JPH0417205B2 - - 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 water and thermally infusible, and has extremely poor moldability 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 proposes a plasma-initiated polymerization method as a method for obtaining a supermolecular weight polymer having 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 low productivity.
Furthermore, Japanese Patent Application 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 applies ionized plasma to a mixed solution of a monomer () having a polymerizable unsaturated bond, water, and a common solvent () of the monomer () and water. After the irradiation, post-polymerization is performed in the absence of the plasma, and the resulting polymer is sequentially precipitated. 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 diarylate compounds and diacrylate compounds, or other monomers having three or more double bonds can 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, vinyl acetate, alkyl vinyl ethers, alkyl esters of acrylic acid, and alkyl esters of methacrylic acid. Water-insoluble monomers such as
Water-insoluble monomers are more preferable in terms of ease of precipitation of the produced polymer and ease of washing. Among the water-insoluble monomers, acrylic esters or methacrylic esters represented by the following general formula are more preferable because they have good polymerizability. general formula

[Formula] (However, l represents 0 or 1, and m represents an integer of 1 to 12.) In particular, methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, or butyl methacrylate are preferred.
In the present invention, the presence of water as well as the monomer () is essential. The reason why water is effective for plasma-initiated polymerization is not yet known, but degassing can be achieved more effectively through repeated freezing and melting, and the polymerization rate is dramatically higher than in a water-free system. It has this great feature. The ratio of monomer () to water is usually 5:95 to 90:10
(weight ratio), preferably 10:90 to 80:20 (weight ratio), more preferably 15:85 to 70:30
(weight ratio). When the amount of water is less than 10 (weight ratio), the polymerization acceleration effect by water is still insufficient, and when the water amount exceeds 95 (weight ratio), the amount of polymer produced in the polymerization system decreases, which is economically disadvantageous. I'm getting old. As mentioned above, water accelerates at the polymerization rate of plasma-initiated polymerization of monomer (). Mechanically forced stirring of the mixture and water alone is not sufficient. By using a mixed solution of monomer () and water and a common solvent () of monomer () and water, even without the use of an emulsifier, microparticles of monomer () and water that are equivalent to those using an emulsifier can be produced. It is possible to increase the contact area by forming, and
It is possible to achieve a uniform mixed solution of molecular mixing of the monomer () and water, which cannot be achieved even when an emulsifier is used. The solvent () is not particularly limited as long as it is a common solvent for the monomer () and water, but it is easy to handle,
Organic compounds are preferred from the standpoint of ease of recovery and purification, and particularly preferred are poor solvents or nonsolvents for the polymer because they sequentially precipitate the produced polymer and facilitate polymer recovery. Therefore, what to use as the solvent () needs to be appropriately determined depending on the type of monomer () and the mixing ratio with water. 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, ketones and amides such as acetone, formamide, N-ethylacetamide, ethers such as 1,3-dioxane, 1,4-dioxane, acetoacetic acid, α-chloropropionic acid, propionic acid, butyric acid, glycerin Carboxylic acids such as acids, amines such as allylamine, isoallylamine, ethylamine, dimethylpyridine, pyridine, butylamine, propylamine, benzylamine, N-methylpyridine, acetonitrile, acetoxime, butyrolactone,
Examples include glycine ethyl ester. 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 () to be used may be determined as appropriate depending on the degree of water insolubility of the monomer () and the ratio of monomer () to water, but usually the amount of monomer (), water and solvent ( ) is 10% by weight or more, preferably 15 to 90% by weight, more preferably 20 to 80% by weight, particularly preferably 25 to 75% by weight. When the amount of the solvent () is less than 10% by weight, sufficient mixing of the monomer () and water cannot be achieved, and the polymerization rate cannot be sufficiently accelerated. A mixed solution of monomer (), water, and solvent () can take a state from a heterogeneous mixed solution to a homogeneous mixed solution depending on the respective composition ratios. If you want to obtain the produced polymer in the form of relatively small particles or powder, it is preferable that the mixed solution is a homogeneous solution.
Furthermore, if it is desired to obtain the produced polymer as particles with a relatively large particle size, it is better to make the mixed solution a heterogeneous solution. The molecular weight of the produced polymer often changes depending on the monomer () content of the mixed solution, and generally, the higher the monomer () content, the greater the molecular weight of the produced polymer. If the mixed solution of monomer (), water 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. , sufficient deaeration is required. Effective degassing methods include blowing an inert gas such as helium, argon, or nitrogen into the mixed solution to drive out dissolved oxygen, or removing dissolved oxygen by repeatedly freezing and melting the mixed solution under reduced pressure. be. A sufficiently degassed (deoxygenated) mixed solution is 10 ^-1
It is degassed under reduced pressure to ~10 ^-4 Torr, and then irradiated with high frequency waves 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, "Applications of Plasma Chemistry" (Willey New York, 1974) written by J.R. Holohan and AT Bell, and "Plasma Chemistry of Polymers" (Detsker, New York, 1976) written by M. Chien. You can refer to it preferably. 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 potential 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 currents. Although the exact composition of the plasma is unknown, it is believed that electrons, ions, radicals, and others are present. 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 the indirect method, a chain transfer reaction occurs between ions or radicals in the plasma or a non-vaporous monomer in contact with the plasma to initiate polymerization of the monomer. Ions and/or radicals in plasma are monomers generated by plasma electrons from a mixed solution,
Generated and supplied by collision with water or organic solvent molecules. Monomer, water, 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, water, and organic solvents causes a decrease in the degree of vacuum, which actually 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 ⁻¹ 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. By irradiating plasma as mentioned above,
Active species are generated directly or indirectly in the non-vapor phase monomer components, and then 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, but 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 crosslinked structures. There is a decrease in the quality of the produced polymer. Therefore, the post-polymerization rate is usually 100°C, preferably 0 to 80°C.
℃, more preferably 20 to 60℃. 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, water, common solvents, etc. can be recovered. It is characterized by being extremely easy to reuse. 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 described with reference to Examples. Example 1 Methyl methacrylate (2), distilled water, 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 in the ratio (weight ratio) shown in Table 1, and the mixture was thoroughly stirred. The ampoule containing the mixed solution was frozen with liquid nitrogen and dissolved with tap water three times under the reduced pressure of a vacuum pump to almost completely remove dissolved oxygen in the mixed solution. Next, with the mixed solution frozen in liquid nitrogen, the ampoule was inserted between a pair of parallel plate electrodes connected to a 13.56 MHz high frequency power source at a vacuum level of 10 ^-2 Torr, and glow discharge was performed for 60 seconds at an output of 100 W. Generated plasma. After plasma irradiation, the ampoule was fused and sealed with a propane-oxygen flame gas burner and post-polymerized in water at a constant temperature of 25°C for 3 days. After the post-polymerization, the ampoule was opened, unreacted monomers, methanol, and water were removed by deep red drying, and the polymer was recovered. The recovered polymer was further washed with methanol and vacuum-dried again. The intrinsic viscosity [η] of the polymer was measured at 30°C in a benzene solution using an Ubbelohde viscometer. The results are shown in Table 1.

