JP2002338812A - Silicon rubber material for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for casting which material does not contaminate, when preparing a blocked item, the blocked item, is excellent in mechanical strength and releasability from a blocked item, suffers little hardness-change and surface-roughness even after repeated blockings, can increase the number of blockings and is suitable for a blocking needing a high releasability such as a prototype. SOLUTION: This material for casting contains (A) a polyorganosiloxane which has an aliphatic unsaturated hydrocarbon group bonding to a silicone atom and has hydroxide groups bonding to the silicone atom of not more than 200 ppm, (B) a polyorganohydrogensiloxane, (C) a platinum compound and (D) an inorganic filler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an addition-reaction type silicone rubber molding material, and more particularly, it requires a high degree of releasability such as molding of a prototype model, that is, prototype molding, by being cured into a rubber state. The present invention relates to a molding material which is used for molding and has excellent mold releasability of a molded product such as a urethane resin or an epoxy resin which is a duplicate product, and has remarkably improved the number of times of molding.

[0002] In the present invention, a molding material is a material which has fluidity in an uncured state over the entire periphery or a part of the surface of a mold, and is formed by casting or It is contacted by a method like coating, cured in that state,
An uncured material that forms a mold to be used for replication with resin or the like. Further, in the present invention, the term “releasability” is used as a term including not only the releasability of the cured mold from the original mold, but also the releasability of a replicated product from the obtained mold.

[0003]

2. Description of the Related Art Conventionally, silicone rubber has been widely used in various fields, taking advantage of its excellent heat resistance, cold resistance, and electrical properties. 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, and automotive parts, prototype molding used at the product development stage and product sample creation, etc.
Attention has been paid to the fact that it is effective in improving the cost and the required period. In particular, the addition reaction type liquid silicone rubber has come to be frequently used in terms of workability.

[0004] Silicone rubber using an addition reaction has favorable molding properties as a molding material. However, as the mechanical properties of urethane resin or epoxy resin used for molding a prototype are improved, the releasability from the silicone rubber mold is increased. Tend to worsen.

[0005] In addition to this, the tendency to reduce the manufacturing cost of prototypes has been further strengthened, so that a significant review and improvement of the number of times of molding and workability are required.

In order to solve such a problem, approaches have been made from both a base polymer, a cross-linking agent and a catalyst system involved in an addition reaction of a molding material and a compounding agent. The former is disclosed, for example, in JP-A-58-1935.
As disclosed in Japanese Patent Application Publication No. 7 (1994) -78, there is exemplified a method of blending a crosslinking agent from which low molecular polyorganohydrogensiloxane has been removed, and the latter is disclosed in JP-A-58-22.
No. 5,152, the method of blending a non-reactive silicone oil is exemplified. However, the former alone does not provide sufficient results with respect to the high requirements imposed on the present invention, and the latter involves mechanical mixing of silicone rubber molds in order to incorporate a large amount of silicone oil which does not participate in crosslinking. This is not preferable for some applications, because the strength tends to decrease, and the duplicates are stained due to oil seeping out. Also, Japanese Patent Application Laid-Open No. 50-66533 discloses that
It is disclosed that by adding a non-reactive silicone oil and titanium oxide to a condensation reaction type liquid silicone rubber composition, the releasability is improved, but in this case, the types of other fillers used in combination are disclosed. There is a problem that the amount is limited.

[0007] Japanese Patent Application Laid-Open No. 2-70755 discloses that when a silica treated again with hexamethyldisilazane is used as a filler for a polyorganosiloxane composition which is cured by an addition reaction type, a silicone obtained is obtained. It is disclosed that the rubber mold has excellent mechanical strength and excellent mold release durability. However, this method does not provide sufficient tear strength as a molding material.

Japanese Patent Application Laid-Open No. 7-33985 discloses that a titanium oxide having an average particle diameter of 0.1 to 10 μm is used as a part of a filler of a silicone rubber composition for molding which is cured by an addition reaction. It is disclosed that a molding material excellent in mechanical strength and releasability can be obtained without soiling. Since the silicone rubber mold obtained from the composition is colored by titanium oxide, a transparent rubber mold in which the state of the duplicate inside can be observed cannot be obtained.

