Acid-resistant polyoxymethylene compositions and articles made therefrom

Abstract

Disclosed is a polyoxymethylene polymer composition that is fuel-resistant, particularly diesel fuel-resistant, and resistant to strong acid solutions, and a molded article made from the composition.The polymer composition contains a polyoxymethylene polymer in combination with a combination of stabilizers, for example a combination of at least three different stabilizers.In addition, the polymer composition contains an acid neutralizer and optionally a plasticizer.

Description

[Technical Field]

[0001] Related Applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 288,320, filed December 10, 2021, and is incorporated herein by reference. [Background technology]

[0002]

[0002] Polyacetal polymers, commonly referred to as polyoxymethylene polymers, have been established as highly useful industrial materials in a variety of applications. Polyoxymethylene polymers are widely used, for example, in the construction of molded parts, such as those for use in the automotive and electrical industries. Polyoxymethylene polymers have, for example, excellent mechanical properties, fatigue resistance, abrasion resistance, chemical resistance, and moldability.

[0003]

[0003] Due to their excellent mechanical properties, heat resistance, and chemical resistance, polyoxymethylene polymers have been used to manufacture components for various vehicles, such as automobiles and trucks. For example, because polyoxymethylene polymers do not significantly decompose when in contact with fuel, molded parts made from polyoxymethylene polymers have been used to manufacture fuel lines and other vehicle parts that repeatedly come into contact with vehicle fuel. In addition to being fuel-resistant, polyoxymethylene polymer compositions also have excellent impact resistance properties, making molded parts made from the polymers resistant to damage or crack formation during normal wear and tear.

[0004] However, particular problems are encountered when polyoxymethylene compositions are designed to come into contact with diesel fuel. Diesel fuel, for example, may contain sulfur or sulfur-containing compounds. When diesel fuel is heated over an extended period of time, the sulfur-containing compounds can oxidize to form acidic sulfur compounds, which can decompose many different synthetic polymers and may have some effect on polyoxymethylene polymers. Therefore, in the past, polyoxymethylene polymers have been combined with a variety of different additives, such as hindered amine light stabilizers or zinc oxide, to make the polymer more resistant to contact with corrosive substances that may form from diesel fuel.

[0005]

[0005] In recent years, an increasing number of automobiles and trucks have been fitted with decorative rims on their tires. Often, the decorative rims are made from polished metal, chrome, or the like. To clean these materials, consumer and commercial car and truck washes typically use highly acidic wheel cleaners. For example, wheel cleaners may have a pH of less than 3, or even less than 2. These wheel cleaners are typically sprayed onto the automobile's fuel components during application to the wheels. These highly acidic solutions can cause rapid aging of the fuel components, causing them to deteriorate and break down over time.

[0006]

[0006] In view of the above, those skilled in the art have attempted to create polyoxymethylene polymer compositions that are resistant to acid. For example, U.S. Patent No. 7,247,665 and U.S. Patent Publication No. 2018 / 0319980, both of which are incorporated herein by reference, disclose polyoxymethylene polymer compositions with improved acid resistance. Although both of the above patent publications disclose compositions that represent a significant improvement in the art, further improvement in acid resistance remains necessary. Summary of the Invention [Problem to be solved by the invention]

[0007] In particular, there is a need for polyoxymethylene polymer compositions with improved acid resistance, and in particular for polyoxymethylene polymer compositions containing additives that can enhance acid scavenging capabilities to further improve acid resistance and possibly other properties. [Means for solving the problem]

[0008]

[0008] In general, the present disclosure is directed to polymer compositions containing primarily polyoxymethylene polymers and molded articles made from the compositions. The polymer compositions of the present disclosure are formulated to be particularly acid-resistant. More specifically, the polymer compositions of the present disclosure and articles molded therefrom are suitable for contact with various fuels, including diesel fuel, and highly acidic fluids, such as various detergents. After repeated contact with fuels and acidic solutions, articles molded in accordance with the present disclosure resist significant degradation.

[0009] The polymer compositions of the present disclosure generally contain a polyoxymethylene polymer and one or more acid neutralizing agents. In addition, the polymer compositions contain an additive package including a combination of stabilizers that can be used synergistically with other components to improve acid resistance and / or fuel resistance. The stabilizer package can also improve other properties, including mold release.

[0010] In one embodiment, for example, a polymer composition includes a polyoxymethylene polymer in combination with at least one acid neutralizer and, optionally, a plasticizer. According to the present disclosure, the polymer composition further includes a combination of stabilizers. The combination of stabilizers includes a hindered phenolic antioxidant, an aromatic amine stabilizer, and a thioester stabilizer. In one aspect, the hindered phenolic antioxidant can be present in the composition in an amount greater than the aromatic amine stabilizer and / or in an amount greater than the thioester stabilizer. For example, the weight ratio of the hindered phenolic antioxidant to the aromatic amine stabilizer can be from about 10:1 to about 1:1, such as from about 5:1 to about 1:1, for example, from about 3:1 to about 1.5:1. The weight ratio of the hindered phenolic antioxidant to the thioester stabilizer can be from about 15:1 to about 1:1, such as from about 8:1 to about 1.5:1, for example, from about 5:1 to about 2:1. In one aspect, the phenolic antioxidant is present in an amount of about 0.2 wt % to about 3.5 wt %. In a particular embodiment, the hindered phenolic antioxidant is present in the composition in an amount less than about 1.5 wt %, such as less than about 1 wt %, for example less than about 0.8 wt %, and typically greater than about 0.2 wt %.

[0011] In one embodiment, the hindered phenolic antioxidant includes tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl-propionate)]. The aromatic amine stabilizer may include 4-(1-methyl-1-phenylethyl)N-[4-(1-methyl-1-phenylethyl)phenyl]aniline. In one embodiment, the aromatic amine stabilizer may be present in the polymer composition in an amount of about 0.05% to about 1.5% by weight. The thioester stabilizer may include distearyl thiodipropionate. The thioester stabilizer may be present in the composition in an amount of about 0.03% to about 1.3% by weight.

[0012] The polyoxymethylene polymer, which may include a polyoxymethylene copolymer, may be present in the polymer composition in an amount greater than about 70% by weight, e.g., greater than about 80% by weight, e.g., greater than about 90% by weight. In one embodiment, the polyoxymethylene polymer is present in the polymer composition in an amount less than about 96% by weight, e.g., less than about 95% by weight. The polyoxymethylene polymer may have a melt flow index greater than about 0.5 g / 10 min, e.g., greater than about 5 g / 10 min, e.g., greater than about 9 g / 10 min, e.g., greater than about 10 g / 10 min, e.g., greater than about 11 g / 10 min, as measured at 190°C and a 2.16 kg load according to ISO Test 1133. The melt flow index is generally less than about 40 g / 10 min, e.g., less than about 35 g / 10 min, e.g., less than about 30 g / 10 min. In one embodiment, the melt flow index is from about 10 g / 10 min to about 15 g / 10 min. Alternatively, the polyoxymethylene polymer may have a relatively low melt flow index, less than about 5 g / 10 min, such as less than about 4 g / 10 min, for example less than about 3 g / 10 min, and generally greater than about 0.1 g / 10 min.

[0013] As described above, the polyoxymethylene polymer is combined with at least one acid neutralizer and, optionally, a plasticizer. The acid neutralizer, in one aspect, includes one or more magnesium compounds. In some embodiments, the use of magnesium compounds can provide optimal acid resistance depending on the physical properties of the particles. The magnesium compounds may be, for example, hydroxides, oxides, carbonates, and the like.

