JPH01297102A - Heat-resistant porous hollow fiber and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a heat-resistant porous hollow fiber by using a dehydration reaction product of polyvinyl alcohol with a specific weight reduction rate due to dehydration reaction. CONSTITUTION:A hollow fiber is manufactured with an aqueous ammonium sulfate as a coagulating liquid using an aqueous solution of high saponified polyvinyl alcohol with a degree of saponification of 99.0mole% or more and partially saponified polyvinyl alcohol with an exceedingly low degree of polymerization. This hollow fiber is immersed in an aqueous solution of saturated ammonium sulfate and thermally treated. Then it is soaked in water and further, the partially saponified polyvinyl alcohol with an exceedingly low degree of polymerization is removed by washing from the external part of the hollow fiber under the water current pressure of the water pressure system to obtain the porous hollow fiber of highly saponified polyvinyl alcohol. Next, this hollow fiber is impregnated with a mixed solution of methanol of p-toluenesulfonic acid and water, and is allowed to receive an acid catalyst by drying with air or by any other appropriate means. The hollow fiber is placed in an oven with both ends fixed to a constant length, then it is subjected to dehydration reaction so that the weight reduction rate is 5-35wt.%. Thus the porous hollow fiber which is insoluble in a solvent and withstands any pressure at a high temperature, is obtained.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to porous hollow fibers with excellent heat resistance.

[Conventional technology] Various polymeric materials are used as ultrafiltration membranes and precision filtration membranes for producing pure water and filtering colloidal substances and bacteria in water. Porous hollow fibers that can obtain a filtration TrrJ product are increasingly being used; these hollow fibers include:
From the viewpoint of formability and physical properties, thermoplastic (or solvent-soluble) polymers having stringability such as polyethylene, polypropylene, polyvinyl alcohol, polyacrylonitrile, polysulfone, polyethersulfone, and polyimide are used.

[Problems to be solved by the present invention] However, originally [i! These materials, which are chain polymers, can be kept at 100°C for long periods of time, even if cross-linking is introduced later.
There is a limit to its use at high temperatures exceeding .

For this reason, thermal power is used in fields such as medicine, food, and medicine, which require high-temperature treatment and steam sterilization.

The emergence of porous hollow fibers that can be used for long periods of time at high temperatures is strongly desired for clarification of feed water for nuclear power plants and other steam generators, as well as precision filtration of oils and fats and various solutions that require processing at high temperatures. It was rare.

An object of the present invention is to provide a heat-resistant porous hollow fiber that can meet these demands.

[Means for Solving the Problems] An object of the present invention is to reduce the weight loss rate due to dehydration reaction from 5 to 35
This is achieved by a heat-resistant porous hollow fiber composed of a dehydrated product of polyvinyl alcohol with a w1% content.

The hollow fibers of the present invention can be obtained by heating porous hollow fibers made of polyvinyl alcohol with a degree of saponification of 99.0 mole % or more in the presence of an acid catalyst to reduce the weight by 5 to 35 wt%.

The hollow fibers of the present invention can be used with any solvent while maintaining excellent permeability, by dehydrating polyvinyl alcohol to form a mainly polyene structure, and at the same time forming a dehydration reaction product with ether bonds and complex oxidation reactions. It is thought that it is insoluble in water and has the property of being able to withstand pressure at high temperatures.

Note that improving the water resistance of polyvinyl alcohol fibers by utilizing the dehydration reaction of polyvinyl alcohol is known from Japanese Patent Publication No. 53-22106 filed by the applicant of the present invention, etc., but the present invention utilizes these findings. However, we have discovered that a remarkable effect can be obtained as a hollow fiber for porous hollow fibers whose manufacturing method, form, internal structure, and usage conditions are completely different.We pursued the optimal conditions and finally developed the present invention. has been reached.

Hereinafter, the ffi of the present invention will be explained in more detail.

Firstly, the polyvinyl alcohol constituting the porous hollow fiber which is the starting material of the present invention tends to have a tendency for the dehydration reaction to proceed with difficulty when there are many acetic acid groups present in IA. a
% or more of highly saponified polyvinyl alcohol.

As long as the porous hollow fibers are composed of highly saponified polyvinyl alcohol, the hollow fibers can be selected in terms of the pore diameter and porosity of the porous hollow fibers depending on the purpose of use, and there are no particular restrictions on the manufacturing method.

Acid catalysts include benzenesulfonic acid, alkylbenzenesulfonic acids, and naphthalenesulfonic acid.

Organic compounds having a sulfonic acid group or a sulfuric acid ester group such as alkylnaphthalene sulfonic acids and alkyl IA acid esters; sulfuric acid, sulfamic acid, and the like.

Moreover, those that generate sulfonic acid groups by heating, such as propane sultone, can also be used.

However, carboxyl groups, phosphoric acids, phosphonic acids, and phosphinic acids have a strong tendency to form ester bonds with polyvinyl alcohol and are not preferred.

Such a catalyst can be applied in advance to the hollow fibers as an aqueous solution by drying at a low temperature in an impregnation machine, and then subjected to the next dehydration reaction. Furthermore, when the catalyst can be gasified, such as hydrochloric acid, the dehydration reaction can be carried out while directly supplying the gaseous catalyst.

