JP2022097987A - Polyacetal copolymer, and production method thereof - Google Patents

Abstract

To provide a polyacetal copolymer excellent in rigidity and impact resistance having thermal stability, especially, low discoloration when fused and remaining in a molding machine, and a stable production method thereof.SOLUTION: A production method of a polyacetal copolymer includes a step for copolymerizing trioxane (A) of 100 pts.mass, a cyclic acetal compound (B) of 0.05-5 pts.mass having an oxyalkylene group of 2 or more carbons in the ring, and a predetermined aliphatic glycidyl ether compound (C) of 0.001-0.5 pts.mass having a sodium content of 0.1-100 ppm mass, in the presence of a linear formal compound (D) as a molecular weight modifier. In the step, (b+c+d)/a=4.5-9 μmol/g is satisfied, where a is a total mass (g) of (A)-(C), b is a mole number of (D), and c and d respectively are total mole numbers of water and methanol contained in (A)-(C).SELECTED DRAWING: None

Description

The present invention relates to a polyacetal copolymer and a method for producing the same.

Polyacetal resin has an excellent balance of mechanical properties, chemical resistance, slidability, etc., and because it is easy to process, it is mainly used as engineering plastics for electrical / electronic parts, automobile parts, and other various mechanical parts. It is widely used as. However, with the expansion of the range of use in recent years, there is a tendency that more advanced characteristics are gradually required. For example, when a polyacetal resin is used for thin-walled parts or the like, rigidity, creep resistance, etc. are required while maintaining the fluidity, moldability, thermal stability, and slidability inherent in the polyacetal resin. There are many.

However, it is extremely difficult to satisfy the above required characteristics in a well-balanced manner. For example, in the method of blending a filler such as a fibrous material with a polyacetal resin in order to improve the rigidity, poor appearance of the molded product, deterioration of sliding characteristics, deterioration of fluidity, etc. occur, and further, depending on the filler to be blended, heat may occur. Stability may be reduced. Further, in the polyacetal copolymer, it is known that the rigidity and the like are improved by reducing the number of comonomer to be copolymerized. However, the improvement in rigidity by this method is not sufficient, and on the other hand, the decrease in the amount of comonomer causes a decrease in the thermal stability of the polymer and the accompanying adverse effects on fluidity, moldability and the like.

In view of the above circumstances, studies have been conducted focusing on the improvement of rigidity and the like due to the modification of the polymer skeleton of the polyacetal resin itself, and a method for improving the rigidity has been proposed (see Patent Document 1). According to this method, the rigidity can be improved while maintaining various properties inherent in the polyacetal resin.

Japanese Unexamined Patent Publication No. 2001-163942

The polyacetal copolymer obtained by the above method is basically good in terms of thermal stability. However, as a result of further studies thereafter, the operation of the polymerization step, the terminal stabilizing step, the melt-kneading step with the compound such as the stabilizer, etc. becomes unstable in its production, or the heat of the obtained copolymer becomes unstable. It turned out that the stability may be inferior. Since such a copolymer is inferior in thermal stability, there is a problem that, for example, the color of the copolymer is discolored when it is melt-retained in the molding machine. In addition, some mechanical properties, especially impact resistance, may not provide satisfactory values. Elucidation and improvement of the cause has been an important issue in putting the polyacetal copolymer by these methods into practical use.

The present invention has been made in view of the above-mentioned conventional problems, and the present invention has excellent rigidity and excellent impact resistance, and also has thermal stability, particularly low discoloration during melt retention in the molding machine. It is an object of the present invention to provide a polyacetal copolymer and a stable production method thereof.

As a result of diligent studies to solve the above problems, the present inventor has found that the sodium content in a specific aliphatic glycidyl ether compound used for forming a branched / crosslinked structure in the polymer skeleton of a polyacetal copolymer is We have found a factor that holds the key to solving the problem, a suitable range of the degree of polymerization of the polyacetal copolymer and a means for controlling the degree of polymerization, and have completed the present invention.

