JPS5838712A - Continuous process for feeding the starting materials of oxymethylene copolymer - Google Patents

Abstract

PURPOSE:The nozzle for feeding the polymerization catalyst is made of a specific substance and specified feeding conditions are set to permit the continuous and stable feed of the starting materials with no problems of nozzle clogging and formation of colored and deteriorated substances. CONSTITUTION:A flow of starting materials for polymerization composed of (A) trioxane and (B) cyclic ether or cyclic formal, preferably ethylene oxide, is fed from a nozzle 1 and used to wash the top end of the nozzle 2' for the catalyst feed pipe 2, which is made of a fluorine-containing resin such as polytetrafluoroethylene. Thus, the starting materials for polymerization are mixed with (C) the polymerization catalyst, preferably boron trifluoride diethyl etherate, which is fed from the nozzle 2', in the mixing chamber 5 and sent to the copolymerization zone. EFFECT:Good-quality oxymethylene copolymers are stably obtained with industrial advantage.

Description

DETAILED DESCRIPTION OF THE INVENTION In the continuous production of polyacetal polymers, the present invention provides a method for continuously supplying and mixing trioxane, a comonomer copolymerized therewith, and a polymerization catalyst to a polymerization reaction apparatus. The present invention relates to an improvement in the method of supplying.

The method for producing oxymethylene copolymers containing trioxane as a main component has been widely studied, and the most advantageous method in industry at present is to use a continuous polymerization reaction apparatus in which liquid trioxane, a comonomer, and a polymerization catalyst are combined. It is said that this is a method in which a powdery copolymer is continuously obtained from a reaction product outlet.

However, in this conventional technology, which is considered to be industrially advantageous, polymers often form and adhere to the tip of the supply nozzle of the polymerization catalyst that is continuously supplied, making it difficult to continuously supply a predetermined amount. However, there was an industrially serious defect in that smooth continuous production of oxymethylene copolymers was no longer possible. When such an inconvenient phenomenon occurs, it is necessary to quickly take measures such as taking out the tip of the catalyst supply pipe including the nozzle, removing and cleaning the stuck polymer, or installing a spare. Although this procedure is not a very difficult operation, it has a serious effect on continuous polymerization operation in an airtight system. This changes the ratio and adversely affects the molecular weight and polymerization yield of the copolymer produced, which not only poses a major problem in industrial production, but also poses a fatal problem that requires the polymerization operation to be stopped. be.

As a means to eliminate such defects in the continuous production of industrial oxymethylene copolymers, Japanese Patent Application Laid-Open No. 56-161
Publication No. 95 proposes a method in which the tip of a polymerization catalyst supply nozzle and the tip of a comonomer supply nozzle are opened close to each other, and the tips of both nozzles are flushed with a separate injection flow of trioxane. has been done. This method greatly improves the problem of clogging caused by polymer adhesion at the tip of the catalyst supply port, but the supply device is complicated and is not easy to handle, and the catalyst supply nozzle has a brown discoloration. A major problem arises in that the colored substances are mixed into the white copolymer final product and degrade its quality. It is presumed that the production of altered products at the catalyst supply nozzle is caused by a side reaction when a comonomer such as ethylene oxide comes into contact with a high concentration polymerization catalyst. One possible solution to this inconvenient phenomenon is to wash the tip of the polymerization catalyst supply nozzle with a mixed flow of a comonomer dissolved in trioxane; It was confirmed that the particles adhered to each other, causing a blockage phenomenon, and no effect was observed.

The present inventors have conducted intensive studies on methods to overcome the above-mentioned defects in the continuous copolymerization of trioxane and a comonomer, and as a result, we have found that a phenomenon in which a polymer is formed and adheres to the polymerization catalyst supply nozzle. We have discovered an industrially superior supply method that can stably supply each component for polymerization continuously over a long period of time without causing any colored foreign matter.

That is, the present invention provides a method for continuously supplying trioxane and a cyclic ether or a cyclic formal together with a polymerization catalyst to a polymerization reaction apparatus to continuously obtain an oxymethylene copolymer, which includes at least a nozzle portion of a polymerization catalyst supply pipe. The copolymerization reaction zone is formed by mixing the polymerization raw material and the catalyst while washing the tip of the polymerization catalyst supply nozzle with the flow of the mixture introduced from the polymerization raw material mixture supply nozzle. A method for continuously supplying raw materials for polymerization is provided.

