JP3101766B2 - Polyoxymethylene copolymer composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyoxymethylene copolymer composition. More specifically, the present invention relates to a highly stable polyoxymethylene copolymer composition having a limited terminal group composition.

[Prior Art] A polyoxymethylene copolymer is usually obtained by copolymerizing formaldehyde or trioxane with a cyclic ether. U.S. Pat. No. 3,027,352 describes a copolymer obtained by cationically copolymerizing trioxane with ethylene oxide and 1,3-dioxolane.

U.S. Pat. No. 3,337,503 discloses the use of methylal as a molecular weight regulator during the polymerization of trioxane. When methylal is used as a molecular weight regulator, the terminal group of the obtained polymer becomes a methoxy group.

During the polymerization using a cationic catalyst of formaldehyde and trioxane, a hydride shift (hydrogen abstraction reaction) occurs, the main chain of the polymer is cut, and a high molecular weight polymer cannot be obtained. Moreover, the cleaved end is
It is known that it becomes a methoxy group and a formate group.

On the other hand, during the copolymerization of trioxane and an alkylene oxide such as ethylene oxide, if a compound having a hydroxyl group such as water, methanol or formic acid is present, they function as a chain transfer agent and form an unstable terminal structure. Usually, a method is employed in which these unstable terminal structures are decomposed by post-treatment after polymerization to stabilize the terminal groups as hydroxyethoxy groups, but in the case of formic acid, further terminal formate groups are simultaneously formed. Is done. If the amount of the terminal formate group in the polymer is large, a polymer having excellent stability cannot be obtained.

[Problems to be Solved by the Invention] As described above, the polyoxymethylene copolymer synthesized by the conventional technique is a chain transfer reaction by formic acid which is an impurity in trioxane during polymerization, and a side reaction by a cation catalyst. A terminal formate group was formed by the hydride shift reaction, and it was difficult to reduce the terminal formate group.

The present invention relates to a polyoxymethylene copolymer composition having excellent stability. More specifically, the present invention relates to a polyoxymethylene copolymer composition having particularly excellent long-term heat resistance and hot water resistance.

Means and Action for Solving the Problems The present inventors have conducted intensive studies on the stability of polyoxymethylene, and as a result, by reducing the amount of terminal formate groups of the polyoxymethylene copolymer to a certain range or less, The present inventors have found that a polyoxymethylene copolymer having extremely excellent stability, particularly excellent long-term heat resistance and hot water resistance, can be obtained, and the present invention has been developed.

That is, the present invention is the presence of a perfluoroalkylsulfonic acid or a derivative thereof, with formaldehyde or trioxane, oxymethylene unit molecular weight obtained by copolymerization of a cyclic ether or cyclic formal is 10,000 to 200,000 (-CH ₂ O- ) And an oxyalkylene unit (R ₀ , R ₀ ′: same or different, selected from hydrogen, alkyl group, aryl group, and further bonded to different carbon atoms
R ₀ and R ₀ ′ bonded to different carbon atoms are respectively the same or different and are selected from hydrogen, an alkyl group, and an aryl group. n is an integer of 1 or more, m = 2 to 6), a polyoxymethylene copolymer having an absorbance (D ₁₇₁₀ ) attributable to the end group formate attributable to the methylene group in infrared spectroscopic measurement of the polymer. With respect to 100 parts by weight of the polyoxymethylene copolymer in the range represented by D ₁₇₁₀ / D ₁₄₇₀ ≦ 0.025, preferably 0.02 with respect to the absorbance (D ₁₄₇₀ ) of: a. Alkali metal oxide, alkaline earth metal oxide An ion adsorbent containing at least two oxides selected from oxides of trivalent and tetravalent elements as main components.

