JPS6221366B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyoxymethylene. Specifically, the present invention relates to an industrially advantageous method for producing polyoxymethylene having a high degree of polymerization and good thermal stability from formaldehyde. Polyoxymethylene has many uses as an engineering plastic due to its excellent mechanical properties. However, polymers obtained by polymerizing formaldehyde using well-known catalysts have poor thermal stability and cannot be used as they are. For this reason, thermal stability is improved by esterifying or etherifying the terminal hydroxyl group of the polymer. In the method of improving thermal stability by such terminal group treatment, it is necessary to provide a complicated processing step that consumes a large amount of energy after polymerization, and it cannot be said to be an economically advantageous method. In view of this point, the present inventors conducted extensive research and found that
If formaldehyde is polymerized using a specific aluminum compound as a catalyst, and a peroxide compound or Lewis acid is added to the resulting polyoxymethylene and heat-treated, polyoxymethylene with good thermal stability and a degree of polymerization that can be molded can be obtained. This discovery led to the present invention. That is, the gist of the present invention is as follows: (a) General formula [] (R ¹ O) _l AlR ² _3-l ... [] (In the formula, R ¹ and R ² represent an alkyl group, and l
indicates either 0, 1, 2, or 3. ), (b) an oxygen or nitrogen atom selected from diketones, aromatic aldehydes or ketones having a hydroxyl group at the ortho position, substituted products thereof, quinolines, or salicylic acids as a donor; In the presence of a chelate compound coordinated with a compound capable of coordination, or to the chelate compound, (c) a phosphorus-containing compound selected from amines, phosphines, phosphites, phosphates, and phosphin oxides; The present invention relates to a method for producing polyoxymethylene, which comprises adding a peroxide compound or a Lewis acid to polyoxymethylene obtained by polymerizing formaldehyde in the presence of a catalyst obtained by contact with the polyoxymethylene, and heating the mixture. To explain the present invention in more detail below, the formaldehyde used as a raw material in the present invention may be either gaseous or liquid, but as in the well-known polymerization method using a catalyst, the water content is 1% by weight or less, particularly 0.1%.
Needless to say, it is substantially anhydrous formaldehyde of less than % by weight. Such substantially anhydrous formaldehyde can be produced by, for example, pyrolyzing paraformaldehyde in a high boiling medium such as liquid paraffin or phthalic anhydride, and then filling the resulting formaldehyde gas with a dehydrating adsorbent such as an ion exchange resin. Obtained by passing it through a column.
Of course, mixtures of formaldehyde and small amounts of comonomers, such as ethylene oxide, can also be used as raw materials. In the present invention, the polymerization of formaldehyde is carried out using an aluminum compound represented by the general formula [].
The presence of a chelate compound of (a) and a coordinating compound (b) having an oxygen atom or nitrogen atom as a donor, or the presence of a catalyst obtained by contacting the chelate compound with a phosphorus-containing compound or amines c. It is necessary to carry out the following steps. Aluminum compound a used as one of the raw materials for the catalyst is represented by the following general formula. (R ¹ O) _l AlR ² _3-l ...[] (In the formula, R ¹ and R ² represent an alkyl group, particularly a lower alkyl group, and 1 represents any one of 0, 1, 2, and 3. ) Various well-known compounds can be used as long as they are represented by the general formula [], but specifically, l=0...triethylaluminum, triisobutylaluminum, tri-n-propylaluminum, tri- n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum,
Trialkylaluminium such as tri-n-decylaluminum l=1...monoethoxyaluminum diethyl, monoethoxyaluminum diisobutyl,
