JPS6023018A - Preparation of silicone rubber molded piece in high temperature region - Google Patents

Abstract

PURPOSE:To make possible dip molding in a high temperature region and to obtain the title molding uniform in thickness and quality by applying addition reaction hardening liquid silicone rubber compound containing inorganic filler with specified viscosity and pot life. CONSTITUTION:First, the viscosity and pot life of the additional reaction hardening liquid silicone rubber compound containing inorganic filler is controlled generally by means of hardening retarder and viscosity adjuster so that the viscosity of said compound at 250 deg.C is 10-1,000,000 centipoises and the pot life thereof is 30 days min. The mold in the region of 150-250 deg.C is dipped in said compound, preferably, for 1sec-10min, then, drawn up and a molded piece is released from the mold and obtained in the desired form. EFFECT:Foamless, stable molded pieces are obtained continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing silicone rubber molded products by dip molding in a high temperature region.

A method for manufacturing silicone rubber molded products by dip molding using a liquid silicone rubber composition is reported in the published patent publication (Sho sIl~//733O), but in the dip molding of this application. The mold temperature is 30°C
-taooa (preferably trooc -ljoo
C), and it is said that if it exceeds 1 qo0c, air bubbles will enter the layer of the molded product and the appearance will deteriorate.

The present inventors have succeeded in continuous molding of a stable silicone rubber molded product that can be molded in a high temperature range of is'o0c or higher, has uniform wall thickness and quality, and is free from bubbles.

In general, the curing mechanism of liquid silicone rubber compositions is addition polymerization of vinyl-terminated polysiloxanes and silicon- and hydrogen-containing polysiloxanes using a platinum catalyst, as shown in the following example. When these two liquids A and B are mixed, they have a bow drive of only about 2 days at room temperature, and are not suitable for molding methods such as dip molding, in which a large amount of resin liquid is retained for a long time.

In the present invention, by mixing a certain amount of a curing retarder and a viscosity modifier into an addition reaction-curing liquid silicone rubber composition containing an inorganic filler, Bowtry 7 can be cured for 30 days or more (, 2
50G), it became possible to perform continuous molding in a higher temperature range.

Viscosity change (u'a: centiboise) Quartz powder 9 parts Hardening retarder

According to the above-mentioned known technology, when molding is performed at a high temperature of 117,000 or higher, air bubbles remain in the layers of the molded product, resulting in poor appearance.

This is because excessive H-3 bonds such as crosslinking agents gradually cause a dehydrogenation reaction.

In the present invention, by delaying the start of curing, the dehydrogenation reaction is also suppressed and the generation of bubbles can be prevented. Furthermore, the effectiveness of the viscosity modifier is enhanced by using a polymer type organopolysiloxane, which does not have reactive groups such as vinyl groups or silicon-bonded hydrogen atoms, and does not easily undergo dehydrogenation or addition reactions.

In carrying out the present invention, the technique of dip molding, which is well known for polyvinyl chloride, was carried out, and the mold temperature was set to /j00c -2JO0Cj.

1. If it is less than tO00, curing will be extremely slow and 11m
Making the wall thicker than this is problematic. Moreover, if it exceeds 2j000, it becomes impossible to manufacture a product with a uniform thickness, and bubbles are likely to occur. The viscosity of the liquid silicone rubber composition is 10-i, ooo, ooo centiboise, preferably m-ioo, oo.

You need something with centiboise.

After the thus heated mold is immersed in the liquid silicone rubber composition for a predetermined period of time, it is pulled out and immersed in the liquid silicone rubber composition.
00-3j? The open bales are heated in a heating furnace at 000' for several seconds to several minutes. After this, the molded article can be completely cured by heating. Thereafter, the mold was demolded to obtain an elastic and homogeneous silicone rubber molded product. At this time, if the viscosity of the liquid silicone rubber composition is less than j'o, ooo centiboise, continuous molding for 7 to 10 days is possible.

At this time, the viscosity of the liquid silicone rubber composition after continuous molding for 7 days was about 10 QOOOO centivoids.

The most common materials for molds are aluminum rubber and brass, but steel can also be used.

By the method of the present invention, silicone rubber products such as various electrical insulation parts, wiring, material parts, automotive insulation parts, etc. can be easily manufactured.

Example/Viscosity ioo, ooo centivoise (g'
The following dip molding was carried out using the addition reaction curing liquid silico-rubber composition containing an inorganic filler and using a platinum catalyst (bow try 730 days at 2s0a) of a).

A cylindrical convex mold made of aluminum rubber (30 wn diameter x 1 s depth
ottan) was immersed in the composition at a speed of 7 seconds to a depth of IOo■, left in the composition for 9 seconds, then pulled up at a speed of wn/l> seconds, and then heated in a heating furnace at 3000C for 30 seconds to demold. A homogeneous and smooth cylindrical silicone rubber molded article with a wall thickness of 2III+ was obtained.

Example 2. Viscosity io, ooo centiboise (25'
The following dip molding was carried out using the addition reaction curing liquid silicone rubber composition containing an inorganic filler and using a platinum catalyst (Boutra 479 days at Δ0C) of a).

