Low-emission polyoxymethylene compositions with color stability

Abstract

Disclosed is a polyoxymethylene polymer composition containing a formaldehyde stabilizer package. In one embodiment, the formaldehyde stabilizer package contains a substituted hydantoin, which has been found to dramatically reduce formaldehyde emissions, either alone or in combination with another release control agent.

Description

[Technical Field]

[0001] Related Applications

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

[0002]

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

[0003]

[0003] While polyacetal resins have many useful properties, these polymers tend to degrade when heated and are inherently unstable in oxidizing atmospheres or acidic or alkaline environments. Specifically, polyacetal resins tend to release formaldehyde during processing and after the polymer has been molded into a part. Formaldehyde is not only a contaminant, but can also have a detrimental effect on metal parts that may be installed with the polymer. For example, formaldehyde can easily oxidize to formic acid, which can corrode metals or cause discoloration.

[0004] In view of the above, those skilled in the art have attempted to combine polyacetal polymers with various compounds to reduce formaldehyde emissions. For example, polyacetal polymers have previously been combined with melamine to achieve lower formaldehyde emission performance. In addition, various other chemicals have been suggested for reducing formaldehyde emissions.

[0005]

[0005] Although various chemicals used to date have successfully reduced formaldehyde emissions from products made from polyoxymethylene polymers, further improvements in formaldehyde emissions are needed. For example, stricter government regulations continue to require further improvements in reducing formaldehyde emissions.

[0006] Unfortunately, however, when an additive is combined with a polyacetal polymer to enhance one property, the additive may have a detrimental effect on another property. For example, adding greater amounts of formaldehyde scavenger to a polyoxymethylene polymer composition may impair one or more properties of the polymer. For example, too much formaldehyde scavenger may cause molded articles to discolor during use and / or begin to adversely affect other physical properties. Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above, there is a need for improved formaldehyde stabilizer packages that can further reduce formaldehyde emissions without adversely affecting other properties of polyoxymethylene polymer compositions. [Means for solving the problem]

[0008]

[0008] Generally, the present disclosure is directed to polymer compositions containing primarily polyacetal resins, and molded articles made from the compositions. The polymer compositions of the present disclosure are specifically formulated to exhibit extremely low formaldehyde emissions. For example, polyoxymethylene polymer compositions formulated according to the present disclosure may exhibit formaldehyde emissions of less than about 2 ppm, e.g., less than about 1 ppm, when tested according to the VDA275 test. The VDA275 test (German Automotive Industry Recommendation No. 275) was codified by Kraftfahrwesen eV in July 1994.

[0009] In one embodiment, for example, the polymer composition of the present disclosure includes a polyoxymethylene polymer in combination with a formaldehyde stabilizer package to reduce formaldehyde emissions. In one embodiment, the formaldehyde stabilizer package may include at least one release control agent. In particular, certain substituted hydantoins have been found to be highly effective in reducing formaldehyde emissions. The substituted hydantoins may be used alone or in combination with other hydrazides and / or other release control agents. In one embodiment, the polymer composition is formulated to contain the substituted hydantoin without any significant adverse effect on other properties of the molded article made from the composition. For example, in one embodiment, molded articles made in accordance with the present disclosure exhibit highly stable color quality, making the polymer composition well suited for producing decorative pieces for automotive interiors, and the like.

[0010] In one embodiment, for example, the present disclosure is directed to a polyoxymethylene polymer in combination with a formaldehyde stabilizer package comprising a substituted hydantoin, alone or in combination with one or more aliphatic carboxylic acid hydrazides. When the substituted hydantoin is present in combination with an aliphatic carboxylic acid hydrazide, the weight ratio of the aliphatic carboxylic acid hydrazide to 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, for example, from about 1:2 to about 1:5.5.

[0011] The substituted hydantoin may be present in the polymer composition in an amount less than about 0.6% by weight, e.g., less than about 0.5% by weight, e.g., less than about 0.4% by weight, e.g., less than about 0.35% by weight, e.g., less than about 0.3% by weight, and generally in an amount greater than about 0.01% by weight, e.g., greater than about 0.05% by weight, e.g., greater than about 0.07% by weight, e.g., greater than about 0.09% by weight, e.g., greater than about 0.1% by weight, e.g., greater than about 0.12% by weight, e.g., greater than about 0.15% by weight, e.g., greater than about 0.17% by weight, e.g., greater than about 0.2% by weight. The substituted hydantoin may contain two hydrazinocarbonylalkyl groups. The substituted hydantoin may have a melting point of less than about 150° C., for example, less than about 140° C., for example, less than about 130° C., for example, less than about 125° C., and generally greater than about 100° C. The substituted hydantoin may have a relatively low curing temperature of less than about 125° C., for example, less than about 120° C., for example, less than about 115° C., and generally greater than about 100° C., for example, greater than about 105° C. In one particular embodiment, the substituted hydantoin comprises 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide).

[0012] As described above, the substituted hydantoin can be combined with an aliphatic carboxylic acid hydrazide. The aliphatic carboxylic acid hydrazide may be a dihydrazide. Examples of dihydrazides include sebacic acid dihydrazide, dodecanedioic acid dihydrazide, or mixtures thereof. When present, the aliphatic carboxylic acid dihydrazide may be present in a relatively small amount in the polymer composition due to the presence of the substituted hydantoin. For example, the aliphatic carboxylic acid hydrazide may be present in the polymer composition in an amount less than the amount of the substituted hydantoin described above, such as less than about 0.15% by weight, e.g., less than about 0.1% by weight.

[0013] The formaldehyde stabilizer package may also include an acid scavenger. The acid scavenger may include a metal salt of an organic acid. In one particular 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 includes tricalcium citrate. The acid scavenger may 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 %, or greater than about 0.001 wt %.

