Low emission polyoxymethylene compositions with color stability

Abstract

A polyoxymethylene polymer composition comprising a formaldehyde stabilizer package is disclosed. In one embodiment, the formaldehyde stabilizer package comprises a substituted hydantoin, it has been found that the substituted hydantoin alone or a combination of a substituted hydantoin and another emission control agent can significantly reduce formaldehyde emissions.

Description

[0001] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 412,592, filed on October 3, 2022, which is incorporated herein by reference in its entirety. Background of the Invention

[0003] Polyacetal polymers (commonly known as polyoxymethylene) have been recognized as extremely useful engineering materials in various applications. For example, polyacetal polymers are widely used in the construction of molded parts, such as parts for the automotive and electrical industries. For example, polyacetal polymers have excellent mechanical properties, fatigue resistance, wear resistance, chemical resistance, and moldability.

[0004] Although polyacetal resins have many useful properties, the polymers tend to degrade when heated and are inherently unstable in an oxidizing atmosphere or in an acidic or alkaline environment. In particular, polyacetal resins have a tendency to emit formaldehyde during processing and after the polymer is molded into parts. Formaldehyde is not only a pollutant but can also have an adverse effect on metal components that may be placed in contact with the polymer. For example, formaldehyde is easily oxidized to formic acid, which can corrode metals or cause discoloration.

[0005] In view of the above, in order to reduce formaldehyde emissions, those skilled in the art have attempted to combine polyacetal polymers with various compounds. For example, in the past, polyacetal polymers have been combined with melamine in order to achieve lower formaldehyde emission performance. Additionally, various other chemical compounds have been proposed for reducing formaldehyde emissions.

[0006] Although the various chemical compounds used in the past have successfully reduced the formaldehyde emissions of products made from polyoxymethylene polymers, there is still a need for further improvement in formaldehyde emissions. For example, more stringent government regulations continue to require further improvement in reducing formaldehyde emissions.

[0007] However, unfortunately, when an additive is combined with a polyacetal polymer to enhance one property, the additive may have an adverse effect on another property. For example, adding a greater amount of a formaldehyde scavenger to a polyoxymethylene polymer composition may impair one or more properties of the polymer. For example, an excessive amount of a formaldehyde scavenger may cause the molded article to discolor during use and / or begin to adversely affect other physical properties.

[0008] In view of the above, there is a need for an improved formaldehyde stabilizer package that can further reduce formaldehyde emissions without adversely affecting other properties of the polyoxymethylene polymer composition. Summary of the Invention

[0010] Generally, the present disclosure relates to a polymer composition mainly comprising a polyacetal resin and a molded product made from the composition. The polymer composition of the present disclosure is particularly formulated to exhibit ultra-low formaldehyde emissions. For example, a polyoxymethylene polymer composition formulated according to the present disclosure can exhibit formaldehyde emissions of less than about 2 ppm, such as less than about 1 ppm, when tested according to the VDA 275 test. The VDA 275 test (German Automotive Industry Recommendation No. 275) was documented by Kraftfahrwesen e.V. in July 1994.

[0011] In one embodiment, for example, the polymer composition of the present disclosure comprises a combination of a polyoxymethylene polymer and a formaldehyde stabilizer package for reducing formaldehyde emissions. In one embodiment, the formaldehyde stabilizer package can comprise at least one emission control agent. In particular, certain substituted hydantoins have been found to be very effective in reducing formaldehyde emissions. The substituted hydantoins can be used alone or in combination with other hydrazides and / or other emission control agents. In one embodiment, the polymer composition is formulated to comprise a substituted hydantoin without any significant adverse effect on other properties of the molded article made from the composition. For example, in one embodiment, a molded article prepared according to the present disclosure exhibits very stable color quality, making the polymer composition very suitable for producing automotive interior trim parts and the like.

[0012] In one embodiment, for example, the present disclosure relates to a polyoxymethylene polymer in combination with a formaldehyde stabilizer package comprising a substituted hydantoin alone, or comprising a combination of a substituted hydantoin and one or more aliphatic carboxylic acid hydrazides. When the substituted hydantoin is present in combination with an aliphatic carboxylic acid hydrazide, the weight ratio between the aliphatic carboxylic acid hydrazide and the substituted hydantoin can be from about 1:1.1 to about 1:8.5, such as from about 1:1.5 to about 1:7.5, such as from about 1:2 to about 1:5.5.

[0013] The substituted hydantoin can be present in the polymer composition in an amount less than about 0.6 wt.%, such as less than about 0.5 wt.%, such as less than about 0.4 wt.%, such as less than about 0.35 wt.%, such as less than about 0.3 wt.%, and generally in an amount greater than about 0.01 wt.%, such as greater than about 0.05 wt.%, such as greater than about 0.07 wt.%, such as greater than about 0.09 wt.%, such as greater than about 0.1 wt.%, such as greater than about 0.12 wt.%, such as greater than about 0.15 wt.%, such as greater than about 0.17 wt.%, such as greater than about 0.2 wt.%. The substituted hydantoin can comprise two hydrazinocarbonylalkyl groups. The substituted hydantoin can have a melting point less than about 150 °C, such as less than about 140 °C, such as less than about 130 °C, such as less than about 125 °C, and generally greater than about 100 °C. The substituted hydantoin can have a relatively low curing temperature less than about 125 °C, such as less than about 120 °C, such as less than about 115 °C, and generally greater than about 100 °C, such as greater than about 105 °C. In one specific embodiment, the substituted hydantoin comprises 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionylhydrazide).

[0014] As described above, the substituted hydantoin can be combined with an aliphatic carboxylic acid hydrazide. The aliphatic carboxylic acid hydrazide can be a dihydrazide. Examples of the dihydrazide include sebacic dihydrazide, dodecanedioic dihydrazide, or a mixture thereof. Due to the presence of the substituted hydantoin, the aliphatic carboxy dihydrazide (when present) can be present in the polymer composition in a relatively small amount. For example, the aliphatic carboxylic acid hydrazide can be present in the polymer composition in an amount less than the amount of the above-mentioned substituted hydantoin and less than about 0.15 wt.%, such as less than about 0.1 wt.%.

[0015] The formaldehyde stabilizer package can further comprise an acid scavenger. The acid scavenger can include a metal salt of an organic acid. In one specific embodiment, the acid scavenger is an organic acid having a carbon chain length of 8 carbon atoms or less. For example, in one aspect, the acid scavenger comprises tricalcium citrate. The acid scavenger can be present in the polymer composition in an amount less than about 0.5 wt.%, such as less than about 0.2 wt.%, such as less than about 0.08 wt.%, and in an amount greater than about 0.001 wt.%.

