JP2017110073A - Manufacturing method of polyacetal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of polyacetal with improved operability, while maintaining miscibility with an additive, by improving a drying method.SOLUTION: A manufacturing method of polyacetal includes: a first-stage heat-drying step of heating polyacetal in a range of 130°C ± 10°C; and a second-stage heat-drying step of heating, if the melting point of the polyacetal is Tm, the polyacetal obtained at the first-stage heat-drying step, within a temperature range of Tm-20°C or higher and Tm or lower.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing polyacetal.

  Polyacetal is an engineering plastic that is used in a wide range of fields including electrical and electronic materials, automobiles, and various industrial materials because it has excellent mechanical properties and moldability. In particular, in recent years, demands in harsh environments indoors and vehicle interiors have increased, and there is a need for a production method that can efficiently obtain polyacetal having high thermal stability. In general, polyacetal contains particles with a remarkably small particle size, and these small particles cause transportation failure due to scattering or clogging when transporting inside the piping, which is a cause of decreasing production stability. ing. In order to solve these problems and further improve production stability, a method for producing polyacetal having excellent handleability and high thermal stability is required.

  In the polyacetal, as a method for improving the thermal stability, for example, in the deactivation step of the polymerization catalyst, the polyacetal is pulverized and pulverized to improve the deactivation efficiency of the polymerization catalyst, thereby improving the thermal stability. (For example, refer to Patent Documents 1 and 2). Further, as another method, there is a method for producing polyacetal in which the polyacetal immediately after polymerization is pulverized and then dried in a nitrogen atmosphere to improve the thermal stability by increasing the drying efficiency (see, for example, Patent Document 3). .

JP 58-34819 A JP-A-57-80414 JP-A-7-228649

  However, when the above-described method is used, there may be a problem that the polyacetal is pulverized to improve the thermal stability, while the fine powder increases, so that the handleability after drying is significantly reduced. For example, when the polyacetal after drying contains more than 15% of fine powder having a major axis of 50 μm or less, there is a possibility of causing transportation failure due to clogging of the transportation piping to the subsequent process or adhesion to the piping wall surface. Polyacetal with good handleability needs to reduce such fine powder, but it is very difficult to reduce fine powder in the above-mentioned process.

  On the other hand, when polyacetal contains a lot of large particles, the handleability during transportation of piping is improved, while thermal stability is impaired due to lack of washing and drying, and miscibility when blended with additives. When melted and kneaded with an additive in an extruder, the meltability deteriorates due to the large particle size, which may cause kneading failure. For example, in melt-kneading with an additive in an extruder, when the major axis contains 20% or more of large grains having a major axis of 300 μm or more, the dispersibility of the additive in the obtained pellet is significantly deteriorated, and the effect of the additive is biased May occur.

  Therefore, the present invention reduces the amount of fine powder during transportation of piping after drying while maintaining thermal stability, improves handling, and is a polyacetal that can be finely re-pulverized when blended with additives. An object is to provide a manufacturing method.

  As a result of diligent research on the above problems, the present inventors have produced polyacetal by a production method that undergoes a specific heat drying step, and thus have high thermal stability, excellent handling properties, and addition At the time of blending with an agent, it was found that a polyacetal capable of maintaining miscibility with additives and the like can be obtained by re-pulverizing again, and the present invention has been completed.

That is, the present invention is as follows.
[1]
A first-stage heating and drying step of heating polyacetal in a range of 130 ° C. ± 10 ° C .;
A second-stage heat-drying step of heating the polyacetal obtained in the first-stage heat-drying step at a temperature in the range of Tm-20 ° C. or higher and Tm or lower when the melting point of the polyacetal is Tm. Method.
[2]
The method for producing polyacetal according to [1], wherein a light agglomerate of polyacetal is formed in the second-stage heat drying step.
[3]
The polyacetal production method according to [1] or [2], wherein the polyacetal obtained in the second-stage heat drying step is a light agglomerate satisfying the following (1) and (2):
(1) The proportion of particles having a major axis of 50 μm or less is 15% or less with respect to all particles,
(2) The ratio of particles having a major axis of 300 μm or more is 20% or more with respect to all particles.
[4]
[1] to [3], wherein the heating time of the first stage heating and drying step is in the range of 30 minutes to 500 minutes after the product temperature of the polyacetal reaches the drying temperature of the first stage heating and drying step. Of producing polyacetal.
[5]
The heating time of the second stage heating and drying process is in the range of 20 minutes to 500 minutes after the product temperature of the polyacetal reaches the drying temperature of the second stage heating and drying process described above. In the second stage heating and drying process, the polyacetal The method for producing a polyacetal according to any one of [1] to [4], wherein drying is performed while stirring.
[6]
The polyacetal is a polyacetal obtained by copolymerizing a formaldehyde monomer or cyclic formaldehyde and a cyclic ether and / or cyclic formal in the presence of an initiator, according to any one of [1] to [5]. Production method of polyacetal.
[7]
The method for producing a polyacetal according to any one of [1] to [6], wherein the polyacetal is a polyacetal obtained by copolymerizing trioxane and a cyclic ether and / or cyclic formal in the presence of an initiator.
[8]
The method for producing a polyacetal according to [6] or [7], wherein the cyclic ether and / or the cyclic formal is 1,3-dioxolane.
[9]
The method for producing a polyacetal according to any one of [1] to [8], wherein the amount of unreacted cyclic formaldehyde remaining in the polyacetal obtained through the first stage heat drying step is 10,000 ppm or less.
[10]
The ratio of particles having a major axis of 50 μm or less is 15% or less with respect to all particles, and the ratio of particles having a major axis of 300 μm or more is 20% or more with respect to all particles,
When mixing with a vortex mixer at a rotational speed of 3000 rpm for 15 minutes, the proportion of fine particles having a major axis of 50 μm or less (fine powder amount) exceeds 15% of the total particles, and the proportion of particles having a major axis of 300 μm or more ( A polyacetal light agglomerate having a large particle amount) of less than 20% based on all particles.
[11]
A first-stage heating and drying step of heating polyacetal in a range of 130 ° C. ± 10 ° C .;
When the melting point of the polyacetal is Tm, a second-stage heat-drying step of heating the polyacetal obtained in the first-step heat-drying step at a temperature in the range of Tm-20 ° C. or higher and Tm or lower;
And a step of melt-kneading the polyacetal obtained in the second-stage heat-drying step and the additive, and a method for producing a polyacetal resin composition.

