JPH0625239B2 - 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 formaldehyde copolymer having an appropriate molecular weight 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 the volatile organic solvent is used in the above direct cooling method without using the indirect cooling method, the polymer is hardly attached to the inner wall of the cooler and the stirrer, and the operation can be stably continued for a long time. As far as the inventors know,
There is no known literature relating to the direct contact of a powdery copolymer at elevated temperature with a volatile organic solvent and the removal of the heat of polymerization by the latent heat of vaporization of the organic solvent.

(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 In the method for producing a formaldehyde copolymer, which comprises the second step of extracting the amount of formaldehyde and the cyclic formal supplied to the first step out of the system out of the system and circulating the remaining copolymer to the first step Supplying a volatile organic solvent in a liquid phase to the cooler of the second step to directly contact the copolymer, and cooling the copolymer supplied from the first step by 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 2 is attached to the biaxial mixing agitator 1 via a screw conveyor 3. Boron trifluoride or its ether complex as a copolymerization catalyst and an organic solvent are continuously supplied into the screw conveyor 3 through the pipes 11 and 12, respectively. Formaldehyde tube 13
The cyclic formal is continuously introduced into the twin-screw mixing stirrer 1 via the tubes 14 and 13, respectively. The cooled formaldehyde copolymer, which is circulated from the second step at the same time, is continuously supplied to the biaxial mixing agitator 1 through the pipe 15, the hopper 2, and the screw conveyor 3.

The twin-screw mixing stirrer 1 used in the present invention has two horizontal stirring shafts, to which a large number of elliptical mixing stirring blades are attached, housed in an outer case. 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 biaxial mixing stirrer 1 is, for example, a KRC from Kurimoto Iron Works Co., Ltd.
It is commercially available as a kneader. Biaxial mixing agitator 1 has 1
It may be configured with only one machine, or may be configured with two or more machines provided in series or in parallel. For example, two twin-screw mixing stirrers 1 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 biaxial mixing stirrer 1 in a gas 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-Butagen-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 into a gas phase and use it for the reaction.

The presence of an inert organic solvent in the copolymerization reaction system is not essential, but the stability of the produced copolymer in a basic medium is increased, and the molecular weight of the produced copolymer is as high as practically required. In order to increase, 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 supplied to the biaxial mixing stirrer 1 in a liquid phase state.

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 that the mixture is made into a gas phase in advance and supplied to the biaxial mixing and stirring machine 1.

In the twin-screw mixing stirrer 1, the copolymerization of formaldehyde and cyclic formal proceeds in a 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 stirrer 1 is usually 300.
˜2000 h ⁻¹ .

The produced copolymer is discharged from the pipe 16 together with the circulating copolymer. The copolymer discharged is heated in the tube 1 by the heat of the copolymerization reaction.
It has a higher temperature than the circulating copolymer fed to the biaxial mixing agitator 1 through 5.

Second Step The formaldehyde copolymer produced in the first step is continuously supplied to the stirring type cooler 21 from the pipe 16 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.

The volatile organic solvent is supplied to the stirring cooler 21 from the pipe 17 in a liquid phase. 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 pentane, heptane, and hexane, and cycloaliphatic hydrocarbons such as cycloheptane and cyclohexane. . Among these volatile organic solvents, the stirring type cooler 2
Those having a boiling point lower than the temperature of the formaldehyde copolymer at the 1 outlet are preferably used. When using hexane or cyclohexane having a relatively high boiling point, it is effective to blow an inert gas at the same time to promote the evaporation of these solvents. Although not industrially advantageous, it is also possible to liquefy and use butane, propane, etc., which are gases at room temperature. In this case, the subsequent device needs to have a pressure resistant structure, and the device 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 evaporated organic solvent is guided to the condenser 22 through the pipe 18, and the condensed and liquefied organic solvent is circulated and supplied to the stirring type cooler 21 through the pipe 17. In front of the condenser 22, it is possible to provide an absorber for formaldehyde, which may be entrained in the evaporated organic solvent, for example, an absorber (not shown) filled with zeolite (not shown), so that the polymer adheres to the inner wall of the condenser 22. It is industrially preferable in terms of preventing

The cooled formaldehyde copolymer is discharged from the pipe 19 and supplied to the hopper 2 via the screw conveyor 23 and the pipe 15. 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 20. The remaining copolymer is circulated and fed to the biaxial mixing agitator 1 in the first step through a screw conveyor. The amount of formaldehyde copolymer circulated and supplied varies depending on the heat of copolymerization reaction to be removed, but it is usually 50 to 200% by weight of formaldehyde supplied.
Double.

(Example) An example is shown below.

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 K as a biaxial mixing stirrer with a hopper manufactured by Kurimoto Iron Works Co., Ltd.
RC 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.

About 40 kg of a copolymer of FA and TOC was put in the apparatus and circulated at 500 kg / h. 870 g / h of benzene,
Gaseous boron trifluoride was introduced at 17.5 mmol / h from the inlets provided between the hopper and the kneader. In addition, the amount of gaseous FA with a water content of 50-80 ppm is 5k.
Gaseous TOC at 260 g / h was introduced downstream of the kneader in the vicinity of the circulating copolymer inlet. FA and TOC under the above conditions
Was subjected to a copolymerization reaction with. 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, and the evaporated pentane was condensed in a condenser and then circulated and supplied to 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 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. 1 ... Biaxial mixing stirrer, 2 ... Hopper 21 ... Stirring type cooler, 22 ... 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. First step of copolymerizing formaldehyde and cyclic formal, the resulting copolymer is continuously supplied to an agitating cooler to be cooled, and formaldehyde to be supplied to the first step among the cooled copolymers and In a method for producing a formaldehyde copolymer, which comprises a second step in which an amount corresponding to the amount of cyclic formal is extracted from the system and the remaining copolymer is circulated in the first step, a volatile organic solvent is added to a cooler in the second step. A formaldehyde copolymer, characterized in that it is supplied in a liquid phase and 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. .