JPH01261286A - Stabilization of formed article - Google Patents

Abstract

PURPOSE:To improve a formed article in mechanical strength shortage, instability at room temperature under high humidity, etc., by impregnating a formed article of copper oxide-contg. metallic oxide sintered form with a liquid thermosetting resin followed by curing to seal the voids in the sintered form with the resultant cured resin. CONSTITUTION:Firstly, a formed article of a metallic oxide sintered form (said metal containing copper, e.g., copper-barium-yttrium, copper-calcium-strontium- bismuth) is prepared. Thence, this formed article is impregnated with a liquid curable resin (e.g., unsaturated polyester resin, epoxy monoacrylate resin) followed by curing to seal the voids in the sintered form with the resultant cured resin. Thus, said formed article can be stabilized, and in case said sintered form is a ceramic superconductor, Meissner effect will stably be retained even at room temperature and high humidity.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to the effects of so-called oxide superconductors, particularly to the temperature at which the superconductor known as the Meissner effect becomes superconducting. The present invention relates to a method for stabilizing a molded product that can stably exhibit the levitation effect of a magnet or superconductor due to the magnetic force line exclusion effect.

[Conventional technology]

Since the announcement of the superconductivity of metal oxide sintered bodies (hereinafter referred to as ceramics) at the temperature of liquid nitrogen, several drawbacks of this material have been pointed out, and improvements are required for practical use. This is well known.

One of the reasons is that ceramic superconductors are relatively unstable, and their superconductivity and the effects they exhibit quickly disappear, especially under high temperature and high humidity conditions, and also because they are sintered bodies. Examples include insufficient strength to move.

The major phenomena exhibited by superconductivity are thought to be the generation of persistent current due to zero electrical resistance, the possibility of obtaining a strong magnetic field accompanying this, and the so-called Meissner effect.

Originally, the Meissner effect means that even if the magnetic field is lowered at a constant temperature, or even if the temperature is lowered with a constant magnetic field, the magnetic field within the conductor will become zero once it transitions to a superconducting state, which means that the electrical resistance will change from zero to zero. is one of the fundamental properties of independent superconductivity that cannot be guided.

In general, only the resulting magnetic levitation effect is highlighted and is recognized as the Meissner effect, so the present invention also follows this convention.

[Problems to be Solved by the Invention] The present invention solves the problem of lack of strength of molded products and problems due to the fact that conventional ceramic superconductors are sintered bodies. ML% The object of the present invention is to provide a molded article that can maintain the Meissner effect stably even at room temperature and high humidity, without the drawback of instability under high humidity.

[Means to solve the problem]

As a result of various studies to solve the above-mentioned problems, the present inventors impregnated and hardened a liquid thermosetting resin into a molded product of a metal oxide sintered body containing a copper oxide. The present invention was achieved based on the knowledge that the above problem can be solved by sealing the voids in the resin with a cured resin.

[For production]

In the present invention, by employing a method of impregnating and curing ceramics with a thermosetting resin instead of using ceramics alone, the voids of the ceramics (generally 20 to 35%
This is based on the knowledge that although it has a two-phase structure in which a resin phase exists (which is said to exist), it does not inhibit the Meissner effect of ceramics. In addition, in the molded product of the present invention, instability at room temperature is improved because the ceramic superconductor is isolated from the outside world by the hardened resin, and the strength of the molded product is also improved by using the hardened resin. There are advantages.

The ceramics that can be used in the present invention are so-called high-temperature superconductors that exhibit superconductivity at temperatures above the boiling point of liquid hydrogen, that is, about 20 degrees, obtained by firing a metal oxide containing copper oxide as an essential component. This is the kind of thing that makes it possible.

Copper oxide is an essential component, but other metal oxides include oxides of group Ⅰ alkaline earth metals of the periodic table, group Ⅰ rare earth metals, as well as bismuth, thallium, and the like.

Typical examples of combinations include molded products of sintered oxides of copper, barium, yttrium, copper, calcium, strontium, and bismuth.

Ceramic molded articles can be obtained in specific shapes using conventional sintering means.

The liquid thermosetting resin used in the present invention is not particularly limited in type and properties as long as it can be impregnated into ceramics in liquid form. Therefore, it is desirable that the viscosity be as low as possible. Taking these into consideration, radical curing resins whose viscosity can be easily adjusted using monomers are optimal.

Examples of thermosetting resins include unsaturated alkyds obtained by reacting unsaturated polybasic acids and polyhydric alcohols in the presence or absence of saturated polybasic acids, which are obtained by blending monomers such as styrene. Typical examples thereof include unsaturated polyester resins obtained by the reaction of epoxy resins and (meth)acrylic acid, epoxy acrylate or vinyl ester resins obtained by the reaction of epoxy resins and (meth)acrylic acid, and diallyl phthalate resins. In addition, oligomers called oligoacrylates, such as polyester acrylate and urethane acrylate, in which a (meth)acryloyl group is introduced into the molecular terminal or side chain, as well as polyene-polythiol resins can also be used.

