JPS61127654A - Cyrindrical mica composite material and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a composite material containing mica.

BACKGROUND OF THE INVENTION Cylindrical bodies containing mica have been used for many years as electrically insulating structures such as standoffs. Typically such mica cylinders are formed by impregnating a mica sheet with a polymeric binder, then wrapping the sheet around a mold, and then heating the sheet to cure the binder and form the cylinder. It is a composite structure. Such structures have good dielectric strength and thermal stability and are relatively low dust. However, such mica cylinders are susceptible to deterioration by moisture, break relatively easily, are not necessarily uniform in thickness, or are not necessarily dimensionally stable at high temperatures. Furthermore, such cylindrical structures have poor strain resistance and are relatively poorly machinable.

Therefore, what is needed in the art is a mica composite cylinder that overcomes the various problems discussed above.

SUMMARY OF THE INVENTION The present invention provides an organic titanate containing about 1 to 4 wt% and about 0.5 wt% of an organic titanate.
~2wt% of metal naphthenates.
The present invention relates to a relatively dense mica cylinder comprising one or more mica papers impregnated with 4 wt% polysiloxane binder. The mica cylinder of the present invention has superior moisture resistance, thermal stability, dimensional stability, strength, and strain resistance compared to conventional mica cylinders. Further, the cylindrical body of the present invention has scratch resistance and excellent machinability.

One aspect of the invention is to impregnate a mica paper with about 5-20 wt% polysiloxane binder containing about 1-4 wt% organic titanate and about 0.5-2 wt% metal naphthenate; The impregnated mica paper is wrapped around the mold, and the binder is densified and hardened under the pressure and temperature that the mica paper is held in, thereby forming a cylindrical body with excellent moisture resistance. This is a method for forming an excellent cylindrical body as described above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

BEST MODE FOR CARRYING OUT THE INVENTION In this specification, the term cylindrical body or cylindrical shape is not limited to a structure having a closed curved cross section, but can also refer to a structure having an arbitrary polygonal cross section. This includes:

The mica paper used in the practice of this invention may be any conventional continuous thin mica paper, but mica papers formed from muscovite or phlogopite are preferred. The material chosen will depend on the properties required in the final product. Typically, muscovite is used when high dielectric properties are required, and phlogopite is generally selected when high temperature properties are required. The mica paper is in the form of conventional underwater decomposed mica paper formed using conventional methods. The thickness of the mica paper ranges from about 50.8 to 508 microns, with about 127 microns being preferred.

The binder used to form the mica paper can be any of the thermally crosslinkable silicone polymer systems used to form other mica papers. The polymer system chosen depends on the properties required of the final mica paper. Many mica papers are used in high temperature environments (
Since the binder used is preferably thermally stable at such high temperatures, the preferred polymer system is [)OWCo.
rnlno4-3136, [)ow Cornlr+
o2104 or 2105 or 2106 by Dow Corning Corporation located in Midland, Michigan, USA.
It is methyl phenyl polysiloxane or methyl polysiloxane sold by On. These polymers typically have temperatures below about 400°C (at 204°C) to about 500°C.
It cures at temperatures below (260°C) or higher and once cured is thermally stable to humidity up to about 1000'F (538°C). The polysiloxane systems used in the practice of this invention must not condense or outgas excessively during curing. This is because such phenomena cause the formation of water bubbles and pores in the mica paper, resulting in the formation of defective mica paper.

Kenrich Petrochemicals, Bayonne, New Chassis, U.S.A.
Any compatible organic titanate may be mixed with the polymer system in the range of about 1 to 4 wt% (with about 2 wt% preferred), including neoalkoxy titanates sold by etrOchelicals Ino, Inc.). The most useful titanates are those that are soluble in the polymer system, ie, polysiloxane, and that do not promote rapid cross-linking of the polymer, which shortens the shelf life of the polymer system. Whether titanates undergo rapid cross-linking depends on the manufacturing method used to form the cylinder. Rapid cross-linking is tolerated when rapid manufacturing methods are employed, but inferior products are formed when slower manufacturing methods are employed. Some typical titanates are shown in Table 1 below, with the preferred titanates being those of the monoalkoxy pyrophosphate titanate family.

Table 1 Isopropyl triisostearoyl titanate Isopropyl trimethacrylic titanate Isopropyl triacrylic titanate Isopropyl tri(tetraethylenetriamino) titanate Isopropyl tri(dioctyl phosphate) titanate Isopropyl tri(dioctyl pyrophosphate) titanate tri( Butyl octyl pyrophosphate) isopropyl titanate mono(dioctyl hydrogen phosphite) titanate tetraisopropyl di(tridecyl phosphite) titanate neoalkoxy triisostearoyl titanate neoalkoxy dodecylbenzenesulfonyl titanate neoalkoxy - Tri(dioctyl phosphate) titanate neoalkoxy tri(diodel pyrophosphate) titanate soap dryers and similar ordinary metal naphthenate dryers contain approximately 0.5 to 2 wt% of the base polymer (
(preferably about 1 wt%) to the pace polymer. Examples of such metallic soap dryers are manganese naphthenate, zinc naphthenate, tin naphthenate, cobalt naphthenate, and the like. It is believed that the addition of these naphthenate driers in conjunction with titanates improves the moisture resistance of mica papers without degrading other properties.

