JP5319905B2 - Silicone rubber composition for mold master and mold master - Google Patents

Description

  The present invention relates to a silicone rubber composition excellent in releasability used as a reversal matrix for molding, and a mold matrix obtained therefrom.

  The silicone rubber mold used as the reversal matrix for mold making is required to have mold release durability. As an attempt to improve the mold release durability of silicone rubber molds, a hydrophilized hydrophilic silica filler using a silazane compound or a compound having an additional functional group is used for reinforcing hydrophilic There has been proposed a method of blending a product obtained by treating a porous silica. According to these methods, although the improvement of the release durability of the silicone rubber mold is recognized, it is possible to release the epoxy resin, urethane resin, etc. having high physical properties, which are the mainstream of current cast resin materials. Sex is not enough.

  On the other hand, for the purpose of further improving releasability, Japanese Patent Application Laid-Open No. 7-118534 (Patent Document 1) proposes to add a non-crosslinkable silicone polymer having a chain length equal to or longer than the base polymer to be crosslinked. In JP 2000-289034 A (Patent Document 2), the organopolysiloxane base polymer forming the silicone rubber mold has a refractive index difference of 0.01 or more and a melting point of 100 ° C. or less. It has been proposed to add a non-crosslinkable oily substance, which has achieved great results in improving the releasability.

However, the blending of these types of non-crosslinkable silicone polymers has problems such as the oil oozes out and the replicated product is soiled, and the material before curing is difficult to degas.
Japanese Patent Laid-Open No. 7-118534 JP 2000-289034 A

  The present invention has been made in view of the above circumstances, and provides a silicone rubber composition for a mold making mother mold that is excellent in releasability, less fouling of a duplicate, and excellent in defoaming property of a material before curing. With the goal.

  As a result of repeated investigations to achieve the above object, the present inventors have, as a liquid silicone rubber composition, an alkoxy group having 1 to 3 carbon atoms bonded to a silicon atom at the molecular end, and an average degree of polymerization. By blending 5 to 500 polydimethylsiloxane, a silicone rubber composition for a mold making mother mold is obtained which is excellent in releasability, less fouling of duplicates, and excellent in defoaming properties of the material before curing. As a result, the present invention has been completed.

That is, the present invention
(A) A polyorganosiloxane having two or more alkenyl groups bonded to a silicon atom in one molecule and having a viscosity at 25 ° C. of 500 to 1,000,000 centipoise; 100 parts by weight
(B) A polyorganohydrogensiloxane having three or more hydrogen atoms bonded to a silicon atom; hydrogen bonded to a silicon atom for one alkenyl group bonded to a silicon atom in component (A) Amount that is 0.4 to 4 atoms
(C) Platinum compound; 1 to 200 ppm by weight in terms of platinum atom with respect to component (A)
(D) A mold taking mother comprising a polydimethylsiloxane having an alkoxy group having 1 to 3 carbon atoms bonded to a silicon atom at the molecular end and an average degree of polymerization of 5 to 500; 0.1 to 10 parts by weight This is a silicone rubber composition for a mold.

  The present invention is described in detail below. The alkenyl group-containing polyorganosiloxane (A) used in the present invention has two or more alkenyl groups bonded to a silicon atom in one molecule, and the siloxane skeleton may be either linear or branched, Moreover, these mixtures may be sufficient. 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. Examples of the substituent bonded to the silicon atom other than the alkenyl group include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl and dodecyl, aryl groups such as phenyl, aralkyl groups such as 2-phenylethynyl and 2-phenylpropyl, Examples thereof include chloromethyl and substituted carbon hydrogen groups such as 3,3,3-trifluoropropyl. Of these, a methyl group is most preferred from the viewpoint of easy synthesis.

  Furthermore, the component (A) serves as a base polymer of the addition reaction type curable polyorganosiloxane, and it is necessary that 0.01 mol% or more of all organic groups bonded to the silicon atom is an alkenyl group. . Its viscosity at 25 ° C. is not particularly limited, but it is more preferably 50 centipoise or more, especially for applications that require fluidity before curing, especially for the purpose of rubber elastic bodies with mechanical properties. Is preferably less than 1 million centipoise.

  The polyorganohydrogensiloxane of the component (B) used in the present invention is crosslinked by an addition reaction with the component (A) to make the composition a rubber elastic body or a gel-like material, so that 3 or more per molecule , An essential component having no more than one silicon atom bonded to each silicon atom. The organic group bonded to the silicon atom other than the 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 linear, branched or cyclic. Such SiH groups may be at the end of the polysiloxane chain or in the middle, but this polyorganohydrogensiloxane has a viscosity at 25 ° C. of 10 to 500 centipoise, particularly 15 to 200 centipoise. preferable. The polyorganohydrogensiloxane of the component (B) is an amount that is 0.4 to 4 of the number of hydrogen atoms bonded to the silicon atom with respect to one alkenyl group bonded to the silicon atom in the component (A). It is preferable to use it.