Industrially useful oxymethylene copolymers are those in which the oxymethylene units have a molar proportion of 90 or more, particularly 95 or more, and are otherwise composed of oxyalkylene units having at least adjacent carbon atoms. Although the oxymethylene units are provided by trioxane and the other oxyalkylene units by the corresponding cyclic ethers or cyclic formals, in the present invention,
These raw materials for polymerization are mixed in advance and supplied to the copolymerization apparatus from the supply nozzle. Further, a catalyst for copolymerizing these raw materials is simultaneously and continuously introduced into the copolymerization apparatus from a supply nozzle provided in the vicinity of the polymerization raw material supply nozzle, and is continuously mixed and guided to the polymerization zone. The present invention is characterized in that, in such a raw material component supply method, at least the nozzle portion of the polymerization catalyst supply pipe is preferably made of a fluorine-containing resin together with the polymerization raw material supply nozzle portion. It is important to provide feed conditions such that the flow of polymerization feedstock exiting the nozzle mixes with the catalyst in a manner that washes the tip of the catalyst feed nozzle.

If a nozzle made of a specific material is used and the above-mentioned supply relationship is maintained, there will be no problem of clogging of the catalyst supply nozzle in the conventional method, and the copolymerization raw material can be used for an extremely long period of time. It was a completely unexpected discovery that it was possible to continuously produce a stable and high-quality oxymethylene copolymer that could be smoothly supplied and industrially advantageous. The method of the present invention essentially requires no other complex equipment or cumbersome operations, and no undesirable discolored foreign matter is formed in the catalyst supply nozzle.

This kind of technical knowledge was completely unknown and had never been suggested before, and it is possible to make predictions that would be impossible to obtain with conventionally used metal materials such as stainless steel. This is a far more amazing effect.

The comonomer used in the present invention is a cyclic ether or cyclic formal copolymerizable with trioxane, and particularly preferred examples include ethylene oxide, 1
, 3-dioquinolane, 1,4-butanediol formal, trioxepane, (113,5,7-titraoxacyclononane, 1,3+.

5.7.10-pentaoxacyclododecane), etc.

Further, the copolymerization catalyst used in the method of the present invention includes all catalysts known for producing oxymethylene copolymers, and industrially known cationic polymerization catalysts are advantageously used. Among them, boron trifluoride diethyl etherate and boron trifluoride dibutyl etherate are particularly preferred, and they are usually diluted with a suitable inert organic solvent and provided to the copolymerization system as a solution.

In the method of the present invention, it is of course possible to add additives such as molecular weight regulators that are advantageous for producing the desired copolymer, for example by mixing them with the polymerization components.

In the method of the present invention, the flow rate at the tip of each supply nozzle of the mixed copolymerization liquid of trioxane and a comonomer and the polymerization catalyst solution is, for example, 5 (7) 780
A linear velocity of 0 or more is desirable, and in combination with the use of a fluorine-containing resin in the nozzle part, even more remarkable effects can be obtained at a flow velocity of 0 or more, preferably 15 crn/sec or more.

Furthermore, in the present invention, the fluorine-containing resin used in the supply nozzle section is, for example, polytetrafluoroethylene (
PTFFi), polychlorotrifluoroethylene (PC
TFE), polyvinylidene fluoride (PVdF)
), a copolymer of tetrafluoroethylene and ethylene (ETPK), a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP), and a copolymer of tetrafluoroethylene and trifluoromethyl trifluorovinylether (P1t) 'A), etc., which are generally known as resins with excellent chemical resistance, heat resistance, and surface lubricity. In the method of the present invention, especially PT
F.K.

POTFE, 'FEP, PFA, etc. are preferably used.

Next, a feed section for copolymerization raw materials in a conventional oxymethylene copolymer continuous production apparatus used in the method of the present invention will be explained with reference to the drawings.

Figure 1 of the accompanying drawings is a schematic cross-sectional view of one example of a polymerization raw material supply section of an apparatus for continuously producing an oxymethylene copolymer used in the method of the present invention, and Figure 2 is a schematic sectional view of another similar example. FIG.

In FIG. 1, trioxane and a copolymerizable comonomer are usually mixed in advance in a predetermined ratio and fed into the polymerization apparatus through a supply pipe 1 through a nozzle 1' opened into the apparatus. Further, the polymerization catalyst is usually diluted with a suitable solvent, passed through the supply pipe 2 arranged in the supply pipe for the monomers, introduced through the nozzle 2' at the tip thereof, and injected from the nozzle 1. It is mixed with the copolymerized components in the mixing section 5. The supply pipes 1 and 2 are made of a metal such as stainless steel in a conventionally known device, but in the method of the present invention, they are made of a fluorine-containing resin. These feed sections are protected by a part 6 of the airtight shell constituting the copolymerization apparatus, and each feed pipe is installed through 6.

