JPS6322211B2 - - 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, a cyclic formal, an inert organic solvent of 0.1 to 20 parts by weight per 100 parts by weight of formaldehyde, and a formaldehyde copolymer recycled from the second step described below are continuously supplied to a twin-screw mixer, A first step of copolymerizing the formaldehyde and cyclic formal in the presence of boron oxide and continuously discharging the formaldehyde copolymer; , is provided through the side wall, a stirring blade is attached to the outermost periphery of the cooling member, and the bottom wall of the reactor is constituted by a partial cylinder along the locus of the tip of the stirring blade, A horizontal cooler with an arcuate upper wall has a first
This is a method for producing a formaldehyde copolymer, which comprises a second step in which the formaldehyde copolymer from the 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 outer case 2 and two horizontal stirring shafts 4, 5 to which are attached a number of elliptical mixing and stirring blades 3. As shown in FIG. 2, the stirring shaft 4,
When the mixing and stirring blades 5 are rotated, a small gap, usually 0.5 to 5 mm, is formed between the mixing and agitating blades 3 and the surfaces of each other and the inner wall of the outer case 2. Such a twin-screw mixer 1 is commercially available from Kurimoto Iron Works Co., Ltd. as a KRC kneader, for example.

Formaldehyde, cyclic formal, an inert organic solvent and boron trifluoride were added to tube 30, respectively.
31, 32 and 33. Formaldehyde copolymer (hereinafter simply referred to as "copolymer") from the second step is fed through tube 34.

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 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, epipromohydrin, butene-1-oxide, 1,3-butidiene-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 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 hexane,
Examples include aliphatic hydrocarbons such as heptane, alicyclic hydrocarbons such as cyclohexane and cyclopentane, aromatic hydrocarbons such as benzene, toluene and xylene, and halides 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 0.1 to 20 parts by weight, preferably 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 the amount used is larger than the upper limit, the stability of the resulting copolymer in a basic medium will not be further increased, and the cost of recovering the inert organic solvent will increase.

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. As metal chelate compounds, for example, Japanese Patent Publication No. 40-7073, Japanese Patent Publication No. 42-958,
No. 42-7629, No. 42-22068, No. 42-
The chelate compounds mentioned 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 34 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 a two-shaft mixer 1 in which stirring shafts 4, 5 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 to 2000 h ^-1 and the average residence time of the copolymer is usually 5 to 30 seconds.

The product copolymer is discharged through tube 35 together with the circulating copolymer.

Second Step A jacket 12 is attached to the cooler 11 to allow a cooling medium to flow therethrough. Two rotating shafts 13 and 14 are provided passing through both side walls of the cooler 11. It is preferable that the rotating shafts 13 and 14 are provided parallel to each other. The interval between the rotating shafts 13 and 14 is determined by the locus (rotation circle) of the tip of the stirring blade 15, which will be described later.
It is preferable that the two are close to each other or overlap each other. Note that three or more rotating shafts may be provided, but since there is no significant difference in mixing performance, two shafts are practically sufficient.

The rotating shafts 13 and 14 are provided with a disk-shaped cooling member 16,
17 is attached. The interiors of the rotating shafts 13, 14 and the cooling members 16, 17 are structured so that a cooling medium flows therethrough, as shown in FIG. 4, for example. A cooling medium is supplied to one end of the rotating shafts 13, 14 and the cooling members 16, 17.
A rotary joint 18 is attached for supplying and discharging water. The size and number of cooling members 16 and 17 can be appropriately determined by those skilled in the art, taking into consideration the amount of polymerization heat to be removed.

Stirring blades 15 are attached to the outermost peripheries of the cooling members 16 and 17. Although there is no particular restriction on the shape of the stirring blades 15, it is preferable that the flat stirring blades be parallel to the rotating shafts 13 and 14 in order to form a circulating flow of the powdery copolymer within the cooler 11. However, for the purpose of promoting movement of the particulate copolymer in the direction of the rotation axis of the cooler 11, the stirring blades 15 may be inclined with respect to the axial direction, or parallel blades and inclined blades may be combined.
A plurality of stirring blades 15 are installed symmetrically, and three or four blades may also be used, but two blades are usually sufficient. The stirring blades 15 are attached so that both blades do not come into contact with each other due to rotation. The width of the stirring blade 15 relative to the rotation radius of the stirring blade 15 is determined by the width as long as a circulating flow of the powdery copolymer is formed, because as this width increases, the radius of the cooling members 16 and 17 decreases, and the heat transfer area decreases. , preferably small.

The bottom wall 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
When the trajectories of the tips of the tips 5 are far apart, it is preferable to provide a chevron-shaped connection part at the lower part of the cooler 11 in the middle part so as to prevent the powder from staying. The gap between the bottom wall of the cooler 11 and the tip of the stirring blade 15 is preferably as small as possible, and is generally 10 mm or less.

