JP3945984B2 - Molding material for transparent resin molding - Google Patents

Description

【００４９】
表１から明らかなように、Ａ−２をＡ−１と併用した比較例１および３で得られたシリコーンゴム型は、エポキシ樹脂を１０回注型した後の硬さ変化が大きく、成形品の脱型が次第に困難になった。そのうえ、型表面の光沢度が減少し、得られた成形品もまた、注型回数を重ねるにつれて表面が荒いものになった。一方、ヘキサメチルジシラザンで表面処理した煙霧質シリカを用いた比較例２で得られたシリコーンゴム型は、必要な硬さが得られなかった。これに対して実施例１および２で得られたシリコーンゴム型は、１０回の注型を繰り返した後も、硬さおよび表面光沢度がほとんど変わらず、成形品の外観と透明性も良好であった。
【００５０】
なお、これとは別に、実施例１および比較例２で得られた型取り材を金型に注入し、前述と同様の条件で硬化させて、厚さ２mmのシートを得た。これから、それぞれＪＩＳ Ｋ６２５２により、クレセント形試験片を作製して、引裂強さを測定した。その結果、比較例２の試験片が８N/mm[kgf/cm]の引裂強さしか得られなかったのに対して、実施例１の試験片は、２０N/mm[kgf/cm]の引裂強さを示した。
【００５１】
【発明の効果】
本発明によって、硬化して、優れた離型性を示し、機械的特性が改善され、樹脂に対して優れた型取り耐久性を示すシリコーンゴム型が得られる型取り材が提供される。本発明の型取り材から得られるシリコーンゴム型は、型取りを繰り返しても、樹脂化する成分がないので硬さの変化が少なく、また表面が荒れて、そのために成形品の外観や透明性を損なうこともないので、ゴム型の耐久性が大きい。さらに、型取りの際に外部離型剤を塗布する必要がなく、離型性を向上させるために非反応性シリコーンオイルを配合する必要もないので、その樹脂への移行による樹脂の汚損や、移行に伴う表面の荒れがない。したがって、透明エポキシ樹脂成形品のように、透明性や表面の平滑性が必要な樹脂成形品の製造に、特に好適である。
【００５２】
本発明の型取り用シリコーンゴム組成物は、上記の利点を生かして、透明樹脂の成形、およびプロトタイプ成形のような、高度の離型性を要する型取りの分野で、特に有用である。[0001]
[Industrial application fields]
The present invention relates to an addition reaction type molding material. More specifically, the present invention is used for molding which requires a high degree of releasability, such as molding of a prototype model, that is, prototype molding, after being cured in a rubber shape. The present invention relates to a molding material that is excellent in mold releasability of a molded product such as a certain urethane resin or epoxy resin and has a remarkably improved number of moldings.
[0002]
In the present invention, the mold material is fluidity in an uncured state on the entire periphery or a part of the surface of the original, and is cast or coated on the entire surface or a part of the surface of the original. It is a material in an uncured state that is brought into contact with a certain method, cured in that state, and forms a mold for production of a replica using a resin or the like.
[0003]
[Prior art]
Conventionally, silicone rubber has been widely used in various fields by taking advantage of its excellent heat resistance, cold resistance, electrical characteristics and the like. In particular, it has been used as a molding material because of its good releasability. In the fields of electronic equipment, office machines, home appliances, automobile parts, etc., it is noted that prototype molding used at the product development stage and product sample creation is effective in improving the cost and time required, especially From the viewpoint of workability, addition reaction type liquid silicone rubber has been frequently used.
[0004]
Silicone rubber using an addition reaction has preferable molding characteristics as a molding material. However, as the mechanical properties of urethane resin and epoxy resin used for molding a prototype are improved, the release property from the silicone rubber mold becomes worse. There is a trend.
[0005]
In addition to this, since the tendency to reduce the manufacturing cost of prototypes has become stronger, there has been a need for a great review and improvement in the number of molds and workability.
