JPH0598027A - Polyoxymethylene gear - Google Patents

Abstract

PURPOSE:To provide a polyoxymethylene gear improved in durability in an atmosphere in contacted with hot water, steam or a basic solution by introducing oxyalkylene units into a polymer comprising repeating oxymethylene units. CONSTITUTION:Formaldehyde or trioxane and a cyclic ether of formula I (wherein R and R0 are each H, alkyl, allyl, R and R0 bonded to the C atom may be the same or different and are each H, alkyl or allyl; and n is 2-6) or a cyclic formal of formula II are copolymerized together at 60-200 deg.C for 10 sec to 100min in the presence of a cationic polymerization catalyst. The catalyst is deactivated by contact with a basic substance to obtain an oxymethylene polymer having a structure derived by introducing 0.07-0.5mol, per 100mol of oxymethylene units, oxyalkylene units of formula II into a polymer comprising repeating oxymethylene units, having a molecular weight of 10000-200000 and terminated with alkoxy, hydroalkoxy or formate groups. This polymer is molded into a gear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyoxymethylene gear having excellent durability. More specifically, the present invention relates to a gear made of polyoxymethylene, which has excellent durability particularly in an atmosphere in contact with hot water, steam or a basic solution.

[0002]

2. Description of the Related Art Polyoxymethylene is widely used as a gear component because it has well-balanced mechanical properties and excellent fatigue properties. However, the conventional gear made of polyoxymethylene homopolymer has excellent durability when used in a normal atmosphere, but when used in an atmosphere that is exposed to hot water, steam, or a basic solution for a long time, the polymer is used. Its own hydrolysis causes poor durability. This is because the terminal of the conventional polyoxymethylene homopolymer is stabilized with an acetyl group. On the other hand, the conventional gear made of polyoxymethylene copolymer is excellent in stability in an atmosphere exposed to hot water, water vapor or a basic solution for a long time, but its durability as a gear is not sufficient.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyoxymethylene gear having excellent durability, which is suitable for use in an atmosphere exposed to hot water, steam or a basic solution for a long period of time. Especially.

[0004]

The polyoxymethylene gear of the present invention is characterized in that it comprises a polyoxymethylene copolymer having a specific main chain composition and a terminal group. That is, the present invention relates to a polymer composed of repeating oxymethylene units (—CH ₂ O—) containing oxyalkylene units.

[0005]

[Chemical 2]

(R and R ₀ may be the same or different and are selected from hydrogen, an alkyl group and an allyl group, and R and R ₀ bonded to different carbon atoms may be the same or different and each is hydrogen, Selected from an alkyl group and an allyl group, n is an integer of 1 or more, and m is an integer of 2 to 6) per 100 mol of oxymethylene units.
This is a gear having a structure in which 07 to 0.5 mol is inserted, and the end group of the polymer is a polyoxymethylene copolymer having an alkoxy group, a hydroalkoxy group, and a formate group.

In the present invention, one of the important points is the amount of polyalkylene units in the polyoxymethylene copolymer. The insertion rate of oxyalkylene units in the polyoxymethylene copolymer is 100 oxymethylene units.
It is selected from the range of 0.07 to 0.5 mol, and more preferably 0.1 to 0.3 mol per mol. When the insertion rate of oxyalkylene units is less than 0.07 mol,
Durability is reduced in an atmosphere exposed to hot water, steam, or a basic solution for a long period of time. On the other hand, when the insertion rate of oxyalkylene units exceeds 0.5 mol, the durability of gear strength is significantly reduced even in a normal atmosphere.

The oxyalkylene units are preferably dispersed alone in the copolymer as long as they can be formed without forming a block. Regarding n representing the sequence of oxyalkylene units, it is preferable that the ratio of n = 1 is 95 mol% or more of the whole oxyalkylene units and the ratio of n ≧ 2 is 5 mol% or less of the whole oxyalkylene units. n = 1
Those having a ratio of over 95 mol% have excellent durability.

The insertion amount and sequence of these oxyalkylene units can be determined by subjecting the polymer to thermal decomposition in a 3N HCl aqueous solution and analyzing the alkylene glycol, dialkylene glycol, and trialkylene glycol in the decomposition solution. it can. In addition, the terminal group of the polyoxymethylene copolymer is one of the important factors.