[0016] Other optional components that can be included in the polymer composition include a nucleating agent in an amount of about 0.05 wt.% to about 1 wt.%, a phenolic antioxidant in an amount of about 0.05 wt.% to about 2 wt.%, and a lubricant in an amount of about 0.05 wt.% to about 1.5 wt.%. The polymer composition can also optionally comprise a thermoplastic elastomer, reinforcing fibers, and / or a UV stabilizer.

[0017] The polymer composition and the molded article made from the composition can exhibit excellent physical and mechanical properties. For example, when tested at a molding temperature of 205 °C according to DIN 6167, the polymer composition can exhibit a yellowness index of less than 0, such as less than about -1, such as less than about -2, such as less than about -3, and greater than about -10. The polymer composition can also exhibit an L value of less than about 80, such as less than about 78, such as less than about 76, and greater than about 60, such as greater than about 70 at a molding temperature of 205 °C. * value.

[0018] The polymer composition can also be tested for formaldehyde emissions according to the 10-Liter Bag Test. The polymer composition made according to the present disclosure, when tested, for example, according to the 10-Liter Bag Test, can exhibit formaldehyde emissions of less than about 100 µg / m 3 , such as less than about 80 µg / m 3 , such as less than about 60 µg / m 3 , such as less than about 55 µg / m 3 .

[0019] All different types of molded articles can be made from the polymer composition containing the formaldehyde stabilizer package according to the present disclosure. For example, the molded article can include automotive interior parts. The molded article can include latches, levers, gears, pivot housings, speaker grilles, door handles, decorative trim, brackets, seat rails, etc. Medical products can also be made from the polymer composition, such as components of inhalers or syringes.

[0020] Other features and aspects of the present disclosure are discussed in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the remainder of the specification, including reference to the accompanying drawings, a complete and enabling disclosure of the present disclosure is set forth in more detail, in which: Figure 1 is a perspective view of the interior of an automobile, showing various molded articles that can be manufactured according to the present disclosure; Figure 2 is a perspective view of a medical inhaler that can be made from a molded part according to the present disclosure; and Figure 3 is a perspective view of a medical syringe containing a molded part manufactured according to the present disclosure.

[0023] In this specification and the drawings, repeated use of reference numerals is intended to represent the same or similar features or elements of the invention. DETAILED DESCRIPTION

[0025] Those of ordinary skill in the art will understand that this discussion is only a description of exemplary embodiments and is not intended to limit the broader aspects of the present disclosure.

[0026] Generally, the present disclosure relates to a polymer composition exhibiting low formaldehyde emissions, which comprises a polyacetal resin, particularly a polyoxymethylene copolymer. The polymer composition is highly suitable for use in a molding process for producing molded articles. The polymer composition may comprise one or more colorants for producing molded articles having any desired color. The molded articles can be used in an infinite variety of different applications and in multiple fields. In one embodiment, for example, the molded article can be manufactured according to the present disclosure and designed to serve as an automotive part, such as an automotive part designed for use inside a vehicle (e.g., a sedan and a truck).

[0027] More particularly, the present disclosure relates to a polymer composition comprising a combination of a polyacetal resin and a formaldehyde stabilizer package. The formaldehyde stabilizer package comprises at least one emission control agent. In particular, it has been found that substituted hydantoins having specific properties are very effective emission control agents either alone or in combination with other hydrazides. For example, it has been found that the substituted hydantoins of the present disclosure significantly reduce the formaldehyde emissions of polyoxymethylene polymer compositions without adversely interfering with other properties of the polymer composition or the molded articles made from the composition. For example, it has been found that the substituted hydantoins greatly reduce formaldehyde emissions while also producing a polymer composition having excellent color retention and stability properties.

[0028] In one aspect, the substituted hydantoin comprises two hydrazinocarbonylalkyl groups. In one aspect, the specific substituted hydantoin for incorporation into the polymer composition can have a relatively low melting point and a relatively low curing temperature. For example, the melting point of the substituted hydantoin can be less than about 150 °C, such as less than about 140 °C, such as less than about 130 °C, such as less than about 125 °C, such as less than about 122 °C. The melting point can be greater than about 100 °C, such as greater than about 110 °C, such as greater than about 115 °C, such as greater than about 118 °C. The substituted hydantoin can be configured to cure (after one hour of exposure to the above temperature) at a temperature of less than about 125 °C, such as less than about 120 °C, such as less than about 115 °C, such as less than about 112 °C, and generally greater than about 100 °C, such as greater than about 105 °C.

[0029] In one specific embodiment, the substituted hydantoin may include 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionylhydrazide).

[0030] In the past, it has been proposed to use hydantoin compounds having two hydrazinocarbonylalkyl groups in polyacetal resin compositions to reduce the generation of formaldehyde in molded articles. For example, U.S. Patent Publication No. 2021 / 0355314, which is incorporated herein by reference, relates to a polyacetal resin composition. However, in the '314 application, the examples generally teach very low amounts of hydantoin compounds and teach that the hydantoin compounds alone produce adverse results. In contrast, we have found that a selected amount of substituted hydantoin alone can be very effective in reducing formaldehyde emissions without any adverse consequences. In addition, we have found that using a combination of a substituted hydantoin compound and other acylhydrazine compounds in a specific weight ratio can be very effective in reducing formaldehyde emissions while maintaining the mechanical and aesthetic properties of the polymer composition and the molded articles made from the composition.

[0031] In one embodiment, for example, the formaldehyde stabilizer package of the present disclosure can comprise a combination of a substituted hydantoin emission control agent and one or more aliphatic carboxylic acid acylhydrazines. The aliphatic carboxylic acid acylhydrazine can be a diacylhydrazine. For example, specific examples of the diacylhydrazine include sebacic diacylhydrazine, dodecanedioic diacylhydrazine, or a mixture thereof.

[0032] In one embodiment, the formaldehyde stabilizer package of the present disclosure comprises an amount of substituted hydantoin that is the same as or greater than the amount of aliphatic carboxylic acid acylhydrazine present in the formulation. In one aspect, for example, the one or more aliphatic carboxylic acid acylhydrazines are present in a weight ratio of about 1:1.1 to about 1:8.5, such as about 1:1.5 to about 1:7.5, such as about 1:2 to about 1:5.5, relative to the substituted hydantoin. Although the weight ratio can vary depending on the specific application, it has been found that the above weight ratios are particularly effective in reducing formaldehyde emissions while producing molded articles with enhanced color stability, making the molded articles particularly suitable for the production of decorative parts for the interior of vehicles (such as automobiles), or for the production of home appliance parts.

