JPH0625240B2 - Formaldehyde copolymer manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a formaldehyde copolymer. More specifically, the present invention relates to a method for producing a formaldehyde copolymer capable of efficiently removing the heat of polymerization generated during the production of the formaldehyde copolymer.

(Prior art and its problems) It is known that a formaldehyde copolymer excellent in moldability, heat resistance and mechanical properties can be obtained by copolymerizing formaldehyde and cyclic formal.

The applicant of the present invention has disclosed that, in JP-A-59-115318, formaldehyde, cyclic formal and a specific amount of an inert organic solvent are supplied to a biaxial mixing stirrer in the presence of boron trifluoride or its ether complex. Discloses a method of copolymerizing formaldehyde and cyclic formal in a gas phase. According to this method, stability in a basic medium is good, and a moderate molecular weight of the formaldehyde copolymer can be obtained in a high yield.

In the method proposed above, in order to efficiently remove the heat of polymerization, the copolymer discharged from the twin-screw mixing agitator is supplied to an agitation-type cooler and cooled, and the amount of the copolymer corresponding to the amount of the monomer supplied is A method in which the polymer is taken out of the system as a product and the remaining copolymer is circulated and fed to a biaxial mixing stirrer is preferably adopted.

The present inventors have obtained the following findings as a result of investigating the cooling method in the cooler.

First, in a normal indirect cooling method in which a cooling medium is circulated through a jacket attached to a cooler or a hollow portion of a stirring shaft, it was confirmed that a polymer adheres to the heat transfer portion and the heat transfer efficiency is rapidly reduced. .

In order to eliminate the above-mentioned inconvenience, when the above indirect cooling method and the direct cooling method in which an organic solvent is introduced into the cooler and brought into contact with the copolymer to cool by the latent heat of vaporization of the organic solvent are used together, Although the amount of adhering polymer is considerably reduced, the adhering of polymer to the heat transfer part becomes visible when the operation is continued for a long time. As described above, as long as the indirect cooling method is adopted, a decrease in cooling efficiency due to the adhesion of the polymer to the heat transfer portion cannot be avoided.

Therefore, it was found that when a volatile organic solvent is used in the direct cooling method without adopting the indirect cooling method, there is almost no polymer adhesion to the inner wall of the cooler and the stirrer, and stable operation can be continued for a long time. . To the best knowledge of the inventors, there is no known literature relating to the direct contact of elevated temperature powdery copolymers with volatile organic solvents and removal of the heat of polymerization by the latent heat of vaporization of the organic solvent.

Further, in the vapor direct cooling method, it is industrially preferable to condense the organic solvent vapor discharged from the cooler and circulate and use the condensed organic solvent. By the way, since this organic solvent vapor contains a small amount of formaldehyde gas, if the organic solvent vapor is condensed as it is, the formaldehyde polymer adheres to the heat transfer surface of the condenser during long-term operation, and the heat transfer efficiency is improved. It causes deterioration and blockage of the condenser.

(Technical Means for Solving the Problems) According to the present invention, formaldehyde, cyclic formal and the cooled copolymer circulated from the second step are continuously fed to a twin-screw mixing stirrer, The first step of copolymerizing formaldehyde and cyclic formal in the presence of boron trifluoride or its ether complex, the resulting copolymer is continuously fed to an agitating cooler to cool, and the cooled copolymer A method for producing a formaldehyde copolymer comprising a second step in which an amount of formaldehyde and a cyclic formal to be co-fed in the first step are extracted from the polymer out of the system and the remaining copolymer is circulated in the first step In, the volatile organic solvent is supplied in a liquid phase to the cooler of the second step and is brought into direct contact with the copolymer, and the copolymer supplied from the first step is cooled by the latent heat of vaporization of the organic solvent. A method for producing a formaldehyde copolymer is provided.

Each step of the present invention will be described below with reference to FIG. 1 showing an example of an apparatus adopted for carrying out the present invention.

