JPH0148820B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for separating and recovering a heteropolyacid contained in a polymer having a polyoxytetramethylene group or a mixture of the same and an organic solvent. . (Prior Art) Generally, in order to remove the acid catalyst in a polymer, extraction with water or addition of a basic substance to generate a salt is filtered or washed. (Problem to be solved by the invention) However, there is a strong interaction between a polymer having a polyoxytetramethylene group in its molecule (hereinafter abbreviated as polyether) and a heteropolyacid; It cannot be removed efficiently by extraction using a method, and a large amount of water is required. Furthermore, water and the polyether tend to form emulsions, making phase separation difficult. Furthermore, if the neutralization reaction is carried out, the expensive heteropolyacid cannot be reused as an acid catalyst, which has the disadvantage of increasing the cost of producing the polymer. (Means for Solving the Problems) Under such circumstances, the present inventors have made extensive efforts to find a method for efficiently removing and recovering the heteropolyacid in the polyether without performing a neutralization reaction in a reusable form. As a result of research, we discovered that when a specific solvent is added to the polyether in which heteropolyacid is dissolved, heteropolyacid precipitates.
The present invention has been accomplished. That is, the present invention is a method for separating and recovering a heteropolyacid contained in a polymer having a polyoxytetramethylene group in the molecule or a mixture of the polymer and an organic solvent, which The gist is to add a single solvent or a mixture of two or more solvents selected from halogenated hydrocarbons having 1 to 15 carbon atoms, and to precipitate and separate a heteropolyacid or a phase mainly composed of a heteropolyacid. The subject of the invention is a polyoxytetramethylene group -(O-CH ₂ -CH ₂ -CH _{2 )} containing a heteropolyacid.
-CH ₂ -) _o (where n is an integer of 2 or more) in the molecule, or a mixture of this and an organic solvent. As a polymer having a polyoxytetramethylene group in the molecule, tetrahydrofuran (hereinafter referred to as
Examples include polymers of THF), copolymers of THF and other cyclic ethers, and copolymers of THF and polyhydric alcohols. The organic solvent mixed with the polyether is not particularly limited, but examples include cyclic ethers that are constituent monomers of the polyether, polyhydric alcohols, alcohols commonly used as polymerization terminators, and the like. A reaction solution of a polymer obtained by polymerizing THF alone or THF and a cyclic ether or polyhydric alcohol using a heteropolyacid as a polymerization catalyst is a suitable example of application, and the fact that the above polymerization is possible is patented by the present inventors. Applications [Japanese Patent Application No. 58-89081 (Japanese Patent Publication No. 63-30931), Japanese Patent Application No. 58-95036 (Japanese Patent Publication No. 63-30932), Japanese Patent Application No. 59-58485 (Japanese Patent Publication No. 60-203633) 〕It is described in. The reaction solution for the above polymerization method is
In many cases, there is a two-phase separation into a phase consisting mainly of the polymer and unreacted monomer and a phase consisting mainly of the catalyst.
In this case, this process may be applied to a reaction liquid from which the catalyst phase has been separated in advance. When a large amount of unreacted monomer coexists, a large amount of solvent is required to precipitate the heteropolyacid. Therefore, at least a portion of the unreacted monomer is recovered from the reaction solution, and the amount of unreacted monomer is preferably 90% by weight or less, more preferably 50% by weight.
After concentration, it is preferable to add an agent that precipitates the heteropolyacid. The crude polyether obtained by simply recovering unreacted monomers from the reaction solution usually contains several weight percent to several tens of weight percent of heteropolyacid. The heteropolyacid in the present invention is a condensation of at least one oxide of Mo, W, and V with an oxyacid of other elements such as P, Si, As, Ge, B, Ti, Ce, and Co. The atomic ratio of the former to the latter is 2.5 to 12. Specific examples of these heteropolyacids include phosphomolybdic acid, phosphotungstic acid, phosphomolybdotungstic acid, phosphomolybdovanadate, phosphomolybdotungstovanadate, phosphotungstovanadate, vanadic acid, phosphomolybdoniobic acid, Silicotungstic acid, silicomolybdic acid, silicomolybdotungstic acid, silicomolybdotungstovanadate, germanium tungstic acid,
Boron tungstic acid, boromolybdic acid, boromolybdotungstic acid, boromolybdovanadate, boromolybdotungstovanadate, cobalt molybdic acid, cobalt tungstic acid, arsenic molybdic acid, arsenic tungstic acid, titanium molybdate, cerium molybdate etc. It also includes these metal salts. 3 carbon atoms used to precipitate heteropolyacid
Examples of ~15 hydrocarbons or halogenated hydrocarbons having 1 to 15 carbon atoms include cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, methylcyclopentane, methylcyclohexane, chlorocyclohexane, propane, butane, Pentane, hexane, hexane, heptane, octane, nonane, decane,
Examples include undecane, dodecane, chloroform, trichlorotrifluoroethane, trichlorofluoromethane, benzene, toluene, chlorunzene, and the like. Propane, butane, etc. must be handled under pressure, which complicates operations. Pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, cyclohexane,