In the present invention, polyoxymethylene copolymer
Is a methoxy group (-OCH ₃) Etc. alkoxy
Group, a hydroxyalkoxy group represented by the following formula

[0011]

[Chemical 3]

(R and R ₀ may be the same or different and are selected from hydrogen, an alkyl group and an allyl group, and R and R ₀ bonded to different carbon atoms may be the same or different, and , An alkyl group, an allyl group, m is an integer of 2 to 6, or a formate group. A terminal group other than these, for example, a hydroxyl group added to an oxymethylene unit is extremely unstable and is decomposed and removed by a post-treatment after polymerization, for example, thermal decomposition in the presence of an alkaline substance to become a hydroxyalkoxy group.

The amount of formate end groups in the polyoxymethylene copolymer can be measured by infrared spectroscopy of the 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 1470 cm ⁻¹ . The amount of terminal formate groups in the copolymer can be expressed by the ratio of these absorbances D ₁₇₁₀ / D ₁₄₇₀ .

The amount of formate groups in the copolymer in the present invention is 0.025 or less, more preferably 0.020 or less, as D ₁₇₁₀ / D ₁₄₇₀ . D ₁₇₁₀ / D ₁₄₇₀ is 0.
When it exceeds 025, the durability of the gear in an atmosphere exposed to hot water, steam or a basic solution for a long period of time deteriorates. Next, a method for producing the polyoxymethylene copolymer, which is a raw material of the gear of the present invention, will be described.

The polyoxymethylene copolymer is a compound of the general formula

[0016]

[Chemical 4]

(R and R ₀ may be the same or different and are selected from hydrogen, an alkyl group and an allyl group, and R and R ₀ bonded to different carbon atoms may be the same or different, and , An alkyl group, an allyl group, m is an integer of 2 to 6), or a general formula

[0018]

[Chemical 5]

(R and R ₀ may be the same or different and are selected from hydrogen, an alkyl group and an allyl group, and R and R ₀ bonded to different carbon atoms may be the same or different, and each is hydrogen. , An alkyl group, an allyl group, and m is an integer of 2 to 6) can be copolymerized with a cyclic catalyst.

Examples of the cyclic ether used to obtain the polyoxymethylene copolymer 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,
Examples thereof include 1,3-propanediol formal, 1,4-butanediol formal, 1,5-pentanediol formal, and 1,6-hexanediol formal. Preferred comonomers are cyclic formal such as ethylene glycol formal (1,3-dioxolane) and 1,4-butanediol formal.

The cationic polymerization catalyst used to obtain the polyoxymethylene copolymer as the raw material of the gear of the present invention, that is, the polyoxymethylene copolymer having a limited main chain composition and terminal group, is Fluoroalkyl sulfonic acids or their derivatives are suitable. Specifically, for example, trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, heptafluoropropanesulfonic acid,
Nonafluorobutanesulfonic acid, undecafluoropentanesulfonic acid, perfluoroheptanesulfonic acid, etc.
As the derivative, trifluoromethanesulfonic anhydride, pentafluoroethanesulfonic anhydride, heptafluoropropanesulfonic anhydride, nonafluorobutanesulfonic anhydride, undecafluoropentanesulfonic anhydride, perfluoroheptanesulfonic acid. Super strong acid anhydrides such as anhydrides, or methyl trifluoromethanesulfonate, ethyl trifluoromethanesulfonate, methyl pentafluoroethanesulfonate, alkyl esters of superstrong acids such as methyl heptafluoropropanesulfonate, or trimethylsilyl trifluoromethanesulfonate, Examples thereof include alkylsilyl esters of super strong acids such as triethylsilyl trifluoromethanesulfonate.

In this case, the catalyst concentration is preferably in the range of 1 × 10 ^-6 to 2 × 10 ^-5 mol% with respect to the main monomer. Lewis acids which are usually used as catalysts for the polymerization or copolymerization of trioxane, such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, phosphorus pentachloride and the compounds or salts thereof can also be used. However, when these catalysts are used, the ratio of n = 1 representing the sequence of the oxyalkylene units of the resulting copolymer is 95 mol% or more of the entire oxyalkylene units, and the terminal formate of the copolymer. It is difficult to set the group concentration D ₁₇₁₀ / D ₁₄₇₀ to 0.025 or less.

Alcohols and ethers are preferred as the molecular weight regulator during polymerization, and alkyl ethers such as methylal are most preferred. The molecular weight of the polyoxymethylene copolymer used as the raw material of the gear of the present invention is 10.000-2.
A range of 0,000 is preferred. Molecular weight 10,000
If it is less than the above range, sufficient durability is difficult to obtain, and if the molecular weight exceeds 200,000, injection molding becomes difficult.