Solvents commonly used as carriers for binders are organic solvents, which can be either aliphatic or aromatic, with toluene or xylene being preferred. Solvents must be selected to be compatible with all components of the binder. The amount of solvent is not critical and generally ranges from 40 to 60% of the total volume of the solution.

A binder solution containing the above-mentioned components to be applied to mica paper is typically formed as follows.

It should be noted that the order in which each component is added is important in this case. The titanate must be added first, then the naphthenate, and then the polysiloxane. This order is desirable because it allows for better dissolution of the ingredients.

First, a solvent is placed in a container to form a binder. Titanate is then added to the solvent and the mixture is stirred until the titanate is dissolved and the solution is clear.

Typically this process is carried out at temperatures below about 60-80°C (15-30°C)
The test is carried out at an ambient temperature of While the solution is being stirred, a naphthenate drier is added to the solution and the solution is stirred until the drier is dissolved. This step also takes place at ambient temperature. The polysiloxane is then added to the solution thus obtained and the mixture is stirred until it is homogeneous, typically at ambient temperature for about 30 minutes to 1 hour. In this case, the polysiloxane is added in such an amount that when the solvent is removed, the correct concentration of titanate and naphthenate is achieved.

The mica paper is then unwound from the roll and placed on a flat surface, ie, a table, conveyor belt, etc., and the mica paper is impregnated with the binder by any conventional method, such as dipping. The amount of binder applied is such that the final cylinder contains about 5-14 wt% binder, and the binder application is such that the binder is evenly distributed throughout the mica paper. must be done. Other conventional impregnation methods of applying binder to mica paper may be employed, such as dipping, roll-soaking, spraying, and brushing (some methods involve applying binder to both sides of the mica paper). desirable.

The aromatic solvent present in the binder is then removed by exposing the mica paper and binder to a temperature high enough to evaporate the solvent, but not high enough to polymerize the polymer. Typically the temperatures mentioned above are about 250-27
5 below (121-135°C). Typically, this step is performed by passing the mica paper through an oven or by exposing the mica paper to radiant heat. The mica paper is then cooled to ambient temperature, thereby forming a relatively rigid paper sheet.

In addition to the methods described above, mica paper impregnated with binder can be made to distribute the binder more evenly throughout the mica paper and to densify it before forming it into a cylinder under heat and pressure. It may be further processed. Typically, this process is carried out at a temperature of about 200-275° C. (93.3-135° C.) under sufficient pressure to flow the polymer throughout the mica paper. Also, the pressure is generally 6.89 to 31.04
It is in the range of bar. This step may be carried out in a conventional press. The time that the mica paper is pressed and the pressure and temperature at which this step is carried out may be varied depending on the thickness of the mica paper and the amount of polymer present and the polymer system used (more on this later). (See example for discussion).

The mica paper is then heated to about 350-400'F (176,6
~204°C). This step may be performed by placing the mica paper on a heated platen or platen placed below a heat source, ie, an infrared lamp, or by passing the mica paper through an oven. Since the above-mentioned temperature is above the polymerization temperature of the polymer, this heating step must be carried out quickly so that the polymerization does not proceed to such an extent that the mica paper cannot be rolled. Typically, only a few minutes (1-1.5 minutes) are required to soften the mica paper to a sufficiently flexible state, depending on the thickness of the mica paper and its state of cure.

Determining whether the mica paper has become sufficiently flexible is
This may be done by testing the flexibility of one corner of the B matrix.

If the mica paper bends easily, the mica paper is sufficiently flexible. The optimum conditions, ie, temperature and time, vary depending on the type of polymer system and the thickness of the mica paper, so the optimum conditions must be determined on a case-by-case basis.

When the mica paper becomes flexible, ie thermoplastic, it is formed into a tube. Typically this process is done by wrapping the softened mica paper around the mold. This step may also be performed by hand rolling, or conventional rolling equipment may be used.

An example of the winding process using such a rolling device is shown in the attached figure, in which the rolling device (winding machine) 1
0 has a belt 20 wrapped around a roller 25, and the belt 20 passes over the heated surface of a platen 30 with mica paper 40 placed thereon. A shaft 50 coated with a release agent, i.e. Teflon, silicone, etc., is disposed in a curved portion 55 of the belt 20 so that the mica paper will not move around the shaft 50 as the belt 20 passes around the shaft 50. It can be wrapped around. The bend 55 in the belt may be formed by positioning the londo to maintain the belt in contact with the shaft 50 for a sufficient period of time to wrap the mica paper around the shaft 50. A tube of mica paper of the desired thickness is formed by wrapping a series of mica papers around a shaft or by wrapping a continuous sheet of mica paper around a shaft. There is no need for a tensile force to be applied to the mica paper when it is wrapped around the shaft. The mica paper need only be under enough tension to form a structure with the desired configuration and relatively smooth, clean appearance.