The dehydration reaction of polyvinyl alcohol is carried out in the presence of such a catalyst at a temperature of 100 to 250°C, more preferably 130 to 250°C.
This can be done by heating to 220°C.

The dehydration reaction depends on the reaction temperature, reaction time, and type of catalyst.

Affected by catalyst concentration, etc. In addition, in the presence of oxygen, such as in the presence of oxygen, complex oxidation reactions may proceed simultaneously with dehydration reactions. A mild oxidation reaction may not be a problem, but if you want to avoid this, the dehydration reaction should be carried out in an M atmosphere.

As the dehydration reaction progresses, porous hollow fibers made of polyvinyl alcohol become insoluble in any solvent, and eventually stop swelling and exhibit excellent heat resistance. At the same time, they become hard and have improved pressure resistance, but the dehydration reaction progresses further. This causes problems such as brittleness (easiness to break).On the other hand, if the degree of dehydration reaction is too light, the required heat resistance cannot be obtained, which is undesirable.

The degree of dehydration reaction is determined by the weight loss rate (wt%), that is, 1
It can be determined by D-X 100÷weight before reaction, and this weight reduction rate is preferably in the range of 5 to 35%, particularly preferably 10 to 30%.

[Examples] In the following, nine examples will be given to specifically explain embodiments of the present invention, in which parts mean parts by weight.

Example 1 Average degree of polymerization 1,200, degree of saponification 99.9m. 50 parts of Ie% highly saponified polyvinyl alcohol, average degree of polymerization 50.
50 parts of partially saponified polyvinyl alcohol with a saponification degree of BB and a super low degree of polymerization of 5 mole% and 1110 parts of water were kneaded.
(TS disintegration machine), and an aqueous solution having a concentration of 36.8% and a viscosity of 230 polsa was stirred at 110° C. for 2 hours under sealed conditions.

Apply this aqueous solution to the core through a nozzle with a diameter of 700μ.
% of ammonium sulfate aqueous solution, and then immediately heated to 40°C.
, was introduced into a 40wI% ammonium sulfate aqueous solution and coagulated to obtain a hollow fiber. This was heat-treated by immersing it in a saturated ammonium sulfate aqueous solution at 130°C for 3Ω, and then immersed in room temperature water for a day and night.Then, the outside of the hollow fiber was pressurized and the ultra-low polymerization degree partially saponified polyvinyl alcohol was washed with an out-in water stream. i1J+ left,
The porous hollow fibers were made of only highly saponified polyvinyl alcohol.

The obtained porous hollow fibers were impregnated with a methanol-water mixed solution of para-toluenesulfonic acid and then dried with hot air to impart 1.3 wLX of para-toluenesulfonic acid as a dehydration catalyst to the hollow fibers.

This was placed in an oven with both ends fixed at a constant length, and heat treated at 150°C for 30 minutes and 200°C for 26 minutes to obtain hollow fibers (A) and (B) of the present invention.

With this process, (A) is 19.7%, (B) is 25%,
It showed a 3% reduction in dehydration.

Example 2 A small amount of gas was continuously supplied from the center of the pipe to a stainless steel pipe with an inner diameter of 30 mm and a length of 3 m with both ends tapered to maintain a nitrogen gas and 1% VO 1% hydrogen chloride gas atmosphere, and the internal temperature was raised to 170 ml. Example 1
A dehydration reaction was carried out by passing 20 m of the porous hollow fiber obtained in step 1 at an overfeed rate of 10% for 1 hour.

The dehydration risk of the thus obtained hollow fiber <C> of the present invention is 14
．． It was 9%.

A module was made by bundling 10 of the hollow fibers of the present invention obtained in this way, placing them in a stainless steel pipe, and hardening the opening with epoxy resin, and then pumping ethylene glycol of +40"C and applying a pressure of 2.3 kg/cm to the module. A liquid flow test was conducted in this direction.

Although there is a difference in water permeability, the hollow fiber (A) of the present invention.

In both (B) and (C), the fluid continued to be passed for a -week test period.

No crushing of the cross section was observed after the test.

In addition, both were added to 120'C pressurized water and rapeseed oil.
When a monthly immersion test was conducted, almost no changes in morphology or filtration performance were observed.

[Effects of the invention] As described above, the hollow fibers of the present invention have excellent heat resistance, and can be used in fields such as medical, food, and pharmaceutical fields that require high-temperature treatment and sterilization with steam, as well as in thermal power, nuclear power, and other fields. Removal of water supply for steam generators 1. Furthermore, it is expected that it can be used for long periods of time at high temperatures for applications such as precision filtration of oils and fats and various solutions that require processing at high temperatures.

Claims (1)

[Scope of Claims] 1) A heat-resistant porous hollow fiber composed of a dehydration reaction product of polyvinyl alcohol whose weight loss rate due to dehydration reaction is 5 to 35 wt%. 2) Polyvinyl having a saponification degree of 99.0 mole% or more. A method for producing heat-resistant porous hollow fibers, which comprises heating porous hollow fibers made of alcohol in the presence of an acid catalyst to reduce the weight by 5 to 35 wt%.