JPH0621139B2 - Method for producing oxymethylene copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for producing an oxymethylene copolymer containing trioxane as a main raw material. In particular, it relates to a method in which a copolymerization component is prepolymerized and then reacted with trioxane.

<Prior Art> A method for obtaining an oxymethylene copolymer by copolymerizing trioxane and a cyclic ether in the presence of a boron trifluoride catalyst is known, for example, from Japanese Patent Publication No. 36640 / SHO.
Since then, various improvement methods have been proposed, but recently, 2
Many bulk polymerization methods using an axial reactor have been proposed.
For example, JP-A-51-84890, JP-A-53-86794, JP-A-55-164214, JP-A-56-38313,
JP-A-57-139113, JP-A-59-159812, JP-A-60-101108 and the like propose a method for producing an oxymethylene copolymer by a bulk polymerization method. <Problems to be solved by the invention Points> The above-mentioned JP-A-51-84890, JP-A-53-86794,
The techniques disclosed in JP-A-55-164214, JP-A-56-38313, JP-A-57-139113, and JP-A-60-101108 use almost no solvent, Although very advantageous in terms of energy, if a polymer with a high degree of polymerization is to be obtained in a high yield of 95% or more, a single twin-screw reactor is not possible because the residence time is too short. Alternatively, a multistage reactor is required. Also, for example, L /
Even if D is increased and the residence time is increased, the eccentricity of the rotating shaft in a twin-screw reactor with a large L / D is large because the reaction material changes greatly from liquid to slurry to lump to powder with the progress of polymerization. This causes steady operation to be difficult. Further, for example, in the above-mentioned JP-A-59-159812, trioxane, cyclic ether and catalyst are once pre-mixed and then fed to a biaxial reactor to shorten the residence time in the biaxial reactor. Attempts have been disclosed. However, since the mixture of the three types naturally reacts and solidifies easily, the polymer easily accumulates in the pre-mixer, and the supply port also easily clogs, which makes steady operation difficult. Therefore, the inventors of the present invention have made diligent studies to solve the above-mentioned problems of the prior art and obtain a high degree of polymerization polymer in a high yield in a short time in one stage of a biaxial or multiaxial reactor. Reached

<Means for Solving Problems> That is, the present invention is selected from the group consisting of boron trifluoride hydrate with ethylene oxide and a coordination compound of boron trifluoride and an organic compound containing an oxygen atom or a sulfur atom. Characterized in that a polyoxyethylene active polymer having a number average molecular weight of 100 to 20,000 or a solution thereof is prepared by prepolymerization in the presence of at least one polymerization catalyst, and the active polymer or the solution is brought into contact with trioxane. It is a method for producing an oxymethylene copolymer. The polymerization catalyst used in the present invention is boron trifluoride hydrate, and at least one compound selected from the group consisting of coordination compounds of boron trifluoride and an organic compound containing an oxygen atom or a sulfur atom, It is used in the form of a gas, a liquid or a suitable organic solvent. Examples of the organic compound having an oxygen atom or a sulfur atom which forms a coordination compound with boron trifluoride include alcohol, ether, phenol and sulfide. Among these catalysts, a coordination compound of boron trifluoride is particularly preferable, and particularly, boron trifluoride / diethyl ether complex, boron trifluoride / di (n-butyl) ether complex, boron trifluoride / phenol. Complexes are preferred. As the solvent for the polymerization catalyst in the present invention,
Aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as n-hexane, n-heptane and cyclohexane, alcohols such as methanol, ethanol and isopropanol, chloroform, dichloromethane and 1,2-dichloroethane. , Halogenated hydrocarbons such as carbon tetrachloride, ketones such as acetone and methyl ethyl ketone are used. The addition amount of the polymerization catalyst is 1 × 10 ⁻⁶ to 1 × 10 ^{6 with} respect to 1 mol of ethylene oxide.
^-1 mol is preferable, and 1 × 10 ^-4 to 1 × 10 ^-2 molga is particularly preferable. The method of mixing ethylene oxide and the polymerization catalyst is not particularly limited, and a method of stirring the polymerization catalyst and ethylene oxide with a mixer with a stirrer, a method of stirring the organic solvent solution of the polymerization catalyst and ethylene oxide with a mixer with a stirrer, and the like can be used. The prepolymerization temperature is in the temperature range of -50 to 150 ° C, preferably -30 to 10 ° C.

