JPH11140319A - Curable polyorganosiloxane composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a curable polyorganosiloxane compsn. which, after molding, can be easily released from a mold. SOLUTION: This curable polyorganosiloxane compsn. comprises: (A) 100 pts.wt. polyorganosiloxane which has in its molecule at least two alkenyl groups bonded to silicon atoms and has a viscosity of 50 to 1,000,000 cP at 25 deg.C; (B) a polyorganosiloxane having in its molecule at least two hydrogen atoms bonded to silicon atoms, the amt. of the component B being such that the ratio of the no. of moles of hydrogen atoms bonded to silicon atoms in the component B to the no. of moles of alkenyl groups bonded to silicon atoms in the component A is (0.5:1) to (5:1); (C) a catalytic amt. of a platinum catalyst; (D) 10 to 100 pts.wt. reinforcing filler; and (E) a polyorganosiloxane having in its molecule hydroxyl groups bonded to silicon atoms. The compsn. is obtd. by premixing the components A and D together, homogeneously mixing the premix with heating to prepare a compd. base, and mixing the mixture with the other components. The content of the hydroxyl group in the compsn. comprising the components A, B, C, D, and E is 0.02 to 1 wt.% as detarmined by the Karl Fischer method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an addition-curable silicone rubber composition for molding, and more particularly, to a curable poly-silicon composition having excellent mold release properties and easy release from a mold after molding. It relates to an organosiloxane composition.

[0002]

Technical background and problems of the present invention A heat-curable silicone composition which is cured by a hydrosilylation reaction has an advantage that a curing reaction can be performed in a very short time and a reaction by-product cannot be formed. Timber,
It is widely used as a molding material or an injection molding material. In particular, injection molding has been widely used in recent years because molding can be performed quickly by a short curing reaction, productivity is high, and molded members can be manufactured at extremely low cost. In order to perform highly productive molding in this injection molding, it is necessary to remove the molded product obtained by curing the material as quickly as possible from the mold and perform the next molding. There is a demand for a silicone composition having excellent properties. In order to respond to such demands, as a method of improving the releasability of silicone rubber, a method of facilitating the release of a molded product such as chrome plating on a mold surface or coating with a fluororesin has been adopted. Is not always satisfactory. On the other hand, a method of applying a surfactant or the like to a mold is also known, but there is no continuity, and it is necessary to apply again, which not only complicates the process but also adversely affects the quality of a molded product. Not the preferred method. In addition, a method of adding a metal carboxylate to a silicone rubber composition (US Pat. No. 3,549,744;
Japanese Patent Application Laid-Open No. 55-45099) has been proposed, but the silicone rubber obtained by these methods has a drawback that compression set is inferior, and it cannot be said that the releasability is sufficient. Further, it is not preferable to add a metal carboxylate to a heat-curable silicone composition which is cured by a hydrosilylation reaction, since it also adversely affects storage stability. In addition, a method of blending a non-functional organopolysiloxane containing an aryl group as a component for forming a peelable film at the time of molding is also known. However, although the releasability is improved, there are disadvantages such as blooming caused by the component blended on the surface of the molded product, giving a sticky feeling and affecting the properties of rubber properties.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a curable polyorganosiloxane composition which can be easily released from a mold after molding.

[0004]