One aspect of the present invention that solves the above problems is as follows.
(1) 100 parts by mass of trioxane (A), 0.05 to 5 parts by mass of a cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in a ring, trimethylolpropane triglycidyl ether, and glycerol triglycidyl. An aliphatic glycidyl ether compound (C) of 0.001 to 0.5 parts by mass, which is one or more selected from the group consisting of ether and pentaerythritol tetraglycidyl ether and has a sodium content of 0.1 to 100% by mass. Including the step of performing copolymerization in the presence of the linear formal compound (D) as a molecular weight modifier.
In the step, the total mass (g) of the (A), (B) and (C) is included in a, the number of moles of the (D) is included in b, and the (A), (B) and (C) are included. A method for producing a polyacetal copolymer, which is set so as to satisfy (b + c + d) / a = 4.5 to 9 μmol / g, where c and d are the total number of moles of water and methanol, respectively.

(2) The method for producing a polyacetal copolymer according to (1) above, wherein the linear formal compound (D) is at least one selected from the group consisting of methylal, etylal and dibutoxymethane.

(3) A polyacetal copolymer obtained by the method for producing a polyacetal copolymer according to (1) or (2) above.

According to the present invention, it is possible to provide a polyacetal copolymer having excellent rigidity, impact resistance, etc., and also having thermal stability, particularly low discoloration during melt retention in a molding machine, and a stable production method thereof. can.

<Manufacturing method of polyacetal copolymer>
The method for producing a polyacetal copolymer of the present embodiment comprises 100 parts by mass of trimethylolpropane (A), 0.05 to 5 parts by mass of a cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring, and the like. (C) An aliphatic glycidyl ether compound (C) which is one or more selected from the group consisting of trimethylolpropane triglycidyl ether, glycerol triglycidyl ether and pentaerythritol tetraglycidyl ether and has a sodium content of 0.1 to 100% by mass. A step of copolymerizing 0.001 to 0.5 parts by mass in the presence of the linear formal compound (D) as a molecular weight adjuster is included. Then, in the above step, the total mass (g) of (A), (B) and (C) is a, the number of moles of (D) is b, and the water content contained in (A), (B) and (C). And, when the total number of moles of methanol is c and d, respectively, it is set to satisfy (b + c + d) / a = 4.5 to 9 μmol / g.
First, each component used in the production method of the present embodiment will be described below.

[Trioxane (A)]
Trioxane (A) is a cyclic trimer of formaldehyde, which is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acidic catalyst, and is used by purifying it by a method such as distillation. The trioxane (A) used for the polymerization is preferably one in which impurities such as water and methanol are reduced as much as possible.

[Cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring]
The cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring (hereinafter, also simply referred to as “cyclic acetal compound (B)”) is a cyclic acetal compound capable of copolymerizing with trioxane (A) (hereinafter, also referred to as “cyclic acetal compound (B)”). B), for example, 1,3-dioxolane, propanediolformal, diethyleneglycolformal, triethyleneglycolformal, 1,4-butanediolformal, 1,5-pentanediolformal, 1,6-hexanediolformal and the like. Among them, 1,3-dioxolane is preferable.

The copolymerization amount of the cyclic acetal compound (B) is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass, and more preferably 0.3 to 2 parts by mass with respect to 100 parts by mass of trioxane (A). .5 parts by mass. When the copolymerization ratio of the cyclic acetal compound (B) is less than 0.05 parts by mass, the difficulty of controlling the polymerization reaction increases and the thermal stability of the produced polyacetal copolymer becomes inferior. On the contrary, when the copolymerization ratio of the cyclic acetal compound (B) exceeds 5 parts by mass, the mechanical properties such as strength and rigidity are lowered.