The prepolymerization time can be arbitrarily selected. If the reaction is carried out at a high temperature, the prepolymerization time may be short, and if the prepolymerization is carried out at a low temperature, it should take a long time. That is, the prepolymer may be prepared so that the number average molecular weight thereof falls within the range of 100 to 20,000. When the number average molecular weight is less than 100, an effective amount of cationically active species is not sufficiently generated and the initiation reaction time becomes long, which is not preferable. Further, when the number average molecular weight exceeds 20,000, the viscosity of the prepolymer is high and it becomes difficult to supply it, or the block copolymer is formed, which is not preferable in terms of physical properties. The reaction method of the prepolymer and trioxane is
There is no particular limitation, and a known device is used, but in the case of bulk polymerization, rapid solidification and heat generation during polymerization occur, so that it has a strong stirring ability and a self-cleaning type mixing device capable of controlling the reaction temperature. Are particularly preferably used. The polymerization temperature is preferably in the range of 65 to 125 ° C, particularly preferably in the range of 65 to 110 ° C. At 65 ° C or lower, the polymerization rate is slow because trioxane is a solid, and at 125 ° C or higher, the depolymerization reaction becomes predominant.
High molecular weight polymer cannot be obtained. The oxymethylene copolymer produced according to the present invention is put into practical use after being stabilized by blocking or removing unstable terminals.
As a stabilizing method in this case, a known method is usually adopted.

<Operation> In the present invention, ethylene oxide is ring-opened by the polymerization catalyst to generate an active cation species in advance, which causes the polymerization of trioxane, so that the degree of polymerization is increased in a short time and the yield is also improved. Conceivable.

<Example> Next, the present invention will be described with reference to Examples and Comparative Examples. In addition,
The physical properties and the like of the molded products shown in Examples and Comparative Examples were measured as follows.

Number average molecular weight of prepolymer Mn; measured by GPC.

Column: TSK-gel G2500HXL, G4000HXL, G7000HXL One each in series (Toyo Soda) Solvent: THF Flow rate: 1 ml / min Temperature: 40 ° C Detector: Differential refractive index detector Relative viscosity of oxymethylene copolymer ηr; 100m p-chlorophenol containing 2% α-pinene
0.5 g of oxymethylene copolymer was dissolved in 1 liter and measured at 60 ° C. using an Ostwald viscometer.

Thermal decomposition rate of oxymethylene copolymer Kx; Kx means the decomposition rate when left standing at x ° C. for a certain time,
Using a thermobalance device, about 10 mg of sample was allowed to stand at x ° C. in an air atmosphere and determined by the following formula.

Kx = (W ₀ −W ₁ ) / W ₀ × 100% W ₀ ; sample weight before heating W ₁ ; 〃 after 〃 The thermobalance device is a thermal analyzer 1090/109 manufactured by DuPont.
1 was used.

Melting point (Tm), crystallization temperature (Tc) of oxymethylene copolymer; 10 ° C / min under nitrogen atmosphere using differential scanning calorimeter
The temperature was raised at a rate of 1, the melting point (Tm) was measured, the temperature was lowered at 10 ° C / min, and the crystallization temperature (Tc) was measured. Differential scanning calorimeter is Du
A thermal analyzer 1090/1091 from Pont was used.

Mechanical Properties of Oxymethylene Copolymer; Using an injection molding machine with an injection capacity of 5 ounces, a cylinder temperature of 230 ° C, a mold temperature of 60 ° C, a molding cycle of 50 seconds are set, and a tensile test piece and an Izod impact test piece are injection molded. did. Using these molded products, the tensile strength and Izod impact value were measured according to ASTM D-638 and D-256, respectively.

Polymerization yield of oxymethylene copolymer: 100 g of oxymethylene copolymer obtained by the reaction of trioxane and a prepolymer was stirred in 500 ml of benzene at room temperature for 30 minutes, and then the polymer was separated and dried in vacuum. The polymer weight after drying was measured to determine the polymerization yield (%).