[0006]
In order to solve such problems, approaches have been made from both a base polymer, a crosslinking agent and a catalyst system involved in an addition reaction of a molding material, and a compounding agent. As the former, for example, as disclosed in JP-A-58-19357, a method of blending a crosslinking agent from which low-molecular polyorganohydrogensiloxane has been removed is exemplified. The method of mix | blending non-reactive silicone oil is illustrated like No.-225152 gazette. However, the former alone does not provide sufficient results for the high demands imposed on the present invention, and the latter does not provide sufficient silicone oil for cross-linking. The strength is likely to decrease, and the duplicated product is soiled because the oil oozes out, which is not preferable depending on the application, particularly when used for molding a transparent resin. Japanese Patent Laid-Open No. 50-66533 discloses that the releasability is improved by blending a non-reactive silicone oil and titanium oxide into a condensation reaction type liquid silicone rubber composition. However, in this case, there is a problem that the type and amount of other fillers used in combination are limited.
[0007]
As a base polymer, RSiO in the molecule_3/2Unit (T unit, wherein R represents an unsubstituted or substituted monovalent hydrocarbon group bonded to a silicon atom) or SiO₂A branched polyorganosiloxane having a branched group such as a unit (Q unit) and having a monovalent aliphatic unsaturated hydrocarbon group bonded to a silicon atom is cured by linear polyorganosiloxane. In addition to increasing the hardness of the resulting silicone rubber mold, mechanical properties such as tensile strength and tear strength have been improved. Examples of such branched polyorganosiloxanes include any ratio of R_ThreeSiO_1/2Vinyl group-containing MQ type polyorganosiloxane consisting of units (M units) and Q units, R in addition to the above M units and Q units₂Examples include vinyl group-containing MDQ type, MTQ type or MDTQ type polyorganosiloxane composed of SiO units (D units) and / or T units. However, such a branched polyorganosiloxane is difficult to synthesize in a controlled manner, and a silicone rubber mold obtained from a molding material containing the branched polyorganosiloxane is sufficient, although the mechanical properties are improved. Since elongation cannot be obtained, it is not suitable for reverse taper mold release. Furthermore, when it is required to release repeatedly with a complicated mold as in recent years, the branched polyorganosiloxane becomes a resin as the mold release operation is repeated at a high temperature, the mold becomes hard, and the mold surface becomes rough. As a result, not only the gloss is lowered, but also the surface of the obtained resin molded body is rough.
[0008]
In Japanese Patent Laid-Open No. 2-70755, when silica subjected to surface treatment again with hexamethyldisilazane is used as a filler of a polyorganosiloxane composition that is cured by an addition reaction type, the obtained silicone rubber mold is It is disclosed that it has excellent mechanical strength and excellent mold release durability. However, this method does not provide sufficient tear strength as a mold material, but particularly when used for casting an epoxy resin, in order to obtain the necessary hardness as a mold material, As a polymer, a branched polyorganosiloxane must be used in combination with a linear polyorganosiloxane, and as described above, there remains a problem of causing hardness change and surface roughness due to repeated mold release. Yes.
[0009]
In JP-A-7-33985, when titanium oxide having an average particle size of 0.1 to 10 μm is used as a part of a filler of a silicone rubber composition for molding that is cured by an addition reaction, a duplicate product is soiled. It is disclosed that a molding material excellent in mechanical strength and releasability can be obtained. Since the silicone rubber mold obtained from the composition is colored with titanium oxide, a transparent rubber mold capable of observing the state of the internal replica is not obtained.
[0010]
Further, as a countermeasure on the work surface for forming a prototype, an external mold release agent is frequently applied to the mold. However, this method not only complicates the work but also requires cleaning with an organic solvent when the mold release agent is transferred to the surface of the obtained replica and the replica is painted or plated. Therefore, there is a possibility that work environment will be deteriorated and pollution may be caused, and it is necessary to take preventive measures. Furthermore, when used for molding a resin that requires transparency, the transparency may be impaired by the transition to a resin.
[0011]
[Problems to be solved by the invention]
The object of the present invention is to produce a replica using a high-performance urethane resin or epoxy resin, without fouling the replica, excellent in mechanical strength and releasability of the replica, The object of the present invention is to provide a molding material suitable for molding which requires a high degree of releasability, such as a transparent resin and a prototype, which can reduce the change in hardness and roughness of the surface even if it is repeated, and can increase the number of times of molding.