[0014] Other optional components that may be included in the polymer composition include a nucleant in an amount of about 0.05% to about 1% by weight, a phenolic antioxidant in an amount of about 0.05% to about 2% by weight, and a lubricant in an amount of about 0.05% to about 1.5% by weight. The polymer composition may also optionally contain a thermoplastic elastomer, reinforcing fibers, and / or UV stabilizers.

[0015] The polymer composition and molded articles made therefrom can exhibit excellent physical and mechanical properties. The polymer composition may, for example, exhibit a yellowness index of less than 0, for example less than about -1, for example less than about -2, for example less than about -3, and greater than about -10, when tested according to test DIN 6167 at a molding temperature of 205°C. The polymer composition may also exhibit an L of less than about 80, for example less than about 78, for example less than about 76, and greater than about 60, for example greater than about 70, at a molding temperature of 205°C. * The value may also be shown.

[0016] The polymer compositions can also be tested for formaldehyde emissions according to the 10-Liter Bag Test. Polymer compositions made according to the present disclosure, for example, have a formaldehyde emission of about 100 μg / m when tested according to the 10-Liter Bag Test. 3 less than about 80 μg / m 3 less than about 60 μg / m 3 less than about 55 μg / m 3 It may exhibit formaldehyde emissions of less than 1000 ppm.

[0017] Various types of molded articles can be made from polymer compositions containing the formaldehyde stabilizer package according to the present disclosure. For example, molded articles can include interior automotive parts. Molded articles can include latches, levers, gears, pivot housings, speaker grilles, door handles, decorative trim pieces, brackets, seat rails, and the like. Medical products, such as inhaler or injector components, can also be made from the polymer compositions.

[0018]

[0018] Other features and aspects of the present disclosure are discussed in more detail below.

[0019] The detailed enabling disclosure of the present disclosure is set forth in more detail in the remainder of the specification, including reference to the accompanying drawings. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a perspective view of the interior of an automobile illustrating various molded articles that can be made in accordance with the present disclosure. [Figure 2] FIG. 2 is a perspective view of a medical inhaler that can be made from molded parts according to the present disclosure. [Figure 3] FIG. 3 is a perspective view of a medical injector containing a molded part made in accordance with the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0020] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. Detailed Description It will be understood by those skilled in the art that the discussion of the present invention is a description of exemplary embodiments only and is not intended to limit the broader aspects of the present disclosure.

[0021]

[0021] In general, the present disclosure is directed to polymer compositions containing polyacetal resins, particularly polyoxymethylene copolymers, that exhibit low formaldehyde emissions. The polymer compositions are well suited for use in molding processes to produce molded articles. The polymer compositions may contain one or more colorants to produce molded articles having any desired color. The molded articles can be used in a wide variety of applications and in multiple fields. In one embodiment, molded articles designed to function as, for example, automotive parts, e.g., automotive parts designed for use in the interior of vehicles such as cars and trucks, can be made according to the present disclosure.

[0022]

[0022] More particularly, the present disclosure is directed to polymer compositions containing a polyacetal resin in combination with a formaldehyde stabilizer package. The formaldehyde stabilizer package includes at least one release control agent. Specifically, it has been discovered that substituted hydantoins having certain properties have proven to be highly effective release control agents, either alone or in combination with other hydrazides. The substituted hydantoins of the present disclosure have been found to dramatically reduce formaldehyde emissions from polyoxymethylene polymer compositions, for example, without adversely interfering with other properties of the polymer composition or molded articles made from the compositions. For example, the substituted hydantoins have been found to significantly reduce formaldehyde emissions while also producing polymer compositions with excellent pigment retention and stability properties.

[0023] In one aspect, the substituted hydantoin contains two hydrazinocarbonyl alkyl groups. In one aspect, certain substituted hydantoins for incorporation into polymer compositions may have relatively low melting points and relatively low cure temperatures. For example, the melting point of the substituted hydantoin may 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 may 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 may be designed to cure at temperatures 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 (after 1 hour of exposure to such temperatures).

[0024] In one particular embodiment, the substituted hydantoin may include 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide).

[0025]

[0025] Hydantoin compounds having two hydrazinocarbonyl alkyl groups have previously been suggested for use in polyacetal resin compositions to reduce formaldehyde generation from molded articles. For example, U.S. Patent Application Publication No. 2021 / 0355314 is directed to polyacetal resin compositions and is incorporated herein by reference. However, the examples in U.S. Patent Application Publication No. 2021 / 0355314 teach that hydantoin compounds are generally used in very small amounts and that hydantoin compounds alone can produce adverse results. In contrast, it has been discovered that selected amounts of substituted hydantoins alone can be very effective in reducing formaldehyde emissions without any adverse consequences. In addition, it has been discovered that using substituted hydantoin compounds in combination with other hydrazide compounds can be very effective in reducing formaldehyde emissions at specific weight ratios while preserving the mechanical and aesthetic properties of polymer compositions and molded articles made from the compositions.

[0026] In one embodiment, for example, the formaldehyde stabilizer package of the present disclosure may contain a substituted hydantoin release control agent in combination with one or more aliphatic carboxylic acid hydrazides. The aliphatic carboxylic acid hydrazides may be dihydrazides. Specific examples of dihydrazides include, for example, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, or mixtures thereof.

[0027] In one embodiment, the formaldehyde stabilizer package of the present disclosure contains a substituted hydantoin in an amount equal to or greater than the amount of aliphatic carboxylic acid hydrazide present in the formulation. In one aspect, for example, the one or more aliphatic carboxylic acid hydrazides are present in a weight ratio relative to the substituted hydantoin of about 1:1.1 to about 1:8.5, e.g., about 1:1.5 to about 1:7.5, e.g., about 1:2 to about 1:5.5. While the weight ratio can vary depending on the specific application, the above weight ratios have been found to be particularly effective in producing molded articles with enhanced color stability while reducing formaldehyde emissions, making the molded articles particularly well suited for producing decorative pieces for the interior of vehicles such as automobiles or for producing parts for home appliances.

