JPH06329803A - Silicone product free from electrical contact failure - Google Patents

Abstract

PURPOSE:To provide a silicone product excellent also in a respect that it is free from electrical contact failure, having stable characteristics and capable of ready production at a low cost. CONSTITUTION:There is provided a silicone product free from generation of >0.1mg/L low-molecular siloxane in the gas phase in a tightly sealed state at practical working temperatures.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone product in which the amount of low-molecular-weight siloxane that volatilizes into the gas phase is suppressed below a specific amount. INDUSTRIAL APPLICABILITY The silicone product of the present invention is useful for electrical applications as it does not cause electrical contact failure due to low molecular weight siloxane.

[0002]

2. Description of the Related Art At present, as a method of preventing electrical contact failure due to low-molecular-weight siloxane, (1) use a commercially available silicone product provided with measures against electrical contact failure, and (2) switch to a material other than silicone. And so on. However, in (1), although some types of products are on the market, the standard is not clear. It also leads to cost increase when a wide range of operating temperatures is assumed. Furthermore, there is a silicone product group that has not yet been developed for electrical contact failure countermeasures. On the other hand, (2) has the same characteristics as silicone,
Moreover, it is difficult to find materials with the same level of price.

[0003]

In view of the above situation, the present invention provides a silicone product for preventing electrical contact failure, which is practically sufficient, but which is not subjected to excessive measures for cost increase. It was designed to be offered in all fields.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have aimed to suppress the amount of low-molecular-weight siloxane that volatilizes into the gas phase at the actual use temperature of silicone products to a specified amount or less. The present invention has been accomplished by finding that the above can be achieved. That is, the gist of the present invention is a silicone product in which the concentration of low-molecular-weight siloxane in the gas phase in a sealed state is set to 0.1 mg / L or less at the actual use temperature. The present invention will be described in detail below.

The silicone products of the present invention include all those used for electrical purposes such as silicone oil, silicone grease and silicone rubber. Silicone products usually contain low molecular weight siloxanes, which volatilize into the gas phase when the temperature rises and, when used in electrical products, adhere to electrical contacts and cause damage. Such low molecular siloxanes are essentially cyclic siloxanes. If internal ventilation is adequately performed during the operation of electrical products and electronic devices, it is considered that the occurrence of obstacles will be reduced, but in reality it is a difficult problem, and since ventilation is insufficient, the internal temperature Also rises. Therefore, volatilization of the low-molecular-weight siloxane at a considerably high temperature (actual use temperature) to which the silicone product is exposed without ventilation (closed state) becomes a problem.

Therefore, the present inventors have examined low molecular weight siloxane in the gas phase which is volatilized from a silicone product in a sealed state, and found that no trouble occurs if the concentration is 0.1 mg / L or less at each temperature. Of. For that purpose, as shown in FIG. 1, a low-molecular-weight siloxane D _{n having} a degree of polymerization of n or less that gives a concentration in the gas phase exceeding 0.1 mg / L by vapor pressure at a specified temperature (actual use temperature). (However, it is preferable to substantially remove the cyclic dimethylpolysiloxane D _n having a degree of polymerization of n, which occupies substantially the entire amount) from the silicone product. Removal methods include distillation under reduced pressure and / or heating, and in some cases extraction is possible. It is also effective to remove low-molecular-weight siloxane from the organopolysiloxane that is a raw material for silicone products in advance. Silicone products that can be heated, such as silicone rubber molded products, should be heat-treated in a post-process such as secondary vulcanization to substantially remove the prescribed D _n (residual amount less than 10 ppm each). ) Can be done.

[0007]

EXAMPLES Next, examples of the present invention will be described. Example 1 A micromotor was placed in a 10 L closed container, and an oscillograph for measuring a current waveform was connected thereto. The representative as octamethylcyclotetrasiloxane cyclic low-molecular siloxane (D _4: boiling point at 760mmHg is 175 ° C.)
Was added at various concentrations in the gas phase of a closed container. The micromotor was operated at each addition amount. condition is,
The DC condition is set as a load condition that is likely to cause contact trouble.
3V, 100mA. The oscillograph was observed to measure the time when the current waveform was abnormal and the time when the micromotor stopped. The result was as shown in FIG. The D ₄ concentration in the gas phase was measured by an analytical method using an activated carbon adsorption method and a pyrolysis gas chromatography [Analytical Chemistry, Vol. 40, T37 (1991)]. The results are shown on the vertical axis in FIG.