  According to the method for producing a polyacetal of the present invention, a polyacetal having high thermal stability and improved handling properties without losing the miscibility with the additive by re-pulverizing when blended with the additive. Can be manufactured.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and the present invention is not limited to the following contents. The present invention can be implemented with various modifications within the scope of the gist.

≪Polyacetal production process≫
The method for producing the polyacetal of this embodiment is as follows:
A first-stage heating and drying step of heating polyacetal in a range of 130 ° C. ± 10 ° C .;
A second-stage heating and drying step of heating the polyacetal obtained in the first-stage heating and drying step at a temperature in the range of Tm−20 ° C. to Tm when the melting point of the polyacetal is Tm.

<Polyacetal>
The polyacetal used in the first stage heat drying step is not particularly limited. For example, formaldehyde monomer or cyclic formaldehyde such as trimer (trioxane) or tetramer (tetraoxane), ethylene oxide, propylene oxide, epichlorohydrin. , 1,3-dioxolane, 1,4-butanediol formal, and / or the like, and / or cyclic formal are copolymerized.
The polyacetal used in the first stage heat drying step is preferably a polyacetal obtained by copolymerizing a formaldehyde monomer or cyclic formaldehyde and a cyclic ether and / or cyclic formal in the presence of an initiator, and trioxane, It is more preferable that it is a polyacetal obtained by copolymerizing cyclic ether and / or cyclic formal in the presence of an initiator. The cyclic ether and / or cyclic formal is preferably 1,3-dioxolane. When the polyacetal thus obtained is used, the thermal stability tends to be improved.

<Cyclic ether and cyclic formal>
When the polyacetal is obtained using a trimer of formaldehyde (trioxane), the amount of the comonomer added is generally preferably 0.1 to 60 mol%, more preferably 0.1 to 100 mol of trioxane. 1 to 20 mol%, more preferably 0.13 to 10 mol%.
When the polyacetal is obtained using a formaldehyde tetramer (tetraoxane), the amount of the comonomer added is preferably 0.13 to 90 mol%, more preferably 0.14, based on 100 mol of tetraoxane. -30 mol%, more preferably 0.16-13 mol%.

  The polyacetal is not particularly limited. For example, a formaldehyde monomer or cyclic formaldehyde such as a trimer (trioxane) or tetramer (tetraoxane), and the above-described comonomers are used in a predetermined polymerization catalyst. Can be produced by copolymerization.

  The polyacetal used in the present embodiment is preferably a polyacetal having a melting point of 160 ° C. or higher and 173 ° C. or lower. When a polyacetal having a melting point in the above range is used, the thermal stability tends to be good.

  In the present embodiment, the melting point of polyacetal is melted by once heating 3 mg of the sample to 200 ° C. at a heating rate of 300 ° C./min using a differential thermal scanning calorimeter (trade name “DSC8000”, manufactured by PerkinElmer). After cooling, the temperature is lowered to 100 ° C. at a temperature lowering rate of 80 ° C./min, the temperature is raised again at a temperature rising rate of 2.5 ° C./min, the temperature at the top of the endothermic peak is measured, and the value is taken as the melting point.

<Polymerization catalyst (initiator)>
As the polymerization catalyst (initiator) used for the polymerization of polyacetal, a cationically active catalyst such as Lewis acid, proton acid and ester or anhydride thereof is preferable.

  Examples of Lewis acids include, but are not limited to, boric acid, tin, titanium, phosphorus, arsenic, and antimony halides, and more specifically, boron trifluoride, tin tetrachloride. , Titanium tetrachloride, phosphorus pentafluoride, phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof.

  In addition, the protonic acid and its ester or anhydride are not limited to the following, but examples include perchloric acid, trifluoromethanesulfonic acid, perchloric acid tertiary butyl ester, acetyl perchlorate, and trimethyloxonium hexa Fluorophosphate is mentioned.

  Among the above polymerization catalysts, from the viewpoint of polymerization reaction control, boron trifluoride, boron trifluoride hydrate, and a coordination complex compound of boron trifluoride with an organic compound containing an oxygen atom or a sulfur atom are preferable, Specific examples include boron trifluoride diethyl ether and boron trifluoride-n-butyl ether.

