JPH0542451B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a formaldehyde copolymer, and more particularly, to a method for producing a high molecular weight formaldehyde copolymer suitable for extrusion molding or blow molding. .

(Prior art) JP-A-59-115318 discloses that formaldehyde, cyclic formal, and a specific amount of an inert organic solvent are continuously supplied to a twin-screw mixer, and the presence of boron trifluoride or its ether complex is A method for copolymerizing the formaldehyde and a cyclic formal is disclosed below. According to this method, the copolymerization reaction can be carried out substantially in a gas phase state, and a formaldehyde copolymer having good stability in basic solvents can be produced in good yield. be done.

(Problems to be Solved by the Invention) The formaldehyde copolymer obtained by the above method has a sufficient molecular weight for injection molding. It has a problem of low molecular weight for molding.

(Means for solving the problem) As a result of the inventors' detailed study of the above method,
As an inert organic solvent supplied to the copolymerization reaction system,
The present invention was completed based on the discovery that the molecular weight of the resulting copolymer can be increased by using a mixed solvent of aromatic hydrocarbons and aliphatic hydrocarbons.

According to the invention, formaldehyde, cyclic formal, and per 100 parts by weight formaldehyde
Continuously supplying 0.1 to 20 parts by weight of an inert organic solvent to a twin-screw mixer and copolymerizing the formaldehyde and cyclic formal in the presence of boron trifluoride or its ether complex. A method for producing a formaldehyde copolymer is provided, which is characterized in that a mixed solvent of an aromatic hydrocarbon and an aliphatic hydrocarbon is used as a solvent.

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 A compound represented by, and the formula A compound represented by (in both the above formulas, R ¹ , R ² ,
R ³ and R ⁴ are each a hydrogen atom, an alkyl group,
Indicates an allyl group and a cycloalkyl group, m is 1 to
An integer of 3, n represents an integer of 2 to 6. ) is used. Specific examples of cyclic formals 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, 1,3-dioxopane, 1,
3,6-trioxocane and 1,3,5-trioxopane are mentioned. The amount of cyclic formal used is per mole of formaldehyde supplied,
It is preferably 0.001 to 0.1 mol, particularly 0.01 to 0.04 mol.

The two-shaft mixing agitator used in the present invention has two horizontal stirring shafts equipped 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 as a KRC kneader from Kurimoto Iron Works Co., Ltd., for example.

In the present invention, a mixed solvent of aromatic hydrocarbons and aliphatic hydrocarbons is used as the inert organic solvent. Specific examples of aromatic hydrocarbons include benzene, toluene, and xylene. Aliphatic hydrocarbons in the present invention include alicyclic hydrocarbons, specific examples of which include pentane, hexane,
Examples include heptane, cyclohexane, cyclopentane and their halides. The ratio of aliphatic hydrocarbons to aromatic hydrocarbons is expressed as a weight ratio.
It is preferably from 0.1 to 10, particularly from 0.5 to 5. If this ratio is too small, the molecular weight of the resulting copolymer will not be sufficiently high, and if this ratio is too high, the ability to dissolve trioxane by-produced in the copolymerization reaction will be reduced. The total amount of inert organic solvent used is from 0.1 to 20 parts by weight, preferably from 0.5 to 5 parts by weight, per 100 parts by weight of formaldehyde fed. If the amount used is less than the lower limit, the activity of boron trifluoride or its ether complex used as a catalyst will be greatly reduced, and the resulting copolymer will have low stability in a basic solvent. Even if the amount used is larger than the upper limit, the stability of the resulting copolymer in basic solvents will not be further increased, and the resulting copolymer will become wet and difficult to move, and the inert organic solvent will Recovery costs will increase.

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 1 mol per mol 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 heat of the copolymerization reaction is usually removed using a separate external circulation cooler in the loop that circulates the copolymer. Cooling methods using this external circulation cooler include indirect cooling using a cooling jacket, direct cooling in which a low boiling point solvent is supplied into the cooler and its latent heat of vaporization is utilized, and a combination of both methods is adopted as appropriate. can do.

The copolymerization reaction temperature is usually 40 to 80°C. The space velocity of formaldehyde in a twin-screw mixer is usually 300 to 2000 h.

