JPH0360869B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to room temperature curable polyorganosiloxane compositions, and more particularly to room temperature curable polyorganosiloxane compositions having excellent fluidity. [Technical background of the invention and its problems] Conventionally, room-temperature-curable polyorganosiloxane compositions, particularly polyorganosiloxane compositions that cure at room temperature and become rubber-like, have been used as electrical insulation materials, mold materials, sealants, and seals. Widely used as a material. Generally, various inorganic fillers are used in such room temperature curable polyorganosiloxanes in order to improve the properties of the cured product, mainly mechanical strength. Among these, fumed silica and hydrophobized fumed silica are most commonly used as reinforcing fillers. However, compositions using such fumed silica suffer from thixotropy when ethyl polysilicate is used as a curing agent component, or when a small amount of water or polyhydric alcohol is added to provide deep hardening. , a disadvantage arises in that sufficient self-horizontal flow (self-leveling) is lacking. [Structure of the Invention] The present invention relates to a room-temperature curable polyorganosiloxane composition that solves these disadvantages. That is, the composition of the present invention comprises (A) 100 parts by weight of a polydiorganosiloxane whose ends are capped with silal groups and has a viscosity of 500 to 200,000 cSt at 25°C, 5 to 50 parts by weight of fumed silica, and 0.001 parts by weight of diethylhydroxylamine. A composition obtained by heating and kneading ~2 parts by weight at a temperature of 50 to 180°C,
and (B) a curing agent. To explain this, component (A) is the main component of the room temperature curable polyorganosiloxane composition of the present invention, and reacts with component (B) to crosslink and cure. Component (A) used in the present invention is a silanol-terminated polydiorganosiloxane that is normally used in this type of condensed polysiloxane composition that cures at room temperature, and particularly provides appropriate fluidity of the composition before curing. In order to give the rubber-like elastomer excellent mechanical properties after curing, the viscosity at 25°C is 500%.
It is necessary to be in the range of ~200000cSt. Examples of organic groups directly bonded to silicon atoms include alkyl groups such as methyl, ethyl, propyl, butyl, and hexyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl; Examples include aralkyl groups such as β-phenylethyl group, monovalent substituted hydrocarbon groups such as 3,3,3-trifluoropropyl group, chloromethyl group, and β-cyanoethyl group, but ease of synthesis Therefore, monovalent hydrocarbon groups such as methyl, vinyl, or phenyl groups are generally advantageous, while other organic groups provide properties such as oil resistance and paintability to the cured rubber-like elastomer. Recommended only when imparting special properties. Among them, the methyl group not only provides the easiest raw material intermediate, but also provides the lowest viscosity relative to the degree of polymerization of siloxane, favoring the balance of physical properties of the rubber-like elastomer after curing. base 85
It is preferable that at least % of the organic groups are methyl groups, and it is more preferable that substantially all the organic groups are methyl groups. However, when the rubber-like elastic body after curing requires cold resistance or heat resistance, it is recommended to use phenyl groups as part of the organic groups. Component (A) used in the present invention provides mechanical strength to the composition after curing, and the surface does not need to be treated. Trimethylchlorosilane,
Hexamethyldisilazane, linear polyorganosiloxane, hexamethylcyclotrisiloxane,
The surface may be made hydrophobic by surface treatment with octamethylcyclotetrasiloxane or the like. The blending amount of component (A) is in the range of 5 to 50 parts by weight per 100 parts by weight of component (A). If it is less than 5 parts by weight, sufficient mechanical strength cannot be obtained, and if it exceeds 50 parts by weight, fluidity cannot be maintained. Component (A) used in the present invention imparts fluidity to the composition of the present invention through heat treatment, and the amount added is in the range of 0.001 to 2 parts by weight per 100 parts by weight of component (A). . If it is less than 0.001 part by weight, the effect of imparting fluidity to the composition, which is the object of the present invention, cannot be obtained, and even if it is used in excess of 2 parts by weight, the effect will not be increased, and instead it will become fluid due to gelation. This is because it impairs sexuality. The kneading temperature is 50-180℃, below 50℃,
This is because long-time kneading is required to obtain a composition with high fluidity, which is the object of the present invention, and if the temperature exceeds 180°C, component (A) will volatilize in a short time during kneading and will not be effective. . The kneading time varies depending on the kneading temperature and is not specified, but it may normally be 1 to 8 hours. After the kneading is completed, if necessary, diethylhydroxylamine may be distilled out of the system by further heating under reduced pressure. Component (B) used in the present invention is a component that cures component (A) at room temperature, and a typical example is an organosilicon having an average of more than two silicon-bonded hydrolyzable groups in one molecule. compounds (eg, silanes, polysiloxanes). Examples of silicon-bonded hydrolyzable groups include alkoxy groups, acyloxy groups, N,N-dialkylamino groups, N-alkylamido groups, N,N-dialkylaminoxy groups, ketoxime groups, and alkenoxy groups. Component (B) may contain silicon-bonded organic groups in addition to silicon-bonded hydrolyzable groups, including alkyl groups such as methyl, ethyl, propyl, and butyl groups; vinyl groups; , an alkenyl group such as an allyl group; an aryl group such as a phenyl group; a haloalkyl group such as a 3,3,3-trifluoropropyl group or a chloromethyl group; a cyanoalkyl group such as a β-cyanoethyl group. Ru. The organosilicon compound is preferably added in such an amount that the silicon-bonded hydrolyzable group is equal to or more than the equivalent of the silanol group in component (A). When the organosilicon compound alone as component (B) does not sufficiently proceed with curing, a curing accelerating catalyst such as dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, cobalt naphthenate, tin octoate,
It may contain a small amount of metal salts of organic carboxylic acids such as iron octoate and manganese octoate, and metal alcoholates such as tetrabutyl titanate and tetrabutyl zirconate. In addition to components (A) and (B), the room-temperature-curable polyorganosiloxane composition of the present invention contains fillers (e.g., diatomaceous earth, calcium carbonate, crushed quartz).
or pigments (for example, red iron, titanium dioxide, subsalt, ultramarine) may be optionally added, and depending on the purpose, other polyorganosiloxanes may be used in combination without impairing the effects of the present invention. Good too. [Effects of the Invention] After the polyorganosiloxane composition of the present invention is prepared by the above mixing, it exhibits a suitable viscosity that allows the working time to be changed freely, and has excellent fluidity, so it can be used as a sealant, It is suitable as a molding matrix material. [Example of the Invention] Next, the present invention will be explained by referring to an example. All parts in the examples indicate parts by weight. Example 1 100 parts of silanol-terminated polydimethylsiloxane with a viscosity of 20.000 cSt at 25°C, 31 parts of fumed silica with a specific surface area of 200 m ² /g and having trimethylsiloxy groups on the surface by surface treatment, and 0.01 part of diethylhydroxylamine. into the kneading machine,
Base compound A was prepared by kneading for 3 hours while heating at 150°C. For comparison, we also prepared a base compound B, which was heated and kneaded under the same conditions without adding diethylhydroxylamine among the above components, and a base compound C, which was kneaded under the same conditions at room temperature for 3 hours.
was prepared. Add 2.5 parts of ethyl polysilicate, 0.5 part of dibutyltin dilaurate, and 30 parts of polydimethylsiloxane with a viscosity of 30 cSt at 25°C to the above base compounds A, B, and C, mix and stir uniformly, and after degassing, add 25 ml of polystyrene. The contents were poured into a plastic cup, and the cup was immediately tipped onto an acrylic resin plate to allow the contents to flow out. After being left at 25°C for 24 hours, the length of the long axis of the effluent was measured to determine flowability. The flow properties of the compositions obtained from base compounds A, B, and C were as shown in Table 1.

[Table] Example 2 100 parts of silanol-terminated polydimethylsiloxane having a viscosity of 100,000 cSt at 25°C, 13 parts of fumed silica on the surface of which polysiloxane consisting of dimethylsiloxane units is present due to surface treatment, and 0.005 parts of diethylhydroxylamine. was placed in a kneader and kneaded for 3 hours while heating to 130°C to prepare base compound D. For comparison, we also prepared Base Compound E, which was heated and kneaded under the same conditions without adding diethylhydroxylamine among the above components, and Base Compound F, which was kneaded under the same conditions at room temperature for 3 hours. was prepared. 0.2 parts of dibutyltin dioctoate and 5.0 parts of methyl tris (methyl ethyl ketoxime) silane were added to the above base compounds D, E, and F, stirred uniformly, defoamed, and then examined for flowability. The composition obtained from the base compound D of the invention exhibited flowability, while the compositions obtained from the comparative example base compounds E and F did not exhibit flowability.

Claims (1)

[Claims] 1 (A) The terminal is blocked with a silanol group, and the temperature at 25°C
A composition obtained by heating and kneading 100 parts by weight of polydiorganosiloxane having a viscosity of 500 to 200,000 cSt, 5 to 50 parts by weight of fumed silica, and 0.001 to 2 parts by weight of diethylhydroxylamine at a temperature of 50 to 180°C. thing,
and (B) a room temperature curable polyorganosiloxane composition comprising a curing agent.