WO2004058887A1

WO2004058887A1 - Polyoxymethylene resin composition

Info

Publication number: WO2004058887A1
Application number: PCT/KR2003/002912
Authority: WO
Inventors: Mok-Keun Lim; Yong-Seon Park
Original assignee: Kolon Industries, Inc.
Priority date: 2002-12-31
Filing date: 2003-12-30
Publication date: 2004-07-15
Also published as: AU2003289581A1; KR20040061720A

Abstract

Disclosed is a polyoxymethylene resin composition, including a polyoxymethylene resin, and an antioxidant, a zinc compound, and polyalkyleneglycol as an essential component, with an alkali earth metal compound and a formaldehyde-reactive material as a selective component, which can be effectively applied for molded articles of fields requiring high resistance to diesel and gasoline, or high chlorine resistance.

Description

POLYOXYMETHYLENE RESIN COMPOSITION

Technical Field

The present invention relates to polyoxymethylene resin compositions, and more specifically, to a polyoxymethylene resin composition having a high resistance to fuel used in internal-combustion engines of automobiles, by improving the decomposition resistance of a polyacetal resin composition with respect to diesel and gasoline used in internal-combustion engines.

Background Art

h general, polyoxymethylene (hereinafter, abbreviated as 'POM') has a high mechanical strength, and is superior in rigidity, creep resistance, chemical resistance and sliding characteristics. Therefore, the POM has been widely used as a representative engineering plastic in industrial fields, including automobile parts, and electric and electronic parts.

Particularly, the above resin, which has a very high chemical resistance, can exhibit excellent properties to gasoline or alkali environments for long periods, and thus, has been utilized for various living goods. However, in recent years, since fuel, such as diesel and gasoline, contains an aggressive acid component for improvement of performance or due to environmental impact, efforts to improve the quality of the fuel have been made. This is because, in cases where a molded article from a conventional POM resin is in contact with fuel at high temperatures for long periods, the resin is decomposed and has a decreased weight, resulting in the drastic reduction of mechanical properties thereof. Further, when the above resin is in long-term use for automobile-related parts, which are difficult to be frequently replaced with new ones, the worst problems may occur.

Hence, with the intention of improving resistance to diesel and gasoline of the POM resin, adding methods of a strong alkali material are known, this regard, EP 0 855 424 Al discloses a method of adding a derivative, such as sterically hindered amine, benzotriazole, benzophenone and benzoate, as a stabilizer. Additionally, in Korean Patent Laid-open Publication No. 10-2001- 0039632, there is disclosed the use of polyalkyleneglycol and zinc oxide. However, the polyacetal resin composition of the above patent has a resistance unsuitable for use in environmental conditions having the large amounts of the aggressive acid component, which are recent fuel development trends. That is, when the above polyacetal resin composition is used, it is impossible to maintain the weight and tensile strength required for the POM resin. Further, increase of the amount of the antioxidant, such as sterically hindered amine, results in drastically decreased resistance to diesel and gasoline. Although resistance to diesel and gasoline may be slightly increased by using larger amounts of zinc oxide, it is noted that the use of 5% or more of an inorganic material leads to decreased tensile strength, tensile elongation and impact strength of the resin composition. Thus, it is difficult to apply the above resin composition so as not to harm the properties of the POM resin.

Hence, there is urgently required the development of a POM resin having a high resistance to diesel and gasoline, as fuel for internal-combustion engines that contain large amounts of aggressive acid components, while not harming the properties of the POM resin.

Disclosure of the Invention

Leading to the present invention, intensive and thorough research on polyoxymethylene resin compositions, carried out by the present inventors aiming to avoid the problems encountered in the related art, resulted in the finding that a polyoxymethylene resin is properly mixed with a sterically hindered amine-based antioxidant, a zinc compound, polyalkyleneglycol, an alkali earth metal compound, and a formaldehyde-reactive material, whereby the resultant polyoxymethylene resin composition has drastically increased resistance to fuel of internal-combustion engines containing larger amounts of aggressive acid components while not harming the properties of the polyoxymethylene resin.

Therefore, it is an object of the present invention to provide a novel polyoxymethylene resin composition having a superior resistance to fuel for use in internal-combustion engines.