Further, as a countermeasure in the work surface for molding a prototype, an external release agent is frequently applied to a mold. However, this method not only complicates the operation, but also requires a cleaning with an organic solvent when the release agent is transferred to the surface of the obtained duplicate, and the duplicate is coated or plated. Therefore, there is a risk that the working environment will deteriorate and pollution will occur, and it is necessary to take preventive measures.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high quality urethane resin or an epoxy resin for producing a duplicate product, which is excellent in mechanical strength and releasability of the duplicate product. It is an object of the present invention to provide a silicone rubber composition suitable for molding that requires a high degree of releasability, such as a prototype, in particular.

[0011]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have suppressed the content of hydroxyl groups bonded to silicon atoms, which are present in trace amounts in the base polymer. As a result, it has been found that the mold release performance of the replicated product from the cured mold is remarkably improved and the object of the present invention is achieved, and the present invention has been completed.

That is, the silicone rubber composition for molding of the present invention comprises: (A) two or more monovalent aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule, and 100 parts by weight of a polyorganosiloxane having a hydroxyl group content of 200 ppm by weight or less; (B) a polyorganohydrogensiloxane having three or more hydrogen atoms bonded to silicon atoms in one molecule.
(A) The number of hydrogen atoms bonded to a silicon atom is 0.5 to 5 for one monovalent aliphatic unsaturated hydrocarbon group in the component.
(C) Platinum-based compound (A) in terms of platinum atom 1
-100 ppm by weight; and (D) 5-100 parts by weight of an inorganic filler.

The polyorganosiloxane of the component (A) used in the present invention is a component serving as a base polymer of a molding material in the present invention. The component (A) is not particularly limited as long as it has two or more monovalent aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule and can form a network structure by an addition reaction. Such a thing may be used.

The monovalent aliphatic unsaturated hydrocarbon group includes
Vinyl, allyl, 1-butenyl, 1-hexenyl and the like are exemplified, but vinyl is preferred because it is easy to synthesize and does not impair the fluidity of the composition before curing or the heat resistance of the composition after curing. The groups are most advantageous.

Other organic groups bonded to the silicon atom of the component (A) include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl; aryl groups such as phenyl; 2
Aralkyl groups such as -phenylethyl 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 preferable because it is easy to synthesize and has an excellent balance of properties such as mechanical strength and fluidity before curing.

The monovalent aliphatic unsaturated hydrocarbon group may be present either at the terminal of the molecular chain of the polyorganosiloxane (A) or at an intermediate position thereof, or may be present at both of them.
In order to give the cured composition excellent mechanical properties,
In the case of a straight chain, it is preferably present at least at both ends.

The siloxane skeleton may be linear or branched. In order to improve the mechanical properties of the cured composition and use it for molding a complicated shape such as for a prototype, it is preferable to use a mixture of a linear polydiorganosiloxane and a branched polyorganosiloxane. However, when used for casting epoxy resins, particularly transparent epoxy resins requiring surface smoothness, the presence of branched polyorganosiloxane increases the hardness of the silicone rubber mold due to its resinification. It is not preferable because of the loss of smoothness. When the mixture as described above is used, in order to increase the mechanical strength and the elastic modulus of the cured product, it is necessary to include R in the polyorganosiloxane of the component (A).
₃ SiO _1/2 unit and SiO ₂ unit and, if necessary, R ₂ SiO unit (R represents the above-mentioned organic group, and at least two, preferably at least three in one molecule are monovalent aliphatic unsaturated carbon atoms. 2 to 40% by weight of a branched polyorganosiloxane consisting of
It is preferable to use a mixture of polydiorganosiloxanes whose both ends are blocked with a monovalent aliphatic unsaturated hydrocarbon group.

The polymerization degree of the component (A) is such that the composition before curing has good fluidity and workability, and the composition after curing has a viscosity at 25 ° C. of 0.1 in order to have an appropriate elasticity. 5-
500 Pa · s [500 to 500,000 cP] is preferable, and 1 to 100 Pa · s [1,000 to 100,000 cP] is particularly preferable.

