JPS61153105A - Manufacture of gas permselective composite membrane - Google Patents

Abstract

PURPOSE:To obtain the titled gas permselective membrane having excellent resistance to heat and chemicals by plasma-polymerizing a mixed vapor of an org. silane compd. consisting of a saturated hydrocarbonic group and gaseous nitrogen or ammonia or a nitrogen-contg. org. compd. on a high molecular supporting body. CONSTITUTION:A high molecular supporting body such as polysulfone and polyphenylene oxide having excellent resistance to heat and chemicals is set in a reaction vessel of a plasma polymerization device, and the vessel is evacuated to <=0.01torr vacuum. A mixed vapor of the monomer vapors of an org. silane compd. consisting of a saturated hydrocarbonic group and gaseous nitrogen or ammonia or a nitrogen-contg. org. compd. such as allylamine, secondary butylamine, diethylamine, aniline, pyridine, etc., is introduced under <=5torr vacuum. Electric power of 10-200W is impressed to produce glow discharge for a specified time, a plasma-polymerized thin film having necessary thickness is deposited and the operation is completed.

Description

Detailed Description of the Invention "Object of the Invention""Industrial Application Field" The present invention relates to a method for producing a gas-selective permselective composite membrane, and more specifically, to a method for producing a gas-selective permselective composite membrane, and more specifically, a method for producing a plasma-polymerized membrane on the surface of a polymer support. The present invention relates to a method for producing a gas-selective permselective composite membrane.

"Conventional Technology" In recent years, gas separation and purification technology using polymer membranes has been actively developed from the standpoint of energy conservation.

For example, large-scale industrial technology research rCi Chemistry is progressing with the development of hydrogen selectively permeable membranes that separate hydrogen and carbon monoxide, and oxygen enrichment membranes used for medical purposes and combustion systems separate oxygen and nitrogen. Targeted. The properties required for these gas selective permeable membranes include not only high separation properties and permeability, but also heat resistance, chemical resistance, and mechanical strength, which are useful for practical use. In order to meet these characteristics,
Various manufacturing methods have been studied for the development of gas-selective permeable membranes, but the most noteworthy among them is a membrane-forming method that utilizes plasma polymerization. Plasma polymerization is operated under reduced pressure, so there is no problem with dust contamination during film formation, and unlike wet methods, it does not require the use of solvents or heating means.
It is possible to create an extremely thin pinhole-free film on the surface of the support.

Reference J, of Appl, Polym, Sci, 150
Section 5, Volume 16 (1972) reports examples of gas selectively permeable composite membranes mainly using compounds containing cyano groups. A plasma-polymerized film of bromine cyanide is deposited on polyphenylene oxide to improve the separation characteristics of hydrogen/CH, but the cyanide compound used here is highly toxic and must be handled with care. The resulting polymeric membrane has the disadvantage of poor flexibility and separation properties that decrease significantly as the measurement temperature rises.

Furthermore, JP-A-57-30528 presents an example in which two types of plasma polymerized thin films are formed in layers on a porous substrate. Here, a polymer film using organosilane is formed as the first layer, and then a second layer is laminated by plasma polymerizing saturated hydrocarbons, unsaturated hydrocarbons, aromatic hydrocarbons, or derivatives thereof.

The organosilane polymer in the first layer has excellent permeability and mechanical properties, but has insufficient selective permselectivity, while the polymer membrane in the second layer has high permselectivity but has poor mechanical properties. It is said that the strength is not sufficient and the permeability is low. In this example,
One type of plasma-polymerized membrane cannot satisfy all the required characteristics, and a frequent operation of laminating two types of plasma-polymerized membranes is performed.

"Problems to be Solved by the Invention" The purpose of the present invention is to provide a method for producing an excellent gas selectively permeable composite membrane using plasma technology. By using a mixed vapor of a compound and nitrogen gas, ammonia, or an organic compound containing a nitrogen atom, adjusting the composition ratio, and performing plasma polymerization on a polymer support, it is possible to create a product that has the desired gas selective permeation characteristics and is heat resistant. The object of the present invention is to provide a manufacturing method that provides a gas selectively permeable composite membrane having excellent properties such as durability, chemical resistance, and mechanical strength.

``Structure of the Invention''``Means'' The method for manufacturing a gas-selective permselective membrane according to the present invention is to produce a mixed vapor of an organic silane compound consisting of a saturated hydrocarbon group and a nitrogen gas or ammonia or an organic compound containing a nitrogen atom.
The material is supplied to a reduced pressure atmosphere of torr or less, subjected to plasma polymerization under glow discharge, and deposited on the surface of the polymer support. The operating procedure for plasma polymerization, which is a feature of the present invention, will be described in detail below.

