JPS6231726B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing oxymethylene copolymers. More specifically, the present invention relates to a method for producing an oxymethylene copolymer having a large particle size. A method is known in which formaldehyde and a cyclic ether are slurry copolymerized in an inert organic solvent in the presence of a reaction mixture of a metal chelate compound and a Lewis acid (Japanese Patent Publication No. 3558/1983). In this method, in order to allow the copolymerization reaction to proceed smoothly, the concentration of thriller in the polymerization system must be at most 15% by weight. That is, it is necessary to use an overwhelmingly large amount of an inert organic solvent as a reaction solvent relative to the produced oxymethylene copolymer. When carrying out this method industrially, the reaction solvent obtained by separating the produced oxymethylene copolymer from the copolymerization reaction mixture is purified by distillation and recycled to the copolymerization reaction system for use. However, this refining consumes a large amount of energy. Further, in this method, it is necessary to react the polyvalent metal chelate compound and the Lewis acid in advance before adding them to the copolymerization reaction system. A method for obtaining an oxymethylene copolymer by subjecting formaldehyde and a cyclic ether to a gas phase reaction in the presence of a Lewis acid is also known (Japanese Patent Publication No. 1973-
Publication No. 7554). Since this method does not use a reaction solvent, there is no need to purify the reaction solvent as in the above method, and it is advantageous in terms of energy. Incidentally, most of the oxymethylene copolymers obtained by this method are powders having a particle size of less than 125 μm. This is explained in ``Tokukoku No. 7554, page 4, right column, lines 14 to 17''.
When the BF ₃ is started, a white vapor resembling cigarette smoke immediately forms in the reaction zone, indicating the formation of polymer in the dispersed phase. This is also supported by the statement. These fine powders have a strong adhesive force (see Powder Engineering Handbook, published by Asakura Shoten, page 132), and adhere to the inner walls of the copolymerization reactor and the stirrer, making it difficult to remove the heat of the copolymerization reaction. In addition, it becomes impossible to smoothly discharge the powder from the copolymerization reactor and to transfer the powder thereafter. An object of the present invention is to provide a method for producing an oxymethylene copolymer having a large particle size. Another object of the present invention is to provide a method for producing oxymethylene copolymers with low energy consumption. These objects of the present invention are directed to the preparation of formaldehyde and a cyclic ether in the presence of an oxymethylene polymer free of inert organic solvents or containing up to 50% by weight thereof, and from a metal chelate compound and a Lewis acid. This is achieved by copolymerizing in the gas phase in the presence of a catalyst in which the molar ratio of the metal chelate compound to the Lewis acid is 5 x 10 ^-4 or more. According to the present invention, since an oxymethylene copolymer having a particle size of mostly 125 μm or more is obtained, there is less adhesion of the copolymer to the inner wall of the copolymerization reactor and the stirring device, and there is less adhesion of the copolymer to the inner wall of the copolymerization reactor and the stirring device. Discharge of the copolymer and subsequent transfer of the copolymer can be performed smoothly. Furthermore, in the present invention,
Since no inert organic solvent is used, or only a small amount is used, the energy required for separation and purification of the inert organic solvent is extremely small. The water content of formaldehyde used in the present invention is preferably 0.1% by weight or less, particularly 0.01% by weight or less. As a cyclic ether, the formula Compounds represented by and formula A compound represented by (in both the above formulas, R ¹ ,
R ² , R ³ and R ₄ each represent hydrogen, an alkyl group, an allyl group and a cycloalkyl group, and m
represents an integer of 1 to 3, and n represents an integer of 2 to 6. ) is used. Specific examples include ethylene oxide, propylene oxide, epichlorohydrin, epibromohydrin, butene-1-oxide, 1,3-butadiene-1-oxide, styrene oxide, a-methylstyrene oxide, oxetane, tetrahydrofuran, 1,3 ―
Dioxolane, 4-phenyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, 2-
Phenyl-1,3-dioxolane, 1,3-dioxopane, 2-butyl-1,3-dioxopane,