[Aliphatic glycidyl ether compound (C)]
The aliphatic glycidyl ether compound (C) is one or more selected from trimethylolpropane triglycidyl ether, glycerol triglycidyl ether and pentaerythritol tetraglycidyl ether, and has 3 to 4 glycidyloxy groups in one molecule. Further, the aliphatic glycidyl ether compound (C) has a structure capable of forming a branched or crosslinked structure in the polymer skeleton by copolymerization with trioxane. In this respect, it is distinguished from the cyclic acetal compound (B). Further, in the present embodiment, the aliphatic glycidyl ether compound (C) has a sodium content of 0.1 to 100 mass ppm.

The copolymerization amount of the aliphatic glycidyl ether compound (C) is 0.001 to 0.5 parts by mass, preferably 0.01 to 0.5 parts by mass, based on 100 parts by mass of the trioxane of the component (A). Particularly preferably, it is 0.1 to 0.5 parts by mass. If the copolymerization amount of the component (C) is less than 0.001 part by mass, the effect of improving the rigidity may not be obtained. On the contrary, if it exceeds 0.5 parts by mass, a problem of poor moldability due to a decrease in fluidity may occur, and further, the mechanical properties of the obtained copolymer may decrease.

In the present embodiment, the aliphatic glycidyl ether compound (C) having a sodium content of 0.1 to 100% by mass is used, which is particularly excellent in thermal stability. It becomes possible to stably produce a polyacetal copolymer. If the sodium content of the aliphatic glycidyl ether compound (C) to be used exceeds 100% by mass, the operation of the polymerization step, the terminal stabilizing step, the commercialization step by blending a stabilizer, etc. becomes unstable, and the operation becomes unstable. The thermal stability of the obtained polyacetal copolymer is also inferior. Regarding the lower limit of the sodium content, the content is set to 0.1 mass ppm from the viewpoint of economic efficiency in the production of the aliphatic glycidyl ether compound (C). The sodium content is preferably 0.1 to 30 mass ppm, more preferably 0.2 to 5 mass ppm.

Aliphatic glycidyl ether compounds are generally produced by the reaction of alcohol with epichlorohydrin. Conventionally, a method of ring-opening and adding epichlorohydrin to an alcohol in the presence of an acidic catalyst and then intramolecularly closing the ring with an alkaline aqueous solution to obtain a glycidyl ether compound (for example, Japanese Patent Application Laid-Open No. 61-178974) is known. On the other hand, a method of reacting alcohol and epichlorohydrin in the presence of a solid alkali metal compound to produce a glycidyl ether compound in the presence of a solid alkali metal hydroxide pulverized in a reaction mixture (for example, special treatment). Kaihei 1-151567) is also disclosed. Due to such differences in the synthesis method and the purification step, aliphatic glycidyl ether compounds having different sodium contents are produced.

In the present embodiment, the polyacetal copolymer is basically a cation polymerization catalyst by adding a trioxane (A), a cyclic acetal compound (B) and an aliphatic glycidyl ether compound (C) in an appropriate amount of a molecular weight modifier. It can be obtained by a method such as bulk polymerization using.

[Linear formal compound (D)]
As the molecular weight adjusting agent used in this embodiment, a linear formal compound is used. Examples of the linear formal compound include methylal, etylal, dibutoxymethane, bis (methoxymethyl) ether, bis (ethoxymethyl) ether, bis (butoxymethyl) ether and the like. These may be used alone or in combination of two or more. Among them, one or more selected from the group consisting of methylal, etilal and dibutoxymethane is preferable.

In the present embodiment, in order to obtain a polyacetal copolymer having more excellent thermal stability, rigidity, impact resistance, etc., the cyclic acetal compound (B) and the aliphatic compound in the molecular chain of the polyacetal copolymer It is preferable that the structural units derived from the glycidyl ether compound (C) are uniformly dispersed. For that purpose, the cyclic acetal compound (B) and the catalyst are uniformly mixed in the production of the polyacetal copolymer by polymerization, and the aliphatic glycidyl ether compound (C) and the trioxane (C) and the trioxane (which are separately uniformly mixed in advance) are used. A method of adding it to the uniform mixed solution of A) and supplying it to a polymerization machine for polymerization is effective. By mixing in advance and preparing a uniform solution state, the dispersed state of the branched structure derived from the aliphatic glycidyl ether compound becomes good, the mechanical properties are improved, and the thermal stability is also excellent.

