JPH0331742B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to highly lubricious polyacetal compositions. More specifically, it is suitably used for parts that require self-lubricating properties, such as automobile parts, electrical parts, and mechanical parts.
The present invention relates to a polyacetal composition that can provide molded articles with extremely excellent friction and wear characteristics. Conventional technology Conventionally, polyacetal has been used for example in automobile parts, electrical parts, etc. due to its excellent mechanical properties, electrical properties, creep properties, and friction and wear resistance properties.
Widely used in gears, bearings, and other mechanical parts. Polyacetal also has excellent self-lubricating properties, and is used in a variety of applications that take advantage of this property. However, this is not necessarily sufficient for applications requiring self-lubricating properties, and there is a strong desire for improved friction and wear properties. As a conventional technique for improving the lubricating properties of polyacetal, a method described in Japanese Patent Application Laid-Open No. 57-5714 is known. However, although the polyacetal polymer produced by this method has been effectively improved in terms of lubricity towards metals (S45C), it is still not satisfactory, and on the other hand, little improvement effect has been observed in terms of lubricity towards resins. Problems to be Solved by the Invention Under these circumstances, an object of the present invention is to provide a molded article with extremely excellent friction and wear characteristics that can be suitably used in various parts that require self-lubricating properties. An object of the present invention is to provide a highly lubricious polyacetal composition. Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have conducted extensive research and first determined that the terminal end is a residue of an alcohol or its alkylene oxide adduct, or a carboxylic acid or its alkylene oxide adduct. Polyoxymethylene (hereinafter referred to as base polymer) blocked with alcohol, alcohol,
It has been found that a composition containing an alkylene oxide addition to a carboxylic acid or a derivative thereof can improve lubricity. As a result of further intensive research, the present inventor found that a composition comprising the base polymer mixed with the same type of alcohol, an alcohol, an alkylene oxide adduct of a carboxylic acid, a derivative thereof, and a crystal nucleating agent, was found. It was discovered that the lubricity of polyacetal resin can be significantly improved, and the present invention was completed based on this knowledge. That is, the present invention provides (A) a number average molecular weight of 10,000 to
One end of the 500,000 polyoxymethylene chain is
general formula (R ₁ and R ₂ in the formula are each a hydrogen atom or a hydrocarbon group with or without a substituent, R ₃ is a hydrocarbon group with or without a substituent or an aliphatic or aromatic acyl group, m is an integer from 2 to 6,
(n is 0 or an integer from 1 to 1000) 100 parts by weight of a polyacetal derivative having a structure blocked by residues represented by (B) general formula (R ₄ and R ₅ in the formula are each a hydrogen atom or a hydrocarbon group with or without a substituent, R ₆ is a hydrocarbon group with or without a substituent or an aliphatic or aromatic acyl group, m' is an integer of 2 to 6, n' is an integer of 0 or 1 to 2000), at least one selected from alcohols, their ethers, or their esters, 0.5 to
20 parts by weight of the crystal nucleating agent (C) and 0.001 to 1 part by weight of the crystal nucleating agent (C). In the composition of the present invention, the base polymer used as component (A) has one end of the polyoxymethylene chain having the general formula (In the formula, R ₁ , R ₂ , R ₃ , m and n have the same meanings as above.) It has a structure blocked by residues represented by the following. If such a base polymer is shown as a structural formula, (R ₁ , R ₂ , R ₃ , m and n in the formula have the same meanings as above, and l is the average degree of polymerization). The polyacetal derivative represented by the above structural formula has a hydroxyl group at the end, and this hydroxyl group is unstable and can usually be converted to a stable group by a known method such as esterification, etherification, or urethanization. be done. The number average molecular weight of the portion of the base polymer consisting of repeating oxymethylene units excluding the terminal groups is the same as that of ordinary high molecular weight polyacetals, and is selected within the range of 10,000 to 500,000. The lower limit of the number average molecular weight is limited by the physical properties of the polyacetal derivative, and the upper limit is limited by the moldability of the polyacetal derivative. The residue blocking one end of the base polymer in the present invention is a residue of an alcohol or an alkylene oxide adduct thereof, or a carboxylic acid or an alkylene oxide adduct thereof, represented by the general formula (), and _R3OH ( _R3OH
