Chemical resistant polyoxymethylene polymer compositions

Abstract

Polyoxymethylene polymer compositions and molded articles made from the compositions that are fuel resistant, in particular diesel resistant, and resistant to high acid solutions are disclosed. The polymer composition typically contains polyoxymethylene polymer in an amount of from about 90% to about 95% by weight. In addition, the polymer composition contains an acid neutralizer and a plasticizer in a weight ratio, which has been found to significantly improve the acid resistance of the composition.

Description

[0001] Related Applications

[0002] This application is based upon and claims priority to U.S. Provisional Patent Application Serial No. 62 / 502,091, filed May 5, 2017, and U.S. Provisional Patent Application Serial No. 62 / 599,373, filed December 15, 2017, both of which are incorporated herein by reference.

[0003] BACKGROUND

[0004] Polyacetal polymers, commonly known as polyoxymethylene, have been identified as an engineering material that is particularly useful in many applications. For example, polyoxymethylene polymers are widely used in the construction of molded parts, such as parts used in the automotive and electrical industries. Polyoxymethylene polymers, for example, have excellent mechanical properties, fatigue resistance, abrasion resistance, chemical resistance, and moldability.

[0005] Because of their excellent mechanical properties, heat resistance, and chemical resistance, polyoxymethylene polymers have been used in the past to produce parts for various vehicles, such as passenger cars and trucks. For example, because polyoxymethylene polymers do not degrade significantly when exposed to fuel oil, molded parts made from polyoxymethylene polymers have been used to produce fuel lines and other vehicle parts where the parts are repeatedly exposed to vehicle fuel oil. In addition to being fuel oil resistant, the polyoxymethylene polymer compositions also have good impact resistance, which makes molded parts made from the polymer resistant to damage or crack formation during normal wear.

[0006] However, polyoxymethylene compositions face special problems when designed to be exposed to diesel fuel. For example, diesel fuel can contain sulfur or sulfur-containing compounds. When diesel fuel is heated for long periods of time, the sulfur-containing compounds can oxidize and produce acidic sulfur compounds, which can decompose many different synthetic polymers, including polyoxymethylene polymers. As a result, in the past, polyoxymethylene polymers have been combined with various different additives, such as hindered amine light stabilizers or zinc oxide, in order to make the polymer more resistant to exposure to corrosive agents that can be formed from diesel fuel.

[0007] Recently, an increasing number of passenger cars and trucks are being manufactured with decorative wheel rims for vehicle tires. In many cases, the decorative wheel rims are made from polished metals, chrome, and the like. In order to clean these materials, consumer and commercial passenger car and truck washing facilities typically use high-acid wheel cleaners. For example, the wheel cleaners can have a pH of less than 3 and even less than 2. Recently, it has been discovered that the wheel cleaners can inadvertently be sprayed onto parts of the fuel system when applied to the vehicle wheel rims.

[0008] For example, when a wheel cleaner is sprayed onto the wheel rim or tire, a highly acidic cleaner can penetrate through the wheel and remain on the fuel components. For example, a highly acidic solution such as a wheel cleaner can cause parts made of polyoxymethylene polymers to rapidly age and cause damage to occur over time.

[0009] Accordingly, there is currently a need for polyoxymethylene polymer compositions that are not only resistant to fuel (e.g., resistant to diesel fuel), but also resistant to highly acidic solutions such as wheel cleaners.

[0010] SUMMARY

[0011] In general, the present disclosure relates to a polyoxymethylene polymer composition containing primarily polyoxymethylene polymers and molded products made from the composition. The polyoxymethylene polymer composition of the present disclosure is specifically formulated to be resistant to fuel and to acids. More particularly, the polyoxymethylene polymer composition of the present disclosure and articles molded from the composition are particularly suitable for contact with various fuels, including diesel fuel, and for contact with highly acidic liquids such as various cleaners. The articles molded according to the present disclosure do not degrade, crack, or fail even after prolonged repeated contact with fuel and acidic solutions.

[0012] For example, in one embodiment, the polyoxymethylene polymer composition of the present disclosure includes a combination of polyoxymethylene polymers with an acid neutralizer and a plasticizer. More particularly, the composition not only contains polyoxymethylene polymers in an amount greater than at least 60 percent by weight, but also contains an acid neutralizer and a plasticizer in a particular weight ratio that has been found to result in a polyoxymethylene polymer composition that is not only resistant to diesel fuel, but also resistant to many highly acidic liquids, such as wheel and rim cleaners.

[0013] For example, the polyoxymethylene polymers can include polyoxymethylene copolymers and can be present in the polyoxymethylene polymer composition in an amount greater than about 70 percent by weight, for example, in an amount greater than about 80 percent by weight, for example, in an amount greater than about 90 percent by weight. In one embodiment, the polyoxymethylene polymers are present in the polyoxymethylene polymer composition in an amount less than about 96 percent by weight, for example, in an amount less than about 95 percent by weight. The polyoxymethylene polymers can have a melt flow index greater than about 5 g / 10 min, for example, greater than about 9 g / 10 min, for example, greater than about 10 g / 10 min, for example, greater than about 12 g / 10 min, when measured according to ISO Test 1133 at 190°C and under a 2.16 kg load. The melt flow index is typically less than about 40 g / 10 min, for example, less than about 35 g / 10 min, for example, less than about 30 g / 10 min. In one embodiment, the melt flow index is about 9 g / 10 min to about 27 g / 10 min.

