JPS6353229B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to platinum-catalyzed SiH-olefin silicone compositions that utilize addition cure reactions, and more particularly to improved methods for formulating such silicone rubber products to control the cure of catalyst-containing silicone compounds. With the present invention,
The silicone compounder or processor can selectively control the cure rate, allowing greater control and flexibility during processing. In addition, the present invention also provides silicone rubber products made by the method using the modified cure techniques disclosed herein. The silicone rubber compositions disclosed in U.S. Pat. No. 4,061,609 to Bobear (published December 6, 1977) have been useful and commercially successful, and have gained wide acceptance in the silicone industry.
This patent specification is considered to be a document related to the present invention. Bobair has discovered that by using suitable inhibitors to inhibit the platinum catalyzed curing reaction, some of the major drawbacks of conventional silicone rubber compositions can be completely eliminated. SiH containing platinum catalyst
- Olefin compositions were well known in the art.
Such compositions are generally based on vinyl-containing polysiloxane materials containing treated or untreated fillers and hydrogen-containing polysiloxanes along with platinum catalysts. The platinum catalyst is supported on a solid support, e.g.
- It can be solid platinum metal supported on alumina or a solubilized platinum complex. The usual procedure is to package the vinyl polysiloxane, filler and platinum catalyst in one package and the hydrogen-containing polysiloxane in a second package. A processor or other user of this material can produce a cured silicone elastomer by mixing two packages in defined proportions, molding the mixed composition into the desired shape, and holding it at room temperature for a sufficient period of time. Or cure at high temperature for a relatively short time. The above-described compositions are usually sold as two-component or two-part systems and are commonly referred to as room temperature curable silicone rubber compositions, and more particularly as room temperature curable platinum catalyzed SiH-olefin silicone rubber compositions. Compositions of this type can be cured at different rates depending on temperature. For example, at room temperature it takes 1 to 12 hours for the composition to cure;
At high temperatures, such as 100-200°C, the composition cures in seconds or minutes. Compositions of this type begin to harden immediately upon mixing the two components together, and typically become hard or at least semi-solid within about an hour, even at room temperature. Therefore, in conventional compositions, the curing of the composition is delayed for at least 12 hours when the two components are mixed together to allow the composition to be processed into the desired shape before the composition cures. It is desirable to incorporate an inhibitor that causes It is desirable to have as long a pot life as possible after the two components are mixed together and before the composition has cured to the point where it can no longer be molded. The function of the inhibitor is to prolong the pot life of the composition before curing at elevated temperatures and to provide a shelf-stable product. The inhibitor needs to provide a suitable pot life and not interfere with or diminish in any way the final cure and properties of the composition or silicone elastomer. Among the conventional inhibitors, acetylene-functional organic polymers and monomers, such as those shown in Kookootsedes, US Pat. No. 3,445,420, are well known. These inhibitors are ultimately less desirable because the acetylenic group-containing compound must be sealed in an airtight container. The reason is that upon exposure to the atmosphere or leakage to the atmosphere, the acetylenic compound evaporates, thereby reducing its inhibition properties. This adds another drawback in that conventional platinum catalyst-containing SiH-olefin compositions do not otherwise need to be packaged in airtight containers. In this context, Bobair has discovered a group of hydroperoxy group-containing inhibitors that are highly effective and can overcome many of the drawbacks of the prior art. As previously mentioned, Bovea's silicone rubber compositions have been successful in the marketplace and have provided useful silicone rubber products molded from silicone rubber. Bobea is
In addition to eliminating the need for explosive acetylenic compounds that require careful manufacturing procedures to manufacture and use, we have succeeded in providing an inhibitor with a higher effective inhibition rate. Conventional platinum-catalyzed SiH-olefin compositions typically consist of polysiloxane polymers having a viscosity of about 1,000 to 500,000 centipoise at 25°C;
Such polymers can therefore be operated or processed at more efficient rates than are possible with higher viscosity polymers. In other words, the low viscosity polymer also serves the additional purpose of helping provide additional pot life. Bovea used very effective inhibitors, so
It was possible to provide a high viscosity platinum catalyst-containing SiH-olefin composition with a viscosity ranging from 1 x ¹⁰⁶ to 200 x ¹⁰⁶ centipoise at 25°C. Not only did these compositions remain ready for processing or use, but the final products exhibited very satisfactory high tensile strength. These compositions have opened up vast new markets and applications for platinum-catalyzed SiH-olefin silicone rubber compositions of this type. A difficult problem arose in developing such a high viscosity platinum catalyst containing SiH-olefin composition. This is because, after mixing the two components together, the composition usually has to be processed on a roll mill or other equipment and therefore requires a long pot life of at least 12 hours. In the past, when using such high viscosity materials, there was a risk that some of the material would harden just on the roll during contact and mixing of the two components. This has made molding into products extremely difficult. The composition provided by Bovea eliminated many of these problems. The present invention provides cure control properties by adding silanol-containing materials to platinum-catalyzed silicone compounds. Silanol groups can be found in a variety of materials and are represented by hydroxyl groups bonded directly to silicon atoms. These silanol groups can be found in certain low molecular weight siloxane fluids that may be chain-terminated with silanols, or can also be found on the surface of heat-treated silica or fumed silica particles. Prior to the present invention, it could not have been foreseen that these materials would serve as the basis for controlled cure methods.
