JPH0829236B2 - Dehumidifying film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dehumidifying membrane. More specifically, it relates to a dehumidifying film made of a modified polyvinyl alcohol-based polymer (hereinafter, polyvinyl alcohol is abbreviated as PVA).

[Prior Art] In recent years, research and development for separating water vapor from a mixed gas containing water vapor have been actively conducted. For example, in the separation of water vapor from methane, hydrogen chloride gas, nitrogen gas, air, or the like. Consideration is being made.

Conventionally, for such dehumidification / drying of mixed gas, a cooling method, an absorption method, an adsorption method, a compression method, and the like have been studied, and each is put into practical use for practical use. However, all of these methods require large equipment, high equipment costs,
There are problems such as complexity of operation, difficulty of maintenance, and consumption of a large amount of energy.

In contrast to the above-mentioned conventional methods, several methods have been proposed for separating water vapor using a membrane, which can be downsized and easy to maintain, and which is attracting attention as an energy-saving process. For example, JP-A-54-152679, JP-A-59-59236, and JP-A-62-273028 disclose dehumidification / drying methods using a film made of a PVA-based polymer.

[Problems to be Solved by the Invention] However, when water vapor is separated from a mixed gas according to the method disclosed in the above-mentioned publicly known document, when the amount of water vapor in the mixed gas supplied to the separation membrane is large, that is, relative When the humidity (hereinafter abbreviated as RH) is close to 100%, good results are obtained as expected, but the amount of water vapor in the supplied mixed gas is small, that is, when RH is low, the separability between the mixed gas and water vapor is low. Was found to be extremely low. In addition, it is difficult to say that the methods disclosed in the above-mentioned publicly known documents have sufficient dehumidification performance, and there is a demand for a dehumidification method using a film having excellent dehumidification performance.

Therefore, an object of the present invention is to provide a dehumidifying film having extremely high moisture permeability without depending on the water vapor content rate (that is, RH) of the mixed gas to be supplied.

[Means for Solving the Problem] As a result of earnest studies for solving the problem, the present inventor has surprisingly found that the PVA polymer has isobutylene-
A film made of a modified PVA containing at least one polymer selected from the group consisting of a maleic anhydride copolymer and / or a salt thereof, gelatin and polyvinylpyrrolidone, has a water vapor content of a mixed gas (that is, ,
The inventors have found that they have extremely high moisture permeability without being affected by RH) and have reached the present invention. That is, the present invention is a dehumidifying membrane composed of a modified PVA-based polymer containing at least one polymer selected from the group consisting of an isobutylene-maleic anhydride copolymer / or its salt, gelatin and polyvinylpyrrolidone.

The PVA polymer used in the present invention includes not only polyvinyl alcohol consisting of vinyl alcohol units, but also copolymers of olefinic compounds such as ethylene and vinyl alcohol and partially saponified products thereof, and the above PV.
A, the above copolymer, and the above partially saponified product chemically modified with aldehyde or the like are also included.

The isobutylene-maleic anhydride copolymer used in the present invention is not particularly limited as long as it is a copolymer of isobutylene and maleic anhydride. Such isobutylene-
As the maleic anhydride copolymer, for example, commercially available products such as Isoban-10, Isoban-06 and Isoban-04 (trade name) manufactured by Kuraray Co., Ltd. can be used. The salt of isobutylene-maleic anhydride copolymer can be easily obtained by dissolving the isobutylene-maleic anhydride copolymer in an aqueous alkaline solution. Further, as gelatin and polyvinylpyrrolidone, commercially available products can be used.

In the present invention, the isobutylene-maleic anhydride copolymer and / or its salt, gelatin and polyvinylpyrrolidone may be used alone or in a mixture of two or more.

The modified PVA-based polymer used in the present invention is prepared so that the PVA-based polymer contains at least one polymer selected from the group consisting of isobutylene-maleic anhydride copolymer and / or its salt, gelatin and polyvinylpyrrolidone. The film can be formed by a generally known method.

In the present invention, the amount of at least one polymer selected from the group consisting of isobutylene-maleic anhydride copolymer and / or salt thereof, gelatin and polyvinylpyrrolidone with respect to the PVA-based polymer varies depending on the PVA-based polymer used. Generally, from the viewpoint of dehumidification performance and film-forming property, generally, the PVA polymer is preferably contained in an amount of 10 to 200% by weight, more preferably 20 to 100% by weight.