[0014] In one embodiment, one or more acid neutralizing agents are present in the composition in an amount greater than about 2.5 wt.%, e.g., greater than about 3.5 wt.%, e.g., greater than about 4.5 wt.%, e.g., greater than about 5.5 wt.%, and generally less than about 15 wt.%, e.g., less than about 10 wt.%. In one aspect, the acid neutralizing agent comprises magnesium oxide alone. Alternatively, the acid neutralizing agent may comprise magnesium hydroxide, alone or in combination with magnesium oxide. In yet another embodiment, the composition contains zinc oxide in combination with magnesium oxide and / or magnesium hydroxide.

[0015] As described above, the polymer composition optionally further contains a plasticizer. The plasticizer may, for example, comprise a polyalkylene glycol. The polyalkylene glycol may, for example, have an average molecular weight greater than about 2,000 g / mol, for example, from about 3,000 g / mol to about 9,000 g / mol. The plasticizer may generally be present in the polymer composition in an amount greater than about 1 wt %, for example, greater than about 1.3 wt %, for example, greater than about 1.7 wt %, and generally less than about 10 wt %, for example, less than about 5 wt %, for example, less than about 4 wt %, for example, less than about 3.3 wt %, for example, less than about 2.8 wt %.

[0016] In other embodiments, the plasticizer may include aromatic polyesters, aliphatic diesters, epoxides, sulfonamides, polyethers, polybutenes, polyamides, acetylated monoglycerides, alkyl citrates, or aromatic esters including organic phosphates.

[0017] The polymer composition may also contain a wax. The wax may be, for example, ethylene bis(stearamide). The wax may be present in the polymer composition in an amount greater than about 0.05 wt %, for example, greater than about 0.1 wt %, for example, greater than about 0.15 wt %, for example, greater than about 0.18 wt %, and generally less than about 2 wt %, for example, less than about 1 wt %, for example, less than about 0.8 wt %, for example, less than about 0.7 wt %.

[0018] The polymer composition may also contain a salt of a carboxylic acid, such as a salt of a hydroxycarboxylic acid. In one embodiment, the polymer composition contains calcium hydroxystearate. The carboxylic acid compound may be present in the polymer composition in an amount greater than about 0.1 wt %, for example, greater than about 0.2 wt %, and generally less than about 1.5 wt %, for example, less than about 1 wt %, for example, less than about 0.5 wt %.

[0019] As described above, the polymer composition is suitable for producing molded articles that will come into contact with fuels such as diesel fuel. The polymer composition is also resistant to strongly acidic solutions. In one embodiment, for example, the polymer composition may be used to produce vehicle exterior parts. The molded article may include, for example, a portion of a fuel system for an automobile or truck. In one embodiment, for example, the molded article may include a fuel-contacting component. The fuel-contacting component may include a fuel line, a fuel valve, or a fuel flange.

[0020]

[0020] Other features and aspects of the present disclosure are discussed in more detail below.

[0021] A full and enabling disclosure of the present disclosure is set forth in more detail in the remainder of the specification, including reference to the accompanying figures. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a side view of one embodiment of a fuel line made in accordance with the present disclosure. [Figure 2]FIG. 1 is a perspective view of an embodiment of a fuel flange made in accordance with the present disclosure. [Figure 3] 1 is a graphical representation of the results obtained in the following examples. DETAILED DESCRIPTION OF THE INVENTION

[0022] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the invention.

[0023] Those skilled in the art will recognize that the discussion of the present invention is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present disclosure.

[0023]

[0024] In general, the present disclosure is directed to polyoxymethylene polymer compositions and polymeric articles made therefrom. The polymeric compositions contain polyoxymethylene polymers and have acid and fuel resistance. In particular, the polymeric compositions of the present disclosure are resistant to strongly acidic solutions or acidic by-products that may come into contact with the fuel systems of vehicles such as automobiles or trucks. Strongly acidic solutions may include, by way of example, wheel cleaners, rim cleaners, chrome cleaners, and the like. In the past, polyoxymethylene polymer compositions have been formulated to be diesel fuel resistant. However, such formulations may be susceptible to damage or degradation when contacted with wheel or rim cleaner solutions that inadvertently come into contact with components or articles that make up the fuel system. In this regard, the present disclosure is directed to polyoxymethylene polymer compositions containing a combination of at least one acid neutralizer and a stabilizer. The stabilizer is present in the composition in an amount and ratio found to dramatically improve acid resistance.

[0024]

[0025] The stabilizer composition contained in the polymer composition of the present disclosure, in one embodiment, comprises a hindered phenolic antioxidant, an aromatic amine stabilizer, and a thioester stabilizer. Suitable hindered phenolic antioxidants that can be incorporated into the composition have the following general structures (IV), (V), and (VI):

[0025] [ka]

[0026] (In the formula, a, b, and c each independently range from 1 to 10, and in some embodiments, from 2 to 6; R 8 , R 9 , R 10 , R 11 , and R 12 are each independently hydrogen, C1 to C 10 Alkyl, and C3-C 30 branched alkyl, such as methyl, ethyl, propyl, isopropyl, butyl, or tertiary butyl groups; and R 13 , R 14 and R 15 each independently having the following general structures (VII) and (VIII):

[0027] [ka]

[0028] (In the formula, d ranges from 1 to 10, and in some embodiments, from 2 to 6; R 16 , R 17 , R 18 , and R 19 are each independently hydrogen, C1 to C 10 Alkyl, and C3-C 30 branched alkyl, for example selected from methyl, ethyl, propyl, isopropyl, butyl, or tertiary butyl groups).

[0029] Specific examples of suitable hindered phenols having the above general structure include, for example, 2,6-di-tert-butyl-4-methylphenol; 2,4-di-tert-butyl-phenol; pentaerythrityl tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate; tetrakis[methylene(3,5-di-tert-butyl-4-hydroxycinnamate)]methane; bis-2,2'-methylene- Bis(6-tert-butyl-4-methylphenol) terephthalate;1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene;Tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate;1,3,5-Tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)1,3,5-triazine-2,4,6-(1H,3H,5H)-trione;1,1,3-Tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane ;1,3,5-Triazine-2,4,6(1H,3H,5H)-trione;1,3,5-Tris[[3,5-bis-(1,1-dimethylethyl)-4-hydroxyphenyl]methyl];4,4',4"-[(2,4,6-trimethyl-1,3,5-benzenetriyl)tris-(methylene)]tris[2,6-bis-(1,1-dimethylethyl)];6-tert-butyl-3-methylphenyl;2,6-Di-tert-butyl-p-cresol;2,2'-Methylenebis(4-ethyl-6-tert-butylphenol);4,4'-Butylidene Bis(6-tert-butyl-m-cresol); 4,4'-thiobis(6-tert-butyl-m-cresol); 4,4'-dihydroxydiphenylcyclohexane; Alkylated bisphenols; Styrenated phenols; 2,6-di-tert-butyl-4-methylphenol; n-Octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate; 2,2'-methylenebis(4-methyl-6-tert-butylphenol); 4,4'-thiobis(3-methyl-6-tert-butylphenyl);Examples of suitable hydroxybenzoates include 4,4'-butylidenebis(3-methyl-6-tert-butylphenol); stearyl-β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane; 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; tetrakis[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, stearyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate; and mixtures thereof.