[0033] The one or more aliphatic carboxylic acid acylhydrazines can generally be present in the polymer composition in an amount of about 0.001 wt.% to about 1 wt.% (including all 0.1 wt.% increments therebetween). However, when combined with a substituted hydantoin, the amount of aliphatic carboxylic acid acylhydrazine present in the polymer composition can be minimized. For example, in one embodiment, the one or more aliphatic carboxylic acid acylhydrazines are present in the polymer composition in an amount less than 0.2 wt.%, such as in an amount less than about 0.15 wt.%, such as in an amount less than about 0.12 wt.%, such as in an amount less than about 0.1 wt.%, such as less than about 0.09 wt.%, such as less than about 0.08 wt.%. Minimizing the amount of aliphatic carboxylic acid acylhydrazine present in the composition can provide various advantages and benefits, including minimizing free acylhydrazine in the composition and providing color stability.

[0034] The amount of the substituted hydantoin present in the polymer composition can vary depending on whether the substituted hydantoin is present alone in the composition or in combination with other emission control agents. Generally, the substituted hydantoin can be present in the polymer composition in an amount from about 0.0001 wt% to about 1 wt% (including all 0.01 wt% increments therebetween). In one embodiment, the substituted hydantoin is present in the polymer composition in an amount greater than any other emission control agent present in the composition. For example, the substituted hydantoin can be present in an amount greater than 0.07 wt.%, such as in an amount greater than about 0.09 wt.%, such as in an amount greater than about 0.1 wt.%, such as in an amount greater than about 0.12 wt.%, such as in an amount greater than about 0.15 wt.%, such as greater than about 0.17 wt.%, such as greater than about 0.2 wt.%, such as greater than about 0.22 wt.%, such as greater than about 0.24 wt.% in the polymer composition. In various embodiments, the substituted hydantoin can be present in an amount less than about 0.8 wt.%, such as in an amount less than about 0.6 wt.%, such as in an amount less than about 0.55 wt.%, such as in an amount less than about 0.5 wt.%, such as in an amount less than about 0.45 wt.%, such as less than about 0.4 wt%, such as less than about 0.35 wt%, such as less than about 0.3 wt% in the polymer composition.

[0035] In one embodiment, the formaldehyde stabilizer package includes the above emission control agents and does not include other formaldehyde scavengers used in the past. For example, the polymer composition can be formulated to be free of melamine. In fact, the polymer composition can be formulated to be free of any melamine or any melamine derivatives. In one aspect, the polymer composition is free of any guanamine compounds.

[0036] Other emission control agents that can be present in the formaldehyde stabilizer package include amino acids (such as arginine) or alkylene ureas (such as ethylene urea). The additional emission control agents can generally be present in the polymer composition in an amount from about 0.01 wt.% to about 0.5 wt.% (including all 0.01 wt.% increments therebetween).

[0037] The formaldehyde stabilizer package of the present disclosure can also contain an acid scavenger. It is believed that certain acid scavengers are particularly suitable for combination with the substituted hydantoin.

[0038] In one specific embodiment, for example, the acid scavenger can include a metal salt of an organic acid, wherein the organic acid has a carbon chain length of 8 carbon atoms or less. For example, in one specific embodiment, the acid scavenger can include a metal citrate, such as tricalcium citrate.

[0039] In other embodiments, the acid scavenger can include salts of carboxylic acids, such as metal salts of fatty acids. The carboxylate salts can include alkaline earth metal salts of fatty acids. For example, the cation of the salt can include calcium, barium, lithium, sodium, magnesium, zinc, etc.

[0040] The fatty acid can contain a carbon chain length of generally about 3 carbon atoms to about 20 carbon atoms. The fatty acid can include dicarboxylic acids or tricarboxylic acids. Specific examples include metal salts of propionic acid, stearic acid, butyric acid, caproic acid, capric acid, lauric acid, myristic acid, palmitic acid, etc. Specific examples include calcium propionate, calcium 12-hydroxystearate, calcium stearate, and mixtures thereof.

[0041] One or more acid scavengers can generally be present in the polymer composition in an amount of about 0.05 wt.% to about 2 wt.% (including all 0.1 wt.% increments therebetween). In some embodiments, particularly when using tricalcium citrate, a relatively small amount of acid scavenger is required. For example, the acid scavenger can be present in an amount less than 1 wt.%, such as less than about 0.8 wt.%, such as less than about 0.5 wt.%, such as less than about 0.2 wt.%, or even in an amount less than about 0.08 wt.%. One or more acid scavengers are generally present in an amount greater than 0.001 wt.%, such as in an amount greater than about 0.01 wt.%.

[0042] When combined with a polyoxymethylene polymer, the formaldehyde stabilizer package of the present disclosure as described above can produce polymer compositions and molded articles that not only have low formaldehyde emission performance but also have excellent mechanical properties and visual appeal.

[0043] For example, in one embodiment, a polymer composition containing a polyoxymethylene polymer exhibits a formaldehyde emission of less than about 2 ppm (μg / g), such as less than about 1 ppm, such as less than about 0.8 ppm, such as less than about 0.6 ppm, or even less than about 0.4 ppm according to VDA 275. Even when the test specimen has a thickness of 1 mm and is formed at a molding temperature of 205 °C, the above formaldehyde emission characteristics can be obtained. In one aspect, the test can be carried out after the test specimen has been dried at 140 °C for two hours.

[0044] Another formaldehyde emission test is the 10-liter bag test. When tested according to the 10-liter bag test, the polymer composition made according to the present disclosure can show a formaldehyde emission of less than about 100 µg / m 3 , such as less than about 80 µg / m 3 , such as less than about 60 µg / m 3 , such as less than about 55 µg / m 3 . The 10-liter bag test can be carried out on specimens molded at a temperature of 205 °C as well.

[0045] Polymer compositions and molded articles made from such compositions may also exhibit excellent color stability. For example, when tested at a molding temperature of 205 °C according to DIN 6167, the polymer composition may exhibit a yellowness index of less than 0, such as less than about -1, such as less than about -2, such as less than about -3, and generally greater than about -10.

[0046] Polymer compositions may also be tested according to the CIELAB color scale. As used herein, the CIELab color values L * 、a * and b * are measured in a color space defined by the International Commission on Illumination. L * a * b * chromaticity system was established as a standard by the International Commission on Illumination (CIE) in 1976. The CIELab L * value used herein to define the darkness / brightness of the polymer composition is a unit of color measurement in the above CIELab system. Colors can be matched according to CIELab. In L * a * b * chromaticity system, L * refers to the brightness represented by a numerical value.

[0047] For example, when the polymer composition is molded at a temperature of 205 °C, it may exhibit an L * value of less than about 80, such as less than about 78, such as less than about 76, and generally greater than about 60, such as greater than about 70, such as greater than about 72.

[0048] The formaldehyde stabilizer package of the present disclosure is particularly formulated to be combined with polyoxymethylene polymers.

[0049] Generally, any suitable polyoxymethylene polymer can be incorporated into the polymer composition.