Among the above-mentioned solvents, cyclopentane, cyclooctane, cyclononane, and cyclodecane are particularly preferred because they have a high ability to cause precipitation in heteropolyacids and are effective even in small amounts. Furthermore, in order to separate and recover unreacted THF from a hydrocarbon solvent, it is preferable that the solvent has a higher boiling point than THF and does not form an azeotrope. It is known that n-hexane forms an azeotrope with THF, but it was recently discovered that n-heptane, octane, and nonane do not form an azeotrope. The most preferred solvents are n-heptane, octane, and nonane because they can be recovered relatively easily. Solvents with carbon atoms of 16 or more have high boiling points and are not preferred because of separation and recovery from polyether. Although the details of the function to precipitate heteropolyacid are unknown, it is presumed that low solubility in heteropolyacid and appropriate compatibility with the polyether are contributing factors. The amount of the solvent used to precipitate the heteropolyacid varies depending on the amount of unreacted monomer present, and is usually equal to or more than the weight of the unreacted monomer, preferably more than twice the weight of the unreacted monomer. When the content of unreacted monomers is small, the solvent may undergo phase separation from the polyether phase, but in this case, even if the solvent is used in an amount greater than the amount dissolved, there is little effect. For mixing the solvents, a conventional stirring device, static mixer, or the like is used. By allowing the mixture to stand after mixing, a heteropolyacid or a phase mainly composed of a heteropolyacid precipitates, forming two phases with the polymer solution phase. The lower phase, which is mainly composed of heteropolyacids, contains a small amount of polymer, an unreacted monomer such as THF, and a very small amount of hydrocarbon solvent, although this varies somewhat depending on the operating conditions. The temperature at which the mixture is mixed and allowed to stand is selected to be within a temperature range that does not solidify the polymer and is easy to operate. Because higher temperatures increase the solubility of heteropolyacids, there is no need to use higher temperatures than necessary; typically 25
Performed in the range ~60°C. The standing time is 0.1
It is about 100 hours. The standing time can be shortened by using a coalescer, liquid cycle, centrifuge, etc. The catalyst can also be separated by passing through a membrane filter. Once phase separation is completed, a lower phase and an upper phase containing a high concentration of heteropolyacid are separated. By removing unreacted monomers and added solvent from the upper phase by a method such as distillation, a polymer with a reduced concentration of heteropolyacid can be obtained. The lower phase can be reused as it is as a polymerization catalyst. (Effects of the Invention) By implementing the method of the present invention, heteropolyacids can be efficiently removed and recovered in a reusable form, and the concentration of heteropolyacids in polyether can be reduced to 0.5% by weight or less.
Under optimal implementation conditions, it can be reduced to 0.01% by weight or less. (Example) Hereinafter, the present invention will be explained with reference to Examples. Example 1 In a 5.0 vessel equipped with a stirrer and a reflux condenser,
Prepare 2.0Kg of THF with a moisture content of 300ppm and heat it to 150℃.
1.0 kg of phosphotungstic acid (H ₃ PW ₁₂ O ₄₀ ·3H ₂ O) which has been heated in an electric furnace at a temperature of 2 hours and adjusted to have a coordinated water number of 3 is added. At this time,
The reaction system forms two liquid phases: a catalyst liquid phase and a THF phase.
After stirring was continued for 4 hours at a temperature of 60° C., the mixture was allowed to stand at room temperature and the lower catalyst phase was separated. superior
Analysis of the composition of the THF phase revealed that it contained 23% by weight of polyoxytetramethylene glycol (hereinafter referred to as
PTMG). Next, some unreacted THF is recovered by distillation,
820 g of THF solution containing 50% by weight of PTMG was obtained. In this solution, 6% by weight of ringstic acid was dissolved. Add 1.0 n-octane to this solution.
After adding Kg and stirring, the mixture was allowed to stand at 30°C for 30 hours, whereby the catalyst liquid phase precipitated and separated into two phases. The upper phase became colorless and transparent, and the separation was completed. The catalyst phase recovered from the lower phase weighed 91g and contained approximately 50% by weight of phosphotungstic acid, with the remainder being PTMG.
It was THF and a trace amount of n-octane. When this was recycled and used as a THF polymerization catalyst, THF polymerization progressed. THF from upper phase
By removing and n-octane by vacuum distillation, the phosphotungstic acid concentration was reduced to 50 ppm.
Got PTMG. Comparative Example 1 Contains 6% by weight of phosphotungstic acid and 50% by weight of PTMG obtained in the same manner as in Example 1.
When THF was distilled off from the THF solution by vacuum distillation, no precipitation of the catalyst phase occurred, and all the phosphotungstic acid present was dissolved in PTMG, which contained 12% by weight of phosphotungstic acid.
Got PTMG. Examples 2 to 3 After adding various solvents listed in Table 1 to a polymer listed in Table 1 containing a heteropolyacid obtained using a heteropolyacid as a polymerization catalyst, and a liquid consisting of the polymer and THF and stirring, It was left standing at 30°C for 50 hours. After phase separation and recovery of the precipitated catalyst phase, the upper phase was subjected to solvent enrichment to obtain a polymer with a reduced heteropolyacid concentration. The results are shown in Table 1. In addition, Example 5
The n-butane addition system was operated under liquefaction conditions using a pressurized vessel. Also, in Example 6
PTMG containing about 1.0% by weight of water was used. 【table】

Claims (1)

[Scope of Claims] 1. When separating a heteropolyacid contained in a polymer having a polyoxytetramethylene group in its molecule or a mixture of this and an organic solvent,
Adding a single solvent or a mixture of two or more solvents selected from ~15 hydrocarbons or halogenated hydrocarbons having 1 to 15 carbon atoms to precipitate and separate a heteropolyacid or a phase mainly composed of a heteropolyacid. A method for separating and recovering heteropolyacids. 2. A reaction solution of a polymer in which a polymer having a polyoxytetramethylene group in the molecule or a mixture thereof with an organic solvent is obtained by polymerizing tetrahydrofuran alone or tetrahydrofuran and a cyclic ether and/or polyhydric alcohol using a heteropolyacid as a polymerization catalyst. , or when the reaction liquid consists of two phases including a catalyst phase, the patent is a reaction liquid obtained by separating the catalyst phase, or by recovering and concentrating at least a portion of unreacted monomers from the reaction liquid. The method according to claim 1.