JP2952834B2 - Method for producing polyoxymethylene - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for producing polyoxymethylene which is widely used as an engineering plastic for electric parts, automobile parts, machine parts, and the like, and a method for producing polyoxymethylene using the apparatus. Things. More particularly, the present invention relates to an improved method for continuously and efficiently producing powdery polyoxymethylene using trioxane or a mixture of a compound capable of reacting with trioxane and trioxane as a main starting material. .

BACKGROUND ART Conventionally, polyoxymethylene has undergone bulk polymerization of trioxane alone in the presence of a cationically active catalyst, or trioxane and ethylene oxide, or trioxane and a cyclic formal such as dioxolan or trioxepane in bulk. It was produced by a method of polymerizing.

As a conventional polyoxymethylene production system, JP-
A twin-screw self-cleaning type device as disclosed in A-51-84890 has become mainstream. In this twin-screw self-cleaning type reactor, the outlet of the reactant hit the lower part of the reactor, so that the polyoxymethylene as the target substance was recovered downward. However, this apparatus has a problem that the conversion rate is low because the residence time of the reactants is short. Therefore, many methods have been proposed for increasing the residence time and increasing the conversion rate.

For example, JP-A-56-59824 discloses that the feed rate of a reaction solution is adjusted by shifting the angle of two adjacent paddles provided on one rotating shaft of a reaction apparatus to each other, and a filling rate is set. To increase the residence time by raising the pressure, JP-A
-61-238812, the whole device on the discharge port side is 1 to 1 from the horizontal.
A method has been proposed in which the residence time is lengthened by tilting upward by 10 mm.

However, in the method of increasing the residence time by shifting the paddle angle as described above, when the filling rate is too high, the torque required for stirring rapidly increases and exceeds the durability limit of the apparatus (torque). Out), so operation cannot be continued. In addition, the method of tilting the entire apparatus as described above is a good method that can achieve both high conversion and stable operation at a high level. However, in order to obtain a sufficient residence time, L / D (L: It is necessary to increase the length of the reactor (D: internal diameter), which increases the size of the equipment, which is not preferable as a reactor for industrial use.

An object of the present invention is to provide a method for producing polyoxymethylene, which increases the residence time of a reactant in a reactor and increases the conversion of trioxane.

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above object can be achieved by devising the shape of a discharge port which is a discharge means of a reactant. Was completed.

That is, the present invention provides (1) a plurality of paddles, each of which is provided with a plurality of paddles, and rotates in the same direction, two rotation shafts which are parallel to each other for stirring the reactants, and A twin-body cylindrical case having an inner wall surface along which the two rotating shafts are housed and having a heating / cooling jacket, and (3) reacting with trioxane or trioxane provided at one end of the case. Raw material supply means for introducing a mixture of the compound and trioxane which can be obtained, and (4) for continuously recovering the produced powdery polyoxymethylene provided at the end of the case opposite to the raw material supply means The mixing of trioxane and trioxane or a compound capable of reacting with trioxane, using the above-described reactor, wherein the discharging means is an outlet having a weir. Was introduced from the raw material supply means, subjected to polymerization by reacting with agitation the reaction is the resulting powdery polyoxymethylene process for producing a continuously consists recovering polyoxymethylene.

The reactor according to the present invention includes a twin-cylinder cylindrical case having a jacket capable of heating and cooling, and two parallel rotations having paddles are provided along the central axes of the two cylinders of the case. Each axis is installed. Each of these two rotating shafts has a large number of paddles and rotates in the same direction. Thus, the rotating shaft can react while stirring the reactants in each of the opposing paddle surfaces and the narrow gap formed between the paddle surface and the inner wall surface of the case. This reactor has, at one end, a raw material supply means for introducing trioxane as a raw material or a mixture of a compound capable of reacting with trioxane and trioxane, and the other end has a powdery polyoxymethylene formed therein. Discharging means for recovering the wastewater.

The raw material supply means is preferably a supply port for introducing a raw material.

A preferred discharge means in the present invention is a discharge port having a weir. The outlet is provided substantially tangentially or radially around the circumference of the cross section of the cylinder of the reactor, preferably in the tangential direction of the reactor. A weir is installed at this outlet. Due to the presence of the weir, it takes time for the reactant to be discharged from the reactor, and as a result, the residence time becomes longer, and the conversion of trioxane can be increased.