[Table] Example 2 Methyl methacrylate (2), distilled water, and ethanol (2) were placed in the ratio (weight ratio) shown in Table 2 into the same ampoule as used in Example 1, and the mixture was thoroughly stirred. The ampoule containing the mixed solution was subjected to plasma irradiation and post-polymerization in the same manner as in Example 1.

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Claims (1)

[Claims] 1. After irradiating a mixed solution of a monomer () having a polymerizable unsaturated bond with water and a common solvent () of the monomer () and water with an ionized gas plasma, A method for producing a polymer, which comprises post-polymerizing in the absence of plasma and sequentially precipitating 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 Claim 1 in which the monomer () is methyl methacrylate, ethyl methacrylate, propyl methacrylate or butyl methacrylate
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 ratio of monomer () to water is 5:95 to 90:10
(weight ratio). 7 The ratio of monomer () to water is 10:90 to 80:20
(weight ratio). 8. The method according to claim 1, wherein the solvent () is an organic solvent. 9. The method according to claim 1, wherein the solvent () is a poor solvent or a non-solvent for the produced polymer. 10. The method according to claim 1, wherein the mixed solution is a homogeneous solution. 11. The method according to claim 1, wherein the mixed solution is a suspension solution. 12. The method according to claim 1, wherein the content of the solvent () in the mixed solution is 10% by weight or more. 13 The content of solvent () in the mixed solution is 15 to 90
Claim 1 or 12 which is % by weight
The method described in section. 14 The content of solvent () in the mixed solution is 20 to 80
14. The method according to claim 1, 12 or 13, wherein the amount is % by weight. 15. 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. 16. The method according to claim 1 or 15, 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. 17. The method according to claim 1, wherein the temperature of the post-polymerization is 100°C or less. 18. The method according to claim 1 or 17, wherein the temperature of the post-polymerization is 0 to 80°C. 19. The method according to claim 1, 17 or 18, wherein the post-polymerization temperature is 20 to 60°C.