JPH0641214A - Method of plasma-initiated polymerization - Google Patents

Abstract

PURPOSE:To obtain a high-molecular polymer at a low cost by causing a monomer vapor to generate an ionized gas plasma under a pressure of about 1-atm, causing the plasma to initiate the polymn. of a monomer, and carrying out most part of the polymn. in the absence of the plasma. CONSTITUTION:A monomer (or an aq. soln. or emulsion of the monomer) (e.g. a 50% aq. soln. of acrylamide) 2 is put into a treating chamber 1 where a plasma of the atmospheric pressure is generated; while a gas (e.g. helium) is being supplied through a gas supply pipe 3, voltage from an a.c. supply 4 is applied to a conductive pipe electrode 5 to form a discharge zone between electrodes 5 and 6 to thereby initiate the polymn. in a similar way to the conventional plasma-initiated polymn.; after a plasma is generated for a predetermined time, the gas supply pipe 3 and an exhaust pipe 7 are closed; and while the temp. of the treating chamber 1 is kept constant, the polymn. is conducted. In the above process, an ionized gas plasma is generated under a pressure of 0.2-3atm, pref, about 1atm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma-initiated polymerization method in which the initiation of polymerization of a monomer is initiated by atmospheric pressure plasma.

[0002]

2. Description of the Related Art The conventional plasma-initiated polymerization method involves reducing the pressure (0.01 to 100) to a vapor of a liquid, a solid monomer or an aqueous solution or emulsion thereof.
An ionized gas plasma is generated by applying a voltage of 10 to 500 W under a pressure of about mmHg), and a polymerization active species is generated by the ionized gas plasma. By bringing it into contact with the surface, the growth reaction of polymerization starts in the liquid or solid monomer, and after a lapse of a predetermined time,
The contact of the ionized gas plasma with the partially polymerized monomer before reaching the final molecular weight is stopped, and the partially polymerized monomer is post-polymerized in the absence of the ionized gas plasma. That is, only the polymerization initiation reaction is carried out in the gas phase, and the subsequent growth and termination reactions are carried out in the condensed phase (liquid phase or solid phase).

This plasma-initiated polymerization method is described, for example, in "Nagata et al .; J. Polym. Sci, Polym. Lett.
Ed. , 16, p309 (1978) "," D. Johnson et al .; Macromolecule, 14, p118 (198).
1), JP-B-59-25807, 54-118483
As described in Japanese Patent Laid-Open Publication No. JP-A No. 2003-242242, after the plasma is contacted for a short time, post-polymerization occurs in a living manner. Differently, a soluble polymer can be obtained while maintaining the chemical structure of the starting monomer, which facilitates reaction analysis. Further, since it has a feature that it is a catalyst-free polymerization that does not contain impurities such as a radical initiator and an inorganic salt, development of various functional polymer compounds is expected.

In the above-mentioned conventional plasma polymerization method, low-temperature plasma (non-equilibrium plasma) is used to generate polymerization active species. However, since low-temperature plasma is usually generated under a reduced pressure of 10 Torr or less, the conventional plasma polymerization method is used. When the legal process is carried out industrially, a large vacuum device is required, which increases equipment costs and processing costs. In addition, since plasma is brought into contact with a solution of a monomer to be polymerized under reduced pressure, the monomer solution or the like is evaporated, which causes a change in the composition of the solution, and a target polymer may not be obtained. is there. Therefore, in order to prevent the change in the solution, it is necessary to freeze the monomer solution using liquid nitrogen or the like, and the manufacturing process is complicated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plasma-initiated polymerization method which is easy to produce and which can obtain a desired polymer inexpensively and reliably.

[0006]

Means for Solving the Problems and Actions The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, start the polymerization of the monomer by generating an ionized gas plasma in the vapor containing the monomer, and In the plasma-initiated polymerization method in which most of the polymerization is completed in the absence of plasma, the generation of the ionized gas plasma is carried out at a pressure of 0.2 to 3 atm, preferably at a pressure of about 1 atm so that the solvent can be dissolved. The inventors have found that a soluble ultra-high molecular weight polymer can be produced safely, in large quantities, efficiently, economically and with energy saving, and have completed the present invention.