To achieve the above object of the present invention, there is provided a polyoxymethylene resin composition, comprising (a) 100 parts by weight of a polyoxymethylene resin, (b) 0.01-5 parts by weight of a sterically hindered amine-based antioxidant, (c) 0.05-5 parts by weight of a zinc compound, and (d) 0.1-10 parts by weight of polyalkyleneglycol.

Best Mode for Carrying Out the Invention

Based on the present invention, a polyoxymethylene resin composition is provided, consisting mainly of a POM resin, with a sterically hindered amine- based antioxidant, a zinc compound and polyalkyleneglycol as essential components.

Used as a main component of the polyoxymethylene resin composition, the POM resin is preferably an oxymethylene homopolymer or an oxymethylene copolymer containing at least one oxyalkylene unit of 2-8 carbon atoms in a polymer main chain formed of an oxymethylene unit.

In addition, the sterically hindered amine-based antioxidant, which is essentially added to the present resin composition, is selected from the group consisting of 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6- tetramethylpiperidine, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy- 2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4- cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6- tetramethylpiperidine, 4-benzyloxy-2,2,6,6-tetramethylpiperidine, 4-

(phenylcarbamoyloxy)-2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4- piperidyl)oxalate, bis(2,2,6,6-tetramethyl-4-piperidyl)malonate, bis(2,2,6,6,- tetramethyl-4-piperidyl)adipate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(l,2,2,6,6-pentamethyl-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4- piperidyl)terephthalate, l,2-bis(2,2,6,6-tetramethyl-4-piperidyloxy)ethane, bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylene-l,6-dicarbamate, bis(l- methyl-2,2,6,6-tetramethyl-4-piperidyl)adipate, tris(2,2,6,6-tetramethyl-4- piperidyl)benzene-l,3,5-tricarboxylate, and mixtures thereof. The sterically hindered amine-based antioxidant is used in an amount of 0.01-5.0 parts by weight, and preferably, 0.05-3 parts by weight, based on 100 parts by weight of the polyoxymethylene resin. If the amount is less than 0.01 parts by weight, the resultant composition has insignificant effects. Whereas, if the amount is larger than 5 parts by weight, the above component may be deposited as a white powder phase on the surface of the POM resin.

Further, the zinc compound is preferably selected from the group consisting of zinc oxide, zinc hydroxide, zinc carbonate, zinc borate, zinc organic acid, and mixtures thereof. In this case, the organic acid is exemplified by formic acid, acetic acid, propionic acid, and alkane acid, alkene acid or alkyne acid having 4 or more carbon atoms, malonic acid, citric acid, adipic acid, maleic acid, oxalic acid, benzoic acid, phthalic acid, trimellitic acid, salicylic acid, gallic acid, naphthenic acid, and substitution derivatives thereof, and fatty acid having 12 or more carbon atoms, such as lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. Of them, the preferable zinc compound is zinc oxide and zinc hydroxide. The zinc compound is used in the amount of 0.05-5 parts by weight, and preferably, 0.1-3 parts by weight, based on 100 parts by weight of the polyoxymethylene resin. If the amount is smaller than 0.05 parts by weight, it is impossible to exhibit resistance to fuel. While, if the amount is larger than 5 parts by weight, undesired properties may result.

Also, as the polyalkyleneglycol, polyethyleneglycol or polypropyleneglycol is preferably used, with a molecular weight of 500-9,000. The use of polyalkyleneglycol having a molecular weight less than 500 results in a concentrated distribution of polyalkyleneglycol to the surfaces of molded articles. Whereas, if the molecular weight exceeds 9,000, the improvement in comparison with the added amounts becomes insignificant. Thus, polyalkyleneglycol is used in the amount of 0.1-10 parts by weight, and preferably, 0.1-5 parts by weight, based on 100 parts by weight of the polyoxymethylene resin. When the amount is less than 0.1 parts by weight, desirable effects cannot be obtained. Whereas, if the amount exceeds 10 parts by weight, the physical properties of the molded articles are negatively affected.

Moreover, the present polyoxymethylene resin composition further includes the selective component, that is, an alkali earth metal compound and a formaldehyde-reactive material, in addition to the above essential components.