FIG. 2 shows another similar example, in which the copolymerization component supply pipe 1 and the catalyst supply pipe 2 are made of conventional metal such as stainless steel, and each pipe in the copolymerization apparatus is made of metal such as stainless steel. At the tips of the tubes, tubes 3 and 4 made of fluorine-containing resin are tightly fitted and connected to the copolymer component supply tube 1 and the catalyst supply tube 2, respectively. The injected substances are mixed at the open ends 5' of tubes 3 and 4 into the apparatus and pumped into the heated copolymerization zone.

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Example 1 In the apparatus shown in FIG. 1, the nozzle 2' has an inner diameter of 0.5
A PTFE tube with an inner diameter of 3 mm and an outer diameter of 4 m was used for the nozzle 1', and a trioxane molten mixture containing 2 parts by weight of ethylene oxide per 100 parts by weight of citrioxane was added to the supply pipe 1. 1 hourly
, 5 K9 were continuously supplied. At the same time supply pipe 2
Then, a catalyst solution prepared by diluting boron trifluoride dibutyl etherate 9,200 times with cyclohexane was continuously supplied at a rate of 46 g/hr, and all the raw materials were mixed in the mixing section 5, and then supplied to the continuous polymerization reactor. did. Polymerization was carried out continuously for 100 hours, during which time there was no phenomenon of nozzle clogging due to polymer formation, and a copolymer with stable polymerization yield and polymer viscosity was continuously obtained.

Comparative Example 1 The same operation as in Example 1 was performed except that a stainless steel pipe was used for the nozzle 2' in FIG.

Internal clogging of the nozzle 2' occurred two hours after the start of raw material supply, making continuous operation for a long time impossible.

Example 2 In Fig. 2, stainless steel pipes are used for supply pipes 1 and 2, FEP tubes with an inner diameter of 1 mm and an outer diameter of 21 ran are used for pipe 4, and a PT tube with an inner diameter of 8 mm and an outer diameter of 10 m+ is used for pipe 3.
A trioxane molten mixture containing 98 parts by weight of ethylene oxide and 2 parts by weight of ethylene oxide was supplied from supply pipe 1 to each of the FEli tubes at a rate of 10 Kf/hour. At the same time, feed pipe 2 with boron trifluoride dibutyl etherate diluted 9200 times with cyclohexane at a rate of 440 rnl/hour.

A reaction raw material mixture was formed in the mixing section 5' and continuously fed into the continuous polymerization reaction zone. Polymerization was carried out continuously for 360 hours, and during this period there was no nozzle clogging phenomenon, and the polymerization operation was extremely stable.

Comparative Example 2 In FIG. 2, except that tubes 4 and 3 were removed, Example 2
Performed exactly the same operation. Approximately 10 hours after the start of raw material supply, internal blockages occurred at the nozzle tips of tubes 1 and 2, making constant liquid feeding impossible.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of one example of a polymerization raw material supply section of an oxymethylene copolymer continuous production apparatus used in the method of the present invention, and FIG. 2 is a schematic sectional view of another similar example. In the figure, numeral 1 is a polymerizable component supply pipe, 2 is a catalyst supply pipe,
1' and 2' are nozzles of each supply pipe. Reference numerals 3 and 4 indicate fluorine-containing resin supply pipes that are fitted and connected to the nozzle portions of the supply pipes 1 and 2, respectively. Patent Applicant Asahi Kasei Industries Co., Ltd. Agent Akira Agata Figure 1 Figure 2

Claims (1)

[Claims] 1. A method for continuously obtaining an oxymethylene copolymer by continuously supplying trioxane and a cyclic ether or a cyclic formal together with a polymerization catalyst to a polymerization reactor, in which at least the nozzle portion of the polymerization catalyst supply pipe is The raw material for polymerization and the catalyst are mixed and supplied to the copolymerization reaction zone while being formed of a fluorine-containing resin and washing the tip of the polymerization catalyst supply nozzle with the flow of the mixture introduced from the raw material mixture supply nozzle for polymerization. A method for continuously supplying raw materials for polymerization, characterized in that: 2 The fluorine-containing resin is polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-ethylene copolymer,
The method of claim 1, wherein the method is selected from the group consisting of tetrafluoroethylene-hexafluoropropylene copolymer and tetrafluoroethylene-trifluoromethyltrialovinyl ether copolymer. 3. The method according to claim 1, wherein the flow velocity of each of the polymerization raw material mixture and the polymerization catalyst at the tip of the supply nozzle is 5 m/sec or more. 4. The method according to claim 1, wherein the nozzle portion of the polymerization raw material mixture supply pipe for producing an oxymethylene copolymer is formed of a fluorine-containing resin.