JPH03139529A - Modification of silicone gel - Google Patents

Abstract

PURPOSE:To obtain a silicone gel which little causes deterioration of the physical properties with the lapse of time and can show stable performances by reacting a silicone gel cured with a platinum catalyst with a specified substance having a function of deactivating the platinum catalyst. CONSTITUTION:An uncured silicone gel is cured by an addition reaction catalyzed by a platinum catalyst as a hydrosilylation catalyst. The cured silicone gel is reacted with a substance selected from among sulfur, phosphorus, a tin compound and an amine compound each of which has a function of deactivating the platinum catalyst in a vapor phase and/or a liquid phase of the substance to stop a further addition reaction inside the silicone gel. The silicone gel as the constitutional element comprises dimethylsiloxane component units. Examples of the platinum catalyst used include finely divided elementary platinum, chloroplatinic acid, platinum oxide and a complex salt of platinum with an olefin.

Description

[Detailed description of the invention]

(Purpose of the invention)

[Industrial application field]

The present invention aims to reduce the change in physical properties over time of silicone gel, which has become popular as a cushioning material, vibration isolating material, and packaging material, and to obtain a material that exhibits more stable performance. The present invention relates to a method for modifying silicone gel.

[Background of the invention]

Recently, the excellent cushioning and vibration-proofing properties of gel-like substances have attracted attention.
It has come to be used as insulators for various rotating equipment and OA equipment, insulators for precision, optical, and measuring equipment, special packaging materials, and cushioning materials for various sporting goods. In particular, addition reaction type silicone gels are preferred because they do not produce by-products during curing. However, when products made from this addition reaction type silicone gel, especially insulators, are incorporated into equipment, the height and hardness of the product may change over time, causing changes in the performance and characteristics of the equipment. This is becoming a problem. In other words, in the curing of silicone gel, that is, the crosslinking reaction, as the reaction progresses, the viscosity increases rapidly beyond a certain degree of crosslinking, and the so-called cage effect causes the anti-Lζ rate to drop significantly, so that the reaction appears to end. This is because he was observed as if he had done it. However, in reality, uncrosslinked components remained and the platinum-based catalyst used maintained its activity for an extremely long time, so even if left at room temperature, the reaction continued, albeit extremely slowly, resulting in increased hardness. If the material had already been incorporated into a device, hardening progressed under flexed conditions, and a creep phenomenon was observed in which the height decreased over time. Naturally, this resulted in an imbalance between the vibration in question and the silicone gel as the vibration damping material, resulting in an increase in the resonance point and a decrease in the vibration damping performance. For this reason, in the case of materials that are particularly susceptible to changes in hardness, conventional methods have been to add a high-temperature, long-term post-curing process called after-cure to completely react the uncrosslinked components. However, even in this case, it is still difficult to determine a complete reaction, and
A problem has arisen in that the processing requires a large amount of time and energy.

[Technical matters attempted to be developed] Therefore, the present invention was made in view of the current situation, and without impairing the properties of silicone gel, - after curing to an appropriate hardness, Stabilize the physical properties of the silicone gel by preventing further curing.
Furthermore, this is intended to stabilize the performance of silicone gel products. (Structure of the invention)

[Means to achieve the purpose]

Therefore, the silicone gel modification method of the present invention uses a platinum-based catalyst as a hydrosilylation catalyst, and after a curing step in which an uncured silicone gel is subjected to an addition reaction and cured, the cured silicone gel and the platinum-based catalyst are cured. A substance selected from sulfur, phosphorus, silver-based compounds, or amine compounds having a deactivation effect is reacted in the gas phase and/or liquid phase of the substance, and the subsequent addition reaction inside the silicone gel is performed. It is characterized by stopping.

[Action of the invention]