The polymerization apparatus may be either batch type or continuous type and is not particularly limited. As a batch type polymerization apparatus, a reaction tank equipped with a stirrer can be generally used, and as a continuous type apparatus, a self-cleaning type such as a co-kneader, a twin-screw screw type continuous extrusion kneader, a two-axis paddle type continuous mixer A mixer can be used. Polymerization temperature is 6
It can be carried out at 0 to 200 ° C, preferably 60 to 140 ° C. The polymerization time is not particularly limited, but generally 10 seconds or more and 100 minutes or less is selected.

After the polymerization, the catalyst contained in the polymerized polymer undergoes depolymerization, so that the catalyst is usually deactivated. As a method for deactivating a polymerization catalyst, it is common to contact a solution containing a basic substance such as triethylamine with a polymerized polymer or neutralize the acid catalyst by adding a basic substance to the polymerized polymer, but at least two or more kinds It is a very effective method to add and melt-mix the crystalline acid adsorbent composed of the metal oxide or metal hydroxide. More specifically, with respect to 100 parts by weight of the polyoxymethylene copolymer, a. An ion adsorbent containing, as a main component, at least one oxide selected from alkali metal oxides and alkaline earth metal oxides and at least one oxide selected from trivalent and tetravalent element oxides. Or b. General formula M1 _1-x M2 _x (OH) _{2 An} ^- _{x / n} · mH ₂ O (wherein M1 represents at least one divalent metal selected from alkaline earth metals, and M2 is trivalent) Showing metal,
A ^n- represents an n-valent anion.

Further, x is 0 <x≤0.5, and m is positive.
Is a number. ) Selected from the ion adsorbents represented by
0.01 to 5.0 wt% of at least one kind is more preferable.
It is preferable to add 0.01 to 1 wt% and perform melt mixing.
Yes. Here, the alkali metal oxide is Na₂O, K
₂O and the like, and M as an alkaline earth metal oxide.
gO, CaO, etc., and acids of trivalent and tetravalent elements
As the compound, Al₂O₃, SiO₂, TiO₂Etc.
You can At least two kinds selected from these oxides
As an ion adsorbent containing an oxide as a main component, specifically,
2.5 MgO / Al₂O₃・ NH₂O, 2MgO ・ 6S
iO₂・ NH₂O, Al₂O₃・ 9 SiO₂・ NH
₂O, Al₂O₃・ Na₂O ・ 2CO₃・ NH₂O, M
g_0.7Al_0.3O_{1. 15}Etc. In addition, the general formula Ml
_1-xM2_x(OH)₂A^n- _{x / n}・ MH₂At O, M
As an example of 1, Mg, Ca, etc., and as an example of M2,
B, Al, Ga, In, Ti, Tl, etc., A^n-As an example of
Is CO₃ ^2-, OH^-, HCO₃ ^-, H₂PO_Four ^-, NO
₃ ^-, I^-Salicylate^-, Citrate ion^-,Liquor
Stone ion^-Etc. A particularly preferred example is
CO₃ ^2-, OH^-Is mentioned. This kind of ion adsorbent
As a concrete example of_0.75Al_0.25(OH)₂CO
_{30.1 twenty five}・ 0.5H₂Natural hydrotarsai indicated by O
G, Mg_4.5Al₂(OH) ₁₃CO₃・ 3.5H₂O etc.
There is a synthetic hydrotalcite represented by.

The amount of these deactivators added is based on the polymer.
0.001 to 0.5 wt% is preferable, and 0.005 to 0.05 wt% is more preferable. 0.00 0.00
If it is less than 1 wt%, the deactivation of the polymerization catalyst is insufficient, and if the amount added exceeds 0.5 wt%, it is colored during molding and the color tone of the molded product is deteriorated. The particle size of the quenching agent is not particularly limited, but 100 μm in order to improve the dispersibility.
The following are preferred. Further, the quenching agent may be surface-treated in order to improve the dispersibility with the polymer.

The deactivator may be added to the polymerization machine after the completion of the polymerization, or in a continuous polymerization machine, to the latter stage of the polymerization machine, or by adding and mixing to the polymer discharged from the polymerization machine. I can. The polymer to which the quenching agent is added,
Further, by melt-mixing, the polymerization catalyst can be more completely deactivated. Melt mixing is from the melting point of the polymer to 27
It is carried out in the temperature range of 0 ° C. As a melt mixing device,
A single-screw type continuous extruder, a co-kneader, a twin-screw type continuous extruder, etc. may be mentioned.