Therefore, any shape and size may be used as long as the time required for the reactant to be discharged from the reactor is controlled and the residence time of the reactant can be extended. It is included in the concept of weir. Therefore, the weir in the present invention is not limited to the embodiments of the present application or the specific examples disclosed in the drawings.

When the outlet is provided in the tangential direction of the reactor, preferably in the downward tangential direction (hereinafter referred to as the side direction), when the inner diameter of the cylindrical inner wall of the reactor is D, the outlet from the lowest surface of the inner wall is provided. Has a height H of 0.1D to 0.8D, preferably 0.3D to 0.6D. If the height of the weir is less than 0.1D,
Since the effect of increasing the residence time is small, the conversion cannot be increased. If the height of the weir exceeds 0.8D,
Insufficient discharge capacity of the powdery polyoxymethylene causes torque out, so that continuous operation cannot be performed.

On the other hand, when the outlet is provided in the radial direction of the reactor, preferably in the downward radial direction (hereinafter referred to as the lower surface direction), the height H of the weir of the outlet from the lowest surface of the inner wall is 0.
It is 1D to 0.4D, preferably 0.2D to 0.3D. The height of the weir is 0.
If it is less than 1D, the conversion cannot be increased because the effect of increasing the residence time is small. The height of the weir is 0.
If it exceeds 4D, the discharge capability of the powdery polyoxymethylene is insufficient, and torque-out occurs, so that continuous operation cannot be performed. Further, when the height of the weir is 0.5D, the weir and the rotating shaft come into contact with each other, so that it is practically impossible to make the height of the weir 0.5D or more. Since the outlet is provided in the lower surface direction of the reactor, it may be necessary to partially remove the paddle at the outlet in order to provide the weir on the inner wall of the cylinder. In this case, the paddle after the outlet is fixed. For this purpose, a space ring 8 or the like can be provided.

In this reactor, the residence time can be adjusted according to the height of the weir irrespective of the paddle feed force.
Also, even when the supply amount of the raw material increases rapidly, the reactants in the apparatus are blocked by the weir, and the level of the liquid rises as a whole, so that the reactants are naturally discharged from the discharge port without difficulty. It has been found that the problems with the reactor can be solved. In the present invention, the weir can be of a jacket type so that heating and cooling can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS Next, the reactor according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a partial cross-sectional side view of one example of the reactor according to the present invention.

FIG. 2 is a cross-sectional view of the reactor of FIG. 1 taken along line BB.

FIG. 3 is a view of a cross section taken along line AA of FIG. 2 as viewed from the direction of the arrow, and shows a cross section of the weir 7 in the reactor in which the discharge port is provided in the side direction of the cylinder. Is what I saw. In FIG. 3, the height H of the weir 7 is 0.5D, where D is the inside diameter of the cylindrical inner wall of the reactor.

FIG. 4 is a cross-sectional view of the weir 7 in the reactor in which the discharge port is provided in the lower surface direction of the cylinder as viewed from the lateral direction of the reactor, and the height of the weir is 0.25D.

BEST MODE FOR CARRYING OUT THE INVENTION In a reactor according to the present invention, a two-body cylindrical case 1 having a hollow body in which two circles having different eccentric diameters overlap each other to form an eight-shaped cross section is provided. Two rotating shafts 2, 2 'are accommodated, and a temperature control jacket 4 divided into one or a plurality is provided outside the body. A plurality of paddles 3, 3 'each having a convex lens-shaped cross-sectional shape are fixed to the two rotating shafts 2, 2', and each of the paddles has both ends thereof opposed to the inner wall surface of the case. It rotates in the same direction and at the same speed so as to scrape the peripheral surface of the paddle. This reactor is a self-cleaning type continuous stirring mixer.

As the shape of the paddle, a paddle having a cross section of a pseudo polygon such as a pseudo triangle may be used in addition to the paddle having a cross section of the convex lens type. Also, the thickness of these paddles is 1/30 to 1/30 of the inner diameter of the cylindrical inner wall of the reactor.
Preferably, it is about 1/2. These paddles are fixed to each of the two rotating shafts.