The inventors of the present invention have conducted various studies to achieve the above-mentioned object. As a result, in the production of a curable polyorganosiloxane composition, an alkenyl group-containing polyorganosiloxane as a base polymer and a reinforcing filler were used. After pre-mixing and heat-treating or uniformly mixing to form a compound base, the compound base is mixed with a hydrogen-containing polyorganosiloxane and a platinum-based catalyst. By mixing a polyorganosiloxane containing a hydroxyl group bonded to a silicon atom to the composition and adjusting the amount of the hydroxyl group measured by the Karl Fischer method in the composition to be 0.02 to 1% by weight, excellent releasability is obtained. , A curable polyorganosiloxane that has little effect on compression set and gives a cured product without stickiness They have found that a composition can be provided, and have completed the present invention. That is, the present invention relates to (A) a polyorganosiloxane containing at least two alkenyl groups bonded to silicon atoms in a molecule and having a viscosity at 25 ° C of 500 to 1,000,000 centipoise; 100 parts by weight (B) A polyorganosiloxane containing at least two hydrogen atoms bonded to atoms; the ratio of the number of moles of silicon-bonded hydrogen in this component to the number of moles of silicon-bonded alkenyl groups in component (A) is (0.5: 1) ~ (5:
(C) platinum-based catalyst; catalytic amount (D) reinforcing silica having a specific surface area of 50 m ² / g or more;
0 parts by weight (E) A polyorganosiloxane containing a hydroxyl group bonded to a silicon atom in the molecule is contained, and the component (A) and the component (D) are mixed in advance, heat-treated and uniformly mixed to form a compound base. From other components, component (A),
A curable polyorganosiloxane composition characterized in that the amount of hydroxyl group measured by the Karl Fischer method in the composition of (B), (C), (D) and (E) is 0.02 to 1% by weight. Things.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The alkenyl group-containing polyorganosiloxane of the component (A) used in the present invention has at least two alkenyl groups directly bonded to silicon atoms in the molecule, and the siloxane skeleton may be either linear or branched. Or a mixture thereof. Examples of the alkenyl group include vinyl, allyl, 1-butenyl, 1-hexenyl, and the like, but a vinyl group is preferable because of ease of synthesis. Substituents bonded to silicon atoms other than alkenyl groups include methyl, ethyl, propyl, butyl, hexyl, alkyl groups such as dodecyl, aryl groups such as phenyl,
Examples thereof include aralkyl groups such as 2-phenylethynyl and 2-phenylpropyl, and substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl. Of these, a methyl group is most preferable in terms of easy synthesis. When cold resistance or special optical properties are required for the cured composition, it contains a phenyl group in the molecule, and when oil resistance is required, it contains a 3,3,3-trifluoropropyl group. Can be arbitrarily selected. In addition, the ingredients
(A) is a base polymer of an addition-reaction-type curable polyorganosiloxane, and it is necessary that 0.01 mol% or more of all organic groups bonded to a silicon atom is an alkenyl group. The viscosity at 25 ° C. is not particularly limited, but is more preferably 50 centipoise or more, particularly when the purpose is a rubber elastic body having mechanical properties.
For applications that require fluidity prior to curing, less than 1 million centipoise is desirable.

The polyorganohydrogensiloxane of the component (B) used in the present invention is crosslinked by an addition reaction with the component (A) to form a rubber-elastic body or a gel-like substance. 2 or more, preferably 3 or more,
It is an essential component having not more than one silicon-bonded hydrogen atom per silicon atom. The organic group bonded to a silicon atom other than a hydrogen atom is a group selected from the group consisting of an alkyl group, a phenyl group and a 3,3,3-trifluoropropyl group, but from the viewpoint of easy synthesis, a methyl group Is most preferred. As this polyorganohydrogensiloxane, the siloxane skeleton may be any of linear, branched or cyclic. Also, such an S
The iH group may be at the terminal of the polysiloxane chain or in the middle thereof, but the viscosity at 25 ° C. of the polyorganohydrogensiloxane is preferably from 10 to 500 centipoise, particularly preferably from 15 to 200 centipoise. The polyorganohydrogensiloxane of the component (B) is used in such an amount that the SiH group is 0.5 to 5 mol, particularly 1 to 3 mol, per 1 mol of the alkenyl group of the polyorganopolysiloxane of the component (A). Is preferred.

The component (C) used in the present invention is a hydrosilylation catalyst. As the platinum-based catalyst used herein, a Lamorrow catalyst (platinum-octanol complex, US Pat. No. 473377) and an Aspy catalyst (platinum-octanol complex) are used. Vinyl group-containing cyclic siloxane complex, U.S. Pat. No. 4,288,345). Examples thereof include Karstedt's catalyst (a platinum-vinyl group-containing disiloxane complex, U.S. Pat. No. 3,814,730).
The compounding amount of the component (C) in the present invention is a catalytic amount, specifically, 0.1 to 2000 ppm as platinum with respect to the component (A),
Preferably, it is used in the range of 1 to 1000 ppm.

The reinforcing filler of the component (D) used in the present invention may be any of those conventionally used for silicone rubber, and examples thereof include powdered silica and carbon black. Examples of the finely divided silica include fumed silica and precipitated silica. In particular, the specific surface area is 50 m ² / g or more, preferably
Fine powder silica of 100 to 400 m ² / g or more is preferred.
If it is less than 50 m ² / g, sufficient reinforcement cannot be obtained. These fillers are used in an amount of 10 to 100 parts by weight of component (A).
It is used in the range of 100 to 100 parts by weight, and if necessary, a surface-treated material such as organosilane or organosilazane may be used.

