DE3213053A1 - FLUORSILICON RUBBER MATERIAL, METHOD FOR THEIR CURING AND POLYMER - Google Patents

Description

1 River Road
Schenectady, NY / U.SA

Fluorosilicone rubber composition, method for its hardening and

polymer

The invention relates to fluorosilicone rubber compositions, processes for their curing and to fluorosilicone polymers, which are uniquely suitable for use in such masses.

Curable fluorosilicone gum compositions are described in U.S. Patents 4,029,629 and 4,041,010. They are liquids, typically having viscosities in the range of 1 to 200 Pa's (1000 to 200,000 cP) at 25 ^e C, use a vinyl-based polymer terminating in a fluorosilicone content in the range from 5 to 98 mol%. The compositions harden with the aid of a platinum-catalyzed hydrosilylation action, and organic hydroperoxides, alkenyl-containing cyclic polysiloxanes and the like serve as hardening inhibitors.

The base polymers terminated in vinyl groups have been taken as the general formula

Vi- Si -
I.
R.

having described wherein Vi is vinyl, R is selected from alkyl having 1 to 8 carbon atoms or phenyl, R is perfluoroalkyl of 1 to 8 carbon atoms, χ and y are at least 1 and, as mentioned, the concentration of the siloxy unit, y multiplied, varies from 5 to 98 mol%.

The base polymer terminated in vinyl groups is produced on a large scale by copolymerizing cyclic methyl-3,3,3-trifluoropropylsiloxane trimer and octamethyl-cyclotetrasiloxane using an alkali metal hydroxide, preferably potassium hydroxide. The polymerization is of the type of a balance, although the catalysts of complex cations may be used. See, eg, US Patent No. 4,122,247 and 4 157 337. The vinyl end groups resulting from the use of vinyl chain stoppers, such as CH ₂ = CHSi- ( CHj) ₂ -O- | -Si (CH ₃ ) jO -] - _2o Si (CH ₃ ) ₂ CH = CH ₂ or CH ₂ = CHSi (CH ₃ ) ₂ 4-0-Si (CH ₃ ) ₂ -0 -] ₃₈ [Si (CH ₃ ) (CF ₃ CH ₂ CH ₂ ) -O- ^ Si < ^CH 3) 2 CH = CH ₂ and the like in a known manner, and the amount of chain terminator controls the desired viscosity as well known.

Even so, the conventional base polymers that end in vinyl groups provide good mechanical properties when combined and cured appropriately, but they do not all requirements specified for the production of the highest quality electrical connectors.

The conventional base polymers have been found to have a small, unexpected amount of unsaturation on the polymer backbone in addition to the expected, i.e. at the ends. It has also been found that such backbone unsaturation for the development of optimal mechanical properties

shaft is harmful by becoming a densely hardened one Matrix leads, which in turn adversely affects the tensile strength, tear strength and rebound resilience.

Main chain unsaturation arises because as found became the fluorosilicone cyclic trimer used to make the base polymer in the above-mentioned equilibrium process by a side reaction in the presence of alkali metal hydroxide at elevated temperatures a vinyl-containing Trimer of the formula

CF ₃ -CH ₂ -CH ₂ ν, ^CH 3

Si

CF ₃ -CH ₂ -CH ₂ .

CH ₃

Si

Si '

CH ₃

CHοCH = CF-

contains or gives rise to. Typically, the level of such material in the cyclic trimer is never less than 1.5 wt%. It has now been found that using less than conventional amounts of base catalyst and at lower than usual temperatures the content of vinyl by-product - 3,3-difluoropropenyl-like unscite I igung - on; less than 1 and even down to 0 to 0.4 wt .-% can be lowered. If the product containing little vinyl trimer is then used with cyclic tetramer according to conventional Working methods copolymerized becomes a new base polymer with little or no main chain unsaturation obtain. This is uniquely suitable for lo-

Solvent-resistant fluorosilicone rubber-containing compound with the best combination of physical properties.