[0012]
[Means for Solving the Problems]
As a result of repeated studies to solve the above-mentioned problems, the present inventors have used only a linear polyorganosiloxane as a base polymer, and as a filler, a fumes treated with a specific silazane compound. By using silica, the mold release performance of the replica from the mold after curing is remarkably improved, and there is little change in hardness even when reversing the mold, resulting in a silicone rubber mold with excellent durability. The inventors have found that the object of the present invention can be achieved and have completed the present invention.
[0013]
  That is, the transparent resin molding mold material of the present invention comprises: (A) a linear polyorganosiloxane having two or more monovalent aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in one molecule; ;
  (B) There are 3 or more hydrogen atoms bonded to a silicon atom in one molecule, or the number of monovalent aliphatic unsaturated hydrocarbon groups bonded to the silicon atom in (A) is 3 in one molecule. In the above case, the number of hydrogen atoms bonded to silicon atoms is 0.5 to 1 per one monovalent aliphatic unsaturated hydrocarbon group in the polyorganohydrogensiloxane (A) component having two or more. Amount to be 5;
  (C) platinum compound 1 to 100 ppm by weight in terms of platinum atom with respect to (A); and
  (D) 5-50 parts by weight of fumed silica surface-treated with 1,3-divinyl-1,1,3,3-tetramethyldisilazane
And a branched polyorganosiloxane having a monovalent aliphatic unsaturated hydrocarbon group bonded to a silicon atom, and a silicone oil which is not involved in crosslinking is not contained.
[0014]
In the present invention, the polyorganosiloxane (A) used in the present invention is a component that serves as a base polymer for the mold taking material. This component (A) is a straight chain having two or more monovalent aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule, and has a network structure by addition reaction with component (B). Form.
[0015]
Examples of the monovalent aliphatic unsaturated hydrocarbon group include vinyl, allyl, 1-butenyl, 1-hexenyl, etc., but the synthesis is easy, the fluidity of the composition before curing, A vinyl group is most preferable because it does not impair the heat resistance of the composition.
[0016]
Other organic groups bonded to the silicon atom of component (A) include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl; aryl groups such as phenyl; benzyl, 2-phenyl Examples include aralkyl groups such as ethyl and 2-phenylpropyl; and substituted hydrocarbon groups such as chloromethyl, chlorophenyl, 2-cyanoethyl and 3,3,3-trifluoropropyl. Of these, a methyl group is most preferred because it is easy to synthesize and has an excellent balance of properties such as mechanical strength and fluidity before curing.
[0017]
The monovalent aliphatic unsaturated hydrocarbon group may be present either at the end of the molecular chain of the polyorganosiloxane (A) or in the middle of the molecular chain, and may be present in both of them. In order to give excellent mechanical properties, it is preferable that they exist at both ends.
[0018]
The component (A) is easy to synthesize and handle, and has excellent curability and mechanical properties and releasability of the resulting silicone rubber mold. A linear polymethylvinylsiloxane which is a combination of groups is preferred. Such polymethylvinylsiloxane has the formula:
M^vD^m _xM^v, M^vD^m _xD^v _yM^v, M^mD^m _xD^v _yM^mOr M^mD^m _xD^v _yM^v
(In the formula, units M and D are as described above, superscript m represents a siloxane unit in which R is all a methyl group, and v represents one of R is a vinyl group and the remainder is a methyl group. Represents a certain siloxane unit, x and y are integers of 1 or more, and D^m _xD^v _yIs merely an indication of the number of siloxane units and does not mean a block copolymer), and examples thereof include those composed of siloxane units, which may be used alone or in combination of two or more. Absent.
[0019]
The degree of polymerization of the component (A) is not particularly limited, but for the composition before curing to have good fluidity and workability, and for the composition after curing to have appropriate elasticity, the viscosity at 25 ° C. The thing of 0.3-500 Pa * s {300-500,000 cP} is preferable, and the thing of 1-100 Pa * s {1,000-100,000 cP} is especially preferable.