[0014] As noted above, the polyformal polymer is combined with an acid neutralizer and a plasticizer. The acid neutralizer can comprise an oxide, a sulfide, or a carbonate. For example, the oxide can comprise a metal oxide such as zinc oxide or magnesium oxide. Similarly, the sulfide can comprise a metal sulfide such as zinc sulfide or magnesium sulfide. The carbonate can comprise calcium carbonate. The acid neutralizer can be present in the composition in an amount less than about 2 wt.%, for example, in an amount less than about 1.5 wt.%, for example, in an amount less than about 1.2 wt.%.

[0015] While the acid neutralizer can protect the polymer composition upon exposure to diesel and acidic components that can be formed from diesel, the acid neutralizer can make the composition more brittle, especially after exposure to highly acidic solutions. In this regard, the acid neutralizer is combined with a plasticizer. For example, the plasticizer can comprise a polyalkylene glycol. For example, the polyalkylene glycol can have an average molecular weight greater than about 12000, for example, from about 25000 to about 55000. The plasticizer and the acid neutralizer are present in the polymer composition in a weight ratio of about 3: 1 to about 20: 1, for example, from about 3.5: 1 to about 6: 1, for example, from about 3.5: 1 to about 5.5: 1. In one embodiment, the plasticizer comprises polyethylene glycol.

[0016] In other embodiments, the plasticizer can comprise an aromatic ester (including aromatic polyesters), an aliphatic diester, an epoxide, a sulfonamide, a polyether, a polybutene, a polyamide, an acetylated monoglyceride, an alkyl citrate, or an organic phosphate ester.

[0017] The plasticizer can be present in the composition in an amount greater than about 3 wt.%, for example, in an amount greater than about 3.5 wt.%, for example, in an amount greater than about 3.8 wt.%. The plasticizer is typically present in an amount less than about 8 wt.%, for example, in an amount less than about 6 wt.%.

[0018] Various other components can be present in the polymer composition to provide various benefits and advantages. Generally, each of the other ingredients and components can be contained in the composition in an amount from about 0.1 wt.% to about 10 wt.%, for example, from about 0.1 wt.% to about 1 wt.%.

[0019] For example, in one embodiment, the polymer composition contains a copolyamide. The copolyamide can be present alone or in combination with ethylene bis(stearamide).

[0020] In one embodiment, a neutralizing agent can be present in the composition. The neutralizing agent can comprise tricalcium citrate or calcium carbonate.

[0021] Another ingredient that can be present in the composition is a nucleating agent. For example, the nucleating agent can comprise a polyformal terpolymer.

[0022] As noted above, the polymer composition is particularly suitable for producing molded articles that are to contact fuel oil, such as diesel fuel. The polymer composition is also resistant to highly acidic solutions. For example, in one embodiment, the polymer composition can be used to produce exterior vehicle parts. For example, the molded article can comprise a portion of a fuel system of a car or truck. For example, in one embodiment, the molded article can comprise a fuel contact element. The fuel contact element can comprise a fuel line or a fuel flange.

[0023] Other features and aspects of the present disclosure are discussed in greater detail below. BRIEF DESCRIPTION OF DRAWINGS

[0024] A complete and thorough disclosure of the present disclosure is set forth more particularly in the remainder of the specification, including reference to the accompanying drawings, in which:

[0025] Figure 1 is a side view of one embodiment of a fuel line manufactured according to the present disclosure;

[0026] Figure 2 is a perspective view of one embodiment of a fuel flange manufactured according to the present disclosure; and

[0027] Figure 3 is a graphical representation of the results obtained in the following examples.

[0028] Reference numerals that are repeated in the description and drawings of the present application serve to indicate identical or similar features or elements throughout the application.

[0029] DETAILED DESCRIPTION

[0030] Reference will now be made in detail to embodiments of the application, one or more embodiments of which are illustrated in the drawings. Each embodiment is provided by way of explanation of the application, not limitation of the application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the scope or spirit of the application. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present application cover such modifications and variations.

[0031] Generally, this disclosure relates to a polyoxymethylene polymer composition and polymer articles made from the composition. The polymer composition contains a polyoxymethylene polymer and has improved fuel resistance, particularly diesel fuel resistance. Furthermore, the polymer composition of this disclosure is specifically formulated to be resistant to highly acidic solutions. In particular, the polymer composition of this disclosure is resistant to highly acidic cleaning agents that can come into contact with the fuel systems of cars or trucks. These highly acidic solutions may, for example, contain wheel cleaners, rim cleaners, chrome cleaners, etc. In the past, polyoxymethylene polymer compositions have been formulated to be resistant to diesel fuel. However, such formulations are easily damaged or degraded when they come into contact with wheel or rim cleaning solutions (which inadvertently come into contact with parts or articles constituting the fuel system). To produce a polymer composition that is not only resistant to fuel but also resistant to highly acidic liquids, the composition contains a polyoxymethylene polymer combined with an acid neutralizer and a plasticizer in a specific weight ratio, which has been found to provide unexpectedly and significantly better acid resistance. In one embodiment, the acid neutralizer may comprise a metal oxide, and the plasticizer may comprise a polyalkylene glycol with an average molecular weight greater than about 8,000.

[0032] Typically, any suitable polyoxymethylene polymer can be incorporated into this polymer composition.

[0033] The preparation of this polyoxymethylene polymer can be achieved by polymerizing polyoxymethylene monomers, such as trioxymethylene monomers, in the presence of a molecular weight regulator (e.g., diol). Alkane or trialkyl The mixture is made from alkyl groups and cyclic acetals (such as dioxolane). The polyoxymethylene polymer used in this polymer composition may comprise homopolymers or copolymers. 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%, and for example even at least 97 mol% of -CH2O- repeating units.