The addition amount of the polymerization catalyst is 0.1 × 10 ^{−5 to} 0.1 × 10 ⁻³ mol per 1 mol of cyclic formaldehyde (eg, trioxane) when polyacetal is obtained using cyclic formaldehyde (eg, trioxane). The range is preferable, more preferably in the range of 0.3 × 10 ^{−5 to} 0.5 × 10 ⁻⁴ mol, still more preferably in the range of 0.5 × 10 ^{−5 to} 0.4 × 10 ⁻⁴ mol. is there. When the addition amount of the polymerization catalyst is within the above range, it is possible to carry out the polymerization reaction stably for a long time while reducing the amount of scale generated in the supply section of the polymerization reactor.

<Low molecular weight acetal compound>
The low molecular weight acetal compound functions as a chain transfer agent in the polymerization step to be described later, and is not limited to the following, and examples thereof include acetal compounds having a molecular weight of 200 or less, preferably 60 to 170. Specific examples include methylal, methoxymethylal, dimethoxymethylal, and trimethoxymethylal. These may be used alone or in combination of two or more.

From the viewpoint of controlling the molecular weight of the polyacetal to a suitable range, when the polyacetal is obtained using cyclic formaldehyde (for example, trioxane), the low molecular weight acetal compound is added in an amount of 0.1% to 1 mol of cyclic formaldehyde (for example, trioxane). The range is preferably 1 × 10 ^{−4 to} 0.6 × 10 ⁻² mol. When the molecular weight of the polyacetal is substituted with the melt flow rate (MFR value) and expressed, it is preferable to adjust the addition amount of the low molecular weight acetal compound so that the MFR value becomes a molecular weight corresponding to 0.1 to 100 g / 10 min. .

<Polymerization reaction process>
Polyacetal can be obtained by a conventionally known method, for example, U.S. Pat. Nos. 3,027,352, 3,803,094, German Patents 1,161,421, 1,495,228, 1,720,358, Polymerization can be carried out by the methods described in Japanese Patent No. 3018898, JP-A-58-98322 and JP-A-7-70267.

  The polymerization method of polyacetal is not particularly limited, and any of slurry polymerization, bulk polymerization, and melt polymerization can be employed.

  The shape and structure of the polymerization reactor to be used are not particularly limited, but a biaxial paddle type or screw type stirring and mixing type polymerization apparatus capable of passing a heat medium through the jacket is preferably used.

<Polymerization catalyst deactivation step>
Examples of the deactivation treatment of the polymerization catalyst include, but are not limited to, amines such as ammonia, triethylamine, tri-n-butylamine, alkali metal or alkaline earth metal hydroxides, inorganic salts, Examples thereof include a method of neutralizing and deactivating the polymerization catalyst in an aqueous solution such as an organic acid salt or an organic solution. From the viewpoint of increasing the deactivation efficiency of the polymerization catalyst, when the polyacetal is a large lump, it is preferable to pulverize and process it once. Then, polyacetal is obtained by filtering with a centrifuge.

<First stage heat drying process>
In the first-stage heating and drying step, the polyacetal particle size is preferably such that the proportion of fine particles having a major axis of 50 μm or less (the amount of fine powder) exceeds 15%, more preferably 20% or more, The ratio (large particle amount) of particles having a major axis of 300 μm or more is preferably less than 20%, more preferably 15% or less, and particularly preferably 10% or less with respect to all particles.
The dryer that can be used in the first heat drying step of the polyacetal obtained through the polymerization reaction step and the polymerization catalyst deactivation step is not limited to the following, but for example, a paddle dryer or drum Examples thereof include a stirring dryer such as a mold dryer, and a stationary dryer such as a conveyor dryer and a thermostatic device. In particular, it is preferable to use a stirring dryer from the viewpoint of improving the drying efficiency. In addition, examples of the heating method include a direct heating method in which hot air or the like is ventilated to dry, an indirect heating method using heat transfer from a heat medium, or the like.

  In this embodiment, when a polyacetal is obtained using a cyclic formaldehyde (for example, trioxane) and a cyclic ether and / or a cyclic formal (for example, 1,3-dioxolane), the polyacetal in the polyacetal after the first stage heat drying step is not used. From the viewpoint of reducing the residual amount of reactive cyclic formaldehyde (for example, trioxane) and its decomposition products, the drying temperature in the first stage heat drying step is in the range of 130 ° C. ± 10 ° C., that is, 120-140 ° C., 130-140 ° C. It is more preferable that When the drying temperature in the first stage heat drying step is within the above temperature range, unreacted cyclic formaldehyde (for example, trioxane) remaining in the polyacetal tends to be suppressed to 10000 ppm or less. In the second stage heat drying step, the polyacetal Tends to be a light aggregate. Also, because the polyacetal is uniformly dried, the drying time in the first stage heat drying step is in the range of 30 minutes to 500 minutes after the product temperature of the polyacetal reaches the drying temperature in the first stage heat drying step. It is preferable.

The amount of unreacted cyclic formaldehyde remaining in the polyacetal obtained through the first-stage heat drying step is preferably 10,000 ppm or less, more preferably 8000 ppm or less, and further preferably 6000 ppm or less. When the amount of unreacted cyclic formaldehyde remaining in the polyacetal obtained through the first-stage heating and drying step is within the above range, the second-stage heating and drying step further suppresses polyacetal from becoming a complete aggregate, It tends to be a light agglomerate.
In this embodiment, the amount of unreacted cyclic formaldehyde remaining in the polyacetal can be measured by the method described in the examples below.