[0050] The preparation of polyoxymethylene polymers can be carried out by the polymerization of monomers for forming polyoxymethylene (such as trioxane, or a mixture of trioxane and cyclic acetals such as dioxolane) in the presence of a molecular weight regulator (such as a diol). The polyoxymethylene polymers used in the polymer composition may include homopolymers or copolymers. According to one embodiment, the polyoxymethylene is a homopolymer or copolymer containing at least 50 mol.%, such as at least 75 mol.%, such as at least 90 mol.% and such as even at least 97 mol.% of -CH2O- repeating units.

[0051] In one embodiment, a polyoxymethylene copolymer is used. The copolymer can comprise from about 0.01 mol.% to about 20 mol.%, and in particular from about 0.5 mol.% to about 10 mol.%, of repeating units that include a saturated or ethylenically unsaturated alkylene group having at least 2 carbon atoms, or a cycloalkylene group, which has a sulfur or oxygen atom in the chain and can include one or more substituents selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl, heteroaryl, halogen, and alkoxy. In one embodiment, a cyclic ether or acetal is used, which can be introduced into the copolymer via a ring-opening reaction.

[0052] Preferred cyclic ethers or acetals are those of the following formula: where x is 0 or 1, and R 2 is a C2-C4 alkylene group, which, where appropriate, has one or more substituents, the one or more substituents being a C1-C4 alkyl group, or a C1-C4 alkoxy group, and / or a halogen atom, preferably a chlorine atom. By way of example only, mention may be made of ethylene oxide, 1,2-epoxypropane, 1,2-epoxybutane, 1,3-epoxybutane, 1,3-dioxane, 1,3-dioxolane, and 1,3-dioxepane as cyclic ethers, and linear oligomeric or polyoxymethylenes, such as polydioxolane or polydioxepane, as comonomers. It is particularly advantageous to use a copolymer consisting of from 99.5 mol.% to 95 mol.% of trioxane and from 0.01 mol.% to 5 mol.% (such as from 0.5 mol.% to 4 mol.%) of one of the abovementioned comonomers. In one embodiment, the polyoxymethylene polymer contains a relatively low amount of comonomer. For example, the comonomer can be present in an amount of less than about 2 mol.%, such as less than about 1.5 mol.%, such as less than about 1 mol.%, such as less than about 0.8 mol.%, such as less than about 0.6 mol.%.

[0053] The polymerization can be carried out as precipitation polymerization or in the melt. For example, the polyoxymethylene copolymer can be formed by solution hydrolysis, where a precipitate or powder with a very small amount of unstable end groups is formed. By appropriately selecting polymerization parameters, such as the polymerization time or the amount of molecular weight regulator, the molecular weight of the resulting polymer can be adjusted and thus the MVR value of the resulting polymer can be adjusted.

[0054] In one embodiment, the polyoxymethylene polymer used in the polymer composition can contain a relatively high amount of reactive groups or functional groups at the terminal positions. For example, the reactive groups can include -OH groups or -NH2 groups.

[0055] In one embodiment, the polyoxymethylene polymer may have terminal hydroxyl groups in at least greater than about 50% of all terminal sites on the polymer, such as hydroxyethylene groups and / or hydroxyl side groups. For example, based on the total number of terminal groups present, at least about 70%, such as at least about 80%, such as at least about 85% of the terminal groups of the polyoxymethylene polymer may be hydroxyl groups. It should be understood that the total number of terminal groups present includes all side-chain terminal groups.

[0056] In one embodiment, the polyoxymethylene polymer has a content of terminal hydroxyl groups of at least 15 mmol / kg, such as at least 18 mmol / kg, such as at least 20 mmol / kg. In one embodiment, the terminal hydroxyl group content is from 18 mmol / kg to 50 mmol / kg. In an alternative embodiment, the polyoxymethylene polymer may contain an amount of terminal hydroxyl groups less than 20 mmol / kg, such as less than 18 mmol / kg, such as less than 15 mmol / kg. For example, the polyoxymethylene polymer may contain an amount of terminal hydroxyl groups from about 5 mmol / kg to about 20 mmol / kg, such as from about 5 mmol / kg to about 15 mmol / kg. For example, a polyoxymethylene polymer with a lower terminal hydroxyl group content but a higher melt volume flow rate can be used.

[0057] In addition to or instead of terminal hydroxyl groups, the polyoxymethylene polymer may also have other terminal groups commonly used for these polymers. Examples of them are alkoxy groups, formate groups, acetate groups or aldehyde groups. According to one embodiment, the polyoxymethylene is a homopolymer or copolymer containing at least 50 mol.%, such as at least 75 mol.%, such as at least 90 mol.% and for example even at least 95 mol.% of -CH2O- repeating units.

[0058] In one embodiment, the polyoxymethylene polymer can be produced using a cationic polymerization process followed by solution hydrolysis to remove any unstable end groups. During the cationic polymerization process, a diol (such as ethylene glycol) or methylal can be used as a chain terminator. A heteropolyacid, trifluoromethanesulfonic acid or a boron compound can be used as a catalyst.

[0059] The polyoxymethylene polymer can have any suitable molecular weight. For example, the molecular weight of the polymer can be from about 4,000 g / mol to about 20,000 g / mol. However, in other embodiments, the molecular weight can be much higher than 20,000 g / mol, such as from about 20,000 g / mol to about 100,000 g / mol.

[0060] The polyoxymethylene polymer present in the composition generally may have about 0.1 cm as determined according to ISO 1133 at 190 °C and 2.16 kg3 / 10 min to about 80 cm 3 / 10 min melt flow index (MFI). In one embodiment, the polyoxymethylene polymer can have about 5 cm 3 / 10 min to about 15 cm 3 / 10 min, such as about 8 cm 3 / 10 min to about 12 cm 3 / 10 min melt flow index. In an alternative embodiment, a polyoxymethylene polymer with a relatively high melt flow index can be used. For example, the polyoxymethylene polymer can have about 18 cm 3 / 10 min to about 40 cm 3 / 10 min, such as about 20 cm 3 / 10 min to about 35 cm 3 / 10 min melt flow index.

[0061] Suitable commercially available polyoxymethylene polymers can be obtained under Celanese's trade name Hostaform® (HF).

[0062] The polyoxymethylene polymer can be present in the polyoxymethylene polymer composition in an amount of at least 50 wt.%, such as at least 60 wt.%, such as at least 70 wt%, such as at least 80 wt.%, such as at least 85 wt.%, such as at least 90 wt.%, such as at least 93 wt.%. Generally, the polyoxymethylene polymer is present in an amount of less than about 100 wt.%, such as less than about 99 wt.%, such as less than about 97 wt.%, where the weight is based on the total weight of the polyoxymethylene polymer composition.

[0063] The polymer compositions of the present disclosure can also contain other known additives, such as antioxidants, UV stabilizers or heat stabilizers, impact modifiers, and / or reinforcing fibers. In addition, the composition can contain processing aids, such as tackifiers, lubricants, nucleating agents, mold release agents, fillers, or antistatic agents, and additives that impart the desired properties to the composition and the articles or parts made therefrom.