[0034] In one embodiment, a polyoxymethylene copolymer is used. The copolymer may contain about 0.1 mol% to about 20 mol% and particularly about 0.5 mol% to about 10 mol% repeating units comprising a saturated or olefinically unsaturated alkylene group or a cycloalkylene group having at least two carbon atoms in the chain, having a sulfur or oxygen atom in the chain, and may include one or more substituents selected from alkyl, cycloalkyl, aryl, aralkyl, heteroaryl, halogen, or alkoxy. In one embodiment, a cyclic ether or cyclic acetal that can be introduced into the copolymer via a ring-opening reaction is used.

[0035] Preferred cyclic ethers or cyclic acetals are those of the following formula:

[0036]

[0037] wherein x is 0 or 1 and R 2 is C2-C4alkylene, which, if appropriate, has one or more substituents, which are C1-C4alkyl, or C1-C4alkoxy, and / or are halogen atoms, preferably chlorine atoms. By way of example only, mention can be made of ethylene oxide, 1,2- propylene oxide, 1,2- and 1,3-butylene oxide, 1,3-dioxolane and 1,3-dioxepane as cyclic ethers, and also linear oligomeric or polymeric formaldehydes such as polydioxolane or polydioxepane as comonomers. It is particularly advantageous to use copolymers which comprise 99.5 to 95 mol% of trioxane and 0.5 to 5 mol%, for example 0.5 to 4 mol%, of one of the abovementioned comonomers. alkylene, which, if appropriate, has one or more substituents, which are C1-C4alkyl, or C1-C4alkoxy, and / or are halogen atoms, preferably chlorine atoms. By way of example only, mention can be made of ethylene oxide, 1,2- propylene oxide, 1,2- and 1,3-butylene oxide, 1,3-dioxolane and 1,3-dioxepane as cyclic ethers, and also linear oligomeric or polymeric formaldehydes such as polydioxolane or polydioxepane as comonomers. It is particularly advantageous to use copolymers which comprise 99.5 to 95 mol% of trioxane and 0.5 to 5 mol%, for example 0.5 to 4 mol%, of one of the abovementioned comonomers. alkylene, which, if appropriate, has one or more substituents, which are C1-C4alkyl, or C1-C4alkoxy, and / or are halogen atoms, preferably chlorine atoms. By way of example only, mention can be made of ethylene oxide, 1,2- propylene oxide, 1,2- and 1,3-butylene oxide, 1,3-dioxolane and 1,3-dioxepane as cyclic ethers, and also linear oligomeric or polymeric formaldehydes such as polydioxolane or polydioxepane as comonomers. It is particularly advantageous to use copolymers which comprise 99.5 to 95 mol% of trioxane and 0.5 to 5 mol%, for example 0.5 to 4 mol%, of one of the abovementioned comonomers.

[0038] The polymerization can be carried out in a precipitation polymerization or in the melt. By suitably selecting the polymerization parameters, such as the duration of the polymerization or the amount of molecular weight regulator, the molecular weight and thus the MVR value of the polymer formed can be adjusted.

[0039] In one embodiment, the polyformal polymer for use in the polymer composition can contain a relatively high amount of reactive groups or functional groups in end positions. For example, the reactive groups can include -OH or -NH2 groups.

[0040] In one embodiment, the polyformal polymer can optionally have end hydroxyl groups, such as hydroxyethylidene groups, and / or pendant hydroxyl groups in at least greater than about 50% of all end positions on the polymer. For example, the polyformal polymer can have at least about 70%, for example at least about 80%, for example at least about 85%, of its end groups being hydroxyl groups, based on the total number of end groups present. It will be understood that the total number of end groups present includes all pendant end groups.

[0041] In one embodiment, the polyformal polymer optionally has an end hydroxyl content of at least 15 mmol / kg, for example at least 18 mmol / kg, for example at least 20 mmol / kg. In one embodiment, the end hydroxyl content is 18-50 mmol / kg. In an alternative embodiment, the polyformal polymer can contain end hydroxyl groups in an amount of less than 100 mmol / kg, for example less than 50 mmol / kg, for example less than 20 mmol / kg, for example less than 18 mmol / kg, for example less than 15 mmol / kg. For example, the polyformal polymer can contain end hydroxyl groups in an amount of about 5 mmol / kg to about 20 mmol / kg, for example about 5 mmol / kg to about 15 mmol / kg. For example, a polyformal polymer having a lower end hydroxyl content but a higher melt volume flow rate can be used.

[0042] In addition to or instead of terminal hydroxyl groups, the polyformal polymer can also have other end groups that are typically used for these polymers. Examples of them are alkoxy, formate, acetate, or aldehyde groups. According to one embodiment, the polyformal is a homopolymer or copolymer comprising at least 50 mol%, for example at least 75 mol%, for example at least 90 mol%, and for example even at least 95 mol% of -CH20- repeat units.

[0043] In one embodiment, the polyformal polymer can be produced using a cationic polymerization process followed by solution hydrolysis to remove any unstable end groups. During cationic polymerization, a diol such as ethylene glycol or a formal can be used as a chain terminator. A heteropoly acid, triflic acid, or boron compound can be used as a catalyst.