The gap between the tip surface of the paddle of this device and the inner wall surface of the cylindrical case is not more than 2%, preferably not more than 1% of the long axis of the paddle, and is mounted facing the tip surface of one paddle and the other rotating shaft. The gap with the side surface of the paddle is 5 times or less, and preferably 2 times or less, of the gap with the inner wall surface of the case.

As shown in FIG. 2, the discharge port 6 is provided in the side direction, and the weir 7
The residence time of the reactants is adjusted by changing the height H of the reactants. Assuming that the cylindrical diameter of the reactor is D, the height H of the weir 7 is 0.
It is 1D to 0.8D, preferably 0.3D to 0.6D.

In order to carry out the present invention, first, the rotating shafts 2 and 2 'of the reactor shown in FIG. 2 are rotated at a desired rotation speed. The rotation speed is not particularly limited, but is usually set at 10 to 150 rpm.

Cooling water of 5 to 95 ° C. is passed through the jacket 4 shown in FIG. 1 in order to remove heat of the polymerization reaction. In the case of a plurality of divided jackets, it is possible to pass cooling water having different temperatures through each jacket, and a preferable cooling water temperature is 65 to 95 ° C. in the first half of the reactor and in the second half thereof. 5-40 ° C.

In this way, the two rotating shafts rotate, and a raw material such as trioxane is supplied from the supply port 5 of the reactor shown in FIG. 1 to the reactor in which cooling water at a predetermined temperature is passed through the jacket.

In addition to the liquid trioxane, a comonomer such as ethylene oxide and 1,3-dioxolan, a polymerization catalyst, and a molecular weight modifier such as methylal are supplied to the supply port 5. When the comonomer is ethylene oxide, since ethylene oxide is a gas at normal temperature, it is preferable to supply it by dissolving it in trioxane.

In the bulk polymerization reaction of bulk polymerization of trioxane alone and copolymerization of trioxane and comonomer, the reaction liquid changes from a liquid with good fluidity to a viscous liquid at first, and further polymerization proceeds, and the conversion of trioxane is about 40% or more. Is a reaction to form a lump solid polyoxymethylene. In this reactor, trioxane is a free-flowing or viscous liquid at the initial introduction of the reactor,
As the reaction proceeds, lump-shaped polyoxymethylene is produced, and is simultaneously pulverized by a paddle into powdery polyoxymethylene, which moves toward the outlet 6 of the reactor while further proceeding the polymerization, and is taken out from the outlet 6. It is.

The production method of the present invention is used for homopolymerization or copolymerization of trioxane. When the purpose is to produce a copolymer, trioxane and a comonomer are mixed in such a ratio that a copolymer containing 0.1 to 20 mol% of an oxyalkylene unit having 2 or more carbon atoms in the oxymethylene main chain is obtained. It is preferable to use those obtained as raw materials. Examples of the comonomer include a cyclic ether or cyclic formal such as ethylene oxide, 1,3-dioxolan, 1,4-butanediol formal, and trioxepane.

As the polymerization catalyst, a commonly used cationic polymerization catalyst is used, preferably, boron trifluoride, boron trifluoride hydrate, and boron trifluoride etherate are used, and more preferably, trifluoride is used. Boron fluoride diethyl ether coordination product and boron trifluoride dibutyl ether coordination product are used.

The polymerization reaction temperature ranges from 60 to 130 ° C, preferably from 65 to 115 ° C.

According to the reactor according to the method of the present invention, a powdery oxymethylene polymer can be efficiently and continuously obtained, and continuous operation can be performed for a long time without any trouble.

 Hereinafter, the present invention will be described in more detail by way of examples.

Example 1 (Invention) The reaction apparatus shown in FIG. 1 was used. This device has an inner diameter
128 mm, the L / D (length / diameter) ratio is 8, and a feed screw having a length of 1D is attached to each of two rotating shafts immediately below the raw material supply port 5.

This reactor has paddles 3, 3 'as shown in Fig. 2, and the gap between the long axis end of the paddle and the inner wall of the cylindrical case is 4m.
m or less. Further, the paddles are mounted in such a manner that they are sequentially shifted by 45 ° in the rotation direction of the shaft following the feed screw. The height of the weir at the outlet is 0.5D.