[0030] In one particular embodiment, the hindered phenolic antioxidant comprises tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl-propionate)].

[0031] The hindered phenolic antioxidant may generally be present in the polymer composition in an amount of about 0.2 wt. % to about 3.5 wt. %, including all 0.1 wt. % increments therebetween. For example, the hindered phenolic antioxidant may be present in the polymer composition in an amount greater than about 0.3 wt. %, such as greater than about 0.5 wt. %, such as greater than about 0.7 wt. %, such as greater than about 0.9 wt. %, such as greater than about 1.1 wt. %, such as greater than about 1.3 wt. %, such as greater than about 1.5 wt. %, such as greater than about 1.7 wt. %, such as greater than about 1.9 wt. %, or such as greater than about 2.1 wt. In one embodiment, however, the phenolic antioxidant may be present in a relatively small amount. For example, the phenolic antioxidant may be present in an amount less than about 1.5 wt. %, such as less than about 1 wt. %, such as less than about 0.8 wt. %.

[0032] As described above, the hindered phenolic antioxidant is combined with the aromatic amine stabilizer and the thioester stabilizer. The aromatic amine stabilizer may include any suitable nitrogen-containing antioxidant, such as a secondary arylamine. The aromatic amine antioxidant may be, for example, the reaction product of diphenylamine and acetone. Specific examples of aromatic amine antioxidants include 4,4'-bis(1,1'-dimethylbenzyl)diphenylamine, 2,2,4-trimethyl-1,2-dihydroquinoline, p-(p-toluenesulfonylamido)-diphenylamine, and N,N'-diphenyl-p-phenylene-diamine, 4,4'-bis(α,α-tertiaryoctyl)diphenylamine, 4,4'-bis(α-methylbenzhydryl)diphenylamine, or mixtures thereof.

[0033] In one particular embodiment, the aromatic amine stabilizer may be 4-(1-methyl-1-phenylethyl)N-[4-[1-methyl-1-phenylethyl)phenyl]aniline.

[0034] The aromatic amine stabilizer may generally be present in the polymer composition in an amount of about 0.05% to about 1.5% by weight, including all increments of 0.05% by weight therebetween. For example, the aromatic amine stabilizer may be present in the composition in an amount greater than about 0.1% by weight, such as greater than about 0.2% by weight, or greater than about 0.3% by weight. The aromatic amine stabilizer is generally present in the composition in an amount less than about 1.3% by weight, such as less than about 1% by weight, such as less than about 0.8% by weight, such as less than about 0.6% by weight, or less than about 0.5% by weight.

[0035] The thioester stabilizer present in the composition may be a thiocarboxylic acid ester. Thioester stabilizers, for example, have the following general structure: R 11 -O(O)(CH2) x -S-(CH2) y (O)OR 12 (In the formula, x and y are each independently 1 to 10, in some embodiments 1 to 6, and in some embodiments 2 to 4 (e.g., 2); R 11 and R 12 are each independently linear or branched, C6 to C 30 Alkyl, in some embodiments C 10 ~C 24 Alkyl, in some embodiments, C 12 ~C 20 alkyl, for example selected from lauryl, stearyl, octyl, hexyl, decyl, dodecyl, oleyl, and the like.

[0036]

[0033] Specific examples of suitable thiocarboxylic acid esters include distearyl thiodipropionate, dilauryl thiodipropionate, di-2-ethylhexyl-thiodipropionate, diisodecyl thiodipropionate, and the like.

[0037] In one embodiment, the thioester stabilizer may be a dicarboxylic acid ester. By way of example, in one aspect, the thioester stabilizer may include distearyl thiodipropionate.

[0038] The thioester stabilizer may generally be present in the polymer composition in an amount of about 0.03 wt.% to about 1.3 wt.%, including all increments of 0.01 wt.% therebetween. For example, the thioester stabilizer may be present in the polymer composition in an amount greater than about 0.05 wt.%, such as greater than about 0.08 wt.%, such as greater than about 0.1 wt.%, such as greater than about 0.13 wt.%, such as greater than about 0.15 wt.%, or such as greater than about 0.17 wt.%. The thioester stabilizer is generally present in the polymer composition in an amount less than about 1.1 wt.%, such as less than about 0.9 wt.%, such as less than about 0.7 wt.%, such as less than about 0.5 wt.%, or such as less than about 0.3 wt.%.

[0039] In one embodiment, the hindered phenolic antioxidant is present in the polymer composition in an amount greater than the aromatic amine stabilizer and the thioester stabilizer. The aromatic amine stabilizer may also be present in the polymer composition in an amount greater than the thioester stabilizer. In one aspect, the weight ratio of the hindered phenolic antioxidant to the aromatic amine stabilizer may be from about 10:1 to about 1:1, such as from about 5:1 to about 1:1, for example, from about 3:1 to about 1.5:1. Alternatively, the weight ratio of the hindered phenolic antioxidant to the thioester stabilizer may be from about 15:1 to about 1:1, for example, from about 8:1 to about 1.5:1, for example, from about 5:1 to about 2:1.

[0040]

[0037] The above-described stabilizer combinations are combined with polyoxymethylene polymers in formulating the polymer compositions of the present disclosure. It has been discovered that, particularly advantageously, the stabilizer combinations can be combined with polyoxymethylene polymers previously taught to be unsuitable for formulating compositions for producing acid-resistant articles. For example, those skilled in the art have taught against the use of polyoxymethylene polymers having relatively high hemiformal end group contents. For example, U.S. Patent No. 10,844,191 states that "a hemiformal end group content of 0.8 mmol / kg or less is essential" to produce a viable acid-resistant polyoxymethylene polymer composition.

[0041]

[0038] Conversely, it has been found that the combination of stabilizers can offset, and in some cases even reverse, any alleged decrease in acid resistance when formulated into a polymer composition containing a polyoxymethylene polymer with a relatively high hemiformal end group content. By way of example, while any suitable polyoxymethylene polymer may be incorporated into the composition, in one embodiment the polyoxymethylene polymer has a hemiformal end group content of greater than 0.81 mmol / kg, e.g., greater than about 0.85 mmol / kg, e.g., greater than about 0.9 mmol / kg, e.g., greater than about 0.95 mmol / kg, e.g., greater than about 1 mmol / kg, e.g., greater than about 1.2 mmol / kg. The hemiformal group content is generally less than about 3 mmol / kg, e.g., less than about 2 mmol / kg.

[0042] The content of terminal hemiformal groups in polyoxymethylene copolymers is determined as follows: The polyoxymethylene copolymer is dissolved in anhydrous hexafluoro-2-propanol (HFIP) at a concentration of 2.9-3.1 wt% at a reaction temperature of 40-50°C. In a separate vial, pyridine is added to the silylating agent, N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), at a concentration of 7.0-8.0 wt%; the solution is stirred at the reaction temperature. The amount of BSTFA used is in large excess relative to the polyoxymethylene copolymer, approximately 1.5-2 times the volume of the copolymer solution. The polyoxymethylene copolymer solution is added dropwise to the stirring BSTFA mixture, which immediately becomes turbid with precipitate. The reaction mixture is stirred at the reaction temperature for 30 minutes. The mixture is then removed from the heat and dried using a nitrogen stream. The copolymer is redissolved in HFIP and dried again, and this cycle is repeated a total of three times. A portion of the resulting silylated copolymer is dissolved in deuterated HFIP (HFIP-d2) and transferred to an NMR sample tube. 1H NMR spectra are collected at 37 °C using the residual solvent signal as an internal standard. Peaks of interest are analyzed; an example of suitable parameters includes 256 scans per spectrum, using a Bruker Avance III 400 MHz spectrometer with a flip angle of 30°. Newly formed tetramethylsilyl ether groups were observed at 0.26 (C) and 0.23 ppm, corresponding to hemiformal and hydroxyethoxy end groups, respectively. Quantification of the terminal hemiformal groups (H) is performed with respect to peaks at 4.98 ppm and 3.84 ppm, corresponding to the oxymethylene units (A) and comonomer units (B) of the polyoxymethylene copolymer:

[0043]

number

[0044] The calculations can be adjusted accordingly to include other components of the polymer structure.