Monoethoxyaluminum diisopropyl, monoisobutoxyaluminum diisobutyl, diethylaluminium acetylacetonate, mono-n-propoxyaluminum di-n-propyl l=2...diethoxyaluminum monoisobutyl, diisobutoxyaluminum monoisobutyl, di-n-propoxyaluminum Mono-n-propyl l=3...Triethoxyaluminum, triisopropoxyaluminum, trioctyloxyaluminum, etc. are mentioned. Among these, triethylaluminum or triisopropoxyaluminum is preferred. Further, as the compound b capable of coordination using an oxygen atom or a nitrogen atom as a donor, which is a raw material of the catalyst, there can be mentioned various well-known compounds that form a chelate compound by coordinating with aluminum. Specifically, for example, diketones such as acetylacetone, benzoylacetone, and hexafluoroacetylacetone; aromatic aldehydes or ketones having a hydroxyl group in the ortho position, such as salicylaldehyde, O-hydroxyacetophenone, and 5-chlorosalicylaldehyde, or substituted thereof; Substituted quinolines such as 8-hydroxyquinoline and 2-methyl-8-hydroxyquinoline; salicylic acids such as salicylic acid, 3-phenylsalicylic acid, and 5-chlorosalicylic acid. Among them, salicylic acids are particularly preferred. In addition, various well-known phosphorus-containing compounds or amines (c) to be brought into contact with the chelate compound of the aluminum compound (a) and the compound (b) capable of coordination with an oxygen atom or nitrogen atom as a donor may be used in some cases. Both can be used. The phosphorus-containing compound is selected from phosphines, phosphites, phosphates, and phosphin oxides. Specifically, phosphins such as triphenylphosphin, tri-n-butylphosphin, and triethylphosphin; triphenylphosphite, tri-n-
Phosphites such as butyl phosphite, trisnonylphenyl phosphite, tristearylphosphite; phosphates such as trimethyl phosphate and triphenyl phosphite; tri-n-butyl phosphin oxide, triphenyl phosphin oxide, etc. Examples include phosphin oxides and hexamethyl phosphor triamide. Among these, triphenylphosphin, triphenylphosphite, tristearylphosphite, triphenylphosphate, tri-n-
Butyl phosphite and tri-n-butyl phosphite are preferred. In addition, examples of amines include 1,8-diazabicyclo(5,4,0)undecene-7, bipyridyl,
Examples include pyridine, ethylenediamine, propylene diamine, tri-n-butylamine, and stearylamine, with 1,8-diazabicyclo(5,4,0)undecene-7 being particularly preferred. The phosphorus-containing compound and amines can be used together. The catalyst can be manufactured according to conventional methods. For example, an aluminum compound (a) and a compound (b) that can coordinate 1 to 2 times as much as the aluminum compound (a),
It can be easily produced by mixing and contacting in a hydrocarbon solvent such as n-hexane, n-heptane, benzene, or toluene or an ether solvent such as ethyl ether or tetrahydrofuran at a temperature of room temperature to 250°C. At that time, the compound (b) capable of coordination is added to 2
It may be used as a mixture of more than one species. It is also possible, if desired, to react the aluminum compound (a) with one of the coordinating compounds (b) and then to further react the reaction product with another coordinating compound. When producing a catalyst by further contacting the reaction product thus prepared with a phosphorus-containing compound or amines, the phosphorus-containing compound or amines are added and then mixed and contacted at a temperature of room temperature to 200°C. Therefore, it can be easily manufactured. After distilling off the solvent from the catalyst thus obtained, if necessary,
Heat treatment may be performed at a temperature of 50°C, particularly 80°C or higher. The amount of phosphorus-containing compound or amine added to the reaction product varies depending on the type, but is usually 0.05 to 10% of the amount of phosphorus compound or amine added to the aluminum compound in the reaction product.
It is selected from the range of 0.1 to 3 times the mole, especially 0.1 to 3 times the mole. For example, in the case of tristearylphosphite