The silicone gel is an addition reaction type silicone gel in which diorganopolysiloxane composed of dimethylsiloxane component units and organohydrodiene polysiloxane are crosslinked and cured by a hydrosilylation reaction using a platinum catalyst. This platinum-based catalyst easily reacts with compounds such as sulfur, phosphorus, silver-based compounds, and amines, and is avoided during normal curing processes as it is a so-called catalyst poison that inhibits crosslinking and curing. In the present invention, after curing to an appropriate hardness, the catalyst poisoning effect of these substances is used to deactivate the catalyst and stop the reaction even if uncrosslinked components remain. Next, the method of the present invention will be specifically explained. Here, the silicone gel that is a constituent element is composed of dimethylsiloxane component units, and is a diorganopolysiloxane (component A) used in the following formula [1]: RR'2S s O-(R22S i O) nS I
R'2R-[1] [where R is an alkenyl group,
R1 is a monovalent hydrocarbon group having no aliphatic unsaturated bond, R2 is a monovalent aliphatic hydrocarbon group (at least 50 mol% of R2 is a methyl group, and when it has an alkenyl group, The content thereof is 10 mol% or less), and n is the viscosity of this component at 26°C of 100 to 10
0. 000cSt] and 25℃
The organohydrodiene polysiloxane (component B) has a viscosity of 5000 cSt or less and has at least three hydrogen atoms directly bonded to Si atoms in one molecule, and the organohydrodiene polysiloxane (component B) Ratio (molar ratio) of the total amount of alkenyl groups contained in the diorganopolysiloxane (component A) to the total amount of hydrogen atoms directly bonded to Si atoms in the diorganopolysiloxane (component A)
It is an addition reaction type silicone copolymer obtained by curing a mixture adjusted so that the To explain this silicone gel in more detail,
The diorganopolysiloxane, which is the above component A, has a linear molecular structure, and has alkenyl groups R at both ends of the molecule.
is a compound that can form a crosslinked structure by adding with the hydrogen atom directly bonded to the S1 atom in component B. The alkenyl group present at the end of the molecule is preferably a lower alkenyl group, and in consideration of reactivity, a vinyl group is particularly preferred. Furthermore, R1 present at the end of the molecule is a monovalent hydrocarbon group having no aliphatic unsaturated bonds, and specific examples of such groups include methyl, propyl, and hexyl groups. Examples include alkyl groups, phenyl groups and fluoroalkyl groups. In the above formula [■], R2 is a -valent aliphatic hydrocarbon group, and specific examples of such groups include alkyl groups such as methyl, propyl, and hexyl groups, and vinyl groups. Examples include lower alkenyl groups such as However, when at least 50 mol% of R2 is a methyl group and R2 is an alkenyl group,
Preferably, the alkenyl group is present in an amount of 10 mol% or less. If the amount of alkenyl groups exceeds 10 mol %, the crosslinking density becomes too high and the viscosity tends to increase. In addition, n is usually 100 to 100 when the viscosity of this A component at 2δ°C is
．． , 000cSt, preferably 200-20, 000
It is set within the range of cst. The organohydrodiene polysiloxane, which is the above component B, is a crosslinking agent for component A, and hydrogen atoms directly bonded to Si atoms add to the alkenyl group in component A to harden component A. It is sufficient that the B component has the above-mentioned effect, and the B component can have various molecular structures such as linear, branched chain, cyclic, or network. Also,
In addition to the hydrogen atom, an organic group is bonded to the Si atom in component B, and this organic group is usually a lower alkyl group such as a methyl group. Furthermore, the viscosity of component B at 25°C is usually 5000 cSt or less, preferably 5
00 cst or less. Examples of such components include organohydrogensiloxanes with both molecular ends capped with triorganosiloxane groups, copolymers of diorganosiloxane and organohydrogensiloxanes, and tetraorganotetrahydrogenshiff autodetrasiloxanes. , HR12S”
Mention copolymerized siloxanes consisting of O+y2 units and S i O4/2 units, and copolymerized siloxanes consisting of HR'2S i O,,2 units, R'3S j OI/2 units, and SiO4,2 units. Can be done. However, in the above formula, R1 has the same meaning as the previous three. The ratio of the total molar amount of alkenyl groups in component A to the total molar amount of hydrogen atoms directly bonded to Sl in component B is usually 0.1 to 2.0, preferably 0. It is manufactured by mixing and curing component A and component B so that the ratio falls within the range of 1 to 1.0. The curing reaction in this case is usually carried out using a platinum-based catalyst. Examples of such platinum-based catalysts include finely ground elemental platinum,
Mention may be made of chloroplatinic acid, platinum oxide, complex salts of platinum and olefins, platinum alcoholades, and complex salts of chloroplatinic acid and vinylsiloxanes. Such a catalyst Ci,4
Usually O-0-1 based on the total weight of component F and component B
pp platinum equivalent amount, the same applies hereinafter) or more, preferably 0.5p
Used in amounts greater than pm. There is no particular restriction on the upper limit of the amount of such catalyst, but for example, when the catalyst is in liquid form or can be used as a solution, an amount of 200 ppm or less is sufficient. The silicone gel obtained by mixing and curing such component A, component B, and catalyst is rated according to JISK (K-2
The penetration, measured at 207-198050g load), usually has a range of 5 to 250 degrees. The hardness of such a silicone gel can be adjusted by using the amount of the component A in excess of the amount that can form a crosslinked structure with the hydrogen atoms directly bonded to Si in the component. can. In addition, as another method, silicone oil having methyl groups at both ends is applied to the resulting silicone gel for 5 to 7 hours.
It can also be adjusted by adding it in advance in an amount within the range of 5% by weight. Such silicone gels can be prepared as described above, or commercially available ones can also be used. Examples of commercial products that can be used in the present invention include CF3027, TOUGH-3, TOUGH
-4, TOUGH-5, TOUGH-6 (■Toray Silicone 11) and X32-902/cat 1300
(manufactured by Shin-Etsu Chemical Co., Ltd.), F25O-121 (Nihon Uniriki It), and the like. In addition to the above-mentioned A component, B component, and catalyst, pigments,
Curing retarders, flame retardants, fillers, etc. may be added within the range that does not impair the properties of the resulting silicone gel, and a silicone gel containing microscopic hollow spherical fillers may also be used. Examples of such materials include Phyllite (registration direction a) manufactured by Nippon Phyllite Co., Ltd. and Expancel (registered trademark) sold by the same company. Furthermore, lead powder, metal mal! It, whiskers, conductive fillers, piezoelectric fillers, etc. can also be mixed. Specifically, in the curing step of subjecting the uncured silicone gel to an addition reaction and curing it, the uncured silicone gel mixed with the above-mentioned component H, component B, and catalyst,
It is poured onto a molding surface such as a specified mold, tray, or a belt surface covered with a film, and is then heated at a specified temperature and for a specified period of time, applying pressure as necessary.
A silicone gel having a desired shape and hardened to a desired hardness is obtained by heating at 80° C. for 1 hour. The steps up to this point are exactly the same as usual, but in the method of the present invention, the next step is to deactivate the platinum catalyst present in the cured silicone gel without losing its activity. In this process, silicone gel that has been converted into gold sand is placed in an atmosphere containing organic or inorganic compounds such as sulfur, phosphorus, silver-based compounds, and amines, which have been avoided during the curing process as catalyst poisons. , a platinum-based catalyst and the compound are reacted. Specifically, the above compounds may be placed in an autoclave with a vaporized atmosphere or in a stirring tank in which they are dissolved in water or a solvent, and the temperature conditions at that time are 50 to 2.
The temperature is 30°C, preferably about 70 to 180°C. After that, if you take out the treated silicone gel, you will get a silicone gel that will not harden after that, with no changes in shape, dimensions, etc. from the conventional product, so you can proceed with the same process as before. Turn it and use it as usual. Here, the compound that deactivates the catalyst used in the present invention easily diffuses into the silicone gel and reacts with the platinum-based catalyst more quickly than with the reactive groups of the silicone gel. Any compound that forms a bond may be used, and it does not matter whether it is organic or inorganic.Specifically, as a sulfur-based compound, as an inorganic compound, ammonium sulfate, ammonium persulfate, persulfate, etc. Examples include soda, sodium sulfite, hydrosulfide, sulfates such as hydroxyamine sulfate, sulfur, carbon disulfide, sodium sulfoxylate (Rongalit), etc.
Examples of organic compounds include thioglycolic acid, thioglycolic acid and its derivatives such as butyl thioglycolate, and β-
Examples include mercaptan compounds such as mercaptopropionic acid, surfactants such as thioacetic acid, thiourea, sulfonates, and sulfate ester salts. In addition, as for phosphorus-based compounds, examples of inorganic compounds include phosphoric acid, ammonium phosphate phosphorous acid, hypophosphorous acid, sodium pyrophosphate, acidic sodium metaphosphate,
Examples include phosphoric acid and its salts such as sodium tripolyphosphate, and examples of organic phosphorus compounds include trimethyl phosphate, dialkyldithiophosphoric acid, and phosphorous esters. Furthermore, tin compounds include various tin chlorides and tin oxides, as well as rhodan salts and stannous sulfate, and amine compounds include iminobispropylamine, triethylamine, 3-diethylaminopropylamine, Examples include tetramethylethylenediamine and 3-methoxypropylamine. In the present invention, the platinum-based catalyst, which is a hydrosilylation catalyst, selectively reacts with the compound in the atmosphere of the compound to deactivate its activity, so that uncrosslinked components are left in the silicone gel. Even if it still exists, the subsequent reaction will stop, and the hardness of the silicone gel will no longer change over time, and the creep phenomenon will be greatly reduced. Compounds for resin react with hydrosilylation catalysts using a reaction mechanism similar to those of these compounds, but the purpose of this is to selectively react with the catalyst at room temperature in advance to prevent crosslinking reactions below the curing temperature. During the reaction, the catalyst is dissociated or decomposed above the curing temperature to restore the catalyst activity.On the other hand, the compound used in the present invention also reacts with the catalyst more quickly than the reactive groups of the gel, but the catalyst The union is permanent.