Examples include 1,3,6-trioxocane, 1,3,5-trioxopane, and polyethylene glycol formal. The amount of cyclic ether used is preferably 0.001 to 0.1 mol, particularly 0.01 to 0.04 mol, per mol of formaldehyde. Examples of metal chelate compounds include, for example, Japanese Patent Publications No. 40-7073, No. 42-958, and No. 42-
The chelate compounds described in JP 7629, JP 42-22068, JP 42-19340, and JP 49-35839 are used. Typically, Cu, CO, Fe,
Examples include chelate compounds having a metal such as Ni or V as a central atom and a ligand such as β-diketones, aromatic oxyaldehydes, or condensates of aromatic oxyaldehydes and diamines. As the Lewis acid, the Lewis acid described in Japanese Patent Publication No. 1983-3558 is used, among which boron trifluoride, boron trifluoride,
Also, complexes of boron trifluoride and ethers such as dimethyl ether and diethyl ether are preferably used. The amount of Lewis acid used is usually 1.0 x 10 ^-5 to 1.0 x 10 ^-3 mol per 1 mol of formaldehyde. The amount of the metal chelate compound used must be 5 x 10 ^-4 mol or more per mol of Lewis acid,
The amount is preferably 5×10 ^-3 mol or more. If the amount of metal chelate compound used is less than the above lower limit,
The proportion of oxymethylene copolymer with small particle size increases (see Comparative Examples 1 and 2). There is no particular restriction on the upper limit of the amount of metal chelate compound used, but even if the amount is excessively increased, the particle size of the oxymethylene copolymer obtained will not become larger, and it is usually 2.0×10 ^-8 per mole of formaldehyde. ~1.0×
10 ^-5 mol. In the present invention, formaldehyde and a cyclic ether are copolymerized in the presence of an oxymethylene polymer. As the oxymethylene polymer to be present in the copolymerization reaction system, when carrying out the present invention continuously,
It is preferable to use the copolymer itself produced by the copolymerization reaction. An oxymethylene homopolymer may be used at the start of the copolymerization reaction. The amount of oxymethylene polymer present in the copolymerization reaction system is 1
It is preferably 30 parts by weight or more, particularly 50 to 500 parts by weight, per 100 parts by weight of formaldehyde fed per hour. If the amount of oxymethylene polymer present is too small, the formaldehyde copolymerization yield will decrease. The oxymethylene polymer present in the copolymerization reaction system can contain an inert organic solvent in an amount of 50% or less, preferably 10% or less of its weight. When the comonomer cyclic formal is liquid and dissolves the catalyst, the copolymerization reaction can be carried out in the absence of an inert organic solvent. When the cyclic formal is liquid but does not dissolve the catalyst, or when the cyclic formal is gaseous, the catalyst is supplied to the copolymerization reaction system as a solution in an inert organic solvent. In this way, in addition to the inert organic solvent supplied with the catalyst, an inert organic solvent may be added alone to the copolymerization reaction system. In any case, it is necessary that the content of the inert organic solvent in the oxymethylene polymer present in the copolymerization reaction system is 50% by weight or less. When the content of the inert organic solvent exceeds the upper limit, the power required to stir the copolymerization reaction system increases, and at the same time, a large amount of thermal energy is required to purify the inert organic solvent after the copolymerization reaction is completed. The copolymerization reaction temperature is usually 0 to 110°C, preferably
The temperature is 40-100℃. Copolymerization reaction time is usually 20 minutes ~
It is 10 hours. The copolymerization reaction in the present invention can be carried out using various reactors. Examples of reactors include fixed reactors with helical stirring blades, paddle-type stirring blades, or anchor-type stirring blades, rotary reactors with internal baffles or built-in hard iron balls, Examples include a reactor described in JP-A-55-157605 in which a large number of stirring blades are attached to two rotating shafts, respectively. In order to efficiently remove the copolymerization reaction heat, a cooling pipe or a cooling plate for circulating a coolant may be provided inside the reactor, or an external circulation cooling device may be provided. Next, Examples and Comparative Examples will be shown. The intrinsic viscosity of the oxymethylene copolymer was measured at 60°C using p-chlorophenol containing 2% by weight of α-pinene as a solvent. The base stability of an oxymethylene copolymer is defined as the base stability of an oxymethylene copolymer in benzyl alcohol containing 1% by weight of tri-n-butylamine.