[0028]

[0028] The one or more aliphatic carboxylic acid hydrazides may 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 hydrazide present in the polymer composition can be minimized. For example, in one embodiment, the one or more aliphatic carboxylic acid hydrazides are present in the polymer composition in an amount less than 0.2 wt%, e.g., less than about 0.15 wt%, e.g., less than about 0.12 wt%, e.g., less than about 0.1 wt%, e.g., less than about 0.09 wt%, e.g., less than about 0.08 wt%. Minimizing the amount of aliphatic carboxylic acid hydrazide present in the composition can provide various advantages and benefits, such as minimizing free hydrazide in the composition and providing color stability.

[0029] The amount of substituted hydantoin present in the polymer composition may vary depending on whether the substituted hydantoin is present in the composition alone or in combination with other release-controlling agents. Generally, the substituted hydantoin may be present in the polymer composition in an amount of 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 release-controlling agent present in the composition. For example, the substituted hydantoin may be present in the polymer composition in an amount greater than 0.07 wt. %, e.g., greater than about 0.09 wt. %, e.g., greater than about 0.1 wt. %, e.g., greater than about 0.12 wt. %, e.g., greater than about 0.15 wt. %, e.g., greater than about 0.17 wt. %, e.g., greater than about 0.2 wt. %, e.g., greater than about 0.22 wt. %, e.g., greater than about 0.24 wt. %. In various embodiments, the substituted hydantoin may be present in the polymer composition in an amount less than about 0.8 wt%, such as less than about 0.6 wt%, such as less than about 0.55 wt%, such as less than about 0.5 wt%, such as 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%.

[0030] In one embodiment, the formaldehyde stabilizer package includes the release control agent described above, but excludes other formaldehyde scavengers that have been used in the past. For example, the polymer composition may be formulated to be melamine-free. In fact, the polymer composition may be formulated to be free of any melamine or any melamine derivatives. In one aspect, the polymer composition is free of any guanamine compounds.

[0031] Other release control agents that may be present in the formaldehyde stabilizer package include amino acids, such as arginine, or alkylene ureas, such as ethylene urea. The additional release control agents may generally be present in the polymer composition in an amount of from about 0.01% to about 0.5% by weight, including all 0.01% increments therebetween.

[0032] The formaldehyde stabilizer packages of the present disclosure may also contain an acid scavenger. It is believed that certain acid scavengers are particularly well suited for combination with substituted hydantoins.

[0033] In one particular embodiment, for example, the acid scavenger may comprise a metal salt of an organic acid, where the organic acid has a carbon chain length of 8 carbon atoms or less. For example, in one particular embodiment, the acid scavenger may comprise a metal citrate, such as tricalcium citrate.

[0034] In another embodiment, the acid scavenger may comprise a salt of a carboxylic acid, such as a metal salt of a fatty acid. The carboxylic acid salt may comprise an alkaline earth metal salt, such as an alkaline earth metal salt of a fatty acid. The cation of the salt may comprise, for example, calcium, barium, lithium, sodium, magnesium, zinc, etc.

[0035] The fatty acids may generally contain carbon chain lengths of from about 3 carbon atoms to about 20 carbon atoms. The fatty acids may include dicarboxylic acids or tricarboxylic acids. Specific examples include metal salts of propionic acid, stearic acid, butanoic acid, hexanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, and the like. Specific examples include calcium propionate, calcium 12-hydroxystearate, calcium stearate, and mixtures thereof.

[0036] One or more acid scavengers may be present in the polymer composition generally 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, relatively small amounts of acid scavenger are necessary. For example, the acid scavenger may be present in an amount less than 1 wt. %, e.g., less than about 0.8 wt. %, e.g., less than about 0.5 wt. %, e.g., less than about 0.2 wt. %, or even as little as less than about 0.08 wt. One or more acid scavengers are generally present in an amount greater than 0.001 wt. %, e.g., greater than about 0.01 wt. %.

[0037]

[0037] The formaldehyde stabilizer package of the present disclosure described above, when combined with polyoxymethylene polymers, can produce polymer compositions and molded articles that not only have low formaldehyde emission properties, but also have excellent mechanical properties and visual appeal.

[0038] 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, and even less than about 0.4 ppm, in accordance with VDA 275. The above formaldehyde emission characteristics can be obtained even when test plaques have a thickness of 1 mm and are formed at a molding temperature of 205°C. In one aspect, testing can be performed after drying the test plaques at 140°C for 2 hours.

[0039] Another formaldehyde emission test is the 10 liter bag test. Polymer compositions made in accordance with the present disclosure emit about 100 μg / m when tested according to the 10 liter bag test. 3 less than about 80 μg / m 3 less than about 60 μg / m 3 less than about 55 μg / m 3The 10 liter bag test can also be performed on samples molded at a temperature of 205°C.

[0040] The polymer compositions and molded articles made therefrom can also exhibit excellent color stability. For example, when tested according to DIN 6167 at a molding temperature of 205° C., the polymer compositions can exhibit a yellowness index of less than 0, e.g., less than about −1, e.g., less than about −2, e.g., less than about −3, and generally greater than about −10.

[0041]

[0001] Polymer compositions can also be tested according to the CIELAB color scale. As used herein, the CIELab color value L * , a * , and b * is measured according to the color space specified by the International Commission on Illumination. * a * b * The color system was standardized by the International Commission on Illumination (CIE) in 1976. * The L value is utilized herein to define the darkness / lightness of a polymer composition, which is a unit of color measurement in the aforementioned CIELab system. Colors can be matched according to CIELab. * a * b * In the color system, L * refers to brightness expressed numerically.