[Example 1] Therefore, CF3027 manufactured by Toray Silicone Co., Ltd. was adjusted as an addition reaction type silicone gel with a mixing ratio of A liquid and Bi& of 1:1, and the diameter was 19 m rn depth 11.5
The mixture was injected into a mold having a cylindrical hole of mm in diameter, and was cured at 80°C for 1 hour, and then further cured at 100°C for 3 hours. Note that, in this silicone gel raw material, a platinum-based catalyst has already been mixed into one of the A liquid and the B liquid. Thereafter, the silicone gel was left to cool at room temperature, and the cylindrical silicone gel was taken out from the mold and used as a sample for evaluation. Next, approximately 1 g of powdered sodium hydrogen sulfite (grade 1 reagent: manufactured by Kanto Kagaku Co., Ltd.) was put into an autoclave of about 20 cc, and then a partition was placed and an evaluation sample was placed on the upper side. Close the autoclave lid and
Vacuum displacement was repeated twice, and the mixture was heated in an oil bath at 100° C. for 1 hour under reduced pressure. Thereafter, the autoclave was returned to normal temperature and pressure, and the sample was taken out and used as a product treated in Example 1. For performance comparison, the height and compression coefficient of the untreated product and the Example 1 treated product were measured in accordance with JISK-6301, and then both samples were placed in a compression set measuring device, and the initial compression ff was set at 125%. It was heated in an oven at 100° C. for 70 hours. According to the same JIS, after the set time elapsed, we measured the change in compression coefficient and the amount of permanent compressive strain, and the results are shown in Table 1.
Shown below. Table 1