<Second stage heat drying process>
The drying method in the second-stage heat drying step of the polyacetal obtained through the above steps is not limited to the following, but examples include a drying method using the above-mentioned stirring dryer and the like. It is done. A polyacetal can be obtained through the first-stage heat drying process and the second-stage heat drying process described above. The drying temperature in the second stage heat drying step is Tm-20 ° C. or more and Tm or less, more preferably Tm−10 ° C. or more and Tm or less, and more preferably Tm− when the melting point of polyacetal is Tm. It is 7 degreeC or more and Tm or less. When the second stage heat drying is performed in this temperature range, the obtained polyacetal becomes a light agglomerate with high handleability. In the second stage heat drying step, drying is preferably performed while stirring the polyacetal in order to prevent complete aggregation due to temperature unevenness. Also, the drying time in the second stage heating and drying step is a range of 20 minutes or more and 500 minutes or less after the product temperature of the polyacetal reaches the drying temperature of the above-mentioned second stage heating and drying step because the polyacetal is uniformly heated. It is preferable to carry out with.
Further, the particle size of the polyacetal particles obtained through the second stage heat drying step is preferably 15% or less, more preferably 10% or less, and the proportion of particles having a major axis of 50 μm or less (fine powder amount) is preferably 5% or less. % Or less is particularly preferable, and the ratio (large particle amount) of particles having a major axis of 300 μm or more is preferably 20% or more, more preferably 30% or more, and particularly preferably 50% or more with respect to all particles.
Here, the polyacetal light agglomerate refers to a polyacetal agglomerate that can be easily returned to the particle size before agglomeration, and specifically refers to a polyacetal that satisfies the following conditions. The proportion of fine particles having a major axis of 50 μm or less (amount of fine powder) is 15% or less with respect to all particles, and the proportion of particles having a major axis of 300 μm or more (large particle amount) is 20% or more with respect to all particles, When mixing with a vortex mixer at a rotational speed of 3000 rpm for 15 minutes, the proportion of fine particles having a major axis of 50 μm or less (fine powder amount) exceeds 15% of the total particles, and the proportion of particles having a major axis of 300 μm or more ( It is a polyacetal (polyacetal light agglomerate) having a large particle amount) of less than 20% based on all particles.

  The light agglomerates were evaluated by photographing polyacetal particles using a microscope (trade name “VHX-2000”, manufactured by Keyence Corporation), and randomly extracting 2000 particles from the photographed particles. Calculate the ratio of the number of fine powders with respect to the total number of particles as the fine powder having a long diameter of 50 μm or less, and set the value as the fine powder amount [%]. A method of evaluating the change in particle diameter by calculating the ratio of the number and setting the value as the large particle amount [%] and then increasing or decreasing the fine particle amount and the large particle amount can be used. Furthermore, the polyacetal after the second stage heating and drying step is put in a screw tube, mixed with a digital vortex mixer (trade name “DIGITAL VORTEX-GENIE 2” manufactured by MS Equipment Co., Ltd.) at a rotational speed of 3000 rpm for 15 minutes, and mixed. The subsequent polyacetal can be evaluated for light agglomeration by calculating the amount of fine powder and large particles using the above-described evaluation method and comparing the particle diameters before and after pulverization.

  When the second stage heat drying process is not performed, or when drying is performed at a temperature outside the above temperature range, the polyacetal after drying contains 15% or more of fine powder having a major axis of 50 μm or less, or the major axis has a major axis of 300 μm or more. Large grains may be less than 20%. In such a case, there is a possibility of causing poor transportation due to clogging of the conveying piping in the subsequent process or adhesion to the piping wall surface, deterioration of miscibility when blending with the additive, or additive in the extruder May cause kneading failure during melt kneading.

≪Method for producing polyacetal resin composition≫
The manufacturing method of the polyacetal resin composition of this embodiment includes the process of melt-kneading the polyacetal and additive obtained through the above-mentioned first stage heat drying process and second stage heat drying process.
It does not specifically limit as a melt-kneading method, The well-known method used when manufacturing a polyacetal resin composition is mentioned.

[Additive]
In the method for producing a polyacetal resin composition of the present embodiment, various additives conventionally used in polyacetal resin compositions can be added within a range that does not impair the object of the present invention. Examples of the additive include, but are not limited to, the following antioxidant, formaldehyde, formic acid scavenger, and release agent.

<Antioxidant>
The antioxidant is preferably a hindered phenol antioxidant from the viewpoint of improving the thermal stability of the polyacetal resin composition.

  Examples of the hindered phenol antioxidant include, but are not limited to, n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate, n -Octadecyl-3- (3'-methyl-5'-t-butyl-4'-hydroxyphenyl) propionate, n-tetradecyl-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) ) Propionate, 1,6-hexanediol-bis- (3- (3 ′-, 5′-di-t-butyl-4′-hydroxyphenyl) propionate), 1,4-butanediol-bis-3- ( 3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) -propionate), triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) pro Onato], and the like.

  Other hindered phenolic antioxidants are not limited to the following, for example, pentaerythritol tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl)- Propionate], 3,9-bis- (2- (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy) -1,1-dimethylethyl-) 2,4,8,10 -Tetraoxaspiro (5,5) undecane, N, N'-bis-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionyldiamine, N, N'-bis- ( 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionyl) hydrazine, N-salicyloyl-N′-salicylidenehydrazine, 3- (N-salicyloyl) amino-1,2, 4 Triazole, N, N'-bis - (2- (3- (3 ', 5'-di -t- butyl-4'-hydroxyphenyl) propionyloxy) ethyl) Oxyamide also be mentioned.