0.25 to 3 times the mole, 1,8-diazabicyclo(5,
In the case of 4,0) undecene-7, it is used in a range of 0.1 to 0.5 times the mole. The amount of catalyst used can be selected arbitrarily.
Usually, as an aluminum compound, the amount is 0.1 to 10 -8 mol per volume of the liquid medium in the case of polymerization using a liquid medium, and 0.1 to 10 ^-8 mol per volume of the polymerization vessel in the case of gas phase polymerization.
1, preferably 10 ^-4 to 10 ^-7 mol/l. Various polymerization methods are known, but
Either of them can be adopted. For example, formaldehyde is dissolved in an inert solvent and polymerized by adding a catalyst to this solution, or a slurry polymerization method in which formaldehyde gas is continuously introduced into an inert solvent in which a catalyst is dispersed, and polymerization is performed by dispersing it in a medium. A gas phase polymerization method or the like is employed in which the catalyst is supplied to a polymerization vessel, the medium is then distilled off, and formaldehyde gas is supplied while stirring the catalyst for polymerization. Inert solvents used in the slurry polymerization method include aliphatic hydrocarbons such as pentane, hexane, heptane, and octane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, and aromatic hydrocarbons such as benzene, toluene, and xylene. can be mentioned. Of course, these inert solvents can also be used as a medium for dispersing the catalyst, so it is preferable to disperse the catalyst in these solvents and then supply them to the polymerization vessel. Polymerization is -
In the temperature range of 40 to 80℃, especially 0 to 40℃, normal pressure to
It is carried out under a pressure of 10 atmospheres, especially normal pressure to 4 atmospheres. In the present invention, it is necessary to add a peroxide compound or a Lewis acid to the polyoxymethylene thus obtained and heat-treat the polyoxymethylene. The thermal stability of the polyoxymethylene to be heat-treated is preferably 85% or more based on R ₆₀ described below. If it is less than this value, the polymer yield after heat-treating the polyoxytylene may decrease, resulting in poor economic efficiency. Peroxide compounds added to polyoxymethylene during heat treatment include various well-known organic peroxides, but suitable peroxides have a half-life and a decomposition temperature of 1 minute.
It is a compound having a temperature of 150°C or higher, particularly preferably 160°C to 260°C. Such compounds include;
t-Butyl hydroperoxide, kyumene hydroperoxide, 2,5-dimethylhexane 2,5-dihydroperoxide, 1,1,3,3
Tetramethylbutyl hydroperoxide, 2,
5-dimethyl 2,5-di(t-butylperoxy)hexyne-3, p-menthane hydroperoxide, di-t-butyl peroxide, diisopropylbenzene hydroperoxide, t-butylcumyl peroxide, 2,5 -dimethyl-2,
5 di(t-butylperoxy)hexane, dicumyl peroxide, α,α′-bis(t-butylperoxyisopropyl)benzene, methyl ethyl ketone peroxide, di t-butyl diperoxyisophthalate, n-butyl 4 , 4bis(t-butylperoxy)valerate, t-butylperoxybenzoate, 2,2-bis(t-butylperoxy)butane, t-butylperoxyacetate, 2,5dimethyl 2,5-di( benzoylperoxy)hexane, t-butylperoxyisopropyl carbonate, cyclohexanone peroxide, t-butylperoxy 3,5,5 trimethylhexanoate, t-butylperoxylaurate, t-butylperoxymale acid , 1,1-bis(t-butylperoxy)cyclohexane, among which more preferable peroxides include cumene hydroperoxide, 1,1,3,3 tetramethylbutyl hydroperoxide, and p-menthane hydroperoxide. Peroxide, diisopropylbenzene hydroperoxide, α,α'bis(t-butylperoxyisopropyl)benzene. Various well-known Lewis acids can be mentioned, but suitable Lewis acids include boron trifluoride etherate, aluminum chloride, aluminum bromide, aluminum iodide, boron trichloride, boron tribromide, and triiodide. Boron, stannous chloride, stannic chloride, ferrous chloride, ferric chloride, gallium trichloride, indium trichloride, bismuth trichloride, silicon tetrachloride, phosphorus trichloride, phosphorus pentachloride, zinc chloride, Antimony chloride, antimony pentachloride, and the most preferred Lewis acid is boron trifluoride etherate. The amount of these peroxide compounds or Lewis acids added varies depending on the type of catalyst used for polymerization, but is 10 ^-9 mol to 1 g of polyoxymethylene.