has the same meaning as above), or to this alcohol or carboxylic acid, the general formula (R ₁ , R ₂ and m in the formula have the same meanings as above) This is a residue derived from a compound to which an alkylene oxide is added. Examples of the alcohol include methyl alcohol, ethyl alcohol, sec-butyl alcohol, hexyl alcohol, cyclohexyl alcohol, octyl alcohol, decyl alcohol,
Lauryl alcohol, cetyl alcohol, stearyl alcohol, eicosanol, ceryl alcohol, myricyl alcohol, oleyl alcohol, 3-ethyl-6-undecanol, phenol, p-butylphenol, p-octylphenol, p-nonylphenol, benzyl alcohol, p -Butylbenzyl alcohol, etc. Among these alcohols, from the viewpoint of improving the lubricating performance of the base polymer, long-chain aliphatic alcohols having 8 or more carbon atoms and p-alkyl-substituted phenols are preferable, and from the viewpoint of easy availability, lauryl alcohol, stearyl alcohol, Particularly preferred are eicosanol, p-octylphenol and p-nonylphenol. Examples of carboxylic acids include acetic acid, propionic acid, caproic acid, 2-ethylhexanoic acid, lauric acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, ricinoleic acid, phenylacetic acid, cinnamic acid, and benzoic acid. , p-octylbenzoic acid, α-naphthalic acid, etc. Among these carboxylic acids, from the viewpoint of improving the lubrication performance of the polyacetal polymer, long-chain aliphatic carboxylic acids having 8 or more carbon atoms are preferred, and from the viewpoint of easy availability, lauric acid, stearic acid, and oleic acid are preferred. and ricinoleic acid are particularly preferred. Examples of alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, styrene oxide,
Examples include oxetane, 3,3-bis(chloromethyl)oxetane, tetrahydrofuran, 2-methyltetrahydrofuran, and oxeban. Among these alkylene oxides, ethylene oxide and propylene oxide are particularly preferred from the viewpoint of affinity with polyacetal and ease of availability. These alkylene oxides can be used alone or in combination of two or more. Alternatively, for example, propylene oxide can be added to the alcohol first, then ethylene oxide can be added thereto, and then propylene oxide can be added thereto. The number of moles (n) of alkylene oxide added per mole of alcohol or carboxylic acid needs to be in the range of 0 to 1000, but in order to improve the lubricating properties of the base polymer, the larger the value of n, the better. On the other hand, from the viewpoint of ease of production and purification, it is preferable that n is smaller. Therefore, from both of these constraints, n is most preferably selected in the range of 2 to 250. Further, the number of moles (n) of alkylene oxide added per mole of alcohol or carboxylic acid can be easily determined by quantifying the hydroxyl group at one end of the produced adduct. The base polymer used in the present invention has the general formula (In the formula, R ₁ , R ₂ , R ₃ , m and n have the same meanings as above) Formaldehyde is polymerized in the presence of an alcohol or its alkylene oxide adduct, or a carboxylic acid or its alkylene oxide adduct. It can be obtained by The alcohol used in this case, its alkylene oxide adduct,
It is desirable that carboxylic acids and their alkylene oxide adducts be purified in advance by methods such as distillation, adsorption, and drying before being subjected to polymerization. Further, these compounds may be used alone or in combination of two or more. For this formaldehyde polymerization, catalysts generally known as anionic polymerization catalysts, coordination anionic polymerization catalysts, and cationic polymerization catalysts can be used. Typical groups of anionic polymerization catalysts and coordination anionic polymerization catalysts include alkali metals such as sodium and potassium, sodium-naphthalene,
Alkali metal complex compounds such as potassium-anthracene, alkali metal hydrides such as sodium hydride, alkaline earth metal hydrides such as calcium hydride, sodium methoxide, potassium t-