[0020]
One of the characteristics of the present invention is that a branched polyorganosiloxane having a monovalent aliphatic unsaturated hydrocarbon group bonded to a silicon atom as a base polymer, that is, the aforementioned T unit and / or Q unit in the molecule. The polyorganosiloxane is not contained. As a result, the silicone rubber mold obtained from the mold material of the present invention repels the molding operation with a resin that has a functional group in an uncured state and generates heat by a curing reaction, such as an epoxy resin or a urethane resin. However, the remarkable effect that the increase in hardness accompanying the resination of such a branched polyorganosiloxane and the roughness of the surface are small is brought about.
[0021]
In the polyorganohydrogensiloxane of the component (B) used in the present invention, the hydrosilyl group contained in the molecule performs an addition reaction to the monovalent aliphatic unsaturated hydrocarbon group in the component (A). It functions as a crosslinking agent for component (A), and has at least three hydrogen atoms bonded to silicon atoms involved in the addition reaction in order to reticulate the cured product. However, when the number of monovalent aliphatic unsaturated hydrocarbon groups bonded to the silicon atom of component (A) is 3 or more in one molecule, it has 2 or more hydrogen atoms bonded to the silicon atom. Yes.
[0022]
Examples of the organic group bonded to the silicon atom of the siloxane unit include those similar to the organic group other than the monovalent unsaturated aliphatic hydrocarbon group in the aforementioned component (A), and among these, the synthesis is easy. From the viewpoint, a methyl group is most preferable.
[0023]
The siloxane skeleton in the component (B) may be linear, branched or cyclic, and a mixture thereof may be used, but a linear one is preferred.
[0024]
The degree of polymerization of the component (B) is not particularly limited, but since polyorganohydrogensiloxane in which two or more hydrogen atoms are bonded to the same silicon atom is difficult to synthesize, it is preferably composed of three or more siloxane units. Because it is easy to handle and does not volatilize during storage and when heated for curing reactions, the viscosity at 25 ° C. is 10-200 mm.²More preferably, it is / s {10-200 cSt}.
[0025]
As such component (B), the formula:
M^mD '_zM^m, M^mD^m _xD '_zM^m, M'D '_zM ', M'D^m _xD '_zM 'and M'D^m _xM '
(In the formula, the units M and D, the superscript m and the number of units x are as described above, and M ′ is (CH_Three)₂HSiO_1/2D ′ represents (CH_Three) Represents an HSiO unit, z is an integer of 1 or more, and D^m _xD '_zIs simply the number of siloxane units and does not mean a block copolymer), and is composed of siloxane units, and one type may be used or two or more types may be used in combination. .
[0026]
The blending amount of the component (B) is 0.5 to 5 hydrogen atoms bonded to the silicon atom in the component (B) with respect to one monovalent aliphatic unsaturated hydrocarbon group in the component (A). The amount is preferably 1 to 3. When the hydrogen atom abundance ratio is less than 0.5, the curing is not completely completed. Therefore, the mold obtained by curing the composition is tacky, and a silicone rubber mold is formed from the original mold. In this case, the mold releasability and the mold releasability of the replicated product obtained by molding with respect to the silicone rubber mold are lowered. On the other hand, if the abundance ratio exceeds 5, foaming is likely to occur during curing, and this is the interface between the prototype and the silicone rubber mold and the replica product obtained by molding with the silicone rubber mold. In addition to giving molds and replicas with poor surface conditions, the resulting silicone rubber molds become brittle, leading to a decrease in the number of resin castings, that is, a decrease in the mold taking life, The mechanical strength is reduced.
[0027]
The platinum compound of component (C) used in the present invention is for promoting the addition reaction between the monovalent aliphatic unsaturated hydrocarbon group in component (A) and the hydrosilyl group in component (B). It is a catalyst and is excellent in that the catalytic ability of the curing reaction is good at around room temperature.
[0028]
Examples of platinum compounds include chloroplatinic acid, complexes obtained by reacting chloroplatinic acid and alcohol, platinum-olefin complexes, platinum-vinylsiloxane complexes, platinum-ketone complexes, platinum-aldehyde complexes, and the like.