According to the invention are solvent-resistant, at room temperature Vulcanizable silicone rubber compositions made available, the

(A) a mixture of

(i) a vinyl-containing base polymer of the formula

Vi- Si-

H\

0 h Si-OV I
R.

_{si O} i-J_ _S i- ο -4 — Si — Vi,

I .1 '

CH ₂ CH ₂ R ^J

■ Si-O
ι
CH ₂ CH-R ^

wherein Vi is vinyl, R is alkyl with 1 to 8 carbon atoms or phenyl, R ^{1 is} perfluoroalkyl with 1 to 8 carbon atoms, R ^{2 is} perfluoroalkylidene with 1 to 8 carbon atoms, χ and y are each at least 1, q is O or not more than 0.01 "y is, varying the viscosity of the polymer at 25 ⁰ C of 1 to 200 Pa-s (1000 to 200,000 cP) and the concentration of the siloxy units, y times, taken from 5 varies to 98 mol%, and

(ii) a platinum catalyst, and (B) alone or in a mixture with the base polymer (i),

(iii) a crosslinking polymer selected from

(a) a resin with

and SiO ₂ units, wherein the R / Si ratio is from 1.0 to
2.7 varies,

(b) a resin with SiO ₂ units and RR ³ SiO units, in which the R / Si ratio varies from 1.2 to 2.7,

(c) a polymer of the formula

R I

Η— SI4- O —SI— CH-I R.

SI— 0

CH ₂ CH ₂ R ¹

R I

SI-0-4-Si -H I.

MR

,1

where R and R ^{1 are} as defined above, s is at least 1, t and ζ 0 or a positive integer and the viscosity of the polymer varies ^{from 0.010 to 1 Pa-s (10 to 1000 cP) at 25 ° C} , where the concentration of siloxy units, taken t times, varies from 0 to 75 mol%, and R ^{1 is} alkyl of 1 to 8 carbon atoms or -CH ₂ CHjR ¹ , or a mixture of (a), (b) and ( c) wherein the total weight of (A) and (B) per 100 parts by weight of base polymer (i) comprises 0.1 to 50 parts per million platinum catalyst pr (ii) and 1 to 50 parts crosslinking polymer (iii).

The invention also relates to a process for the formation of a solvent-resistant silicone elastomer under (a) Mixing ingredients (A) and (B), which are as defined above, and (b) allowing the mixture to harden.

The invention also relates to new base polymers which can be used in a unique way for the production of such compositions suit and the formula

Vi—

Si

/ R

CH ₂ CH ₂ R ¹ \ CH ₂ CH-r2

R I

Si

- Vi

where Vi is vinyl, R is alkyl of 1 to 8 carbon atoms

1
or phenyl, R is perfluoroalkyl of 1 to 8 carbon atoms, R ^{2 is} perfluoroalkylidene of 1 to 8 carbon atoms, χ and y are each at least 1 and q is O or not more than 0.01-y, the viscosity of the polymer from 1 to 200 Pa-s (1000 to 200,000 cP) varies at 25 ⁰ C and taken times the concentration of siloxy units y, varies from 5 to 98 mol%.

The platinum catalyst can be a deposit of platinum on a solid support, such as activated carbon or gamma-alumina, or a solubilized platinum catalyst such as chloroplatinic acid, or any of the well known platinum complexes be.

The composition cures to a solvent-resistant at room temperature or at a much greater rate at elevated temperatures Silicone elastomer. Preferably 5 to 100 parts of a filler are incorporated into the mass, in order to impart high tensile strength and elongation to the fully cured silicone elastomer, so that the material has strength properties that are similar to those of hot-vulcanizable ones Silicone rubber compounds are comparable. More preferably, the filler is among flame formed silica and precipitated silica which has been treated with a silicone compound to make it hydrophobic make and the silicone rubber composition with improved physical Properties, especially tensile strength, to be provided. So the filler can with a cyclic polysiloxane or a silyl nitrogen compound as well known in the art and subsequently described

purifies.