  Among the hindered phenol antioxidants described above, triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) is used from the viewpoint of improving the thermal stability of the polyacetal resin composition. Propionate], pentaerythritol tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate] is preferred.

<Formaldehyde and formic acid scavenger>
Examples of the formaldehyde and formic acid scavengers include, but are not limited to, (1) compounds and polymers containing formaldehyde-reactive nitrogen, and (2) hydroxides of alkali metals or alkaline earth metals. , Inorganic acid salts, carboxylate salts and alkoxides.

(1) Formaldehyde-reactive nitrogen-containing compounds and polymers are not limited to the following, but include, for example, (i) dicyandiamide, (b) amino-substituted triazine, (c) amino-substituted triazine and formaldehyde Examples include cocondensates.
(B) Specific examples of amino-substituted triazines include guanamine (2,4-diamino-sym-triazine), melamine (2,4,6-triamino-sym-triazine), N-butylmelamine, and N-phenylmelamine. N, N-diphenylmelamine, N, N-diallylmelamine, N, N-diallylmelamine, N, N ′, N ″ -triphenylmelamine, N-methylolmelamine, N, N′-dimethylolmelamine, N , N ′, N ″ -trimethylolmelamine, benzoguanamine (2,4-diamino-6-phenyl-sym-triazine), 2,4-diamino-6-methyl-sym-triazine, 2,4-diamino-6 -Butyl-sym-triazine, 2,4-diamino-6-benzyloxy-sym-triazine, 2,4-diamino-6-butoxy- sym-triazine, 2,4-diamino-6-cyclohexyl-sym-triazine, 2,4-diamino-6-chloro-sym-triazine, 2,4-diamino-6-mercapto-sym-triazine, 2,4- Examples include dioxy-6-amino-sym-triazine (Amelite), 2-oxy-4,6-diamino-sym-triazine (Ameline), N, N ′, N ″ -tetracyanoethylbenzoguanamine and the like.
(C) Specific examples of the co-condensate of amino-substituted triazine and formaldehyde include melamine-formaldehyde polycondensate.

  Among the formaldehyde and formic acid scavengers mentioned above, dicyandiamide, melamine, and melamine-formaldehyde polycondensate are preferable.

  (2) Alkali metal or alkaline earth metal hydroxide, inorganic acid salt, carboxylate, and alkoxide are not particularly limited, but specific examples include sodium, potassium, magnesium, calcium or barium Examples thereof include hydroxides, carbonates, phosphates, silicates, borates and carboxylates of the metals. The carboxylic acid of the carboxylate is a saturated or unsaturated aliphatic carboxylic acid having 10 to 36 carbon atoms, and these carboxylic acids may be substituted with a hydroxy group. The saturated aliphatic carboxylic acid is not particularly limited. Is mentioned. Examples of the unsaturated aliphatic carboxylic acid include undecylenic acid, oleic acid, elaidic acid, celetic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propiolic acid, stearic acid and the like. The alkoxide is not particularly limited, and examples thereof include methoxide and ethoxide of the above metals.

  Other scavengers that capture formaldehyde (formaldehyde scavengers) include hydrazide compounds, aminotriazine compounds, guanidine compounds, urea compounds, amino acid compounds, amino compounds, imide compounds, and imidazoles. Of these, amide compounds are preferred.

  Although it does not specifically limit as a hydrazide type compound, For example, 1-dimethyl-2- carboxyethyl) -1,3- dioxane hydrazide, 3,9-bis (2-carboxyethyl) -2,4,8,10- Tetraoxaspiro [5,5] undecanedihydrazide, 1,3,5-tris (3-carboxypropyl) isocyanurate trihydrazide, etc .; (meth) acrylic acid hydrazide homopolymer or polymer type hydrazide compounds, etc. Can be mentioned. Among these, it is preferable to use a dihydrazide compound. More preferred are aliphatic dihydrazide compounds such as 1,12-dodecanedicarboxylic acid dihydrazide, sebacic acid dihydrazide, adipic acid dihydrazide; 1,8-naphthalenedicarboxylic acid dihydrazide, 2,6-naphthalenecarboxylic acid dihydrazide, terephthalic acid dihydrazide, etc. An aromatic dihydrazide compound.

  Although it does not specifically limit as an amino triazine type compound, Specifically, a melamine, an acetoguanamine, a stealog anamine, a benzoguanamine, a phenyl benzoguanamine, a phthalo guanamine, naphthalene guanamine etc. are mentioned, for example. Among these, benzoguanamine is preferable.

  Specific examples of the guanidine-based compound include, but are not limited to, glycosylamine, guanoline, glycocyanidine, oxalylguanidine, creatinine, iminourazole, malonylguanidine, mesoxalylguanidine, and the like.

  Although it does not specifically limit as a urea type compound, Specifically, alkylene urea, such as biuret, biurea, ethylene urea, propylene urea, etc. are mentioned, for example. Among these, ethylene urea is preferable.

  Although it does not specifically limit as an amino acid type compound, For example, glycine, alanine, arginine, glutamine etc. are mentioned.

  Although it does not specifically limit as an amino compound, Specifically, amino alcohols, such as a monoethanolamine, diethanolamine, 2-amino-1-butanol, are mentioned, for example.