First Step A hopper 12 is attached to the biaxial mixing agitator 11 via a screw conveyor 13. Boron trifluoride or its ether complex as a copolymerization catalyst and an organic solvent are continuously supplied into the screw conveyor 13 through pipes 41 and 42, respectively. Formaldehyde is passed through pipe 43 and cyclic formal is fed through pipes 44 and 43.
Are continuously introduced into the biaxial mixing stirrer 1 via. The cooled formaldehyde copolymer, which is circulated from the second step at the same time in the biaxial mixing stirrer 11, is connected to the pipe 4
5, it is continuously fed through the hopper 12 and the screw conveyor 13.

The twin-screw mixing stirrer 11 used in the present invention has two horizontal stirring shafts, to which a large number of elliptical mixing stirrers are attached, housed in an outer case. When the stirring shaft is rotated, In addition, the device has a slight gap between the surface of the mixing and stirring blade and the inner wall of the case which are mutually opposed. Such a twin-screw mixing stirrer 11 can be manufactured, for example, by Kurimoto Iron Works Co., Ltd.
It is marketed as an RC kneader. Biaxial mixing stirrer 1
One may be composed of only one machine, or may be composed of two or more machines arranged in series or in parallel. For example,
Two twin-screw mixing stirrers 11 can be provided in series to divide the copolymerization reaction.

The water content of formaldehyde is preferably 0.1% by weight or less, and particularly preferably 0.01% by weight or less. Formaldehyde is supplied to the twin-screw mixing stirrer 11 in the vapor phase.

The formula for a cyclic formal is A compound represented by A compound represented by the formula (in both the above formulas, R ¹ , R ² , R
³ and R ⁴ respectively represent a hydrogen atom, an alkyl group, an allyl group and a cycloalkyl group, m is an integer of 1 to 3,
n represents an integer of 2 to 6) is used.

Specific examples of the cyclic formal include ethylene oxide, propylene oxide, butene-1-oxide,
1,3-Butadiene-1-oxide, styrene oxide, α-methylstyrene oxide, oxetane, tetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 2-phenyl-1,3-dioxolane, 4 -Phenyl-1,3-dioxolane, 1,
Examples thereof include 3-dioxopane, 2-butyl-1,3-dioxopane, 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, particularly 0.0
It is preferably 1 to 0.04 mol. When a cyclic formal that is liquid at room temperature is used, it is preferable to preheat it to make it into a gas phase and to participate in the reaction.

The presence of an inert organic solvent in the copolymerization reaction system is not essential, but increases the stability of the resulting copolymer in a basic medium,
In addition, in order to increase the molecular weight of the produced copolymer to a level required for practical use, it is preferable to use an inert organic solvent.

Specific examples of the inert organic solvent include aliphatic hydrocarbons such as pentane, hexane and heptane, aliphatic hydrocarbons such as cyclohexane and cyclopentane, aromatic hydrocarbons such as benzene, toluene and xylene, and halogens of these hydrocarbons. Compound. The amount of inert organic solvent used is
0.1 to 2 per 100 parts by weight of formaldehyde supplied
It is preferably 0 parts by weight, particularly preferably 0.5 to 5 parts by weight. The inert organic solvent is preferably in a liquid state and supplied to the biaxial mixing stirrer 11.

Specific examples of the boron trifluoride ether complex include a complex of boron trifluoride and an aliphatic ether such as dimethyl ether or diethyl ether. The amount of boron trifluoride or its ether complex used is 1
It is usually 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol per mol. In the case of a boron trifluoride ether complex that is liquid at room temperature,
It is preferable to make the gas phase in advance and supply it to the biaxial mixing agitator 11.

In the biaxial mixing stirrer 11, the copolymerization of formaldehyde and cyclic formal proceeds in the gas phase to form a formaldehyde copolymer.

The copolymerization reaction temperature is usually 40 to 80 ° C. The space velocity of formaldehyde in the biaxial mixing agitator 11 is usually 30.
It is 0-2000h- ¹ .

The produced copolymer is discharged from the pipe 46 together with the circulating copolymer. The copolymer discharged is heated by the heat of the copolymerization reaction,
It has a higher temperature than the circulating copolymer fed through 5 to the biaxial mixing agitator 11.