[0044] The polyformal polymer can have any suitable molecular weight. For example, the molecular weight of the polymer can be from about 4000 g / mol to about 20000 g / mol. However, in other embodiments, the molecular weight can be much higher than 20000 g / mol, for example from about 20000 g / mol to about 100000 g / mol.

[0045] The polyformal polymer present in the composition can generally have a melt flow index (MFI) of from about 1 g / 10 min to about 50 g / 10 min, for example from about 9 g / 10 min to about 27 g / 10 min, measured according to ISO Test 1133 at 190°C and 2.16 kg, although polyformals having higher or lower melt flow indices are also contemplated herein. In one embodiment, the polyformal polymer has a melt flow index that is generally greater than about 10 g / 10 min. For example, the polyformal polymer can have a melt flow index that is greater than about 11 g / 10 min, greater than about 12 g / 10 min. The melt flow index of the polyformal polymer can be less than about 35 g / 10 min, for example less than about 30 g / 10 min, for example less than about 25 g / 10 min, for example less than about 20 g / 10 min, for example less than about 14 g / 10 min.

[0046] A suitable commercially available polyformal polymer is available under the trademark (HF) from Celanese / Ticona.

[0047] The polyoxymethylene polymer may be present in the polyoxymethylene polymer composition in an amount of at least 60 wt%, for example at least 70 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%. Typically, 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.

[0048] According to this disclosure, the polyoxymethylene polymer is combined with an acid neutralizer and a plasticizer in a ratio that has been found to unexpectedly and significantly improve the polymer composition's and molded articles made therefrom's resistance to highly acidic solutions. The acid neutralizer typically comprises a metal compound and / or oxide, sulfide, or carbonate. Metal oxides that can be used as acid neutralizers include, for example, magnesium oxide and / or zinc oxide. Sulfides that can be used include zinc sulfide, magnesium sulfide, silver sulfide, or molybdenum disulfide. In some instances, the neutralizer comprises calcium carbonate.

[0049] For example, in one embodiment, the acid neutralizer comprises zinc oxide. Zinc oxide may be present in the polymer composition in particulate form (such as precipitated particles).

[0050] In one embodiment, the zinc oxide particles have a combination of a relatively small particle size range and a high surface area. For example, precipitated zinc oxide particles can have a significantly higher surface area than zinc oxide produced by other methods. For example, the acid neutralizer of this disclosure can have a surface area greater than about 25 μm. 2 / g, for example, greater than approximately 30m 2 / g, for example, greater than approximately 35m 2 / g, for example, greater than approximately 40m 2 / g, for example, greater than approximately 45m 2 / g, for example, greater than approximately 50m 2 / g, for example, greater than approximately 55m 2 / g of BET surface area. The BET surface area is typically less than approximately 100m². 2 / g. Using zinc oxide or other acid neutralizers with a relatively high surface area allows the material to be present in a minimal amount. Minimizing the amount of zinc oxide relative to the plasticizer can improve the polymer composition's resistance to wheel cleaner solutions.

[0051] Generally, the acid neutralizer is present in the polymer composition in an amount less than about 10 wt.%, for example, less than about 5 wt.%, for example, in an amount less than about 4 wt.%, for example, in an amount less than about 3 wt.%, for example, in an amount less than about 2 wt.%. Minimizing the amount of acid neutralizer present in the composition can be desirable in certain applications. In this regard, in one embodiment, the acid neutralizer or zinc oxide can be present in the composition in an amount less than about 1.5 wt.%, for example, in an amount less than about 1.2 wt.%, for example, even in an amount less than about 1.1 wt.%. The acid neutralizer is generally present in an amount greater than about 0.1 wt.%, for example, in an amount greater than about 0.5 wt.%, for example, in an amount greater than about 0.7 wt.%.

[0052] In addition to the polyformal polymer and acid neutralizer, the polymer composition further contains a plasticizer. The plasticizer can include a polyalkylene glycol, an ester, a polyester, an epoxide, a sulfonamide, a polyether, a polyamide, a polybutene, an acetylated monoglyceride, an alkyl citrate, an organophosphate, or a mixture thereof.

[0053] For example, in one embodiment, the plasticizer includes a polyethylene glycol having a relatively high molecular weight. For example, the average molecular weight of the plasticizer can generally be greater than about 8000, for example, greater than about 15000, for example, greater than about 20000, for example, greater than about 25000, for example, greater than about 30000, for example, greater than about 35000. The average molecular weight of the plasticizer is generally less than about 55000, for example, less than about 50000, for example, less than about 45000, for example, less than about 40000.

[0054] In an alternative embodiment, the plasticizer can have ester functionality and can include a phthalate, an adipate, a sebacate, a maleate, a trimellitate, a benzoate, or a mixture thereof. Examples of suitable phthalates are diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), diisohexyl phthalate (DIHP), L79 phthalate, L711 phthalate, dioctyl phthalate, diisooctyl phthalate, dinonyl phthalate, diisononyl phthalate, diisodecyl phthalate, L911 phthalate, diundecyl phthalate, diisoundecyl phthalate, undecyl dodecyl phthalate, diisotridecyl phthalate (DTDP), and butyl benzyl phthalate (BBP).

[0055] Examples of adipates are dioctyl adipate, diisononyl adipate, and diisodecyl adipate. An example of a trimellitate is trioctyl trimellitate. Phosphate esters can also be used. Suitable examples are tris(2-ethylhexyl) phosphate, 2-ethylhexyl diphenyl phosphate, and tricresyl phosphate.