[0040] The preparation of polyoxymethylene polymers can be carried out by polymerization of polyoxymethylene-forming monomers, such as trioxane or a mixture of trioxane and a cyclic acetal, such as dioxolane, in the presence of a molecular weight regulator, such as a glycol. The polyoxymethylene polymer used in the polymer composition may comprise a homopolymer or a copolymer. According to one embodiment, the polyoxymethylene is a homopolymer or copolymer containing at least 50 mol%, such as at least 75 mol%, for example at least 90 mol%, or even at least 97 mol% -CHO- repeating units.

[0045] In one embodiment, a polyoxymethylene copolymer is used. The copolymer may contain from about 0.1 mol % to about 20 mol %, particularly from about 0.5 mol % to about 10 mol %, of repeating units containing a saturated or ethylenically unsaturated alkylene group having at least two carbon atoms, or a cycloalkylene group having a sulfur atom or an oxygen atom in the chain and which may contain one or more substituents selected from the group consisting of alkylcycloalkyl, aryl, aralkyl, heteroaryl, halogen, or alkoxy. In one embodiment, a cyclic ether or acetal is used, which can be incorporated into the copolymer by a ring-opening reaction.

[0046] Preferred cyclic ethers or acetals have the formula:

[0047] [ka]

[0048] (wherein x is 0 or 1, and R 2 is a C2-C4-alkylene radical, if appropriate bearing one or more substituents which are C1-C4-alkyl or C1-C4-alkoxy groups and / or halogen atoms, preferably chlorine atoms. By way of example only, ethylene oxide, propylene 1,2-oxide, butylene 1,2-oxide, butylene 1,3-oxide, 1,3-dioxane, 1,3-dioxolane and 1,3-dioxepane may be mentioned as cyclic ethers, and linear oligoformals or polyformals, such as polydioxolanes or polydioxepanes, as comonomers.

[0049] In one embodiment, the polyoxymethylene polymer present in the polymer composition is a copolymer containing a relatively small amount of comonomer, such as dioxolane. For example, the polyoxymethylene copolymer may contain less than about 2 wt. % of comonomer units, such as less than about 1.8 wt. %, for example, less than about 1.7 wt. %, for example, less than about 1.6 wt. %. The comonomer content of the polyoxymethylene copolymer may generally be greater than about 0.3 wt. %, for example, greater than about 0.5 wt. %, for example, greater than about 0.7 wt. %, for example, greater than about 0.9 wt. %, for example, greater than about 1.1 wt. %, for example, greater than about 1.3 wt. %.

[0050] The polymerization can take place as a precipitation polymerization or in the melt. By appropriately selecting the polymerization parameters, such as the polymerization duration or the amount of molecular weight regulator, the molecular weight of the resulting polymer, and therefore the MVR value, can be adjusted.

[0051] In one embodiment, the polyoxymethylene polymer used in the polymer composition may contain a relatively large amount of reactive or functional groups at the terminal positions. The reactive groups may include, by way of example, —OH or —NH groups.

[0052]

[0001] In one embodiment, a polyoxymethylene polymer may optionally have terminal hydroxyl groups, e.g., hydroxyethylene groups and / or hydroxyl side groups, at least about 50% of all terminal sites on the polymer. By way of example, a polyoxymethylene polymer may have at least about 70%, e.g., at least about 80%, e.g., at least about 85%, of its end groups being hydroxyl groups, based on the total number of end groups present. It is understood that the total number of end groups present includes all terminal side groups. Quantification of the hydroxyl group content in a polyoxymethylene polymer can be carried out by the method described in JP-A-2001-11143, which is incorporated herein by reference.

[0053] In one embodiment, the polyoxymethylene polymer optionally has a terminal hydroxyl group content of at least 15 mmol / kg, e.g., at least 18 mmol / kg, e.g., at least 20 mmol / kg. In one embodiment, the terminal hydroxyl group content is in the range of 18 to 80 mmol / kg. In an alternative embodiment, the polyoxymethylene polymer may contain terminal hydroxyl groups in an amount less than 100 mmol / kg, e.g., less than 50 mmol / kg, e.g., less than 20 mmol / kg, e.g., less than 18 mmol / kg, e.g., less than 15 mmol / kg. By way of example, the polyoxymethylene polymer may contain terminal hydroxyl groups in an amount of from about 5 mmol / kg to about 20 mmol / kg, e.g., from about 5 mmol / kg to about 15 mmol / kg. For example, a polyoxymethylene polymer having a low terminal hydroxyl group content but a high melt volume-flow rate may be used.

[0054] In addition to or instead of the terminal hydroxyl groups, the polyoxymethylene polymer may also have other terminal groups common to these polymers. Examples of these are alkoxy groups, the above-mentioned hemiformal groups, acetate groups or aldehyde groups. According to one embodiment, the polyoxymethylene is a homopolymer or copolymer containing at least 50 mol%, for example at least 75 mol%, for example at least 90 mol%, or even at least 95 mol% -CHO- repeating units.

[0055] In one embodiment, polyoxymethylene polymers can be produced by a cationic polymerization process followed by solution hydrolysis to remove some of the unstable end groups. During cationic polymerization, glycols such as ethylene glycol or methylal can be used as chain terminators. Heteropolyacids, triflic acids, or boron compounds can be used as catalysts.

[0056] The polyoxymethylene polymer may be of any suitable molecular weight. The molecular weight of the polymer may be, for example, from about 4,000 grams per mole to about 20,000 g / mol. In other embodiments, however, the molecular weight may be significantly greater than 20,000 g / mol, for example, from about 20,000 g / mol to about 200,000 g / mol.

[0057] The polyoxymethylene polymer present in the composition may generally have a melt flow index (MFI) ranging from about 1 to about 50 g / 10 min, e.g., from about 9 g / 10 min to about 27 g / 10 min, as determined according to ISO Test 1133 at 190°C and 2.16 kg, although polyoxymethylenes having higher or lower melt flow indices are also encompassed herein. In one embodiment, the polyoxymethylene polymer generally has a melt flow index greater than about 10 g / 10 min. For example, the polyoxymethylene polymer may have a melt flow index greater than about 11 g / 10 min, or even greater than about 12 g / 10 min. The polyoxymethylene polymer may have a melt flow index less than about 35 g / 10 min, e.g., less than about 30 g / 10 min, e.g., less than about 25 g / 10 min, e.g., less than about 20 g / 10 min, e.g., less than about 14 g / 10 min. In one embodiment, the polyoxymethylene polymer may have a relatively low melt flow index, less than about 5 g / 10 min, such as less than about 4 g / 10 min, for example less than about 3 g / 10 min, and generally greater than about 0.1 g / 10 min.