[0029]
Among these, a complex obtained by reacting chloroplatinic acid and an alcohol, a platinum-vinylsiloxane complex, and the like are preferable from the viewpoints of solubility in the components (A) and (B) and good catalytic activity.
[0030]
(C) The compounding quantity of a component is 1-100 ppm in conversion of a platinum atom with respect to (A) component, Preferably it is 2-50 ppm. If it is less than 1 ppm, the curing speed is slow and the curing is not completed completely. Therefore, the silicone rubber mold is sticky, and the mold release property of the silicone rubber mold from the original mold and the mold release from the silicone rubber mold are released. Sex is reduced.
If it exceeds 100 ppm, the curing rate is excessively accelerated, so that workability after blending each component is impaired, and it is also uneconomical.
[0031]
The surface-treated fumed silica of component (D) used in the present invention is a silicone rubber obtained by curing the molding material of the present invention without using a branched polyorganosiloxane as part of component (A). The mold has sufficient hardness, especially about 40 with JIS type A durometer, and mechanical strength such as tear strength that does not cause deformation of the mold even when obtaining a large molded product such as a prototype. It is a filler to be applied.
[0032]
As the fumed silica, the specific surface area is 50-500m²/ g is common, and gives excellent mechanical properties and transparency to the rubber mold.²/ g is preferred. In the state where the fumed silica is not subjected to surface treatment, hydroxyl groups are present on the surface. By using this treated with 1,3-divinyl-1,1,3,3-tetramethyldisilazane, it is sufficient as a silicone rubber mold without using a branched polyorganosiloxane as the component (A). Give good hardness and mechanical properties. Therefore, as described above, a rubber mold with little change in hardness and less rough surface can be obtained even if the molding of a replica, particularly an epoxy resin, is repeated. Such an effect is obtained specifically by the fumed silica treated with 1,3-divinyl-1,1,3,3-tetramethyldisilazane, and other effects used for hydrophobization. It cannot be obtained with fumed silica treated with a surface treatment agent such as hexamethyldisilazane or trimethylchlorosilane.
[0033]
The surface treatment of the fumed silica with 1,3-divinyl-1,1,3,3-tetramethyldisilazane may be performed directly on the fumed silica. The fumed silica is preliminarily treated with hexamethyldisilazane, trimethylchlorosilane. , Octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane or the like may be used for the surface treatment.
[0034]
The surface treatment can be performed by a usual method. That is, the fumed silica is put into a reaction vessel and heated to 100 to 170 ° C. under normal pressure or reduced pressure with stirring, and an excess amount of 1,3-divinyl-1,1,3,3-tetramethyldisilazane vapor is added. After the reaction with the hydroxyl groups on the silica surface, dry nitrogen gas is sent to remove the by-produced ammonia and unreacted silazane; the fumed silica is dispersed in the hydrocarbon. 1,3-divinyl-1,1,3,3-tetramethyldisilazane was added with stirring, and the mixture was allowed to react with stirring while heating if necessary. Wet method for separating and drying silica; (A) component mixed with fumed silica, 1,3-divinyl-1,1,3,3-tetramethyldisilazane is blended, The silazane is heated and kneaded at a temperature for 2 to 6 hours. Is reacted with the hydroxyl groups of the silica surface, such as in-process treatment of removing to-product in a reduced pressure is exemplified as needed. Moreover, when performing surface treatment by these methods, in order to accelerate | stimulate reaction, you may add a small amount of water.
[0035]
(D) The compounding quantity of a component is 5-50 weight part with respect to 100 weight part of (A) component, 15-30 weight part is preferable and 20-25 weight part is more preferable. If it is less than 5 parts by weight, the rubber mold obtained by curing cannot obtain sufficient hardness, and a large mold may be bent by its own weight. On the other hand, if it exceeds 50 parts by weight, it becomes hard and it becomes difficult to remove the resin.
