JPH0341045B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a silicone rubber molded product by integrally molding different types of silicone rubber. Regarding silicone rubber molded products, some are known that are made by combining two types of molded items with different shapes or two types of molded items with different properties such as conductivity and insulation. If it is a silicone rubber molded product, it can be easily made into an integral molded product by applying pressure and heating after that, but if the silicone rubber molded products are of different types, adhesion between the two,
There was a problem in that the fusion was insufficient and a satisfactory integrally molded product could not be obtained. That is, in order to integrate dissimilar rubber molded products, for example, a cured silicone molded product is inserted into a mold cavity, and then an uncured silicone rubber composition of a different type is placed therein. Either pressurize and heat to make an integrally molded product, or cut out a part of the uncured rubber molded product and insert a different type of uncured rubber there, then press and heat them to create an integrally molded product. However, in the former method, the adhesion between the two types of rubber molded products is insufficient, and in this case, the uncured rubber enters between the mold and the cured rubber, which is the so-called back side. This has the disadvantage that the integrated molded product has an unsightly appearance due to rotation, and in the latter case, since the fluidity of the two is the same when pressurized, not only will the joint surface of the two be disordered, but also the There is a disadvantage that the shape of the part is distorted (color shift), and furthermore, the work is complicated. Therefore, the present inventors first injected liquid addition-type silicone rubber into the recesses of a preheated mold, allowed it to partially cure to a non-flowing state under normal pressure, and then poured it into the mold. We developed a method in which a heat-curable silicone rubber composition containing a vulcanizing agent is charged, the mold is closed, and the mold is pressurized and heated to form an integrally molded product (see Japanese Patent Publication No. 63-44042). )
However, this method requires control of the semi-cured state of the liquid silicone rubber, and it is difficult to make the cured state uniform due to the relationship between the temperature of the mold and the reaction rate, and it may vary depending on the location. However, the problem was that the adhesion surface between the addition-type silicone rubber and the heat-curable silicone rubber of the molded product was disturbed, uneven coloring occurred, and the adhesion of that surface was also insufficient. The present invention relates to a method for manufacturing dissimilar silicone rubber molded products that solves these disadvantages.
In this process, a composition consisting of liquid addition-type silicone rubber and peroxide-cured liquid silicone rubber is injected into the cavity cavity of a preheated mold, and is partially cured to form a non-flowing material under normal pressure. After forming a mold into a shape, a heat-curing sulfurable silicone rubber composition containing a vulcanizing agent is charged into the mold, the mold is closed, and the mold is pressurized and heated to form an integrally molded product. That is. To explain this, the present inventors conducted research on a method for manufacturing an integrally molded product made of different types of silicone rubber, and found that a product containing the above-mentioned addition-type silicone rubber and an organic peroxide as a vulcanizing agent. In an integrally molded product with a heat-curable curable silicone rubber composition, if this liquid addition-type silicone rubber is mixed with a peroxide-vulcanized liquid silicone rubber, the temperature of the mold and the heating Since there is no need to control the time, etc., this method prevents irregularities and color unevenness on the bonding surface between the liquid silicone rubber and the heat-curing silicone rubber known as "Mirable". They found that the properties of the liquid silicone rubber were also improved, and conducted research on the composition, molding conditions, etc. of this liquid silicone rubber, and completed the present invention. The liquid silicone rubber used in the method of the present invention is a mixture of a liquid addition type silicone rubber and a liquid silicone rubber containing a peroxide vulcanizing agent. This addition type liquid silicone rubber may be a known one, and it is composed of an organopolysiloxane having an aliphatic unsaturated group bonded to a silicon atom in the molecule, such as a vinyl group (≡SiVi group), and It consists of an organohydrodiene polysiloxane that has a hydrogen group (≡SiH group) bonded to a silicon atom. twenty five
It has a viscosity of 300 to 500,000 cS at °C, and this means that when noble metals belonging to Group 3 of the periodic table, such as platinum, rhodium, palladium, or their compounds and complex salts, are added as a catalyst, the ≡SiH group The addition reaction of the SiVi groups is initiated, and as a result, the crosslinking reaction progresses, resulting in a cured product. The above-mentioned noble metal catalyst is blended into either of the ≡SiVi group-containing organosiloxane and ≡SiH group-containing organosiloxane that constitute this composition, and these are mixed at a predetermined mixing ratio during normal use. use a mixture of
It is commercially available as a so-called two-component composition, but
This compounding ratio is 0.8 to 8.0 for the ≡SiH group/≡SiVi group.