The polyorganopolysiloxane having a hydroxyl group bonded to a silicon atom in the molecule of the component (E) used in the present invention has a hydroxyl group directly bonded to a silicon atom, and the siloxane skeleton has a linear or branched structure. Or a mixture thereof. Such a SiOH group may be at the terminal of the polysiloxane chain or in the middle thereof, but its viscosity at 25 ° C. is not particularly limited, but in order to obtain particularly stable curing, it is 50 centipoise or more. For applications requiring fluidity before curing, those having a viscosity of 1,000,000 centipoise or less are desirable. The organic group bonded to the silicon atom other than the hydroxyl group is not particularly limited, but can be selected from the group consisting of an alkyl group, a phenyl group, and a 3,3,3-trifluoropropyl group as needed.

The amount of the component (E) used is determined by mixing the components (A) and (D) in advance, mixing by heating to form a compound base, and then mixing with other components, and measuring the content in the composition by the Karl Fischer method. When the amount of hydroxyl group is 0.02 to 1% by weight, less than 0.02% by weight has little releasing effect, and when it exceeds 1% by weight, no more releasing effect can be obtained. Foaming easily occurs in the object.

The composition of the present invention comprises, in addition to the components (A) to (E), methylvinylpolysiloxane, acetylene alcohols, and the like in order to have good storage stability at room temperature and maintain an appropriate curing time. It is desirable to add a reaction inhibitor such as an organic phosphorus compound such as benzotriazole and triphenyl phosphite, various triazine compounds, and organic sulfur compounds. The addition amount of the reaction inhibitor depends on the inhibitory ability of the various inhibitors, but is preferably in the range of 1 to 2000 mol per 1 mol of platinum atom in the platinum-based catalyst. From the viewpoint of the properties and the like, the ratio is more preferably 10 to 1000 mol. If necessary, suitable pigments, dyes, adhesion aids, fungicides, heat resistance improvers, flame retardants or antioxidants can be added.

The composition of the present invention is prepared by mixing the components (A) and (D) in a known mixer such as a kneader mixer or a loss mixer, heat-treating and uniformly mixing to produce a compound base. , If necessary, components (B) and (C)
, (E) can be easily produced by uniformly mixing them with a mixer. In order to increase the fluidity of the composition, a surface treating agent for a filler such as organosilazane may be blended when the component (A) and the component (D) are mixed in the production of the base compound.

The composition of the present invention as described above has excellent releasability by using known molding methods such as injection molding and compression molding, and does not affect rubber properties such as compression set of the cured product. Further, a molded product having no sticky feeling can be obtained.

[0014]

The curable polyorganosiloxane composition of the present invention comprises the components (A) to (E). In particular, the components (A) and (D) are mixed in advance, and then heat-treated for uniform mixing. After producing the compound base by using the component (B),
By uniformly mixing (C) and (E) and adjusting the amount of hydroxyl groups measured by the Karl Fischer method to 0.02 to 1% by weight in the present composition, the cured product is excellent in releasability. Does not affect the rubber properties such as compression set of
A molded product without stickiness can be obtained, and injection molding,
This is extremely useful because the molded product can be easily released from the mold when molded by pressure molding or the like.

[0015]

EXAMPLES The present invention will be described below with reference to examples, but the scope of the present invention is not limited by these examples. In Examples and Comparative Examples, all parts are parts by weight. Example 1 (A) Dimethylpolysiloxane having a vinyl dimethyl silicone group at both ends (viscosity 10,000 cP, vinyl value 0.005 mol /
100 g) In 100 parts, (D) a hydrophobic fumed silica having a specific surface area of 130 m ² / g (AEROSIL® manufactured by Nippon Aerosil Co., Ltd.)
-972) 30 parts were mixed with a kneader, heat-treated at 80 ° C for 1 hour, heat-treated at 150 ° C under vacuum for 2 hours,
It cooled to below ° C, and obtained the base compound. To 100 parts of the base compound, 0.5 part of (E) dimethylpolysiloxane (50 cP, hydroxyl group 6.2 wt%) having a hydroxyl group at both ends and 0.02 parts of (C) chloroplatinic acid-vinylsiloxane complex (2 wt% platinum concentration) , 0.05 parts of tetramethyltetravinylcyclosiloxane and 1 part of (B) an organohydrogenpolysiloxane (viscosity: 100 cP, Si-H equivalent: 1 mol / 100 g), and mixed until uniform to prepare a composition. . For this composition, the amount of hydroxyl groups in the compound was measured by the Karl Fischer method.
The amount of hydroxyl groups was measured using a Karl Fischer method automatic moisture meter KF-06 (manufactured by Mitsubishi Kasei Co., Ltd.) using Karl Fischer reagent SS "Mitsubishi" as a measuring reagent and a dehydrated solvent CM "Mitsubishi" as a pretreatment. 2 g of siloxane and 0.2 g of KOH were dissolved in 50 ml and measured. Moreover, the peeling force was measured by performing the following peeling test using this composition, and the mold releasability was evaluated. The smaller the peeling force, the better, and preferably 5 kgf / cm or less. Using this composition, injection molding was performed with a keypad molding die for a calculator, and the mold releasability in the injection molding was relatively evaluated in two stages of ○ and ×. Further, the surface of the molded product was evaluated for tackiness, foaming and compression set. * Peeling test The curable polyorganosiloxane composition was applied to an iron test piece (50 mm x 2.5 mm x 1 mm), heated at 150 ° C for 10 minutes with a hot-air dryer and cured, and the test piece as shown in Fig. 1 Create Next, the test piece is pulled in the direction of the arrow in FIG. 1 at a speed of 10 mm per minute by an autograph, and the peel strength is measured. * Compression set Measure the compression set of a test specimen obtained by press vulcanization at 150 ° C for 15 minutes and 180% for 22 hours at 25% compression.

Example 2 In the composition of Example 1, dimethylpolysiloxane (50%) having a dimethylsilicone group blocked at both ends of the component (B) was used.
A composition was prepared and evaluated in exactly the same manner except that the blending amount of cP and hydroxyl group (6.2 wt%) was 1.5 parts.

Example 3 The same procedure as in Example 1 was repeated except that 10 parts of dimethylpolysiloxane (50 cP, hydroxyl group 10.3 wt%) having a hydroxyl group at both ends was blocked as the component (B). Compositions were prepared and evaluated.

Example 4 (A) Dimethylpolysiloxane having a vinyldimethylsilicone group at both ends (viscosity 3000 cP, vinyl value 0.008 mol / 10
0 g) 100 parts of (D) a hydrophobic fumed silica having a specific surface area of 200 m ² / g (AEROSIL R-97 manufactured by Nippon Aerosil Co., Ltd.)
4) 30 parts, tetrahexamethyldisilazane 3 parts, city water 3
The mixture was kneaded with a kneader, heat-treated at 150 ° C. for 2 hours under vacuum, and then cooled to 60 ° C. or lower to obtain a base compound. To 100 parts of this base compound, 1.5 parts of (E) dimethylpolysiloxane (viscosity: 50 cP, hydroxyl group: 6.2 wt%) having hydroxyl groups at both ends hydroxyl-blocked, (C)
Chloroplatinic acid-vinylsiloxane complex (platinum concentration 2wt%)
0.02 parts, tetramethyltetravinylcyclosiloxane
0.05 parts and 1 part of (B) an organohydrogenpolysiloxane (viscosity 100 cP, Si-H equivalent 1 mol / 100 g) were added,
The composition was prepared by mixing until uniform and evaluated.

EXAMPLE 5 (A) Dimethylpolysiloxane having a vinyldimethylsilicone group at both ends (viscosity 10,000 cP, vinyl value 0.005 mol /
100 g) 100 parts of (D) precipitated silica (Nippon Silica Co., Ltd.)
30 parts of Nipsil LP) were mixed by a kneader, heat-treated at 80 ° C. for 1 hour, heat-treated under vacuum at 150 ° C. for 2 hours, and then cooled to 60 ° C. or lower to obtain a base compound.
100 parts of this base compound contained (E) dimethylpolysiloxane (hydroxyl
1.5 parts of 50 cP, hydroxyl group 6.2 wt%), 0.02 parts of (C) chloroplatinic acid-vinylsiloxane complex (platinum concentration 2 wt%), 0.05 parts of tetramethyltetravinylcyclosiloxane, (B) organohydrogenpolysiloxane (viscosity 100cP, Si
The composition was prepared by adding 1 part of -H equivalent 1 mol / 100 g) and mixing until uniform, and the composition was evaluated.

Example 6 (A) Dimethylpolysiloxane having a vinyldimethylsilicone group at both ends (viscosity 10,000 cP, vinyl value 0.005 mol /
100 g) 100 parts of (D) precipitated silica (Nippon Silica Co., Ltd.)
Nipsil LP) 30 parts, tetrahexamethyldisilazane 3
Parts, 3 parts of city water are mixed with a kneader, heat-treated at 80 ° C for 1 hour, and heat-treated at 150 ° C under vacuum for 2 hours.
It was cooled to 60 ° C. or lower to obtain a base compound. To 100 parts of this base compound is added (E) a dimethylpolysiloxane with a hydroxyl group at both ends, dimethylsilicone group (viscosity 50c
P, hydroxyl group 6.2 wt%) 0.5 part, (C) chloroplatinic acid-vinylsiloxane complex (platinum concentration 2 wt%) 0.02 part, tetramethyltetravinylcyclosiloxane 0.05 part, (B) organohydrogenpolysiloxane (viscosity 100cP, Si-H
(Equivalent 1 mol / 100 g) was added and mixed until uniform, and the composition was prepared and evaluated. Table 1 shows the results.