[0056] Decanedioates and azelates include di(2-ethylhexyl)sebacate (DOS) and di(2- ethylhexyl)azelate (DOZ).

[0057] Polyester plasticizers are typically based on the condensation products of propylene or butylene glycol with adipic acid or phthalic anhydride. The growing polymer chain of these polyesters can then be capped with an alcohol or a monobasic acid, although non-capped polyesters can be produced by strict control of the reaction stoichiometry.

[0058] Further plasticizers are benzoic acid esters, which are commercially available as MB 10, 2088, LA-705 and 9-88. Epoxide-based plasticizers include epoxidized vegetable oils.

[0059] In one embodiment, the plasticizer is an aromatic benzenesulfonamide. Preference is given to benzenesulfonamides which are represented by the general formula (I):

[0060]

[0061] in which R 1 denotes a hydrogen atom, a C1-C4alkyl group or a C1-C4alkoxy group, X denotes a linear or branched C2-C 10 alkylene group, or an alkyl group, or a methylene group, or a cycloaliphatic group, or an aryl group, and Y denotes a group H, OH or one of the following formulae:

[0062]

[0063] in which R2denotes a C1-C4alkyl group or an aryl group, which groups are optionally themselves substituted by OH or a C1-C4alkyl group.

[0064] Preferred aromatic benzenesulfonamides of the formula (I) are those in which R1denotes a hydrogen atom or a methyl or methoxy group, X denotes a linear or branched C2-C 10 alkylene group or a phenyl group, Y denotes H, OH or a group -O-CO-R2, R2denotes a methyl or phenyl group, the latter being optionally itself substituted by OH or a methyl group.

[0065] Among the aromatic sulfonamides of the formula (I) mention can be made of the following products indicated as being liquid (L) or solid (S) at room temperature, with the abbreviations already assigned to them:

[0066] N-(2-hydroxyethyl)benzenesulfonamide (L),

[0067] N-(3-hydroxypropyl)benzenesulfonamide (L),

[0068] N-(2-hydroxyethyl)-p-toluenesulfonamide (S),

[0069] N-(4-hydroxyphenyl)benzenesulfonamide (S),

[0070] N-[(2-hydroxy-l-hydroxymethyl-l-methyl)ethyl]benzenesulfonamide (L),

[0071] N-[5-hydroxy-l,5-dimethylhexyl]benzenesulfonamide (S),

[0072] N-(2-acetyloxyethyl)benzenesulfonamide (S),

[0073] N-(5-hydroxypentyl)benzenesulfonamide (L),

[0074] N-[2-(4-hydroxybenzoyloxy)ethyl]benzene-sulfonamide (S),

[0075] N-[2-(4-methylbenzoyloxy)ethyl]benzenesulfonamide (S),

[0076] N-(2-hydroxyethyl)-p-methoxybenzenesulfonamide (S), and

[0077] N-(2-hydroxypropyl)benzenesulfonamide (L).

[0078] A particular plasticizer is a sulfonamide, such as N-(n-butyl)benzenesulfonamide.

[0079] It has been surprisingly discovered that controlling the ratio between the plasticizer and the acid neutralizer has a significant and surprising effect on the ability of the polymer composition to resist highly acidic solutions, such as solutions having a pH of less than about 3, such as less than about 2. For example, the plasticizer can be present relative to the acid neutralizer such that the plasticizer to acid neutralizer weight ratio is about 3: 1 to about 20: 1. The plasticizer and acid neutralizer weight ratio can be, for example, about 3: 1 to about 6: 1, such as about 3.5: 1 to about 5.5: 1, such as about 3.8: 1 to about 5.2: 1.

[0080] As noted above, the actual 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 2 wt%, such as in an amount greater than about 3 wt%, such as in an amount greater than about 3.5 wt%, such as in an amount greater than about 3.8 wt%. The plasticizer is generally present in an amount less than about 12 wt%, such as in an amount less than about 8 wt%, such as in an amount less than about 6 wt%, such as in an amount less than about 5 wt%.

[0081] In addition to the polyoxymethylene polymer, acid neutralizer, and plasticizer, various other components and ingredients can be included in the composition to improve one or more properties. For example, in one embodiment, the composition can contain a conductive filler to enable any article molded from the composition to exhibit electrostatic dissipative (ESD) capability. The conductive filler can include conductive particles, powders, fibers, or combinations thereof. For example, the conductive filler can include metal powders, metal flakes, metal fibers (i.e., stainless steel fibers), carbon powders, carbon fibers, carbon black, carbon nanotubes, or combinations thereof.

[0082] Further, the conductive filler can be present in the polymer composition of the present disclosure in an amount of about 1 wt% to about 30 wt%, for example, in an amount of about 1.5 wt% to about 25 wt%, for example, in an amount of about 2 wt% to about 20 wt%, based on the total weight of the polymer composition.

[0083] In one embodiment, a formaldehyde scavenger such as a nitrogen-containing compound can be present. Among them are primarily heterocyclic compounds which have at least one nitrogen atom as or adjacent to an amino-substituted carbon atom or as a heteroatom adjacent to a carbonyl group, for example pyridine, pyrimidine, pyrazine, pyrrolidine, aminopyridine and compounds derived therefrom. Other particularly advantageous compounds are triamino-1,3,5-triazine (melamine) and derivatives thereof, for example melamine-formaldehyde condensates and methylol melamine. In one embodiment, the formaldehyde scavenger present in the composition comprises melamine. Oligomeric polyamides are in principle also suitable for use as formaldehyde scavengers.