The present invention will be described in more detail below. In the plasma-initiated polymerization method of the present invention, the polymerization of the monomer is initiated by generating an ionized gas plasma in the vapor containing the monomer, and in the absence of plasma. It completes most of the polymerization.

Here, examples of the monomer to which the present invention can be applied include unsaturated organic compounds having one or more double bonds or triple bonds. Further, although it can be applied to a diene and a monomer having a larger number of double bonds, the monomer to which the present invention is applied is preferably a monoethylene type monomer, and of these, a vinyl monomer is particularly preferable. Specific examples of vinyl monomers include methyl acrylate, ethyl acrylate, butyl acrylate, ethylhexyl acrylate, lauryl acrylate, dodecyl acrylate, stearyl acrylate, cyclohexyl acrylate, benzyl acrylate, and similar methacrylates. Acrylic acid and methacrylic acid alkyl esters, acrylic acid, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate, ethylene glycol diacrylate , Diacrylic acid 1,3-butylene glycol, triacrylic acid trimethylolpropane, acrylic acid dimethylaminoethyl methyl chloride salt, acrylic acid ant , Acrylamide, acrylamido 2-methylpropane sulfonic acid,
Acrylic acid derivatives such as isopropyl acrylamide, methacrylic acid and methacrylic acid derivatives similar to acrylic acid derivatives, copolymers of the above monomers, copolymers of the above monomers with other vinyl monomers, of the above monomers and non-vinyl monomers Copolymer, styrene and its derivatives,
Examples include ethylenically unsaturated monomers such as ethylene and propylene.

The above-mentioned monomer can be used in a substantially pure monomer state (solid or liquid) or in the form of a solution, and if necessary, in the form of an emulsified liquid. As the solvent, either an organic solvent or an inorganic solvent can be used as long as it can completely dissolve the monomer. Examples of the organic solvent that dissolves the monomer include ketones such as benzene and acetone, and alcohols such as methyl alcohol.
Examples of the inorganic solvent include water and carbon disulfide. The monomer concentration in the solution is preferably 0.1 to 100% (% by weight, the same applies hereinafter), and particularly preferably 10 to 60%.

The emulsion is prepared by mixing a water-insoluble monomer among the above monomers with an aqueous medium containing an emulsifier and emulsifying the mixture. The emulsifier is not particularly limited as long as it can uniformly emulsify the above monomer in an aqueous medium, but is not particularly limited, such as alkali soap, organic amine soap, sulfate of higher alcohol or aromatic alcohol, and the like. Surfactant or sodium polystyrene sulfonate,
Polymer compounds such as partially saponified polyvinyl acetate and polyether are preferred. Also, a monomer containing a hydrophilic group or a hydrophobic group in one molecule such as hydroxyethyl methacrylate can be used.

The amount of the emulsifier to be used is not particularly limited, but in order to emulsify the water-insoluble monomer in an aqueous medium, it is usually preferable to set it to 0.1% based on the total amount charged.

Examples of the aqueous medium include water, a mixture of water and alcohols such as methanol, ethanol and butanol, and a mixture of water and ketones such as acetone and methyl ethyl ketone. It is preferable to use water alone. . When an aqueous medium, especially water, is used, the polymerization rate will be significantly higher. The monomer concentration in the aqueous medium is 0.1 to 90.
%, Preferably 1-65%, more preferably 10-60
%. Generally, in the case of aqueous medium, the monomer concentration is 50%
At that time, the polymerization rate is maximized, and there is a tendency that the polymerization rate decreases below or above it.

The present invention uses a vapor containing a monomer of 0.2 to 3
The polymerization of the monomer is started by generating an ionized gas plasma at a pressure of atmospheric pressure, preferably at a pressure of about 1 atm. However, in order to obtain an atmospheric pressure plasma stably at a low voltage, It is preferable to use a gas that is easily discharged. Specific examples of such a gas include helium, argon, an inert gas such as neon, nitrogen,
One or two of non-polymerizable gas such as hydrogen, organic gas, etc.
Mixtures of more than one gas can be used. Of these, helium is particularly preferably used. Further, it is possible to mix a gas other than the above-mentioned gases as necessary.