  Although it does not specifically limit as an imide type compound, Specifically, a phthalic acid imide, trimellitic acid imide, pyromellitic acid imide, pyromellitic acid diimide etc. are mentioned, for example. Among these, phthalimide is preferable.

  Specific examples of the imidazole compound include, but are not limited to, imidazole, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, and 2-phenylimidazole.

  Although it does not specifically limit as an amide type compound, Specifically, for example, polyamide 6, polyamide 66, polymetaxylylene adipamide (polyamide MXD6), dimer acid polyamide, polyamide 12, 6/66/610/12 Examples thereof include an original copolymer polyamide, a 6/66/610 terpolymer polyamide, and a 6/12 copolymer polyamide.

<Release agent>
Examples of the release agent include, but are not limited to, (1) alcohol, (2) ester of alcohol and fatty acid, (3) ester of alcohol and dicarboxylic acid, silicone oil, and the like. It is done.

  (1) Although it does not specifically limit as alcohol, Specifically, there exist monohydric alcohol and a polyhydric alcohol, for example, Although it does not specifically limit as an example of monohydric alcohol, For example, octyl alcohol, capryl alcohol, nonyl Alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, oleyl alcohol, nonadecyl alcohol, eicosyl alcohol, behenyl alcohol, ceryl alcohol, melyl alcohol Examples include silalcohol, 2-hexyldecanol, 2-octyldodecanol, 2-decyltetradecanol, and unilin alcohol. Although it does not specifically limit as a polyhydric alcohol, For example, it is a polyhydric alcohol containing 2-6 carbon atoms, Specifically, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene Examples include glycol, butanediol, pentanediol, hexanediol, glycerin, diglycerin, triglycerin, threitol, erythritol, pentaerythritol, arabitol, ribitol, xylitol, sorbite, sorbitan, sorbitol, mannitol and the like.

  (2) The ester of alcohol and fatty acid is preferably a fatty acid compound, preferably a fatty acid selected from palmitic acid, stearic acid, behenic acid, and montanic acid, and many selected from glycerin, pentaerythritol, sorbitan, and sorbitol. There are fatty acid esters derived from polyhydric alcohols. The hydroxy group of these fatty acid ester compounds may be present or absent, and does not limit the fatty acid ester compound. For example, it may be a monoester, a diester, or a triester. Further, the hydroxy group may be blocked with boric acid or the like.

  Specific examples of preferred fatty acid esters include glycerin monopalmitate, glycerin dipalmitate, glycerin tripalmitate, glycerin monostearate, glycerin distearate, glycerin tristearate, glycerin monobehenate, glycerin dibehenate, Glycerol tribehenate, glycerin monomontanate, glycerin dimontanate, glycerin trimontanate, pentaerythritol monopalmitate, pentaerythritol dipalmitate, pentaerythritol tripalmitate, pentaerythritol tetrapalmitate, pentaerythritol mono Stearate, pentaerythritol distearate, pentaerythritol tristearate, pentaerythritol tetrastearate Pentaerythritol monobehenate, pentaerythritol dibehenate, pentaerythritol tribehenate, pentaerythritol tetrabehenate, pentaerythritol monomontanate, pentaerythritol dimontanate, pentaerythritol trimontanate, pentaerythritol tetramontanate, Sorbitan monopalmitate, sorbitan dipalmitate, sorbitan tripalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monobehenate, sorbitan dibehenate, sorbitan tribehenate, sorbitan monomontanate , Sorbitan dimontanate, sorbitan trimontanate, sorbitol monopalmitate, sorbitol zippa Mitate, sorbitol tripalmitate, sorbitol monostearate, sorbitol distearate, sorbitol tristearate, sorbitol monobehenate, sorbitol dibehenate, sorbitol tribehenate, sorbitol monomontanate, sorbitol dimontanate, sorbitol Such as limontanate. Moreover, boric acid ester of glycerol mono fatty acid ester is also mentioned as the aliphatic ester compound whose hydroxy group is blocked with boric acid or the like.

  (3) Although ester of alcohol and dicarboxylic acid is not specifically limited, For example, as alcohol, methyl alcohol, ethyl alcohol, propyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, n-amyl alcohol, 2- Saturated and unsaturated alcohols such as pentanol, n-heptyl alcohol, n-octyl alcohol, n-nonyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol and behenyl alcohol, and oxalic acid, malonic acid and succinic acid as dicarboxylic acids Acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanoic acid, brassic acid, maleic acid, fumaric acid, glutaconic acid monoester, dies Le, and the like.

  In the method for producing the polyacetal resin composition of the present embodiment, the blending ratio of the polyacetal and the additive is preferably 0.1 to 10 parts by weight of the additive with respect to 100 parts by weight of the polyacetal.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention more concretely, this invention is not limited by these.

The crude polyacetal used in Examples of the present application was polymerized by the method shown below.
[Polyacetal I polymerization method]
A twin-screw self-cleaning type polymerization machine with a jacket through which a heat medium can pass is adjusted to 80 ° C., trioxane is 4 kg / h, and 1,3-dioxolane as a comonomer is 394.9 g / h (based on 1 mol of trioxane). 4 mol%), methylal as a chain transfer agent was continuously added at 7.3 g / h. Further, boron trifluoride di-n-butyl etherate was continuously added as a polymerization catalyst at 2.0 × 10 ⁻⁵ mol with respect to 1 mol of trioxane to carry out polymerization. The polyacetal discharged from the polymerization machine was charged into a 0.1% aqueous solution of triethylamine and pulverized using a wet pulverizer (trade name “Warling Blender 7011HS” manufactured by WARING) to inactivate the polymerization. Polyacetal I was obtained by filtering and washing the deactivated polyacetal with a centrifuge.