The shape of the dehumidifying membrane of the present invention is not particularly limited, and flat membranes, tubular membranes, hollow fiber membranes and the like can be appropriately used.

As a method for dehumidifying and drying the mixed gas using the dehumidifying membrane of the present invention, the side that supplies the mixed gas containing water vapor (primary side)
Is pressurized above atmospheric pressure and the side through which water vapor permeates (secondary side) is set to atmospheric pressure to dehumidify and dry the mixed gas. The primary side is pressurized above atmospheric pressure and the secondary side is depressurized. Then, the mixed gas is dehumidified and dried, the primary side is pressurized to atmospheric pressure or higher, and a (mixed) gas with a smaller water vapor content than the primary side is flowed to the secondary side to reduce the partial pressure of the transmitted water vapor. Dehumidifying the mixed gas by lowering it to dehumidify and dry the mixed gas, pressurizing the primary side to atmospheric pressure or higher, depressurizing the secondary side and flowing (mixed) gas with a lower water vapor content than the primary side. -There is a method of drying, etc., which is appropriately used as necessary.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 3 and Comparative Example PVA having a polymerization degree of 1700 and a saponification degree of 88.5 mol% (manufactured by Kuraray Co., Ltd .; trade name PVA-217) was made into a 10 wt% aqueous solution.
It melt | dissolved, stirring at 100 degreeC for 5 hours.

The solution was neutralized with sodium hydroxide to obtain a neutralization degree of 0.
An isobutylene-maleic anhydride copolymer (5) (manufactured by Kuraray Co., Ltd .; trade name Isoban-10) in a 25 wt% aqueous solution was used as a PV.
Add to 45% by weight with respect to A, thoroughly degas, then cast on a Teflon plate and air dry at room temperature to obtain a film thickness of 20-25
A μm isovan-PVA membrane was obtained.

The membrane is provided with an inlet for the gas to be dried and an outlet for the dried gas on one side (primary side) of the membrane, and an effective membrane area with a vacuum pump on the other side (secondary side) of the membrane. Is 28.3 cm ²
It was attached to the test equipment of.

The pressure on the primary side was set to 4 kg / cm ² G, the pressure on the secondary side was set to 5 mmHg, and air was supplied continuously at a temperature of 25 ° C. at 50 ml / min while changing the RH. The obtained results are shown in FIG. 1 (Example 1).

Neutralization degree of Example 1 neutralized with sodium hydroxide.
A film was prepared in the same manner as in Example 1 except that 100% by weight of gelatin and 50% by weight of polyvinylpyrrolidone were used instead of 45% by weight of the isobutylene-maleic anhydride copolymer of 5 respectively, and the above test was conducted. The measurement was carried out by the device under similar conditions. The results are also shown in FIG. 1 (Example 2: gelatin,
Example 3: Polyvinylpyrrolidone).

For comparison, the case where a film made of PVA alone is used is also shown (comparative example).

[Brief description of drawings]

FIG. 1 shows the results of dehumidification tests in Examples 1 to 3 and Comparative Example. 1 …… Example 1 2 …… Example 2 3 …… Example 3 4 …… Comparative Example [Advantages of the Invention] According to the present invention, compared with the conventional PVA membrane, in the mixed gas supplied with moisture permeability. It is possible to provide a dehumidifying film that is not affected by the water vapor content of the. The dehumidifying film provided by the present invention is, for example, a general-purpose gas such as nitrogen in the electronics field, a corrosive gas such as hydrogen chloride and chlorine, a rare gas such as argon and helium, and further, such as silane, arsine, and borane gas. It can be widely used for dehumidification or drying of special gas, air, natural gas, associated gas at the time of crude oil mining, fermentation gas, etc., and the present invention has great significance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01D 71/74 9538-4D // B01D 53/22 9538-4D

Claims (1)

[Claims] 1. A modified polyvinyl prepared so that a polyvinyl alcohol-based polymer contains at least one polymer selected from the group consisting of an isobutylene-maleic anhydride copolymer and / or a salt thereof, gelatin and polyvinylpyrrolidone. Dehumidifying film made of alcohol-based polymer.