JPH0257567B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for making formaldehyde copolymers. A method of copolymerizing formaldehyde and cyclic formal in the gas phase in the presence of boron trifluoride is known (see Japanese Patent Publication No. 7554/1983). As can be seen from the results of the examples in the above publication, the copolymers obtained by this method have low molecular weights and low stability in basic media, and cannot be put to practical use. Japanese Patent Publication No. 44-870 discloses a method of copolymerizing formaldehyde and a comonomer in the gas phase in the presence of an amine in a rotating reactor. When this method is carried out industrially, the polymer adheres to the walls of the reactor within a short period of time, making it impossible to operate smoothly. To prevent polymer adhesion to the reactor walls,
It is conceivable to use a self-cleaning twin-screw mixer that has been proposed as a copolymerization reactor for trioxane and cyclic formal. According to experiments conducted by the present inventors, when formaldehyde and cyclic formal are copolymerized using this twin-shaft mixer, the activity of boron trifluoride or its ether complex used as a catalyst is low, and productivity is low. Problems arose such as small size and poor stability of the resulting copolymer in basic media. Further, in the copolymerization of formaldehyde and cyclic formal, a large amount of heat of polymerization is generated, but since the heat transfer area of the twin-screw mixer is small, the heat of polymerization cannot be completely removed. Therefore, it is necessary to adopt an external circulation cooling method in which the copolymer discharged from the twin-screw mixer is cooled by passing it through an external circulation cooler and then returned to the above-mentioned stirrer. When a known cooler such as a stirrer cooler with a cooling jacket is used for this purpose, formaldehyde copolymer adheres to the inner wall of the cooler and the stirrer, reducing the cooling function and increasing the load on the stirring power. A problem arises. The present invention provides a method for all at once solving the above-mentioned problems when copolymerizing formaldehyde and cyclic formal. In the present invention, formaldehyde, cyclic formal, an inert organic solvent of 0.1 to 20 weight parts per 100 parts of formaldehyde, and a formaldehyde copolymer recycled from the second step described below are continuously supplied to a twin-shaft mixer, and trifluorinated A first step of copolymerizing the formaldehyde and cyclic formal in the presence of boron and continuously discharging the formaldehyde copolymer, and a plurality of stirring shafts equipped with stirring blades are provided to penetrate the lower side wall, A cooler in which the bottom wall is made up of a partial cylinder that follows the trajectory of the tip of the stirring blade, and a rotating shaft with a disk-shaped cooling member inside which the cooling medium flows passes through the upper side wall. This method for producing formaldehyde copolymers consists of a second step in which the formaldehyde copolymer from the first step is continuously supplied and cooled, the copolymer corresponding to the amount produced is extracted, and the remainder is returned to the first step. According to the present invention, a formaldehyde copolymer having excellent stability in a basic medium can be obtained in high yield. Furthermore, according to the present invention, adhesion of the copolymer to the cooler is significantly suppressed.
The copolymer can be produced stably over a long period of time. Next, the present invention will be explained based on one embodiment shown in the drawings. 1st step: Twin-shaft mixer 1 used as a polymerization reactor
consists of an external case 2 and two horizontal stirring shafts 4 to which are attached a large number of circular mixing and stirring blades 3. As shown in FIG. 2, when the stirring shaft 4 is rotated, the mixing and stirring blades 3 have a small gap between each other and the inner wall of the outer case 2.
Create a gap of 0.5 to 5 mm. Such a twin-shaft mixer 1 is available from KRC, for example, from Kurimoto Iron Works Co., Ltd.
It is commercially available as Kneader. Formaldehyde, cyclic formal, an inert organic solvent and boron trifluoride were added to tube 20, respectively.
21, 22 and 23. The formaldehyde copolymer (hereinafter simply referred to as "copolymer") from the second step is fed through tube 24. The moisture content of formaldehyde is preferably 0.1% by weight or less, particularly 0.01% by weight or less.
Formaldehyde is subjected to the reaction in a gas phase. As a cyclic formal, the formula

【formula】 A compound represented by, and formula

[Formula] Compound (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, α-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 formal used is 0.001 to 0.1 mol per mol of formaldehyde supplied.