When the concentration of D ₄ in the gas phase is 1 mg / L, an abnormal waveform is observed almost immediately after the start of the micromotor operation.
Motor stopped in less than 100 hours. When the D ₄ concentration in the gas phase was 0.3 mg / L, waveform anomalies began to be observed after about 400 hours. When the D ₄ concentration in the gas phase was 0.1 mg / L, no abnormal waveform was observed even after 700 hours. From this result, the concentration of low-molecular-weight siloxane in the gas phase was 0.1 mg.
It was clarified that if / L or less, no trouble would occur.

Example 2 A micromotor was placed in a 10 L closed container, and Example 1 was used.
A test device exactly the same as above was prepared. 10 g of various silicone rubber products were put in the container, and the operation test of the micromotor was conducted in the same manner as in Example 1.

The silicone rubber product used is sample A
~ E of 5 types of press-molded products, which are obtained by performing press vulcanization (160 ° C x 5 minutes) only on these 5 types, and secondary vulcanization (200 ° C x 4 hours) after the press vulcanization. There are 10 types of molded products, each with a thickness of 2 mm. For each of these samples, each of the cyclic low-molecular-weight siloxanes D _n (n = 3 to 10) contained therein was measured. The results are shown in Table 1. The measurement was carried out by immersing 1 g of the sample in 10 ml of carbon tetrachloride for one day and subjecting the extract to gas chromatographic analysis.

Each of the above samples was put into a test apparatus and a micromotor operation test was conducted at 60 ° C. The results for the sample that was only press-vulcanized but not subjected to secondary vulcanization (removal of low-molecular-weight siloxane by heating) are as shown in Fig. 3. The higher the content of low-molecular-weight siloxane, the poorer the proportion of the content. The incidence was high. However, the vertical axis of FIG. 3 represents the failure rate (at oscillograph waveform abnormality or micromotor stop) (at n = 10). No defects occurred in the sample subjected to secondary vulcanization. Figure 1
Shows that the degree of polymerization is 9 (D ₉ ) at the actual use temperature of 60 ° C.
It can be seen that the following cyclic low-molecular-weight siloxane should be substantially removed. As shown in Table 1, according to the above-mentioned secondary vulcanization (heat treatment) conditions, such cyclic low-molecular-weight siloxane is The content has dropped to below 10 ppm and has been substantially removed. From these results, the effectiveness of controlling the D _n content so that the concentration in the gas phase becomes 0.1 mg / L or less is clear based on FIG.

[0012]

[Table 1]

Example 3 A trouble simulation using a micromotor was carried out in the same test apparatus equipped with a 10 L closed container as in Example 1. As the sample, a silicone rubber molded product recovered from a commercially available radio cassette in which a contact failure trouble occurred was used. First, the cyclic low-molecular siloxane (3 to 10 mer) contained in this sample was measured by the measurement method used in Example 2.
The measurement was performed on the as-collected sample, the sample heated at the temperature condition (60 ° C) actually used in the radio cassette for 24 hours, and the sample heat-treated at 200 ° C x 4 hours. The results are shown in Table 2. Next, put 20g (2g x 10 pieces) of the above sample into the test equipment and 60 ℃
At n = 5, the test was conducted. The results are as shown in FIG. 4, and when heat treatment was carried out at 200 ° C. for 4 hours, no defects occurred, and the effect of removing the cyclic low-molecular-weight siloxane (3 to 10 mer) is clearly recognized.

[0014]

[Table 2]

[0015]

EFFECTS OF THE INVENTION The silicone product of the present invention is set so that the concentration of low-molecular-weight siloxane in the gas phase in a hermetically sealed state is 0.1 mg / L or less at the actual use temperature, which causes electrical contact failure. The characteristics are excellent and stable in that there is no point. Further, the silicone product of the present invention can be obtained easily and inexpensively.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between n and temperature when the concentration of the low-molecular-weight siloxane D _{n in} the liquid phase coexists in a closed state at a concentration of 0.1 mg / L.

FIG. 2 is a graph showing the relationship between the concentration of D _{4 in the} gas phase, the time when an abnormality occurs in the current waveform when the micromotor is operated in this gas phase, and the time when the micromotor stops.

FIG. 3 is a graph showing a failure occurrence rate in an operation test of a micromotor in a coexisting sealed state of a silicone rubber molded product which was only press-vulcanized.

FIG. 4 is a graph showing a failure occurrence rate in a trouble simulation of a micromotor under coexistence of a silicone rubber molded product recovered from a commercially available radio cassette in which a contact failure trouble has occurred.

Claims (1)

[Claims] 1. A silicone product in which the concentration of low-molecular-weight siloxane in the gas phase in a sealed state is set to 0.1 mg / L or less at an actual use temperature.