JPH051805B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing formaldehyde copolymers.

(Prior art) JP-A-59-115318 discloses formaldehyde, cyclic formal, and formaldehyde 100
Discloses a method of copolymerizing the formaldehyde and cyclic formal in the presence of boron trifluoride or its ether complex by continuously supplying 0.1 to 20 parts by weight of liquid hydrocarbon to a twin-screw mixer. has been done. This publication also describes that the copolymerization reaction heat is cooled by a cooler provided in an external loop in which the copolymer circulates.

(Problems to be Solved by the Invention) When carrying out the above method industrially, it is necessary to efficiently remove the copolymerization reaction heat in the cooler, and to remove the formaldehyde discharged from the cooler in the gas phase. It is desirable to treat and reuse mixed gases containing solvents.

(Means for Solving the Problems) The present invention provides a method for producing a formaldehyde copolymer that satisfies the above requirements.

According to the invention, formaldehyde, cyclic formal, and per 100 parts by weight formaldehyde
A first step of copolymerizing the formaldehyde and cyclic formal in the presence of boron trifluoride or its ether complex by continuously supplying 0.1 to 20 parts by weight of liquid hydrocarbon to a twin-screw mixer; The copolymer obtained in the process and an inert gas are introduced into a cooler to cool the copolymer, a part of the cooled copolymer is returned to the first step, and the remaining copolymer is extracted. , a second step in which a mixed gas consisting of formaldehyde, an inert gas, and a gaseous hydrocarbon is discharged; the mixed gas from the second step is supplied to a column filled with synthetic zeolite to selectively adsorb formaldehyde; and a fourth step in which the gas from the third step is cooled to condense gaseous hydrocarbons and returned to the first or second step, and the inert gas is returned to the second step. A method for producing characteristic formaldehyde copolymers is provided.

Each step of the present invention will be explained below.

First Step In the first step, formaldehyde and cyclic formal are copolymerized to obtain a formaldehyde copolymer.

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, 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.

Specific examples of hydrocarbons include aliphatic hydrocarbons such as pentane, hexane, and heptane, alicyclic hydrocarbons such as cyclohexane and cyclopentane, aromatic hydrocarbons such as benzene, toluene, and xylene, and halides of these hydrocarbons. can be mentioned. Hydrocarbon usage, supply formaldehyde
0.1 to 20 parts by weight, preferably 0.5 per 100 parts by weight
~5 parts by weight. If the amount used is less than the lower limit,
The activity of boron trifluoride or its ether complex used as a catalyst is greatly reduced, and the stability of the resulting copolymer in a basic medium is reduced. Even if the amount used is larger than the upper limit, there is no point in increasing the stability of the resulting copolymer in a basic medium.

Specific examples of boron trifluoride ether complexes include:
Examples include complexes of boron trifluoride and aliphatic ethers, such as dimethyl ether and diethyl ether. The amount of boron trifluoride or its ether complex used is usually 1x per mole of formaldehyde supplied.
10 ⁻⁵ to 1×10 ⁻³ mol. When using a boron trifluoride ether complex that is liquid at room temperature, it is preferable to use the boron trifluoride ether complex in a gas phase in advance for the reaction.

The two-shaft mixing agitator used in the present invention has two horizontal stirring shafts attached with a large number of elliptical mixing blades housed in an external case, and when the stirring shafts are rotated, This device has a small gap between the surface of the mixing stirring blade and the inner wall of the case. Such a twin-screw mixer is commercially available from Kurimoto Iron Works Co., Ltd. as a KRC kneader, for example.

The copolymerization reaction temperature is usually 40 to 80°C. The space velocity of formaldehyde in a twin-screw mixer is:
Usually 300 to 200 h ^-1 .

The copolymer cooled in the second step described below is supplied to the twin-screw mixer from a circulating copolymer supply port provided at one end thereof. Formaldehyde, cyclic formal, liquid hydrocarbon and catalyst are each fed to a twin-screw mixer. Formaldehyde and cyclic formal are copolymerized in the twin-screw mixer and are extracted together with the circulating copolymer from a copolymer outlet provided at the end opposite to the copolymer supply port.

Second Step In the second step, the copolymer from the first step is cooled to remove the copolymerization reaction heat.

Specific examples of the inert gas include nitrogen gas, argon gas, and helium gas.

As the cooler, a horizontal cooler in which a large number of stirring blades are attached to a stirring shaft can be used.

Methods for removing copolymerization reaction heat include an indirect cooling method in which the copolymerization reaction heat is cooled through a jacket attached to a cooler, and a direct cooling method in which a low-boiling-point hydrocarbon is supplied together with the above-mentioned inert gas into the cooler and the heat is cooled by its latent heat of vaporization. A cooling method and a method combining both can be adopted. In the indirect cooling method, if an attempt is made to ensure a sufficient heat transfer area, the cooler becomes larger, and if the temperature difference between the cooler wall and the copolymer is increased, the formaldehyde polymer adheres to the inner wall of the cooler and the heat transfer is increased. The thermal coefficient tends to decrease. On the other hand, the direct cooling method is preferably adopted in the present invention because the cooler can be made compact and the polymer can be prevented from adhering to the inner wall of the cooler.

The low-boiling hydrocarbons supplied to the cooler in the direct cooling method include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane, alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cycloheptane, and benzene. , an aromatic hydrocarbon such as toluene, or a mixed solvent thereof can be used. The amount of hydrocarbon supplied depends on the amount of heat of copolymerization reaction to be removed and cannot be uniformly prescribed, but can be easily determined by those skilled in the art in accordance with the teachings of the present invention.

Of the cooled copolymer, an amount corresponding to the amount of copolymer produced in the first step is extracted as a product, and the remaining copolymer is recycled and supplied to the first step. The amount of copolymer fed in circulation is preferably 50 to 200 times that of copolymer withdrawn.

A mixed gas consisting of formaldehyde gas, gaseous hydrocarbons, and inert gas is discharged from the cooler and subjected to the third step. The formaldehyde content of the mixed gas is usually 0.01 to 1% by weight.

Third Step In the third step, formaldehyde in the mixed gas from the second step is selectively removed.

As the synthetic zeolite, any known synthetic zeolite can be used, but among them, a synthetic zeolite with an average pore diameter of 4 Å, which has a high formaldehyde adsorption ability, can be preferably used.

Contact between the mixed gas and the synthetic zeolite is generally performed by passing the mixed gas through an adsorption tower filled with the synthetic zeolite. The amount of mixed gas supplied per unit weight of synthetic zeolite varies depending on the formaldehyde content in the mixed gas.
It cannot be specified uniformly. For example, when using a mixed gas having a formaldehyde content of 0.1% by weight, 0.1 to 50 parts by weight/hour of the mixed gas can be passed per 1 part by weight of synthetic zeolite. Contacting the mixed gas with the synthetic zeolite can usually be carried out at a temperature of 20 to 80°C.

Formaldehyde in the mixed gas is selectively adsorbed by bringing the mixed gas into contact with the synthetic zeolite.

If the third step of the present invention is not adopted and the mixed gas in the second step is immediately condensed to condense the hydrocarbons in the mixed gas, the following problem will occur. That is, as is well known, formaldehyde is a compound that polymerizes extremely easily, and when the above mixed gas is introduced into the condenser and cooled, the formaldehyde in the mixed gas polymerizes in the condenser.
It adheres to the walls of the condenser, rapidly reducing the heat transfer effect.

Synthetic zeolite that has adsorbed formaldehyde can be regenerated by efficiently desorbing formaldehyde without degrading the quality of formaldehyde by heating it to a low temperature of 120-150℃, preferably 130-140℃. . The desorbed formaldehyde can be reused, for example, as a formaldehyde source in the first step.

The gas from which formaldehyde has been removed is subjected to a fourth step.

Fourth Step In the fourth step, the gas from the third step is cooled to condense the gaseous hydrocarbons.

All known condensers can be used as the condenser.

In the present invention, since formaldehyde in the mixed gas is removed in the third step, gaseous hydrocarbons can be efficiently condensed without causing problems such as formaldehyde polymer adhesion to the inner wall of the condenser. I can do it.

The condensed liquid hydrocarbon is recycled as a hydrocarbon source in the first step or the second step. In addition, the inert gas is returned to the second step.