(1) Set the polymer support in the reaction vessel of the plasma polymerization apparatus, and use a vacuum pump to pump at least 0.01% of the inside of the reaction vessel.
Exhaust to below torr.

(2) While continuing evacuation, monomer vapor of an organic silane compound consisting of a saturated hydrocarbon group and nitrogen gas or vapor of ammonia or an organic compound containing a nitrogen atom are supplied into the reaction vessel. When using nitrogen gas or ammonia at this time,
This is used as a carrier gas, that is, by placing a gas pipe in a container storing the organic silane compound, introducing nitrogen gas or ammonia, and bubbling it in the organic silane compound, so that the vapor of the organic silane compound and the nitrogen gas or acetylene It is also possible to introduce a mixed gas into the reaction vessel. In general, the organic silane compound and the nitrogen gas or ammonia or the organic compound containing a nitrogen atom may be supplied independently and separately under control. These gas flow rates are controlled via a mass flow controller. Further, the supply ratio of the organic silane compound and the nitrogen gas, ammonia, or an organic compound containing a nitrogen atom is determined by considering the desired permeation characteristics of the membrane and the material of the polymer support. The nitrogen atom imparts polarity to the polymer and allows it to exhibit functions such as selectivity and adhesiveness, while the organic silane compound imparts excellent mechanical strength and permeability.

These gases are introduced and the exhaust speed is adjusted to set the pressure inside the reaction vessel to 5 torr or less. If the pressure is high, the discharge becomes unstable and the energy required for the reaction is insufficient.

(4) Apply electric power and perform glow discharge. Power depends on equipment factors (electrode construction, reactor volume, etc.) and other operating conditions (
The optimum value changes depending on the pressure camotum flow rate, etc.), but if it is too low, the polymer will have a low molecular weight and will not exhibit sufficient properties.
If too much is given, it will cause deterioration of the polymer support, so generally 10 Watts to 200 Watts
It operates between s.

(5) The process is continued for a predetermined period of time to complete the operation after depositing a plasma-polymerized thin film of the required thickness on the polymer support.

The organic silane compound used in the present invention is represented by the following structural formula.

Rn S+ f(4-n n ; 2
Integer R of ~4; CHs -9CH3CH! 1- These organic silane compounds consisting of saturated hydrocarbon groups can be plasma-polymerized to provide a thin film with high flexibility and excellent gas permeability.

Specific examples include tetramethylsilane, trimethylsilane, diethylsilane, and triethylsilane. These organic silane compounds are used as one component, and the other component is selected from nitrogen gas, ammonia, or an organic compound containing a nitrogen atom. Examples of organic compounds containing nitrogen atoms include allylamine, nibutylamine, diethylamine,
Aniline, pyridine, picoline, lutidine, etc. can be mentioned. The two components are polymerized simultaneously to form a thin film that is permeable to gases and has excellent adhesion to the polymeric support.

The polymeric supports on which these plasma-polymerized thin films are deposited are
Various materials can be used by devising usage conditions.

Examples of materials with excellent heat resistance, chemical resistance, and mechanical strength include polysulfone, polyphenylene oxide, polyaromatic ester, polyimide, polytetrafluoroethylene, polydimethylsisexane, and polyphenylsiloxane. Moreover, polyethylene, polypropylene, cellulose acetate, etc. can also be mentioned as general-purpose materials. It is generally advantageous for polymer supports made of these materials to be porous from the viewpoint of gas permeability. However, plasma polymerization alone results in pores so large that it is difficult to block them.

"Operation" Plasma polymerization is a unique polymerization method in which monomers are activated with radicals, ions, or excited species by the action of an electric field in a reduced pressure system, and are sequentially combined to increase the molecular weight. The polymer is inferior and has a molecular structure rich in branched and cross-linked structures, and generally has excellent heat and chemical resistance, but tends to generate internal stress in the direction of expansion and can be deposited thickly. Another drawback is that defects such as cracks are likely to occur. However, among various organic compounds, compounds containing silicon generally tend to form plasma polymerized films with low internal stress and excellent flexibility. In particular, a polymer film made of an organic silane compound comprising saturated hydrocarbon groups provides a thin film with high flexibility and excellent gas permeability. - The atomic atoms are better incorporated into plasma polymerization traps (compared to oxygen atoms), exhibit polarity, and provide selectivity and adhesive properties. When a plasma-polymerized membrane is deposited on a polymer support to form a gas selectively permeable composite membrane, the adhesion between the polymer support and the plasma-polymerized membrane interface becomes a practically important property. Furthermore, the gas permeation mechanism is expressed as the product of dissolution and diffusion, and the polarity of nitrogen atoms magnifies the difference in dissolution depending on the type of gas.