[0042] For example, the polymer composition, when molded at a temperature of 205° C., has an L 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. * The value can be shown.

[0043] The formaldehyde stabilizer package of the present disclosure is particularly formulated in combination with a polyoxymethylene polymer. Generally, any suitable polyoxymethylene polymer may be incorporated into the polymer composition.

[0044]

[0044] Polyoxymethylene polymers can be prepared by polymerizing polyoxymethylene-forming monomers, such as trioxane or a mixture of trioxanes, with a cyclic acetal, such as dioxolane, in the presence of a molecular weight regulator, such as a glycol. The polyoxymethylene polymer used in the polymer composition may comprise a homopolymer or a copolymer. According to one embodiment, the polyoxymethylene is a homo- or copolymer containing at least 50 mol%, such as at least 75 mol%, for example at least 90 mol%, of -CHO- repeating units, for example at least 97 mol%.

[0045] In one embodiment, a polyoxymethylene copolymer is used. The copolymer may contain about 0.01 mol % to about 20 mol %, specifically about 0.5 mol % to about 10 mol %, of repeating units comprising a saturated or ethylenically unsaturated alkylene group having at least two carbon atoms or a cycloalkylene group having a sulfur atom or an oxygen atom in the chain, and may contain one or more substituents selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl, heteroaryl, halogen, or alkoxy. In one embodiment, a cyclic ether or acetal is used that can be introduced into the copolymer via a ring-opening reaction.

[0046] Preferred cyclic ethers or acetals are those having the formula:

[0047] [ka]

[0048] In the formula, x is 0 or 1, and R 2 is a C2-C4 alkylene group, optionally bearing one or more substituents, which may be C1-C4 alkyl or C1-C4 alkoxy groups, and / or halogen atoms, preferably chlorine atoms. Examples include ethylene oxide, propylene 1,2-oxide, butylene 1,2-oxide, butylene 1,3-oxide, 1,3-dioxane, 1,3-dioxolane, and 1,3-dioxepane as cyclic ethers, as well as linear oligo- or polyformals, such as polydioxolane or polydioxepane, as comonomers. It is particularly advantageous to use copolymers composed of 99.5-95 mol % trioxane and 0.01-5 mol %, e.g., 0.5-4 mol %, of one of the aforementioned comonomers. In one embodiment, the polyoxymethylene polymer contains a relatively small amount of comonomer. For example, the comonomer may be present in an amount 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%.

[0049] The polymerization may be carried out as a precipitation polymerization or in the melt. For example, polyoxymethylene copolymers may be formed via solution hydrolysis, in which precipitates or powders with very few unstable end groups are formed. By appropriately selecting polymerization parameters such as the duration of polymerization or the amount of molecular weight regulator, the molecular weight of the resulting polymer, and therefore its MVR value, can be adjusted.

[0050] In one embodiment, the polyoxymethylene polymer used in the polymer composition may contain a relatively large amount of reactive or functional groups at the terminal positions. The reactive groups may include, for example, —OH or —NH groups.

[0051] In one embodiment, the polyoxymethylene polymer may have terminal hydroxyl groups, e.g., hydroxyethylene groups and / or hydroxyl side groups, at at least about 50% of all terminal sites on the polymer. For example, the polyoxymethylene polymer may have hydroxyl groups on at least about 70%, e.g., at least about 80%, e.g., at least about 85%, of its terminal groups, based on the total number of terminal groups present. It should be understood that the total number of terminal groups present includes all side chain terminal groups.

[0052] In one embodiment, the polyoxymethylene polymer has a terminal hydroxyl group content of at least 15 mmol / kg, e.g., at least 18 mmol / kg, e.g., at least 20 mmol / kg. In one embodiment, the terminal hydroxyl group content is in the range of 18 to 50 mmol / kg. In an alternative embodiment, the polyoxymethylene polymer may contain terminal hydroxyl groups in an amount less than 20 mmol / kg, e.g., less than 18 mmol / kg, e.g., less than 15 mmol / kg. For example, the polyoxymethylene polymer may contain terminal hydroxyl groups in an amount of from about 5 mmol / kg to about 20 mmol / kg, e.g., from about 5 mmol / kg to about 15 mmol / kg. For example, polyoxymethylene polymers having lower terminal hydroxyl group contents but higher melt volume-flow rates may be used.

[0053] In addition to or instead of the terminal hydroxyl groups, the polyoxymethylene polymer may also have other terminal groups common to these polymers. Examples of these are alkoxy, formate, acetate or aldehyde groups. According to one embodiment, the polyoxymethylene is a homo- or copolymer containing at least 50 mol%, for example at least 75 mol%, for example at least 90 mol%, of -CHO- repeating units, for example at least 95 mol%.

[0054] In one embodiment, polyoxymethylene polymers can be produced by a cationic polymerization process followed by solution hydrolysis to remove any unstable end groups. During cationic polymerization, glycols such as ethylene glycol or methylal can be used as chain terminators. Heteropolyacids, triflic acids, or boron compounds can be used as catalysts.

[0055] The polyoxymethylene polymer may have any suitable molecular weight. The molecular weight of the polymer may be, for example, from about 4,000 g / mol to about 20,000 g / mol. In other embodiments, however, the molecular weight may be significantly greater than 20,000 g / mol, for example, from about 20,000 g / mol to about 100,000 g / mol.

[0056] The polyoxymethylene polymer present in the composition generally has a viscosity of from about 0.1 to about 80 cm when determined at 190° C. and 2.16 kg according to ISO 1133. 3 In one embodiment, the polyoxymethylene polymer may have a melt flow index (MFI) in the range of about 5 cm / 10 min. 3 / 10 minutes ~ approx. 15cm 3 / 10 minutes, for example, about 8 cm 3 / 10 minutes ~ approx. 12cm 3 In an alternative embodiment, a polyoxymethylene polymer having a relatively high melt flow index may be used. For example, the polyoxymethylene polymer may have a melt flow index of about 18 cm / 10 min. 3 / 10 minutes ~ approx. 40cm 3 / 10 minutes, for example, about 20 cm 3 / 10 minutes ~ approx. 35cm 3 It may have a melt flow index of 1 / 10 minutes.