Next, the present invention will be explained based on one embodiment shown in the drawings.

Twin-shaft mixing stirrer 1 used as a polymerization reactor
consists of an external case 2 and two horizontal stirring shafts 4 equipped with a large number of elliptical mixing and stirring blades 3a and 3b.
It is composed of a and 4b. As shown in FIG. 2, when the stirring shafts 4a, 4b are rotated, the mixing stirring blades 3a, 3b have a small gap between the other surface and the inner wall of the outer case 2, usually 0.5 to 5 mm.
form a gap.

Inert organic solvents, boron trifluoride, formaldehyde and cyclic formal, respectively,
12, 13 and 14. . Formaldehyde copolymer from a cooler (not shown) is in tube 1.
Supplied from 5. The amount of copolymer fed through tube 15 varies depending on the heat of polymerization to be removed by the cooler, but is typically 50 to 200 times the weight of formaldehyde fed.

A copolymerization reaction between formaldehyde and cyclic formal is carried out in the twin-shaft mixer 1 in which the stirring shafts 4a, 4b and the mixing blades 3a, 3b are driven by a motor (not shown). The product copolymer is discharged from pipe 16 along with the circulating copolymer.

(Effects of the Invention) According to the present invention, a formaldehyde copolymer having a high molecular weight and excellent stability in a basic medium can be obtained with high productivity, as can be seen from the results of Examples described below. . The formaldehyde copolymer obtained by the present invention is particularly excellent for extrusion molding and blow molding.

(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 polymerization reactor equipped with a hopper manufactured by Kurimoto Iron Works Co., Ltd.
Using KRC kneader #4, height 435mm, width 560mm with jacket part and internal cooler as cooler.
A twin-shaft mixing stirring type cooler with a length of 1150 mm and an internal volume of 200 mm was used.

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
360 g/h, and an equal weight mixed solvent of benzene and cyclohexane at 142 g/h.
and 12. The exit temperature of the copolymer
The amount of water entering the jacket and internal cooling section of the cooler was adjusted to maintain the temperature at 60°C. The resulting copolymer was withdrawn from the hopper overflow line and contacted with gaseous ammonia to deactivate the boron trifluoride. This continuous operation was carried out for 240 hours.

The resulting copolymer has an intrinsic viscosity of 2.4, a base stability of 92%, a 1-pass FA yield of 99%, and a TOC content of
It was 1.5 mol%.

Comparative example 1 142g/h of benzene instead of equal weight mixed solvent
The same method as in Example 1 was repeated, except that

The resulting copolymer has an intrinsic viscosity of 1.7, a base stability of 88%, a one-pass FA yield of 99%, and a TOC content of
It was 1.5 mol%.

Comparative example 2 142g/h of toluene instead of equal weight mixed solvent
The same method as in Example 1 was repeated, except that

The intrinsic viscosity of the resulting copolymer was 1.6, the base stability was 87%, the 1-pass FA yield was 99%, and the TOC content was
It was 1.5 mol%.

Comparative Example 3 Cyclohexane was used instead of an equal weight mixed solvent of 142
The same procedure as in Example 1 was repeated, except that the feed was carried out at g/h.

The intrinsic viscosity of the resulting copolymer was 1.6, the base stability was 87%, the 1-pass FA yield was 99%, and the TOC content was
It was 1.5 mol%.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a polymerization reactor that can be used in the present invention, and FIG. 2 is a sectional view taken along the line A--A in FIG. 1. 1...Two-shaft mixing stirrer, 3...Mixing stirring blade, 4
……Axis of rotation.

Claims (1)

[Claims] 1. Continuously feed formaldehyde, cyclic formal, and an inert organic solvent of 0.1 to 20 parts by weight per 100 parts by weight of formaldehyde to a twin-shaft mixer, and mix the formaldehyde and the above in the presence of boron trifluoride or its ether complex. A method for producing a formaldehyde copolymer, which comprises using a mixed solvent of an aromatic hydrocarbon and an aliphatic hydrocarbon as an inert organic solvent when copolymerizing a formaldehyde copolymer with a cyclic formal.