[0036]
According to the purpose, other components can be blended in the molding material of the present invention as long as the characteristics of the present invention are not hindered. For example, as a filler other than the component (D), silica-based powders such as fumed silica, fused silica, pulverized quartz, and diatomaceous earth, and surface treatment with ordinary silicon compounds such as polyorganosiloxane and hexamethyldisilazane. In addition, calcium carbonate, aluminum silicate, titanium oxide, zinc oxide, iron oxide, carbon black and the like can be blended. Of these, except for fumed silica impairs transparency, so care must be taken when rubber-type transparency is required.
[0037]
Further, in order to improve the workability by prolonging the curing time at room temperature of the molding material of the present invention, a curing delay such as acetylene compound, diallyl maleate, triallyl isocyanurate, nitrile compound or organic peroxide is used. An agent may be blended.
[0038]
Furthermore, you may mix | blend a pigment, a plasticizer, a flame retardance imparting agent, a thixotropy imparting agent, an antibacterial agent, an antifungal agent, an adhesiveness imparting agent, etc. as needed.
[0039]
The molding material of the present invention is prepared by uniformly kneading the components (A) to (D) and other components blended as necessary by a mixing means such as a universal kneader or a kneader. Can do. Usually, the component group containing the component (B) and the component group containing the component (C) are prepared separately and stored, and both components are mixed and used immediately before use. It is also possible to store all components in the same container in the presence of a retarder.
[0040]
When the molding material of the present invention is stored in a plurality of containers, it is uniformly mixed and defoamed, and when stored in a single container, it is extruded as it is, so as to wrap the master, or one surface of the master A silicone rubber mold is produced by casting or applying the resin to the part and curing it. Curing can be performed at room temperature to a slight heating of about 60 ° C., but curing may be accelerated by heating up to 150 ° C. depending on conditions. After curing, the rubber mold is removed from the original mold, a molding resin is cast, cured at a curing temperature corresponding to each resin, and demolded to obtain a replica.
[0041]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by these examples. In the following examples and comparative examples, parts represent parts by weight, and the viscosity represents a value at 25 ° C.
[0042]
  The polysiloxane used in Examples and Comparative Examples is as follows.
  A-1: Linear polymethylvinylsiloxane having a viscosity of 5 Pa · s {5,000 cP}, in which both ends are blocked with dimethylvinylsilyl groups and the intermediate unit is a dimethylsiloxy unit;
  A-2: trimethylsiloxy unit, dimethylvinylsiloxy unit andSiO ₂ unitIn a molar ratio of 5: 1: 8, branched polymethylvinylsiloxane;
  B-1: Linear polymethylhydrogensiloxane having both ends blocked with dimethylhydrogensiloxane and having an average of 12 dimethylsiloxy units and an average of 9 methylhydrogensiloxy units in the middle.
[0043]
Silicas treated with various silazanes and used in Examples and Comparative Examples are as follows.
S-1: Specific surface area of 300 m previously treated with hexamethyldisilazane²/ g fumed silica;
S-2: Specific surface area of 300 m²/ g fumed silica.
[0044]
  Example 1
  Kneader with 100 parts of A-1 and S-1231,3-divinyl-1,1,3,3-tetramethyldisilazane 0.05 parts and water 0.05 parts were added while kneading at room temperature and kneading at room temperature, and kneading for 4 hours. And the silazane were reacted, and S-1 was dispersed uniformly. Subsequently, the pressure was reduced to remove the by-product ammonia and the unreacted silazane, and then the mixture was allowed to cool and 3.1 parts of B-1 was added while kneading, and a 1% by weight solution of chloroplatinic acid in isopropanol was added. As a platinum atom, it was added so as to be 15 ppm with respect to A-1, and kneaded to prepare a mold taking material of the present invention. The apparent viscosity of the molding material was 30 Pa · s {30,000 cP}.
[0045]
Place the original mold made of ABS resin in the container, and inject the above-mentioned mold taking material so that the thickness of the part where the hardness is measured is 12 mm in contact with the original mold so as to wrap it. It was allowed to stand for a period of time, then heated to 60 ° C. for 2 hours to be cured, and the original mold was removed to obtain a silicone rubber mold. The hardness of the said site | part was measured based on JISK6251. Moreover, the surface glossiness was measured by a method according to ASTM D523 using a handy photometer gloss checker IG-310 (Horiba, Ltd., trade name).