[0057] A suitable commercially available polyoxymethylene polymer is available from Celanese under the trade name Hostaform® (HF). The polyoxymethylene polymer may be present in the polyoxymethylene polymer composition in an amount of at least 50 wt.%, such as at least 60 wt.%, for example at least 70 wt.%, for example at least 80 wt.%, for example at least 85 wt.%, for example at least 90 wt.%, for example at least 93 wt.%. Generally, the polyoxymethylene polymer is present in an amount of less than about 100 wt.%, for example less than about 99 wt.%, for example less than about 97 wt.%, where the weight is based on the total weight of the polyoxymethylene polymer composition.

[0058] The polymer compositions of the present disclosure may also contain other known additives, such as antioxidants, UV or heat stabilizers, impact modifiers and / or reinforcing fibers, etc. In addition, the compositions may contain processing aids, such as adhesion promoters, lubricants, nucleating agents, mold release agents, fillers, or antistatic agents, as well as additives that impart desirable properties to the compositions and articles or parts produced therefrom.

[0059] In one embodiment, an ultraviolet light stabilizer may be present. The ultraviolet light stabilizer may include benzophenone, benzotriazole, or benzoate. When present, the ultraviolet light absorber may be present in the polymer composition in an amount of at least about 0.01 wt.%, for example, at least about 0.05 wt.%, for example, at least about 0.075 wt.%, and less than about 1 wt.%, for example, less than about 0.75 wt.%, for example, less than about 0.5 wt.%, where the weight is based on the total weight of the respective polymer composition.

[0060] In one embodiment, a nucleating agent may be present. The nucleating agent can increase crystallinity and may include an oxymethylene terpolymer. In one particular embodiment, for example, the nucleating agent may include a terpolymer of butanediol diglycidyl ether, ethylene oxide, and trioxane. The nucleating agent may be present in the composition in an amount of at least about 0.01 wt.%, for example, at least about 0.05 wt.%, for example, at least about 0.1 wt.%, and less than about 2 wt.%, for example, less than about 1.5 wt.%, for example, less than about 1 wt.%, where the weight is based on the total weight of each polymer composition.

[0061] In one embodiment, an antioxidant such as a sterically hindered phenol may 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)propionohydrazide], 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.%, 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.

[0062] In one embodiment, in addition to the ultraviolet light stabilizer, a light stabilizer, such as a sterically hindered amine, may be present. Usable hindered amine light stabilizers include N-methylated oligomeric hindered amine compounds. For example, the hindered amine light stabilizer may include a high molecular weight hindered amine stabilizer. Other light stabilizer embodiments include 2,2,6,6-tetramethyl-4-piperidyl compounds, such as bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, or polymers 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. When present, the light stabilizer may be present in the polymer composition in an amount of at least about 0.01 wt.%, for example at least about 0.05 wt.%, for example at least about 0.075 wt.%, and less than about 1 wt.%, for example less than about 0.75 wt.%, for example less than about 0.5 wt.%, where the weight is based on the total weight of the respective polymer composition.

[0063] In one embodiment, a lubricant may be present. The lubricant may include a polymer wax composition. Additionally, in one embodiment, a polyethylene glycol polymer (processing aid) may be present in the composition. The polyethylene glycol may have a molecular weight of, for example, about 1000 to about 5000, e.g., about 3000 to about 4000. In one embodiment, for example, PEG-75 may be present. In another embodiment, a fatty acid amide, e.g., ethylene bis(stearamide), may be present. The lubricant may generally be present in the polymer composition in an amount of at least about 0.01 wt.%, e.g., at least about 0.05 wt.%, e.g., at least about 0.075 wt.%, or less than about 1 wt.%, e.g., less than about 0.75 wt.%, e.g., less than about 0.5 wt.%, where the weight is based on the total weight of the respective polymer composition.

[0064] In one embodiment, a colorant may be present. Colorants that can be used include any desired inorganic pigment, such as titanium dioxide, ultramarine, cobalt blue, and other organic pigments, as well as dyes, such as phthalocyanines and anthraquinones. Other colorants include carbon black or various other soluble polymeric dyes. In one embodiment, a combination of colorants may be included in the polymer composition. For example, the polymer composition may contain titanium dioxide in combination with carbon black. In an alternative embodiment, the colorant present in the polymer composition may include titanium dioxide in combination with at least one colored pigment, such as a yellow pigment and a green pigment, optionally in combination with additional carbon black. The colorant may be present in the composition in an amount of at least about 0.01 wt.%, for example at least about 0.05 wt.%, for example at least about 0.1 wt.%, for example at least about 0.5 wt.%, for example at least about 0.8 wt.%, for example at least about 1 wt.%, and may also be present in an amount of 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.

[0065] Fillers that may be included in the composition include glass beads, wollastonite, loam, molybdenum disulfide or graphite, and / or inorganic or organic fibers.

[0066]

[0065] Reinforcing fibers that may be contained in the composition are mineral fibers, such as glass fibers, polymer fibers, in particular organic high-modulus fibers, such as aramid fibers, metal fibers, such as steel fibers, carbon fibers, natural fibers, and / or fibers from renewable resources.

[0067]

[0066] These fibers may be in modified or unmodified form, for example provided with a sizing agent or chemically treated to improve adhesion to the polymer. Glass fibers are particularly preferred.

