JPH0662730B2 - 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. 36-14640. Since then, various improved methods have been proposed, but recently, many bulk polymerization methods using a biaxial reactor have been proposed. For example, JP-A-51-84890 and JP-A-53-86794
JP, JP-A-55-164214, JP-A-56-38313, JP-A-57-139113, JP-A-59-159812, JP-A-60-101108, etc. A method for producing an oxymethylene copolymer by a polymerization method has been proposed.

<Problems to be Solved by the Invention> JP-A-51-84890, JP-A-53-86794, JP-A-55-164214, JP-A-56-38313, The techniques disclosed in JP-A-57-139113 and JP-A-60-101108 are very advantageous in terms of energy because they use almost no solvent, but a polymer having a high degree of polymerization of 95% or more is used. In order to obtain a high yield, a single biaxial reactor is not possible because the residence time is too short, and inevitably a two-stage or multi-stage reactor is required.

Further, for example, even if L / D is made large and the residence time is made long, the reaction material largely changes from liquid to slurry to agglomerate to powder with the progress of polymerization, so that L / D is large.
In a shaft reactor, eccentricity of the rotating shaft occurs, which makes steady operation difficult. Further, for example, in the above-mentioned JP-A-59-159812, trioxane, cyclic ether and catalyst are pre-mixed once 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 present inventors have solved the above-mentioned problems of the conventional technology,
The present invention has been achieved as a result of intensive studies to obtain a high-polymerization degree polymer in a high yield in a short time in one stage of a biaxial or multiaxial reactor.

<Means for Solving Problems> That is, the present invention, 1,3-dioxolane from boron trifluoride hydrate and a coordination compound of boron trifluoride and an organic compound containing an oxygen atom or a sulfur atom Prepolymerization in the presence of at least one polymerization catalyst selected from the group consisting of and an organic solvent to prepare a poly (oxymethylene / oxyethylene) active copolymer solution having a number average molecular weight of 150 to 20,000, and the active copolymer A method for producing an oxymethylene copolymer, which comprises contacting the solution with trioxane.

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, which is used as a gas, liquid or solution of a suitable organic solvent. As the organic compound having an oxygen or sulfur atom which forms a coordination compound with boron trifluoride, alcohol, ether, phenol,
Examples thereof include 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.

Examples of the solvent for the polymerization catalyst in the present invention include 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, 1,
2-Dichloroethane, halogenated hydrocarbons such as carbon tetrachloride, acetone, ketones such as methyl ethyl ketone are used.

The addition amount of the polymerization catalyst is preferably 1 × 10 ⁻⁶ to 1 × 10 ⁻¹ mol, and particularly 1 × 10 ¹ mol to 1 mol of 1,3-dioxolane.
10 ⁻⁴ to 1 × 10 ⁻² mol is preferable.

The method for mixing the 1,3-dioxolane, the polymerization catalyst and the organic solvent is not particularly limited, and the method for stirring the polymerization catalyst, the 1,3-dioxolane and the organic solvent with a mixing device with a stirrer, and the organic solvent solution of the polymerization catalyst A method of stirring 1,3-dioxolane with a mixer equipped with a stirrer can be used.

The prepolymerization temperature is in the temperature range of -30 to 150 ° C, especially 0 to 70 ° C.
Is preferred.

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 number average molecular weight of the prepolymer may be adjusted to fall within the range of 150 to 20,000. If the number average molecular weight is less than 150, 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 from the viewpoint of physical properties.

The reaction method of the prepolymer and the trioxane is not particularly limited, and a known device is used, but in the case of bulk polymerization, rapid solidification or heat generation during polymerization occurs, so that it has a strong stirring ability. A self-cleaning type mixing device capable of controlling the reaction temperature is 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. Below 65 ° C, the polymerization rate is slow because trioxane is a solid, and above 125 ° C, the depolymerization reaction becomes predominant and a 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, 1,3-dioxolane is ring-opened by a polymerization catalyst to generate an active cation species in advance, which causes polymerization of trioxane, so that the degree of polymerization is increased in a short time, and the yield is also increased. Is also expected to improve.

<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.

The number average molecular weight Mn of the prepolymer was measured by GPC.

Column; TSK-gel G2500HXL, G400HXL, G700HXL One each in series (Toyo Soda Co., Ltd.) Solvent: THF flow velocity; 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 and measured at 60 ° C. using an Ostwald viscometer.

The thermal decomposition rate of oxymethylene copolymer Kx; Kx means the decomposition rate when left to stand at x ° C. for a certain period of time.
It was left at x ° C. and calculated by the following formula.

Kx = (W ₀ −W ₁ ) / W ₀ × 100% W ₀ ; sample weight for heating W ₁ ; 〃 after 〃 The thermal balance device used was a thermal analyzer 1090/1091 manufactured by Du Ponh.

Oxymethylene copolymer melting point (Tm), crystallization temperature (T
c); Using a differential scanning calorimeter, under nitrogen atmosphere, 10 ℃ / min
After 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 under-crystal temperature (Tc) was measured. Differential scanning calorimeter
A thermal analyzer 1090/1091 manufactured by Du Pont was used.

Mechanical Properties of Oxymethylene Copolymer; Tensile test pieces and Izod impact test pieces are injection molded by setting the silliwada temperature to 230 ℃, mold temperature to 60 ℃ and molding cycle to 50 seconds using an injection molding machine with an injection capacity of 5 ounces. 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 1-5, Comparative Example 1 642.0 g of 1,3-dioxane was added to a mixed solution of 2.30 g of boron trifluoride / diether etherate and 88.0 g of benzene, and the mixture was stirred while keeping the internal temperature at 20 ° C. did. After a predetermined time, GPC
The number average molecular weight of the prepolymer was measured by analysis.