[Polyacetal II polymerization method]
Polymerization is carried out in the same manner as in the above polyacetal I polymerization method except that 1,3-dioxolane is 148.1 g / h (1.5 mol% with respect to 1 mol of trioxane) as a comonomer, and polyacetal II is obtained. Obtained.

[Method for evaluating the amount of unreacted trioxane]
3 g of polyacetal after the first heating and drying step described later was heated at 140 ° C. for 90 minutes under a nitrogen stream (50 NL / hour), and unreacted trioxane gas generated from the polyacetal was absorbed into water to obtain an aqueous solution. Thereafter, the trioxane content of the obtained aqueous solution was measured using gas chromatography. The measured value was defined as the amount of unreacted trioxane.

[Evaluation method of melting point]
Using a differential thermal scanning calorimeter (trade name “DSC8000”, manufactured by Perkin Elmer Co., Ltd.), 3 mg of the sample was once heated to 200 ° C. at a heating rate of 300 ° C./min and melted, and then the cooling rate was 80 ° C./min. The mixture was cooled to 100 ° C., heated again at a heating rate of 2.5 ° C./min, and the temperature at the top of the endothermic peak was measured to obtain the melting point.

[Evaluation method of fine powder amount and large particle amount]
The particles of polyacetal were photographed using a microscope (manufactured by Keyence Corporation, trade name “VHX-2000”). Take a picture at a magnification of 100 times, extract 2000 particles randomly from the photographed particles, make a fine powder with a major axis of 50 μm or less among them, calculate the ratio of the number of fine powders to the total number of particles, the value Was defined as the amount of fine powder [%]. Moreover, the thing with a long diameter of 300 micrometers or more was made into a large particle, the ratio of the large particle number with respect to the total particle number was computed, and the value was made into the large particle amount [%]. The light agglomerate formation was determined based on the amount of fine powder and large particles.

[Evaluation method of light cohesion]
The polyacetal after the second stage heat drying step was put into a screw tube, and mixed for 15 minutes at a rotational speed of 3000 rpm with a digital vortex mixer (manufactured by MS Equipment Co., Ltd., trade name “DIGITAL Vortex-GENIE 2”). The polyacetal after mixing was evaluated for light agglomeration by calculating the amount of fine powder and large particles using the above-described evaluation method and comparing the particle sizes before and after pulverization.
The case where the large particle amount after the second stage heat drying step is significantly increased compared with that before heating, and the large particle amount after mixing is approximately the same as the large particle amount before heating, ○, before and after heating or before and after mixing The case where the amount of fine powder and / or the amount of large particles hardly changed was evaluated as x.

[Evaluation method of formaldehyde emission]
After adding the additives shown in Table 2 below to 100 parts by weight of the polyacetal after the second-stage heating and drying step, mixing by hand blending, a lab plastmill micro twin screw extruder (manufactured by Toyo Seiki Co., Ltd.) , 500 g of product name “2D15W”). A polyacetal resin composition was obtained by extruding as a strand from a die part and pelletizing under conditions of a preset temperature of 200 ° C. and a discharge rate of 1.5 kg / hour. Immediately after the inside of the machine is purged for 3 minutes after being fed from the extruder supply port, 5 g of the sampled pellets are extruded to obtain an initial polyacetal resin composition, and 5 g of the sampled pellets are sampled 15 minutes after the initial extrusion is sampled. A polyacetal resin composition was obtained. Formaldehyde generated was extracted into water by immersing 2 g each of the pellets at the beginning and end of extrusion into 20 g of water and heating at 90 ° C. for 7 hours. Formaldehyde in water was reacted with acetylacetone in the presence of ammonium ions, the absorption peak at a wavelength of 412 nm was measured with a UV spectrometer for the reaction product, and formaldehyde emission (ppm) was determined.

Example 1
As a first-stage heating and drying step, 150 g of polyacetal I was placed in an eggplant flask and heated at 140 ° C. for 30 minutes while rotating at 140 rpm using an evaporator (trade name “Rotary evaporator R-210”, manufactured by BUCHI Labortechnik). . Subsequently, as the second-stage heating granulation step, heating was performed at 162 ° C. for 20 minutes using the same evaporator. By repeating the above operation 10 times in total, polyacetal A-1 was obtained. The properties of the resulting polyacetal A-1 were measured by the above method. The results are shown in Table 1.

(Examples 2 to 5)
The process was performed in the same manner as in Example 1 except for the conditions shown in Table 1. The results are shown in Table 1.

(Examples 6 to 7)
Using polyacetal A-1, a polyacetal resin composition was obtained based on the above-described evaluation method of formaldehyde emission. Table 2 shows the results of the formaldehyde emission amount of the obtained polyacetal resin composition.

(Comparative Example 1)
As a first drying step, 150 g of polyacetal I was placed in an eggplant flask and heated at 140 ° C. for 30 minutes while rotating at 140 rpm using the above-described evaporator. The above operation was repeated a total of 10 times to obtain polyacetal A-2. The characteristics of the obtained polyacetal A-2 were measured by the above method. The results are shown in Table 1.