In producing the polyacetal copolymer of the present embodiment composed of the above-mentioned constituent components, the polymerization apparatus is not particularly limited, and a known apparatus is used, and any method such as a batch type or a continuous type can be used. Is. Further, it is preferable to keep the polymerization temperature at 65 to 115 ° C. Deactivation after polymerization is carried out by adding a basic compound or an aqueous solution thereof to the reaction product discharged from the polymerization machine or the reaction product in the polymerization machine after the polymerization reaction.

The cationic polymerization catalyst used in this embodiment includes lead tetrachloride, tin tetrachloride, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, antimon trifluoride, phosphorus pentafluoride, antimon trifluoride, and trifluoride. Boron trifluoride, boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, boron trifluoride dioxanate, boron trifluoride acetic anhydrate, boron trifluoride triethylamine complex compound, etc. Inorganic and organic acids such as position compounds, perchloric acid, acetylparklorate, t-butylparklorate, hydroxyacetic acid, trichloroacetic acid, trifluoroacetic acid, p-toluenesulfonic acid, toethyloxonium tetrafluoroborate, triphenylmethyl Examples thereof include complex salt compounds such as hexafluoroantimonate, allyldiazonium hexafluorophosphate and allyldiazonium tetrafluoroborate, alkyl metal salts such as diethylzinc, triethylaluminum and diethylaluminum chloride, heteropolyacids and isopolyacids. Among them, especially three such as boron trifluoride, boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, boron trifluoride dioxanate, boron trifluoride acetic anhydrate, and boron trifluoride triethylamine complex compound. Boron trifluoride coordination compounds are preferred. These catalysts can also be used after being diluted in advance with an organic solvent or the like.

Examples of the basic compound for neutralizing and inactivating the polymerization catalyst include ammonia, amines such as triethylamine, tributylamine, triethanolamine and tributanolamine, or alkali metals and alkaline earth metals. Hydroxide salts and other known catalytic deactivating agents are used. Further, after the polymerization reaction, it is preferable to quickly add these aqueous solutions to the product to inactivate it. After the polymerization method and the deactivation method, if necessary, further washing, separation and recovery of unreacted monomers, drying and the like are carried out by conventionally known methods.

Further, stabilization treatment is performed by a known method as necessary, such as decomposition and removal of the unstable end portion or sealing of the unstable end with a stable substance, and various necessary stabilizers are blended. Examples of the stabilizer used here include one or more of hindered phenolic compounds, nitrogen-containing compounds, hydroxides of alkaline or alkaline earth metals, inorganic salts, carboxylates and the like. can. Further, as long as the effect of the polyacetal copolymer of the present embodiment is not impaired, general additives to the polyacetal resin such as dyes, colorants such as pigments, lubricants, nucleating agents, mold release agents, and charging are required. One or more kinds of inhibitors, surfactants, organic polymer materials, inorganic or organic fibrous, powdery, plate-like fillers and the like can be added.

In the present embodiment, in the step of performing the copolymerization, the total mass (g) of the trioxane (A), the cyclic acetal compound (B), and the aliphatic glycidyl ether compound (C) is a, and the linear formal compound (D). When the total number of moles of water and methanol contained in the components (A), (B) and (C) is c and d, respectively, (b + c + d) / a = 4.5 to 9 μmol / g. Set to meet. When (b + c + d) / a = 4.5 to 9 μmol / g is satisfied, rigidity and impact resistance can be improved while maintaining moldability.
The water and methanol contained in the above (A), (B) and (C) are derived from the respective impurities.

