vulcanized under 30 kgf / cm ² at 12O ⁰ C for 10 minutes to obtain a film which has been post-cured for 2 hours at 150 ° C. The physical properties of the vulcanized film obtained were measured (Table 1). For comparison, a vulcanized sheet was produced in the same manner as above except that powdered manganese carbonate was not used. The results of the measurements on this comparative product are also shown in Table 1.

Table 1

Inventive Comparison product product Hardness (JIS) 55 50 Strain (%) 300 320 Tensile strength (kg / cm ² ) 73 75 Flame extinguishing (see) 3 25th (at the first time) Flame extinguishing (see) 0 33 (the second time)*)

10

*) After completion of the flame extinguishing test, the The flame of the alcohol lamp was brought into contact with the test piece again for 15 seconds and the flame extinguishing property determined again.

Example 2

A molding compound was prepared in the same manner as in Example 1, except that instead of 0.7 part of Silicone oil paste with 50% benzoyl peroxide content here

Table 2

20 0.2 part of an organohydrogenpolysiloxane, consisting of 2 moles of (CH ₃ ) 2 (H) SiOo, 5 units and 1 mole of SiO ₂ units, was used. The mass was formed into a film and ^{vulcanized in an oven at 150 °} C. for 30 minutes. In the flame extinguishing test, the vulcanized film obtained in this way went out after only 6 seconds, while a comparison product made without the use of manganese carbonate only went out after 35 seconds.

Example 3

100 parts of an organopolysiloxane, consisting of 97.85 mol% (CH ₃ ) ₂ Si0 units, 2 mol% (C ₆ H ₅ ) 2SiO units and 1.15 mol%

CH ₃ (CH ₂ = CH) SiO units, 3 parts of methyltriethoxysilane 45 parts of fumed silicon dioxide and 4 parts of diphenylsilanediol were mixed homogeneously on two rollers, and the mixture was ^{heated to 150 °} C. for 3 hours. The ingredients shown in Table 2 were mixed into the composition thus formed to obtain a molding composition.

From this molding compound, a film was produced in the same way as in Example 1, its flame-extinguishing properties are listed in Table 2.

Sample no.

Dimensions

(Parts)

Manganese carbonate

(Parts)

Quartz powder: r

(Parts of) platinum chloride

2% solution
(Parts)

Benzoyl peroxide

50% paste
(Parts)

Flame extinguishing

(lake)

3-1 (comparison) 100 0 3-2 (invention) 100 15th 3-3 (comparison) 100 0 3-4 (invention) 100 30th 3-5 (invention) 100 40 3-6 (comparison) 100 0 Example 4

Physical Properties

■ Sample 3-Γ
(Comparison)

Sample 3-2 '
(Invention)

Hardness (JIS) 57 62 Strain (%) 350 320 Tensile strength (kg / cm ² ) 83 85 Persistent distortion 50 18th Flame extinguishing (see) 30th 3

Molding compositions (samples 3-and 3-2 ') were prepared in the same way as in Example 3 from the mixtures of samples 3-1 and 3-2 of Example 3, with only 1.3% 2, instead of the benzoyl peroxide 4-dichlorobenzoyl peroxide was used, which shows the disadvantage of increasing the permanent distortion in elastomers. These molding compositions were kept under 30 kgf / cm ² at 120 ° C. for 10 minutes to produce sheets of 2 mm thick and other sheets of 12 mm thick. The latter were used to measure the permanent distortion.

These films and sheets were post-cured for a further 4 hrs. At 200 ⁰ C. The measurement of their physical properties gave the values given in Table 3.

Table 3

0.1

0.1

0.05

0.05

0.05

0.1

1.0
1.0
1.0
1.1
1.2
1.0

35
2

30th
0
0

60

60

65

45

50

55 The percentage of permanent distortion is determined by -, χ 100, where A is the original

Thickness of the material and B is the thickness of its part that does not recover after the stress is released.

Example 5

100 parts of a dimethylpolysiloxane consisting of
(CH ₃ ) ₂ SiO units,

30 parts of precipitated silicon dioxide, 5 parts of methyltrimethoxysilane, 30 parts of powdered manganese carbonate, 0.1 part of a solution of 2% (calculated as platinum metal) platinum chloride in 2-ethylhexanol and 3 parts of a paste containing 50% benzoyl peroxide were mixed homogeneously on two rollers to to obtain a molding compound. This was molded at 12O ⁰ C under pressure in order to obtain a sheet of 2 mm thickness. The film was post-cured 4 hrs. At 150 ⁰ C. The vulcanized film obtained was subjected to the above flame test. It was found that it did not inflame at all.

comparison

For comparison, the procedure of Example 1 was repeated except that the powdered manganese carbonate was used

has been replaced by sodium carbonate, calcium carbonate or zinc carbonate. The results are in the shown in the table below. The sample slides were

Table 4

heated to 250 ° C for a further 24 hours, whereupon its hardness, Elongation and tensile strength were determined. The results are also given in the table.

Manganese carbonate

sodium

Calcium carbonate

Zinc carbonate

Hardness (JIS) 55 no good 57 53 Strain (%) 300 Foil was 295 330 Tensile strength (kg / cm ² ) 73 cmaiicn 77 56 Flame extinguishing (see) at the first time 3 burns down 5 the second time 0 - 35 After 24 hr. At 250o C ⁰ Hardness (JIS) 57 60 75 Strain (%) 220 170 90 Tensile strength (kg / cm ² ) 63 66 30th

It was also observed that the zinc carbonate 25 noted during their heat resistance

containing film, which initially has an excellent poor and the permanent distortion about 3 times se

Flame quenching showed this property rapidly lost, much as the sheet containing manganese carbonate

after being lit several times was.

Claims (1)

Claim: Thermosetting organopolysiloxane molding compounds containing SiO ₂ fillers, mixtures of flame retardants and curing agents, characterized in that they contain a) 100 parts by weight of an organopolysiloxane of the general formula R _o Si0 ₄ _ _u where R is a substituted or unsubstituted monovalent hydrocarbon radical and a is a number from 1.90 to 2.05, b) 20 to 200 _{parts by weight of a finely divided SiO 2} filler and as a flame retardant c) 5 to 100 parts by weight of a manganese carbonate and d) 5 to 1000 ppm (parts per million), based on the weight of component a), of platinum or a platinum compound containing this amount of platinum, and hardening agent (e).