Alkali metal alkoxides such as butoxide, alkali metal salts of carboxylic acids such as sodium caproate and potassium stearate, alkaline earth metal salts of carboxylic acids such as magnesium caproate and calcium stearate, n-butylamine, diethylamine, trioctylamine, pyridine, etc. amines, quaternary ammonium salts such as ammonium stearate, tetrabutylammonium methoxide, dimethyl distearyl ammonium acetate, phosphonium salts such as tetramethylphosphonium propionate, trimethylbenzylphosphonium ethoxide, tributyltin chloride, diethyltin dilaurate, Examples include tetravalent organic tin compounds such as dibutyltin dimethoxide, and alkyl metals such as n-butyllithium and ethylmagnesium chloride. Examples of cationic polymerization catalysts include tin tetrachloride, tin tetrabromide, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, antimony pentafluoride, boron trifluoride, boron trifluoride diethyl etherate, and trifluoride. So-called Friedel-Crafts type compounds such as boron trifluoride coordination compounds such as boron acetate anhydrate and boron trifluoride triethylamine complex compounds, perchloric acid,
Inorganic and organic acids such as acetyl perchlorate, hydroxyacetic acid, trichloroacetic acid, p-toluenesulfonic acid, triethyloxonium tetrafluoroborate, triphenylmethylhexafluoroantimonate, aryldiazonium hexafluorophosphate, aryldiazonium tetrafluoroborate and alkyl metals such as diethylzinc, triethylaluminum, and diethylaluminum chloride. Polymerization of the base polymer is usually carried out in an organic medium. Organic media that can be used for polymerization include aliphatic hydrocarbons such as n-hexane, n-heptane, and cyclohexane, aromatic hydrocarbons such as benzene, toluene, and xylene, and halogenated hydrocarbons such as methylene chloride, chloroform, and trichloroethylene. These include aliphatic hydrocarbons and halogenated aromatic hydrocarbons such as chlorobenzene. These organic media may be used alone or in combination of two or more. The formaldehyde used in the polymerization needs to be substantially anhydrous and needs to be purified using known methods such as cold trap methods, solvent washing methods, and the like. For polymerization of such base polymers, conventionally known methods such as blow polymerization and solution polymerization can be used. Further, the molecular weight regulator is used after being uniformly dissolved or dispersed in the organic medium. The concentration of the molecular weight modifier in the organic medium can be easily determined experimentally depending on the molecular weight requirements of the desired polyacetal polymer. After the polymerized polymer is separated from the organic medium, the terminal unstable portions are blocked using, for example, acetic anhydride, and then a stabilizer and the like are added, and the polymer is used as a base polymer. In the composition of the present invention, the compound used as component (B) has the general formula (In the formula, R ₄ , R ₅ , R ₆ , m' and n' have the same meanings as above.) An alcohol, an ether thereof, or an ester thereof. Examples of the compound represented by the general formula () include alcohols, ethers, alkylene oxide adducts of alcohols, alkylene oxide adducts of carboxylic acids, terminal ethers of polyalkylene oxides, esters of alcohols and carboxylic acids, and alkylene alcohols. There are esters of oxide adducts and carboxylic acids, and esters of polyalkylene oxides acylated at one end and carboxylic acids. These compounds may be used alone or in combination of two or more. Among the above compounds, alcohols, alkylene oxide adducts thereof, carboxylic acids, and alkylene oxide adducts thereof may be the same as those described above. In addition, the alcohols, carboxylic acids, and alkylene oxides used as other compounds can also be the same as those described above, but among them, lauryl alcohol, lauryl alcohol, Stearyl alcohol, eicosanol, p-octylphenol and p-nonylphenol are preferred, and as the carboxylic acid, lauric acid, stearic acid, oleic acid and ricinoleic acid are preferred;