In fact, these materials have previously been used for very different purposes. Silanol-terminated polysiloxane fluids have sometimes been used as processing aids to improve the rheological properties and viscoelastic properties of silicone compounds during processing. Fumed silicas, such as Cab-O-Sil and Aerosil, on the other hand, are colloidal silicas that have often been used as thickeners or thixotropic agents or reinforcing agents or fillers for silicone rubbers. In fact, prior to this invention, silicone rubber processors believed that when small amounts of these silanol-containing materials were added, the excess -SiOH groups reacted with -SiH in the presence of platinum to form siloxane bonds and release hydrogen. One would have expected that this would result in a more tightly crosslinked and harder final product. The method of controlling cure of the present invention is distinct from the disclosure of the Bobair patent regarding cure inhibition.
Bobair found that the presence of hydroperoxy groups was effective in inhibiting addition cure reactions in platinum-catalyzed silicone rubbers. By introducing an effective amount of hydroperoxy-containing material, it was possible to obtain a shelf-stable product that could be processed for more than one year. Therefore, the inhibitor is designed to eliminate catalytic activity until it is desired to perform curing at elevated temperatures. Cure modifiers serve a fundamentally different purpose; they are not intended to act like inhibitors to produce storage-stable compounds. Cure modifiers are added in small amounts sufficient to affect the curing of the catalyst-containing silicone compound, regardless of whether the catalyst-containing silicone compound contains an inhibitor. Inhibitors are effective for one year, whereas modulators can be effective for minutes to days. Such silanol cure modifiers are essential for silicone rubber processors who are processing catalyst-containing compounds in molding, extruder, or injection molding machines to ensure that the compounds can be processed until they are desired to begin curing. It is designed to provide sufficient flexibility when Additionally, the present invention provides flexibility for processors wishing to vary the cure rate of silicone compound systems, thereby allowing for various types of processing, such as extrusion through hot air tunnels or steam autoclaves, compaction, transfusion, etc. Facilitates molding with a molding machine or an injection molding machine. The flexibility afforded by the present invention with the opportunity to vary cure rates can be demonstrated by considering various silicone rubber processing techniques. When a catalyst-containing composition is processed in an extrusion device and then directed to a hot air, vulcanization tunnel (or zone), it is desirable that curing of the material occur relatively quickly. That is, best results are obtained if the composition begins to cure immediately upon exposure to the hot air vulcanization zone. However, when hot molding techniques are used, such as compression molding and injection molding, a slower curing is necessary in order for the rubber material to first assume the shape of the molding device before the curing reaction begins. The present invention provides a system for formulating addition cure silicone rubber compositions that allows the rate of cure of the product to be processed to be controlled. The main component is a silicone-based polymer compound, which contains 100 parts by weight of the following formula: vinyl-containing linear polysiloxanes or blends thereof. Here, R in the formula has 1 to 1 carbon atoms.