Examples 1 to 5 and Comparative Example 1 382 g of ethylene oxide was added to a mixed solution of 2.30 g of boron trifluoride / diethyl etherate and 88.0 g of benzene, and the mixture was stirred while keeping the internal temperature at 5 ° C. After a predetermined time, G
The number average molecular weight of the prepolymer was measured by PC analysis.
Further, 72 g of the prepolymer thus prepared and 3000 g of trioxane were put into a 31 kneader having two Σ-type stirring blades heated to 80 ° C. and stirred at 50 rpm for 3 minutes. The contents immediately solidified and crushed into a white powder. The relative viscosity ηr. The melting point Tm and the crystallization temperature Tc were measured. The results are summarized in Table 1. Also,
As Comparative Example 1, polymerization was carried out in the same manner as in Examples 1 to 5 except that boron trifluoride / diethyl etherate / benzene mixed solution, ethylene oxide and trioxane were simultaneously charged into 31 kneader. The results are also shown in Table 1.

It is clear from Table 1 that in the reaction between the prepolymer and trioxane, the degree of polymerization is increased and the yield is high within 3 minutes. On the other hand, when it is carried out without prepolymerization as in Comparative Example 1, the degree of polymerization cannot be increased in a short time and the yield is low.

Examples 6 to 9 The procedure of Example 1 was repeated except that the prepolymerization temperature was changed. The results are summarized in Table 2.

It is clear from Table 2 that even if the prepolymerization temperature is changed and the number average molecular weight of the prepolymer is changed, both the viscosity and the yield of the finally obtained oxymethylene copolymer are high. Further, there are no changes in the physical properties such as melting point and crystallization temperature.

Examples 10 to 12 The procedure of Example 1 was repeated except that the solvent for prepolymerization was changed. The results are summarized in Table 3.

It is clear from Table 3 that the viscosity and yield of the finally obtained oxymethylene copolymer do not change significantly even if the solvent during prepolymerization is changed. In addition, there is no significant change in physical properties such as melting point and crystallization temperature.

Example 13, Comparative Example 2 The degree of polymerization of the prepolymer was controlled by temperature and time without using a solvent. In addition, oxymethylene copolymer was polymerized using these prepolymers. The results are summarized in Table 4.

It is apparent from Table 4 that prepolymerization is possible even in a solventless system,
It can be seen that the finally obtained oxymethylene copolymer has a high degree of polymerization and a high yield. However, if the degree of polymerization of the prepolymer is too high as in Comparative Example 2, the copolymerized units enter into a block form and the melting point of the finally obtained oxymethylene copolymer becomes high.

Examples 14 to 16 and Comparative Example 3 The procedure of Example 1 was repeated except that a di (n-butyl) ether complex, a phenol complex or a diphenyl sulfide complex was used as the catalyst instead of the boron trifluoride / diethyl ether complex. It was As a comparative example, polymerization was carried out using a boron trifluoride / triethylamine complex as a catalyst. The results are summarized in Table 5.

It is clear from Table 5 that when the compound forming a complex with BF ₃ is an oxygen or sulfur atom-containing compound, both the degree of polymerization and the yield of the finally obtained oxymethylene copolymer are high. On the other hand, when the compound forming a complex with BF ₃ is an amine as in Comparative Example, the degree of polymerization and the yield of the oxymethylene copolymer finally obtained are both low.
Based on 100 parts by weight of the polymer obtained in Examples 1 to 16,
(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate 0.27 parts by weight, triethylene glycol-bis [3- (3-t
-Butyl-5-methyl-4-vidroxyphenyl) propionate] 0.50 parts by weight and calcium hydroxide 0.10 parts by weight were added, and the mixture was mixed in a mixer having two roller type blades.
The mixture was melt-kneaded at 0 ° C for 10 minutes. The obtained polymer was crushed and injection-molded, and the mechanical properties and heat resistance stability of the molded product were measured, and all showed good values. For reference, the measured values of the polymer obtained from Example 1 are shown below.

Tensile strength: 63 MPa Tensile rupture elongation: 65% Izod impact value: 6.7 kgcm / cm (1/2 notch); Thermal decomposition rate: K240 (60min) = 3.2% Comparative example 4 Separately in place of the active polymer Polymerization of trioxane was performed using the polymerized polyethylene glycol as a copolymerization component. Commercially available polyethylene glycol was used. The number average molecular weight calculated from the analysis of terminal OH groups was 1000. This polyethylene glycol
57 g, trioxane 3000 g, and a mixed solution of boron trifluoride / diethyl etherate 0.3 ml / benzene 15 ml.
Heated to 80 ° C. It was put into a 31 kneader having two Σ type stirring blades and stirred at 50 rpm. After about 5 minutes, the content began to solidify, gradually became a lump, and was further pulverized into a powder. Stirring was stopped 10 minutes after the start of the reaction, and the relative viscosity ηr, melting point Tm, and crystallization temperature Tc of the polymer powder were measured.