  The platinum component (C) used in the present invention is a hydrosilylation catalyst. As the platinum catalyst used here, a Lamorro catalyst (platinum-octanol complex, US Pat. No. 473377), an Ashpy catalyst (platinum-vinyl) Group-containing cyclic siloxane complex, U.S. Pat. No. 4,288,345). An example is a Karlstedt catalyst (platinum-vinyl group-containing disiloxane complex, US Pat. No. 3,814,730). The blending amount of the component (C) in the present invention is a catalytic amount, and specifically, it is used in the range of 1 to 200 ppm by weight in terms of platinum atoms with respect to the component (A).

  The (D) component polydimethylsiloxane used in the present invention is a characteristic component of the present invention and imparts excellent release properties to the silicone rubber mold and defoaming properties of the material before curing.

  The polydimethylsiloxane of component (D) is substantially linear and has at least one alkoxy group having 1 to 3 carbon atoms at both ends of the molecule. Examples of the alkoxy group include methyl, ethyl, n-propyl and isopropyl, which may be the same or different, but are preferably the same from the viewpoint of easy synthesis. The average degree of polymerization, that is, the average number of silicon atoms is in the range of 5 to 500, and preferably in the range of 10 to 100. If the degree of polymerization is less than 5, the terminal alkoxy group is easily hydrolyzed, and the effect of releasing durability and defoaming property cannot be obtained due to volatilization during curing conditions or use. On the other hand, when the degree of polymerization exceeds 500, it is necessary to add a large amount of component (D), and workability is lowered.

  Such component (D), for example, partially hydrolyzes dimethyldichlorosilane in the presence of the corresponding alcohol; in the presence of the corresponding dimethyl dialkoxysilane, opens a cyclic siloxane such as octamethylcyclotetrasiloxane. Ring-equilibrating; alkoxylating the terminal silanol groups of α, ω-dihydroxypolydimethylsiloxane with the corresponding alcohol; the terminal silanol groups of α, ω-dihydroxypolydimethylsiloxane with the corresponding dimethyldialkoxysilane; It can be synthesized using various methods such as reacting methyltrialkoxysilane or tetraalkoxysilane to obtain polydimethylsiloxane having 1 to 3 arbitrary alkoxy groups bonded to the respective terminals.

  The amount of component (D) is 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of polyorganosiloxane of component (A). If it is less than 0.1 part by weight, the effect of sustaining the mold release durability and defoaming property cannot be obtained, and if it exceeds 10 parts by weight, the physical strength of the silicone rubber is lowered.

Moreover, it is preferable to mix | blend a reinforcing filler with the composition of this invention. Such fillers may be those conventionally used for silicone rubber, and examples thereof include powdered silica and carbon black. Examples of fine powder silica include fumed silica and precipitated silica. In particular, silica of fine powder having a specific surface area of 50 m ² / g or more, preferably 100 to 400 m ² / g or more is preferred. If it is less than 50 m ² / g, sufficient reinforcement cannot be obtained. The amount of these fillers used is in the range of 10 to 100 parts by weight per 100 parts by weight of component (A) and, if necessary, surface treated with organosilane, organosilazane, etc. Also good.

  In addition to the components described above, the composition of the present invention is organic such as methyl vinyl polysiloxane, acetylene alcohols, benzotriazole, triphenyl phosphite, etc. in order to have good storage stability at room temperature and maintain an appropriate curing time. It is desirable to add reaction inhibitors such as phosphorus compounds, various triazine compounds, and organic sulfur compounds. The amount of the reaction inhibitor added is preferably in the range of 1 to 2000 moles per mole of platinum atoms in the platinum-based catalyst, although depending on the inhibitory ability of various inhibitors, and the curing rate and storage stability of the resulting composition. From the viewpoint of properties, a ratio of 10 to 1000 moles is preferable. Further, if necessary, an appropriate pigment, dye, adhesion aid, antifungal agent, heat resistance improver, flame retardant or antioxidant can be added.