In this way, plasma polymerization of an organosilane compound consisting of a saturated hydrocarbon group and an organic compound containing nitrogen gas, ammonia, or a nitrogen atom results in high gas selective permeability, as well as improved mechanical strength and adhesion to the support. It is possible to create a composite membrane with excellent gas selective permeability.

Further, in the production method according to the present invention, by controlling the two components independently, it is possible to adjust the membrane quality and gas selective permeability over a wide range.

Next, examples will be shown to specifically explain the present invention.

In addition, the permeation rate and separation coefficient shown in the examples are AST
Based on the M method (pressure method), permeated components were separated and detected using a gas chromatograph, and determined by quantitative determination. Moreover, the measurement was performed in an atmosphere at 30°C. The unit of gas permeation rate is an (STP)/aIIffi.
-sec-CmHg, and the separation coefficient is the ratio of the permeation speed of each scum.

Example 1 20% by weight of polyetherimide resin (ULTEM; Japan Engineering Plastics ■Hanuri) was mixed with N-methyl 2
Dissolve it in 80% by weight of pyrrolidone and adjust the dope solution.This dope solution? It was cast onto a smooth Nakara glass plate to a thickness of 300μ using a doctor knife, and the glass plate was immersed in distilled water. After the film had coagulated and peeled off, it was washed with water for 2 hours and heated to 45°C.
The mixture was dried for 24 hours at 80° C. and then for 24 hours at 80° C. to obtain an asymmetric pore membrane with a thickness of about 170 μm. The gas selective permeability of this asymmetric pore membrane was measured and the first-order value was obtained: oxygen permeation rate Qo, I = 1.2 x 10-5
Nitrogen permeation rate QNg = 1. I x 10-5 separation factor (zOt/Nt = 1.1) This asymmetric pore diameter membrane was set as a polymer support in a Pelger type plasma reaction vessel having parallel plate electrodes inside. A high frequency power source is connected, and a gas line for monomer supply is introduced into a two-line reaction vessel, and the two discharge ports are close to each other.After the inside of the reaction vessel is sufficiently evacuated to 0.01 torr or less, Diethylsilane was supplied from one gas line at a flow rate of 5 an3/min, and N2 was supplied from the other gas line at a flow rate of 5 an3/min, and glow discharge was performed for 15 minutes at an output of 20 W to attach the plasma polymerized membrane to the support. The gas selective permeability of the resulting composite membrane was as follows.

Oxygen permeation rate Qo2=5. I x 10-6 nitrogen permeation rate QN2=9. ．． 6 x 10-' Separation coefficient α04/N2 = 5.3 Examples 2 to 3 The asymmetric pore diameter membrane obtained in Example 1 was deposited on a polymer support as shown in Table 1. Plasma polymerization was performed using an organic silane compound consisting of a saturated hydrocarbon group and an organic compound containing a nitrogen atom. Table 2 shows the gas selective permeability of the composite membrane obtained.

Table 1: Plasma polymerization operation conditions Table: 2: Gas selective permselectivity of composite membrane ``Effects of the present invention'' The method for producing a gas selectively permeable composite membrane using plasma polymerization of the present invention has excellent flexibility and high gas permeability. Two types of organic compounds are used: an organic silane compound consisting of a saturated hydrocarbon group that provides a polymeric membrane that exhibits permeability, and an organic compound containing nitrogen gas or ammonia or a nitrogen atom that exhibits polarity and provides high selectivity and adhesion. A method is provided in which membrane quality and gas selective permeability can be adjusted over a wide range by using components.

Claims (1)

[Claims] (1) Structural formula; R_n-Si-H_4_-_n n;2
An integer R of ~4; CH_3-, CH_3CH_2- An organic silane compound represented by CH_3-, CH_3CH_2- and nitrogen gas or ammonia or a vapor of an organic compound containing a nitrogen atom are supplied to an atmosphere of 5 torr or less, and plasma polymerized under glow discharge to form a polymer. A method for producing a gas selectively permeable composite membrane, which comprises depositing it on the surface of a support.