8 alkyl groups, vinyl groups, phenyl groups, fluoroalkyl groups having 3 to 10 carbon atoms, and mixtures thereof, the vinyl unsaturation in the polymer is 0.005 mol% or more, and a is
It is 1.98-2.01. Preferably, the vinyl-containing polysiloxane has the following formula: It has a viscosity of 1,000 to 3,000,000 centipoise at 25°C. Here, Vi in the formula represents vinyl, and R ¹ is vinyl, phenyl, and has 1 carbon atom.
-8 alkyl groups, fluoroalkyl groups having 3 to 10 carbon atoms, and mixtures thereof, and x is from 330 to 11,000. The vinyl-containing polysiloxane can be present as a blend of such polysiloxanes, in which case up to 50% by weight of the vinyl-containing polysiloxane can be present as a blend of such polysiloxanes, with up to 50% by weight of the following formula: The second vinyl-containing polysiloxane may be a second vinyl-containing polysiloxane. Here, Vi in the formula represents vinyl, ^R2 is selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, phenyl, a fluoroalkyl group having 3 to 10 carbon atoms, and a mixture thereof, and y is 1~4000
And z is 1 to 4000. The second polysiloxane is
It has a viscosity of 1000-1000000 centipoise at 25°C. Preferably, the first polysiloxane is
It has a viscosity of 1000000 to 200000000 centipoise,
The second polysiloxane has a viscosity of 50,000 to 500,000 centipoise at 25°C. Also preferably, the vinyl content of such vinyl-containing polysiloxanes or blends is from 0.01 to 1.0 mole percent. To 100 parts of vinyl-containing polymer are added 0.5 to 50.0 parts by weight, preferably 0.5 to 3.0 parts by weight of hydrogen-containing polysiloxane. Hydrogen-containing compounds are It can be a hydride resin consisting of SiO ₂ units and SiO 2 units. Here, the ratio of ^R3 to Si is 1.1 to 1.9, and ^R3 is selected from the group consisting of alkyl groups having 1 to 8 carbon atoms, phenyl groups, and fluoroalkyl groups having 3 to 10 carbon atoms. In addition, the resin can contain a large number of (R ³ ) ₂ SiO units such that the R ³ to Si ratio is between 1.5 and 2.1. The specific hydrogenated compound has the following formula: polysiloxane. here
R ⁴ is the same as R ³ but can also indicate hydrogen,
v is 1-1000, and w is 0-200. The viscosity of this polymer is between 1 and 10,000 centipoise at 25°C. Since the present invention provides an addition cure silicone rubber, platinum is used to catalyze the curing reaction. As is well known to those skilled in the art, approximately 0.1 parts per million parts of vinyl polymer (i.e., 0.1 ppm)
or more platinum is required. The resulting composition of the components is cured by known means such as extrusion, molding or injection.
Molded silicone rubber products can be obtained. Of course, one skilled in the art can add various processing aids and fillers to the composition to achieve the desired effect. It is also clear that the skilled silicone rubber processor can control the rheological properties of the composition during compounding by selectively adjusting the mutual proportions of the components. Hydroperoxy inhibitors as disclosed in the Bobair patent may also be incorporated into the compositions of the present invention. 0.004 parts by weight or more of inhibitor per 100 parts of vinyl-containing gum is effective in inhibiting platinum-catalyzed curing reactions. The inhibitor has the formula -C-O-O
Contains at least one -H hydroperoxy group. Particularly suitable inhibitors are h-butyl hydroperoxide, metal ethyl ketone peroxide, cumene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide and 2,5-
Dimethyl-2,5-dihydroperoxyhexane. Examples of silanol-containing materials that are considered useful cure modifiers include post-process heat treated silicas and fumed silicas such as Aerosil and Cab-O.
-Sil, as well as low molecular weight silanol fluids that are sometimes used as processing aids. Such silanol fluids include silanol chain-terminated polydimethylsiloxane oils, diphenylsilanediol, dimethylphenylsilanol, and similar silanol-containing materials. Using the method of the present invention, a silicone rubber processor can selectively add from 0.01 to 50 parts by weight, preferably from 0.5 to 10 parts by weight, of a silanol-containing cure modifier per 100 parts of vinyl-containing polysiloxane gum. Curing of catalyst-containing compounds can be controlled. The basic component of the composition produced by the method of the invention is a vinyl-containing polysiloxane of the formula, the polymer containing 0.005 mole percent or more vinyl;
Preferably it contains 0.01 to 1 mol% vinyl.