[0064] In one embodiment, a UV light stabilizer can be present. The UV light stabilizer can include benzophenone, benzotriazole, or benzoate. When present, the UV light absorber can be present in the polymer composition in an amount of at least about 0.01 wt.%, such as at least about 0.05 wt.%, such as at least about 0.075 wt.%, and less than about 1 wt.%, such as less than about 0.75 wt.%, such as less than about 0.5 wt.%, where the weight is based on the total weight of the corresponding polymer composition.

[0065] In one embodiment, a nucleating agent may be present. The nucleating agent may increase crystallinity and may include a formaldehyde terpolymer. In a specific embodiment, for example, the nucleating agent may comprise a terpolymer of butanediol diglycidyl ether, ethylene oxide, and trioxane. The nucleating agent 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.%, and less than about 2 wt.%, such as less than about 1.5 wt.%, such as less than about 1 wt.%, where the weight is based on the total weight of the corresponding polymer composition.

[0066] In one embodiment, an antioxidant may be present, such as a hindered phenol. Exemplary commercially available ones are pentaerythritol tetra[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-(3,5-di-tert-butyl-4-hydroxyphenyl)propionylhydrazide], and hexamethylene glycol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The antioxidant 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.%, such as at least about 0.075 wt.%, and less than about 1 wt.%, such as less than about 0.75 wt.%, such as less than about 0.5 wt.%, where the weight is based on the total weight of the corresponding polymer composition.

[0067] In one embodiment, in addition to ultraviolet light stabilizers, light stabilizers may also be present, such as hindered amines. Hindered amine light stabilizers that may be used include N-methylated oligomeric hindered amine compounds. For example, the hindered amine light stabilizer may include high molecular weight hindered amine stabilizers. Other embodiments of the light stabilizer include 2,2,6,6-tetramethyl-4-piperidyl compounds, such as bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate or a polymer of dimethyl succinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine. In one embodiment, the light stabilizer may include 2-(2H-benzotriazol-2-yl)-4,6-bis(1-ethyl-1-phenyl-ethyl)phenol. The light stabilizer (when present) 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.%, such as at least about 0.075 wt.%, and less than about 1 wt.%, such as less than about 0.75 wt.%, such as less than about 0.5 wt.%, where the weight is based on the total weight of the corresponding polymer composition.

[0068] In one embodiment, a lubricant may be present. The lubricant may include a polymeric wax composition. Additionally, in one embodiment, a polyethylene glycol polymer (processing aid) may be present in the composition. For example, the polyethylene glycol may have a molecular weight of from about 1000 to about 5000, such as from about 3000 to about 4000. In one embodiment, for example, PEG-75 may be present. In another embodiment, a fatty acid amide, such as ethylenebis(stearamide), may be present. The lubricant may generally be present in the polymer composition in an amount of at least about 0.01 wt%, such as at least about 0.05 wt%, such as at least about 0.075 wt.%, and less than about 1 wt%, such as less than about 0.75 wt%, such as less than about 0.5 wt%, where the weight is based on the total weight of the corresponding polymer composition.

[0069] In one embodiment, a colorant may be present. Colorants that may be used include any desired inorganic pigments, such as titanium dioxide, ultramarine, cobalt blue, and other organic pigments and dyes, such as phthalocyanine, anthraquinone, etc. 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 include a combination of titanium dioxide and carbon black. In an alternative embodiment, the colorant present in the polymer composition may include a combination of titanium dioxide and 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.%, such as at least about 0.8 wt.%, such as at least about 1 wt.%, and less than about 5 wt.%, such as less than about 2.5 wt.%, such as less than about 1 wt.%, where the weight is based on the total weight of the corresponding polymer composition.

[0070] Fillers that may be included in the composition include glass beads, wollastonite, loam, molybdenum disulfide or graphite, and / or inorganic or organic fibers.

[0071] Reinforcing fibers that may be included in the composition are mineral fibers (such as glass fibers), polymer fibers (especially organic high-modulus fibers, such as aramid fibers), metal fibers (such as steel fibers), carbon fibers, natural fibers, and / or fibers from renewable resources.

[0072] These fibers may be in a modified or unmodified form, such as being provided with a sizing agent or chemically treated to improve adhesion to the polymer. Glass fibers are particularly preferred.

[0073] The glass fibers are provided with a sizing agent to protect the glass fibers, smooth the fibers, and improve the adhesion between the fibers and the matrix material. The sizing agent generally includes silanes, film formers, lubricants, wetting agents, binders, optionally antistatic agents and plasticizers, emulsifiers, and optionally other additives.

[0074] Specific examples of silanes are amino silanes, such as 3-trimethoxysilylpropylamine, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(3-trimethoxysilylpropyl)ethane-1,2-diamine, 3-(2-aminoethyl-amino)propyltrimethoxysilane, N-[3-(trimethoxysilyl)propyl]-1,2-ethane-diamine.

[0075] For example, the film formers are polyvinyl acetate, polyesters, and polyurethanes. A polyurethane-based sizing agent can be advantageously used.

[0076] The reinforcing fibers can be compounded into the polyoxymethylene matrix, for example, in an extruder or a kneader. However, in a process suitable for this purpose, the reinforcing fibers can also advantageously be in the form of continuous filament fibers coated or impregnated with a polyoxymethylene molding composition, and then processed or wound in the form of a continuous tow, or cut into the desired pellet length such that the fiber length and the pellet length are the same. Examples of processes particularly suitable for this purpose are pultrusion processes.

[0077] The reinforcing fibers can be present in the molding composition in an amount of 5 wt.% to 45 wt.%, for example 10 wt.% to 40 wt.%, where the weight is based on the total weight of the composition.

[0078] The polymer composition can also contain an impact modifier, such as a thermoplastic elastomer. A thermoplastic elastomer is a material having thermoplastic and elastomeric properties. Thermoplastic elastomers include styrene block copolymers, polyolefin blends (referred to as thermoplastic olefin elastomers), elastomer alloys, thermoplastic polyurethanes, thermoplastic copolyesters, and thermoplastic polyamides.

[0079] Thermoplastic elastomers that are very suitable for the present disclosure are polyester elastomers (TPE-E), thermoplastic polyamide elastomers (TPE-A), and especially thermoplastic polyurethane elastomers (TPE-U).