When the obtained copolymer has an unstable terminal hydroxyl group, the unstable portion is decomposed and removed by heat treatment with a basic substance such as an aqueous solution of triethylamine by a conventionally known method. To do. Further, this operation can be carried out simultaneously with the operation of adding and mixing the catalyst deactivator, or by the same melt mixer. Polyoxymethylene gear of the present invention is a polyoxymethylene copolymer obtained by the above method, if necessary, conventionally known additives, for example, various antioxidants, heat stabilizers,
Pigment, nucleating agent, antistatic agent, lubricant, glass fiber,
It can be obtained by injection molding after kneading various fillers such as carbon fiber, talc and mica. An injection molding machine such as a screw type or a plunger type can be used without particular limitation. Preferred molding conditions are a cylinder temperature of 180 ° C to 230 ° C and a mold temperature of 0 ° C to 120 ° C. For other various conditions,
It can be set according to the size and shape of the gear.

The polyoxymethylene gear of the present invention has excellent durability and can be used in various applications. In particular, it is suitable for gears used in hot water or hot water or a basic solution because of its durability in hot water or a basic solution and no rust.

[0031]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples. The measurement items in the examples are as follows. 1. The terminal formate: copolymer is hot pressed at 200 ° C. to form a 15 μ film. The infrared absorption spectrum of the obtained film is taken and the ratio D ₁₇₁₀ / D ₁₄₇₀ of the absorbance at ν = 1710 cm ⁻¹ and the absorbance at ν = 1470 cm ⁻¹ is calculated. 2. Oxyalkylene unit insertion amount and sequence:
10 g of the copolymer is added to 100 ml of 3N HC1 aqueous solution and heated in a sealed container at 120 ° C. for 2 hours for decomposition. After cooling, the amounts of alkylene glycol, dialkylene glycol and trialkylene glycol in the aqueous solution are measured by gas chromatography (FID), and the amount of oxyalkylene units is expressed by mol% based on the oxymethylene units of the copolymer.

The sequence of oxyalkylene units corresponds to an amount of monoalkylene glycol of n = 1, an amount of dialkylene glycol of n = 2 and an amount of trialkylene glycol of n = 3. 3. Ml: Based on ASTM D-1238-86. 4. Gear durability: A power consumption type gear durability tester was used to evaluate the cumulative number of revolutions leading to destruction.

Measurement conditions: gear shape; module 1, number of teeth 30, tooth width 3 mm, spur gear combination gear; gear rotation speed with the same material and same shape; 1 m / sec (pitch circle) environment; 23 ° C., 50% RH lubrication Unlubricated load torque; 9 kgf-cm, 13.5 kgf-cm 5. Hot water resistance: The gear molded article was evaluated by immersing it in hot water (running water type) adjusted to 120 ° C. The measurement item is the weight retention rate. 6. Base resistance stability: The gear molded product was evaluated by immersing it in a 1N NaOH aqueous solution at 60 ° C. The measurement item is the weight retention rate.

[0034]

[Reference Example] (Production of Polyoxymethylene Copolymer) (1) Production of Sample A Highly produced trioxane (2 p of water in trioxane)
pm, formic acid 3 ppm) 2000 g, 1,3-dioxola
(0.8 mol% relative to trioxane), and methyl
2 pieces of ral (0.2 mol% relative to trioxane)
70 in a kneader with a jacket that has Σ blades
The temperature was raised to ° C. Then of trifluoromethane sulfonic acid
Dioxane solution (0.002 mol / 1) was added to trifluoro
Rhomethanesulfonic acid is 5 × 10 relative to trioxane^-6m
Polymerization was carried out by adding so as to be ol%. After starting the reaction, 1
After 5 minutes, put cold water into the jacket and nitrogen
Cooled under atmosphere. 1 hour later, take the contents of the kneader
Mg as a quenching agent _0.75Al_0.25O_1.125(KW-2
300 Kyowa Kagaku) 0.01 for the polymer obtained
Add 2 wt% and use a vented twin-screw extruder to
Extruded at 00 ° C. Furthermore, 100 weight of the obtained polymer
1 part by weight of triethylamine, 5 parts by weight of water, 2,
2-methylenebis- (4methyl-6-t-butylpheno
Of 0.2% by weight) and a single screw extruder with a vent
(Extrusion temperature 200 ° C, vent pressure 200t
orr). (2) Production of Samples B to E In the same manner as in Sample A, 1,3-dioxolane
Amount of polyoxymethylene copolymer with varying amount and amount of methylal
Was synthesized. The end of the obtained polymer has a methoxy group,
It is composed of an oxyethoxy group and a formate group.

