JPS6287209A - Production of thin film - Google Patents

Abstract

PURPOSE:To obtain the titled thin film whose performance to separate oxygen and nitrogen is especially improved by forming the plasma-polymerized thin film of a mixture of hexafluoropropylene and an aliphatic hydrocarbon on a substrate molded body. CONSTITUTION:Sheets, fibers, tubes, etc., consisting of a high molecular polymer and an inorg. material are used as the substrate molded body. The plasma- polymerized thin film of a mixture of hexafluoropropylene and an aliphatic hydrocarbon such as methane is formed on the substrate molded body. The mixing ratio of both materials is preferably regulated to 100/1-1/10 (by volume). The polymerization can be carried out at a temp. close to ordinary temp. The polymerization is conducted, for example, by using a device having 10cm diameter and 55cm length, the electric power of the radio wave is controlled to 10-200W and the flow rate of the monomer is adjusted to about 0.1-50 cm<3>(STP)/min. The thickness of the thin film is regulated to 0.01-10mum. The permeability coefficient of oxygen can be controlled to about 10<-8>cm<3>(STP)/ cm<2>.sec.cm Hg and the separation ratio of oxygen and nitrogen adjusted to about 3.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention forms a thin film on a base molded body by plasma polymerizing a mixture of hexafluoropropylene (also referred to as hexafluoropropene) and an aliphatic hydrocarbon. The present invention relates to a method for producing thin films useful as electrical materials, separation membranes, etc.

[Conventional technology]

Plasma polymerization refers to the polymerization of monomers by glow discharge in monomers that exist under vacuum and low pressure.In such reactions, the monomers undergo splitting, so if two types of monomers are injected, both monomer components will be separated. Polymers containing the following elements may be produced. The inventor previously
reported that a thin film could be formed on a substrate by plasma polymerization of tetrafluoromethane in the coexistence of methane (J, Macromol, Sci, -ch
em.

Alt(su, pAA/-bqs(lqgco)).

[Problem that the invention seeks to solve]

However, this thin film was not satisfactory in terms of gas separation performance, for example.

Therefore, the present inventor conducted further studies and found that a thin film formed from a mixture of hexafluoropropylene and aliphatic hydrocarbon by plasma polymerization on a basic molded body has excellent performance in separating substances, especially oxygen and nitrogen. The present invention was achieved by discovering that a thin film can be formed.

That is, the present invention resides in a thin film forming method characterized by forming a thin film on a base molded body by plasma polymerizing a mixture of hexafluoropropylene and an aliphatic hydrocarbon.

[Means for solving problems]

To explain the present invention in more detail, the base molded body used in the present invention includes polyethylene, polypropylene,
Polyolefins such as polycoumethylpentene/, polyvinyl chloride, polyacrylonitrile, polymers of vinyl monomers such as polymethyl methacrylate, polymers of fluorine-containing monomers such as polyvinylidene fluoride, polysiloxane, polytrimethylvinylsilane, polytrimethylsilyl Examples include sheets, fibers, and tubes made of silicon-containing polymers such as propylene, polyamides, polyimides, polyethyl cellulose, certain cellulose polymers such as acetyl cellulose, metals, and inorganic materials such as glass. When used as a separation membrane, porous molded bodies of these polymers and inorganic substances are used in the form of sheets, hollow fibers, spirals, tubes, and the like. In addition, coating on the surface of a membrane consisting of a skin layer and a porous layer, which is usually called an asymmetric membrane, or a porous membrane, which is called a composite membrane, 1 nsitu polymerization,
A homogeneous ultra-thin film formed by a method such as plasma polymerization or lamination can also be used as the base molded body. When used for other purposes such as electrical materials and surface modification of plastics, the substrate is selected as appropriate depending on the purpose.

Next, alkanes are used as aliphatic hydrocarbons in the coexistence of hexafluoropropylene.

Alkenes are used. Preferably, a substance that is a gas at room temperature is used, and methane is most suitable.

The ratio of hexafluoropropylene to aliphatic hydrocarbon is not particularly limited, but is preferably 10O:l-l:lO(
(volume ratio), particularly preferably in a ratio of 20:/-i:s (volume ratio).

Next, conditions for plasma polymerization will be explained.

There are no particular restrictions on the polymerization temperature, and it may be around room temperature.