In particular, it is preferably 0.01 to 0.04 mol. When using a cyclic formal that is liquid at room temperature, it is preferable to preheat it to a gaseous state and use it for the reaction. Specific examples of inert organic solvents include pentane,
Examples include aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane and cyclopentane, aromatic hydrocarbons such as benzene, toluene and xylene, and halogenated products of these hydrocarbons. It is preferable that the inert organic solvent is subjected to the reaction in a gaseous state. The amount of inert organic solvent used is
The amount is from 0.1 to 20 parts by weight, preferably from 0.5 to 5 parts by weight, per 100 parts by weight of formaldehyde fed. If the amount used is less than the lower limit, the activity of boron trifluoride or its ether complex used as a catalyst will be greatly reduced, and the resulting copolymer will have low stability in a basic medium. Even if you use more than the upper limit,
The resulting copolymer is not more stable in basic media, and the cost of recovering the inert organic solvent is increased. Boron trifluoride may be used as it is, or may be used as a complex with an ether such as dimethyl ether or diethyl ether. The amount of boron trifluoride used is usually 1 x 10 ^-5 to 1 x 10 ^-3 mol per mol of formaldehyde supplied. When using a boron trifluoride ether complex that is liquid at room temperature, it is preferable to bring it into a gas phase beforehand and use it for the reaction. Boron trifluoride can be used in combination with metal chelate compounds. Examples of metal chelate compounds include, for example, Japanese Patent Publication No. 40-7073, Japanese Patent Publication No. 42-958,
Publication No. 42-7629, Publication No. 42-22068, Publication No. 42-
The chelate compounds described in JP 19340 and JP 49-35839 are used. Typically, Cu, Co,
Examples include chelate compounds having a metal such as Fe, Ni, or V as a central atom and a ligand such as β-diketones, aromatic oxyaldehydes, or condensates of aromatic oxyaldehydes and diamines. The amount of metal chelate compound used is preferably 0.5 mol or less, particularly 0.05 to 0.5 mol, per 1 mol of boron trifluoride. By using a metal chelate compound in combination, the stability of the produced copolymer in a basic medium is further improved. The metal chelate compound is dissolved in an inert organic solvent or liquid cyclic formal and subjected to the reaction. The amount of copolymer circulated through tube 24 is
It varies depending on the polymerization heat to be removed in the second step, but usually 50 to 50% of the formaldehyde weight supplied is
200 times more. A copolymerization reaction between formaldehyde and cyclic formal is carried out in the twin-screw mixer 1 in which a stirring shaft 4 and stirring blades 3 are driven by a motor (not shown). Polymerization temperature is usually 40-80°C. The space velocity of formaldehyde in stirrer 1 is usually 300
˜2000 h ⁻¹ and the average residence time of the copolymer is typically 5 to 30 seconds. The produced copolymer is discharged through tube 25 together with the circulating copolymer. Second Step Two stirring shafts 12 are provided in the lower part of the cooler 11, penetrating the side wall 13 of the cooler in parallel. The distance between the two stirring shafts 12 is determined by the support 1 on the shaft.