[0035]

Example 1 The terminal formate, the amount of oxyalkylene units inserted, the sequence of oxyalkylene units, and MI of Sample A obtained in Reference Example were evaluated. The results are shown in Table 1. Using the sample A as a raw material, the gear of the module 1 was molded by an injection molding machine. (Cylinder temperature 200
C., mold temperature 40.degree. C.) A pair of molded gears was evaluated for durability by a power consumption type gear durability tester.

Separately, the molded gears were evaluated for hot water resistance and base resistance. Table 2 shows these results. The durability of the gear was good, and the hot water resistance and base stability were also very good.

[0037]

Examples 2 to 5 Sample B was prepared in the same manner as in Example 1.
The same evaluation was performed for ~ E. The results are shown in Tables 1 and 2. In all cases, the durability of the gear was good, and the hot water resistance and base stability were also very good.

[0038]

Comparative Examples 1 and 2 Tenac 5010 (manufactured by Asahi Kasei) and Delrin 50, which are commercially available polyoxymethylene homopolymers
0 (manufactured by Du Pont) was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. The end group of Tenac 5010 is acetate group, Delrin 50
The terminal group of 0 is composed of an acetyl group and a methoxy group.

In all cases, the durability of the gear was good, but the hot water resistance and base resistance were very poor.

[0040]

Comparative Examples 3 and 4 Tenac-C4520 (manufactured by Asahi Kasei) DURACON M, which is a commercially available polyoxymethylene copolymer.
-9002 (manufactured by Polyplastics) was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. Tenac-C 4520, Duracon M-9
The end groups of 002 are methoxy group, oxyethoxy group,
It is composed of formate groups.

In all cases, the hot water resistance and base stability of the gears were good, but the durability was very poor.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

According to the present invention, a gear having excellent durability in an atmosphere in contact with hot water, steam or a basic solution can be obtained.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 27, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

[0034]

[Reference Example] (Production of Polyoxymethylene Copolymer) (1) Production of Sample A Highly purified trioxane (2 p of water in trioxane)
pm, 2000 g of formic acid 3 ppm, 1,3-dioxolane (0.8 mol% with respect to trioxane), and methylal (0.2 mol% with respect to trioxane) were put in a kneader with a jacket having two Σ blades, and 70
The temperature was raised to ° C. Then, a solution of trifluoromethanesulfonic acid in dioxane (0.002 mol / 1) was added to trioxane in an amount of 5 × 10 ⁻⁶ m based on trioxane.
Polymerization was carried out by adding so as to be ol%. After starting the reaction, 1
After 5 minutes, cold water was put into the jacket and cooled in a nitrogen atmosphere. After 1 hour, Mg _{0. 75} Al _0.25 O _1.125 as deactivator removed kneader contents (KW-2
300 Kyowa Kagaku) 0.01 for the polymer obtained
Add 2 wt% 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, 100 parts by weight of the obtained polymer,
0.2 parts by weight of 2-methylenebis- (4methyl-6-t-butylphenol) was added and extruded with a vented single-screw extruder (extrusion temperature 200 ° C, vent pressure 200t).
orr). (2) Production of Samples B to E In the same manner as in Sample A, polyoxymethylene copolymers were synthesized by changing the amounts of 1,3-dioxolane and methylal. The end of the obtained polymer has a methoxy group,
It is composed of an oxyethoxy group and a formate group.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

[0038]

Comparative Examples 1 and 2 Tenac 5010 (manufactured by Asahi Kasei) and Delrin 50, which are commercially available polyoxymethylene homopolymers
0 (manufactured by Du Pont) was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. The terminal group of Tenac 5010 is acetyl group , Delrin 500
The terminal group of is composed of an acetyl group and a methoxy group.

Claims (1)

[Claims] 1. A polymer comprising repeating oxymethylene units (—CH ₂ O—), wherein an oxyalkylene unit: (R and R ₀ may be the same or different, and are selected from hydrogen, an alkyl group and an allyl group, and R and R ₀ bonded to different carbon atoms may be the same or different, and are hydrogen and an alkyl group. , Allyl group, n is 1
It is the above integer, and m is an integer of 2 to 6. ) Is 0.07 to 0.5 per 100 mol of oxymethylene unit.
A polyoxymethylene gear having a mol-inserted structure and having a polymer end group which is an alkoxy group, a hydroalkoxy group or a formate group.