Or b. The general formula _{M1 1-x M2 x (OH} ) 2 A n- x / n · mH 2 O ( provided that wherein M1 represents at least one divalent metal selected from alkaline earth metals, M2 Represents a trivalent metal, and A ^n-
Represents an n-valent anion. X is 0 <x ≦ 0.5, and m is a positive number. The present invention relates to a polyoxymethylene copolymer composition having excellent stability, comprising 0.01 to 5.0 parts by weight of at least one selected from the ion adsorbents represented by the following formula:

 Next, the present invention will be described specifically.

The polyoxymethylene copolymer of the present invention comprises a compound represented by the general formula: (R ₀ , R ₀ ′: same or different, selected from hydrogen, alkyl group, aryl group, and further bonded to different carbon atoms
R ₀ and R ₀ ′ bonded to different carbon atoms are respectively the same or different and are selected from hydrogen, an alkyl group, and an aryl group. m = 2 to 6), or a cyclic ether represented by the general formula (R ₀ , R ₀ ′: same or different, selected from hydrogen, alkyl group, aryl group, and further bonded to different carbon atoms
R ₀ and R ₀ ′ bonded to different carbon atoms are respectively the same or different and are selected from hydrogen, an alkyl group, and an aryl group. m = 2 to 6) can be obtained by copolymerization with a cyclic formal represented by the following formula (3) using a cationic catalyst.

Examples of the cyclic ether used for obtaining the polymer of the present invention include ethylene oxide, propylene oxide, butylene oxide, and styrene oxide.

Examples of the cyclic formal include ethylene glycol formal (1,3-dioxolane), diethylene glycol formal, 1,3-propanediol formal, 1,4-butanediol formal, 1,5-pentanediol formal, and 1,6-hexane. Diol formal and the like. A particularly preferred comonomer is ethylene glycol formal (1,3-dioxolane).

As the cationic polymerization catalyst used for obtaining the polymer of the present invention, perfluoroalkylsulfonic acid or a derivative thereof is suitable. Specific examples include trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, anhydrides of these superacids, and alkyl esters of superacids. The concentration of the catalyst is preferably low as long as the polymerization activity is sufficient. When the catalyst concentration is high, the catalyst remaining in the polymer causes depolymerization, so that the thermal stability decreases. In the present invention, the catalyst concentration is preferably in the range of 1 × 10 ⁻⁶ to 2 × 10 ⁻⁵ mol% based on the main monomer.

The present inventors have found that when perfluoroalkylsulfonic acid or a derivative thereof is used as a cationic polymerization catalyst, Lewis acids such as boron trifluoride, which is a cationic polymerization catalyst usually used for the polymerization or copolymerization of trioxane, are used. It was found that hydride shift, which is a side reaction during polymerization, was specifically suppressed as compared with the catalyst.

This means that the production of a polyoxymethylene polymer having a higher molecular weight, which has conventionally been difficult in cationic polymerization due to side reactions during the polymerization, becomes easier.

After the polymerization, the catalyst contained in the polymerized polymer causes depolymerization.In general, in order to deactivate the catalyst, the catalyst is brought into contact with an aqueous solution containing a basic substance such as triethylamine, an organic solvent, or the basic substance. It is neutralized and deactivated by adding and mixing. The present inventors have also found that deactivation by adding and mixing a crystalline acid adsorbent composed of at least two or more metal oxides or metal hydroxides is extremely effective. Was. More specifically, based on 100 parts by weight of the polyoxymethylene copolymer, a. At least two kinds of oxides selected from alkali metal oxides, alkaline earth metal oxides, oxides of trivalent and tetravalent elements are mainly used. Ion adsorbent as a component.