Preferably the polymer is linear and the vinyl group is preferably at the terminal position of the linear polymer chain. However, in a broad sense, in the present invention, the vinyl group may be located anywhere on the polymer chain. Regardless of whether or not there is some polymer chain vinyl present in the polymer, it is preferred that at least some terminal vinyl groups are present in the polymer. The polymer can be a single species or a blend of vinyl-containing polymeric materials, the polymer having a viscosity of 1000 to 300 million centipoise at 25°C, and the final blend at 25°C.
It has a viscosity of 11,000 to 30,000,000 centipoise. In the optimal example, the polymer of formula 1000000 at 25°C
It has a viscosity of ~200000000 centipoise. Other substituents on the vinyl group can be monovalent hydrocarbon groups or monovalent halogenated hydrocarbon groups, preferably having up to 10 carbon atoms. Most preferably, the R substituent is selected from lower alkyl groups having 1 to 8 carbon atoms, vinyl groups, phenyl groups and fluoroalkyl groups having 3 to 10 carbon atoms, such as trifluoropropyl. Among the most preferred polymers within the scope of vinyl-containing polymers of the formula are vinyl-containing polymers of the formula, ie, strictly linear polymers having vinyl-terminated units. The polymer or blend thereof has a viscosity of 1,000 to 2,000,000 centipoise at 25°C, with polymers having a viscosity of 1,000,000 to 2,000,000 centipoise at 25°C being preferred. When a polymer of the formula is used as a polymer within the range of the formula, the polymer of the formula need not be a single type of polymer, but can be a blend of vinyl-containing polymers of the formula having different viscosities. In this regard, within the formula the R ¹ group can be vinyl, but in most instances R ¹
It should be noted that it is preferred that the group is not a vinyl group. Within the vinyl concentration range mentioned above, R ¹
Compositions can be made in which none of the groups are vinyl. For high viscosity systems, vinyl-containing polymers or blends thereof of the formula and
It has a viscosity of 200000000 centipoise. Within the formula, R ¹ can be selected from vinyl;
It may be located anywhere on the polymer chain. However, according to what has been said above, it is preferred that only a minimum number of R ¹ groups be vinyl groups. Preferably R ¹
is phenyl, a lower alkyl group having 1 to 8 carbon atoms, and a fluoroalkyl group having 3 to 10 carbon atoms,
For example, selected from the group consisting of trifluoropropyl. However, the R ¹ group can be selected from monovalent hydrocarbon groups having up to 10 carbon atoms and monovalent halogenated hydrocarbon groups. The viscosity of the polymer of the formula varies from 1000 to 300000000 centipoise at 25°C and the value of x varies from 330 to 11000. The vinyl-containing polymers mentioned above are the basic components of the silicone rubber compositions of the present invention. Another basic component in the addition cure system defined by this invention is a hydrogen-containing polysiloxane crosslinker. Any hydrogenated crosslinking agent commonly used in platinum-catalyzed SiH-olefin reactions to form silicone elastomers or silicone polymers can be used in the present invention. Suitable hydrogenated crosslinking agents for use in silicone elastomers either at room temperature or elevated temperature are shown below. for example, Hydrogenated crosslinkers consisting of SiO 2 units and SiO ₂ units can be used. Here the ratio of ^R3 to Si part is 1.1-1.9,
R ³ is selected from the group consisting of a monovalent hydrocarbon group having up to 10 carbon atoms or a monovalent halogenated hydrocarbon group. Preferably ^R3 is selected from the group consisting of alkyl groups having 1 to 8 carbon atoms, phenyl groups and fluoroalkyl groups having 3 to 10 carbon atoms. A particularly preferred fluoroalkyl group is trifluoropropyl. In general, it is preferred for the hydrogenated crosslinking agents used in the invention that their hydride content is between 0.05 and 5% by weight, especially between 0.1 and 1% by weight. Other hydrogenated crosslinkers are those containing monofunctional units, tetrafunctional units and difunctional units. For example, as a hydrogenated crosslinking agent in the present invention, Hydrogenated silicone resins consisting of SiO ₂ units and (R ³ ) ₂ SiO units can be used. Here the ratio of ^R3 to Si moieties is 1.5-2.1. In this case as well, the hydride content of the silicone resin must be within the above-mentioned range if it is necessary to obtain a suitable crosslinking density in the final cured product. In a broad sense