[0046]
This silicone rubber mold was preheated to 60 ° C., and epoxy resin CEP-5 (two packaging molds, trade name of Kokusai Chemical Co., Ltd.) was cast and cured for 2 hours. A considerable temperature increase was observed due to heat generated by the curing reaction. After curing, the mold was removed to obtain an epoxy resin molded product. After repeating this 10 times, the hardness and surface glossiness of the silicone rubber mold were measured to evaluate the changes.
[0047]
Example 2, Comparative Examples 1-3
According to the procedure similar to Example 1, the mold material of an Example and a comparative example was prepared by the mixing | blending shown in Table 1. FIG. However, in Comparative Examples 1 and 3 using A-2, A-2 was dissolved in A-1 in advance and used. Using these molding materials, the same replica production test as in Example 1 was performed. The results are summarized in Table 1 together with the results of Example 1.
[0048]
[Table 1]

[0049]
As is apparent from Table 1, the silicone rubber molds obtained in Comparative Examples 1 and 3 in which A-2 is used in combination with A-1 have a large change in hardness after casting the epoxy resin 10 times. Demolding became increasingly difficult. In addition, the glossiness of the mold surface decreased, and the resulting molded product also became rougher as the number of castings was repeated. On the other hand, the silicone rubber mold obtained in Comparative Example 2 using fumed silica surface-treated with hexamethyldisilazane did not have the required hardness. On the other hand, the silicone rubber molds obtained in Examples 1 and 2 have almost the same hardness and surface gloss even after 10 times of casting, and the appearance and transparency of the molded product are good. there were.
[0050]
Apart from this, the molding material obtained in Example 1 and Comparative Example 2 was poured into a mold and cured under the same conditions as described above to obtain a sheet having a thickness of 2 mm. From this, crescent-type test pieces were prepared according to JIS K6252, and the tear strength was measured. As a result, the test piece of Comparative Example 2 only had a tear strength of 8 N / mm [kgf / cm], whereas the test piece of Example 1 had a tear of 20 N / mm [kgf / cm]. Showed strength.
[0051]
【The invention's effect】
According to the present invention, there is provided a molding material that is cured to exhibit excellent release properties, improved mechanical properties, and a silicone rubber mold that exhibits excellent molding durability against a resin. The silicone rubber mold obtained from the molding material of the present invention has little change in hardness because there is no component that becomes a resin even after repeated molding, and the surface is rough, so the appearance and transparency of the molded product The durability of the rubber mold is great. In addition, it is not necessary to apply an external release agent during molding, and it is not necessary to add a non-reactive silicone oil to improve the releasability. There is no surface roughness associated with the transition. Therefore, it is particularly suitable for the production of a resin molded product that requires transparency and surface smoothness, such as a transparent epoxy resin molded product.
[0052]
The silicone rubber composition for molding according to the present invention is particularly useful in the field of molding that requires a high degree of releasability, such as molding of a transparent resin and prototype molding, taking advantage of the above-mentioned advantages.

Claims (1)

(A) 100 parts by weight of a linear polyorganosiloxane having two or more monovalent aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule;
(B) There are 3 or more hydrogen atoms bonded to a silicon atom in one molecule, or the number of monovalent aliphatic unsaturated hydrocarbon groups bonded to the silicon atom in (A) is 3 in one molecule. In the above case, the number of hydrogen atoms bonded to silicon atoms is 0.5 to 1 per one monovalent aliphatic unsaturated hydrocarbon group in the polyorganohydrogensiloxane (A) component having two or more. Amount to be 5;
(C) platinum compound 1 to 100 ppm by weight in terms of platinum atom with respect to (A); and (D) fumed silica surface-treated with 1,3-divinyl-1,1,3,3-tetramethyldisilazane It contains 5 to 50 parts by weight, does not contain a branched polyorganosiloxane having a monovalent aliphatic unsaturated hydrocarbon group bonded to a silicon atom, and does not contain a silicone oil that is not involved in crosslinking. A mold for transparent resin molding.