The mass can also comprise a hardening inhibitor in order to make it processable long enough at room temperature, what for the particular processing technique in which the compound is used, is desirable. Various accessories can be incorporated into the mass, e.g. additives for heat resistance, such as iron oxide.

In the process of forming the silicone elastomer, the vinyl-containing polymer is incorporated with the filler, the Platinum catalyst optionally mixed with an inhibitor and the heat stabilizing agent in one component. Of the The hydride crosslinker is packaged separately in a second component and this can contain vinyl-containing polymer and filler and the setting inhibitor. When the mass is to be hardened, the two components are simply mixed together and the mass (depending on the amount of inhibitor that is incorporated and the temperature, in which the curing takes place) can cure to a solvent-resistant silicone elastomer.

The above composition makes a solvent-resistant silicone rubber composition Provided with suitable low viscosity properties that are either at room temperature or cured at elevated temperatures if a shorter cure cycle is desired. So can ever depending on the temperature and the amount of inhibitor used, the above mass in the uncured state and with the desired cure in a time that varies anywhere from 1 min to 5 h or more depending on how it's used for low viscosity the processing and manufacturing technique for which the compound is used is desired.

The above base polymer (i) is one of the basic components of the composition according to the invention, where R is an alkyl group.

1 to 8 carbon atoms and phenyl, preferably from an alkyl radical having 1 to 4 carbon atoms such as methyl, ethyl, etc. is selected. The radical R can be any perfluoroalkyl radical having 1 to 8 carbon atoms, but is most preferably perfluoromethyl. In general, χ can vary from 1 to 1000 and y from 1 to 1000. These symbols must be at least 1 and can have any value so that the viscosity of the liquid is generally from 1 to 500 Pa · s (1000 to 500,000 cP) at 25 ^° C., preferably from 1 to 200 Pa · s (1000 to 200,000 cP) at 25 ^° C. Most preferably, the viscosity of the above polymer varies of formula (i) from 20 to 85 Pa-s (20 000 to 8500OcP) at 25 ⁰ C.

Another important limitation of the base polymer (i) is that the alkyl perfluoroalkylethylene-siloxy-substituent units, Taken y times, in the polymer at a concentration generally somewhere between 5 and 98 mol% and preferably between 26 and 29 mol% must be present.

The base polymers are made in accordance with well known procedures, see, for example, U.S. Patent 4,29,629. Conveniently becomes a mixture of a cyclic alkyl or phenylperfluoropropylsiloxane trimers and octamethylcyclotetrasiloxane with an alkali metal hydroxide, preferably potassium hydroxide, brought into balance. The polymerization can also take place in the presence of a complex cation catalyst. In each However, if so, the fluorosilicone trimer must be no more than 1.0 wt%, preferably 0 to 0.4 wt%, of any vinyl containing Trimer by-product, e.g., of the type represented by the formula above.

To control the final viscosity of the base polymer, contains the mixture divinyl chain terminators according to standard practice.

^{The mixture is heated to over 100 °} C. in the presence of the catalyst for 5 to 20 hours until equilibrium is reached.

Then it is cooled and the catalyst is neutralized, e.g. with tris (2-chloroethyl) phosphite or other standard materials. The mixture is then devolatilized to remove cyclic compounds.

Until it is ready for use, the base polymer is catalyst mixed with the crosslinking agent, as known in the art, is kept separate. The catalyst can be in the base polymer, the crosslinker can be dispersed in a second portion of the base polymer, but too early contact between them triggers premature hardening. The crosslinker can be any of the known hydride-containing resins or hydrogenpolysiloxane polymers or their mixtures be. They are made by techniques such as those shown in the above-mentioned US Pat. No. 4,029,629, the disclosure of which is disclosed is incorporated into the present application by this reference for unnecessary more detailed descriptions to avoid.

