JP3020386B2 - Silicone rubber composition for molding - Google Patents

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 composition for molding, and more particularly, to a molding material which requires a high degree of releasability, such as molding of a prototype model, ie, prototype molding. When used as
The present invention relates to a molding composition which is excellent in releasability of a molded article of a urethane resin or an epoxy resin as a duplicate from a silicone rubber mold obtained by curing, and in which the number of times of molding is remarkably improved.

[0002]

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, because of its good releasability, it has been used as a molding material. In recent years, attention has been paid to the fact that prototype molding used at the product development stage and product sample creation in the fields of electronic equipment, office machines, home appliances, automobile parts, etc. is effective in improving the cost and required period. In particular, in view of workability, addition-reaction-type liquid silicone rubber has been widely used.

[0003] 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.

[0004] In addition, in recent years, as the tendency to reduce the manufacturing cost of prototypes has become more intense, there has been a demand for a significant review and improvement of the number of times of molding and workability.

[0005] In order to solve such a problem, approaches have been made from both a system of a base polymer, a crosslinking agent and a catalyst 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 Laid-Open No. 7-222, a method of blending a cross-linking agent from which low molecular polyorganohydrogensiloxane is removed is exemplified.
No. 5,152, a method of blending a non-reactive silicone oil is exemplified. However, the former alone does not provide sufficient results with respect to the high required level imposed on the present invention, and the latter contains a large amount of silicone oil that does not participate in cross-linking. This is not preferable for some applications because the oil easily oozes out and the duplicates are stained due to oil seeping out. Further, Japanese Patent Application Laid-Open No. 50-66533 discloses that the releasability is improved by mixing a non-reactive silicone oil and titanium oxide with a condensation-reaction type liquid silicone rubber composition. However, in this case, there is a problem that the types and amounts of other fillers used in combination are limited.

Further, as a countermeasure in the work surface for molding a prototype, an external mold release agent is frequently applied to a mold. However, this method not only complicates the operation, but also requires the release agent to migrate to the surface of the obtained duplicate, and requires washing with an organic solvent or Freon when coating or plating the duplicate. Therefore, there is a risk of deteriorating the working environment and causing pollution, and it is necessary to take preventive measures.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to manufacture a duplicate product using a high-performance urethane resin or epoxy resin without contaminating the duplicate product as described above.
An object of the present invention is to provide a silicone rubber composition which is excellent in mechanical strength and releasability of a replicated product and which can be molded many times, and which is particularly suitable for molding requiring high releasability such as a prototype.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above-mentioned problems, and as a result, have determined that a specific constituent ratio of the filler to be mixed in the silicone rubber composition for molding is oxidized. By using titanium, it was found that the mold release performance of the duplicated product from the cured mold was remarkably improved, and the object of the present invention was achieved. Thus, the present invention was completed.

That is, the silicone rubber composition for molding of the present invention comprises: (A) 100 parts by weight of a polyorganosiloxane having two or more monovalent aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule. (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) a platinum-based compound, 1 to 1 in terms of platinum atom with respect to (A).
And (D) titanium oxide having an average particle size of 0.1 to 10 μm
An inorganic filler containing 40% by weight, characterized in that it contains 5-200 parts by weight and the amount of titanium oxide is 1-20 parts by weight.

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 groups include:
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 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 at the terminal or midway of the molecular chain of the polyorganosiloxane (A), or may be present at both.
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 of complex shapes such as for prototypes, use a mixture of linear polydiorganosiloxane and branched polyorganosiloxane. Is preferred. When these mixtures are used, in order to increase the mechanical strength and elastic modulus of the cured product, R ₃ SiO _1/2 units and Si
It is composed of an O ₂ unit and, if necessary, an R ₂ SiO unit (R represents the above-mentioned organic group, and at least two, preferably three or more in one molecule are a monovalent aliphatic unsaturated hydrocarbon group). 2 to 50% by weight of branched polyorganosiloxane
It is preferable to use a mixture of a polydiorganosiloxane which is blended and the balance of which is linear and whose both ends are blocked with a monovalent aliphatic unsaturated hydrocarbon group.

