JPS6149097B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing polyimide tubes. Conventionally, as electrical insulating materials for covering electric wires or bundling cables, adhesive is applied to one side of polyethylene film or polyvinyl chloride film.
An electrical insulating tape obtained by cutting this into a predetermined width is used. This electrical insulating tape is used by wrapping it around the adherend, but wrapping it around the adherend is not always easy, and the insulation performance of the covering part varies depending on the skill level of the worker. There are some easy drawbacks. To improve the drawbacks of electrically insulating tapes, electrically insulating tubes such as polyethylene tubes and polyvinyl chloride tubes, which do not require wrapping work when applied to adherends, have come into use. Incidentally, in recent years, demands for improving various properties such as heat resistance for electrical insulating materials have become even more stringent, but the polyethylene tubes and polyvinyl chloride tubes mentioned above are increasingly unable to meet these demands. Ta. Therefore, polyimide resin is attracting attention as an electrical insulating material that meets this demand, but polyimide resin has a high melt viscosity and poor fluidity, so tube molding using extrusion molding like other thermoplastic resins cannot be applied. Further, since polyimide resin itself does not exhibit heat-fusibility, a method of winding a film around a core material and then heat-sealing it to form a tube cannot be applied. Although polyimide resin is significantly superior to polyethylene and polyvinyl chloride in terms of heat resistance and other properties, it is not widely used in industrial tube manufacturing due to the difficulty of molding. Not yet. The present invention was made in view of the above-mentioned current situation, and an object of the present invention is to provide a tube that can fully exhibit the excellent heat resistance inherent to polyimide resin. That is, the method for producing a polyimide tube according to the present invention is based on the general formula A polyamic acid solution obtained by reacting biphenyltetracarboxylic dianhydride (hereinafter referred to as BPDA) represented by (hereinafter referred to as BPDA) and an aromatic diamine in an organic polar solvent is heated and dried to convert a part of the polyamic acid into imide. At the same time, a polyimide precursor film with a volatile content of 5 to 30% by weight is obtained, and then the precursor film is wound around a heat-resistant core and heated to thermally fuse the films together and remove the remaining polyamic acid. This method is characterized by imidizing the molecule and then removing the heat-resistant core. In the present invention, a polyamic acid solution is obtained by first reacting BPDA and aromatic diamine in an organic polar solvent. This polyamic acid solution is represented by the general formula above.
BPDA e.g. 3,4,3',4'-BPDA, 2,3,
3′4′-BPDA, 2,3,2′,3′-BPDA and aromatic diamines such as m-phenylenediamine, P-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′- diaminodiphenyl ether,
4,4'-diaminodiphenylpropane, 4,4'-
Diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 1,5-diaminonaphthalene,
It is obtained by reacting 2,6-diaminonaphthalene and 3,4'-diaminobenzanilide in an organic polar solvent. Examples of the organic polar solvent include N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-
N,N-dialkylcarboxamides such as diethylacetamide and N,N-dimethylmethoxyacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, dimethylsulfone, hexamethylphosphoramide, and the like are used. The concentration of the monomer in the organic polar solvent when reacting the above-mentioned BPDA and aromatic diamine to obtain a polyamic acid solution can be set depending on various conditions, but is usually 5 to 30% by weight, preferably 10 to 25% by weight. %. Further, the reaction temperature is usually 80°C or lower, preferably 5 to 50°C, and the reaction time is usually about 1 to 10 hours. In the present invention, BPDA, aromatic diamine and organic polar solvent may be used alone or in combination of two or more. Furthermore,
Organic polar solvents include aromatic hydrocarbons such as benzene, toluene, and xylene, ethers such as dioxane,
Ketones such as methyl ethyl ketone, methanol,
It is also possible to use a mixture of solvents such as alcohols such as ethanol, phenols such as phenol, and cresol. In this way, when BPDA and aromatic diamine are reacted in an organic polar solvent, polyamic acid is produced, and the solution viscosity increases as the reaction progresses.
In the present invention, it is preferable to obtain a polyamic acid solution having an intrinsic viscosity of 0.5 or more. Intrinsic viscosity is 0.5
A polyimide precursor film (hereinafter referred to as precursor film) was obtained using the above polyamic acid solution,
When the film is formed into a tube, it has a characteristic that the tube has particularly excellent mechanical strength. The intrinsic viscosity of the polyamic acid solution used in the present invention is determined by taking out the polyamic acid from the polyamic acid solution, dissolving this polyamic acid in a specified solvent, measuring the solution viscosity, and then determining the following ()
This is the value calculated using the formula.

[Table] Solvent viscosity Intrinsic viscosity =

Claims (1)

[Claims] 1. General formula A polyamic acid solution obtained by reacting biphenyltetracarboxylic dianhydride represented by and aromatic diamine in an organic polar solvent is heated and dried to convert a part of the polyamic acid into imidation and to reduce the volatile content. A polyimide precursor film containing 5 to 30% by weight of A method for producing a polyimide tube characterized by removing a heat-resistant core.