The silicone rubber molding material of the present invention is characterized in that the amount of hydroxyl groups bonded to silicon atoms, which is present in a small amount in the component (A), is 200 ppm by weight or less, preferably 0 to 150 ppm, as a whole of the component (A). Ppm by weight, more preferably 0 to 100 ppm by weight. By using such a component (A), adhesion to the casting resin is suppressed, and the number of times of molding the resin can be significantly improved.

In the case of a linear polyorganosiloxane, such a hydroxyl group bonded to a silicon atom is used as a polymerization catalyst in the ring-opening copolymerization of a cyclic siloxane with a terminal-stopping siloxane having a monofunctional siloxane unit. Depending on the selection and polymerization conditions, the terminal blocking reaction is not completely performed, and a trace amount is formed in the terminal siloxane unit. Further, in the case of a branched polyorganosiloxane, the polysiloxane is usually an organoalkoxysilane or an organochlorosilane, which is a raw material of a 1-3 functional siloxane unit, and when it contains a tetrafunctional siloxane unit, Alkyl silicate as raw material or its partial hydrolysis condensate,
Alternatively, it is obtained by co-hydrolysis and condensation with sodium silicate, but when the condensation reaction does not proceed sufficiently, a hydroxyl group bonded to a silicon atom is formed. The amount of such hydroxyl groups may reach 300 ppm by weight or more for a linear polyorganosiloxane and 600 ppm by weight or more for a branched polyorganosiloxane.

As a method for reducing the hydroxyl group bonded to the silicon atom to a limited range, for example, there is a method of treating the component (A) with a silylating agent. Hexamethyldisilazane, 1,3-divinyl-
Examples include silazanes such as 1,1,3,3-tetramethyldisilazane; silylamines such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; silazanes are preferred. During the silylation reaction,
Organoalkoxysilanes may be used in combination.

The amount of the hydroxyl group bonded to the silicon atom in the component (A) is determined by, for example, the Karl Fischer method using a chloroform-methanol mixture as a solvent.
The total amount of water and hydroxyl groups occluded in the siloxane is measured, and then the water content is measured by the Karl Fischer method using a pyridine-ethylene glycol mixture as a solvent, and the difference is determined as the amount of hydroxyl groups. be able to.

In the polyorganohydrogensiloxane of the component (B) used in the present invention, the hydrosilyl group contained in the molecule undergoes an addition reaction to the monovalent aliphatic unsaturated hydrocarbon group in the component (A). Thus, it functions as a crosslinking agent for the component (A), and has at least three hydrogen atoms bonded to silicon atoms involved in the addition reaction in order to form a cured product into a network.

Examples of the organic group bonded to the silicon atom of the siloxane unit include the same organic groups as those described above other than the monovalent unsaturated aliphatic hydrocarbon group in the component (A). From the standpoint of ease, a methyl group is most preferred.

The siloxane skeleton in the component (B) may be linear, branched or cyclic. A mixture of these may be used, but a linear one is preferred.

Although the degree of polymerization of component (B) is not particularly limited, it is difficult to synthesize a polyorganohydrogensiloxane in which two or more hydrogen atoms are bonded to the same silicon atom. The viscosity at 25 ° C. is more preferably from 15 to 200 mPa · s [15 to 200 cP] because the material is easy to handle and does not volatilize during storage and during heating for the curing reaction.

The amount of the component (B) is 1% in the component (A).
The amount is such that the number of hydrogen atoms bonded to silicon atoms in the component (B) is from 0.5 to 5, preferably from 1 to 3, per one unsaturated aliphatic unsaturated hydrocarbon group. If the amount of the hydrogen atoms is less than 0.5, the curing is not completely completed, so that the mold obtained by curing the composition becomes tacky, and the silicone rubber mold is molded from the original mold. In this case, the mold releasability and the releasability of the duplicate product obtained by molding from the silicone rubber mold are reduced. Conversely, when the abundance ratio is 5
When the amount exceeds the above range, foaming is liable to occur during curing, which accumulates at the interface between the prototype and the silicone rubber mold and the interface between the silicone rubber mold and the replica obtained by molding, resulting in a good surface condition. Not only do not give a mold or a duplicate, but also the obtained silicone rubber mold becomes brittle, resulting in a decrease in the number of times of resin injection, that is, a decrease in the mold life, or a decrease in the mechanical strength of the mold.