The polymerization time is longer than that of the examples of the present invention, and the degree of polymerization and the polymerization yield are low. Further, since the copolymerization component enters the block form, the melting point becomes high.

Example 17 25 kg / h of trioxane from a raw material supply port provided at one end of a twin-screw mixer having a barrel inner diameter D = 100 mm and L / D = 10 and a preliminary prepared in the same manner as in Example 1. A polymerization solution of 0.6 kg / h was supplied to carry out polymerization inside a biaxial mixer, and a white powdery oxymethylene copolymer was obtained from a discharge port provided at the other end. A flat paddle with a convex lens cross section and a total of 36 helical paddles per shaft are attached to the shaft of the biaxial mixer, and the raw material supply section and discharge section are ordinary feed screws. There is a small clearance between the tip of the paddle and the inner wall of the mixer or the paddle surface of the other shaft, which corresponds to 1/100 of the major axis of the paddle. Rotate in the same direction by stroking the paddle surface of. The mixer is equipped with a hot water jacket and is kept at 90 ° C. The rotation speed of both shafts is 175r
It was set to pm, but the average residence time at this time was 3 minutes. The powdery polymer obtained from the discharge port was 25.5 kg / h. When a part of the polymer was taken and the polymerization yield was measured,
It was 98%. 0.27 parts by weight of bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate per 100 parts of the polymer thus obtained, triethylene glycol-bis [3- (3-t- Butyl-5-methyl-4-hydroxyphenyl) propionate] 0.50 parts by weight, calcium hydroxide
0.10 parts by weight was added, and the mixture was continuously fed to a twin-screw mixer of the same type as the above-mentioned polymerization reactor to stabilize the melting. However, this twin-screw mixer is provided with a bend port 5D to 8D from the supply port toward the discharge port, and formaldehyde gas can be removed by depressurizing at the time of stabilization. In addition, a die is attached to the discharge port so that the stabilized polymer can be drawn as a strand. Further, the twin-screw mixer is equipped with an oil circulation jacket so that it can be heated to 210 to 230 ° C. In this example, the unstabilized polymer mixed with the above additives was supplied at 25 kg / h and melt-stabilized at 230 ° C. and a vent of 100 mmHg. Melt-stabilized polymer as pellets
Obtained at 22.5 kg / h. For 100 parts by weight of this pellet
0.1 part by weight of dicyandiamide was added and melt-kneaded at 190 ° C. using a twin-screw extruder. Injection molding was performed using this polymer, and the mechanical properties and heat stability of the molded product were measured. The results are shown below.

Tensile strength; 64MPa Tensile elongation at break; 64% Izod impact value; 6.7 kg.cm/cm (1/2 notch) thermal decomposition rate; K240 (60min) = 3.0% <Effect of the invention> Use the manufacturing method of the present invention As a result, a polymer having a high degree of polymerization can be obtained within an extremely short time, so that the manufacturing process can be significantly shortened. Furthermore, since the finally obtained polymer has excellent mechanical properties and heat resistance stability, it can be used in a wide range of applications such as machine mechanism parts and electric / electronic parts.

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Claims (5)

[Claims] 1. Preliminary ethylene oxide is prepared in the presence of at least one polymerization catalyst selected from the group consisting of boron trifluoride hydrate and a coordination compound of boron trifluoride and an organic compound containing an oxygen atom or a sulfur atom. A method for producing an oxymethylene copolymer, which comprises polymerizing to prepare a polyoxyethylene active polymer having a number average molecular weight of 100 to 20,000 or a solution thereof, and bringing the active polymer or the solution into contact with trioxane. 2. A polymerization catalyst selected from the group consisting of boron trifluoride / diethyl ether complex, boron trifluoride / di (n-butyl) ether complex and boron trifluoride / phenol complex. The manufacturing method according to the item. 3. The production method according to claim 1, wherein the prepolymerization temperature is -50 to 150 ° C. 4. The method according to claim 1, wherein the active polymer obtained by prepolymerization or a solution thereof is reacted with trioxane at 65 to 125 ° C. 5. The production method according to claim 1, wherein the prepolymerization is carried out in an organic solvent having 1 to 20 carbon atoms.