[0084] In one embodiment, the formaldehyde scavenger present comprises a guanamine compound. The guanamine compound can include aliphatic guanamine-based compounds, alicyclic guanamine-based compounds, aromatic guanamine-based compounds, heteroatom-containing guanamine-based compounds, and the like. In one embodiment, the guanamine compound comprises a benzoguanamine.

[0085] The polymer composition can contain a single formaldehyde scavenger or can contain a blend of formaldehyde scavengers. Generally, the formaldehyde scavenger is present in the composition in an amount of at least about 0.01 wt%, for example, in an amount of at least about 0.03 wt%, for example, in an amount of at least about 0.05 wt%. The formaldehyde scavenger is generally present in an amount of less than about 2 wt%, for example, in an amount of less than about 1.5 wt%, for example, in an amount of less than about 1 wt%, for example, in an amount of less than about 0.5 wt%, for example, in an amount of less than about 0.1 wt%.

[0086] In one embodiment, one or more formaldehyde scavengers can be combined with the copolyamide. The copolyamide can also enhance the ability of the composition to reduce formaldehyde emissions.

[0087] The copolyamide can have a softening point typically greater than about 120°C, for example greater than about 130°C, for example greater than about 140°C, for example greater than about 150°C, for example greater than about 160°C, for example greater than about 170°C. The copolyamide can have a softening point less than about 210°C, for example less than about 200°C, for example less than about 190°C, for example less than about 185°C. The copolyamide can have a melt viscosity at 230°C greater than about 7 Pa s, for example greater than about 8 Pa s, for example greater than about 9 Pa s. The melt viscosity is typically less than about 15 Pa s, for example less than about 14 Pa s, for example less than about 13 Pa s. In one embodiment, the copolyamide is soluble in ethanol. In one embodiment, the copolyamide can comprise a polycondensation product of a polymeric fatty acid and an aliphatic diamine. The copolyamide is typically present in the composition in an amount greater than about 0.01 wt%, for example in an amount greater than about 0.03 wt%, for example in an amount greater than about 0.05 wt%. The copolyamide is typically present in an amount less than about 2 wt%, for example in an amount less than about 1.5 wt%, for example in an amount less than about 1 wt%, for example in an amount less than about 0.5 wt%, for example in an amount less than about 0.1 wt%.

[0088] In one embodiment, an acid scavenger can be present. The acid scavenger can comprise, for example, an alkaline earth metal salt. For example, the acid scavenger can comprise a calcium salt such as calcium citrate or calcium carbonate. In one embodiment, the acid scavenger can comprise tricalcium citrate. The acid scavenger can be present in an amount of at least about 0.01 wt%, for example at least about 0.05 wt%, for example at least about 0.09 wt%. In one embodiment, a greater amount of acid scavenger is used, for example when the acid scavenger is a carbonate salt. For example, the acid scavenger can be present in an amount greater than about 2 wt%, for example greater than about 5 wt%, for example greater than about 7 wt%. The acid scavenger is typically present in an amount 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.

[0089] In one embodiment, a nucleating agent can be present. The nucleating agent can increase crystallinity and can comprise a formaldehyde terpolymer. For example, in one particular embodiment, the nucleating agent can comprise butanediol diglycidyl ether, oxirane, and tri terpolymers of alkyls. In one embodiment, the terpolymer nucleating agent can 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 micron, for example, less than about 0.6 micron, for example, less than about 0.4 micron, and typically greater than 0.01 micron. Other nucleating agents that can be used include polyamides, boron nitride, or talc. The polyamide nucleating agent can be PA6 or PA12. The nucleating agent can 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 polymeric composition.

[0090] In one embodiment, an antioxidant such as a sterically hindered phenol can be present. Commercially available examples are pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate], triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 3,3'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionhydrazide], and hexamethylene glycol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The antioxidant can be present in the polymeric 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%, for example, at least about 0.2 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 polymeric composition.

[0091] In one embodiment, a lubricant can be present. The lubricant can comprise a polymeric wax composition. In one embodiment, a fatty acid amide such as ethylene bis(stearamide) can be present. In an alternative embodiment, the lubricant can comprise a polyalkylene glycol having a relatively low molecular weight compared to the plasticizer. For example, the lubricant can comprise a polyethylene glycol having an average molecular weight of about 1000 to about 5000, for example, about 3000 to about 4000. The lubricant can be typically present in the polymeric 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 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 polymeric composition.

[0092] In an embodiment, a colorant can be present. Colorants that can be used include any desired 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 polymeric soluble dyes. In an embodiment, a combination of colorants can be included in the polymer composition. For example, the polymer composition can contain carbon black. In an alternative embodiment, the colorants present in the polymer composition can comprise a combination of titanium dioxide with at least one colored pigment (e.g., yellow pigment and green pigment), and optionally further in combination with carbon black. The colorant can 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%, for example at least about 0.5 wt%, and less than about 5 wt%, for example less than about 2.5 wt%, for example less than about 1 wt%, where the weight is based on the total weight of the respective polymer composition.

[0093] When a colorant is present, one or more light stabilizers can also be included in the composition. In an embodiment, a light stabilizer such as a sterically hindered amine can be present in addition to an ultraviolet light stabilizer. Hindered amine light stabilizers that can be used include N-methylated oligomeric hindered amine compounds. For example, the hindered amine light stabilizer can comprise a high molecular weight hindered amine stabilizer. The light stabilizer, when present, can 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.