The platinum compound (C) used in the present invention promotes the addition reaction between the monovalent aliphatic unsaturated hydrocarbon group in the component (A) and the hydrosilyl group in the component (B). The catalyst is excellent in that it has good catalytic ability for the curing reaction at around normal temperature.

As the platinum compound, chloroplatinic acid, a complex obtained by reacting chloroplatinic acid with an alcohol, platinum-
Olefin complex, platinum-vinylsiloxane complex, platinum-
Examples include a ketone complex and a platinum-aldehyde complex.

Of these, a reaction product of chloroplatinic acid and an alcohol, a platinum-vinylsiloxane complex, and the like are preferable from the viewpoints of good solubility in the components (A) and (B) and excellent catalytic activity.

Component (C) is used in an amount of 1 to 100 ppm, preferably 2 to 5 ppm, as platinum atom, based on component (A).
It is 0 ppm. If it is less than 1 ppm, the curing speed is slow,
Since the curing is not completely completed, the silicone rubber mold becomes tacky, and the releasability of the silicone rubber mold from the original mold and the releasability of the replicated product from the silicone rubber mold are reduced.
If it exceeds 100 ppm, the curing speed will be excessively high, so that the workability after blending each component will be impaired, and it will be uneconomical.

The inorganic filler (D) in the present invention imparts mechanical properties to the cured product of the composition. Examples of such materials include silica powders such as fumed silica, precipitated silica, fused silica, crushed quartz, and diatomaceous earth, and polyorganosiloxanes, hexamethyldisilazane, 1,3-divinyl-1,1 And surface-treated with a silicon compound such as 3,3,3-tetramethylsilazane; and powders such as calcium carbonate, aluminum silicate, titanium oxide, zinc oxide, iron oxide and carbon black. To obtain good mechanical properties, fumed silica is preferred, and fumed silica surface-treated with silazanes such as hexamethyldisilazane is more preferred.

The amount of the component (D) is from 5 to 100 parts by weight per 100 parts by weight of the component (A), since the silicone rubber mold obtained by curing has good mechanical properties. Parts by weight are preferred.

Other components can be added to the silicone rubber molding material of the present invention according to the purpose within a range not to impair the features of the present invention. That is, in order to improve the workability by extending the curing time at room temperature of the silicone rubber molding material of the present invention, such as an acetylene compound, diallyl maleate, triallyl isocyanurate, a nitrile compound or an organic peroxide. A curing retarder may be included. Further, if necessary, a release agent, a pigment, a plasticizer, a flame retardant, a thixotropic agent, a bactericide, an anti-binder, and the like may be added.

The silicone rubber molding material of the present invention comprises:
It can be prepared by uniformly kneading the components (A) to (D) and other components blended as required by a mixing means such as a universal kneader or a kneader.
Usually, the component group containing the component (B) and the component group containing the component (C) are separately prepared and stored, and the two components are uniformly mixed immediately before use before use. It is also possible to store all components in the same container in the presence of a retarder.

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 prototype, or A silicone rubber mold is produced by casting or applying to a part of the surface and curing. Curing is possible by slightly heating from room temperature to about 60 ° C,
Curing may be accelerated by heating to 150 ° C. depending on the 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 duplicate.

[0037]

The present invention will be described more specifically with reference to reaction examples, examples and comparative examples. The present invention is not limited by the examples. In the following examples and comparative examples, parts represent parts by weight, and the viscosity indicates a value at 25 ° C.

The polysiloxanes used in Reaction Examples, Examples and Comparative Examples are as follows. A-1a: Both ends are blocked with a dimethylvinylsilyl group, the intermediate unit is a dimethylsiloxy unit, and the viscosity is 10
A-2a: containing a trimethylsiloxy unit, a dimethylvinylsiloxy unit and a SiO unit in a molar ratio of 5: 1: 8, Pa.s {10,000 cP} linear polymethylvinylsiloxane, hydroxyl content 290 ppm; Branched polymethylvinylsiloxane, hydroxyl content 320 ppm (used as a 60% by weight xylene solution); B-1: both ends are blocked with dimethylhydrogensiloxane, and an average of 12 dimethylsiloxy units in the middle;
And a linear polymethylhydrogensiloxane having an average of 9 methylhydrogensiloxy units.