[0058] The polyoxymethylene polymer may be present in the polyoxymethylene polymer composition in an amount of at least 50 wt.%, for example at least 60 wt.%, for example at least 75 wt.%, for example at least 80 wt.%, for example at least 85 wt.%, for example at least 90 wt.%, for example at least 93 wt.%. Generally, the polyoxymethylene polymer is present in an amount of less than about 100 wt.%, for example less than about 97 wt.%, for example less than about 95 wt.%, where the weight is based on the total weight of the polyoxymethylene polymer composition.

[0059]

[0052] In accordance with the present disclosure, the polyoxymethylene polymer is combined with at least one acid neutralizing agent and, optionally, a plasticizer. The acid neutralizing agent generally comprises a metal compound and / or a hydroxide, oxide, sulfide, or carbonate.

[0060]

[0053] In one embodiment, at least one of the acid neutralizing agents is a magnesium compound. For example, the polymer composition of the present disclosure can contain a single magnesium compound or multiple magnesium compounds. Particularly suitable compounds for use in the present disclosure include magnesium hydroxide alone, magnesium oxide alone, or a combination of magnesium hydroxide and magnesium oxide. According to the present disclosure, one or more magnesium compounds are added to the polymer composition to achieve a specific magnesium content that has been found to be particularly suitable for providing acid resistance. For example, the magnesium content of the polymer composition can be greater than about 1.8 wt%, for example, greater than about 2 wt%, for example, greater than about 2.2 wt%, for example, greater than about 2.4 wt%, for example, greater than about 2.6 wt%, for example, greater than about 2.8 wt%, for example, greater than about 3 wt%, for example, greater than about 3.2 wt%, for example, greater than about 3.4 wt%, or for example, greater than about 3.6 wt%. The magnesium content of the polymer composition is generally less than about 8.5 wt%, such as less than about 7 wt%, for example less than about 6 wt%, for example less than about 5 wt%. In one embodiment, the magnesium content of the polymer composition is less than about 4.1 wt%.

[0061] In one embodiment, the polymer composition contains only magnesium oxide. The magnesium oxide may be present in the polymer composition in an amount sufficient to provide a magnesium content of the polymer composition of from about 2.5% to about 6.5% by weight.

[0062] In an alternative embodiment, the polymer composition may contain magnesium hydroxide, either alone or in combination with magnesium oxide. The magnesium hydroxide may be present in the polymer composition such that the magnesium hydroxide accounts for about 0.6% to about 4.5% by weight of magnesium relative to the polymer composition. For example, magnesium hydroxide may be added to the polymer composition to provide a magnesium content of greater than about 0.8 wt.%, e.g., greater than about 1.2 wt.%, e.g., greater than about 1.5 wt.%, e.g., greater than about 1.8 wt.%, e.g., greater than about 2 wt.%, e.g., greater than about 2.2 wt.%, e.g., greater than about 2.5 wt.%, e.g., greater than about 2.8 wt.%, e.g., greater than about 3 wt.%, e.g., greater than about 3.2 wt.%, e.g., greater than about 3.5 wt.%, and generally less than about 6.3 wt.%, e.g., less than about 5.5 wt.%, e.g., less than about 4.1 wt.%. As noted above, the magnesium hydroxide may be present alone or in combination with magnesium oxide. When magnesium oxide is present in conjunction with magnesium hydroxide, the magnesium oxide may also be present to provide the same amount of magnesium content to the polymer composition as noted above for magnesium hydroxide.

[0063] In addition to one or more magnesium compounds, various other acid neutralizing agents can also be added to the polymer composition. By way of example, other acid neutralizing agents that may be used include zinc oxide, zinc sulfide, sulfur sulfide, calcium carbonate, or mixtures thereof.

[0064] In one embodiment, the acid neutralizers may combine a relatively small particle size with a high surface area. Each acid neutralizer may have, for example, about 25 ml 2 / g, e.g., about 35m 2 / g, e.g., about 45m 2 / g, e.g., about 55m 2 / g, e.g., about 65m 2 / g, e.g., about 75m 2 / g, e.g., about 85m 2 / g, e.g., about 95m 2 / g, e.g., about 105m 2 / g, e.g., about 115m 2 / g, e.g., about 125m 2 / g, e.g., about 135m 2 / g, e.g., about 145m 2 / g, e.g., about 155m 2 / g, e.g., about 165m 2 / g, e.g., about 175m 2 / g, e.g., about 185m 2 / g, e.g., about 195m 2 / g, e.g., about 205m 2 / g, e.g., about 215m 2 / g. The BET surface area is generally about 400 m 2 / g.

[0065] In one embodiment, the one or more acid neutralizing agents are present in the polymer composition in an amount greater than 2 wt%, such as greater than 2.5 wt%, for example greater than about 3 wt%, for example greater than about 3.5 wt%, for example greater than about 4 wt%, for example greater than about 4.5 wt%, for example greater than about 5 wt%, such as greater than about 5.2 wt%, for example greater than about 5.5 wt%, for example greater than about 5.7 wt%, for example greater than about 6 wt%, for example greater than about 6.5 wt%, for example greater than about 7 wt%, for example greater than about 8 wt%, for example greater than about 9 wt%, for example greater than about 10 wt%, for example greater than about 11 wt%, for example greater than about 12 wt%. The one or more acid neutralizing agents are generally present in the composition in an amount of less than about 25% by weight, such as less than about 22% by weight, for example less than about 20% by weight, such as less than about 18% by weight, for example less than about 15% by weight, such as less than about 12% by weight, for example less than about 10% by weight, for example less than about 8% by weight.

[0066] In addition to the polyoxymethylene polymer and the acid neutralizing agent, the polymer composition may further contain a plasticizer, which may include a polyalkylene glycol, ester, polyester, epoxide, sulfonamide, polyether, polyamide, polybutene, acetylated monoglyceride, alkyl citrate, organic phosphate ester, or a mixture thereof.

[0067]

[0060] For example, in one embodiment, the plasticizer comprises polyethylene glycol. The average molecular weight of the plasticizer is generally greater than about 1,000 g / mol, such as greater than about 3,000 g / mol, and may be greater than about 5,000 g / mol. The average molecular weight of the plasticizer is generally less than about 55,000 g / mol, such as less than about 30,000 g / mol, such as less than about 15,000 g / mol, and may be less than about 8,000 g / mol.

[0068] In an alternative embodiment, the plasticizer may have an ester functionality and may include phthalates, adipates, sebacates, maleates, trimellitates, benzoates, or mixtures thereof. Examples of suitable phthalates are diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), diisoheptyl phthalate (DIHP), L 79 phthalate, L 711 phthalate, dioctyl phthalate, diisooctyl phthalate, dinonyl phthalate, diisononyl phthalate, diisodecyl phthalate, L 911 phthalate, diundecyl phthalate, diisoundecyl phthalate, undecyl dodecyl phthalate, diisotridecyl phthalate (DTDP), and butyl benzyl phthalate (BBP).

[0069]

[0062] Examples of adipate esters are dioctyl adipate, diisononyl adipate, and diisodecyl adipate. An example of a trimellitate ester is trioctyl trimellitate. Phosphate esters can also be used. Suitable examples are tri-2-ethylhexyl phosphate, 2-ethylhexyl diphenyl phosphate, and tricresyl phosphate.

[0070] Sebacate and azelate esters include di-2-ethylhexyl sebacate (DOS) and di-2-ethylhexyl azelate (DOZ).

[0071]

[0064] Polyester plasticizers are usually based on the condensation products of propanediol or butanediol with adipic acid or phthalic anhydride. The growing polymer chains of these polyesters may then be end-capped with alcohols or monobasic acids, although strict control of the reaction stoichiometry can produce unend-capped polyesters.

[0072] Further plasticizers are benzoic acid esters commercially available as JAYFLEX® MB10, BENZOFLEX® 2088, BENZOFLEX® LA-705, and BENXOFLEX® 9-88. Epoxide plasticizers include epoxidized vegetable oils.

[0073] In one embodiment, the plasticizer is an aromatic benzenesulfonamide, represented by the general formula (I):

[0074] [ka]

[0075] (wherein R1 represents a hydrogen atom, a C1-C4 alkyl group or a C1-C4 alkoxy group, and X represents a linear or branched C2-C 10 represents an alkylene group, or an alkyl group, or a methylene group, or an alicyclic group, or an aromatic group; Y represents a group H, OH or

[0076] [ka]

[0077] Preference is given to benzenesulfonamides represented by the formula: wherein R2 represents one of a C1-C4 alkyl group or an aromatic group, which groups may themselves optionally be substituted by OH or a C1-C4 alkyl group.

[0078] Preferred aromatic benzenesulfonamides of formula (I) are: R1 represents a hydrogen atom or a methyl or methoxy group, and X represents a linear or branched C2-C 10 represents an alkylene group or a phenyl group, Y represents an H, OH or —O—CO—R group, R representing a methyl or phenyl group, the latter optionally being itself substituted by an OH or methyl group.

[0079] Among the aromatic sulfonamides of formula (I) which are liquid (L) or solid (S) at room temperature as specified below, the following products may be mentioned together with their assigned abbreviations: N-(2-hydroxyethyl)benzenesulfonamide (L), N-(3-hydroxypropyl)benzenesulfonamide (L), N-(2-hydroxyethyl)-p-toluenesulfonamide (S), N-(4-hydroxyphenyl)benzenesulfonamide (S), N-[(2-hydroxy-1-hydroxymethyl-1-methyl)ethyl]benzenesulfonamide (L), N-[5-hydroxy-1,5-dimethylhexyl]benzenesulfonamide (S), N-(2-acetoxyethyl)benzenesulfonamide (S), N-(5-hydroxypentyl)benzenesulfonamide (L), N-[2-(4-hydroxybenzoyloxy)ethyl]benzene-sulfonamide (S), N-[2-(4-methylbenzoyloxy)ethyl]benzenesulfonamide (S), N-(2-hydroxyethyl)-p-methoxybenzenesulfonamide (S) and N-(2-hydroxypropyl)benzenesulfonamide (L).

[0080] One particular plasticizer is a sulfonamide, such as N-(n-butyl)benzenesulfonamide. The amount of plasticizer present in the polymer composition can depend on the amount of acid neutralizer present as well as various other factors. Generally, the plasticizer is present in the composition in an amount greater than about 0.8 wt %, for example, greater than about 1.2 wt %, for example, greater than about 1.6 wt %, for example, greater than about 1.8 wt %. The plasticizer is generally present in an amount less than about 12 wt %, for example, less than about 8 wt %, for example, less than about 6 wt %, for example, less than about 3 wt %.

[0081] In addition to the polyoxymethylene polymer, stabilizer combination, at least one acid neutralizer, and plasticizer, various other ingredients and materials may be included in the composition to improve one or more properties. For example, in one embodiment, the composition may contain a conductive filler so that any article molded from the composition exhibits electrostatic dissipative (ESD) capabilities. The conductive filler may include conductive particles, powders, fibers, or combinations thereof. By way of example, the conductive filler may include metal powder, metal flakes, metal fibers (i.e., stainless steel fibers), carbon powder, carbon fibers, carbon black, carbon nanotubes, or combinations thereof.

[0082]

[0072] Furthermore, the conductive filler may be present in the polymer composition of the present disclosure in an amount ranging from about 1 wt% to about 30 wt%, for example, in an amount ranging from about 1.5 wt% to about 25 wt%, for example, in an amount ranging from about 2 wt% to about 20 wt%, based on the total weight of the polymer composition.

[0083] In one embodiment, a copolyamide may be present in the polymer composition to reduce formaldehyde emissions. The copolyamide generally has a softening point greater than about 120°C, such as greater than about 130°C, such as greater than about 140°C, such as greater than about 150°C, such as greater than about 160°C, or such as greater than about 170°C. The copolyamide may have a softening point less than about 210°C, such as less than about 200°C, such as less than about 190°C, or such as less than about 185°C. The copolyamide may have a melt viscosity greater than about 7 Pa s, such as greater than about 8 Pa s, or such as greater than about 9 Pa s, at 230°C. The melt viscosity is generally less than about 15 Pa s, such as less than about 14 Pa s, or such as less than about 13 Pa s. In one embodiment, the copolyamide is ethanol-soluble. In one embodiment, the copolyamide may comprise a polycondensate of a polymeric fatty acid and an aliphatic diamine. The copolyamide may generally be present in the composition in an amount greater than about 0.01 wt %, such as greater than about 0.03 wt %, for example greater than about 0.05 wt %. The copolyamide is generally present in an amount less than about 2 wt %, such as less than about 1.5 wt %, for example less than about 1 wt %, for example less than about 0.5 wt %, for example less than about 0.1 wt %.

[0084] In one embodiment, an acid scavenger may be present. The acid scavenger may, for example, include an alkaline earth metal salt. For example, the acid scavenger may include a calcium salt, such as calcium citrate or calcium carbonate. In one embodiment, the acid scavenger may include tricalcium citrate. The acid scavenger may be present in an amount of at least about 0.01 wt.%, such as at least about 0.05 wt.%, for example at least about 0.09 wt.%. In one embodiment, for example, when the acid scavenger is a carbonate salt, a greater amount of acid scavenger is used. For example, the acid scavenger may be present in an amount greater than about 2 wt.%, such as greater than about 5 wt.%, for example greater than about 7 wt.%. The acid scavenger is generally present in an amount of less than about 10 wt.%, for example less than about 7 wt.%, for example less than about 5 wt.%, for example less than about 1 wt.%, for example less than about 0.75 wt.%, for example less than about 0.5 wt.%, where the weight is based on the total weight of the respective polymer composition.

[0085] In one embodiment, a nucleating agent may be present. The nucleating agent may increase crystallinity and may include an oxymethylene terpolymer. In one particular embodiment, for example, the nucleating agent may include a terpolymer of butanediol diglycidyl ether, ethylene oxide, and trioxane. In one embodiment, the terpolymer nucleating agent may have a relatively small particle size, for example, a d50 particle size of less than about 1 micron, for example, less than about 0.8 microns, for example, less than about 0.6 microns, for example, less than about 0.4 microns, and generally greater than 0.01 microns. Other nucleating agents that can be used include polyamide, boron nitride, or talc. The polyamide nucleating agent may be PA6 or PA12. The nucleating agent may be present in the composition in an amount of at least about 0.01 wt.%, for example at least about 0.05 wt.%, for example at least about 0.1 wt.%, and less than about 2 wt.%, for example less than about 1.5 wt.%, for example less than about 1 wt.%, where the weight is based on the total weight of the respective polymer composition.