Second Step The formaldehyde copolymer produced in the first step is continuously supplied to the stirring type cooler 21 from the pipe 46 together with the circulating copolymer. As the agitating cooler 21, a uniaxial or biaxial agitator provided with a large number of agitating blades known per se can be used.

A volatile organic solvent is supplied to the stirring cooler 21 in a liquid phase through a pipe 47. As the volatile organic solvent, an organic solvent having a relatively low boiling point is used, and specific examples thereof include aliphatic hydrocarbons such as heptane and hexane, and alicyclic hydrocarbons such as cycloheptane and cyclohexane. Among these volatile organic solvents, those having a boiling point lower than the temperature of the formaldehyde copolymer at the outlet of the stirring-type cooler 21 are preferably used. Although it is not an industrially advantageous method, butane, propane, etc., which are gases at room temperature, can be liquefied and used. In this case, the recovery system becomes pressurized and becomes complicated.

In the stirrer cooler 21, the formaldehyde copolymer supplied from the first step comes into contact with the organic solvent, the organic solvent is heated and evaporated by the formaldehyde copolymer, and the copolymerization reaction is caused by the latent heat of vaporization at that time. The heat is removed.

The cooled formaldehyde copolymer is discharged from the pipe 48 and supplied to the hopper 12 via the screw conveyor 23 and the pipe 45. An amount corresponding to the amounts of formaldehyde and cyclic formal supplied to the first step is withdrawn as a product from the system via the pipe 49. The remaining copolymer is circulated and fed through the screw conveyor 12 to the stirring type cooler 11 in the first step. The amount of formaldehyde copolymer circulated and supplied varies depending on the heat of the copolymerization reaction to be removed, but it is usually 50 to 50% by weight of formaldehyde supplied.
It is 200 times.

The evaporated organic solvent is discharged through the pipe 50 and used in the third step. The organic solvent discharged from the pipe 50 is usually accompanied by 1 to 5% of unreacted formaldehyde in the first step and tokioxane produced in the same step.

Third step The organic solvent vapor from the pipe 50 is introduced into the lower part of the absorption tower 31. On the other hand, the formaldehyde absorbing liquid is introduced from the upper portion of the absorber 31 through the pipe 53.

As the formaldehyde absorbing liquid, alcohols having a boiling point higher than that of the organic solvent can be used, but polyethylene glycol, which has high absorbing performance for formaldehyde and trioxane, is preferably used. The molecular weight of polyethylene glycol is preferably 200 to 400.

The organic solvent vapor and the absorption liquid come into countercurrent contact in the absorption tower 31,
Formaldehyde and trioxane entrained in the organic solvent vapor are absorbed by the formaldehyde absorption liquid, and the absorption tower 3
It is discharged from the bottom of No. 1 via a pipe 51, and is optionally used in a process for recovering formaldehyde and trioxane. The formaldehyde absorbing liquid from which both are collected and removed can be circulated and supplied to the absorption tower 31.

The organic solvent vapor from which formaldehyde and trioxane have been removed is discharged from the top of the absorption tower 31 via a pipe 52 and supplied to the condenser 32. The organic solvent condensed and liquefied in the condenser 32 passes through the pipe 47 and cooler 2 of the second step.
1 is circulated.

As described above, the formaldehyde and trioxane entrained in the organic solvent vapor discharged from the second step are removed from the organic solvent vapor in the absorption tower 31, so that the condenser 32
Thus, when the organic solvent vapor is condensed, the polymer does not adhere to the heat transfer surface of the condenser 32, and the formaldehyde copolymer can be stably produced.

Before supplying the organic solvent vapor to the absorption tower 31, the catalyst may be removed through a device for removing a copolymerization catalyst that may be entrained in the organic solvent vapor, for example, a packed column of zeolite.

(Example) An example is shown below.

In the examples, a copolymer of formaldehyde and 1,3,6-trioxocane was produced using the apparatus shown in FIG.