[0094] In an embodiment, an ultraviolet light stabilizer can be present. The ultraviolet light stabilizer can comprise a benzophenone, benzotriazole, or benzoate. The UV light absorber, when present, can 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.

[0095] In an embodiment, however, the polymer composition is free of any light stabilizer. For example, the composition can be free of an ultraviolet light stabilizer or a hindered amine light stabilizer.

[0096] The polymer composition can also optionally contain one or more reinforcing agents. For example, the polymer composition can contain reinforcing fibers such as glass fibers, carbon fibers, and the like. Reinforcing fibers can generally be present in an amount of about 2 wt% to about 25 wt%.

[0097] In other embodiments, the polymer composition can contain reinforcing particles having a high aspect ratio. The particles can include, for example, glass flakes, mica, loam, graphite, molybdenum disulfide, and mixtures thereof. The particles can have an aspect ratio greater than about 1.5, for example greater than about 2, for example greater than about 2.5, for example greater than about 3, for example greater than about 3.5, for example greater than about 4, for example greater than about 4.5, for example greater than about 5, and typically less than about 20, for example less than about 15, for example less than about 12. Reinforcing fillers can be present in the composition typically in an amount of about 2 to about 25 weight percent.

[0098] The compositions of the present disclosure can be compounded and shaped into polymeric articles using any technique known in the art. For example, the respective compositions can be intensively mixed to form a substantially homogeneous blend. The blend can be melt kneaded at an elevated temperature, such as above the melting point of the polymers used in the polymer composition but below the degradation temperature. Alternatively, the respective compositions can be melted and mixed together in a conventional single or twin-screw extruder. Preferably, the melt mixing is carried out at a temperature of 100-280°C, for example 120-260°C, for example 140-240°C, or 180-220°C.

[0099] After extrusion, the composition can be shaped into pellets. The pellets can be molded into polymeric articles by techniques known in the art, such as injection molding, thermoforming, blow molding, rotational molding, and the like.

[0100] In one embodiment, the polymer composition can be used to produce polymeric articles designed for use in the automotive field. The polymeric articles may, for example, be designed as exterior vehicle parts. In one embodiment, the molded articles are shaped as fuel contact elements. The fuel contact elements may, for example, be one or more parts included in the fuel system of a vehicle, such as a car or a truck. The fuel contact elements may, for example, be designed for repeated contact with diesel fuel.

[0101] For example, see Figure 1 , which shows a fuel line 100 formed from the polymer composition of the present disclosure. The fuel line 100 may, for example, comprise a corrugated tube in this embodiment.

[0102] In addition to fuel lines, the polymer composition of the present disclosure can be used to produce fuel tanks, parts of fuel pumps, parts of fuel filters, fuel rails, parts of injectors, pressure regulators, and return fuel lines.

[0103] In one embodiment, the polymer composition is used to produce a fuel flange 200, as shown in Figure 2 The fuel flange 200 may, for example, be designed to be placed on a fuel tank and connected to one or more fuel lines. For example, as shown in Figure 2As shown, the fuel flange 200 can include at least one fuel inlet or outlet 202 for feeding fuel into the fuel tank and for dispensing fuel from the fuel tank. The fuel flange 200 can also include electrical terminals 204 for connecting controllers contained within the vehicle to various sensors that can be present in and around the fuel tank.

[0104] The present disclosure can be better understood with reference to the following examples. Examples

[0105] The following examples are provided to further illustrate the present application, and are not intended to limit the scope thereof. Other variations of the application will be apparent to those skilled in the art and will be encompassed by the additional claims.

[0106] Example 1

[0107] In this example, various polymer compositions were formulated and tested for resistance to a highly acidic solution. The highly acidic solution used was a wheel cleaner solution.

[0108] The following polymer compositions were formulated:

[0109]

[0110] The above polymer compositions were molded into test coupons and tested against a wheel cleaner solution. The wheel cleaner solution used was EAGLE ONE Chrome Wheel Cleaner, sold by Eagle One of Draper, Utah. This wheel cleaner has a pH of 1.3 and contains the following acidic ingredients:

[0111] Component CAS No. Concentration Phosphoric acid 7664-38-2 >= 5 to < 10% Sodium 1-octanesulfonate 5324-84-5 >= 1.5 to < 5% Oxalic acid, dihydrate 6153-56-6 >= 1.5 to < 5% Sulfuric acid 7664-93-9 >= 0.5 to < 1 % Hydrofluoric acid 7664-39-3 >= 0.1 to <= 0.9%

[0112] The test was performed by spraying the solution onto a strained molded part. Strain of 2% was achieved by applying a 77.8 mm radius of curvature to a 3 mm thick part. The solution was sprayed four times per day and the part was monitored every hour on the first day, twice daily on days 2-7, and once daily thereafter. The general procedure and guidelines for visual inspection were as follows:

[0113] Procedure

[0114] 1. Each sample was covered in a thin layer of cheesecloth and placed in a bending fixture. The cheesecloth was there to ensure an even coverage on the surface. The cheesecloth was left on the surface during the aging.

[0115] 2. The sample was subjected to 2% strain. (There should not be a large difference between materials at 2% strain).

[0116] 3. Stress samples are sprayed with Eagle One Chrome Wheel Cleaner 4 times per day. Suggested times: 8am, 11am, 2pm, and 5pm.

[0117] 4. Samples should be given one even spray, unless a second spray is needed for even and consistent coverage.

[0118] a. Please measure pH regularly in the first few days to confirm consistent exposure.