[0086] In one embodiment, a lubricant may be present. The lubricant may comprise a polymer wax composition. In one embodiment, a fatty acid amide, such as ethylene bis(stearamide), may be present. In an alternative embodiment, the lubricant may comprise a polyalkylene glycol having a relatively low molecular weight compared to the plasticizer. By way of example, the lubricant may comprise polyethylene glycol having an average molecular weight of about 500 to about 4,000. The lubricant may generally be present in the polymer composition in an amount of at least about 0.01 wt.%, e.g., at least about 0.05 wt.%, e.g., at least about 0.1 wt.%, and less than about 1 wt.%, e.g., less than about 0.75 wt.%, e.g., less than about 0.5 wt.%, where the weights are based on the total weight of the respective polymer composition.

[0087] In one embodiment, a colorant may be present. Colorants that can be used include any desirable inorganic pigments, such as titanium dioxide, ultramarine blue, cobalt blue, and other organic pigments and dyes, such as phthalocyanines, anthraquinones, and the like. Other colorants include carbon black or various other polymer-soluble dyes. In one embodiment, a combination of colorants may be included in the polymer composition. For example, the polymer composition may contain carbon black. In an alternative embodiment, the colorant present in the polymer composition may include titanium dioxide in combination with at least one colored pigment, such as a yellow pigment and a green pigment, and optionally further in combination with carbon black. The colorant may be present in the composition in an amount of at least about 0.01 wt.%, such as at least about 0.05 wt.%, such as at least about 0.1 wt.%, such as at least about 0.5 wt.%, and less than about 5 wt.%, such as less than about 2.5 wt.%, such as less than about 1 wt.%, where the weights are based on the total weight of the respective polymer composition.

[0088] One or more light stabilizers may also be included in the composition. In one embodiment, in addition to the ultraviolet light stabilizer, a light stabilizer, such as a sterically hindered amine, may be present. Examples of hindered amine light stabilizers that can be used include N-methylated oligomeric hindered amine compounds. For example, the hindered amine light stabilizer may include a high molecular weight hindered amine stabilizer. When present, the light stabilizer may be present in the polymer composition in an amount of at least about 0.01 wt.%, such as at least about 0.05 wt.%, for example at least about 0.075 wt.%, and less than about 1 wt.%, for example less than about 0.75 wt.%, for example less than about 0.5 wt.%, where the weight is based on the total weight of the respective polymer composition.

[0089] In one embodiment, an ultraviolet light stabilizer may be present. The ultraviolet light stabilizer may include a benzophenone, a benzotriazole, or a benzoic acid ester. When present, the ultraviolet light absorber may be present in the polymer composition in an amount of at least about 0.01 wt.%, for example, at least about 0.05 wt.%, for example, at least about 0.075 wt.%, and less than about 1 wt.%, for example, less than about 0.75 wt.%, for example, less than about 0.5 wt.%, where the weight is based on the total weight of the respective polymer composition.

[0090]

[0080] However, in one embodiment, the polymer composition does not include any light stabilizers. For example, the composition may be free of ultraviolet light stabilizers or hindered amine light stabilizers.

[0091] In one aspect, nitrogen-containing formaldehyde scavengers may be optionally present in the polymer composition. However, in an alternative embodiment, the polymer composition can be formulated to be completely free of any nitrogen-containing formaldehyde scavengers. Among these are primarily heterocyclic compounds having at least one nitrogen atom as a heteroatom adjacent to either an amino-substituted carbon atom or a carbonyl group, such as pyridine, pyrimidine, pyrazine, pyrrolidone, aminopyridine, and compounds derived therefrom. Such compounds include triamino-1,3,5-triazine (melamine) and its derivatives, such as melamine-formaldehyde condensates and methylolmelamine. Other compounds include guanamine compounds.

[0092] The polymer composition may also optionally contain one or more reinforcing materials. By way of example, the polymer composition may contain reinforcing fibers, such as glass fibers, carbon fibers, etc. The reinforcing fibers may generally be present in an amount of from about 2% to about 40% by weight, for example, from about 10% to about 25% by weight.

[0093] The compositions of the present disclosure can be combined and formed into polymeric articles using any technique known in the art. For example, the individual compositions can be vigorously mixed to form a substantially homogeneous blend. The blend can be melt-mixed at elevated temperatures, e.g., above the melting point but below the decomposition temperature of the polymers utilized in the polymer composition. Alternatively, the individual compositions can be melted and mixed together in a conventional single- or twin-screw extruder. Preferably, melt-mixing is carried out at a temperature ranging from 100 to 280°C, e.g., from 120 to 260°C, e.g., from 140 to 240°C, or from 180 to 220°C.

[0094] After extrusion, the composition can be formed into pellets, which can be molded into polymeric articles by techniques known in the art, such as injection molding, thermoforming, blow molding, rotational molding, and the like.

[0095] In one embodiment, the polymer composition can be used to manufacture a polymer article designed for the automotive field. The polymer article can be, for example, designed to be an exterior vehicle part. In one embodiment, the molded article is formed into a fuel contact member. The fuel contact member can be, for example, one or more components contained in a fuel system of a vehicle, such as an automobile or truck. The fuel contact member can be, for example, designed for repeated contact with diesel fuel.

[0096]

[0086] Referring to Figure 1, an exemplary fuel line 100 formed from the polymer composition of the present disclosure is shown. In this embodiment, the fuel line 100 includes, by way of example, a corrugated pipe.

[0097]

[0087] In addition to fuel lines, the polymer compositions of the present disclosure can be used to manufacture fuel tanks, fuel pump components, fuel filter components, fuel rails, injector components, pressure regulators, and return fuel lines.

[0098] In one embodiment, the polymer composition is used to manufacture a fuel flange 200, as shown in FIG. 2. The fuel flange 200 is designed to be installed on a fuel tank and connected to one or more fuel lines, for example. For example, as shown in FIG. 2, the fuel flange 200 may include at least one fuel inlet or outlet 202 for supplying fuel to and dispensing fuel from the fuel tank. The fuel flange 200 may also include an electrical connector 204 for connecting a controller contained within the vehicle to various sensors that may be present in and around the fuel tank.

[0099] The polymer composition may have a combination of physical properties and acid resistance that make it suitable for many applications in addition to use in fuel-related applications. For example, when tested according to GM test GMW18052, the polymer composition may exhibit acid resistance of greater than 30 cycles at 75% tensile stress, acid resistance of greater than 10 cycles at 35% tensile stress, a tensile modulus of greater than 2500 MPa, a tensile yield strength of greater than 54 MPa, and a tensile modulus of greater than 4 kJ / m 2 It exhibits a notched Charpy impact strength at 23°C greater than 3kJ / m 2 It exhibits a notched Charpy impact strength at -30°C greater than 1.4g / cm 3 ~1.46g / cm 3 a density of 1000 to 1500 MPa, a melting temperature of 168°C to 175°C, a DTUL of greater than 90°C, and a melt flow rate of 9 g / 10 min to 16 g / 16 min. For example, the polymer composition may exhibit a tensile modulus of greater than 2800 MPa, e.g., greater than 3000 MPa, and typically less than 4500 MPa, a tensile yield strength of greater than 56 MPa, e.g., greater than 58 MPa, and typically less than 70 MPa, and a viscosity of about 5 kJ / m 2 greater, e.g., about 5.5 kJ / m 2 greater, and generally around 9 kJ / m 2 It exhibits a notched Charpy impact strength at 23°C of less than 5kJ / m 2 Larger, e.g., about 5.4 kJ / m 2 greater, and generally around 8.5 kJ / m 2 The Charpy notched impact strength at -30°C is less than 100%.