The upper wall of the cooler 11 is formed in an arc shape.
In particular, it is preferable that the upper part of the cooler 11 is formed by a partial cylinder whose diameter is the distance between the walls of the reactor along a horizontal line passing through the centers of the rotating shafts 13 and 14.

A weir 19 is provided on one side wall of the cooler 11, and connected to the weir 19, a copolymer extraction nozzle 2 is connected to the weir 19.
0 is set. The copolymer extraction device is not limited to that shown in the drawings; for example, an extraction nozzle penetrating the jacket 12 may be provided at the bottom of the cooler 11.

The length of the cooler 11 in the axial direction is arbitrary, but it is usually 1 to 7 times the diameter of the rotating circle of the stirring blades 15, especially
1.5 to 5 times is appropriate. The cooler 11 is preferably installed horizontally, but for the purpose of promoting axial movement of the particulate copolymer, it can also be installed at an angle of no more than 10° from the horizontal.

The copolymer from the first step is fed through tube 35. The rotating shafts 13 and 14 are rotated at a constant speed by a drive device (not shown). Rotating shafts 13, 14
The rotating direction of the rotating shaft 13 may be arbitrary, but from the viewpoint of uniformity of stirring, it is preferable to rotate both shafts in opposite directions. In FIG.
It is particularly preferred to rotate the rotating shaft 14 counterclockwise. The rotational speed of the rotating shafts 13 and 14 is preferably 1 to 5 m/sec as the tip speed of the stirring blade 15.

The amount of granular 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 particulate copolymer is stirred up by the stirring blades 15 to form a forced circulation flow.

The heat of polymerization is generated by the refrigerant flowing in the jacket 12,
From the rotary joint 18 to the cooling member 16,1
It is removed by the refrigerant supplied to 7. In the present invention, the powder and granular copolymer violently collides with the entire cooling members 16 and 17, and the heat transfer surface itself rotates, so that the sliding force of the powder increases, and moreover, the heat transfer surface is uniformly fluidized. come into contact with. Therefore, there is little adhesion of the powdery copolymer to the heat transfer surface, the heat transfer surface can be easily renewed, the heat transfer coefficient can be increased by disturbing the boundary surface, and the heat of polymerization can be efficiently removed.

The cooled particulate copolymer is discharged through tube 34. An amount of copolymer commensurate with the product copolymer is withdrawn as product from tube 36, and the remaining copolymer is returned to the first step through tube 34.

In the present invention, the transfer tube 3 for powdery copolymer
Preferably, forced transfer pipes such as screw conveyors are used as 4, 35 and 36.

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.
Using KRC kneader #4, the first
It has the shape shown in Figures 3 and 4, and has a height of 435 mm, a width of 560 mm, a length of 1150 mm, and an internal volume of 200 mm.
A cooler made of SUS304 was used. The cooler is equipped with the cooling member shown in Figure 4 (outer diameter 200mm, made of SUS304).
Two rotating shafts, each with 10 pieces attached at a spacing of 95 mm, are installed in parallel. Two stirring blades are attached to the outer periphery of each cooling member at opposing positions. 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 (hereinafter referred to as FA) was prepared using the above equipment.
) and 1,3,6-trioxocane (hereinafter referred to as
The copolymerization reaction with TOC was carried out continuously.

Approximately 50 kg of a copolymer of FA and TOC was placed in the device and circulated at a rate of 600 kg/h. Moisture content 50
~80ppm gaseous FA at 6Kg/h, gaseous TOC
480 g/h, toluene at 142 g/h, and gaseous boron trifluoride at 18 mmole/h were each fed from an inlet provided downstream of the hopper.
The amount of cooling water entering the cooler jacket and cooling member was adjusted to maintain the copolymer kneader exit temperature at 60°C. The resulting copolymer was withdrawn from the hopper overflow line and contacted with gaseous ammonia to deactivate the boron trifluoride. This continuous copolymerization reaction was carried out for 240 hours.

The resulting copolymer has an intrinsic viscosity of 1.6, a base stability of 90%, a one-pass FA yield of 99%, and a TOC content of
It 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 resulting copolymer has an intrinsic viscosity of 1.7, a base stability of 92%, a one-pass FA yield of 99%, and a TOC content of
It was 2.0 mole%.

Comparative Example 1 Example 1 was repeated except that no toluene was fed.

The resulting copolymer had an intrinsic viscosity of 1.7, a base stability of 81%, and a one-pass FA yield of 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, 13, 14 ... Rotating shaft, 15 ... Stirring blade, 16, 17 ... Cooling member, 19 ... Weir.

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 rotating shafts with disk-shaped cooling members through which a cooling medium flows are installed through the side wall, and a stirring blade is attached to the outermost periphery of the cooling member. The horizontal cooler has a bottom wall formed by a partial cylinder along the locus of the tip of the stirring blade, and a top wall formed in an arc shape.
A method for producing a formaldehyde copolymer comprising a second step of continuously supplying and cooling the formaldehyde copolymer from the step, extracting the copolymer corresponding to the amount produced, and returning the remainder to the first step.