In the range of 10 ^-3 mol, preferably from 10 ^-8 mol
It is in the range of 10 ⁻⁵ mol. A peroxide compound and a Lewis acid can also be used in combination. In the present invention, these compounds can be added to the solvent in the case of slurry polymerization, or after the solvent has been separated, they can be added directly to the resulting wet cake, or if necessary, after washing and drying, or during the heat treatment. Although possible, adding directly to the wet cake is preferred. In the case of gas phase polymerization, a peroxide solution may be sprinkled onto the polymer powder. The heat treatment is usually carried out under an inert gas atmosphere such as nitrogen gas or argon gas, under reduced pressure, or under pressure, and in the case of peroxide compounds, at a temperature of 150°C to 265°C, preferably from the melting point of polyoxymethylene to 255°C.
Temperatures in the range of °C, for Lewis acids, 30-260 °C
Preferably, the temperature is 40 to 100°C. The treatment time is 5 minutes to 120 minutes when the temperature is below the melting point of the polymer, and 10 seconds to 30 minutes when the temperature is above the melting point of polyoxymethylene.
Although the polymerization conditions and heat treatment temperature are appropriately selected, the object of the present invention can be achieved even with a time that is long enough to pass through an extruder. Suitable equipment for carrying out such heat treatment is a reaction tank if the heat treatment is carried out in a solvent at a temperature between 150°C and the melting point of polyoxymethylene, and a fluidized bed if the heat treatment is carried out after drying. I can do it. When carrying out the melting at a temperature higher than the melting point of polyoxymethylene, a single-screw, twin-screw or multi-screw extruder having a vent port, a kneader type heating melting device, or a device having a mechanism similar to these devices can be used. In the method of the present invention, heat treatment can be carried out before or after the treatment with a peroxide compound or Lewis acid, that is, in the absence of additives, if necessary. The present invention has been explained in detail above, but in the present invention, polyoxymethylene is produced by a specific method, and then a peroxide compound or a Lewis acid is added to the polyoxymethylene, followed by heat treatment. , polyoxymethylene with high molecular weight and good thermal stability can be produced. Therefore, it is an industrially extremely advantageous method. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, in this invention, _R60 (weight%) is the value calculated|required as follows. 222℃ using a thermobalance
It was determined by heating polyoxymethylene for 60 minutes (in a nitrogen atmosphere), measuring its weight, and calculating the weight residual ratio relative to the weight before heating. In the examples, the viscosity of polyoxymethylene (η
sp/C) is obtained by dissolving acetylated polyoxymethylene in p-chlorophenol containing 2% α-pinene at 130°C for 5 minutes, and heating the resulting 0.5% by weight solution at 60°C using an Ubbelohde viscometer. Obtained by measuring. The stabilized polymer yield after heat treatment was determined from the following formula. Stabilized polymer yield (wt%) = Polymer weight after treatment / Polymer weight before treatment x 100 Catalyst production examples 1 to 7 Aluminum compound (a) of the type and amount shown in Table 1 in a four-necked glass flask. The coordinating compound (b) and a solvent were charged. This was reacted with stirring under the conditions shown in Table 1. Next, phosphorus-containing compounds or amines of the type and amount shown in Table 2 were added to the reaction product, and the mixture was stirred and mixed at 25° C. for 2 hours in the solvent shown in Table 2. After distilling off the solvent, the mixture was heated under the conditions shown in Table 2 to produce a catalyst.