(Effects of the Invention) According to the present invention, the excellent effects of being able to efficiently remove copolymerization reaction heat and effectively reusing each starting material are achieved.

(Example) Examples are shown below.

The intrinsic viscosity of formaldehyde copolymer is α-
The measurement was carried out at 60°C using p-chlorophenol containing 2% by weight of pinene as a solvent.

What is the base stability of formaldehyde copolymer?
At a copolymer concentration of 10% by weight in benzyl alcohol containing 1% by weight of tri-n-butylamine.
It means the recovery rate (%) of the copolymer after heat treatment at 160°C for 1 hour.

Example 1 A KRC kneader #4 with a hopper manufactured by Kurimoto Iron Works Co., Ltd. was used as the twin-shaft mixing agitator for the first step, and a jacket portion and an internal cooling portion were used as the cooler for the second step, with a height of 435 mm and a width of 560 mm. Length 1150mm Internal volume 200
A twin-shaft flow stirring type cooler was used as the third step adsorber, which was a cylindrical adsorber (diameter 350 mm, height 300 mm) filled with 150 kg of synthetic zeolite with an average pore diameter of 4 Å.
A multi-tubular heat exchange type condenser (heat transfer area: 6 m ² ) was used as the condenser in the fourth step.

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 600 kg/h. Moisture content 50
~80ppm gaseous FA at 6Kg/h, gaseous TOC
was fed at a rate of 360 g/h, an equal weight mixture of benzene and cyclohexane at a rate of 142 g/h, and gaseous boron trifluoride at a rate of 18 mmol/h, each from an inlet provided downstream of the hopper. In order to maintain the kneader outlet temperature of the copolymer at 60°C, the amount of cooling water entering the jacket of the cooler and the internal cooler, the amount of N gas supplied to the cooler, and a mixture of benzene and cyclohexane (mixing ratio 1:1 by weight) were adjusted. The amount was adjusted. The amount of N at this time was 50 Nm ³ /H, and the amount of the mixture of benzene and cyclohexane was 30/H.

The mixed gas discharged from the cooler was led to an adsorption tower. At this time, when the mixed gas outlet FA concentration reached 0.1%, the adsorption tower was switched. Switching time is 15~
It was hot in 20 hours.

The mixed gas from which FA was removed in the adsorption tower was led to a shell-and-tube heat exchanger. Here, the mixed gas was cooled to 15°C, the mixed liquid was condensed, and the gas and liquid were separated. The liquid was pressurized by a pump and the gas was pressurized by a blower, and both were supplied to the cooler. In addition, a part of the condensed mixed liquid was returned to the first step.

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 500 hours.

As a result, the adsorption tower could be used repeatedly with regeneration at 140°C and could be operated without reducing the heat transfer capacity of the condenser or the cooling capacity of the cooler.

The ultimate clay of the resulting copolymer is 2.4, the base stability is 92%, the 1-pass FA yield is 99%, and the TOC content is
It was 1.5 mol%.

Comparative Example 1 Example 1 was repeated except that no adsorption tower was used. After 20 hours, the heat transfer capacity of the condenser decreased and it became impossible to operate.

Claims (1)

[Scope of Claims] 1. Formaldehyde, cyclic formal, and 0.1 to 20 parts by weight of liquid hydrocarbon per 100 parts by weight of formaldehyde are continuously supplied to a twin-shaft mixer, and the presence of boron trifluoride or its ether complex is Below, the first step of copolymerizing formaldehyde and cyclic formal, the copolymer obtained in the first step, and the cooled copolymer by introducing an inert gas into a cooler to cool the copolymer. A second step in which a part of the combined product is returned to the first step, the remaining copolymer is extracted, and a mixed gas consisting of formaldehyde, an inert gas, and a gaseous hydrocarbon is discharged; a mixed gas from the second step; a third step in which formaldehyde is selectively adsorbed by supplying it to a column filled with synthetic zeolite; and a first step or a second step in which the gas from the third step is cooled and gaseous hydrocarbons are condensed. A method for producing a formaldehyde copolymer, comprising a fourth step of returning the inert gas to the second step.