The term “platinum catalyst” defined here means not only platinum metal deposited on a solid support, but also platinum in any form and in particular in the form of a platinum complex. These platinum complex catalysts are preferred because the platinum is more soluble in the reacting components and, depending on the platinum complex catalyst used, tends to result in a faster reaction rate. Such a platinum compound catalyst can be, for example, chloroplatinic acid. Preferred platinum catalysts are those platinum compound catalysts which are soluble in the reaction mixture according to the invention. The platinum compound can be selected from those of the formula (PtCl ₂ olefin) ₃ and H (PtCl ₃ olefin) as described in US Pat. No. 3,159,601. The olefin represented in the above two formulas is preferably alkenylene having 2 to 8 carbon atoms, cycloalkenylene having 5 to 7 carbon atoms or styrene. Special olefins that can be used in the above formulas are ethylene, propylene, the various isomers of butylene, octylene, cyclopentene,

Cyclohexene, cycloheptene, etc.

Another platinum catalyst is the platinum chloride-cyclopropane complex (PtCl “C Hj, as described in US Pat. No. 3,159,522 is.

Another platinum catalyst arises from chloroplatinic acid with up to 2 mol / g platinum of a representative from the class of Alcohols, ethers, aldehydes and their mixtures as described in US Pat. No. 3,220,972.

The above ingredients form solvent resistant silicone rubber. However, about tensile strength and toughness To increase the cured silicone elastomer, a filler is preferably incorporated. Examples of the numerous Usable fillers are titanium dioxide, lithopone, zinc oxide, calcium silicate, silica gel airgel, barium oxide, diatomaceous earth, Calcium carbonate, silicon dioxide formed in the flame, silazane-treated silicon dioxide, precipitated silicon dioxide, Glass fibers, magnesium oxide, chromium oxide, zirconium oxide, aluminum oxide, <* - quartz, baked clay, asbestos, carbon, Graphite, cork, cotton, synthetic fibers, etc. It has been found that silicon dioxide formed in the flame and precipitated Silica is the best filler for the composition of the invention with a view to optimizing tensile strength and toughness of the hardened masses and are the most advantageous, and optimum results are obtained with silicon dioxide formed in the flame, that has been treated. So the silicon dioxide fillers, e.g. as disclosed in U.S. Patent No. 2,938,009, treated with cyclic polysiloxanes. Silazane treated fillers as disclosed in U.S. Patent 3,635 and 3,847,848 are preferred.

When making the mass, part A is conveniently made, by taking all or part of the base polymer (i) and, if desired, filler and platinum catalyst

(ii) is added. Part B is prepared by using the crosslinker (iii) alone, but more preferably using a portion of the base polymer and the crosslinker (iii) and a useful life extending agent, e.g. 100 to 10,000 parts / million of a vinyl unsaturated cyclic polysiloxane, Dialkyl maleate, dialkyl maleic acid imide, a hydroperoxide or the like is added. The latter promotes the useful life, because after mixing parts A and B, depending on the temperature, the masses ^{harden within hours at 25 °} C. to a few minutes at 100 ^° C. or above. These factors are well known to the person skilled in the art, only the amounts of material specified above and in the claims needing to be taken into account.

The following examples illustrate the compounds, compositions and procedures according to the invention. They only serve to illustrate and in no way limit the claims.

Examples 1-3

Base polymers ending in vinyl groups with 28 mol% of 3,3,3-trifluoropropylmethylsiloxy units and 72 mole percent dimethylsiloxy units are prepared according to the following general procedure manufactured:

A clean, dry container is filled with 24 grams of methyl-3,3,3-trifluoropropylsiloxane cyclic trimer and 300 g octamethylcyclotetrasiloxane (including 50 g excess to dry) loaded. The container is heated to 120 C and the excess cyclic tetramer flushed with nitrogen to azeotropically lower the moisture content to less than 10 ppm water. Then 4.5 to 6 parts of a chain terminator are used the formula

₂ = CHSi (CH ₃ ) ₂ -C ~ f "Si (CH ₃ ) ₂ 0 -} - ₂₀ Si (CH ₃ ) ₂ CH =

added per 100 parts of the cyclic trimer, which is sufficient to ultimately give a polymer freed from volatile constituents and having a viscosity in the range from 20 to 80 Pa · s (20,000 to 80,000 cP) at 25 ^° C. A catalyst is prepared with 0.013 g of potassium hydroxide colloidally distributed in the cyclic tetramer (ground with high shear mixing). The average particle size is 25 to 100 .mu.m and is dried over a 4A ° molecular sieve. The catalyst is added and the mixture reacts exothermically. After the oxot.hormon reaction has subsided, the container temperature is increased to 160 ° C. and held for 6 h. The catalyst is neutralized by adding tris (2-chloroethyl) phosphite and the polymer is freed from volatile components to less than 2.5% by weight. Has the clear polymer, usually about 420 g (80% recovered yield) of a density of about 1,101 at 25 ⁰ C.

Three polymers with different viscosities and two different Main chain unsaturations arise from two approaches of the cyclic perfluoroalkyl trimer and with two different ones Quantities of the chain terminating agent prepared. They have the following general formula:

H ₂ C - CH - Si - I - Si - OW - Si O - # Si - O - I Si - CH - CH ₂

CH ₃ \ CH ₃ J \ CH ₂ CH ₂ CFt / IcH ₂ CH = CF ₂ / CH ₃

Base polymer olefin compound viscosity,

Example χ y q in the trimer,% Pa-s (cP) at

25 ° C 000) 85 (85 400) 26.4 (26 000) 52 (52

1 72 27.94 0.056 0.2

2 72 27.94 0.056 0.2

3 72 27.80 0.196 0.7

Examples 4-6

Three batches of curable compositions are made from the base polymer of Examples 1-3 according to the following general procedure manufactured:

Part A

In a batter mixer are placed 100 parts of the base polymer, then 15 parts of a first silazane-treated silica filler and 5 parts of a second silazane-treated silica filler. The first silica filler is a flame formed silica that is first treated with 1,1,3,3,5,5,7,7-octamethylcyclotetrasiloxane, devolatilized, then treated with hexamethyldisilazane. The second silica filler is a precipitated silica that is first treated with the same cyclic siloxane, devolatilized, then treated with hexamethyldisilazane. After the mixture has become uniform, it is ^{hot mixed for two hours at 120 °} C. under a nitrogen gas atmosphere. It is cooled to below 50 ⁰ C, and then 0.08 part of a platinum catalyst are chloroplatinic acid, complexed with 2 mol / g-atom of platinum of an alcohol (U.S. Patent 3,220,972) was added.

part B

It is manufactured in accordance with Part A, with the exception of that 2.1 parts of a branched hydride of the general

formula

H = 0.8-1.2%

and 0.09 part of diallyl maleate is added in place of the platinum catalyst after hot mixing. The branched hydride is the hydrolysis product of 4 moles of dimethylchlorosilane and one mole of ethyl orthosilicate.

Rubber sheets with ASTM dimensions are made by mixing Part A and Part B in a ratio of 1: 1 and curing in the mold for 1 hour at 150 ^° C (300 ^° F). The panel is then cured for 8 hours at 204 ^° C (400 ^° F) and examined for physical properties. The results of the hardening of the respective recipes are as follows:

Example base polymer hardness of Ex.

Shore A tensile strength elongation, tear

1 2 3

44 46 46

(psi)

55.2 (785) 56.7 (807) 50.7 (721)

470
400
360

strength

(pi) kg / cm (122) 21.8 (102) 18.3 (89) 15.9

It becomes high-strength, solvent-resistant fluorosilicone rubber compounds obtain.

The aforementioned patents are incorporated into the present application by reference. It is obvious, that numerous modifications will be apparent to those skilled in the art in light of the above. All such modifications are in the intended scope of the claims.

Claims (12)

Claims 1. Solvent-resistant, room temperature vulcanizable silicone rubber composition which (A) a mixture of (i) a vinyl-containing base polymer of the formula Vi R ι Si 0 I-Si-OV \ ι Si-ι CH ₂ CH ₂ R ¹ • Si- 0
CH ₂ CH-R ² R ι Si —Vl, wherein Vi is vinyl, R is alkyl having 1 to 8 carbon atoms or 1 Phenyl, R perfluoroalkyl with 1 to 8 carbon atoms, R Is perfluoroalkylidene with 1 to 8 carbon atoms, χ and y are each at least 1, q is O or not more than 0.01 * y, the viscosity of the polymer at 25 ⁰ C from 1 to 200 Pa-s (1,000 to 200,000 cP) varies and the concentration of the siloxy units, taken y times, varies from 5 to 98 mol%, and (ii) a platinum catalyst, and (B) alone or in a mixture with the base polymer (i), (iii) a crosslinking polymer selected from (a) a resin with , 5 and SiO ₂ units, in which the R / Si ratio varies from 1.0 to 2.7, (b) a resin with SiO ₂ units and RR ³ SiO units, in which the R / Si ratio varies from 1.2 to 2.7, (c) a polymer of the formula R / H - Sl - 0 - Si where R and R are as defined above, s is at least 1, t and ζ can be 0 or a positive integer and the viscosity of the polymer ^{varies from 0.010 to 1 Pa «s (10 to 1000 cP) at 25 °} C, where the concentration of the siloxy units taken t times vary from 0-75 mol%, and R ^{3 is} alkyl with 1 to 8 carbon atoms or -CH ₂ CH ₂ R, or a mixture of (a), (b) and (c) wherein the total weight of (A) and (B) per 100 parts by weight of base polymer (i) comprises 0.1 to 50 parts per million of platinum catalyst (ii) and 1 to 50 parts of crosslinking polymer (iii). 2. Composition according to claim 1, which further comprises 5 to 100 parts of a filler, selected from titanium dioxide, lithopone, zinc oxide, zirconium silicate, silicon dioxide airgel, iron oxide, diatomaceous earth, calcium carbonate, silicon dioxide formed in the flame, precipitated silicon dioxide, glass fibers, magnesium oxide, Chromium oxide, zirconium oxide, aluminum oxide, oC quartz, baked clay, asbestos, carbon, graphite, cork, cotton and synthetic fibers. 3. Composition according to claim 2, the filler of which in the flame formed silicon dioxide, precipitated silicon dioxide, respectively treated with a silicone compound, or a mixture thereof. 4. The composition of claim 1, wherein R is methyl, R CF. ,, R = CF ₂ and R ³ -CH ₂ CH ₂ CF ₃ . 5. Composition according to claim 3, the silicone compound of which is silazane. 6. The composition of claim 1, the platinum catalyst of which is a platinum complex with an alcohol. 7. The composition of claim 1 containing 100 to 10,000 parts per million of a curing inhibitor selected from an organic one Hydroperoxide, dialkyl maleate or dialkyl maleic acid imide. -A- 8. A composition according to claim 7, the hardening inhibitor of which is dialkyl maleate is. 9. Composition according to claim 1, the concentration of which units y times are poor in grain, varies from 26 to 29 mol% in the base polymer (i). 10. Composition according to claim 1, in which the viscosity of the polymer (i) is in the range from 20 to 85 Pa-s (20,000 to 85,000 cP) at 25 ^° C. 11. Method of forming a solvent resistant Silicone elastomers, characterized by (a) mixing component (A) and component (B) according to claim 1 and (b) allowing the mixture to harden. 12. Vinyl-containing polymer of the formula Vi— R I Si Si— 0 CH ₂ CH ₂ R ¹ • Si \ f CH ₂ CH-R ² Si-Vi, wherein Vi is vinyl, R is alkyl having 1 to 8 carbon atoms or 1 2 Phenyl, R is perfluoroalkyl with 1 to 8 carbon atoms, R is perfluoroalkylidene with 1 to 8 carbon atoms, χ and y are each at least 1 and q is 0 or not more than 0.01-y, the viscosity of the polymer from 1 to 200 Pa- s (1000 to 200,000 cP) varies at 25 ⁰ C and the concentration of the siloxy units, which are taken by y varies from 5-98 mole%.