The R ³ group can be selected from a monovalent hydrocarbon group having up to 10 carbon atoms or a monovalent halogenated hydrocarbon group, but preferably the R ³ group is a lower alkyl group having 1 to 8 carbon atoms, a phenyl group, and a monovalent halogenated hydrocarbon group. Number of carbon atoms: 3-10
selected from fluoroalkyl groups. A most preferred fluoroalkyl group is trifluoropropyl. It should also be noted that it is desirable for such hydrogenolinkers to have no vinyl groups or other unsaturated groups within them. This is because the presence of such vinyl or unsaturated groups accelerates the curing of the composition. However, this is not a strict requirement for the compositions of the invention, since the inhibitors are added to the compositions of the invention, as is the case with conventional compositions. Therefore, some amount of unsaturation in the hydrogenated crosslinker is acceptable. The only undesirability of including a certain amount of unsaturation in the hydrogenated crosslinker is that the proper crosslink density may not be obtained. Generally, when an inhibitor additive is used in this invention and optimal physical properties are desired in the cured composition, the hydrogenated crosslinker is
Only 0.001 mole % or less of unsaturated groups is allowed. Other suitable hydrogenated crosslinkers have the following formula: It is a compound of Note that although the compound of formula is linear, hydride-containing branched polymers can also be used as hydrogenated crosslinking agents in the present invention. However, linear polymers, such as the compounds of the formula, are preferred as they produce cured elastomers with optimal physical properties. In the formula, R ⁴ is a monovalent hydrocarbon group and a monovalent halogenated hydrocarbon group,
Preferably, it is selected from those having 10 or less carbon atoms. Particularly preferably ^R4 is selected from C1-C8 alkyl, phenyl, C3-C10 fluoroalkyl and hydrogen. A preferred fluoroalkyl group is trifluoropropyl. Thus, the hydrogenated polysiloxane polymer crosslinker generally has a viscosity of 1 to 100,000 centipoise at 25°C, preferably 1 to 10,000 centipoise at 25°C. In the formula, v is 1 to 1000
It is preferable that w is 0 to 200. Although the hydrogen atoms in the hydrogen-containing polysiloxane polymers of the formula can be located only at terminal positions of the polymer chain, hydrogen atoms can also be located at internal positions of the polymer chain. Terminal configuration of hydrogen atoms is desirable to provide optimal physical properties to the cured composition. In this respect, it is also true that the particular hydrogenated crosslinking agent can be chosen depending on the end use for which the composition is intended. However, the hydride resins disclosed above, particularly the hydrogen-containing polysiloxanes of the formula, are suitable hydrogenated crosslinking agents for the production of silicone elastomers.
As mentioned above, it is preferred that the viscosity of the polymer of the formula falls within the range of 1 to 10,000 centipoise at 25°C, particularly 1 to 1,000 centipoise at 25°C. Another essential component of the compositions of the invention is a platinum catalyst. Generally, a platinum catalyst with a platinum metal content of 0.1 ppm or more must be used. This platinum catalyst can be in any form. It can be solid platinum metal or a solubilized platinum complex deposited on a solid support. Any type of platinum catalyst will work effectively in the present invention. A preferred platinum complex is a solubilized platinum complex. Many types of platinum compounds are known for SiH-olefin addition reactions.
Such platinum catalysts can be used in the reaction in the present invention. Suitable platinum catalysts are platinum compound catalysts that are soluble in the reaction mixture, especially if optical clarity is required. The platinum compound can be selected from those having the formulas (PtCl ₂ /olefin) ₂ and H (PtCl ₃ /olefin), as described in Ashby US Pat. No. 3,159,601. The olefins shown in these two formulas can be almost any type of olefin, but are preferably C2-C8 alkenylene, C5-7 cycloalkenylene or styrene. The specific olefins in the above formula are ethylene, propylene,
Various isomers of butylene, such as octylene, cyclopentene, cyclohexene, and cycloheptene. Another platinum-containing material that can be used in the compositions of the present invention is the platinum chloride-cyclopropane complex (PtCl ₂ /C ₃ H ₆ ) ₂ described in U.S. Pat. No. 3,159,662 to Ashby. Furthermore, platinum-containing materials are
chloroplatinic acid and up to 2 moles per gram of platinum of a component selected from the group consisting of alcohols, ethers, aldehydes, and mixtures thereof, as described in U.S. Pat. It can be a chain. Karstedt U.S. Patent No.