As the alkylene oxide, ethylene oxide and propylene oxide are preferred. The ether can be synthesized by dehydration condensation of the alcohols, and the terminal ether form of polyalkylene oxide can be synthesized by dehydration condensation of the alkylene oxide adduct of the alcohol and the alcohol. and carboxylic acids and esters of alkylene oxide adducts of alcohols and carboxylic acids can be obtained by esterifying the alcohols and alkylene oxide adducts of alcohols with the carboxylic acids or their acid anhydrides, respectively. Can be synthesized. Furthermore, a diester of a polyalkylene oxide with one end acylated and a carboxylic acid can be synthesized by esterifying the alkylene oxide adduct of the carboxylic acid with the carboxylic acid or its acid anhydride. can. Furthermore, when alkylene oxide is added to alcohol or carboxylic acid, the number of moles added is determined from the viewpoint of lubricity and ease of moldability. It is preferably equal to or less than the number of moles of oxide added. The blending ratio of the base polymer (A) component and the compound (B) component in the composition of the present invention is selected within the range of 0.5 to 20 parts by weight of component (B) per 100 parts by weight of component (A). It will be done. If component (B) is less than 0.5 parts by weight, the effect of the present invention will be small, while if it exceeds 20 parts by weight, the mechanical properties of the molded article obtained from the composition will be significantly reduced. From the viewpoint of lubricity, moldability, mechanical strength, etc., the amount of component (B) is preferably in the range of 2 to 10 parts by weight. The crystal nucleating agent used as component (C) in the composition of the present invention preferably has a particle size of 10 μm or less, and nitrogen boron, talc, and phyllite are particularly suitable as the crystal nucleating agent. The talc is mainly composed of magnesium silicate, and the phyllite is mainly composed of aluminum silicate. These crystal nucleating agents may be used alone or in combination of two or more, and the blending amount is 0.001 to 1 part by weight, preferably 0.001 to 1 part by weight, based on 100 parts by weight of the base polymer of component (A). is selected in the range of 0.01 to 0.5 parts by weight. Conventionally known additives, such as stabilizers, can be added to the composition of the present invention to the extent that they do not impair the effects of the present invention. In addition, when adding a stabilizer and component (B) to the base polymer of component (A), it is preferable that the base polymer and stabilizer are powders, and furthermore, (B)
When the component is solid, it is preferable to use a powdered component as much as possible. The composition of the present invention is prepared, for example, by uniformly mixing a powdered base polymer, a powdered stabilizer, a liquid or powdered component (B), and a powdered crystal nucleating agent using a commonly used Henschel mixer or the like. Ru. This composition can be easily molded using an extruder, injection molding machine, or the like. Effects of the Invention The polyacetal composition of the present invention can provide molded articles with extremely superior self-lubricating properties compared to conventional compositions. This excellent lubricity is due to
Polyacetal derivatives whose ends are blocked with residues of alcohol or its alkylene oxide adduct, or carboxylic acid or its alkylene oxide adduct, are added with the same type of alcohol, alcohol,
This property is obtained for the first time by a composition comprising an alkylene oxide adduct of a carboxylic acid or a derivative thereof and a crystal nucleating agent, and the property is obtained by a composition comprising a crystal nucleating agent and a polyoxymethylene end-capped with the above-mentioned residues or the above-mentioned composition. It can be obtained either with a composition that does not contain a crystal nucleating agent, or with a composition that contains alcohol, an alkylene oxide adduct of alcohol, a carboxylic acid, or a derivative thereof, with polyoxymethylene whose terminal end is blocked with an acetyl group. I can't. Furthermore, the composition of the present invention can provide a molded article with extremely excellent lubricity as described above, and the moldability and other physical properties of the molded article are completely comparable to those of conventional compositions, making it suitable for automobiles. It is particularly suitable for use in parts, electrical parts, mechanical parts, etc., which require self-lubricating properties. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way. The friction coefficient and wear amount of the molded product were determined as follows. (1) Friction coefficient Using a thrust type friction and wear tester, two carts
Measurements were performed under the conditions of Kg/cm ² and linear velocity of 1.2 to 70 cm/sec, and the average coefficient of friction was determined. (2) Amount of wear Using the above testing machine, the cart was set at 2Kg/cm ² and linear speed.