Further, 112 g of the prepolymer thus prepared and 3,000 g of trioxane were put into a 3 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 whitened powder.
The relative viscosity ηr, melting point Tm and crystallization temperature Tc of this polymer powder were measured. The results are summarized in Table 1.

Further, 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, 1,3-dioxolane and trioxane were simultaneously charged into 3 kneaders. I went. 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 was increased in 3 minutes and the yield was also high. 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 8 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 when the prepolymer 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 is no great change in the physical properties such as melting point and crystallization temperature.

Examples 9 to 11 The procedure of Example 3 was repeated except that the solvent for the prepolymer 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.

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 shown in Table 4.

When 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 12 to 14 and Comparative Example 3 The same as Example 3 except that a di (n-butyl) ether complex, a phenol complex and a diphenyl sulfide complex were used as the catalyst instead of the boron trifluoride / diether ether complex. went. 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 apparent 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 polymerization degree and yield of the finally obtained oxymethylene copolymer are both low.

0.27 parts by weight of bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and 100 parts by weight of the polymers obtained in Examples 1 to 14 and 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 melt-kneaded at 210 ° C. for 10 minutes in a mixer having two roller type blades.

Thereafter, 0.10 part by weight of dicyandiamide was further added, and the mixture was kneaded for 5 minutes. The obtained polymer was crushed and injection-molded, and the mechanical properties and heat 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; 63MPa Tensile rupture elongation; 64% Izod impact value; 6.6kgcm / cm (1/2 notch) Thermal decomposition rate; K240 (60min) = 3.1% Comparative Example 4 Instead of the active copolymer, Polymerization of trioxane was performed using the synthesized and isolated poly (oxymethylene / oxyethylene) as a copolymerization component.

Poly (oxymethylene / oxymeelene) was isolated as follows.

642.0 g of 1,3-dioxolane was added to a mixed solution of 2.30 g of boron trifluoride / diether etherate and 88.0 g of benzene, and the mixture was stirred while keeping the internal temperature at 20 ° C. After 4 hours, the solution became very viscous and the contents were invisible when the container was turned upside down. When the number average molecular weight was measured in this state, it was about 25,000. The reaction product was scraped into a 10% aqueous solution of triethylamine and then heated to 50 ° C. to 1
Stir vigorously for hours. Then, the polymer was extracted with chloroform, and the extract was dried over anhydrous magnesium sulfate.
The extract was subjected to vacuum decompression, the residue was poured into a metal vat, and left standing overnight to obtain a white solid. ¹ H of this solid
When NMR (solvent; p-chlorophenol / C ₆ D ₆ , 270 MHz) was measured, absorptions close to singlets were found at 3.69 ppm and 470 ppm, and the ratio of integrated values was 2: 1. From this, it is clear that the target poly (oxymethylene / oxyethylene).

96 g of poly (oxymethylene / oxyethylene) thus prepared, 3000 g of trioxane, and a mixed solution of boron trifluoride / diethyl etherate 0.3 ml / benzene 15 ml were heated to 80 ° C. Having 3
It was put into a kneader and stirred at 50 rpm. After about 3 minutes, the contents began to solidify, gradually became a lump, and were further pulverized into a powder. Stirring was stopped 10 minutes after the start of the reaction, and the relative viscosity ηr, melting point Ta and crystallization temperature Tc of the polymer powder were measured.

In addition to increasing the polymerization time as compared to the examples of the present invention,
The degree of polymerization and the polymerization yield are also low. Further, since the copolymerization component enters the block form, the melting point becomes high.

Example 15 25 kg / h trioxane from a raw material supply port provided at one end of a twin-screw mixer having an inner diameter D of 100 mm and L / D = 10 and a prepolymerization prepared in the same manner as in Example 1 Solution 0.93
kg / h was supplied and polymerization was performed inside the twin-screw mixer, and a white powdery oxymethylene copolymer was obtained from the 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.Both shafts mix the inner wall or the other shaft during mixing. 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 was set to 175 rpm, and the average residence time at this time was 3 minutes.
The powdery polymer obtained from the discharge port was 25.9 kg / h. When a part of the polymer was taken and the polymerization yield was measured, it was 98
%Met.

0.27 parts by weight of bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 100 parts by weight of the polymer thus obtained, and 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 biaxial mixer is provided with a vent port at 5D to 8D from the supply port to 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 biaxial mixer is provided 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. 22.5 kg of melt-stabilized polymer as pellets
/ H. Add 0.1 parts by weight of dicyandiamide to 100 parts by weight of these pellets, and use a twin-screw extruder.
Melt kneading was performed at 190 ° C.

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; 65MPa Tensile rupture elongation; 67% Izod impact value; 6.8kgcm / cm (1/2 notch) Thermal decomposition rate; K240 (60min) = 3.0% It is understood that it shows a very good value. .

<Effects of the Invention> By using the production method of the present invention, a polymer having a high degree of polymerization can be obtained within an extremely short time, so that the production process can be greatly 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.

Claims (5)

[Claims] 1. At least one polymerization catalyst selected from the group consisting of boron trifluoride hydrate and a coordination compound of boron trifluoride with an organic compound containing an oxygen atom or a sulfur atom, and 1,3-dioxolane. The method is characterized in that a poly (oxymethylene / oxyethylene) active copolymer solution having a number average molecular weight of 150 to 20,000 is prepared by prepolymerization in the presence of an organic solvent, and the active copolymer solution is contacted with trioxane. Method for producing oxymethylene copolymer. 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 -30 to 150 ° C. 4. An active copolymer solution obtained by prepolymerization
The method according to claim 1, wherein the reaction is carried out 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.