JP2845452B2 - Method for producing polyoxymethylene - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing polyoxymethylene using trioxane or tetraoxane as a main raw material.

<Prior Art> Polyoxymethylene is known as an engineering plastic having high crystallinity and excellent mechanical properties. Various methods are known as the manufacturing method,
Recently, a general method is to supply trioxane to a twin-screw mixer type polymerization reactor to carry out cationic bulk polymerization. Such polymerization methods are described, for example, in JP-A-56-38312 and 56-383.
13, 56-59824, 57-139113, 58-32619, 58-32620, 5
It is disclosed in JP-A-8-32621.

<Problems to be Solved by the Invention> However, continuous polymerization is possible by using the method described in the above-mentioned publications, but when operated for a long period of time, the polymer is gradually deposited on the inner wall surface of the cylinder,
The clearance from the tip of the paddle becomes almost zero, and a squeak sound is generated. When the squeak noise is generated, the stirring shaft is eccentric, the surface of the paddle is shaved, and the metal powder is mixed into the polymer, and the polymer is colored gray, or the load is applied to the motor to cause torque out. Further, when the scale is peeled, the stirring state is disturbed, and the particle size of the polymer powder becomes non-uniform or the degree of polymerization changes.

JP-A-56-38313, 58-32619, 58-32620, 58-3
Japanese Patent No. 2621 aims at preventing scaling by making the tip of the paddle a special shape, but this alone is insufficient, and stable operation over a long period of time has been difficult.

<Means for Solving the Problems> The present inventors have conducted intensive studies to solve the above problems, and as a result, have found the present invention.

In other words, the present invention provides a method for producing polyoxymethylene by homopolymerizing or copolymerizing trioxane or tetraoxane with a copolymer component using a twin-screw mixer type polymerization reactor, and comprises a liquid paraffin, a natural paraffin, a micro paraffin. A method for producing polyoxymethylene, comprising supplying at least one selected from wax, polyethylene wax, and fluorine-based hydrocarbon.

The polymerization reactor used in the present invention will be described with reference to FIGS. FIG. 1 shows that two circles having eccentric diameters are overlapped with each other.
FIG. 3 schematically shows a state in which a stirring shaft having a large number of paddles is disposed in a cylinder having a cross section of a letter shape. FIG. 2 schematically shows a cross section perpendicular to the stirring axis. The two stirring shafts are provided with a large number of paddles having a convex lens-shaped cross section. There are two types of paddles: flat type as shown in Fig. 3 (A) and helical type as shown in Fig. 3 (B). It can make the feeding action. Further, a paddle with a scraper as shown in FIG. 3 (C) can be used to further enhance the scaling prevention ability, or a pseudo-triangular paddle as shown in FIG. 3 (D) is used. You can also. The clearance between the tip of the paddle and the paddle surface and the inner wall surface of the cylinder is 2% or less, preferably 1% or less of the diameter of the circumscribed circle of the paddle. The thickness of the paddle is preferably 1/20 to 1/4 of the diameter of the circumscribed circle of the paddle.

In the reactor used in the present invention, since the feeding effect and the kneading effect can be changed by the arrangement of the paddle,
It is necessary to consider the arrangement according to the desired conversion and degree of polymerization. When using a convex lens type paddle, the padding effect is minimized by disposing the paddle from the supply port to the discharge port by 45 ° in the direction of rotation of the stirring shaft,
Further, when the paddles are arranged by being shifted by 45 ° in the direction opposite to the rotation direction, the feeding effect is maximized. Further, when the helical paddle is used, the feeding effect is increased, and when the inverted helical paddle is used, the feeding effect is reduced.

The ratio of the length (L) to the diameter (D) of the reactor, ie, L / D is 3
It is preferably 2 or less, more preferably 15 or less, and still more preferably 6 to 12. The polymerization of trioxane or tetraoxane undergoes a significant phase change with liquids, slurries, and powders.If the L / D is large, the stirring shaft will bend in areas where the phase change is large, or the torque will be abnormally increased, making operation impossible. Becomes On the other hand, if the L / D is small, the residence time is short, and the conversion is low, which is economically disadvantageous.

The reaction temperature is preferably 40 to 150 ° C., more preferably 50 to 150 ° C.
~ 110 ° C. Temperature control can be performed by providing a jacket outside the cylinder and circulating hot or cold water.

If the reaction temperature is low, the conversion will be low. If the reaction temperature is too high, depolymerization will proceed competitively and the degree of polymerization will decrease, so care must be taken.