The apparatus for plasma polymerization may be a known one; for example, in the case of an internal electrode system,
olymerSQ1enQ13 Volume 17, gza left page (/
97.7), or the same magazine, volume g, page 3629 (19rp
), the electrodeless method is called Journa.
l of Apl: Ilied Polymar 5ci
Examples include the device described in ence Volume 1j, 2 Cores, page 7 (/q?/). The flow rate of the monomer is related to the size of the device and the amount of electric power.For example, the diameter is 10 cnr, the length is j! The flow rate of the monomer is selected to be about 0.7 to 50 d(STP)/min with a radio wave power of 10 to 200 W in a cm device.

The thickness of the extremely thin film formed on the substrate molded body by plasma polymerization can be controlled by the polymerization time and flow rate. When used as a separation membrane, the thickness of an ultra-thin membrane is preferable because the permeation rate of a thin seed substance is high, but on the other hand, an extremely thin membrane is undesirable because the separation performance deteriorates due to the formation of pinholes. Therefore, normally 0.0/μm~
It is used by forming it on the surface of a base molded body so as to have a film thickness in the range of IO μm.

〔Example〕

Hereinafter, a more specific explanation will be given using Examples and Comparative Examples.

Comparative Example Journal of Applied Polyme
The same type of device as described in r 5aience Volume 2g, page 3429 (Iqg da year), diameter 100 m, length'
A circular Millipore filter (porous membrane manufactured by Millipore Limited, average pore size olopropylene) was introduced into a 100 m internal electrode type polymerization reactor, and an Af current of 75 mA (2
0 KHz), and monomer flow rate gcrd (S
TP) Co-hour plasma polymerization was carried out for 7 minutes at a pressure of /b Pa.

The oxygen and nitrogen permeability coefficients of the plasma polymerized membrane formed on the Millipore filter are calculated from the primary side (gas supply side) of the membrane.
The pressure is / kg / cnt, on the secondary side (permeate side) of the membrane
The pressure was measured in s kg 7 crl.

I got the following results.

Po2=1. oxlo-”Cm”(STP)-What Hago・Sec・mH,9PH2=t,,,2×1O−1
0crtlSrp)-6V/CrI-eec-, mgP
o 2 / PN 2 ==mu7 Note that the thickness of the plasma polymerized film at this time is 0. 'l 68m
Met.

Example / Monomer 3 of hexafluoropropylene and methane
Plasma polymerization was carried out in the same manner as in the comparative example except that a mixture of 2/2 was used, and the oxygen and nitrogen permeability coefficients of the thin film formed on the Millipore filter were measured, and the following results were obtained.

PO, =: Ri, Ri×/θ−' c7IIl(STP
)-αV仝GO・sec-mHJ7pN2=J、+X
/ (7-” 7(S TP) ・ Sird@sθCII
ttnHyPO2/PN2= s, the thickness of the plasma polymerized film at this time is 0.3? It was μm.

From the above results, by mixing hexafluoropropylene with methane and subjecting it to plasma polymerization, the oxygen permeability coefficient increases by about 10 times compared to the case of hexafluoropropylene alone, which is shown by the ratio of oxygen and nitrogen permeability coefficients. It can be seen that the separation performance increases significantly.

Example Using the same membrane as that used in Example 1, the permeation performance of a mixed gas containing 2% of 02 core IN and N27 core was measured.

? , 1I7X 10-'m(STP)/7-t3ec
The composition of the permeated gas obtained at a rate of -tynHji was measured by gas chromatography and oxygen s7. /%, nitrogen qco, 9% results were obtained.

Calculating the permeability coefficients of oxygen and nitrogen from the above results, Pa□==ヲ! ;X10″m (STP) ・ctr
y'crll・sec・cmHlPN, =,?
, 9X10″m1 (STP) aary'cr/b
ae c acmH9, and the separation coefficient determined from the composition of the feed gas and the composition of the permeate gas was α=3.6.

〔Effect of the invention〕

According to the method for manufacturing a thin film according to the present invention, it is possible to obtain a thin film with particularly improved oxygen and nitrogen separation performance.

Claims (1)

[Claims] (1) A thin film manufacturing method characterized by forming a thin film on a base molded body by plasma polymerizing a mixture of hexafluoropropylene and an aliphatic hydrocarbon.