[0068]

[0067] Glass fibers are provided with a sizing agent to protect the glass fibers, smooth the fibers, and also improve adhesion between the fibers and the matrix material. Sizing agents typically include silanes, film formers, lubricants, wetting agents, adhesives, and optionally antistatic agents, plasticizers, emulsifiers, and optionally further additives.

[0069]

[0068] Specific examples of silanes are aminosilanes, such as 3-trimethoxysilylpropylamine, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(3-trimethoxysilanylpropyl)ethane-1,2-diamine, 3-(2-aminoethyl-amino)propyltrimethoxysilane, and N-[3-(trimethoxysilyl)propyl]-1,2-ethane-diamine.

[0070]

[0069] Film-forming agents are, for example, polyvinyl acetate, polyesters and polyurethanes. Polyurethane-based sizing agents can be advantageously used. The reinforcing fibers may be incorporated into the polyoxymethylene matrix, for example, in an extruder or kneader. However, the reinforcing fibers may also advantageously take the form of continuous filament fibers coated or impregnated with the polyoxymethylene molding composition by a process suitable for this purpose, and then processed or wound up in the form of a continuous strand, or cut to the desired pellet length, so that the length of the fiber and the length of the pellet are identical. An example of a process particularly suitable for this purpose is the pultrusion process.

[0071]

[0071] The reinforcing fibres may be present in the moulding composition in an amount in the range 5 to 45 wt.%, for example 10 to 40 wt.%, where the weight is based on the total weight of the composition.

[0072] The polymer composition may further include an impact modifier, such as a thermoplastic elastomer. Thermoplastic elastomers are materials that have both thermoplastic and elastomeric properties. Thermoplastic elastomers include styrenic block copolymers, polyolefin blends known as thermoplastic olefin elastomers, elastomeric alloys, thermoplastic polyurethanes, thermoplastic copolyesters, and thermoplastic polyamides.

[0072]

[0073] Thermoplastic elastomers well suited for use in the present disclosure are polyester elastomers (TPE-E), thermoplastic polyamide elastomers (TPE-A), and especially thermoplastic polyurethane elastomers (TPE-U).

[0073]

[0074] In one specific embodiment, a thermoplastic polyurethane elastomer is used.The thermoplastic polyurethane elastomer may have, for example, a soft segment of a long-chain diol and a hard segment obtained from a diisocyanate and a chain extender.In one embodiment, the polyurethane elastomer is a polyester type, which is prepared by reacting a long-chain diol with a diisocyanate to produce a polyurethane prepolymer with an isocyanate terminal group, 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) glycol, poly(propylene oxide) glycol, poly(ethylene oxide) glycol, 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-(cyclohexyl isocyanate). Suitable chain extenders are C2-C6 aliphatic diols, such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol. An example of a thermoplastic polyurethane is one characterized essentially as poly(adipic acid-co-butylene glycol-co-diphenylmethane diisocyanate).

[0074]

[0075] The amount of thermoplastic elastomer included in the polymer composition can vary depending on various factors. For example, the thermoplastic elastomer may be present in an amount ranging from about 0.5% to about 50% by weight. In one embodiment, for example, the thermoplastic elastomer or impact modifier may be present in the composition in an amount less than about 25% by weight, such as less than about 15% by weight, or less than about 10% by weight. The thermoplastic elastomer or impact modifier is generally present in an amount greater than about 2% by weight, such as greater than about 5% by weight, such as greater than about 8% by weight, or greater than about 10% by weight.

[0075]

[0076] In one embodiment, when an impact modifier or a thermoplastic elastomer is present in the composition, the composition may also include a coupling agent. The coupling agent may include a polyisocyanate, such as a diisocyanate or triisocyanate. The coupling agent may generally be present in an amount of from about 0.1% to about 2% by weight, for example, from about 0.1% to about 1% by weight.

[0076]

[0077] The compositions of the present disclosure can be compounded or formed into polymeric articles using any technique known in the art. For example, the individual compositions can be intensively mixed to form a substantially homogeneous blend. The blend can be melt-mixed at elevated temperatures, e.g., above the melting point but below the decomposition temperature of the polymers utilized in the polymer composition. Alternatively, the individual compositions can be melted and mixed together in a conventional single or twin screw extruder. Preferably, melt mixing is carried out at a temperature ranging from 100 to 280°C, e.g., 120 to 260°C, e.g., 140 to 240°C, or 180 to 220°C.

[0077]

[0078] After extrusion, the composition may be formed into pellets, which can be formed into polymeric articles by techniques known in the art, such as injection molding, thermoforming, blow molding, rotational molding, and the like.

[0078]

[0079] The polymer compositions of the present disclosure can be used to produce a variety of molded parts. Such parts can be formed through any suitable molding process, such as an injection molding process, or a blow molding process. Polymer articles that can be made according to the present disclosure include, but are not limited to, knobs, door handles, decorative trim pieces for automobiles, and the like. For example, other polymer articles that can be made according to the present disclosure include latches, levers, gears, pivot housings, speaker grilles, and the like.

[0079]

[0080] For example, referring to Figure 1, an automobile interior is shown illustrating various automobile parts that can be made in accordance with the present disclosure. The polymer composition can be used to produce automobile part 10, for example, comprising 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 automobile part 12. In general, the polymer composition can be used to mold any suitable decorative trim piece or bevel, such as decorative piece 14.

[0080]

[0081] The compositions are also particularly well suited for use in producing medical products. For example, referring to Figure 2, an inhaler 20 is shown. The inhaler 20 includes a housing 22 attached to a mouthpiece 24. A plunger 26 for receiving a canister containing the composition to be inhaled is in operative association with the housing 22. The compositions may include sprays or powders.

[0081]

[0082] During use, the inhaler 20 administers a metered dose of a therapeutic agent, such as an asthma medication, to a patient. The asthma medication may be suspended or dissolved in a propellant or may be contained in a powder. When a patient activates the inhaler and inhales the therapeutic agent, a valve opens, allowing the therapeutic agent to exit the mouthpiece. In accordance with the present disclosure, the housing 22, mouthpiece 24, and plunger 26 may all be fabricated from the polymer compositions described above.