This is the recovery rate of the copolymer when heat treated at 160°C for 1 hour at a copolymer concentration of 10% by weight. Example 1 A glass flask with an internal volume of 1 and an intrinsic viscosity of 1.50 was equipped with a catalyst inlet, a comonomer inlet, and a copolymer outlet at the bottom, and was equipped with a stirrer, a thermometer, and a formaldehyde gas injection nozzle.
dl/g and 20 g of oxymethylene copolymer with base stability of 92% was charged. In order to remove moisture in the flask, it was dried under reduced pressure at 60°C for 3 hours. While the copolymer was uniformly suspended in the flask by stirring, the temperature of the contents of the flask was raised to 80°C, and a toluene solution of 1 x 10 ^-6 mol/ml of copper bis(acetylacetone), 1 ×10 ^-4 mol/ml boron trifluoride diethyl ether toluene solution, 1,
3,6-trioxocane and formaldehyde gas at 6 ml/h, 1 ml/h, and 3.4 ml, respectively.
Continuous copolymerization is carried out in which the formaldehyde-TOC random copolymer produced is continuously supplied to the flask at a rate of ml/h and 62 g/h, and the resulting formaldehyde-TOC random copolymer is continuously discharged from the flask at a rate corresponding to the amount of monomer supplied.
It was carried out for 5 hours at ℃. Table 1 shows the yield of the copolymer, the intrinsic viscosity of the copolymer 3 to 5 hours after the start of copolymerization, the base stability, and the particle size distribution. Comparative Example 1 Example 1 was repeated except that the toluene solution of copper bis(acetylacetone) was not fed. The results are shown in Table 1. Example 2 Example 1 was repeated except that a toluene solution of bis(acetylacetone)copper of 1×10 ^-8 mol/ml was fed at a rate of 6 ml/h. The results are shown in Table 1. Comparative Example 2 Example 2 was repeated except that the concentration of copper bis(acetylacetone) in toluene was changed to 1×10 ⁻⁹ mol/ml and the feeding rate was changed to 1 ml/h. The results are shown in Table 1. Example 3 Bis(acetylacetone) copper was dissolved in TOC in advance, and the solution was supplied at a rate of 6×10 ^-6 mol/h and 3.4 ml/h. Example 1 was repeated. The results are shown in Table 1. Example 4 1,3- in place of 1,3,6-trioxocane
Example 1 was repeated, except that dioxolane was fed at a rate of 4.5 ml/h. The results are shown in Table 1. Comparative Example 3 Example 4 was repeated except that the toluene solution of copper bis(acetylacetone) was not provided. The results are shown in Table 1.

Table 1 shows that according to the present invention, in which a metal chelate compound and a Lewis acid are used in a certain ratio, an oxymethylene copolymer having a large particle size can be obtained.

Claims (1)

[Claims] 1. Formaldehyde and the formula Compounds represented by and formula A compound represented by (in both the above formulas, R ¹ ,
R ² , R ³ and R ⁴ each represent hydrogen, an alkyl group, an allyl group and a cycloalkyl group, and m
represents an integer of 1 to 3, and n represents an integer of 2 to 6. ) in the presence of an oxymethylene polymer containing no inert organic solvent or 50% by weight or less thereof, and consisting of a metal chelate compound and a Lewis acid,
A method for producing an oxymethylene copolymer, which comprises copolymerizing in a gas phase in the presence of a catalyst in which the molar ratio of metal chelate compound to Lewis acid is 5 x 10 ^-4 or more.