[0080] In a specific embodiment, thermoplastic polyurethane elastomer is used. For example, the thermoplastic polyurethane elastomer can have a flexible segment of long-chain diol and a hard segment derived from diisocyanate and chain extender. In one embodiment, the polyurethane elastomer is polyester-based, which is prepared by reacting a long-chain diol with a diisocyanate to produce a polyurethane prepolymer with isocyanate end groups, and then chain-extending the prepolymer with a diol chain extender. Representative long-chain diols are polyester diols, such as poly(butylene adipate) diol, poly(ethylene adipate) diol, and poly(ε-caprolactone) diol; and polyether diols, such as poly(tetramethylene ether) diol, poly(propylene oxide) diol, poly(ethylene oxide) diol, polycarbonate diol, and / or polyester polycarbonate diol. Suitable diisocyanates include 4,4'-methylenebis(phenyl isocyanate), 2,4-toluene diisocyanate, 1,6-hexamethylene diisocyanate, and 4,4'-methylenebis(epoxy isocyanate). Suitable chain extenders are C2-C6 aliphatic diols, such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol. One example of the thermoplastic polyurethane is characterized by substantially poly(adipic acid-co-butylene glycol-co-diphenylmethane diisocyanate).

[0081] The amount of the thermoplastic elastomer contained in the polymer composition can vary depending on various factors. For example, the thermoplastic elastomer can be present in an amount of about 0.5 wt.% to about 50 wt.%. In one embodiment, for example, the thermoplastic elastomer or impact modifier can be present in the composition in an amount less than about 25 wt.%, such as in an amount less than about 15 wt.%, such as in an amount less than about 10 wt.%. The thermoplastic elastomer or impact modifier is generally present in an amount greater than about 2 wt.%, such as in an amount greater than about 5 wt.%, such as in an amount greater than about 8 wt.%, such as in an amount greater than about 10 wt.%.

[0082] In one embodiment, when an impact modifier or a thermoplastic elastomer is present in the composition, the composition can further contain a coupling agent. The coupling agent can include polyisocyanates, such as diisocyanate or triisocyanate. The coupling agent can generally be present in an amount of about 0.1 wt.% to about 2 wt.%, such as about 0.1 wt.% to about 1 wt.%.

[0083] The compositions of the present disclosure can be compounded and formed into polymer articles using any techniques known in the art. For example, the corresponding compositions can be vigorously mixed to form a substantially homogeneous blend. The blend can be melt-kneaded at an elevated temperature (e.g., a temperature above the melting point of the polymers used in the polymer composition but below the degradation temperature). Alternatively, the corresponding compositions can be melted and mixed together in a conventional single-screw or twin-screw extruder. Preferably, the melt mixing is carried out at a temperature of from 100°C to 280°C, such as from 120°C to 260°C, such as from 140°C to 240°C or from 180°C to 220°C.

[0084] After extrusion, the composition can form pellets. The pellets can be formed into polymer articles by techniques known in the art (such as injection molding, thermoforming, blow molding, rotational molding, etc.).

[0085] The polymer compositions of the present disclosure can be used to produce a variety of molded parts. These parts can be formed by any suitable molding process (such as an injection molding process or by a blow molding process). Polymer articles that can be manufactured according to the present disclosure include, but are not limited to, knobs, door handles, automotive decorative trim, etc. For example, other polymer articles that can be manufactured according to the present disclosure include latches, levers, gears, pivot housings, speaker grilles, etc.

[0086] For example, referring to Figure 1 , an automotive interior is shown, which illustrates various automotive parts that can be manufactured according to the present disclosure. For example, the polymer composition can be used to produce automotive part 10, which includes at least a portion of an interior door handle. The polymer composition can also be used to produce parts on a steering column, such as automotive part 12. Generally, the polymer composition can be used to mold any suitable decorative trim or molding, such as molding 14.

[0087] The composition is also particularly suitable for the production of medical products. For example, referring to Figure 2 , an inhaler 20 is shown. Inhaler 20 includes a housing 22 attached to a mouthpiece 24. A plunger 26 is operatively associated with housing 22, and plunger 26 is for receiving a cartridge containing a composition to be inhaled. The composition can include a spray or a powder.

[0088] During use, inhaler 20 administers a metered dose of a drug, such as an asthma drug, to a patient. The asthma drug can be suspended or dissolved in a propellant, or can be contained in a powder. When the patient activates the inhaler to inhale the drug, a valve opens to allow the drug to exit the mouthpiece. According to the present disclosure, housing 22, mouthpiece 24, and plunger 26 can all be made of the polymer composition as described above.

[0089] Referring to Figure 3 , another medical product that can be manufactured according to the present disclosure is shown. InFigure 3 In FIG. Figure 3 , a medical syringe 30 is shown. The medical syringe 30 includes a housing 32 operably associated with a plunger 34. The housing 32 is slidable relative to the plunger 34. The medical syringe 30 may be spring-loaded. The medical syringe is used to inject a drug into a patient, typically into the thigh or buttock. The medical syringe may be needleless or may include a needle. When a needle is included, the needle tip is typically shielded within the housing prior to injection. On the other hand, a needleless syringe may include a cartridge of pressurized gas that can propel the drug through the skin without using a needle. According to the present disclosure, the housing 32 and / or the plunger 34 may be made of the polymer composition as described above.

[0090] While the polyoxymethylene polymer compositions of the present disclosure and polymer articles made therefrom provide improved emissions performance, the compositions and articles may also exhibit excellent mechanical properties (ISO 527 testing). For example, when tested according to ISO Test No. 527, the polymer composition may have a tensile modulus greater than about 1,200 MPa, such as greater than about 2,000 MPa. The tensile modulus is generally less than about 10,000 MPa.

[0091] The polymer composition may exhibit a notched Izod impact strength (ISO 179-1 testing) greater than about 3 kJ / m 2 , such as greater than about 6 kJ / m 2 at 23 °C. The notched Izod impact strength is generally less than about 20 kJ / m 2 .

[0092] The present disclosure may be better understood with reference to the following examples. Examples

[0093] The following examples are conducted to demonstrate some of the advantages and benefits of the polymer compositions made according to the present disclosure.

[0094] Example 1 Various polymer compositions were formulated, molded into test specimens, and tested for formaldehyde emissions. The polymer compositions included a formaldehyde copolymer. The polyoxymethylene polymer had a melt volume rate of about 9 cm 3 / 10 min according to ISO 1133 testing. In addition to the polyoxymethylene polymer, the polymer compositions also included 0.25 wt.% of a nucleating agent (polyoxymethylene terpolymer), 0.2 wt.% of an antioxidant (tris(ethylene glycol) bis(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate unless otherwise noted), and 0.2 wt.% of ethylenebis(stearamide).

[0095] Then various different additives are combined with the above polymer composition and the formaldehyde emission is tested. Each formulation is compounded on a 32 mm co-rotating twin-screw extruder (ZSK 32, Coperion, Germany). The test specimens are injection molded. The test specimens are molded at a temperature of 205 °C and dried at 140 °C for 2 hours. The test specimens have a thickness of 1 mm.