【table】

[Table] Catalyst Production Examples 8 to 14 A four-neck flask was charged with an aluminum compound (a), a coordinating compound (b), and a solvent in the types and amounts shown in Table 3. This was reacted with stirring under the conditions shown in Table 3 to produce a catalyst.

【table】

[Table] Examples 1 to 17 700ml of hexane in the four-necked glass flask from 1.
Then, the types and amounts of catalysts shown in Table 4 were charged.
Paraformaldehyde is suspended in liquid paraffin, and substantially anhydrous formaldehyde gas obtained by thermal decomposition at 120 to 130°C is continuously blown into this at a rate of 0.5 g/min with nitrogen as a carrier gas, as shown in Table 4. Polymerization was carried out under the polymerization conditions shown below.
As a result, polyoxymethylene was obtained in the amount shown in Table 4. The catalytic efficiency and thermal stability (R ₆₀ ) of this polyoxymethylene are also shown in Table 4. Next, 3 g of dried polyoxymethylene was charged into a 200 ml four-necked glass flask along with 100 ml of acetic anhydride and 0.05 g of sodium acetate, reacted at 139°C for 1.5 hours, thoroughly washed with acetone and water, and dried under reduced pressure overnight. I did this. Table 4 shows the ηsp/C of the polyoxymethylene thus obtained. A small kneader was charged with 10 g of powdered polyoxymethylene obtained by polymerization and a peroxide compound of the type and amount shown in Table 4, and heated and melted under the conditions shown in Table 4. The stabilized polymer yield, thermal stability (R ₆₀ ) and ηsp/C of the polyoxymethylene after treatment are also shown in Table 4.

【table】

[Table] Examples 18-31 700ml of hexane in the four-necked glass flask from 1.
Then, the types and amounts of catalysts shown in Table 5 were charged.
Paraformaldehyde was suspended in liquid paraffin, and substantially anhydrous formaldehyde gas obtained by thermal decomposition at 120 to 130°C was continuously blown into this at a rate of 0.5 g/min with nitrogen as a carrier gas, as shown in Table 5. Polymerization was carried out under the polymerization conditions shown below.
As a result, polyoxymethylene was obtained in the amount shown in Table 5. The catalytic efficiency and thermal stability (R ₆₀ ) of this polyoxymethylene are also shown in Table 5. Next, 3 g of dried polyoxymethylene was charged into a 200 ml four-necked glass flask along with 100 ml of acetic anhydride and 0.05 g of sodium acetate, reacted at 139°C for 1.5 hours, thoroughly washed with acetone and water, and dried under reduced pressure overnight. I did this. Table 5 shows the ηsp/C of the polyoxymethylene thus obtained. Powdered polyoxymethylene 2 obtained by polymerization
30 ml of n-hexane as a solvent and a Lewis acid of the type and amount shown in Table 5 were charged, and heat treatment was performed under the conditions shown in Table 5. The stabilized polymer yield, thermal properties (R ₆₀ ) and ηsp/C of polyoxymethylene after treatment are also shown in Table 5.

【table】

Claims (1)

[Claims] 1 (a) General formula [] (R ¹ O) _l AlR ² _3-l ... [] (In the formula, R ¹ and R ² represent an alkyl group, and l
indicates either 0, 1, 2, or 3. ), (b) an oxygen or nitrogen atom selected from diketones, aromatic aldehydes or ketones having a hydroxyl group at the ortho position, substituted products thereof, quinolines, or salicylic acids as a donor; In the presence of a chelate compound coordinated with a compound capable of coordination, or to the chelate compound, (c) a phosphorus-containing compound selected from amines, phosphines, phosphites, phosphates, and phosphin oxides; A method for producing polyoxymethylene, which comprises adding a peroxide compound or a Lewis acid to polyoxymethylene obtained by polymerizing formaldehyde in the presence of a catalyst obtained by contacting the polyoxymethylene, and heating the mixture. 2 (a) General formula [] (R ¹ O) _l AlR ² _3-l ... [] (In the formula, R ¹ and R ² represent an alkyl group, and l
indicates either 0, 1, 2, or 3. ), (b) an oxygen or nitrogen atom selected from diketones, aromatic aldehydes or ketones having a hydroxyl group at the ortho position, substituted products thereof, quinolines, or salicylic acids as a donor; The presence of a catalyst obtained by contacting a chelate compound coordinated with a compound capable of coordination with (c) an amine or a phosphorus-containing compound selected from phosphines, phosphites, phosphates, and phosphin oxides; 2. The method for producing polyoxymethylene according to claim 1, which comprises adding a peroxide compound or a Lewis acid to polyoxymethylene obtained by polymerizing formaldehyde and heating the mixture. 3 (b) The method for producing polyoxymethylene according to claim 1 or 2, characterized in that salicylic acids are used as the compound capable of coordination with an oxygen atom or a nitrogen atom as a donor. .