  The composition of the present invention is prepared by mixing the component (A) and the reinforcing silica in a known mixer such as a kneader mixer or a loss mixer in advance, and performing a heat treatment to uniformly mix to produce a compound base. Thus, the components (B), (C) and (D) can be easily produced by uniformly mixing them with a mixer. In order to improve the fluidity of the composition, a filler surface treatment agent such as organosilazane can be blended when the component (A) and the reinforcing silica are mixed in the production of the base compound.

  The mold master of the present invention can be obtained by molding and curing the silicone rubber composition with a predetermined mold according to a conventional method. In this case, the curing condition of the silicone rubber composition is generally performed around the temperature at which the resin is cured for the purpose of alleviating the shrinkage at the time of curing of the resin used for the replica. For about 2 to 20 hours at a temperature of 40 to 60 ° C.

  This mold master can be effectively used for molding a resin molding such as an epoxy resin or a urethane resin.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, the scope of the present invention is not limited by these Examples. In the examples and comparative examples, all parts are by weight.

Example 1
(A) Hydrophobic fumed silica having a specific surface area of about 240 m ² / g (manufactured by Nippon Aerosil Co., Ltd.) in 80 parts of dimethylpolysiloxane (viscosity 7000 cP, vinyl value 0.007 mol / 100 g) blocked with vinyldimethylsilicone at both ends AEROSIL R-976) Mix 20 parts with a kneader, add 6 parts of hexamethyldisilazane and 1 part of water while stirring well, mix for 1 hour without heating, then raise the temperature to 150 ° C. Subsequently, after mixing for 2 hours, the temperature was lowered to room temperature.

  To 100 parts of the base compound thus obtained, 0.1 part of (C) chloroplatinic acid-vinylsiloxane complex (platinum concentration 2 wt%), 0.05 part of tetramethyltetravinylcyclosiloxane, (B) methylhydrogenpolysiloxane (below) 3 parts was added and mixed until uniform to prepare a composition.

  To 100 parts of this composition, 0.5 part of (D) terminal ethoxy group polydimethylsiloxane (viscosity 50 cSt) was added to prepare a silicone rubber composition for a molding mother mold of the present invention.

The silicone rubber composition for mold making mother mold was thoroughly stirred and then vacuum degassed, poured into a mold and cured at 40 ° C. for 12 hours to prepare a concave mother mold, and the following evaluation was performed.
(Releasability of casting resin)
Epoxy resin NM-102 (manufactured by Nippon Polyurethane Co., Ltd.) was poured into the above matrix and cured at 70 ° C. for 2 hours, and the strength when taking out the obtained epoxy resin from the matrix was determined according to the following criteria. .
○: Light △: Slightly heavy ×: Heavy (transparent cast resin turbidity)
The turbidity of the transparent epoxy resin taken out from the matrix was evaluated by visual observation.
(Muddy mold)
The turbidity of the concave matrix was evaluated by visual observation.
(Expansion volume magnification of foam)
Immediately after stirring for 10 minutes, the silicone rubber composition for the mold master was weighed 20 ml into a 300 ml disc cup and immediately degassed with a vacuum pump. Thereafter, the volume of the most expanded foam was measured, and the magnification with respect to the initial volume was determined.

  These results are shown in Table 1.

Examples 2-5, Comparative Examples 1-12
When the blending amount of the terminal ethoxy group polydimethylsiloxane (viscosity 50 cSt) is changed as shown in Table 1, the components shown in Table 1 are blended in the amounts shown in Table 1 instead of the terminal ethoxy group polydimethylsiloxane (viscosity 50 cSt). A silicone rubber composition for a molding mother mold was obtained and evaluated in the same manner as in Example 1 except that. These results are shown in Table 1.

  From the results of Table 1, the cured product obtained from the composition according to the method of the present invention has a good releasability from a well-cast resin, and a good defoaming property is observed in the material before curing. It was.

Claims (2)

(A) A polyorganosiloxane having two or more alkenyl groups bonded to a silicon atom in one molecule and having a viscosity at 25 ° C. of 500 to 1,000,000 centipoise; 100 parts by weight
(B) A polyorganohydrogensiloxane having three or more hydrogen atoms bonded to a silicon atom; hydrogen bonded to a silicon atom for one alkenyl group bonded to a silicon atom in component (A) Amount that is 0.4 to 4 atoms
(C) Platinum compound; 1 to 200 ppm by weight in terms of platinum atom with respect to component (A)
(D) a mold taking mother comprising a polydimethylsiloxane having an alkoxy group having 1 to 3 carbon atoms bonded to a silicon atom at the molecular end and an average degree of polymerization of 10 to 100 ; 0.1 to 10 parts by weight Silicone rubber composition for molds.   A mold master made of a cured product of the silicone rubber composition according to claim 1.