[0096] The samples are also tested according to the Ford 10-Liter Bag Method (hereinafter referred to as the "10-Liter Bag Method"), and the method is Test Reference No. BZ 108-01 (July 2, 2018).

[0097] In addition to the above components, the tested polymer composition also contains a formaldehyde stabilizer package. The formaldehyde stabilizer package contains a combination of 0.05 wt.% of tricalcium citrate and one or more emission control agents. The formaldehyde emission of the test formulations is tested according to VDA 275. The following table lists the emission control agents present in the formulations and the formaldehyde emission results. Sample Number Emission Control Agent Formaldehyde Emission (µg / g) 1 0.05% Melamine 27.66 2 0.05% Melamine and 0.05% Copolyamide 26.07 3 0.45% Benzoguanamine and 0.05% Copolyamide 9.94 4 0.07% Sebacic Diacyl Hydrazide and 0.5% MDI 24.89 5 0.07% Sebacic Diacyl Hydrazide and 0.25% Substituted Hydantoin 0.43 6 0.07% Sebacic Diacyl Hydrazide and 0.5% MDI 31.34 7 0.07% Dodecanedioyl Diacyl Hydrazide and 0.5% MDI 35.91 8 0.07% Dodecanedioyl Diacyl Hydrazide and 0.25% Substituted Hydantoin 0.39 9 0.07% Sebacic Diacyl Hydrazide and 0.25% Substituted Hydantoin 0.39 10 0.07% Dodecanedioyl Diacyl Hydrazide and 0.25% Substituted Hydantoin 0.39 11 0.07% Dodecanedioyl Diacyl Hydrazide and 0.5% MDI 21.06

[0098] The above-mentioned substituted hydantoin is 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionylhydrazide), which is also considered to have coupling agent properties. The MDI in the above table is methylene diphenyl diisocyanate, which is called a coupling agent. In Samples 4, 5, 10, and 11 as above, the formulation contains two phenolic antioxidants. The first phenolic antioxidant is present in an amount of 0.15 wt.% and contains triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate. The second phenolic antioxidant contained in the formulation is present in an amount of 0.05 wt.%, and contains N,N'-(hexane-1,6-diyl) bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionamide]. As shown above, the formulation containing the substituted hydantoin significantly reduces the formaldehyde emission.

[0099] The formaldehyde emission of the formulations is also tested using the 10-Liter Bag Method as described above. The following results are obtained: Sample Number <![CDATA[Formaldehyde emission (µg / m 3 )]]> 1 2974 2 4520 3 1279 4 59 5 51 6 506 7 6485 8 32 9 40 10 49 11 8910 A formulation is also tested, which contains 0.05% of copolyamide in addition to the other components contained in the other formulations. The formaldehyde emission result is 5517 µg / m 3 .

[0100] The color stability of the formulations is also tested. Samples molded at a temperature of 205 °C are also tested. The following results are obtained: Sample Number Yellowness Tested According to DIN 6167 <![CDATA[L * > <![CDATA[a * > <![CDATA[b * > Control -6.69 78.51 -0.69 -2.60 1 -6.96 78.89 -0.65 -2.74 2 -6.78 79.75 -0.63 -2.70 3 -6.69 79.05 -0.68 -2.62 4 3.89 87.58 -0.11 1.94 5 1.97 87.94 -0.12 1.01 6 -4.17 73.96 -0.23 -1.63 7 -3.92 74.20 -0.26 -1.52 8 -3.68 73.87 -0.08 -1.47 9 -3.65 74.50 -0.08 -1.48 10 -3.80 74.54 -0.11 -1.53 11 -3.23 74.79 -0.27 -1.27 The melt flow rate of the composition was also tested at 190 °C and a load of 2.16 kg. The following results were obtained: Sample Number <![CDATA[Melt flow rate (cm 3 / 10 min)]]> 1 7.04 2 7.56 3 7.73 4 6.86 5 7.64 6 6.48 7 6.45 8 7.67 9 7.50 10 7.46 11 6.68 Example 2 Example 1 was repeated using the same method and components. Under the VDA 75 test, the formaldehyde emissions and melt flow rate of the test formulation were tested. The following results were obtained: Sample Number Emission Control Agent Formaldehyde Emission (mg / kg) <![CDATA[MFR (cm 3 / 10 min) (ISO 1133 test)]]> 12 None 65.90 8.48 13 0.05% Melamine 25.20 8.64 14 0.05% Substituted Hydantoin 28.30 8.39 15 0.05% Melamine, 0.05% Substituted Hydantoin 23.10 8.51 16 0.05% Melamine, 0.1% Substituted Hydantoin 13.80 8.49 17 0.05% Melamine, 0.2% Substituted Hydantoin 14.50 8.47 18 0.05% Sebacic Diacyl Hydrazide 27.30 8.27 19 0.05% Sebacic Diacyl Hydrazide, 0.05% Substituted Hydantoin 5.70 8.20 20 0.05% Sebacic Diacyl Hydrazide, 0.1% Substituted Hydantoin 0.50 8.34 21 0.05% Sebacic Diacyl Hydrazide, 0.2% Substituted Hydantoin 0.80 8.37 22 0.1% Substituted Hydantoin 9.2 8.16 23 0.2% Substituted Hydantoin 1.4 8.46 The color stability of the above formulation was also tested. The following results were obtained: Sample Number Yellowness Tested According to DIN 6167 <![CDATA[L * > <![CDATA[a * > <![CDATA[b * > 12 -2.64 73.82 -0.46 -0.91 13 -3.87 74.15 -0.07 -1.57 14 -4.03 74.01 -0.1 -1.62 15 -4.50 73.50 -0.12 -1.79 16 -4.40 74.12 -0.14 -1.76 17 -3.93 74.37 -0.12 -1.58 18 -3.76 74.16 -0.08 -1.53 19 -3.74 73.95 -0.08 -1.51 20 -4.34 73.95 -0.17 -1.72 21 -4.15 73.90 -0.18 -1.64 22 -4.11 74.22 -0.11 -1.65 23 -3.93 73.97 -0.12 -1.57 Without departing from the spirit and scope of the present invention, those of ordinary skill in the art can make these and other modifications and variations to the present invention, the spirit and scope of which are 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. Further, those of ordinary skill in the art will understand that the foregoing description is by way of example only and is not intended to limit the present invention as further described in the appended claims.

Claims

1. A polymer composition comprising: A polyoxymethylene polymer; and A formaldehyde stabilizer package for reducing formaldehyde emissions, the formaldehyde stabilizer package comprising at least one emission control agent, the emission control agent comprising a combination of a substituted hydantoin alone or an aliphatic carboxylic acid hydrazide and a substituted hydantoin, wherein the aliphatic carboxylic acid hydrazide is present in a weight ratio of about 1:1.1 to about 1:8.5 relative to the substituted hydantoin.