The flame retardants disclosed in US Pat. No. 3,814,730 are also suitable platinum compounds. Generally, platinum complexes of this type are formed by reacting chloroplatinic acid containing 4 moles of water of hydration with tetravinylcyclotetrasiloxane in the presence of sodium bicarbonate in an ethanol solution. From a broad perspective, solid platinum deposited on a solid support contains 0.1 ppm or more of platinum metal, preferably 1 to 50 ppm of platinum metal, per 100 parts by weight of a vinyl-containing polymer of the formula or a blend of such polymers. or used as a solubilized platinum complex. Together with these components, from 1 to 50 parts by weight of a hydrogenated crosslinking agent having a hydride content within the ranges mentioned above are used, preferably from 1 to 25 parts by weight. Yet another basic ingredient in the compositions of the invention is an inhibitor. It has been determined that the desired inhibition level in curing the compositions of the invention is achieved by the presence of hydroperoxy groups. In order to achieve any inhibiting effect, the compositions of the present invention must have at least
It was determined that 0.004 parts of inhibitor compound must be present. However, the amount of inhibitor compound added to the composition will vary depending on the particular use of the composition, as will be readily appreciated. The higher the level of inhibitor present, the longer the storage stability of the composition. For most applications, the concentration of hydroperoxy compound inhibitor will range from 0.01 to 10 parts by weight per 100 parts by weight of vinyl-containing compound in the base. However, higher levels of inhibitor compounds can be used as desired to further increase the retention stability of one-component systems or to increase the pot life of two-component systems, thus extending the pot life beyond six months. Long storage stability and pot life of several weeks or more can be obtained if required. The above-mentioned preferred concentration range is for platinum catalyst containing
It merely indicates the general use of SiH-olefin compositions. A hydroperoxy-containing compound can have any desired structure provided it contains a hydroperoxy group in its molecular structure. This is because it is the hydroperoxy group that achieves the inhibiting effect for reasons that are not yet understood. As hydroperoxy compounds, methyl ethyl ketone peroxide, cumene hydroperoxide, t-butyl hydroperoxide, 1-hydroxycyclohexyl hydroperoxide, 1,
1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethyl-2,5-dihydroperoxyhexane, decalin hydroperoxide,
1,1,2,2-tetramethylpropyl hydroperoxide, p-methane hydroperoxide and pinane hydroperoxide can be used. These compounds are manufactured by Pennwalt Corp.
Manufactured and distributed by Hercules Inc. and Lucidol Chemical Cc. The above compounds are exemplary only and many other compounds can be used as compounds containing hydroperoxy groups are well known. For polymers of the formula and range, these are well known compounds. See, eg, Jeram and Striker, US Pat. No. 3,884,866. To prepare such polymers, vinyl-containing cyclic polysiloxane compounds or non-vinyl-containing chain terminators are typically equilibrated at elevated temperatures to produce high viscosity vinyl-containing polymers. Such equilibration reactions are carried out by using alkali metal catalysts or, in the preparation of low viscosity vinyl-containing polymers, by using acid catalysts, such as toluenesulfonic acid or acid-activated clays. When it is desired that the polymer contain some fluoroalkyl groups, a slightly different approach is taken, such as that disclosed in Razzano, US Pat. No. 3,937,684. Hydrogenated crosslinkers are also well known, as disclosed in Dieram et al., US Pat. No. 3,884,866, supra. Briefly, hydride resins are prepared by hydrolyzing a suitable hydrochlorosilane in a two-phase hydrolysis system, i.e., water and a water-immiscible solvent, and separating the resulting hydrolysis products. , easily manufactured. Hydrogen-containing polysiloxane crosslinkers of the formula are also prepared by equilibration or hydrolysis processes, typically by equilibrating the tetrasiloxane with a suitable hydrogenated chain stopper in the presence of an acid-activated equilibration catalyst. Manufactured by. For example, Siciliano (Sici−
The methods disclosed in Siciliano and Holdstock, US Pat. No. 3,853,933 and Siciliano and Holdstock, US Pat. No. 3,853,934, can be employed.