[0082]

[0083] Referring to FIG. 3, another medical product that can be made in accordance with the present disclosure is shown. In FIG. 3, a medical injector 30 is illustrated. The medical injector 30 includes a housing 32 operatively associated with a plunger 34. The housing 32 is slidable relative to the plunger 34. The medical injector 30 may also include a spring. The medical injector is typically for injecting medication into a patient's thigh or buttocks. The medical injector may be needleless or may contain a needle. If it contains a needle, the tip of the needle is typically hidden within the housing prior to injection. Alternatively, a needleless injector may contain a cylinder of pressurized gas that forces a therapeutic agent through the skin without the use of a needle. In accordance with the present disclosure, the housing 32 and / or plunger 34 may be made from the polymer compositions described above.

[0083]

[0084] Although the polyoxymethylene polymer compositions of the present disclosure and the polymer articles produced therefrom provide improved release characteristics, the compositions and articles may also exhibit excellent mechanical properties (ISO Test 527). For example, when tested according to ISO Test No. 527, the polymer compositions 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.

[0084]

[0085] The polymer composition has a capacitance of about 3 kJ / m 2 greater, e.g., about 6 kJ / m 2 The notched Charpy impact strength (ISO test 179-1) at 23°C may be greater than 20 kJ / m. 2 is less than.

[0085]

[0086] The present disclosure may be better understood with reference to the following examples. [Example]

[0086]

[0087] The following examples were carried out to demonstrate some of the advantages and benefits of polymer compositions made in accordance with the present disclosure.

[0087] Example 1

[0088] Various polymer compositions were compounded, molded into test specimens, and tested for formaldehyde emissions. The polymer compositions contained oxymethylene copolymers. The polyoxymethylene polymers were measured at approximately 9 cm per ISO test 1133. 3 In addition to the polyoxymethylene polymer, the polymer composition contained 0.25 wt. % of a nucleating agent (polyoxymethylene terpolymer), 0.2 wt. % of an antioxidant (unless otherwise specified, triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, 0.2 wt. % of ethylene bis(stearamide).

[0088]

[0089] Various different additives were then combined with the above polymer compositions and tested for formaldehyde emissions. Each formulation was compounded in a 32 mm co-rotating twin screw extruder (ZSK32, Coperion, Germany). Test plaques were injection molded. The test plaques were molded at a temperature of 205°C and dried at 140°C for 2 hours. The test plaques had a thickness of 1 mm.

[0089]

[0090] The samples were also tested according to Ford's 10 Liter Bag Method (hereinafter "10 Liter Bag Method"), test reference number BZ108-01 (July 2, 2018).

[0090]

[0091] In addition to the above-mentioned components, the tested polymer compositions also contained a formaldehyde stabilizer package. The formaldehyde stabilizer package contained tricalcium citrate in an amount of 0.05 wt % in combination with one or more release control agents. The formulations were tested for formaldehyde release according to the VDA275 test. The following table lists the release control agents present in the formulations and the formaldehyde release results.

[0091] [Table 1]

[0092] The substituted hydantoin is 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide), which is also believed to have coupling agent properties. MDI in the table above is methylene diphenyl diisocyanate, a known coupling agent. In Samples 4, 5, 10, and 11 above, the formulations contained two phenolic antioxidants. The first phenolic antioxidant was present in an amount of 0.15 wt. % and included triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate. The second phenolic antioxidant contained in the formulations was present in an amount of 0.05 wt. % and included N,N'-(hexane-1,6-diyl)bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide]. As shown above, formulations containing substituted hydantoins dramatically reduced formaldehyde emissions.

[0093] The formulations were also tested for formaldehyde emissions using the 10 liter bag method described above, with the following results:

[0094] [Table 2]

[0095] A formulation containing 0.05% copolyamide in addition to the other ingredients contained in the other formulations was also tested. Formaldehyde emission result was 5517 μg / m 3 It was. The formulations were also tested for color stability. Again, samples molded at a temperature of 205° C. were tested. The following results were obtained:

[0096] [Table 3]

[0097] The composition was also tested for melt flow rate at 190° C. and a load of 2.16 kg. The following results were obtained:

[0098] [Table 4]

[0099] Example 2 Example 1 was repeated using the same process and ingredients. The formulation was tested for formaldehyde emission in the VDA 75 test and for melt flow rate. The following results were obtained:

[0100] [Table 5]

[0101] The above formulations were also tested for color stability with the following results:

[0102] [Table 6]

[0103]

[0099] These and other modifications and variations to the present invention may be practiced by those skilled in the art without departing from the spirit and scope of the invention, as more particularly described in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those skilled in the art will appreciate that the foregoing description is by way of example only and is not intended to limit the invention, as further described in such appended claims. [Explanation of symbols]

[0104] 10, 12 Auto parts 14 decorative pieces 20 Inhaler 22 Housing 24 mouthpiece 26 Plunger 30 Medical Injector 32 Housing 34 Plunger

Claims

1. polyoxymethylene polymers; and Formaldehyde stabilizer package for reducing formaldehyde emissions A polymer composition comprising: The formaldehyde stabilizer package includes at least one release-controlling agent, the release-controlling agent comprising a substituted hydantoin alone or a combination of an aliphatic carboxylic acid hydrazide and a substituted hydantoin, wherein when present in combination, 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. 2. The polymer composition of claim 1, wherein the aliphatic carboxylic acid hydrazide is present in a weight ratio relative to the substituted hydantoin of about 1:1.5 to about 1:7.5, such as about 1:2 to about 1:5.

5.