[Example 2] In addition, an evaluation sample was placed in the same autoclave, and approximately 2 cc of liquid 2-mercaptoethanol (Reagent 2, manufactured by Kanto Kagaku Kogyo Co., Ltd.) was injected with a syringe.
Perform the depressurization operation twice, and then place it in the oil bath with the depressurized state.
Heated at 00°C for 1 hour. Thereafter, the temperature was returned to room temperature and normal pressure to obtain a treated product of Example 2. The treated product of Example 2 and the untreated product were heated together in an oven at 100° C. for 70 hours, and the change in compression coefficient was measured according to the above-mentioned JIS. The results are shown in Table 2. Table 2

[Example 3] Furthermore, as an example of liquid phase treatment, an evaluation sample was put into an aqueous solution of about 5% by weight of each of the following compounds, and then heated at 85°C for 1 hour with gentle stirring. did. Thereafter, the temperature was returned to room temperature and then taken out to obtain each of the treated products of Example 3. The dissolved compounds are A → Sodium hydrogen sulfite (Kanto Chemical Industry Co., Ltd. U) B → Rongalit C (Super Light C.) (Mitsubishi Gas Chemical Co., Ltd.) C → Sulfonate surfactant (Eleminol JS-20) ) (Sanyo Kaseiko 2 Co., Ltd.) The changes in the compression coefficient were measured according to the above JTS, and the results are shown in Table 3. Table 3 The gold thread catalyst no longer retained its activity and did not meet the target. Since the crosslinking reaction can be stopped at a certain hardness, and the product is not cured beyond the desired hardness, the product performance is stable, there is almost no subsequent change in properties, and the creep phenomenon is also greatly improved.Production time is also shortened. Now you can.

Claims (1)

[Claims] After a curing step in which an uncured silicone gel is subjected to an addition reaction using a platinum-based hydrosilylation catalyst to cure it, the cured silicone gel is combined with a sulfur, phosphorus, or silver-based catalyst that has a deactivation effect on the platinum-based catalyst. a substance selected from compounds or amine compounds, in the gas phase of the substance and/or
Alternatively, a method for modifying silicone gel characterized by causing the reaction in a liquid phase and stopping subsequent addition reactions inside the silicone gel.