These gases do not necessarily have to be gaseous at room temperature, and the supply method is selected depending on the temperature of the discharge region, the state at room temperature (solid, liquid, gas).
That is, if it is gaseous at the temperature of the discharge region or at room temperature, it can be flowed into the processing container as it is, and if it is liquid, if the vapor pressure is relatively high, the vapor can be left as it is. The liquid may be introduced, or the liquid may be bubbled with an inert gas or the like to be introduced. On the other hand, when it is not in a gaseous state and has a relatively low vapor pressure, it can be used in a state of being in a gaseous state or a high vapor pressure by heating.

As a method of generating atmospheric pressure plasma according to the present invention, any method can be adopted as long as it can discharge at a pressure near atmospheric pressure. The voltage application method can be broadly divided into two types: direct current and alternating current.

When an internal electrode type device is adopted as the AC discharge device, it is recommended to cover at least one of the electrodes with an insulator in order to easily obtain stable atmospheric pressure plasma. Further, when the processing chamber is made of an insulating material such as glass, the external electrode method can be adopted. Further, it is also possible to use a coil type discharge or a waveguide type discharge. In the case of direct current discharge, it is preferable that neither the high voltage application side electrode nor the ground side electrode is covered with an insulator in order to form and stabilize direct current discharge by direct electron inflow from the electrode.

The plasma-initiated polymerization in the present invention is one in which the above-mentioned atmospheric pressure plasma is used to initiate the polymerization, and most of the polymerization is completed in the absence of plasma.
In this case, it is preferable that oxygen is removed from the system where plasma is generated, and any method can be adopted as the oxygen removing means as long as it is a method capable of removing oxygen from the system. For example, freeze, degas, or A
A method of bubbling with an inert gas such as r or He or a general-purpose gas such as N ₂ can be used.

The input energy when the ionized gas plasma is brought into contact with the above-mentioned monomer cannot be said unequivocally depending on the form of the apparatus, but generally 1 to 3 × 10 ⁴ J is sufficient. The post-polymerization is performed by bringing the emulsified solution into contact with plasma and then leaving it at a constant temperature for several hours. The polymerization rate during the plasma initiation period is significantly smaller than the post-polymerization rate, and usually does not exceed 2%. The post-polymerization time varies depending on the type of monomer and is not particularly limited. Further, the post-polymerization temperature is also not limited as it varies depending on the kind of the monomer, but is usually 0 to 80 ° C, and particularly preferably 10 to 60 ° C. If the temperature is lower than 0 ° C, the post-polymerization may not be able to proceed within the above-mentioned input energy range.

The plasma polymerization apparatus used in the present invention is not particularly limited, but for example, the apparatus shown in FIG. 1 can be used. In this apparatus, a monomer (or an aqueous solution of a monomer or an emulsion of a monomer) 2 to be polymerized is housed in a processing chamber 1 for forming an atmospheric pressure plasma, the above-mentioned gas is supplied from a gas supply pipe 3, and an AC power supply 4 is provided. To conductive pipe-shaped electrode 5
A voltage is applied to the electrodes to form a discharge region between the electrodes 5 and 6, and the polymerization is initiated by the same method as the conventional plasma initiation polymerization method. The electrode 6 is grounded. The electrodes 5 and 6 are preferably covered with an insulator. After the plasma is generated for a predetermined time, the gas supply pipe 3 and the exhaust pipe 7 are closed,
The processing chamber 1 is held in a constant temperature bath (not shown) to carry out post-polymerization.

[0020]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 Atmospheric pressure plasma was generated using the same apparatus as shown in FIG. Acrylamide monomer (AAM) in processing chamber 1 made of Pyrex glass
20 g of a 50% aqueous solution of was added, and the aqueous solution was bubbled with helium gas for 1 hour to remove dissolved oxygen, and the processing chamber 1 was replaced with gas.

Diameter 6 with helium gas still flowing
An AC plasma having a frequency of 5 kHz and a voltage of 3 kV is applied between the electrodes 5 and 6 made of a copper tube of mm to generate atmospheric pressure plasma for 60 seconds in the processing chamber 1 (input energy 21J), and AA
M aqueous solution was contacted. Then, the supply pipe 3 and the exhaust pipe 7 are closed, the processing chamber 1 is placed in a constant temperature water bath at 50 ° C. for a predetermined time with shaking, and post-polymerization is performed for 2 hours, and then the container is cooled with liquid nitrogen to perform polymerization. Stopped.

The polymer obtained was dried and weighed to determine the yield (polymerization rate). Moreover, the molecular weight was measured using GPC (made by Tosoh Corporation). The results are shown in Table 1. In Table 1, the input energy when plasma is generated is a value calculated from (power (W) × (time (second))).
The yield was determined from (weight of polymer obtained) / (weight of charged monomer).

Comparative Example 1 Prepared in the same manner as in Example 1,
After reducing the pressure to 0.1 Torr, it remains frozen at 13.56
A radio frequency oscillator with a control unit of MHz was applied at an output of 50 W to generate plasma for 30 seconds, after which the same post-polymerization as in Example 1 was performed and the same measurement was performed. The results are shown in Table 1. Note that the input energy differs from that in Example 1 because the discharge efficiency is different and therefore the polymerization efficiency is also different.

[Embodiment 2] Using a device similar to that of Embodiment 1, styrene emulsion (styrene 22.%, DB
S3.8%) 20 g was added and the same operation as in Example 1 was performed. An AC voltage having a frequency of 5 kHz and a voltage of 2.5 kV was applied, atmospheric pressure plasma was generated in the processing chamber 1 for 300 seconds (input energy 21 J), and brought into contact with the AAM aqueous solution. Then, the same post-polymerization as in Example 1 was performed at 50 ° C. for 7 hours, and the same measurement was performed. The results are also shown in Table 1.

[Comparative Example 2] A styrene emulsion was prepared in the same manner as in Example 2, plasma was used in the same manner as in Comparative Example 1, plasma was generated at 50 W for 30 seconds, and post-polymerization was performed at 50 ° C for 7 seconds. Styrene was polymerized for a period of time and the same measurement was performed. The results are also shown in Table 1.

[0027]

[Table 1]

[0028]

According to the present invention, a high molecular weight polymer can be obtained without destroying the chemical structure of the starting monomer and without impairing the characteristics of the plasma-initiated polymerization method such as no catalyst. Since there is no need for depressurization, composition change can be prevented by evaporation of the monomer solution, and composition change can be prevented by evaporation of the monomer solution because there is no need for freezing operation. Also in this case, there is an advantage that the processing cost and the equipment cost are reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of an atmospheric pressure plasma polymerization apparatus used in the present invention.

[Explanation of symbols]

 1 Processing Room 2 Monomer 3 Gas Supply Pipe 4 AC Power Supply 5 Electrode 6 Electrode 7 Discharge Pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masato Yoshikawa 3-5-9 Ogawa Higashi-cho, Kodaira-shi, Tokyo (72) Inventor Itsuo Tanuma 3405-181 Kashihara, Sayama-shi, Saitama Prefecture (72) Inventor Toshio Naito Kawasaki, Kanagawa 969-1 Makinagi, Miyamae-ku, Ichi (72) Inventor Yukihiro Kusano 1-50-15 Nishikoigakubo, Kokubunji, Tokyo (72) Inventor Setsuo Akiyama 28-5, 72, Miyashitahonmachi, Sagamihara-shi, Kanagawa (72) Inventor Sachiko Okazaki 2-20-11 Takaido Higashi, Suginami-ku, Tokyo (72) Inventor Masuhiro Ogoma 843-15 Shimoshinkura, Wako City, Saitama Prefecture

Claims (1)

[Claims] 1. A plasma-initiated polymerization process in which ionized gas plasma is generated in a vapor containing a monomer to initiate polymerization of the monomer, and most of the polymerization is completed in the absence of plasma. Is initiated at a pressure of 0.2 to 3 atmospheres, a plasma-initiated polymerization method.