, preferably in the range of 0.8 to 3.0. The peroxide-vulcanized liquid silicone rubber compounded in this addition-type silicone rubber is dimethylpolysiloxane or dimethylmethylvinylpolysiloxane, organic peroxide, and if necessary fumed silica or silica as a reinforcing agent. Any material containing precipitated silica may be used. Examples of this organic peroxide include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, ditertiary butyl peroxide, tertiary butyl perbenzoate, 2,5-dimethyl-2,5-bis( Examples include t-butyloxy)hexane, which may be added in an amount of 0.1 to 5 parts by weight based on the organopolysiloxane. Regarding the blending ratio of the above-mentioned liquid addition type silicone rubber and peroxide vulcanized type liquid silicone, if the blending ratio of the latter is less than 20% by weight, the reaction rate will be slow and the molding time will be prolonged. This is 80% by weight
If the reaction rate is higher than this, the reaction rate is too fast, which tends to cause gel formation, and even causes poor adhesion to the millable. It is recommended that the range be within the range of . The production of the dissimilar silicone rubber molded product of the present invention is as follows:
First, the liquid silicone rubber composition described above is injected into the recessed cavity of the preheated mold. Using a nozzle, pour into the mold for 20~
It is preferable to carry out the test under pressure of 200 kg/cm ² . Also, in this case, the mold should be preheated to 50 to 180℃,
According to this, the liquid silicone rubber composition is incompletely cured in this mold and flows under pressure, but becomes non-fluid under normal pressure. Because it contains silicone rubber, the reaction rate is faster, the molding time is shortened, and even if the molded product obtained inside the cavity is completely cured, it has the effect of completely adhering to the millable after that. will be added. Note that the nozzle for injecting the liquid silicone rubber composition into the mold is used to prevent the press-fitted silicone rubber composition from remaining there until it solidifies or while the nozzle is removed from the lower mold. It is preferable to have a forced cooling mechanism to prevent the liquid silicone rubber composition from solidifying. In the method of the present invention, when the liquid silicone rubber in the lower mold is fluid under pressure but non-fluid under normal pressure, a heat-curable silicone rubber composition is added thereto. The heat-curable silicone rubber composition used here is an organopolysiloxane having a hydroxyl group, trimethylsilyl group, or dimethylvinylsilyl group at the end of the molecular chain. The material is not particularly limited, and may be a commercially available product generally called "mirable" which is prepared by blending a vulcanizing agent such as an organic peroxide with an organopolysiloxane having a functional group such as a vinyl group in the molecule. By this heating and pressurization, this heat-curable silicone rubber composition is cured by the action of the vulcanizing agent blended therein, but at this time, the solid molded product of the liquid silicone rubber composition is The material is co-vulcanized from a semi-cured state to a fully cured product by this vulcanizing agent, and by this simultaneous vulcanization, a molded article made from a liquid silicone rubber composition and a thermosetting silicone rubber composition are made. The resulting molded product is completely bonded to the molded product, resulting in an integrally molded product with no backing. The pressure and heating conditions vary depending on the type and viscosity of the heat-curable silicone rubber composition used here, but are usually 5 to 50 kg/cm ² , preferably 10 to 50 kg/cm 2 .
The vulcanization may be performed at a temperature of 30 Kg/cm ² and a temperature in the range of 120 to 200°C, and if necessary, secondary vulcanization may be performed at this temperature at 150 to 200°C. Next, this will be explained by a method using the molding apparatus of the present invention illustrated in the attached drawings.
The figure is a schematic vertical cross-sectional view of the apparatus used in the method of the present invention, Figure 2 is a vertical cross-sectional view showing the heated and pressurized state in the mold, and Figure 3 is a cross-sectional view of the heterogeneous silicone obtained by the method of the present invention.
1 is an example of a vertical cross-sectional view of a molded rubber product. The apparatus for producing dissimilar silicone rubber molded products of the present invention shown in FIG. Mechanism 3 , a pressurizable liquid silicone rubber container 5 for supplying the liquid silicone rubber composition 6 to this nozzle mechanism, an upper mold 7 for forming a thermosetting silicone rubber molded product, and heating the lower mold and the upper mold. It consists of a pressurizing device (not shown), and in the production of dissimilar silicone rubber molded products using this device, first, the nozzle mechanism 3 is fitted to the lower mold 1, and then the liquid silicone
The solenoid valve 8 between the silicone rubber container 5 and the nozzle mechanism 3 is opened, and pressure is applied from the upper part 9 of the container 5 to cause the liquid silicone rubber composition 6 to flow into the manifold 10 of the nozzle mechanism 3, and the liquid silicone rubber composition 6 is passed through its distribution hole. 11. When the liquid silicone rubber is press-fitted into the receiving recess 2 through the nozzle hole 12, it will flow under pressure but will not flow under normal pressure because the lower mold 1 has been preheated to 100-140°C, so it will be incompletely cured. to form a molded article 13. At this time, in order to prevent the liquid silicone rubber composition filling the manifold 10, distribution hole 11, and nozzle hole 12 of the nozzle mechanism 3 from solidifying due to the heat from the lower mold 1 , the cooling water inlet 14, It is cooled by a cooling mechanism 4 having an outlet 15. When the molded product 13 is obtained by solidifying the liquid silicone rubber composition, the solenoid valve 8 is closed, the nozzle mechanism 3 is removed from the lower mold 1 , and then a lump of heat containing a vulcanizing agent is placed on the lower mold 1 . Curable silicone rubber composition 16
As shown in Fig. 2, attach the upper mold 7 and heat it to 180-200℃, and release 10-30kg/
It is sufficient to co-vulcanize the thermosetting silicone rubber and the partially cured liquid silicone rubber by applying pressure to ^cm2 . Cured product 17 and thermosetting silicone
It is possible to obtain the desired dissimilar silicone rubber molded product 19 in which the cured product 18 of silicone rubber is integrally molded. In this case, either the liquid silicone rubber composition or the thermosetting silicone rubber composition may be electrically conductive, or a composition of a different color may be used. For example, the liquid silicone rubber composition may be a carbon It is said that if a black conductive composition is blended with black, etc., and a gray insulating composition is made of a thermosetting silicone rubber composition, it is possible to easily obtain a contact element for electronic components in which these are integrally molded. given an advantage. Next, examples of the method of the present invention will be given. In the examples, parts are parts by weight, and viscosity is a value measured at 25°C. Example Using the apparatus shown in Figure 1, 100 parts of addition-type liquid silicone rubber with a viscosity of 1000 cS, KE-1925 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed with 5 parts of a white pigment, Titanium White. and dimethylpolysiloxane with a viscosity of 10,000 cS and whose molecular chain ends are blocked with dimethylvinylsiloxy groups (vinyl group content: 0.3 mol%).
100 parts of fumed silica 30 with a specific surface area of 200 m ² /g
part, white pigment titanium white 5 parts and 2,5-
A peroxide-vulcanized liquid silicone rubber containing 0.5 part of dimethyl-2,5-his(t-butyloxy)hexane is mixed, and the volume formed by the concave part of the lower mold and the nozzle is 0.5cc is press-fitted into the cavity of 1c.c. under pressure of 10Kg/ ^cm2 , and this lower mold is
After heating to 170℃ for 1 minute, this silicone rubber is incompletely cured and becomes non-fluid under normal pressure, then the nozzle is removed, and then heat-curable silicone rubber KE-951U ( Shin-Etsu Chemical
Co., Ltd.'s product name] 100 parts and 2 parts of curing catalyst C-8 (product name of the company) was added, and 20 g was added, and after attaching an upper mold, the temperature was raised to 170°C, and a heating rate of 30 kg/cm ² was added. Heat treatment was performed for 5 minutes under pressure, the mold was opened, the molded product was taken out, and vulcanization was performed at 200℃ for 4 hours.
The resulting molded product had a beautiful horizontal surface on which the two types of rubber adhered, and was an integrally molded product in which the two types of rubber were completely adhered. However, the above mixture of liquid addition type silicone rubber KE-1925 and peroxide vulcanization type liquid silicone rubber was cured by heating at 130°C for 1 minute or
When the treatment was carried out in the same manner as in the above example except that the temperature was 100°C for 30 minutes, this curing reaction was observed for 1 minute.
If it is less than 10%, the silicone rubber will have an unsightly appearance, and if it is left for 30 minutes, the curing reaction will proceed too much and it will be almost completely cured, making it difficult to combine with thermosetting silicone rubber. Adhesion was poor and this product peeled off at the interface.

[Brief explanation of the drawing]

Fig. 1 is a schematic longitudinal cross-sectional view of an apparatus for producing dissimilar silicone rubber molded products used in the method of the present invention, Fig. 2 is a longitudinal cross-sectional view showing the heating and pressurizing state in the mold, and Fig. 3 is a main view of the present invention. 1 illustrates a longitudinal cross-sectional view of a dissimilar silicone rubber molded product obtained by the method of the invention. 1 ...lower mold, 2...liquid rubber receiving recess, 3 ...nozzle mechanism, 4...cooling mechanism, 5 ...liquid silicone rubber container, 7...upper mold, 10...manifold, 11...distribution hole, 12...nozzle hole, 19 ...Different types of silicone rubber molded products.

Claims (1)

[Claims] 1. A composition consisting of liquid addition-type silicone rubber and peroxide-vulcanized liquid silicone rubber is injected into the cavity recess of a preheated mold, and the composition is incompletely cured. After this, a heat-curable silicone rubber composition containing a vulcanizing agent is charged into the mold, and the mold is closed, pressurized, and heated to form a non-fluid state. A method for manufacturing a dissimilar silicone rubber molded product, characterized in that it is made into a molded product. 2 Liquid silicone rubber composition is addition type silicone
80 between silicone rubber and peroxide vulcanized silicone rubber:
The method for producing a dissimilar silicone rubber molded article according to claim 1, which is a blend of 20 to 20:80 (weight ratio).