3. 10. The polymer composition of claim 1, wherein the substituted hydantoin contains two hydrazinocarbonylalkyl groups.

4. 2. The polymer composition of claim 1, wherein the substituted hydantoin comprises 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide).

5. The polymer composition of any one of claims 1 to 4, wherein the aliphatic carboxylic acid hydrazide comprises sebacic acid dihydrazide, dodecanedioic acid dihydrazide, or a mixture thereof.

6. The polymer composition of any one of claims 1 to 5, wherein the aliphatic carboxylic acid hydrazide is present in the polymer composition in an amount less than about 0.15 wt%.

7. 7. The polymer composition of any one of claims 1 to 6, which exhibits a Yellowness Index of less than 0, such as less than about -1, such as less than about -2, for example less than about -3, and greater than about -10, when tested according to DIN 6167 at a moulding temperature of 205°C.

8. At a molding temperature of 205°C, the L is less than about 80, e.g., less than about 78, e.g., less than about 76, and greater than about 60, e.g., greater than about 70. ＊ The polymer composition according to any one of claims 1 to 7, wherein the polymer composition exhibits a value of 0.

05.

9. 9. The polymer composition of any one of claims 1 to 8, which exhibits formaldehyde emissions of less than about 1 ppm, such as less than about 0.8 ppm, for example less than about 0.6 ppm, for example less than about 0.4 ppm, when tested according to test VDA-275, at a thickness of 1 mm, at a moulding temperature of 205°C, after drying at 140°C for 2 hours.

10. The polymer composition of any one of claims 1 to 9, wherein the polymer composition further comprises an acid scavenger, the acid scavenger comprising a metal salt of an organic acid.

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

12. The polymer composition of claim 10, wherein the acid scavenger comprises tricalcium citrate.

13. 13. The polymer composition of 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 less than about 0.2 wt%, such as less than about 0.08 wt%, and in an amount greater than about 0.001 wt%.

14. Approximately 100 μg / m when tested according to the 10 liter bag test ３ less than about 80 μg / m ３ less than about 60 μg / m ３ less than about 55 μg / m ３ 14. The polymer composition of any one of claims 1 to 13, exhibiting a formaldehyde emission of less than 1000 ppm.

15. 15. The polymer composition of any one of claims 1 to 14, wherein the substituted hydantoin is present in the polymer composition in an amount greater than about 0.05 wt%, such as greater than about 0.07 wt%, for example greater than about 0.15 wt%, such as greater than about 0.2 wt%, for example greater than about 0.22 wt%, and less than about 0.5 wt%.

16. When the polyoxymethylene polymer is tested at 190° C. and a load of 2.16 kg, it has a thickness of about 5 cm ３ / 10 minutes to approx. 15cm ３ 16. The polymer composition according to claim 1, having a melt flow rate of 1 / 10 min.

17. 17. The polymer composition of any one of claims 1 to 16, further comprising a nucleating agent in an amount of about 0.05% to about 1% by weight, a phenolic antioxidant in an amount of about 0.05% to about 2% by weight, and a lubricant in an amount of about 0.05% to about 1.5% by weight.

18. The polymer composition of any one of claims 1 to 17, further comprising a thermoplastic elastomer in an amount of about 5% to about 30% by weight.

19. The polymer composition of any one of claims 1 to 18, further comprising reinforcing fibers in an amount of from about 3% to about 40% by weight.

20. The polymer composition of any one of claims 1 to 19, further comprising a UV stabilizer.

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

22. 22. The polymer composition of claim 21, wherein the acid scavenger comprises tricalcium citrate.

23. 22. The polymer composition of claim 21, wherein the aliphatic carboxylic acid hydrazide is present in a weight ratio relative to the substituted hydantoin of about 1:1.5 to about 1:7.5, such as about 1:2 to about 1:5.

5.

24. 22. The polymer composition of claim 21, wherein the aliphatic carboxylic acid hydrazide comprises a dihydrazide.

25. 22. The polymer composition of claim 21, wherein the substituted hydantoin comprises 4-isopropyl-2,5-dioxoimidazolidine-1,3-di(propionohydrazide).

26. 22. The polymer composition of claim 21, wherein the aliphatic carboxylic acid hydrazide comprises sebacic acid dihydrazide, dodecanedioic acid dihydrazide, or a mixture thereof.

27. 27. The polymer composition of any one of claims 21 to 26, wherein the aliphatic carboxylic acid hydrazide is present in the polymer composition in an amount less than about 0.15 wt%.

28. polyoxymethylene polymers; Formaldehyde stabilizer package for reducing formaldehyde emissions 1. A polymer composition comprising: The formaldehyde stabilizer package includes at least one release-controlling agent, the release-controlling agent including a substituted hydantoin alone or a combination of an aliphatic carboxylic acid hydrazide and a substituted hydantoin, the substituted hydantoin containing two hydrazinocarbonyl alkyl groups; The polymer composition exhibits a yellowness index of less than -1 and greater than about -10 when tested according to DIN 6167 at a molding temperature of 205°C, and an L of less than about 80 and greater than about 60 at a molding temperature of 205°C. ＊ values ​​and exhibits formaldehyde emissions of less than about 1 ppm when tested according to test VDA-275 after drying at 140°C for 2 hours at a thickness of 1 mm and a mold temperature of 205°C, and about 80 μg / m when tested according to the 10 liter bag test. ３ The polymer composition exhibits formaldehyde emissions of less than 1000 ppm.

29. A shaped article made from the polymer composition of any one of claims 1 to 28.

30. 30. The molded article of claim 29, comprising an interior automotive part.

31. 30. The molded article of claim 29, comprising a latch, a lever, a gear, a pivot housing, a speaker grill, a door handle, a decorative trim piece, a bracket, or a seat rail.

32. 30. The shaped article of claim 29, comprising an inhaler or injector.

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