The alkali earth metal compound is selected from the group consisting of magnesium compounds, calcium compounds, strontium compounds, and mixtures thereof. Such an alkali earth metal compound is present in the form of organic acid compounds, hydroxides, and oxides, as in the zinc compound. Particularly, the preferable alkali earth metal compound is the organic acid compounds of magnesium and the organic acid compounds of calcium. The alkali earth metal compound is used in the amount of 0.05-5 parts by weight, and preferably, 0.1-2 parts by weight, based on 100 parts by weight of the POM resin. In particular, it is preferred that the total amounts of the alkali earth metal compound and the zinc compound be 0.1-5 parts by weight, based on 100 parts by weight of the POM resin. If the amount of the alkali earth metal compound is less than 0.05 parts by weight, it is impossible to exhibit resistance to fuel. Meanwhile, if the amount exceeds 5 parts by weight, the properties are negatively affected.

The formaldehyde-reactive material is selected from the group consisting of formaldehyde-reactive amide compounds, urethane compounds, pyridine derivatives, urea derivatives, triazine derivatives, hydrazine derivatives, and mixtures thereof. This component is used to prevent the functions of the metal compound from decreasing due to the reaction of the metal compound with formic acid oxidized from formaldehyde upon molding the resin. Such a formaldehyde-reactive material is exemplified by lactam-based homopolymers or copolymers, such as N,N-diphenylbenzeneamide, N,N-dimethylacetamide, N,N- diphenylformamide, N,N-diphenylbenzeneamide, N,N,N',N'- tetramethyladipamide, nitric acid dianilide, adipic acid anilide, α-(N- phenyl)acetanilide, nylon 6, nylon 11, and nylon 12; polyamide homopolymers or copolymers derived from divalent carbonic acid, such as adipic acid, sebacic acid, decane dicarbonic acid and dimer acid, and diamine, such as ethylenediamine, tetramethylenediamine, hexamethylenediamine and metaxylenediamine; polyamide copolymers derived from lactam-based compounds, dicarbonic acid and diamine; amide compounds, such as polyacrylamide, polymethacrylamide, poly(N-vinyllactam), and poly(N-vinylpyrrolidone); polyurethane compounds derived from diisocyanate, such as toluene diisocyanate and diphenylmethane diisocyanate, glycol such as 1,4-butanediol, and polymer glycol, such as poly(tetramethyleneoxide)glycol, and polycaprolactam; triazine derivatives, such as melamine, benzoguanamine, acetguanamine, N-butylmelamine, N- phenylmelamine, N,N'-diphenylmelamine, N,N,N-triphenylmelamine, N- methylmelamine, N,N'-dimethylmelamine, N,N',N'-trimethylmelamine, 2,4- diamino-6-benzyloxytriazine, 2,4-diamino-6-phthoxytriazine and 2,4-diamino-6- cyclohexyltriazine; urea derivatives, such as N-phenyl urea, N,N'-diphenyl urea, thiourea, N-phenylthiourea, N,N'-diphenylthiourea, and nonamethylene polyurea; hydrazine derivatives, such as phenylhydrazine, diphenylhydrazine, hydrazine of benzoaldehyde, semicarbozone, 1 -methyl- 1-phenylhydrazone, hydrazone of 4- (dialkylamino)benzoaldehyde, 1 -methyl- 1-phenylhydrazone and thiosemicarbazone; amine compounds, such as dicyanediamide, guancydine, guanidine, aminoguanidine, guanine, guanacline, guanochlor, guanoxane, guanosine, amirolide, and N-amidino-3-amino-6-chlorohydrazinecarboxyamide; pyridine derivatives, such as poly(2-vinylpyridine), poly(2-methyl-5- vinylpyridine), poly(2-ethyl-5-vinylpyridine), 2-vinylpyridine-2-methyl-5- vinylpyridine copolymer, and 2-vinylpyridine-styrene copolymer. Among those listed above, it is preferable to use dimer oxypolyamide, melamine, guanamine, benzoguanamine, N-methylated melamine, N-methylated benzoguanamine, thermoplastic polyurethane, dicyanediamide, guanidine, poly(N- vinylpyrrolidone), and poly(2-vinylpyridine). The formaldehyde-reactive material is used in the amount of 0.01-2 parts by weight, and preferably, 0.05-1 parts by weight, based on 100 parts by weight of the POM resin. When the amount is smaller than 0.01 parts by weight, thermal stability decreases. On the other hand, when the amount is larger than 2 parts by weight, the above component may be deposited on the surface of the molded article.