2. The polymer composition according to claim 1, wherein The aliphatic carboxylic acid hydrazide is present in a weight ratio of about 1:1.5 to about 1:7.5, such as about 1:2 to about 1:5.5, relative to the substituted hydantoin.

3. The polymer composition according to claim 1, wherein The substituted hydantoin comprises two hydrazinocarbonylalkyl groups.

4. The polymer composition according to claim 1, wherein The substituted hydantoin includes 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionylhydrazide).

5. The polymer composition according to any one of the preceding claims, wherein, The aliphatic carboxylic acid hydrazide includes sebacic dihydrazide, dodecanedioic dihydrazide or a mixture thereof.

6. The polymer composition according to any one of the preceding claims, wherein, The aliphatic carboxylic acid hydrazide is present in the polymer composition in an amount less than about 0.15 wt.%.

7. The polymer composition according to any one of the preceding claims, wherein, The polymer composition shows a yellowness index less than 0, such as less than about -1, such as less than about -2, such as less than about -3 and greater than about -10 when tested according to DIN6167 at a molding temperature of 205 °C.

8. The polymer composition according to any one of the preceding claims, wherein, The polymer composition exhibits an L value at a molding temperature of 205 °C that is less than about 80, such as less than about 78, such as less than about 76, and greater than about 60, such as greater than about 70. * value.

9. The polymer composition according to any one of the preceding claims, wherein, The polymer composition shows a formaldehyde emission less than about 1 ppm, such as less than about 0.8 ppm, such as less than about 0.6 ppm, such as less than about 0.4 ppm when tested according to VDA-275 at a thickness of 1 mm, a molding temperature of 205 °C and after drying at 140 °C for 2 hours.

10. The polymer composition according to any one of the preceding claims, wherein, The polymer composition further comprises an acid scavenger, the acid scavenger comprising a metal salt of an organic acid.

11. The polymer composition according to claim 10, wherein, The organic acid has a carbon chain length of 8 carbon atoms or less.

12. The polymer composition according to claim 10, wherein, The acid scavenger includes tricalcium citrate.

13. The polymer composition according to claim 10, 11 or 12, wherein, The acid scavenger is present in the polymer composition in an amount less than about 0.5 wt.%, such as in an amount less than about 0.2 wt.%, such as in an amount less than about 0.08 wt.%, and in an amount greater than about 0.001 wt.%.

14. The polymer composition according to any one of the preceding claims, wherein, The polymer composition shows a formaldehyde emission of less than about 100 µg / m when tested according to the 10-litre bag test 3 , for example less than about 80 µg / m 3 , for example less than about 60 µg / m 3 , for example less than about 55 µg / m 3 .

15. The polymer composition according to any one of the preceding claims, wherein, The substituted hydantoin is present in the polymer composition in an amount greater than about 0.05 wt.%, such as in an amount greater than about 0.07 wt.%, such as in an amount greater than about 0.15 wt.%, such as in an amount greater than about 0.2 wt.%, such as greater than about 0.22 wt.%, and less than about 0.5 wt.%.

16. The polymer composition according to any one of the preceding claims, wherein, The polyoxymethylene polymer has a melt flow rate of about 5 cm 3 / 10 min to about 15 cm 3 / 10 min when tested at 190 °C under a load of 2.16 kg.

17. The polymer composition according to any one of the preceding claims, wherein, The polymer composition further comprises a nucleating agent in an amount of about 0.05 wt.% to about 1 wt.%, a phenolic antioxidant in an amount of about 0.05 wt.% to about 2 wt.% and a lubricant in an amount of about 0.05 wt.% to about 1.5 wt.%.

18. The polymer composition according to any one of the preceding claims, wherein, The polymer composition further comprises a thermoplastic elastomer in an amount of about 5 wt.% to about 30 wt.%.

19. The polymer composition according to any one of the preceding claims, wherein, The polymer composition further comprises a reinforcing fiber in an amount of about 3 wt.% to about 40 wt.%.

20. The polymeric composition according to any one of the preceding claims, wherein, The polymer composition further comprises a UV stabilizer.

21. A polymer composition comprising: A polyoxymethylene polymer; A formaldehyde stabilizer package for reducing formaldehyde emissions, said formaldehyde stabilizer package comprising at least one emission control agent, said emission control agent comprising a combination of a substituted hydantoin alone or an aliphatic carboxylic acid hydrazide and a substituted hydantoin, said substituted hydantoin comprising two hydrazinocarbonylalkyl groups; and An acid scavenger, which comprises a metal salt of an organic acid having a carbon chain length of 8 carbon atoms or less.

22. The polymer composition according to claim 21, wherein, Said acid scavenger comprises tricalcium citrate.

23. The polymer composition according to claim 21, wherein Said aliphatic carboxylic acid hydrazide is present in a weight ratio of about 1:1.5 to about 1:7.5, such as about 1:2 to about 1:5.5, relative to said substituted hydantoin.

24. The polymer composition according to claim 21, wherein Said aliphatic carboxylic acid hydrazide comprises dihydrazide.

25. The polymer composition according to claim 21, wherein Said substituted hydantoin comprises 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionylhydrazide).

26. The polymer composition according to claim 21, wherein Said aliphatic carboxylic acid hydrazide comprises sebacic dihydrazide, dodecanedioic dihydrazide or a mixture thereof.

27. The polymer composition according to any one of the preceding claims, wherein, Said aliphatic carboxylic acid hydrazide is present in an amount of less than about 0.15 wt.% in said polymer composition.

28. A polymer composition comprising: A polyoxymethylene polymer; A formaldehyde stabilizer package for reducing formaldehyde emissions, said formaldehyde stabilizer package comprising at least one emission control agent, said emission control agent comprising a combination of a substituted hydantoin alone or an aliphatic carboxylic acid hydrazide and a substituted hydantoin, said substituted hydantoin containing two hydrazinocarbonylalkyl groups; and Wherein the polymer composition shows a yellowness index of less than -1 and greater than about -10 when tested at a molding temperature of 205 °C according to DIN 6167, shows an L value of less than about 80 and greater than about 60 at a molding temperature of 205 °C, shows a formaldehyde emission of less than about 1 ppm when tested according to VDA-275 at a thickness of 1 mm, a molding temperature of 205 °C and after drying at 140 °C for 2 hours, and shows a formaldehyde emission of less than about 80 µg / m * when tested according to the 10-litre bag test. 3 ​ 29. A molded article made from the polymer composition according to any one of the preceding claims.

30. The molded article according to claim 29, wherein said molded article comprises automotive interior parts.

31. The shaped article according to claim 29, wherein, Said molded article comprises a latch, a lever, a gear, a pivot housing, a speaker grille, a door handle, a decorative trim, a bracket or a seat rail.

32. The molded article according to claim 29, wherein, Said molded article comprises an inhaler or a syringe.

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