20 kg / h of liquid trioxane, 1, 1,
400 g / hour of 3-dioxolane and 0.02 mmol and 1 mmol of a tributylamine dibutyl ether coordination compound and methylal were supplied as a cyclohexane solution per 1 mol of trioxane. The polymerization temperature was 90 ° C., and the rotation speed of the paddle tip was 3 m / min. A fine particle polymer passing through a 10-mesh sieve containing 15% of unreacted substances was obtained from the discharge port.

No abnormalities were observed during continuous operation for 300 hours.

Example 2 (invention) In the same reactor as in Example 1, only the height H of the weir 7 at the outlet 6 was set to 0.
The operation was started in the same manner as in Example 1 except that the conditions such as the feed amount of the raw material and the polymerization temperature were changed to 3D.

A fine particle polymer passing through a 10-mesh sieve containing 18% of unreacted substances was obtained from the discharge port.

No abnormalities were observed during continuous operation for 300 hours.

Example 3 (invention) In the same reactor as in Example 1, only the height H of the weir 7 at the outlet 6 was set to 0.
The operation was started in the same manner as in Example 1 except that the conditions such as the raw material supply amount and the polymerization temperature were changed to 7D.

From the discharge port, a fine particle polymer passing through a 10-mesh sieve containing 13% of unreacted substances was obtained.

No abnormalities were observed during continuous operation for 300 hours.

Example 4 (Invention) Except that 1,4-butanediol formal was used in place of 1,3-dioxolane of Example 1, the same reactor as in Example 1 was used, using exactly the same feed rate and feed rate as in Example 1. The operation was started under each condition such as the polymerization temperature.

From the discharge port, a fine particle polymer passing through a 10-mesh sieve containing 14% of unreacted substances was obtained.

No abnormalities were observed during continuous operation for 300 hours.

Example 5 (invention) The same reactor as in Example 1 except that the direction of the discharge port 6 was set to the lower surface direction of the reactor and the height H of the weir 7 was set to 0.25D as shown in FIG. The operation was started in the same manner as in Example 1 for each condition such as the polymerization temperature.

From the outlet, a fine particle polymer passing through a 10-mesh sieve containing 19% of unreacted substances was obtained.

No abnormalities were observed during continuous operation for 300 hours.

Example 6 (Comparative) The operation was started in the same reactor as in Example 1 except that a weir was not provided at the discharge port, and the conditions such as the raw material supply amount and the polymerization temperature were the same as in Example 1.

A fine particle polymer passing through a 10-mesh sieve containing 29% of unreacted substances was obtained from the discharge port.

Example 7 (Comparative) In the same reactor as in Example 1, the reactor was tilted at an angle of 5 ° so that the outlet side was higher, and the conditions such as the amount of raw material supplied and the polymerization temperature were operated in the same manner as Example 1. Started.

After 1 hour, a fine particle polymer passing through a 10-mesh sieve containing 28% of unreacted material was obtained from the discharge port.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C08G 2/00-2/38

Claims (3)

(57) [Claims] 1. A plurality of paddles, each having a plurality of paddles, and rotating in the same direction, two rotating shafts parallel to each other for stirring a reactant, and (2) along a rotating circumferential surface of each paddle. A twin-cylinder cylindrical case having an inner wall surface, housing the two rotation shafts, and having a heating and cooling jacket,
(3) a material supply means provided at one end of the case for introducing trioxane or a mixture of trioxane and a compound capable of reacting with trioxane; and (4) a material supply means provided at an end of the case opposite to the material supply means. In the reaction apparatus comprising discharge means for continuously recovering the produced powdered polyoxymethylene, the discharge means reacts with trioxane or trioxane by using the above-described reaction apparatus which is a discharge port having a weir. The production of polyoxymethylene by introducing a mixture of a compound capable of being prepared and trioxane from a raw material supply means, reacting the reactants while stirring and subjecting the mixture to polymerization, and continuously recovering the resulting powdery polyoxymethylene. Method. 2. The method according to claim 1, wherein the outlet of the reactor is provided tangentially on a side surface of the cylinder of the reactor. (3) Assuming that the inner diameter of the cylindrical inner wall of the reactor is D,
3. The method according to claim 2, wherein the height of the weir at the outlet from the lowest surface of the inner wall is in the range of 0.1D to 0.8D.