Reaction Example 1 1,000 parts of A-1a was charged into a reactor equipped with a stirrer, a heater, a decompression device, and a reflux condenser.
-Divinyl-1,1,3,3-tetramethyldisilazane (3 parts) was added, and the mixture was heated at 80 ° C. for 3 hours while stirring.
The silazane compound was reacted with the terminal hydroxyl group of -1a.
The amount of the silazane compound was about 2 mol per 1 mol of the terminal hydroxyl group of A-1a. After completion of the reaction, the mixture was heated to 150 ° C. under reduced pressure to remove unreacted silazane compounds and by-products, thereby obtaining A-1b. A-1 obtained
The amount of the hydroxyl group bonded to the silicon atom in b is 40 ppm by weight.
Met.

Reaction Example 2 In place of A-1a, 1,000 parts of a 60% by weight xylene solution of A-2a was used, and 1,3-divinyl-1,1,3,3
Except that the amount of 3-tetramethyldisilazane was 2 parts,
The same reaction as in Reaction Example 1 was performed, and the purification step was omitted.
A 60% by weight xylene solution of 2b was obtained. The amount of the hydroxyl group bonded to the silicon atom in A-2b was 50 ppm by weight.

Example In a kneader, 100 parts of A-1b obtained in Synthesis Example 1 was added.
The 60% xylene solution of A-2b obtained in Synthesis Example 2 was
9 parts as A-2b and 25 parts of fumed silica having a specific surface area of 300 m ² / g, which had been surface-treated with hexamethyldisilazane, were charged and kneaded for 4 hours while heating to 150 ° C. The system was evenly dispersed. Then, the pressure was reduced to remove xylene, the mixture was allowed to cool, 2.4 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 to the component (A). Kneaded by adding 18 ppm to the total amount,
A molding material of the present invention was prepared. The apparent viscosity of this molding material was 50 Pa · s {50,000 cP}.

A mold made of ABS resin is placed in a container, and the above-described molding material is poured in contact with the mold so as to wrap the mold, and the mold is left at 25 ° C. for 24 hours, and then heated to 60 ° C. for 2 hours. After curing, the prototype was removed to obtain a silicone rubber mold.

Preheat this silicone rubber mold to 60 ° C.
A urethane resin high cast 3075 (two packaging type, trade name of International Chemical Co., Ltd.) was cast, cured for 2 hours, and demolded to obtain a duplicate. By repeating this, the moldability of the rubber mold was evaluated by the number of times until the resin adhered to the mold.

Comparative Example A comparative example was carried out in the same manner as in Example except that A-1a and A-2a used as the raw materials of Synthetic Examples 1 and 2 were used instead of A-1b and A-2b, respectively. Example mold materials were prepared. Using these molding materials, a duplicate production test similar to that of the example was performed. Table 1 summarizes the results together with the results of the examples.

[0045]

[Table 1]

[0046]

Industrial Applicability According to the present invention, there is provided a molding material which can be cured to obtain a silicone rubber mold exhibiting excellent mold release properties, improving mechanical properties, and exhibiting excellent molding durability against resin. You. The silicone rubber composition for molding of the present invention,
Taking advantage of the above advantages, it is particularly useful in the field of molding that requires a high degree of mold release, such as urethane resin molding and prototype molding.

Claims (1)

[Claims] 1. (A) The compound has two or more monovalent aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule, and the content of the hydroxyl group bonded to the silicon atom is 200 ppm by weight or less. (B) a polyorganohydrogensiloxane having three or more hydrogen atoms bonded to a silicon atom in one molecule;
(A) The number of hydrogen atoms bonded to a silicon atom is 0.5 to 5 for one monovalent aliphatic unsaturated hydrocarbon group in the component.
(C) platinum-based compound (A) 1 to platinum atom equivalent
100% by weight; and (D) 5 to 100 parts by weight of an inorganic filler.