It is preferable that the trajectories (circles of rotation) of the tips of the stirring blades 15 provided through the stirring blades 4 touch or overlap. Three or more stirring shafts may be provided, but since there is no significant difference in mixing performance, two stirring shafts are practically sufficient. Although there are no particular restrictions on the shape of the stirring blades 15, paddle blades are generally used to scrape up the powdered copolymer in the cooler 11. In order to scrape up the powdered copolymer, it is preferable to place the paddle blades parallel to the stirring shaft 12, but in order to create a gentle circulation flow throughout the cooler 11, the paddle blades may be tilted or horizontal blades may be used. It is also possible to combine the blade with an inclined blade. A plurality of stirring blades 15 are mounted symmetrically on the stirring shaft. Three or four blades may also be used, but two blades spaced 180 degrees apart is usually sufficient. The spacing between the stirring blades 15 in the axial direction is also arbitrary, but from the point of view of the stirring effect, it is preferable that they be close to each other, and they are usually installed at intervals of 1.1 to 3 times the width of the blades. The relative position of the stirring blades 15 between the two shafts is such that both blades do not come into contact with each other due to rotation. The bottom of the cooler 11 is formed of a partial cylinder along the trajectory of the tip of the stirring blade 15. The limit for partial cylinders is up to 1/2 cylinder. That is, stirring blade 1
If the trajectories of the tips of the copolymer 5 are far apart, a chevron-shaped connection part is provided at the bottom of the cooler 11 in the middle part thereof to prevent the copolymer from stagnation. Cooler 11
The smaller the gap between the bottom of the stirring blade 15 and the tip of the stirring blade 15, the better, and is generally 10 mm or less. The height of the cooler 11 is desirably greater than the height of the powdered copolymer that has been stirred and floated, and is therefore 1.2 times or more, preferably 1.5 to 3.5 times the diameter of the maximum rotation circle drawn by the stirring blades 15. The length of the cooler 11 in the axial direction is arbitrary, but it is usually 1 to 7 times, particularly 1.5 to 5 times, the diameter of the rotating circle. At the top of the cooler 11, a disk-shaped cooling member 16 is provided.
A rotating shaft 17 with a rotary shaft attached thereto is provided to penetrate through the side wall 13. The rotating shaft 17 is installed parallel to the stirring shaft 12. Further, the rotating shaft 17 is provided so that the lower end of the cooling member 16 attached thereto is near the highest point of the trajectory of the stirring blade 15. The size, number, etc. of the cooling member 16 can be easily determined by those skilled in the art, taking into consideration the amount of heat to be removed. The interiors of the cooling member 16 and the rotating shaft 17 have a structure through which a cooling medium flows, as shown in FIG. 4, for example. A rotary joint 18 is attached to one end of the rotating shaft 17, and the cooling medium is supplied to the cooling member 16 and is discharged through the rotating shaft 17 after exchanging heat. The powdered copolymer from the first step is fed through tube 25. The stirring shaft 12 is driven by a drive device (not shown). The rotational speed of the stirring blades 15 is determined in consideration of the size of the cooler 11, the size and number of blades, etc. In order to obtain a sufficient stirring effect, the height of the powdered copolymer in the cooler 11 is generally set so that the height above the upper end of the stirring blade 15 is approximately 0.5 to 2 times the rotational diameter of the stirring blade 15. The rotation speed is adopted. This generally corresponds to a linear velocity of 1 to 5 m/sec at the tip of the stirring blade 15. The amount of powdered copolymer in the cooler 11 may be any amount as long as a sufficient stirring effect can be obtained, but the amount below the position near the highest point drawn by the stirring blade 15 when the stirring blade 15 is stopped is sufficient. It is preferable that there be. Inside the cooler 11, the powdered copolymer is stirred up by the stirring blades 15 to form a forced circulation flow. The upper surface of this forced circulation flow is connected to the cooling member 16
It is preferable for the polymerization temperature to be located above the highest point in order to efficiently remove the heat of polymerization. The rotating shaft 17 is rotated by a drive device (not shown). The rotational speed of the rotating shaft 17 is set to 0.3 as the linear velocity of the tip of the cooling member 16 in order to increase the apparent collision speed between the powdered copolymer and the cooling member 16.
It is preferable that it is 3 m/sec. The polymerization heat is transferred to the wall of the cooler 11 and the cooling member 1.
removed by 6. In particular, in the present invention, the cooling member 16 is installed in the forced circulation flow generated by the intense scraping or splashing effect of the stirring blades 15.
The powdered copolymer violently collides with the entire surface of the heat transfer surface 6, and the heat transfer surface itself rotates, thereby increasing the sliding force of the powder and bringing the heat transfer surface into uniform contact with the fluid. Therefore, there is less adhesion of the powdered copolymer to the heat transfer surface, the heat transfer surface can be updated easily, and the heat transfer coefficient can be increased by disturbing the boundary surface.
Polymerization heat can be efficiently removed. The cooled powdered copolymer is discharged through tube 24. An amount of copolymer commensurate with the product copolymer is withdrawn as product from tube 26, and the remaining copolymer is returned to the first step through tube 24. In the present invention, the powder copolymer transfer tube 2
Preferably, forced transfer pipes such as screw conveyors are used as 4, 25 and 26. Next, examples will be shown. The intrinsic viscosity of the copolymer is 60% when p-chlorophenol containing 2% by weight of α-pinene is used as a solvent.