If the polymer is a fluorosilicone-containing polymer, the Lazano U.S. patent no.
Using the special method disclosed in No. 3937684. Other ingredients can be added to the basic composition of the invention. Vinyl-containing polysiloxanes can be used as reinforcing agents to impart good physical strength to the final composition, and are comprised of 1 to 50 parts by weight per 100 parts by weight of the base vinyl-containing polymer of the formula or
Preferably a concentration of the compound of the following formula from 1 to 25 parts by weight is used. where vinyl groups are present only at internal positions of the polymer chain. Similarly, the vinyl content of this polymer is determined by the vinyl concentration of all vinyl-containing polymers.
The value should be 0.005 mol% or more, preferably in the range of 0.001 to 1 mol%. Although higher vinyl contents can be used, they are of no benefit and reduce the strength of the composition. In the formula, Vi represents vinyl and the R ² group is selected from monovalent hydrocarbon groups having up to 10 carbon atoms and monovalent halogenated hydrocarbon groups. Preferably, the R ^group in the formula is an alkyl group having 1 to 8 carbon atoms,
It is selected from phenyl groups, fluoroalkyl groups having 3 to 10 carbon atoms (preferably trifluoropropyl) and mixtures thereof. y is 1 to 4000,
z is from 1 to 4000, and the viscosity of the polymer in the formula is 25
1000-1000000 centipoise, preferably 25 °C
in the range of 50,000 to 500,000 centipoise in °C.
Such vinyl-containing polymers can be made according to the methods disclosed in the Razzano and Dieram et al. patents mentioned above. These polymers of the formula are used essentially for the purpose of reinforcing the strength of the base composition in the absence of fillers. Vinyl-containing silicone resins, especially vinyl-containing silicone resins with fluoroalkyl substituents, can also be used as additional or separate additives in the compositions of the invention.
Preferably, the viscosity of the vinyl-containing polymer of the formula is 50,000 at 25°C even for high viscosity compositions.
Varies in the range of ~500,000 centipoise. Next, examples of the present invention will be shown. Example 1 80 parts by weight of a vinyl chain-terminated polydimethylsiloxane gum having a viscosity of 50 million centipoise at 25°C and a trimethyl chain-terminated polydimethyl having a methyl-vinyl D unit concentration of about 0.6 mole % and a viscosity of 55 million centipoise at 25°C. - 20 parts by weight of methyl-vinylsiloxane copolymer to prepare a silicone base compound. To this mixture was added 40 parts by weight of Cab-O-Sil MS-70 filler treated with octamethylcyclotetrasiloxane. These ingredients were kneaded in an ordinary dough mixer. The basic compound includes vinyl-containing gum.
Also included was 1 part by weight per 100 parts of methylene-hydrogen fluid crosslinking agent. The crosslinker is a dimethylvinylsiloxy chain-terminated polydimethyl-methylhydrogen siloxane having a viscosity of about 50 centistokes at 5°C and a hydrogen content of about 1.0% by weight. A platinum catalyst-containing masterbatch containing an inhibitor was prepared by taking a portion of the silicone base compound described above and adding the methyl hydride crosslinker thereto.
To 141.5 parts by weight of this base compound were added 5 parts by weight Lupersol DDM inhibitor and 0.5 parts by weight platinum catalyst solution. The platinum catalyst solution consists of approximately 90% by weight octyl alcohol and 10% by weight chloroplatinic acid. Different amounts of cure modifier were then added to several samples of the silicone base compound. Samples A, B, and C contained 1.5, 2.0, and 2.5 parts by weight, respectively, of a dimethylsilanol chain-terminated polydimethylsiloxane fluid cure modifier having a viscosity of about 30 centistokes at 25°C and a silanol content of about 8.0% by weight. The final compound was prepared and tested in a rheometer (Monsanto Rheometer, Model 100).