Although the degree of polymerization of component (A) is not particularly limited, it is necessary that the composition before curing has good fluidity and workability, and that the composition after curing has appropriate elasticity at 25 ° C.
Is preferably 500 to 500,000 cP, and particularly preferably 1,000 to 100,000 cP.

The polyorganohydrogensiloxane of the component (B) used in the present invention undergoes an addition reaction of the hydrosilyl group contained in the molecule 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. Moreover, you may use these mixtures.

The degree of polymerization of component (B) is not particularly limited, but it is difficult to synthesize a polyorganohydrogensiloxane in which two or more hydrogen atoms are bonded to the same silicon atom. Is preferred.

The following are specific examples of the component (B). a. A branched polyorganohydrogensiloxane comprising (CH ₃ ) ₂ HSiO _1/2 units and SiO ₂ units. b. The following formula:

[0021]

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(Where p represents an integer of 3 to 100; q
Represents an integer of 0 to 100). c. The following formula:

[0023]

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(Wherein p represents an integer of 1 to 100; q
Represents an integer of 0 to 100).

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 formed from the matrix. In this case, the releasability of the silicone rubber mold of the silicone rubber mold of the duplicated product obtained by molding is reduced. Conversely, when the abundance ratio is 5
If the amount exceeds the above range, foaming is likely to occur during curing, which accumulates at the interface between the mother mold and the silicone rubber mold and the interface between the silicone rubber mold and the replica obtained by molding, and In addition to giving bad molds and replicas, the obtained silicone rubber molds become brittle, resulting in a decrease in the number of times the resin is cast, that is, a decrease in the molding life, or a decrease in the mechanical strength of the mold. .

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

Examples of the platinum compound include chloroplatinic acid, a reaction product of chloroplatinic acid and an alcohol, a platinum-olefin complex, a platinum-vinylsiloxane complex, and a platinum-phosphine complex.

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

The component (C) is used in an amount of 1 to 100 ppm, preferably 2 to 5 ppm in terms of platinum atom, based on the 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 mother mold and the releasability of the copy from the silicone rubber mold are reduced.
If it exceeds 100 ppm, the curing speed becomes excessively high, so that workability after blending each component is impaired, and it is 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 those obtained by subjecting them to a surface treatment with a silicon compound such as polyorganosiloxane and hexamethyldisilazane;
Further, powders such as calcium carbonate, aluminum silicate, titanium oxide, zinc oxide, iron oxide, and carbon black are exemplified. The amount of the inorganic filler is 5 to 200 parts by weight in order to give the silicone rubber mold obtained by curing good mechanical properties.

A feature of the present invention is that 10 to 40% by weight of the above-mentioned inorganic filler as the component (D) is titanium oxide, and the amount of the titanium oxide is 1 to 20 parts by weight. Thereby, the silicone rubber mold obtained by curing the composition of the present invention can be provided with extremely good molding performance. This titanium oxide is made of TiO
_In general, a small amount of such a curable rubber composition as a white coloring pigment (in an inorganic filler,
(About 1 to 5%) in some cases, but in the present invention, it has been found that the above-described effects can be obtained by further increasing the amount of titanium oxide in the addition reaction type silicone rubber composition. .

As described above, the amount of titanium oxide is 1 to 20 parts by weight as titanium oxide and accounts for 10 to 40% by weight, preferably 15 to 40% by weight of the component (D). . If the content of the component (D) is less than 10% by weight or the amount of titanium oxide is less than 1 part by weight, the releasability of the silicone rubber mold obtained by curing is insufficient, and the releasability is rather reduced by adding a small amount of titanium oxide. In some cases. On the other hand, if it exceeds 40% by weight in the component (D) or exceeds 20 parts by weight as titanium oxide, the mechanical properties deteriorate,
Sufficient performance cannot be exhibited for molding.

There are two types of such titanium oxides, one is a sulfuric acid method and the other is a chlorine method. From the crystal structure, there are two types of rutile type and anatase type. In order to do so, a rutile type by a chlorine method is more preferable. Further, in order to obtain good releasability, which is the object of the present invention, the average particle size of titanium oxide needs to be 0.1 to 10 μm. 0.1
If it is less than μm, there is no effect of improving the releasability. Also 10
Even if it exceeds μm, not only the effect is not obtained but also the mechanical properties and surface condition of the silicone rubber mold obtained by curing the composition are adversely affected.

The titanium oxide can be used as it is, but is preferably a surface-treated with a cyclic polyorganosiloxane, a chain polyorganosiloxane or an organic silazane compound. Such an organic silazane compound is more preferable. The surface treatment can be performed according to a method for treating a general reinforcing silica filler. Titanium oxide (A)
The mixture after mixing with the component and / or the remaining component (D) can be subjected to surface treatment in the same manner as described above.

The amount of the component (D) is from 5 to 200 parts by weight, preferably from 10 to 100 parts by weight, based on 100 parts by weight of the component (A), on condition that the above-mentioned amount of titanium oxide is satisfied.
Parts by weight. If the amount is less than 5 parts by weight, sufficient mechanical properties as a molding material cannot be imparted to the composition after curing. If the amount exceeds 200 parts by weight, rubber elasticity and elongation are insufficient, and workability at the time of molding becomes poor. In addition, the mold may be damaged when removing the duplicate.

In the composition of the present invention, if necessary,
By blending an appropriate amount of a non-reactive oily polyorganosiloxane, the interaction between the oily polyorganosiloxane and the above-mentioned titanium oxide can further increase the releasability, and perform an effective molding operation. It is possible. This oily polyorganosiloxane has an average unit formula of R ¹ _a SiO
_{(4-a) / 2} , wherein R ¹ represents a methyl group or a phenyl group; a represents a number from 1.98 to 2.02; It does not need to be, and may be linear or branched.
000 cP, preferably 1,000 to 50,000
00cP. If the viscosity is less than 100 cP, the initial amount of bleed on the silicone rubber mold surface is large, and
Anything over cP has no effect.

The amount of the oily polyorganosiloxane is 15 parts by weight or less, preferably 1 to 10 parts by weight, per 100 parts by weight of the component (A). Compounding amount is 15
If the amount is more than 10 parts by weight, the amount of bleeding of the oily polyorganosiloxane on the surface of the silicone rubber mold becomes excessive, and the amount of the polyorganosiloxane adhering to the duplicated product increases. In addition, problems such as deterioration of the dimensional accuracy of the mold occur.

In order to prolong the curing time at room temperature of the silicone rubber composition for molding of the present invention and improve the workability, an acetylene compound, diallyl maleate, triallyl isocyanurate, a nitrile compound or an organic peroxide may be used. A curing retarder such as a product may be blended. In addition, pigments, plasticizers, and the like may be added as necessary.

In the composition of the present invention, the component group containing the component (B) and the component group containing the component (C) are usually stored separately, and the two components are uniformly mixed immediately before use. However, it is also possible to store all components in the same container in the presence of a setting retarder. Although curing can be performed at room temperature, curing may be promoted by heating up to 150 ° C. depending on conditions.

[0040]

According to the present invention, even when a non-reactive silicone oil is not blended, the composition cures, exhibits excellent mold release properties, and has an improved mechanical property. Thus, a silicone rubber composition which is a silicone rubber mold exhibiting excellent mold durability can be obtained. Silicone rubber mold obtained from the composition of the present invention,
There is no need to apply an external release agent at the time of molding. Furthermore, since there is no need to wash with a solvent before applying a coating or plating to the replica obtained using the silicone rubber mold, including the molding operation and all the accompanying operations,
The working time can be shortened and the cost can be significantly reduced.

The silicone rubber composition for molding of the present invention is particularly useful in the field of molding that requires a high degree of releasability, such as prototype molding, taking advantage of the above advantages.

[0042]

The present invention will be described more specifically with reference to the following 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 indicates a value at 25 ° C.

The polysiloxanes used in the examples and comparative examples are as follows. A-1: Polydimethylsiloxane having a viscosity of 3,000 cP, both ends of which are blocked with a dimethylvinylsilyl group A-2: Trimethylsiloxy unit, dimethylvinylsiloxy unit and SiO ₂ unit in a molar ratio of 3.5: 1: 5 .
B-1: a polymethylhydrogensiloxane containing 0.9% by weight of Si-H groups and having both ends capped with trimethylsilyl groups and having a viscosity of 20 cP F-1: both 10,000 cP polydimethylsiloxane end-blocked with trimethylsilyl group F-2: 100 cP polydimethylsiloxane end-blocked with trimethylsilyl group

Example 1 100 parts of A-1 and 10 parts of A-2 were used as base polymers.
Part, and Aerosil 200 as an inorganic filler.
(Product name, fumed silica, manufactured by Nippon Aerosil Co., Ltd.) 3
0 parts, 8 parts of rutile type titanium oxide powder having an average particle size of 3 μm surface-treated with hexamethyldisilazane, B as a crosslinking agent
-1 as 3 parts, and F as a non-reactive silicone oil
-1 was added and kneaded until uniform. Next, as a catalyst, a solution prepared by dissolving 1% by weight of chloroplatinic acid in isopropyl alcohol was blended in an amount of 20 ppm as platinum atoms with respect to the above base oil, kneaded and uniformly dispersed to obtain the composition of the present invention. Was prepared. The apparent viscosity of this composition was 50,000 cP, indicating fluidity that can be easily poured into a mold.

This was poured into a mold having a thickness of 2 mm and left at room temperature for 24 hours to obtain a sheet-like cured product. This sheet-shaped cured product was heated at 60 ° C. for 60 minutes to be completely cured.
The physical properties of this cured product according to JIS K6301 are as follows:
The hardness was 40 (JIS A), the tensile strength was 40 kgf / cm ² , the elongation was 350%, and the tear strength was 25 kgf / cm (JIS A).

Using the above-described composition as a mold material and the following urethane resin and epoxy resin as a resin for a prototype, a test of the molding performance of each resin was conducted. Urethane resin: Highcast 3075 (trade name, two package type, manufactured by Kokusai Chemical Co., Ltd.) Epoxy resin: CEP-5 (trade name, double package type, manufactured by Kokusai Chemical Co., Ltd.)

That is, height 10 cm, width 15 cm, height 10
A mold made of ABS resin is placed in a cm container, the composition is poured into the container so as to wrap it, and left at room temperature for 24 hours.
Then, it was heated at 60 ° C. for 2 hours. The matrix was removed from the cured product to obtain a silicone rubber mold. Using this silicone rubber mold, the above-mentioned prototype resin was injected and cured to obtain a duplicate. Then, repeat the creation of duplicates,
The number of times until the prototype resin adhered to the mold was examined.

Examples 2 to 4 and Comparative Examples 1 to 3 Example and comparative compositions having the formulations shown in Table 1 were prepared in the same manner as in Example 1. In Example 3, rutile-type titanium oxide powder having an average particle size of 3 μm was used without surface treatment. Using these compositions, a duplicate production test similar to that of Example 1 was conducted. Table 1 summarizes the results together with the results of Example 1.

[0049]

[Table 1]

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-18453 (JP, A) JP-A-49-97082 (JP, A) JP-A-2-151660 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C08L 83 / 07,83 / 05

Claims (1)

(57) [Claims] (A) 100 parts by weight of a polyorganosiloxane having two or more monovalent aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule; and (B) a hydrogen atom bonded to a silicon atom. A polyorganohydrogensiloxane having three or more per 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) a platinum-based compound, 1 to 1 in terms of platinum atom with respect to (A).
And (D) titanium oxide having an average particle size of 0.1 to 10 μm
An inorganic filler containing 40% by weight, a silicone rubber composition for molding containing 5-200 parts by weight and an amount of titanium oxide of 1-20 parts by weight.