Trioxane or tetraoxane used in the present invention may be supplied in a solid or crystalline state or may be supplied in a molten state, but is preferably supplied in a molten state.

In the present invention, homopolymerization of trioxane or tetraoxane or copolymerization with another copolymer component is possible.

Examples of the copolymerization component in this case include a cyclic ether and an olefin, and a cyclic ether represented by the general formula (A) is preferable.

(However, in the formula, Y _{1 to} Y ₄ represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a halogen-substituted alkyl group having 1 to 6 carbon atoms, and may be the same or different. , X represents a methylene or oxymethylene group, which may be substituted with an alkyl group or a halogen-substituted alkyl group, and m represents an integer of 0 to 3. Alternatively, X represents-(CH
_{2) p-O-CH 2} - or _{-O-CH 2 - (CH 2} ) p-O-CH
_2- , where m = 1 and p is an integer from 1 to 3. ).

Among the cyclic ethers represented by the general formula (A), particularly preferred compounds include ethylene oxide, propylene oxide, 1,3-dioxolan, 1,3-dioxane,
Examples include 3-dioxepane, 1,3,5-trioxepane, 1,3,6-trioxocan, epichlorohydrin and the like.

The copolymerization amount of the cyclic ether of the present invention must be in the range of 0.1 to 15 mol%, particularly preferably 0.2 to 5 mol%, based on trioxane or tetraoxane. The polymer yield when decomposed and removed for stabilization is low, and the productivity is lowered, which is not preferable. On the other hand, if it is 15 mol% or more, the melting point and crystallinity of the polymer are lowered, and the mechanical strength and the moldability are deteriorated.

The polymerization catalyst of the present invention is selected from the group consisting of boron trifluoride, boron trifluoride hydrate, and a coordination compound of boron trifluoride and an organic compound having an oxygen or sulfur atom.
One or more compounds may be used in gaseous, liquid or solution in a suitable organic solvent.

Organic compounds having an oxygen or sulfur atom forming a coordination compound with boron trifluoride include alcohols,
Ether, phenol, sulfide and the like can be mentioned.

Among these catalysts, a coordination compound of boron trifluoride is particularly preferable, and boron trifluoride / diethyl etherate and boron trifluoride / dibutyl etherate are particularly preferably used.

As the polymerization catalyst solvent of the present invention, benzene, toluene, aromatic hydrocarbons such as xylene, n-hexane,
Aliphatic hydrocarbons such as n-heptane and cyclohexane, alcohols such as methanol and ethanol, halogenated hydrocarbons such as chloroform, dichloromethane, and 1,2-dichloroethane, and ketones such as acetone and methyl ethyl ketone are used. .

The addition amount of the polymerization catalyst is based on 1 mole of trioxane.
It is in the range of 5 × 10 ^-6 to 1 × 10 ^-1 mol, particularly preferably 1 × 10 ^-5 to 1 × 10 ^-2 mol.

The liquid paraffin, natural paraffin, microwax, polyethylene wax, and fluorine-based hydrocarbon used in the production method of the present invention are generally added to improve the fluidity during heat molding of a thermoplastic resin, and the releasability. Things. A very large number of such compounds are known.

The fluorinated hydrocarbon used in the production method of the present invention refers to a substituted hydrocarbon having a structure in which a fluorine atom is directly bonded to carbon, and specifically, polytetrafluoroethylene, tetrafluoroethylene / hexa. Fluoropropylene copolymer, polyvinylidene fluoride,
Examples include polychlorotrifluoroethylene and tetrafluoroethylene / ethylene copolymer.

The liquid paraffin, natural paraffin, microwax, polyethylene wax, and fluorocarbon used in the present invention may be dissolved or suspended in trioxane, tetraoxane, a copolymer component, or a catalyst solution, and supplied to the polymerization reactor. Alternatively, it may be dissolved or suspended in another organic solvent and supplied to the polymerization reactor. Alternatively, it may be supplied as it is.

In addition, the supply amount is trioxane or tetraoxane 10
The amount is preferably 0.01 to 30 parts by weight, more preferably 0.1 to 10 parts by weight, based on 0 parts by weight. If the amount is less than 0.01 part by weight, the effect of addition is small, and if it exceeds 30 parts by weight, the mechanical properties of the polymer are undesirably reduced.

<Example> Hereinafter, the present invention will be described with reference to examples.

Incidentally, the polymerization reactor used in the examples and comparative examples,
The inner diameter was 100 mmφ, and L / D = 10.2. The paddle arrangement pattern is shown in FIG. The numbers shown in FIG.
When the discharge port is viewed from the raw material supply port, it represents a shift angle (゜) in the rotation direction of the stirring shaft.