Or b. The general formula _{M1 1-x M2 x (OH} ) 2 A n- x / n · mH 2 O ( provided that wherein M1 represents at least one divalent metal selected from alkaline earth metals, M2 Represents a trivalent metal, and A ^n-
Represents an n-valent anion. X is 0 <x ≦ 0.5, and m is a positive number. ) At least one selected from the ion adsorbents represented by the formula (1) is added in an amount of 0.01 to 5.0 parts by weight, more preferably 0.01 to 1 part by weight, and melt-mixed. here,
Examples of the alkali metal oxide include Na ₂ O, K ₂ O, etc., and examples of the alkaline earth metal oxide include MgO, Ca
O and the like, and examples of the oxides of trivalent and tetravalent elements include Al ₂ O ₃ , SiO ₂ and TiO ₂ . As an ion adsorbent mainly composed of at least two kinds of oxides selected from these oxides, specifically, 2.5 MgO.Al ₂ O ₃ .nH ₂
O, 2MgO ・ 6SiO ₂・ nH ₂ O, Al ₂ O ₃・ 9SiO ₂・ nH ₂ O, Al ₂ O ₃・ N
a ₂ O.2CO ₃ .nH ₂ O, Mg _0.7 Al _0.3 O _{1.15 and the} like.
In the general formula _{M1 1-x M2 x (OH} ) 2 A n- x / n · mH 2 O, M1
Examples of Mg, Ca, etc., and examples of M2 include B, Al, Ga, In,
Ti, Tl etc., A CO ₃ ^2- Examples of ^{_{n-, OH -, HCO 3 -}} , H 2 PO 4 -, NO 3
^-, I ^-, salicylic acid ion ^-, citrate ^-, tartrate ^- and the like are. A particularly preferred example is CO ₃
^2-, OH ^-, and the like. Specific examples of this type of ion adsorbent include natural hydrotalcite represented by Mg _0.75 Al _0.25 (OH) ₂ CO _{3 0.125} 0.5 H ₂ O, and Mg _4.5 Al ₂ (OH) ₁₃ CO _3.
There is a synthetic hydrotalcite represented by 3.5H ₂ O or the like.

Alcohols and ethers are preferred as the molecular weight regulator, and alkyl ethers such as methylal are most preferred. In addition, water, formic acid, methyl formate and the like are also effective as molecular weight regulators.
Methyl formate is not preferred because it forms a terminal formate group. In addition, water is not preferred because it forms unstable terminal hydroxyl groups. Therefore, when water, formic acid, or methyl formate is contained as an impurity in the monomer, it is necessary to purify the monomer prior to polymerization to reduce these impurities as much as possible. Preferred amounts of water, formic acid, and methyl formate in the monomer are 40 ppm or less, respectively.

The molecular weight of the polymer of the present invention ranges from 10,000 to 200,000. If the molecular weight is less than 10,000, sufficient mechanical properties cannot be obtained. On the other hand, when the molecular weight is 200,000 or more, processability such as molding and extrusion is remarkably reduced, which is not practical.

In the present invention, the terminal group structure and terminal group composition of the polymer are extremely important points.

In the present invention, the terminal group of the polymer includes an alkoxy group such as a methoxy group (—OCH ₃ ), a hydroxyalkoxy group, and the like. (R ₀ , R ₀ ′: same or different, selected from hydrogen, alkyl group, aryl group, and further bonded to different carbon atoms
R ₀ and R ₀ ′ bonded to different carbon atoms are respectively the same or different and are selected from hydrogen, an alkyl group, and an aryl group. m = 2-6), which is a formate group. The terminal groups other than these, for example, the hydroxyl group added to the oxymethylene unit, are very unstable and must be decomposed and removed by a post-treatment after polymerization, for example, by heating in the presence of an alkaline substance to form a hydroxyalkoxy group. Must.

In the present invention, the amount of formate is the most important point in these terminal groups. The amount of formate end groups in the copolymer can be measured by infrared spectroscopy of a film obtained by hot pressing the polymer. The absorption wave number (ν) due to the terminal formate is 1710 cm ⁻¹ , and the absorption wave number (ν) due to the methylene group of the polyoxymethylene main chain is
It is 1470cm ^-1 . The amount of terminal formate groups in the copolymer can be represented by the ratio of these absorbances, D ₁₇₁₀ / D ₁₄₇₀ .

The amount of formate groups of the copolymer in the present invention is D ₁₇₁₀ /
D ₁₄₇₀ must be 0.025 or less, more preferably 0.020 or less. If D ₁₇₁₀ / D ₁₄₇₀ is more than this,
The heat aging characteristics and the hot water resistance of the copolymer are reduced.