(Comparative Example 2)
A polyacetal A-3 was obtained in the same manner as in Example 1 except for the conditions shown in Table 1. The properties of the resulting polyacetal A-3 were measured by the above method. The results are shown in Table 1.

(Comparative Example 3)
The process was performed in the same manner as in Example 1 except for the conditions shown in Table 1. The results are shown in Table 1.

(Comparative Examples 4 and 5)
The same operation as in Comparative Example 1 was performed except for the conditions shown in Table 1. The results are shown in Table 1.

(Comparative Examples 6-9)
Except for the conditions shown in Table 2, a polyacetal resin composition was obtained based on the above-described method for evaluating the amount of formaldehyde released in the same manner as in Examples 6-7. Table 2 shows the results of the formaldehyde emission amount of the obtained polyacetal resin composition.

From Tables 1 and 2, the following results were obtained.
In Comparative Examples 1 to 5, since the above-mentioned production conditions were not satisfied, polyacetal light aggregates excellent in handleability could not be obtained. Further, from the results of Comparative Examples 6 to 9, neither a decrease in formaldehyde emission amount nor stability was observed. On the other hand, in Examples 1-5, since the above-mentioned manufacturing conditions were satisfied, a light agglomerate excellent in handleability was obtained, and from the results of Examples 6-7, a decrease in formaldehyde emission was observed. Furthermore, in Example 2, since the second stage heating temperature is low, the handleability is slightly low, whereas in Examples 1 and 3-5, the second stage heating temperature is high, so that the handleability and thermal stability are high. Both sexes showed particularly good results.

Abbreviations in the table are as follows.
Additive B-1: Triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate]
Additive B-2: Pentaerythritol tetrakis- (3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) -propionate)
Additive C: Nylon 66
Additive D: Ethylene glycol difatty acid ester Additive E: Calcium distearate

  Since the polyacetal resin composition containing polyacetal obtained by the method for producing polyacetal according to the present invention has a small amount of formaldehyde emission, it can be used industrially in various parts materials in various industrial material fields including the automobile field. It has sex. Furthermore, since the polyacetal obtained by the production method according to the present invention is a light agglomerate, it is easy to handle during transportation in a pipe, and also maintains miscibility with additives, so that productivity is stable. Improvement in quality and quality stability is expected.

Claims (11)

A first-stage heating and drying step of heating polyacetal in a range of 130 ° C. ± 10 ° C .;
A second-stage heat-drying step of heating the polyacetal obtained in the first-stage heat-drying step at a temperature in the range of Tm-20 ° C. or higher and Tm or lower when the melting point of the polyacetal is Tm. Method.   The method for producing a polyacetal according to claim 1, wherein a light agglomerate of polyacetal is formed in the second stage heat drying step. The polyacetal production method according to claim 1 or 2, wherein the polyacetal obtained in the second stage heat drying step is a light agglomerate satisfying the following (1) and (2):
(1) The proportion of particles having a major axis of 50 μm or less is 15% or less with respect to all particles,
(2) The ratio of particles having a major axis of 300 μm or more is 20% or more with respect to all particles.   The heating time of the first stage heating and drying step is in the range of 30 minutes to 500 minutes after the product temperature of the polyacetal reaches the drying temperature of the first stage heating and drying step described above. Of producing polyacetal.   The heating time of the second stage heating and drying process is in the range of 20 minutes to 500 minutes after the product temperature of the polyacetal reaches the drying temperature of the second stage heating and drying process described above. In the second stage heating and drying process, the polyacetal The method for producing a polyacetal according to any one of claims 1 to 4, wherein drying is performed while stirring.   The polyacetal is a polyacetal obtained by copolymerizing a formaldehyde monomer or cyclic formaldehyde and a cyclic ether and / or cyclic formal in the presence of an initiator. Production method of polyacetal.   The method for producing a polyacetal according to any one of claims 1 to 6, wherein the polyacetal is a polyacetal obtained by copolymerizing trioxane and a cyclic ether and / or a cyclic formal in the presence of an initiator.   The method for producing a polyacetal according to claim 6 or 7, wherein the cyclic ether and / or the cyclic formal is 1,3-dioxolane.   The method for producing a polyacetal according to any one of claims 1 to 8, wherein the amount of unreacted cyclic formaldehyde remaining in the polyacetal obtained through the first-stage heat drying step is 10,000 ppm or less. The ratio of particles having a major axis of 50 μm or less is 15% or less with respect to all particles, and the ratio of particles having a major axis of 300 μm or more is 20% or more with respect to all particles,
When mixing with a vortex mixer at a rotational speed of 3000 rpm for 15 minutes, the proportion of fine particles having a major axis of 50 μm or less (fine powder amount) exceeds 15% of the total particles, and the proportion of particles having a major axis of 300 μm or more ( A polyacetal light agglomerate having a large particle amount) of less than 20% based on all particles. A first-stage heating and drying step of heating polyacetal in a range of 130 ° C. ± 10 ° C .;
When the melting point of the polyacetal is Tm, a second-stage heat-drying step of heating the polyacetal obtained in the first-step heat-drying step at a temperature in the range of Tm-20 ° C. or higher and Tm or lower;
And a step of melt-kneading the polyacetal obtained in the second-stage heat-drying step and the additive, and a method for producing a polyacetal resin composition.