Epoxy resins can also be used practically, especially if they are of low viscosity type such as alicyclic, ester, or bisphenol F type. These thermosetting resins are commercially available, and their manufacturing methods are also known. Also,
Thermoplastic polymers can also be blended to modify thermosetting resins.

Impregnation of the liquid thermosetting resin into the ceramic molded article is preferably carried out under reduced pressure or increased pressure.

〔Example〕

Examples are shown below to help understand the present invention. All parts and percentages in the text are expressed on a weight basis.

Example 1 Made by Furuuchi Kagaku ■, diameter 20 mm, thickness approximately 8III1
1 copper-barium-yttrium metal oxide (ratio 3
:2:1) After cooling the sintered body with liquid nitrogen in the company's equipment and confirming that the attached magnet floats approximately 5mm+,
Returned to room temperature.

In a 100cc polyethylene beaker, add 50 unsaturated polyester resin (GOLAC 1608 manufactured by Showa Kobunshi).
1 part of methi, 1210 parts of methi, and 1 part of benzoyl peroxide were uniformly dissolved, and the ceramic sintered body was impregnated therein, and immediately impregnated under a reduced pressure of 50 to 60 Torr until the generation of fine bubbles was completely stopped. The amount of resin impregnated was about 30%.

After the impregnation was completed, the pressure was returned to normal, and the mixture was first heated at 60°C overnight, then taken out from the beaker and heated at 100°C for 2 hours to complete curing.

A black, hard and uniform molded article (A) was obtained. When a portion of it was cut and polished and observed under a microscope, it was confirmed that it consisted of two phases: a ceramic particle phase and a resin phase.

Cut this molded product (A) from the excess resin.

After polishing and removing all but one layer of the resin on the surface, and fabricating it in the same manner, the Meissner effect was measured in the same manner as above, and the magnet levitated to a height of about 5 mm.

Separately, the sintered body manufactured by Furuuchi Chemical Co., Ltd. and the molded article of the present invention (
A) was prepared and stored in a desiccator at 40°C and 95% R and H. After one month, the Meissner effect of the sintered body disappeared and magnetic levitation ability was observed. On the other hand, molded product (A) showed the same magnetic levitation effect even after one month.

Example 2 As an epoxy resin, a type in which methacrylic acid and epoxy groups (approximately 50 C%) were reacted was used.

Synthesis of epoxy monoacrylate resin In a 1J7 separable flask equipped with a stirrer, a reflux condenser, and a thermometer, 370 parts of bisphenol A diglycidyl ether type epoxy resin with an epoxy weight of 187 m,
86 parts of methacrylic acid, 2 g of trimethylbenzylammonium chloride, 0.2 g of hydroquinone,
After reacting at 30-135°C for 1.5 hours, the acid value became substantially zero.

At this stage, 200 g of styrene was added to obtain an epoxy monoacrylate resin.

66 parts of the epoxy monoacrylate resin was placed in a polyethylene beaker, and 14 parts of methyltetrahydrophthalic anhydride and 1 part of benzoyl peroxide were added thereto to form a homogeneous solution.

Superconducting ceramic pellets (metal oxide containing bismuth, strontium, calcium, and copper in a ratio of 1:1:1:2) manufactured by Furuuchi Chemical ■ are impregnated into the solution, and fine bubbles are generated under reduced pressure of approximately 100 Torr. After impregnating the sample until it was no longer wet, it was taken out and both sides were covered with polyester film.

This was first heated at 80°C for 3 hours, the polyester film was removed, and heated at 120°C for 3 hours and 150°C for 5 hours.
hardened.

It was confirmed that the cut surface of the obtained molded article (B) had two phases: a ceramic phase and a resin layer.

Both the superconducting ceramic pellets and the molded product (B) were heated at 40°C and 95% R,)1. When stored in a desiccator for one month, ceramic pellets showed no magnetic levitation effect at all even when cooled with liquid nitrogen, whereas molded product (B) showed a levitation effect of approximately 1 mm. .

〔Effect of the invention〕

The molded article of the present invention can stably maintain the excellent Meissner effect even at room temperature and high humidity, and the strength of the obtained molded article is also improved, so it is expected to be used in many fields.

Patent applicant: Showa Kobunshi Co., Ltd.

Claims (3)

[Claims] (1) For molded products of metal oxide sintered bodies containing copper oxide,
A method for stabilizing a molded article, which comprises impregnating and curing a liquid thermosetting resin and sealing voids in a sintered body with the cured resin. (2) The molded product according to claim 1, wherein a molded product of a metal oxide sintered body consisting of copper, barium, yttrium, or copper, calcium, strontium, and bismuth is used as the molded product. Stabilization method. (3) The method for stabilizing a molded article according to claim 1, wherein the liquid thermosetting resin is an unsaturated polyester resin or an epoxy monoacrylate resin.