EXAMPLES Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the examples.

 The measurement items in the examples are as follows.

1. Terminal formate: hot-press the copolymer at 200 ° C,
Form a film of μ. The infrared absorption spectrum of the obtained film was measured, and the absorbance at ν = 1710 cm ⁻¹ and ν = 14
The ratio of the absorbance at 70 cm ^-1 D ₁₇₁₀ / D ₁₄₇₀ is calculated.

2. Oxyalkylene unit insertion amount: 100 g of copolymer 10 g
It is put in a 3N HCl aqueous solution and heated in a sealed container at 120 ° C. for 2 hours to decompose. After cooling, the amounts of the alkylene glycol, dialkylene glycol, and trialkylene glycol in the aqueous solution are measured by gas chromatography (FID), and the amount of the oxyalkylene unit is represented by mol% based on the oxymethylene unit of the copolymer.

3. Based on MI: ASTM D-1238-86.

4. Thermal stability: Resin is retained in an injection molding machine (Arbour All Launder 100, manufactured by Western Trading Co., Ltd.) with a cylinder temperature of 230 ° C to form a molded piece of 12 x 120 x 3 mm and molded piece. The time (min) at which silver streaks occur on the surface is determined. The higher the value, the better the thermal stability of the polymer.

5. Heat-resistant aging: A tensile test specimen based on ASTM D-638 was placed in a 140 ° C. gear oven (manufactured by Tabai Seisakusho, GPS-222).
(Type) and evaluated. The measurement item is the tensile strength retention.

6.Hot water: a tensile test specimen based on ASTM D-638
It was immersed in hot water (flowing water type) adjusted to 120 ° C and evaluated.
The measurement item is the tensile strength retention.

[Example-1] Highly purified trioxane (water in trioxane ≤
2000 g, 1,3-dioxolane (5 mol% based on trioxane), and methylal (0.2 mol% based on trioxane) are put into a jacketed kneader having two Σ blades and heated to 70 ° C. Warmed. Then, a solution of trifluoromethanesulfonic acid in dioxane (0.002 mol /
) Was added at a concentration of 5 × 10 ⁻⁶ mol% of solifluoromethanesulfonic acid with respect to trioxane to carry out polymerization. After 15 minutes from the start of the reaction, cold water was poured into the jacket and cooled under a nitrogen atmosphere. One hour later, the contents of the kneader were removed and Mg _0.75 Al _0.25 O _1.125 (Kyoward KW2300 Kyowa Chemical) was obtained as a deactivator.
Add 1wt% and use a vented twin screw extruder to
Extruded at 00 ° C. Further, 1 part by weight of triethylamine, 5 parts by weight of water, 2,2-
0.2 parts by weight of methylenebis- (4-methyl-6-t-butylphenol) was added and extruded with a vented single-screw extruder (extrusion temperature 200 ° C., vent pressure 200 torr).
r). Terminal formate of the obtained copolymer, insertion amount of oxyalkylene unit, MI, thermal stability, heat aging,
The hot water resistance was evaluated. The results are shown in Table 1. For both heat aging and hot water resistance, the retention of tensile strength after 2000 hours was 80% or more.

[Examples 2 to 17] In the same manner as in Example 1, the catalyst concentration, the amount of 1,3-dioxolane, the amount of methylal, the type of comonomer, and the like were changed to obtain polyoxyethylene under the conditions shown in Table 1. A methylene copolymer was synthesized. The obtained polymer was subjected to the same treatment as in Example 1, and the same evaluation was performed. Table-Results
It is shown in FIG. All were excellent in heat-resistant aging and hot-water resistance as in Example 1, and the tensile strength retention after 2,000 hours passed was 80% or more.