Measured at °C. The base stability of a copolymer is defined as the base stability of a copolymer at a concentration of 10% by weight 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. Example 1 A polymerization reactor equipped with a hopper manufactured by Kurimoto Iron Works Co., Ltd.
KRC kneader #4 is used as a cooler, as shown in Figure 1.
It has the shape shown in Figures 3 and 4, and the height
475mm, width 440mm, length 1000mm, internal volume approx. 192.3
A cooler made of SUS304 was used. Inside the cooler, 16 disk-shaped cooling members (outer diameter 200 mm, made of SUS304) are installed in series on two parallel rotating shafts. Each is designed to allow water to flow through it. Temperature-controlled water was passed through it as a coolant. The cooler was also equipped with a jacket for heat removal, which was used to remove reaction heat in the same way as the internal cooler. The length from the tip of one stirring blade to the tip of the other blade 180 degrees apart is 270 mm. Screw conveyors were used for all the tubes connecting the polymerization reactor and the cooler and the tubes for extracting the produced copolymer from the hopper. Formaldehyde (below) using the above equipment
It's called FA. ) and 1,3,6-trioxocane (hereinafter referred to as TOC) were continuously copolymerized. Put about 50 kg of copolymer of FA and TOC into the device,
This was circulated at 600 kg/h. Moisture content is 50~
80ppm gaseous FA at 6Kg/h, gaseous TOC
480 g/h, toluene at 142 g/h, and gaseous boron trifluoride at 18.0 mmole/h were each fed from an inlet provided downstream of the hopper. The amount of cooling water entering the jacket and disc-shaped cooling member of the polymerization reactor and cooler was adjusted so as to maintain the copolymer kneader outlet temperature at 60°C. The resulting copolymer was extracted from the overflow line of the hopper and the boron trifluoride was deactivated with gaseous ammonia. This continuous copolymerization reaction was carried out for 240 hours. The intrinsic viscosity of the resulting copolymer is 1.6, and the base stability is
The FA yield in one pass was 99%. The TOC unit content of the copolymer was 2.0 mole%. Example 2 Example 1 was repeated except that the gaseous TOC feed rate was changed to 390 g/h and liquid TOC in which bis(acetylacetone) copper was dissolved at a concentration of 21.4 μmole/g was newly fed at 90 g/h. . The intrinsic viscosity of the resulting copolymer is 1.7, and the base stability is
The FA yield in one pass was 92% and 99%. The TOC unit content of the copolymer was 2.0 mole%. Comparative Example 1 Example 1 was repeated except that no toluene was fed. The intrinsic viscosity of the resulting copolymer is 1.7, and the base stability is
The yield was 81% and 95%.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are respectively A of FIG.
- A sectional view and a BB line sectional view, and FIG. 4 is an enlarged sectional view of the cooling member. 1...Two-shaft mixing agitator, 3...Mixing stirring blade, 4
... Stirring shaft, 11 ... Cooler, 12 ... Stirring shaft,
15... Stirring blade, 16... Cooling member, 17... Rotating shaft.

Claims (1)

[Claims] 1. Formaldehyde, cyclic formal, 0.1 to 20 parts by weight of an inert organic solvent per 100 parts by weight of formaldehyde, and formaldehyde copolymer recycled from the second step described below are continuously fed to a twin-shaft mixer. , a first step of copolymerizing the formaldehyde and cyclic formal in the presence of boron trifluoride and continuously discharging the formaldehyde copolymer;
A plurality of stirring shafts equipped with stirring blades are installed through the lower side wall, and the bottom wall is composed of a partial cylinder that follows the trajectory of the tips of the stirring blades, and a cooling medium flows inside. The formaldehyde copolymer from the first step is continuously supplied and cooled to a cooler in which a rotary shaft to which a disc-shaped cooling member is attached passes through the upper side wall. A method for producing a formaldehyde copolymer comprising a second step of extracting and returning the remainder to the first step.