[0119] 5. Remove tissue and record evidence of cracking according to the following schedule

[0120] a. Day 1 (1 time / hour until end of day)

[0121] b. Days 2-7 (2 times / day starting and switching end of workday)

[0122] c. Days 8-25 (1 time / day only during workday)

[0123] 6. The process continues for a 25 day period.

[0124] Visual Inspection

[0125] 1. Day 1 - Samples should be checked every hour from 8am to 5pm.

[0126] 2. Days 2-5 - Samples should be checked 3 times daily only during normal workday hours. Suggested times: 8am, 1pm, and 5pm.

[0127] 3. Days 6-25 samples should be checked 1 time daily only during normal workday hours.

[0128] 4. All observations are recorded as follows: O for sample is good, Δ for sample has small surface cracks, X for there is a 12mm long crack, and XX for sample is consistently cracked.

[0129] 5. Photograph files should be taken of any cracks or defects on the surface over the 25 day period.

[0130] Results are shown in Figure 3 .

[0131] As shown, Sample 3 was significantly better than Samples 1 and 2 in the wheel cleaner resistance test. Sample 3 contained a plasticizer to acid neutralizer weight ratio of 4:1.

[0132] Various physical properties were also tested for different polymer compositions. The following results were obtained:

[0133]

[0134]

[0135] Example 2

[0136] Polymer compositions were formulated according to the present disclosure and various physical properties were tested. Sample #4 of the polymer composition contained the following components:

[0137]

[0138] The above polymer compositions were molded into various test coupons and the following results were obtained:

[0139]

[0140]

[0141] These and other alterations and changes to the present application can be practiced by those skilled in the art without departing from the spirit and scope of the application, which is defined by the appended claims. In addition, it should be understood that aspects of the various embodiments can be interchanged either 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 application as further described in such appended claims.

Claims

1. A polymer composition comprising: A polyoxymethylene polymer, present in the polymer composition in an amount of at least about 60% by weight, the polyoxymethylene polymer comprising a polyoxymethylene copolymer in a comonomer content of 0.5 mol% to 4 mol%; An acid neutralizing agent comprising magnesium oxide, wherein the acid neutralizing agent has a concentration greater than about 55m 2 / g BET surface area, and the acid neutralizer is present in the polymer composition in an amount greater than about 5% by weight and less than about 10% by weight; A plasticizer comprising polyethylene glycol, wherein the plasticizer is present in the polymer composition in an amount of less than 12% by weight; Deacids containing calcium salts; and Ethylenebis(stearamide).

2. The polymer composition as defined in claim 1, wherein the acid neutralizer is magnesium oxide.

3. The polymer composition as defined in claim 1, wherein the comonomer comprises 1,3-dioxolane.

4. The polymer composition as defined in any of the preceding claims, wherein the polyoxymethylene polymer has a terminal hydroxyl content of about 5 mmol / kg to about 20 mmol / kg.

5. The polymer composition as defined in claim 4, wherein the polyoxymethylene polymer further comprises end groups consisting of alkoxy groups.

6. The polymer composition as defined in any of the preceding claims, wherein the polyoxymethylene polymer is present in the polymer composition in an amount greater than about 80% by weight.

7. The polymer composition as defined in any of the preceding claims, wherein the polyoxymethylene polymer has a melt flow index greater than 5 g / 10 min and less than 30 g / 10 min.

8. The polymer composition as defined in any of the preceding claims, wherein the polyoxymethylene polymer has a melt flow index of 9 g / 10 min to 27 g / 10 min.

9. The polymer composition as defined in any of the preceding claims, wherein the average molecular weight of the polyethylene glycol is less than 40,000 g / mol.

10. The polymer composition as defined in any of the preceding claims, wherein the composition further comprises a sterically hindered phenol.

11. The polymer composition as defined in claim 10, wherein the sterically hindered phenol comprises pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

12. The polymer composition as defined in any of the preceding claims, wherein the polymer composition further comprises a reinforcing agent comprising reinforcing fibers, glass flakes, mica, or mixtures thereof.

13. The polymer composition as defined in claim 1, wherein the comonomer comprises 1,3-dioxolane, and the plasticizer is present in the polymer composition in an amount greater than 2% by weight, wherein the polyoxymethylene polymer has a melt flow index greater than 5 g / 10 min and less than 30 g / 10 min, and wherein the composition further comprises a sterically hindered phenol.

14. The polymer composition as defined in claim 1, wherein the comonomer comprises 1,3-dioxolane, the polyoxymethylene polymer has a terminal hydroxyl content of about 5 mmol / kg to about 20 mmol / kg, the polyoxymethylene polymer further comprises end groups consisting of alkoxy groups, the plasticizer is present in the polymer composition in an amount greater than 2% by weight, the polyoxymethylene polymer has a melt flow index greater than 5 g / 10 min and less than 30 g / 10 min, and the composition further comprises a sterically hindered phenol.

15. The polymer composition as defined in any of the preceding claims, wherein the composition further comprises at least one member selected from nucleating agents or lubricants.

16. The polymer composition as defined in claim 15, wherein the composition further comprises a nucleating agent comprising a polyoxymethylene terpolymer.

17. A molded article made of a polymer composition as defined in any one of the preceding claims, the molded article comprising an external vehicle part.

18. The molded article as defined in claim 17, wherein the external vehicle part comprises a fuel contact element.

19. The molded article as defined in claim 17, wherein the molded article comprises a fuel line.

20. The molded article as defined in claim 17, wherein the molded article comprises a fuel flange.

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