Measurements were performed under the conditions of 0.72 Km/hr and a running distance of 200 Km, and the amount of wear was determined. Production example Production of base polymer Tetrabutylammonium acetate 1.0~
10 ^-4 mol/and

[Formula] (Random copolymer adduct of ethylene oxide and propylene oxide to stearyl alcohol, average number of added moles of ethylene oxide and propylene oxide 55, hereinafter abbreviated as SEP-55) 5×
Formaldehyde gas with a purity of 99.9% and toluene solution with the above composition are added to 500 parts by weight of a toluene solution containing 10 ^-3 mol/hour at a rate of 110 parts by weight and 500 parts by weight, respectively, and the polymerization temperature is maintained at 60°C. The reactor was continuously fed for 3 hours while the reaction solution was continuously drawn out in proportion to the amount fed. The polymer in the reaction solution was separated by filtration, thoroughly washed with acetone, and then dried at 60°C to obtain 289 parts by weight of a white polymer. 50 parts by weight of the polyacetal polymer thus obtained was added to acetic anhydride.
with 500 parts by weight and 0.1 part by weight of sodium acetate
The mixture was heated at 139°C for 3 hours to obtain 49 parts by weight of the base polymer. In addition, formaldehyde gas with a purity of 99.9% is
Thoroughly dehydrated and dried paraformaldehyde at 150%
It was obtained by pyrolysis at °C and passing through a cooling trap several times. Example 1, Comparative Examples 1 and 2 To 100 parts by weight of the base polymer obtained in the production example, 2,
0.25 parts by weight of 2'methylenebis(4-methyl-6-tert-butylphenol) (hereinafter abbreviated as 2246),
0.7 parts by weight of copolyamide (hereinafter abbreviated as PA) consisting of polyhexamethylene adipamide/polyhexamethylene sebamide/polycaprolactam, 5 parts by weight of stearyl alcohol, and 0.02 parts by weight of boron nitride were added to form a polyacetal composition. A product was prepared and molded using a 30 mmφ extruder. The lubricity of this molded article was determined and the results are shown in Table 1. In addition, for comparison, in the above composition, the composition in which only stearyl alcohol was added to the base polymer (Comparative Example 1), and the composition in which stearyl alcohol and crystal nucleating agent were not added (Comparative Example 2) were also examined. We looked for lubricity. The results are shown in Table 1.

[Table] Example 2, Comparative Examples 3 and 4 To 100 parts by weight of the base polymer obtained in the production example,
2246 0.25 parts by weight, PA0.7 parts by weight, C ₁₈ H ₃₇ O
A polyacetal composition was prepared by adding 5 parts by weight of (CH ₂ CH ₂ O) ₃ H (ethylene oxide adduct of stearyl alcohol, hereinafter abbreviated as S-3) and 0.05 parts by weight of boron nitride, and a 30 mmφ extruder was added. It was molded using Find the lubricity of this material,
The results are shown in Table 2. In addition, for comparison, in the above composition, a composition in which only S-3 was added to the base polymer (Comparative Example 3), a composition in which S-3 and a crystal nucleating agent were not added (Comparative Example 4), and the respective molding The lubricity of the product was determined. The results are shown in Table 2.

[Table] Examples 3 to 17 To 100 parts by weight of the base polymer obtained in the production example,
2246 Added 0.25 parts by weight, 0.7 parts by weight of PA, 3 parts by weight of alcohols or alkylene oxide adducts of alcohols and carboxylic acids shown in Table 3, and 0.05 parts by weight of various crystal nucleating agents shown in Table 3. A polyacetal composition was prepared and molded using a 30 mmφ extruder. The lubricity of this material was determined and the results are shown in Table 3.

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Claims (1)

[Scope of Claims] 1 (A) One end of the polyoxymethylene chain having a number average molecular weight of 10,000 to 500,000 has the general formula (R ₁ and R ₂ in the formula are each a hydrogen atom or a hydrocarbon group with or without a substituent, R ₃ is a hydrocarbon group with or without a substituent or an aliphatic or aromatic acyl group, m is an integer from 2 to 6,
100 parts by weight of a polyacetal derivative having a structure blocked by a residue represented by (R ₄ and R ₅ in the formula are each a hydrogen atom or a hydrocarbon group with or without a substituent, R ₆ is a hydrocarbon group with or without a substituent or an aliphatic or aromatic acyl group, m' is an integer of 2 to 6, n' is an integer of 0 or 1 to 2000), 0.5 to 20 parts by weight of at least one selected from alcohols, ethers thereof, or esters thereof; (C) A highly lubricating polyacetal composition containing 0.001 to 1 part by weight of a crystal cutting agent. 2. The composition according to claim 1, wherein the crystal nucleating agent is at least one selected from boron nitride, talc, and phyllite.