Comparative Example 1 A composition was prepared and evaluated in exactly the same manner as in Example 2, except that (E) dimethylpolysiloxane having hydroxyl groups at both ends hydroxyl-blocked with dimethylsilicone was not blended.

Comparative Example 2 A composition was prepared and evaluated in exactly the same manner as in Example 4 except that (E) dimethylpolysiloxane having a hydroxyl group-terminated dimethylsilicone group was not blended.

Comparative Example 3 A composition was prepared and evaluated in exactly the same manner as in Example 5, except that (E) dimethylpolysiloxane having a hydroxyl group-terminated dimethyl silicone group at both ends was not blended.

Comparative Example 4 A composition was prepared and evaluated in exactly the same manner as in Example 6, except that (E) dimethylpolysiloxane having a hydroxyl group-terminated dimethyl silicone group at both ends was not blended.

Comparative Example 5 The composition of Comparative Example 1 was further added with 0.3% of magnesium stearate.
Parts were blended to prepare and evaluate the composition.

Comparative Example 6 The composition of Comparative Example 1 was further mixed with 5 parts of dimethylpolysiloxane-blocked dimethylpolysiloxane (viscosity: 100 cP) to prepare a composition and evaluated.

Comparative Example 7 In the composition of Example 2, (A) dimethylpolysiloxane having vinyldimethylsilicone groups at both ends and (D) hydrophobic fumed silica were kneaded. A composition was prepared and evaluated in exactly the same manner except that the base-blocked dimethylpolysiloxane was added before kneading.

Comparative Example 8 In the composition of Example 4, when (A) dimethylpolysiloxane having vinyldimethylsilicone groups blocked at both ends and (D) hydrophobic fumed silica were kneaded, (E) dimethylsilicone having hydroxyl groups at terminal ends The composition was prepared and evaluated in exactly the same manner except that the base-blocked dimethylpolysiloxane was blended before kneading.

Comparative Example 9 In the composition of Example 5, when (A) dimethylpolysiloxane having vinyl dimethyl silicone groups at both ends and (D) hydrophobic fumed silica were kneaded, (E) dimethyl silicone having hydroxyl groups at the ends was obtained. The composition was prepared and evaluated in exactly the same manner except that the base-blocked dimethylpolysiloxane was blended before kneading.

Comparative Example 10 The procedure of Example 1 was repeated except that 15 parts of dimethylpolysiloxane (50 cP, hydroxyl group: 11.4 wt%) having a hydroxyl group at both ends was blocked as the component (E). Compositions were prepared and evaluated. Table 2 shows the results.

[0031]

[Table 1]

[0032]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the situation of a peel test in an example.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 83:07 83:06) (72) Inventor Norio Hirai 6-31 Roppongi, Minato-ku, Tokyo Toshiba Silicone Corporation

Claims (2)

[Claims] (A) A molecule containing at least two alkenyl groups bonded to a silicon atom in a molecule and having a viscosity at 25 ° C. of 50
~ 1 million centipoise polyorganosiloxane; 100
Parts by weight (B) a polyorganosiloxane containing at least two silicon-bonded hydrogen atoms in the molecule; the number of moles of silicon-bonded hydrogen in this component and the moles of silicon-bonded alkenyl groups in component (A) The ratio of numbers is (0.5: 1) to (5:
(C) Platinum catalyst; catalytic amount (D) Reinforcing filler; 10 to 100 parts by weight (E) Polyorganosiloxane containing hydroxyl group bonded to silicon atom in the molecule (A) and component (D) are pre-mixed, heat-treated and uniformly mixed to form a compound base, and then mixed with other components to form component (A),
(B), (C), (D), in the present composition consisting of (E) the amount of hydroxyl group measured by the Karl Fischer method is 0.02 ~
Curable polyorganosiloxane composition characterized in that it is 1% by weight. 2. The reinforcing filler of component (D) has a specific surface area of 50 m.
^2. The curable polyorganosiloxane composition according to claim 1, which is a reinforcing silica of ² / g or more.