Examples 1 to 16 Polymerization was carried out for a long time under the conditions shown in Table 1, and the presence or absence of squeak noise and the size of the obtained polymer powder were examined. Furthermore, 0.27 parts by weight of bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate (Sanol LS765 manufactured by Ciba-Geigy) was added to 2 parts by weight of benzene based on 100 parts by weight of the obtained polymer. The dissolved solution was added, and the mixture was stirred and pulverized in a Henschel mixer for 15 minutes to deactivate the catalyst. Furthermore, 0.5 parts by weight of triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] (Irganox 245 manufactured by Ciba-Geigy), 0.1 part by weight of calcium stearate, 0.1 part by weight of melamine Add the parts by weight and in Toyo Seiki Labo Plastomill, 230 ° C / 50rpm
, And the resulting polymer was measured for melt index (MI) at a load of 2,160 g and a temperature of 190 ° C.

Comparative Examples 1-4 Except not supplying the release agent, Examples 1, 11, 15,
Polymerization and melt stabilization were carried out in the same manner as in 17. Table 2 shows the results.

Comparative Rows 5 to 8 Polymerization and melt stabilization were performed in the same manner as in Comparative Rows 1 to 4 except that a paddle with a scraper as shown in FIG. 3 (C) was used. Table 2 shows the results.

Comparative Examples 9 to 12 Polymerization and melt stabilization were carried out in the same manner as in Comparative Examples 1 to 4, except that a pseudo-triangular paddle as shown in FIG. 3 (D) was used. Table 2 shows the results.

Examples 1 to 6 show that long-term continuous operation is possible regardless of the type, supply amount, and supply method of the release agent. The particle size of the polymer powder was fine and the quality was uniform.

From Examples 7 to 10, long-term continuous operation was possible even when the copolymerization components were changed. Further, it can be seen from Examples 11 and 12 that there is no problem even if the supply amount of the raw material is halved.

Examples 13 to 16 show that long-term continuous operation is possible in the same manner even when the main raw material is changed from trioxane to tetraoxane.

From Comparative Examples 1 to 4, it can be seen that long-term continuous operation is impossible without supplying a release agent.

From Comparative Examples 5 to 8, it can be seen that even if a paddle with a scraper as shown in FIG. 3 (C) is used, long-term continuous operation is impossible unless a release agent is supplied.

From Comparative Examples 9 to 12, it can be seen that long-term continuous operation is impossible even if a pseudo-triangular paddle as shown in FIG. 3 (D) is used without supplying a release agent.

<Effect of the Invention> By performing the production method of the present invention, the polymerization of trioxane or tetraoxane can be continuously performed for a long time. In addition, since a release agent is added during polymerization, the polymer finally obtained has excellent release properties.

[Brief description of the drawings]

FIG. 1 is a schematic view of a twin-screw reactor, and FIG. 2 is a cross-sectional view of a main part in a direction perpendicular to a stirring shaft of the twin-screw reactor.
FIG. 3A is a schematic diagram of a flat paddle, FIG. 3B is a schematic diagram of a helical paddle, FIG. 3C is a schematic diagram of a flat paddle with a scraper, and FIG. FIG. 4 is a schematic view of a triangular flat paddle, and FIG. 4 is a block diagram showing a paddle pattern. 1: stirring shaft, 2: trunk, 3: jacket, 4: supply port, 5: paddle,
6: Discharge port, 7: Feed screw

Continuation of front page (56) References JP-A-56-38312 (JP, A) JP-A-62-280253 (JP, A) JP-A-63-112650 (JP, A) JP-A-57-21414 (JP) JP-A-60-104161 (JP, A) JP-A-61-98767 (JP, A) JP-B-41-3714 (JP, B1)

Claims (2)

(57) [Claims] 1. A process for producing polyoxymethylene by homopolymerizing or copolymerizing trioxane or tetraoxane with a copolymer component using a biaxial mixing type polymerization reactor, comprising: liquid paraffin, natural paraffin, microwax, A method for producing polyoxymethylene, comprising supplying at least one selected from polyethylene wax and fluorine-based hydrocarbon. 2. The polymerization reactor has a jacket for temperature control on the outer periphery of a cylinder, and has a plurality of plate-like paddles fixed on two stirring shafts so as to be in contact with each other. Is opposed to one of the other paddles fixed to the stirring shaft, and that each paddle is arranged so as to rotate with a slight clearance between its tip and the surface of the paddle and the inner wall surface of the cylinder. The method for producing polyoxymethylene according to claim 1, wherein: