JPH0417204B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a polymer by plasma-initiated polymerization of a monomer having a polymerizable unsaturated bond. (Prior Art) It has been known to polymerize monomers using ionized plasma generated under vacuum, and has been proposed, for example, in US Pat. No. 2,257,177.
However, these polymerizations are generally referred to as plasma polymerization, in which monomers are brought into continuous contact with ionized gas plasma, and the resulting polymers generally have an extremely large number of crosslinked structures, and are It is insoluble in organic materials and thermally infusible, and is extremely difficult to process as an organic material, so it is only used in some fields such as surface treatment, separation membranes, and films. On the other hand, JP-A-54-118483 provides a plasma-initiated polymerization method as a method for obtaining a polymer having an ultra-high molecular weight and a substantially linear structure. However, in this method, the polymerization rate is slow and it takes an extremely long time to complete the polymerization, resulting in very poor productivity.
Furthermore, Japanese Patent Laid-Open No. 59-25807 proposes a plasma-initiated polymerization method in which the polymerization rate is increased by using an emulsifier and polymerizing in an emulsified state.
This method increases the polymerization rate, but since it uses an emulsifier, the emulsifier gets mixed into the resulting polymer, making it impossible to obtain a completely pure polymer.Additionally, the polymer cleaning process requires many steps and is extremely difficult. It cannot necessarily be said that it is an industrially easy and inexpensive manufacturing method, as it requires a lot of energy. (Problems to be Solved by the Invention) The present inventors have completed the present invention as a result of intensive studies to eliminate the conventional defects. An object of the present invention is to provide a polymerization method for obtaining a substantially linear, ultra-high molecular weight polymer without contamination with impurities, industrially easily and economically at low cost. (Means for Solving the Problems) The present invention provides a monomer () having a polymerizable unsaturated bond and a solvent for the monomer () and a monomer () having a polymerizable unsaturated bond.
The method is characterized in that a mixed solution of the polymer and an organic solvent (2) as a non-solvent is irradiated with ionized gas plasma, and then post-polymerized in the absence of the plasma to sequentially precipitate the resulting polymer. The monomer () used in the present invention is not particularly limited as long as it is a monomer that undergoes plasma-initiated polymerization, but monomers having one unsaturated double bond are more preferable in terms of versatility, processability, and homogeneity of the polymer. However, diene compounds such as butadiene and pentadiene, monomers having two unsaturated double bonds such as diacrylate compounds and diarylate compounds, or other monomers having three or more double bonds may also be used as appropriate depending on the purpose. For example, by adding a small amount of a monomer having two or more of these double bonds, it is possible to obtain a polymer that is insoluble in solvents, has good heat resistance, and has improved mechanical properties. Monomers () include water-soluble monomers such as acrylamide, acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, etc., alkyl vinyl ethers, alkyl esters of acrylic acid, alkyl esters of methacrylic acid, etc. Water-insoluble monomers can be used. Among the water-insoluble monomers, acrylic esters or methacrylic esters represented by the following general formula have good polymerizability and are more preferable. general formula

[Formula] (wherein l is 0 or 1, and m is an integer of 1 to 12.) Particularly preferred are methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, or butyl methacrylate. The solvent () is not particularly limited as long as it is an organic solvent that is a solvent for the monomer () and a non-solvent for the polymer of the monomer (). For example, methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, allyl alcohol, tert-butyl alcohol, furfuryl alcohol, ethylene glycol, propanediol, pentamethylene glycol, 2-methylbutanediol, monoacetyl glycol, glycerin, etc. alcohols, formamide, N-
Ketones and amides such as ethyl acetamide, ethers such as 1,3-dioxane and 1,4-dioxane, carboxylic acids such as acetoacetic acid, α-chloropropionic acid, propionic acid, butyric acid, glyceric acid, allylamine, isoallylamine , ethylamine, dimethylpyridine, pyridine, butylamine, propylamine, benzylamine, N
- Can be selected from amines such as methylpyridine. In particular, when acrylic esters or methacrylic esters represented by the above general formula are used as monomers (), alcohols such as C ₄ or less monools, diols or triols, 1,3
-dioxane, 1,4-dioxane, etc. are preferred. The amount of solvent () used is usually 10 to 95% by weight, preferably 15 to 90% by weight, more preferably 20% by weight.
~80% by weight, particularly preferably 25-75% by weight. If the amount of the solvent () is less than 10% by weight, the resulting polymer will not be sufficiently precipitated. If it is more than 95% by weight, it is possible to produce a polymer, but the productivity decreases, which is not preferable. When the amount of solvent () is 20 to 80% by weight, productivity is high, and precipitation, separation, and recovery of the produced polymer are easy. In particular, in order to improve demonomerization and solvent removal from the produced polymer by filtration, centrifugation, compression, etc. and washing of the produced polymer, it is preferable that the amount of the solvent () is 25 to 75% by weight. If the mixed solution of monomer () and solvent () contains air or oxygen, plasma-initiated polymerization may not occur, the polymerization rate may decrease, or the molecular weight of the resulting polymer may decrease. You need to exercise enough qi. Degassing methods include blowing an inert gas such as helium, argon, or nitrogen into the mixed solution to drive out dissolved oxygen;
Alternatively, it is effective to repeatedly freeze and thaw the mixed solution under reduced pressure to remove dissolved oxygen. A sufficiently degassed (deoxygenated) mixed solution has a temperature of 10 ^-1 ~
It is degassed under reduced pressure to 10 ^-4 Torr and irradiated with high frequency under the same degree of vacuum to generate ionized gas plasma (hereinafter simply referred to as plasma). Plasma can be generated by any known method. For example, "Applied Techniques of Plasma Chemistry" (Willey, New York, 1974) written by J.R. Holohan and AT Bell, and "Plasma Chemistry of Polymers" (Detzker, New York, 1974), written by M. Chien.
1976) etc. can be preferably referred to. For example, an ionized gas is placed under vacuum between parallel plate electrodes connected to an International Plasma Corporation Model 3001 radio frequency generator. Plasma can be generated using parallel plate electrodes either outside or inside the vacuum chamber. In other techniques, an external induction coil can generate an electric field that generates a plasma of ionized gas. Still other techniques may use spaced, oppositely charged electrode points placed directly into a vacuum chamber to generate a plasma, and so on. Plasma operating parameters vary depending on monomer, container shape, material, etc. Generally preferred is a glow discharge with electron radiation producing ionization in the gas phase using a reduced pressure gas. When plasma is generated in a room under reduced pressure, the voltage between the electrodes needs to have a value sufficient to ionize or decompose the gas. The ionized or decomposed gas becomes conductive and a stable plasma can be maintained over a wide range of current. Although the exact composition of plasma is unknown, it contains electrons, ions, radicals,
and others are believed to exist. According to the present invention, as will be described later, the active species in the plasma directly or indirectly initiate a growth reaction of non-vapor phase monomers that come into contact with the plasma. In the direct method, the ions or radicals themselves create active sites at the interface between the plasma and the non-vaporous monomer;
Polymerization of the monomer starts from the active site. In indirect methods, ions or radicals in the plasma initiate polymerization of the monomers by causing a chain transfer reaction between the non-vaporous monomers in contact with the plasma. Ions and/or radicals in the plasma are generated and supplied when plasma electrons collide with monomers or organic solvent molecules generated from a mixed solution. Monomers and organic solvent molecules can be easily generated by reducing the pressure in the system. Alternatively, any other ionized gas may be present to generate a plasma, thereby initiating polymerization of the non-vapor phase monomer. Gases for this purpose include carbon tetrachloride, helium, neon, argon, nitrogen, and the like. When a glow discharge type plasma is used, excessive evaporation of monomers and organic solvents causes a decrease in the degree of vacuum and hinders plasma generation. Therefore, if these vapor pressures are high, it is necessary to cool the mixed solution or increase the degree of vacuum using a vacuum pump or the like. The degree of vacuum in the vacuum chamber is usually 10 ^-4 to 10 ⁰
Torr, preferably 10 ⁻³ to 10 ⁻¹ Torr. When the plasma is generated by glow discharge, the output is usually 20 to 200 watts, preferably 40 to 150 watts, and the irradiation time is usually 1 to 3,600 seconds, preferably 10 to 600 seconds. Of course, the output may be variable, and the irradiation may be performed intermittently. As described above, by irradiating the plasma, active species are generated directly or indirectly in the non-vapor phase monomer components, and thereafter, the monomer growth reaction proceeds in the absence of plasma. This polymerization behavior in the absence of plasma is called postpolymerization.
In post-polymerization, the polymerization rate is low at low temperatures. At higher temperatures, the diffusion rate of the monomer to the active species increases and the polymerization rate increases, but the probability of abnormal reactions also increases, and the occurrence of branching and cross-linked structures increases, resulting in a decrease in the quality of the resulting polymer. Therefore, the post-polymerization rate is usually 100°C or less, preferably 0 to 80°C,
More preferably, the temperature is 20 to 60°C. The polymer produced by post-polymerization gradually precipitates from the mixed solution. Therefore, the produced polymer can be recovered by simply separating the polymerization solution in which the post-polymerization has proceeded, followed by simple washing and drying, which is a great industrial advantage over conventional methods. (Effects of the invention) Since the polymer obtained by the method of the present invention is obtained in the form of granules or powder, it is not only extremely easy to handle after polymerization, but also unreacted monomers, common solvents, etc. can be recovered and reused. It has the characteristic that it is very easy. Furthermore, since no polymerization catalyst or emulsifier is used in the reaction, the purity of the obtained polymer is extremely high.
Furthermore, since it was obtained by plasma-initiated polymerization, it has a very large molecular weight, which is advantageous industrially, and it is also an excellent material. (Example) Hereinafter, the present invention will be specifically explained by showing examples. Example 1 Methyl methacrylate (2) and methanol (2) were placed in a pressure-resistant ampoule having an inner diameter of 10 mm, a length of 30 mm, and a content of 25 ml at the ratio shown in Table 1 to form a 10 ml homogeneous solution. The ampoule containing the solution was frozen in liquid nitrogen and dissolved in tap water three times under the reduced pressure of a vacuum pump to almost completely remove dissolved oxygen in the mixed solution. Then, after freezing again with liquid nitrogen,
An ampoule was inserted between a pair of parallel plate electrodes connected to a 13.56 MHz high frequency power source in a vacuum of 10 ^-2 Torr, and plasma was generated by glow discharge for 60 seconds at an output of 100 watts. After plasma irradiation, the ampoule was fused with a propane/oxygen flame gas burner and post-polymerized in water at a constant temperature of 35°C for 3 days. After post-polymerization, the ampoule was opened and the contents were precipitated into a large amount of methanol. The polymer was precipitated. The polymer was washed with methanol and water, thoroughly dried in a vacuum dryer, and then recovered. The intrinsic viscosity [η] of the produced polymer was measured in a benzene solution at a temperature of 30°C using an Ubbelohde viscometer. The results are shown in Table 1.