<Polyacetal copolymer>
The polyacetal copolymer of the present embodiment is obtained by the above-mentioned method for producing a polyacetal copolymer of the present embodiment. Therefore, the polyacetal copolymer of the present embodiment has excellent rigidity and impact resistance, and also has thermal stability, particularly low discoloration during melt retention in the molding machine.

Hereinafter, the present embodiment will be described in more detail by way of examples, but the present embodiment is not limited to the following examples.

[Examples 1 to 10]
Two with paddles using a continuous mixing reactor consisting of a barrel with a jacket through which a heat (cold) medium is passed on the outside and a shape in which two circles partially overlap each other and a rotating shaft with a paddle. The trioxane (A), the cyclic acetal compound (B), and the aliphatic glycidyl ether compound (C) were added at the ratios and amounts shown in Table 1 while rotating each of the rotation axes of the above at 150 rpm. Further, the linear formal compound (D) shown in Table 1 is continuously supplied as a molecular weight modifier at the ratio and amount shown in Table 1, and the catalyst boron trifluoride gas is 0 with respect to trioxane in terms of boron trifluoride. A homogeneous mixture mixed so as to have a molecular weight of .005% by mass was continuously added and supplied to carry out bulk polymerization. The reaction product discharged from the polymerizer was rapidly passed through the crusher and added to an aqueous solution at 80 ° C. containing 0.1% by mass of triethylamine to inactivate the catalyst. Further, after separation, washing and drying, a crude polyacetal copolymer was obtained.

Next, 4 parts by mass of a 5% by mass aqueous solution of triethylamine and pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate were added to 100 parts by mass of this crude polyacetal copolymer. ] Was added in an amount of 0.03 parts by mass and melt-kneaded at 210 ° C. using a twin-screw extruder to remove unstable portions.

Pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] was further added to 100 parts by mass of the branched or crosslinked polyacetal copolymer obtained by the above method as a stabilizer. .3 parts by mass and 0.15 parts by mass of melamine were added and melt-kneaded at 210 ° C. using a twin-screw extruder to obtain a pellet-shaped branched polyacetal copolymer. Table 1 shows the results of evaluation by the method described later.

[Comparative Examples 1 to 4]
As shown in Table 2, when the sodium content of the aliphatic glycidyl ether compound (C) is out of the specification of the present embodiment, the value of the formula (b + c + d) / a is out of the specification of the present embodiment, and the like. Table 2 shows the results of obtaining and evaluating pellet-shaped polyacetal copolymers in the same manner as in Examples.

The abbreviations of the components shown in Tables 1 and 2 have the following meanings.
[Cyclic acetal compound having an oxyalkylene group having 2 or more carbon atoms in the ring]
DO; 1,3-dioxolane [aliphatic glycidyl ether compound]
TPTGE; trimethylolpropane triglycidyl ether GTGE; glycerol triglycidyl ether PETGE; pentaerythritol tetraglycidyl ether Each aliphatic glycidyl ether compound is produced by different synthetic methods to obtain multiple species having different sodium contents. rice field.

[Sodium content]
The sodium content of the aliphatic glycidyl ether compound was measured by the following method. 1 g of the measurement sample was weighed in a platinum crucible and heated with an electric stove to decompose and volatilize the organic components in the crucible, and then heated at 600 ° C. for 1 hour in an electric furnace. After cooling, the inside of the crucible was washed with 3.5% by mass hydrochloric acid, and the cleaning solution diluted to 25 mL with 3.5% by mass hydrochloric acid was used as a sample for inductively coupled plasma emission spectroscopy. , The amount of sodium was quantified, and the amount of sodium in the measurement sample was determined.

[Total amount of water in component (A), component (B), and component (C)]
The water content of the mixed solution of the component (A), the component (B), and the component (C) was measured by the curl fisher method.

[Total amount of methanol in component (A), component (B), and component (C)]
The amount of methanol in the mixed solution of the component (A), the component (B), and the component (C) was measured by a gas chromatography method.