A mold α for an insulating sleeve for a continuous terminal made of brass as shown in the figure was heated to 11rO0C, immersed at a speed of 10w7M), heated in the composition for 3 seconds ia*, and demolded. After molding
When the sample was removed and the wall thickness was measured, a homogeneous, smooth, pinhole-free silicone rubber molded product with a thickness of /10I was obtained. In this molding, continuous molding was possible for 10 days in 7 days and 7 hours.

Example 3. Addition reaction curing liquid silicone rubber composition using a platinum-based catalyst containing an inorganic filler with a curing retardant of A3, a viscosity modifier of 75% by weight, and an ooo centiboise (Boutora 4F 40 in WOA).
The following dip molding was performed using

A conical brass mold J heated to 2RO0A was immersed in the above liquid silicone rubber composition to a depth of 2D■, and left in the composition for 15 seconds. When removed from the mold after heating, the wall thickness/mm
A homogeneous and smooth silicone rubber molded article was obtained.

[Brief explanation of drawings]

The attached drawings illustrate one aspect of the mold used in Embodiment 2 of the present invention. Figure 1 is a partially sectional front view, Figure 1 and Figure 2 are written amendments (voluntary), published in 1981. Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office/Display of the case Showa J1 patent application No. ≦! No. 177 No. 2 Name of the invention Method for manufacturing silicone rubber molded products in a high-temperature region 3 Relationship with the arrester case Description of the contents of the amendment to the left side of the specification M, subject of the amendment to the patent applicant Hiroshi m. Name: Method for manufacturing silicone rubber molded products in high temperature range 2, Claims (1) Viscosity at 25'O: 10 to 000.0
00*> A mold is immersed in an addition reaction curing liquid silicone rubber composition containing an inorganic filler, which has a pot life of 30 days or more, and has a temperature range of /JO00-koso'a, A method for manufacturing a silicone rubber molded product, characterized by pulling it up and demolding it. (2) The manufacturing method according to claim 1, wherein the addition reaction-curable liquid silicone rubber composition uses a platinum-based catalyst and contains a curing retarder and a viscosity modifier. (8) The manufacturing method according to claim 1, wherein the immersion time of the mold is 1 second to 10 minutes. (4) The manufacturing method according to claim 1, wherein the mold is a convex mold. (5) Immerse the mold and pull it up /ro'c-3zo
The manufacturing method according to claim 1, wherein the mold is removed by heating for 3 seconds to OO seconds in a heating furnace. 3. Detailed Description of the Invention The present invention is applicable to immersion in high temperature areas. The present invention relates to a method for manufacturing silicone rubber molded products by lv molding. A method for manufacturing silicone rubber molded products by dip molding using a liquid silicone rubber composition is reported in the published patent publication (Sho!;'l-//7.!;!;Otsu). In the dip molding of this application, the mold temperature is jo'o-/μo'a (preferably za000-/J□
It is said that if the temperature exceeds 111,000, air bubbles will enter the center of the molded product and the appearance will deteriorate. Therefore, the present inventors conducted extensive research on a method for manufacturing silicone rubber molded products that have uniform wall thickness and quality and do not contain air bubbles when molded in a high temperature range of 1jO0C or higher, and as a result, they have arrived at the present invention. . In general, the curing process for liquid silicone rubber compositions is the addition polymerization of vinyl-terminated polysiloxanes and silicon-bonded hydrogen-containing polysiloxanes using a platinum-based catalyst, as shown by example. When these two liquids A and H are mixed, the pot life is only about two days at most at room temperature, so it is not suitable for molding methods such as dip molding where a large amount of resin liquid is retained for a long time. . Therefore, in the present invention, a pot life of 30 days or more (ssoa) is achieved by, for example, mixing a curing retarder and a viscosity modifier in an addition reaction-curable liquid silicone rubber composition containing an inorganic photonic agent. This made it possible to perform dip molding in a high temperature range of 1so0a or higher. Viscosity change (Joc: centipoise) Curing retarder
X%/1otal **In the present invention, pot life refers to the time required for the initial viscosity to double. According to the above-mentioned known technology, when molding is performed at a high temperature of l≠θ°G or higher, air bubbles remain in the center of the molded product, resulting in poor appearance. This is because excessive H-8z bonds such as crosslinking agents gradually cause a dehydrogenation reaction. However, in the present invention, by using an addition reaction curing liquid silicone rubber composition having a pot life of 30 days or more, the dehydrogenation reaction is suppressed and the generation of bubbles can be prevented. Furthermore, the above effects can be further enhanced by using a viscosity modifier, such as a polymer system that does not easily undergo dehydrogenation or addition reactions, such as an organopolysiloxane that does not have reactive groups such as vinyl groups or silica-bonded hydrogen atoms. I can do it. In carrying out the present invention, the technique of dip molding, which is well known for polyvinyl chloride, was carried out, but the mold temperature was adjusted to /! ;0'G -230'O-/J If it is less than O'O, curing will be extremely slow and it will be difficult to make the wall thickness on the part. Moreover, if the thickness exceeds 2so0a, it becomes impossible to manufacture a product with a uniform thickness, and bubbles will occur. The viscosity of the liquid silico Δtam composition is to −i, oo
o, ooo centiboise, preferably W-100,00
One with 0 centipoise is required. . After the thus heated mold is immersed in the liquid silicone rubber composition for a predetermined period of time, preferably from 1 second to 10 minutes,
This is pulled out and placed in a heating furnace at 100 = 33000 for several seconds to several minutes, preferably from 3 seconds to 10 minutes, if necessary.
Post-heat for 0 seconds. After this, the molded article can be completely cured by heating. Thereafter, the mold is removed to obtain an elastic and homogeneous silicone rubber molded product. At this time, if the viscosity of the liquid silicone rubber composition is below jO,000 centivoices, continuous molding for 7 to 10 days is possible. At this time, the viscosity of the liquid silicone rubber composition after continuous molding for 7 days was approximately /q, 0.000 centivoice. The shape of the mold is preferably convex. The most common materials for molds are aluminum rubber and brass, but steel can also be used. According to the method of the present invention, silicone rubber products such as various electrical insulation parts, wiring, material parts, automotive insulation parts, etc. can be easily manufactured. Example t Viscosity 'II at 8°0: 100.0
00 centipoise, 02 heavy weight curing retardant, 3
The following dip molding was carried out using an addition reaction-curable liquid silicone rubber composition (pot life at Δ0C of 30 days) containing a platinum-based catalyst and containing % by weight of a viscosity modifier and an inorganic filler. A cylindrical convex mold (diameter J6wq,
was immersed in the composition to a depth of 10° at a rate of 3 cm/sec, left in the composition for 9 seconds, and then pulled out at a rate of 3 cm/sec.
When the mold was demolded by post-heating for X seconds in a heating furnace of 0.000 mm, a thick, homogeneous, smooth cylindrical silicone rubber molded product was obtained. Example 2. An addition reaction curing liquid silicone rubber composition using a platinum-based catalyst, which has a viscosity at ΔOa of 10,000 centivoids, contains a curing retardant of A2, a viscosity modifier of 10, and an inorganic filler ( ,u'
The following dip molding was performed using the pot (2479 days old) in a. m molds for insulating sleeves for continuous terminals of Shinchuko shown in the attached drawings were heated to 110°C, immersed at a rate of 10 steps/sec, and left in the above composition for J seconds, then j Wnn
The mold was pulled out at a speed of 1/2, and then heated for 9 seconds in a heating furnace at 30,000 °C to remove the mold. After the molding, the + was removed and the wall thickness was measured, and a homogeneous, smooth silicone rubber molded product with no pinholes was obtained. In addition, in this molding, continuous molding was possible for 10 days in 787 hours. Implementation 3. An addition reaction-curing liquid silicone rubber using a platinum-based catalyst that has a viscosity in Moo of s and ooo centipoise, contains a curing retardant of A3 Jujukei, a viscosity modifier of /j Jujukei, and contains an inorganic filler. Composition (x
The following immersion molding was carried out using the above liquid silicone rubber composition (with a pot life of 60 days). Leave it in the composition for seconds and then pull it up, 3 ooa
After heating in a heating furnace for 7 seconds, the mold was demolded and the wall thickness/m
A homogeneous and smooth silicone rubber molded article of n was obtained. BRIEF DESCRIPTION OF THE DRAWINGS The attached drawings illustrate a mold used in Example 2 of the present invention, with FIG. 1 being a partially sectional front view and FIG. 2 being a bottom view thereof. Procedure Amendment Written February 77, 1980 Manabu Shiga, Commissioner of the Patent Office Display of X Case Showa 5G Patent Application No. Otsu No. 5777 2 Title of Invention Method for manufacturing silicone rubber molded products in high temperature range 3.
Relationship with the case of the person making the amendment Patent applicant T, the date of the amendment order June 30, 1970 Application subject to the amendment Contents of amendment B (1) [procedural amendment submitted on June 30, 1980] "Application for correction attached to the document" should be deleted.゛(2) ``A patent application pursuant to the proviso to Article 3g of the Patent Act in the application form'' and ``Number of inventions stated in the claims'' are deleted. , -QQ-

Claims (1)

[Claims] (1) Viscosity at uoC is 10-/,000.0
Bowtry 7 is immersed in an addition reaction-curable liquid silicone rubber composition containing an inorganic filler for 30 days or more at a temperature of /30'O-11A-0'0 at a temperature of 0'00 cm, A method for manufacturing a silicone rubber molded product, which is characterized by removing the mold by pulling it open. (2) The manufacturing method according to claim 1, wherein the addition reaction-curable liquid silicone rubber composition uses a platinum-based catalyst and contains a curing retarder and a viscosity modifier. (3) The manufacturing method according to claim 1, wherein the immersion time of the mold is 1 second to 10 minutes. (4) The manufacturing method according to claim 1, wherein the mold is a convex mold. (6) Immerse the mold and open it to tsooa -3so0
The manufacturing method according to claim 1, wherein the mold is removed by heating in the heating furnace of (a) for 3 to 00 seconds.