[0100]

[0090] The present disclosure may be better understood with reference to the following examples. [Example]

[0101] The following examples are provided to further illustrate the present invention, but not to limit its scope. Other variations of the present invention will be readily apparent to those skilled in the art and are encompassed by the appended claims.

[0102] Example 1 In this example, various polymer compositions were formulated and tested for resistance to strong acid solutions. The polymer compositions were also tested for various physical properties.

[0103] The following polymer compositions were prepared:

[0104] [Table 1]

[0105] The above compositions were injection molded into tensile test specimens and tested for their media resistance to acidic car wash solutions. Eagle One® Etching Mag Wheel Cleaner (pH 2-3) manufactured by Energizer Holdings was used as the test medium. Test specimens were tested in triplicate as follows: 1. Each specimen was clamped at 2% bending strain. The fixture used was a two-point bending apparatus, and the % strain was controlled by the distance between the two end plates. 2. At the beginning of the day, the specimens were sprayed with the vehicle and covered with gauze to soak. 3. The test specimen was placed in an oven at 60±3°C for 4 hours. 4. After removal from the oven, the specimens were sprayed with the medium and left to soak under gauze at room temperature for 4 hours. 5. After 4 hours, the specimens were sprayed again with the vehicle and allowed to soak under gauze overnight at room temperature. 6. The processes from 1 to 4 were considered as one cycle, and the cycle was repeated until the specimen was completely destroyed. 7. Before each spray, the specimens were visually inspected using a magnifying glass and light for cracks or changes in appearance.

[0106] The following results were obtained (also shown in Figure 3):

[0107] [Table 2]

[0108] Samples 1 and 2 showed dramatic media resistance compared to Sample 3, which contained only polyoxymethylene polymer. While both Samples 1 and 2 showed excellent results, Sample 2, which contained a polyoxymethylene polymer with a higher hemiformal end group content, actually showed more resistance to acid. This result was completely unexpected.

[0109]

[0097] These and other modifications and variations to the present invention may be made by those skilled in the art without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged in whole or in part. Furthermore, those skilled in the art will appreciate that the foregoing description is by way of example only and is not intended to limit the invention as set forth in the appended claims.

Claims

1. 1. A polymer composition having acid-resistant properties, comprising: polyoxymethylene polymers, Acid neutralizers, and a combination of stabilizers, (a) a hindered phenolic antioxidant, (b) an aromatic amine stabilizer, and (c) thioester stabilizers The polymer composition comprising:

2. 2. The polymer composition of claim 1, wherein the polyoxymethylene polymer comprises a polyoxymethylene copolymer containing hemiformal end groups in an amount greater than about 0.8 mmol / kg, such as greater than about 0.85 mmol / kg, for example greater than about 0.9 mmol / kg, for example greater than about 0.95 mmol / kg, for example greater than about 1 mmol / kg, and generally less than about 4 mmol / kg, for example less than about 2 mmol / kg.

3. 10. The polymer composition of claim 1, wherein a hindered phenolic antioxidant is present in the composition in an amount greater than the amount of aromatic amine stabilizer present in the composition and greater than the amount of thioester stabilizer present in the composition.

4. 2. The polymer composition of claim 1, wherein the hindered phenolic antioxidant is present in a weight ratio to the aromatic amine stabilizer of from about 10:1 to about 1:1, such as from about 5:1 to about 1:1, for example, from about 3:1 to about 1.5:1, and wherein the hindered phenolic antioxidant is present in the composition in a weight ratio to the thioester stabilizer of from about 15:1 to about 1:1, such as from about 8:1 to about 1.5:1, for example, from about 5:1 to about 2:

1.

5. 10. The polymer composition of claim 1, wherein the hindered phenolic antioxidant is present in the composition in an amount of from about 0.2% to about 3.5% by weight.

6. 2. The polymer composition of claim 1, wherein the hindered phenolic antioxidant is present in the composition in an amount less than about 1.5 wt%, such as less than about 1 wt%, for example less than about 0.8 wt%, and generally greater than about 0.2 wt%.

7. 10. The polymer composition of claim 1, wherein the hindered phenolic antioxidant comprises tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl-propionate)].

8. 10. The polymer composition of claim 1, wherein the aromatic amine stabilizer comprises 4-(1-methyl-1-phenylethyl)N-[4-(1-methyl-1-phenylethyl)phenyl]aniline.

9. 9. The polymer composition of claim 8, wherein the aromatic amine stabilizer is present in the polymer composition in an amount of from about 0.05% to about 1.5% by weight.

10. The polymer composition of claim 1 , wherein the thioester stabilizer comprises distearyl thiodipropionate.

11. A thioester stabilizer is added to the polymer composition in an amount of about 0.03% to about 1.3% by weight. The polymer composition of claim 1 .

12. 10. The polymer composition of claim 1, wherein the acid neutralizing agent is present in the polymer composition in an amount greater than about 2.5 wt%, such as greater than about 3.5 wt%, for example greater than about 4.5 wt%, for example greater than about 5.5 wt%, and generally less than about 15 wt%, for example less than about 10 wt%.

13. The polymer composition of claim 1 , wherein the acid neutralizing agent comprises magnesium oxide.

14. 14. The polymer composition of claim 13, wherein the only acid neutralizing agent present in the composition is magnesium oxide.

15. 10. The polymer composition of claim 1, wherein the acid neutralizing agent comprises magnesium hydroxide, alone or in combination with a metal oxide, such as magnesium oxide or zinc oxide.

16. The polymer composition of claim 1 further comprising a plasticizer.

17. 17. The polymer composition of claim 16, wherein the plasticizer comprises a polyalkylene glycol, such as polyethylene glycol.

18. The polymer composition of claim 1 further comprising a lubricant.

19. 10. The polymer composition of claim 1, wherein the polyoxymethylene polymer has a melt flow index greater than about 5 g / 10 min, e.g., greater than about 10 g / 10 min, and less than about 50 g / 10 min, e.g., less than about 30 g / 10 min, when tested according to ISO test 1133 at 190°C and 2.16 kg load, and the polyoxymethylene polymer is present in the polymer composition in an amount of from about 40 wt% to about 95 wt%.

20. Acid resistance greater than 30 cycles while maintaining 75% tensile stress, acid resistance greater than 10 cycles while maintaining 35% tensile stress, a tensile modulus greater than 2500 MPa, a tensile yield strength greater than 54 MPa, and a viscosity of 4 kJ / m ２ It exhibits a notched Charpy impact strength at 23°C greater than 3 kJ / m ２ It exhibits a notched Charpy impact strength at -30°C greater than 1.4 g / cm ３ ~1.46g / cm ３ 2. The polymer composition of claim 1, wherein the polymer composition exhibits a density of from about 100 to about 150° C., a melting temperature of from about 168° C. to about 175° C., a DTUL of greater than about 90° C., and a melt flow rate of from about 9 g / 10 min to about 16 g / 16 min.

21. A molded article made from the polymer composition of any of claims 1 to 20, including exterior vehicle parts.

22. 22. The molded article of claim 21, wherein the exterior vehicle part comprises a fuel contact component.

23. 22. The molded article of claim 21, comprising a fuel line or a fuel flange.

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