The intrinsic viscosity of the formaldehyde copolymers obtained in the examples was measured at 60 ° C. using p-chlorophenol containing 2% by weight of α-pinene as a solvent. The base stability of formaldehyde copolymer is 1-tri-n-butylamine.
The recovery rate (%) of the copolymer when heat-treated at 160 ° C. for 1 hour at a copolymer concentration of 10% by weight in a benzine alcohol content.

Example 1 KR with hopper manufactured by Kurimoto Iron Works Co., Ltd. as a biaxial mixing agitator
C Kneader # 4 was used, and a paddle dryer NPD-1.6W manufactured by Nara Machinery Co., Ltd. was used as a stirring type cooler. All the copolymers were transported using a tube containing a screw conveyor. Using the above device, a copolymerization reaction of formaldehyde (hereinafter referred to as FA) and 1,3,6-trioxocane (hereinafter referred to as TOC) was continuously performed.

Approximately 40 kg of a copolymer of FA and TOC was put in the equipment and 5
It was circulated at 00 kg / h. Benzene (870 g / h) and gaseous boron trifluoride (17.5 mmol / h) were introduced through the inlets provided between the hopper and the kneader, respectively.
In addition, 5 kg / h of gaseous FA with a water content of 50-80 ppm
Then, 260 g / h of gaseous TOC was introduced into the vicinity of the inlet of the circulating copolymer of the kneader. A copolymerization reaction between FA and TOC was performed under the above conditions. The copolymer discharged from the kneader outlet was continuously supplied to the dryer.

Simultaneously with the start of the copolymerization reaction, pentane was introduced at a rate of 55 kg / h downstream of the copolymer inlet of the dryer.

Of the cooled copolymer, an amount corresponding to the introduced FA and TOC was extracted from the overflow line of the hopper.

The evaporated pentane was brought into countercurrent contact with polyethylene glycol in the absorption tower to remove entrained FA and trioxane, then condensed in a condenser, and then circulated to a dryer. The amount of FA and trioxane entrained in the organic solvent vapor was 3% by weight.

The continuous operation was continued for 336 hours. The kneader inlet temperature of the copolymer was 65 ° C, and the outlet temperature was 38 ° C.

The resulting copolymer has an intrinsic viscosity of 1.7, a base stability of 87%,
The FA yield in one pass was 98%, and the TOC unit content of the copolymer was 1.7 mol%.

Comparative Example 1 The same method as in Example 1 was repeated except that the copolymer was indirectly cooled by passing a refrigerant through a jacket attached to the dryer without introducing pentane to the dryer.

The polymer adhered to the inner wall of the dryer 120 hours after the start of operation, and the heat of the copolymerization reaction could be removed.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an apparatus used for implementing the present invention. 11 ... Biaxial mixing stirrer, 12 ... Hopper, 21 ... Stirring type cooler, 31 ... Absorption tower, 32 ... Condenser The abbreviations in FIG. 1 mean the following. FA: Formaldehyde, TOC: Cyclic formal, BF ₃ : Boron trifluoride, IOS: Inert organic solvent

Claims (1)

[Claims] 1. Formaldehyde, cyclic formal and the cooled copolymer recycled from the second step are continuously fed to a biaxial mixing stirrer in the presence of boron trifluoride or its ether complex. The first step of copolymerizing formaldehyde and cyclic formal, the resulting copolymer and the volatile organic solvent are continuously supplied to a stirring type cooler to bring them into contact with each other, and the first step is carried out by latent heat of vaporization of the organic solvent. From the cooled copolymer, the amount corresponding to the amounts of formaldehyde and cyclic formal to be supplied to the first step is extracted out of the system, and the remaining copolymer is cooled in the first step. The second step of circulating
And the organic solvent vapor discharged from the second step is supplied to the lower part of the formaldehyde absorption tower, and the formaldehyde absorbing liquid is supplied from the upper part to bring them into contact with each other to absorb and remove the formaldehyde entrained in the organic solvent vapor. A process for producing a formaldehyde copolymer, which comprises a third step of condensing the organic solvent vapor from which is removed, and then circulatingly supplying it to the second step.