[Comparative Examples 1 to 7] Using the apparatus of Example 1, replacing trifluoromethanesulfonic acid as a polymerization catalyst with boron trifluoride dibutyl etherate (0.02 mol / L benzene solution) and using a catalyst concentration of trioxane In the same manner as in Example 1, except that 5 × 10 ⁻³ mol% was added, the amount of comonomer and the amount of methylal as a molecular weight regulator were variously changed, and the polyoxymethylene copolymer was polymerized. -1 and melt-mixed with a quencher. The obtained polymer was treated in the same manner as in Example 1 and evaluated. The results are shown in Table 1. Both of them were inferior to the examples in both heat aging and hot water resistance, and the tensile strength retention after 2,000 hours passed was 50% or less.

[Comparative Examples-8 and 9] A method similar to that of Example-1, except that the polyoxymethylene copolymer was polymerized under the conditions of Example-5, and the cooling after the polymerization was performed in a nitrogen atmosphere containing 1 vol% of Air. With the above, a polyoxymethylene copolymer was obtained. The obtained polymer was evaluated in the same manner as in Example-1. The results are shown in Table 1. Both are inferior to the examples in both heat aging and hot water resistance,
The tensile strength retention after lapse of 2000 hours was 50% or less.

[Examples 18 to 23] The polyoxymethylene copolymer was polymerized under the conditions of Example 3, and the deactivator shown in Table 2 was used as the deactivator after polymerization, in the same manner as in Example 3. , Melt-mixed. The obtained polymer was subjected to the same treatment as in Example 3, and the same evaluation was performed. Table 2 shows the results. Examples-
Similar to 1, excellent in both heat aging and hot water resistance,
The tensile strength retention after lapse of 2000 hours was 80% or more.

[Example-24] A cross section having a partially overlapped circle with an inner diameter of 50 mm, and L / D = 14
A continuous mixing reactor (KRC-Kneader, manufactured by Kurimoto Steel Works Co., Ltd.) consisting of a barrel with a jacket through which heat medium can pass through the outside and two rotating shafts with a number of paddles meshing with each other inside. ), Using a jacket temperature of 80
C., 78 rpm, trioxane (2 kg / h), 1,3-dioxolane (5 mol% based on trioxane), methylal (0.3 mol% based on trioxane), and trifluoromethanesulfonic acid in dioxane (0.002 mol / ) With trifluoromethanesulfonic acid is 5 to trioxane.
Polymerization was carried out by continuously supplying the solution to a concentration of × 10 ^-6 mol%. The polymer discharged from the polymerization machine is taken out under a nitrogen atmosphere, and then the polymer is added as a deactivator with Mg _0.75 Al _0.25 O
_1.125 (Kyoward KW2300 Kyowa Chemical) was added in an amount of 0.1 wt% to the polymer, and extruded at 200 ° C. using a vented twin screw extruder. Further, based on 100 parts by weight of the obtained polymer, 1 part by weight of triethylamine, 5 parts by weight of water,
0.2 parts by weight of 2-methylenebis- (4-methyl-6-t-butylphenol) was added and extruded with a vented single-screw extruder (extrusion temperature 200 ° C., vent pressure 200 torr).
r). The obtained copolymer was evaluated in the same manner as in Example-1. Table 2 shows the results. For both heat aging and hot water resistance, the retention of tensile strength after 2000 hours was 80% or more.

[Comparative Example-10] Using the same polymerization apparatus as in Example-24, using boron trifluoride dibutyl etherate (0.02 mol / L benzene solution) instead of trifluoromethanesulfonic acid as the polymerization catalyst, and changing the catalyst concentration to trioxane. 5 × 10 ^-3 mol%
The polyoxymethylene copolymer was polymerized under the same conditions as in Example 23, except that the mixture was continuously supplied. The polymer from the polymerization machine was taken out into an aqueous solution of triethylamine having a diameter of 5% by weight to deactivate the polymerization catalyst. The obtained polymer was filtered and dried by heating (135 ° C.) under a nitrogen stream. Next, as in Example 23, 1 part by weight of triethylamine, 5 parts by weight of water, and 0.2 part of 2,2-methylenebis- (4-methyl-6-t-butylphenol) were added to 100 parts by weight of the obtained polymer.
Parts by weight were added and extruded with a vented single screw extruder (extrusion temperature 200 ° C, vent pressure 200 torr). The obtained copolymer was evaluated in the same manner as in Example-23. Table 2 shows the results.
Shown in In both the heat aging and the hot water resistance, the retention of tensile strength after 2000 hours was 50% or less.

[Effect of the Invention] The copolymer composition of the present invention has strength, rigidity, fatigue properties,
It is excellent in friction and wear properties, thermal stability, etc., and uses where conventional polyoxymethylene homopolymers and copolymers have been used, such as cams, gears, switches, handles, levers, reels, hubs, bearings, etc. It can be used for various mechanical parts, various miscellaneous parts such as fasteners, buttons, clips, and many other automobiles, electric and electronic parts. In addition, taking advantage of the excellent properties of the present copolymer composition, pump impeller, pump casing, shower nozzle,
It can be used for parts around water such as faucets. In addition, processing such as an extruded rod, a sheet, and a blow is also possible. In addition, conventionally known additives, for example, various antioxidants, heat stabilizers, pigments, nucleating agents, antistatic agents, weathering agents, and the like,
Addition of various reinforcing materials such as carbon fiber, glass fiber, glass beads, talc, mica,
Can be blended. In addition, polymer blends and polymer alloys with polyurethane, PMMA, PE, etc. are possible.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-18511 (JP, A) JP-A-57-30715 (JP, A) JP-A-57-12018 (JP, A) JP-A 49-185 23294 (JP, A) JP-A-63-56552 (JP, A) JP-A-57-192448 (JP, A) JP-A-59-93717 (JP, A) JP-B-48-8759 (JP, B1) JP-B-47-49833 (JP, B1) JP-B-43-8883 (JP, B1) JP-B-44-11144 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 2/00-2/38 C08L 59/04

Claims (2)

(57) [Claims] 1. A perfluoro presence of alkyl sulfonic acid or a derivative thereof, with formaldehyde or trioxane, a cyclic ether or oxymethylene unit molecular weight obtained by copolymerization of cyclic formal is 10,000 to 200,000 (-CH ₂ O- ) And an oxyalkylene unit (R ₀ , R ₀ ′: same or different, selected from hydrogen, alkyl group, aryl group, and further bonded to different carbon atoms
R ₀ and R ₀ ′ bonded to different carbon atoms are respectively the same or different and are selected from hydrogen, an alkyl group, and an aryl group. n is an integer of 1 or more, m = 2 to 6), a polyoxymethylene copolymer having an absorbance (D ₁₇₁₀ ) attributable to the end group formate attributable to the methylene group in infrared spectroscopic measurement of the polymer. With respect to 100 parts by weight of the polyoxymethylene copolymer within the range represented by D ₁₇₁₀ / D ₁₄₇₀ ≦ 0.025 with respect to the absorbance (D ₁₄₇₀ ), a. Alkali metal oxide, alkaline earth metal oxide, trivalent And an ion adsorbent containing at least two oxides selected from oxides of tetravalent elements. Or b. The general formula _{M1 1-x M2 x (OH} ) 2 A n- x / n · mH 2 O ( provided that wherein M1 represents at least one divalent metal selected from alkaline earth metals, M2 Represents a trivalent metal, and A ^n-
Represents an n-valent anion. X is 0 <x ≦ 0.5, and m is a positive number. A polyoxymethylene copolymer composition comprising 0.01 to 5.0 parts by weight of at least one selected from the ion adsorbents represented by the formula: 2. The absorbance (D ₁₇₁₀ ) due to the terminal group formate of the polyoxymethylene copolymer is D ₁₇₁₀ / D ₁₄₇₀ ≦ 0.02 with respect to the absorbance (D ₁₄₇₀ ) due to the methylene group.
The polyoxymethylene copolymer composition according to claim 1, wherein: