JPH0347664B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a novel method for producing a liquid composition for silicone rubber. [Prior art] Room temperature curable (RTV) liquid silicone rubber compositions have excellent mold release properties when cured, so they can be used with resins such as epoxy, polyester, urethane, acrylic, phenol, and plaster. It is widely used as a matrix for making replicas. The characteristics of the cured material used for the matrix include appropriate hardness, elongation, and tensile strength as well as high tear strength (about 10 kg/cm or more) as the matrix becomes larger and the shape becomes more complex. It is said that Therefore, in order to improve the tear strength, in the case of condensation reaction type RTV silicone rubber compositions, for example, about 25% reinforcing silica is added to the main component, terminal silanol-terminated diorganopolysiloxane (generally dimethylpolysiloxane). Although filling has been carried out, compositions in which reinforcing silica is simply mixed have low fluidity and have the disadvantage of significantly increasing viscosity during storage. In order to eliminate this drawback, as reinforcing silica, for example, U.S. Pat.
Using surface-treated silica that has been previously treated with trimethylchlorosilane, hexamethyldisilazane, etc. by the method described in the specification, etc., the mixture is further heated and kneaded under reduced pressure, etc., to form silica powder and disilane. A method is known in which a composition with good fluidity and suppressed thickening during storage can be obtained by blending the composition with organopolysiloxane oil. [Problems to be solved by the invention] However, the method using the surface-treated silica described above requires two steps: a step of preparing the surface-treated silica and a kneading step for wetting the silica and siloxane oil. Therefore, productivity is low because it takes a long time to manufacture, and additional equipment is required to prepare surface-treated silica.
The problem is that the resulting composition is expensive. Therefore, the object of the present invention is to provide a liquid composition for RTV silicone rubber that is simple because it does not require the preparation process of treated silica, has good fluidity, has little thickening during storage, and has good mechanical properties. The object of the present invention is to provide a cured product having excellent properties. [Means for Solving the Problems] The present invention solves the above problems by providing (A) a silanol-terminated diorganopolysiloxane having a viscosity of 500 to 1,000,000 cs at 25°C.
100 parts by weight (B) Silica powder with a specific surface area of 50 m ² /g or more
20-80 parts by weight (C) General formula below (): [In the formula, R ¹ , R ² and R ³ may be the same or different and are substituted or ratio-substituted monovalent hydrocarbon groups; a is an integer from 0 to 50] silazane (B) component represented by 0.062~ per 100g
0.25 mol, and (D) 0.5 to 40 parts by weight of water. A liquid composition for silicone rubber comprising the step of kneading at room temperature to 200°C and then removing the ammonia content to 50 ppm or less. A manufacturing method is provided. The terminal silanol-terminated diorganopolysiloxane of component (A) used in the present invention has the following general formula (): [In the formula, R ⁴ and R ⁵ are each a substituted or unsubstituted monovalent hydrocarbon group; n is a positive integer such that the viscosity at 25°C is 500 to 1,000,000 cs] General formula () , R ⁴ and R ⁵ each represent an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group; an alkenyl group such as a vinyl group or an allyl group; a cycloalkyl group such as a cyclohexyl group or a cyclopentyl group; a phenyl group , an aryl group such as tolyl group, xylyl group, naphthyl group; α
- Hydrocarbon groups such as methylstyryl groups, and
Some or all of the hydrogen atoms bonded to the carbon atoms of these groups are halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, etc.), cyano groups, etc.
It is a hydrocarbon group substituted with one species or two or more species, and specific examples thereof include a chloromethyl group, a trifluoropropyl group, and a cyanomethyl group. Among these substituted or unsubstituted monovalent hydrocarbon groups, preferred are methyl group, ethyl group,
Examples include a vinyl group and a phenyl group, and the most preferred is a methyl group. If the viscosity of the organopolysiloxane (A) is too low, the resulting cured product will have low mechanical strength, and if it is too high, the composition will be difficult to handle. 5000~100000cs is desirable. Specific examples of organopolysiloxane as component (A) include:

【formula】 (Here, p, q, and r are positive integers such that the viscosity at 25° C. is 500 to 1,000,000 cs, respectively). The organopolysiloxane of component (A) is, for example,
Corresponding cyclic oligomers, e.g.

【formula】

【formula】

A mixture of H ₂ SO ₄ , CF ₃ SO ₃ H,
Acid catalysts such as PNCl ₂ , CsOH, KOH, NaOH,
In the presence of a base catalyst such as (R ⁶ ) ₄ NOH (R ⁶ is an alkyl group such as a methyl group, ethyl group, propyl group, or butyl group), (R ⁶ ) ₄ POH, and these silanolate catalysts, the necessary amount After carrying out a ring-opening copolymerization reaction with water of
Obtained by filtration. The silica powder of component (B) used in the present invention includes, for example, dry silica such as fumed silica obtained by reacting SiCl ₄ and HSiCl ₃ under an oxyhydrogen flame, and silica powder made from sodium silicate as a starting material. Examples include wet silica. In order to obtain a good reinforcing effect, the specific surface area of the silica powder must be 50 m ² /g or more, preferably 100 m ² /g or more. In order to obtain high tear strength, fumed silica is preferable and has a specific surface area of 200 to 400 m ² /g.
Further preferred is fumed silica. Specifically, examples of the silica powder include Aerosil-130, Aerosil-200, Aerosil-300,
Aerosil-380 (manufactured by Degutsusa); MS-5, MS
-7 (manufactured by Kayabot Co., Ltd.); examples include those commercially available under trade names such as Nipsil VN3, Nipsil LP, Nipsil E-220, and Nipsil A-300 (manufactured by Nippon Silica Co., Ltd.). In the general formula () representing the silazane of component (C) used in the present invention, R ¹ , R ² and R ³ each represent an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group; Alkenyl group;
Cycloalkyl groups such as cyclohexyl; aryl groups such as phenyl, naphthyl, tolyl, xylyl; and atoms, chlorine atoms, bromine atoms, etc.),
It is a hydrocarbon substituted with one or more types such as a cyano group, and specific examples include a chloromethyl group, a trifluoropropyl group, and a cyanoethyl group. Preferred among these substituted or unsubstituted monovalent hydrocarbon groups are methyl, vinyl, phenyl, and the like. Also, a
is an integer from 0 to 50, preferably from 0 to 10. a is
If it exceeds 50, it will be economically disadvantageous because it will be difficult to manufacture and the apparent amount added will increase. Specifically, the silazane of component (C) is, for example,
[(CH ₃ ) ₃ Si] ₂ NH, [(CH ₂ = CH) _b (CH ₃ ) _3-b
Si] ₂ NH (b is an integer from 1 to 3),

【formula】

【formula】

【formula】 (where c is an integer from 1 to 24),

[Formula] (where d is 1 ~24 integer),

[Formula] (where e and f are each integers of 1 to 12). The amount of silazane used as component (C) needs to be 0.062 to 0.25 mol, and preferably 0.12 to 0.19 mol, per 100 g of silica powder as component (B). If the amount used is less than 0.062 mol, the fluidity of the composition obtained by the method of the present invention will be low, and if it exceeds 0.25 mol, no significant improvement in the effect can be expected despite the increase in the amount of raw material silazane. Furthermore, a process for removing surplus silazane after the reaction with silica is required, which is economically disadvantageous. Component (C) silazane is, for example,
It is obtained by the reaction of trimethylchlorosilane etc. with ammonia gas by the method described in No. 3927057. Component (C), silazane, reacts with the silanol present on the surface of the silica powder to stabilize the composition obtained by the present invention and prevent it from thickening during storage. Although the details of the action of water, component (D) constituting the composition of the present invention, are unknown, it is thought to have the action of selectively reacting silazane. In order to react with the silanol on the silica surface and to make it difficult to react with the terminal silanol of the diorganopolysiloxane (A) component, neutral or basic water with a pH of 6 or higher is preferable. For example, ammonia aqueous solution, ammonium carbonate aqueous solution, etc. are preferable. Furthermore, heating water to an appropriate temperature above room temperature promotes the decomposition of silazane and the volatilization of ammonia. The water content of component (D) is 0.5 to 100 parts by weight of component (A).
40 parts by weight, preferably 8 to 12 parts by weight are used.
If the amount of water is less than 0.5 part by weight, the resulting composition will have a high viscosity and will tend to thicken during storage. If it exceeds 40 parts by weight, it will take a lot of energy and time to remove excess water, which is economically disadvantageous. In the method of the present invention, a formulation containing the components (A) to (D) is first prepared and mixed uniformly, usually at room temperature. This mixing starts a reaction between the hydroxyl groups on the silica surface of component (B) and the silazane of component (C). The formulation is then heated to 80-200°C, preferably 100-150°C.
It is kneaded with This kneading is preferably carried out under closed conditions. This kneading under heating is usually 0.5 to 2
It is desirable that the reaction time is about 100 minutes, and it is thought that this completes the reaction between the hydroxyl groups on the silica surface of the component (B) and the silazane of the component (C) and the hydrolysis of excess silazane. Next, the ammonia produced by the reaction between component (B) and component (C) is removed to a content of 50 ppm or less, preferably 10 ppm or less. This method is
For example, a method can be used in which the mixture is heated in the open at about 100 to 200°C, or heated at about 80 to 150°C under reduced pressure. Appropriate heating conditions for the above-mentioned heating kneading and ammonia removal depend on the performance of the mixing device, the presence or absence of reduced pressure, the silica powder of component (B), and the type of silazane of component (C), and are desirably selected appropriately. Components other than components (A) to (D) may also be added to the composition obtained by the method of the present invention, if necessary, within a range that does not impair its properties. Preferred optional components include (E) low amounts of organosilanes and organopolysiloxanes with a molecular weight of 3,800 or less, which are added to control the thixotropy and extend the pot life of the resulting composition; It is desirable to add 20 parts by weight or less per 100 parts by weight, particularly preferably 0.5 to 20 parts by weight.
Depending on the purpose, this component (E) is added to the mixture before kneading or after ammonia is removed. Examples of component (E) include the following compounds. ( _CH3 ) _2Si ( ^OR7 ) ₂ , _CH3Si ( ^OR7 ) ₃ ,

【formula】

【formula】

【formula】

[ ^R7 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms (e.g., methyl group, ethyl group, propyl group, i-propyl group, butyl group, t-butyl group, etc.), alkenyl group (vinyl group, Hydrocarbon groups such as propenyl group, butenyl group, etc.), and some or all of the hydrogen atoms bonded to the carbon atoms of these groups are halogen atoms (e.g. fluorine atom, chlorine atom, bromine atom, etc.), cyano group It is a hydrocarbon group substituted with one or more types such as. Further, k, l, m, n, p, q and r are each positive integers such that the molecular weight is 3800 or less. ]

This component (E) is thought to have the effect of complementing the treatment of the silica surface of component (B) by components (C) and (D), and promotes wetting of the silica surface, so that the resulting composition has a fluidity. It has the function of further improving the stability of properties and viscosity. In the method of the present invention, after the ammonia removal described above and before putting it into practical use, components (A), (C), or (D) and others are added to reduce the silica powder content of component (B). Good too. Furthermore, the composition obtained by the method of the present invention is
A two-component RTV liquid silicone rubber composition using this as a main ingredient may be combined with a crosslinking agent, a tin catalyst, and, if necessary, a curing agent such as an extender. In addition to the above components, pigments, heat-resistant agents, organic solvents, etc. may be added depending on various uses, and if fast curing performance is required, tin dioctylate may be used as a catalyst. Alternatively, curing agents described in Japanese Patent Publication No. 52-36920 may be used in combination. Furthermore, the composition obtained by the present invention comprises 2
A so-called one-component RTV liquid silicone rubber composition can also be prepared by blending a crosslinking agent with high reactivity above functional level. It is also extremely useful for so-called moisture-curing RTV liquid silicone rubber, which cures by reacting with moisture in the air when stored under closed conditions and exposed to open conditions. The above component (E) and other optional components are usually
According to the method of the present invention, it is added to the blend in advance before heat-kneading and subjected to heat-kneading, but depending on the type and amount of the added ingredients, the blend is added to the blend after heat-kneading and removal of ammonia, It may be kneaded. [Example] Next, the present invention will be specifically explained with reference to Examples. In the following, "parts" represent parts by weight, and "viscosity" represents a value measured at 25°C. Example 1 Component (A): Terminal silanol-terminated dimethylpolysiloxane (viscosity 20000cs) (B) component: fumed silica (specific surface area 300m ² /
(Product name: Aerosil 300 (manufactured by Nippon Aerosil Co., Ltd.)) (C) component: Hexamethyldisilazane (D) component: Ion-exchanged water (PH6.9) () component: Terminal trimethylsiloxy-terminated dimethylpolysiloxane (viscosity 30cs) () Ingredients: Terminated silanol-terminated dimethylpolysiloxane (viscosity 30cs) 500g of component (A), component (C) in a kneader with a melt volume of 3
After 75 g of component (D) and 37.5 g of component (D) were charged and mixed for 5 minutes at room temperature, 230 g of component (B) was added and mixed under closed conditions, generating heat and generating ammonia gas. Next, after heating under closed conditions and mixing at 120℃ for 1 hour,
The mixture was mixed in the open at 160° C. for 3 hours, and heating was stopped after confirming that the ammonia odor had disappeared.
After this, 250 g of component (A) was added and mixed, and after cooling, 200 g of component () and 50 g of component () were added and mixed, and finally kneaded with three rolls to obtain a uniform composition. . Regarding the obtained composition, the initial viscosity, the viscosity after accelerated deterioration by heating at 150° C. for 2 hours, and the amount of ammonia remaining were measured. Also, for 100 parts of the composition,
3 parts of an alkoxysilane represented by the formula (n-C ₃ H ₇ O) ₄ Si and 0.5 part of a tin catalyst represented by the formula (C ₄ H ₉ ) ₂ Sn (OCOC ₁₁ H ₂₃ ) ₂ were added, and the mixture was heated at 25°C. A curing reaction was carried out for 72 hours, and the resulting cured product was measured for various properties such as hardness, elongation, tensile strength, and tear strength. The results are shown in Table 1. Comparative Example 1 In a high-speed mixer with a dissolution amount of 5, 230 g of component (B) (100
part), component (C) 57.5g (25 parts) and component (D) 23g
(10 parts) were heated and dried to prepare surface-treated silica (carbon 4.3% by weight, specific surface area 180 m ² /g, ammonia 35 ppm). 500 g of component (A) and 250 g of the surface-treated silica were placed in a kneader having a solubility of 3, and heated while mixing. After mixing at 150° C. for 1 hour, heating was stopped. Then, in the same manner as in Example 1, (A) component
250g, () ingredient 200g, () ingredient 50g added,
A composition was obtained by mixing. In the same manner as in Example 1, various properties of the obtained composition and its cured product were measured. The results are shown in Table 1. Comparative Example 2 In a high-speed mixer with a dissolution amount of 5, 230 g of component (B) (100
part), component (C) 46g (20 parts) and component (D) 23g (10 parts)
) were mixed at room temperature under closed conditions and kept for 24 hours.
A surface-treated silica was prepared by heat curing for a period of time. When 500 g of component (A) and 299 g of the above-mentioned surface-treated silica were charged into a kneader having a solubility of 3 and mixed under closed conditions, heat was generated and ammonia gas was generated. next,
The mixture was heated under closed conditions and mixed at 120°C for 1 hour, then mixed under open conditions at 160°C for 3 hours, and heating was stopped after confirming that the ammonia odor had disappeared. Thereafter, in the same manner as in Example 1, 250 g of component (A), ()
200 g of the component and 50 g of the component () were added and mixed to obtain a composition. In the same manner as in Example 1, various properties of the obtained composition and its cured product were measured. The results are shown in Table 1. Comparative Example 3 500 g of component (A) and (C) were added in a kneader with a solubility of 3.
After preparing 50g of ingredients and mixing at room temperature for 5 minutes, (B)
When 230g of ingredients are added and mixed under closed conditions, heat is generated.
Ammonia gas was generated. Next, heat under closed conditions, mix at 120℃ for 1 hour, and then heat under open conditions at 160℃ for 3 hours.
After stirring for a while and confirming that the ammonia odor had disappeared, heating was stopped. Thereafter, in the same manner as in Example 1, 250 g of component (A), 200 g of component (), and 50 g of component () were added and mixed to obtain a composition. In the same manner as in Example 1, various properties of the obtained composition and its cured product were measured. The results are shown in Table 1.

〔Effect of the invention〕

The method for producing a liquid silicone rubber composition of the present invention does not require the step of preparing surface-treated silica, and it is possible to obtain a composition that has good fluidity and suppresses viscosity increase during storage. The cured product obtained from this composition has appropriate mechanical strength and high tear strength.

Claims (1)

[Claims] 1 (A) A silanol-terminated diorganopolysiloxane having a viscosity of 500 to 1,000,000 cs at 25°C.
100 parts by weight (B) Silica powder with a specific surface area of 50 m ² /g or more
20-80 parts by weight (C) General formula below [In the formula, R ¹ , R ² and R ³ may be the same or different and are substituted or unsubstituted monovalent hydrocarbon groups; a is an integer from 0 to 50.] Silazane (B) component represented by 0.062 per 100g
A liquid composition for silicone rubber, which comprises the step of kneading a compound comprising an amount of ~0.25 mol and (D) 0.5 to 40 parts by weight of water at room temperature to 200°C, and then removing the ammonia content to 50 ppm or less. manufacturing method.