【table】

[Table] Example 2 In a pressure-resistant ampoule with an inner diameter of 10 mm, a length of 30 mm, and a content of 25 ml, an organic solvent () that is a solvent for methyl methacrylate () and a non-solvent for polymethyl methacrylate was added at a ratio of 30:70 (%). ) with the ratio of 10ml and added it. Plasma irradiation and postpolymerization were performed in the same manner as in Example 1. The results are shown in Table 2.

【table】

Claims (1)

[Claims] 1. A mixed solution of a monomer () having a polymeric unsaturated bond and an organic solvent () that is a solvent for the monomer () and a non-solvent for the polymer of the monomer (). ,
1. A method for producing a polymer, which comprises irradiating an ionized gas plasma and then performing post-polymerization in the absence of the plasma to sequentially precipitate the resulting polymer. 2. The method according to claim 1, wherein the monomer () is water-insoluble. 3. The method according to claim 1, wherein the monomer () is represented by the following general formula. General formula [Formula] (However, l represents 0 or 1, and m represents an integer of 1 to 12.) 4 Claims in which the monomer () is methyl methacrylate, ethyl methacrylate, propyl methacrylate, or butyl methacrylate 1
The method described in Section 3 or Section 3. 5. The method according to claim 1 or 3, wherein the monomer () is methyl acrylate, ethyl acrylate, propyl acrylate, or butyl acrylate. 6. The method according to claim 1, wherein the solvent () in the mixed solution is 10 to 95% by weight. 7. The method according to claim 1 or 6, wherein the solvent () in the mixed solution is 15 to 90% by weight. 8. The method according to claim 1, 6 or 7, wherein the solvent () in the mixed solution is 20 to 85% by weight. 9. The method according to claim 1, wherein the ionized gas plasma is degassed to 10 ^-4 to 10 ^-1 Torr and then irradiated under vacuum at 20 to 200 Watts for 1 to 3,600 seconds. 10. The method according to claim 1 or 9, wherein the ionized gas plasma is degassed to 10 ^-4 to 10 ^-1 Torr and then irradiated under vacuum at 40 to 150 Watts for 10 to 600 seconds. 11. The method according to claim 1, wherein the temperature of the post-polymerization is 100°C or less. 12. The method according to claim 1 or 11, wherein the temperature of the post-polymerization is 0 to 80°C. 13. The method according to claim 1, 11 or 12, wherein the post-polymerization temperature is 20 to 60°C.