TABLE As one skilled in the art will appreciate, the amount of silanol-containing cure modifier directly affects the cure of catalyst-containing silicone rubber compounds, as measured by ODR scorch time. Example 2 Another example of a silanol-containing cure modifier is fumed silica, which was tested as follows. Four samples of the silicone base compound prepared in Example 1 were prepared in a similar manner. In this example, each sample contained 1 part by weight of methyl hydride crosslinker per 142 parts by weight of base compound.
Thus, each sample was 143 parts by weight of the base compound and each contained 2.86 parts by weight of the inhibitor-containing catalyst masterbatch compound. Contains different amounts of untreated silanol as cure modifier
Cab-O-Sil HS-5 was added to the mixture, which was tested in the same manner as Example 1. Table 1 shows the cure control properties of untreated fumed silica.

Table: As can be seen, the scorch time of these silicone rubber compounds can be adjusted by varying the amount of the silanol-containing cure modifier, untreated fumed silica in this example or low molecular weight siloxane fluid in the previous example. can do.
It will be apparent to those skilled in the art that the scorch time is a function of the compound's cure rate. Previously, this type of silanol material was used only as a common processing aid or as an additive to improve the rheological properties of silicone compounds, but the method of the present invention allows silanol processing While it allows manufacturers to selectively control the cure rate of catalyst-containing compounds, which provides the desirable benefits of longer compound pot lives and improved processability, the prohibitive properties of shelf-stable compounds It's not alleviated in the slightest.

Claims (1)

[Claims] 1 (i) 100 parts by weight of the formula R _a SiO _(4-a)/2 (R in the formula is an alkyl group having 1 to 8 carbon atoms, a vinyl group, a phenyl group, a carbon atom number selected from the group consisting of 3 to 10 fluoroalkyl groups and mixtures thereof, and the vinyl unsaturation in the polymer is
0.005 mol% or more, and a is 1.98 to 2.01)
(ii) a platinum catalyst of 0.1 ppm or more based on the weight of said polysiloxane gum; and (iii) a silicon-containing linear polysiloxane gum or a blend thereof;
0.5 to 50 parts by weight of a hydrogen-containing polysiloxane having one or more hydrogen bonds to form a silicone-based compound; 0.01 to 50 parts by weight of a low viscosity silanol-containing polysiloxane fluid; controlling the cure of the addition-curable silicone rubber compound by adding a silanol-containing cure modifier selected from the group consisting of synthetic silica, fumed silica, diphenylsilanediol, and dimethylphenylsilanol; and curing the silicone rubber compound. A method for controlling the curing of an addition-curing silicone rubber compound, comprising the step of: 2. A portion of the vinyl-containing silicone-based compound has at least one hydroperoxy group of the formula -C-O-O-H in an amount sufficient to inhibit the curing reaction of the platinum-catalyzed silicone rubber compound. 2. The method of claim 1, including the step of forming an inhibitor-containing catalyst compound by mixing an inhibitor and an amount of platinum catalyst effective to cure the silicone rubber. 3. The method of claim 2, wherein the hydroperoxy inhibitor is present in an amount of 0.004 parts by weight or more per 100 parts by weight of vinyl-containing polysiloxane gum. 4 Add 1 to the silicone base compound.
2. The method of claim 1, wherein the method includes ˜100 parts of methylsiloxy-treated silica filler. 5 The low viscosity silanol-containing polysiloxane fluid has the following formula: (R in the formula represents a monovalent hydrocarbon group or a mixture thereof, m is equal to 0 to 40), and
2. The method of claim 1, having a viscosity of about 1 to 50 centipoise. 6. The method of claim 1, wherein said cure modifier is present in an amount of 0.5 to 10 parts by weight per 100 parts by weight of vinyl-containing polysiloxane gum. 7 The vinyl-containing polysiloxane gum has the following formula: (Vi in the formula represents a vinyl group, ^R1 is selected from vinyl, phenyl, an alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 3 to 10 carbon atoms, and a mixture thereof, and x is 330-11000) and has a viscosity of about 1000-300 million centipoise at 25°C. 8. The inhibitor is selected from t-butyl hydroperoxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide and 2,5-dimethyl-2,5-dihydroperoxyhexane. The method according to claim 2. 9. The method of claim 1, wherein the cure modifier is selected from silanol chain-terminated polydimethylsiloxane oils, diphenylsilanediol, and dimethylphenylsilanol.