The obtained polyoxymethylene resin composition is usefully applied for molded articles of fields requiring a high fuel resistance of internal-combustion engines, resisting such fuels as diesel, gasoline, and other fuels. In particular, the polyoxymethylene resin composition can be used as a material of a molded article that is in direct contact with fuel used for the internal-combustion engines of automobiles, such as fuel pipes, fuel tanks, and fuel delivering units.

Further, the polyoxymethylene resin composition is superior in chlorine resistance, and can be effectively applied for cooling columns, water pipes, and other device components.

Having generally described this invention, a further understanding can be obtained by reference to specific examples and comparative examples which are provided herein for the purposes of illustration only and are not intended to be limiting unless otherwise specified.

Examples 1 to 5 and Comparative Examples 1 to 8

A polyoxymethylene resin was dried at 80°C for 4 hours in a vacuum, and then mixed with an antioxidant, a formaldehyde-reactive material, polyalkyleneglycol and a metal compound, and then introduced into a first inlet of an extruder. In the cases where the metal compound was used in larger amounts, it could be placed into a second inlet of the extruder. The above mixture was sufficiently melted and kneaded at 190°C using the extruder, discharged in a long and narrow tube shape through a die, cooled, and then cut by use of a pelletizer, to obtain a resin composition as a chip. The resin composition was sufficiently dried and a dumbbell-shaped test piece (ASTM D256) was injection molded at 190°C, and measured for mechanical properties. The test piece was measured for initial tensile strength and weight, and then immersed into diesel oil at 110°C for 1000 hours. Thereafter, tensile strength and weight of the test piece were measured, and thus the maintenance rates of both tensile strength and weight were calculated. Each component (based on 100 parts by weight of the polyoxymethylene resin) of the polyoxymethylene resin compositions of examples and comparative examples prepared according to the above procedure are shown in Table 1, below. The results of the measured properties are given in Table 2, below.

TABLE 1

* Antioxidant

A01 : pentaerythrityl-tetrakis[3-(3,5- di-t-butyl-4-hydroxyphenyl)propionate] A02 : bis(2,2,6,6-tetramethyl-4* ■piperidyl)sebacate

* Zinc Compound

Ml : zinc oxide M2 : zinc hydroxide

* Alkali Earth Metal Compound M3 : magnesium stearate

M4 : calcium stearate

* Polyalkyleneglycol

PG : polyethyleneglycol, MW: 6000 * Formaldehyde-Reactive Material FA : glycerin monostearate

TABLE 2

* 50% or less is represented by '-', in consideration of measurement errors

* weight maintenance rate (%) is calculated: weight maintenance rate (%) = (dry weight after immersion/dry weight before immersion) x 100

* tensile strength maintenance rate (%) is calculated: tensile strength maintenance rate (%) = (tensile strength after immersion/tensile strength before immersion) x 100

Industrial Applicability

As described hereinbefore, the present invention provides a polyoxymethylene resin composition having high maintenance rates of weight and tensile strength. Further, the polyoxymethylene resin composition can be applied for molded articles of fields requiring high resistance to fuel, such as diesel and gasoline, for example, parts in direct contact with fuel used in internal- combustion engines of automobiles, which include fuel pipes, fuel tanks and fuel delivering units. Further, the inventive resin composition has a high chlorine resistance, and thus, can be used for cooling columns, water pipes, etc. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A polyoxymethylene resin composition, comprising (a) 100 parts by weight of a polyoxymethylene resin, (b) 0.01-5 parts by weight of a sterically hindered amine-based antioxidant, (c) 0.05-5 parts by weight of a zinc compound, and (d) 0.1-10 parts by weight of polyalkyleneglycol.

2. The composition as defined in claim 1, further comprising 0.05-5 parts by weight of an alkali earth metal compound, based on 100 parts by weight of the polyoxymethylene resin.

3. The composition as defined in claim 1, further comprising 0.01-2 parts by weight of a formaldehyde-reactive material, based on 100 parts by weight of the polyoxymethylene resin.

4. The composition as defined in claim 1, wherein the polyalkyleneglycol has a number average molecular weight of 500-9,000.

5. The composition as defined in claim 2, wherein the alkali earth metal compound is selected from the group consisting of magnesium compounds, calcium compounds, strontium compounds, and mixtures thereof.

6. The composition as defined in claim 3, wherein the formaldehyde- reactive material is selected from the group consisting of amide compounds, urethane compounds, pyridine derivatives, urea derivatives, triazine derivatives, hydrazine derivatives, and mixtures thereof.