If the thickness of the mica paper is about 127μ or less, or if the amount of polymer is small, such as about 7% or less, the inside of the mica paper ( An additional layer of adhesive may be applied (the part in contact with the shaft). This improves the adhesion between the layers of the tube,
A better and more stable tubular structure is formed. The wall thickness of such cylinders is generally about 0.025 to 2.54 cm.

Once the tube is formed, lower the tube by approximately 392-1000 (200
The polymeric binder is cured by heating to 537.8° C.) to cross-link the binder. This process is typically performed in a furnace. The time the tube is heated and maintained at the above temperature depends on the wall thickness and the amount of polymer present in the mica paper. However, typical times are about 2-4 hours.

It is important to restrain the tube while the binder is hardened by heating the tube so that the tube does not collapse. This can be done using a mold or by wrapping the tube in a removable layer such as glass cloth, or by placing the tube in a woven fiberglass sleeve and pulling it to tension. This may be done by bringing about the condition. In this case, the constraints imposed on the tube need not be large, but they must be present.

Once the tube's binder is cured, the tube is cooled to ambient temperature, then unconstrained and machined to the desired dimensions if not in the final shape.

The mica cylinder obtained in this manner is a thermally stable and excellent electrical insulating material, and has very high moisture resistance and very high fracture toughness. All these properties make it an excellent alternative to traditional ceramic or glass components traditionally used in the electrical industry.Furthermore, such cylinders have a low operating temperature. It does not become brittle when heated to a high temperature and is dimensionally stable, thus being superior to glass or ceramic cylinders.

Moreover, such cylinders have very good dielectric properties.

example A mica cylinder was formed according to the invention as follows.

Two sheets of muscovite paper, each 127μ thick, weigh approximately 8
A silicon binder having an average concentration of wt%,
It was impregnated with a silicone binder containing 1 wt% isopropyl tri(dioctylpyrophosphate) titanate solids and 2 wt% zinc naphthenate solids. The two sheets are then stacked on top of each other, and a 13-metre step is applied to evenly distribute the binder and join the two sheets together.
It was pressed at about 31.04 bar for 30 minutes at 5°C, thereby forming a piece of mica paper 254μ thick, 91.44cm wide and about 18.28cm long.

The mica paper is then placed along the belt onto the platen 30 through the belt as shown in the accompanying figure, approximately 30 mm
It was heated to 232°C for a period of seconds to 1 minute. The mica paper was then wrapped around a 1.270 m diameter shaft coated with silicone mold release agent. The shaft and uncured mica cylinder were then placed within a sleeve consisting of woven glass fibers stretched under tension around the cylinder and shaft. The cylinder, thus restrained by the sleeve, is then placed vertically in a furnace and exposed to four cylinders to cure the binder.
It was heated to 260° C. for an hour. The cylinder was then cooled, the sleeve was unconstrained, and the rear shaft was withdrawn. The tube thus obtained had an internal diameter of 1.27 cm and a wall thickness of 762 microns. Additionally, several properties of this tube were tested. The results are shown in Table 2 below.

Table 2 Dielectric strength per wall thickness of 25.4μ (AS
TM D 149) 500VASTM on average
Water immersion (ASTM D 570, less than 0.5% weight gain 24 hours in water at 23°C) Thermal shock Less than 1% weight loss (500°C)
(1 hour) In the above example, the method of the present invention has been described as a rolling method, but other cylinder forming methods using conventional paper rolling equipment or cylinder forming apparatus may be employed.

The excellent moisture resistance of the cylindrical body formed as described above is presumed to be due to the fact that the silicone polymer significantly improves the wettability of mica. It is presumed that naphthenate and titanate work together to form a good chemical bond between mica and silicon, resulting in improved moisture resistance, fracture toughness, and thermal stability.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. This will be clear to those skilled in the art.

[Brief explanation of drawings]

The accompanying figures previously illustrate a conventional belt-type rolling apparatus that may be used to form the mica cylinders of the present invention. 10... Rolling equipment ffi, 20... Belt, 2
5... Roller, 30... Platen, 40... Mica paper, 50... Shaft, 55... Curved portion, 60... Rondo patent application Artificial Sex Group, Inc.

Claims (2)

[Claims] (1) one or more impregnated with substantially 5-20 wt% polysiloxane binder containing substantially 1-4 wt% organic titanate and substantially 0.5-2 wt% metal naphthenate; Contains more than mica paper layer, high density,
Cylindrical mica composite with fracture toughness, moisture resistance and thermal stability. (2) A method for producing a cylindrical mica structure, comprising forming a mica paper and containing substantially 1 to 4 wt% organic titanate and substantially 0.5 to 2 wt% metal naphthenate on a solid basis in an organic solvent. impregnating the mica paper with a composition containing substantially 5 to 20 wt% polysiloxane binder, heating the mica paper to remove the solvent, the mica paper from which the solvent has been removed. forming the mica paper into a cylindrical structure; constraining the cylindrical structure; and heating the constrained cylindrical structure to bind the polymer binder. curing, cooling the cylindrical structure, and removing the constraints, thereby forming a dense cylindrical mica structure having fracture toughness, moisture resistance, and thermal stability.