<Evaluation>
The flexural modulus, impact resistance and thermal stability of the pellet-shaped polyacetal copolymer according to Examples and Comparative Examples were evaluated as follows.
[Rigidity (flexural modulus)]
Using an injection molding machine (“SE100DU” manufactured by Sumitomo Heavy Industries, Ltd.), test pieces (4 mm × 10 mm × 80 mm) from pellets in Examples and Comparative Examples under the conditions of cylinder temperature: 205 ° C and mold temperature: 90 ° C. ) Was molded. Then, the flexural modulus of the test piece was measured according to ISO178.
[Impact resistance (Charpy impact strength)]
Using the above injection molding machine, notched Charpy test pieces according to ISO179 / IeA were molded from the pellets in Examples and Comparative Examples. Then, according to ISO179 / IeA, the Charpy impact test value at 23 ° C. was measured.
[Thermal stability (degree of discoloration when melting and staying in the molding machine)]
Using the above injection molding machine, the pellets in Examples and Comparative Examples were allowed to stay in a cylinder set at 220 ° C. for 2 hours, and then a flat plate having dimensions of 50 × 70 × 3 (mm) was formed to form the molded product. The appearance was evaluated. That is, the hue (L, a, b) of the molded product was measured with a Z-300A color sensor manufactured by Nippon Denshoku Kogyo Co., Ltd., and the deviation (ΔE) from the initial hue was calculated by the following formula.
ΔE = [(L ₁ − L ₀ ) ² + (a ₁ − a ₀ ) ² + (b ₁ − b ₀ ) ² ] ^1/2
L, a, and b are color values measured by a color difference meter, respectively, the subscript 1 of L, a, and b means the hue after staying for 2 hours, and 0 means the hue in the normal cycle. do.

From Tables 1 and 2, in Examples 1 to 10, the examples 1 to 10 have sufficient rigidity (flexural modulus of 2800 MPa or more), excellent impact resistance (charpy impact strength of 9 kJ / m ² or more), and thermal stability (sharpy impact strength of 9 kJ / m 2 or more). It was shown that a polyacetal copolymer having a low melt retention discoloration degree (2.5 or less) can be produced. On the other hand, in Comparative Examples 1 to 4, although the rigidity was comparable to that of Examples, it was inferior in at least one of impact resistance and thermal stability. In particular, Examples 1, 3, 5 and 10 and Comparative Example 1, Example 8 and Comparative Example 3 differ only in the sodium content of the aliphatic glycidyl ether compound, but from their comparison, the sodium content is high. It can be seen that the thermal stability is inferior unless it is within a predetermined range. Further, in Example 2 and Comparative Example 2, Example 9 and Comparative Example 4, the content of the linear formal compound, that is, whether or not the formula (b + c + d) / a = 4.5 to 9 μmol / g is satisfied, respectively. However, it can be seen from their comparison that both rigidity and impact resistance cannot be satisfied unless the above equation is satisfied.

Claims (3)

100 parts by mass of trioxane (A), 0.05 to 5 parts by mass of a cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in a ring, trimethylolpropane triglycidyl ether, glycerol triglycidyl ether and penta. An aliphatic glycidyl ether compound (C) 0.001 to 0.5 part by mass, which is one or more selected from the group consisting of erythritol tetraglycidyl ether and has a sodium content of 0.1 to 100% by mass, has a molecular weight. Including the step of performing copolymerization in the presence of the linear formal compound (D) as a regulator.
In the step, the total mass (g) of the (A), (B) and (C) is included in a, the number of moles of the (D) is included in b, and the (A), (B) and (C) are included. A method for producing a polyacetal copolymer, which is set so as to satisfy (b + c + d) / a = 4.5 to 9 μmol / g, where c and d are the total number of moles of water and methanol, respectively. The method for producing a polyacetal copolymer according to claim 1, wherein the linear formal compound (D) is at least one selected from the group consisting of methylal, etylal and dibutoxymethane. A polyacetal copolymer obtained by the method for producing a polyacetal copolymer according to claim 1 or 2.