Low emission polyoxymethylene composition

Abstract

A polyoxymethylene polymer composition containing a formaldehyde stabilizer package is disclosed. In one embodiment, the formaldehyde stabilizer comprises a substituted hydantoin, it has been found that the substituted hydantoin alone or a combination of a substituted hydantoin with another emission control agent significantly reduces formaldehyde emissions. When the polymer composition does not contain calcium stearate, the formaldehyde emission is low.

Description

Background Technology

[0001] Polyacetal polymers (commonly known as polyoxymethylene) have been recognized as extremely useful engineering materials in a wide range of applications. For example, polyoxymethylene polymers are widely used to construct molded parts, such as those used in the automotive and electrical industries. Polyoxymethylene polymers also exhibit excellent mechanical properties, fatigue resistance, abrasion resistance, chemical resistance, and moldability.

[0002] While polyacetal resins possess many useful properties, the polymers tend to degrade upon heating and are inherently unstable in oxidizing atmospheres or in acidic or alkaline environments. In particular, polyacetal resins have a tendency to release formaldehyde during processing and after the polymer is molded into parts. Formaldehyde is not only a pollutant but can also adversely affect metal parts that may be placed in contact with the polymer. For example, formaldehyde readily oxidizes into formic acid, which can corrode metals or cause discoloration.

[0003] In light of the above, those skilled in the art have explored combining polyacetal polymers with various compounds to reduce formaldehyde emissions. For example, in the past, polyacetal polymers have been combined with melamine to achieve lower formaldehyde emission performance. Furthermore, various other chemical compounds have been proposed for reducing formaldehyde emissions.

[0004] While various compounds used in the past have successfully reduced formaldehyde emissions from products made from polyoxymethylene polymers, further improvements in formaldehyde emission control are still needed. For example, stricter government regulations continue to require further improvements in reducing formaldehyde emissions.

[0005] In view of the above, there is a need for improved formaldehyde stabilizer packages that can further reduce formaldehyde emissions. Summary of the Invention

[0006] In general, this disclosure relates to a polymer composition primarily comprising a polyacetal resin and molded products prepared from the composition. The polymer composition of this disclosure is specifically formulated to exhibit ultra-low formaldehyde emissions. For example, when tested according to the VDA 275 test, the polyacetal polymer composition formulated according to this disclosure can exhibit formaldehyde emissions of less than about 2 ppm, for example, less than about 1 ppm. The VDA 275 test (German Automotive Industry Recommendation No. 275) was recorded by Kraftfahrwesen e.V. in July 1994. Unless otherwise specified, the test is performed on a sample with a thickness of 1 mm (40 mm × 100 mm), and formaldehyde emissions are tested 24 hours after extraction.

[0007] In one embodiment, for example, the polymer composition of this disclosure comprises a combination of a polyoxymethylene polymer and a formaldehyde stabilizer package for reducing formaldehyde emissions. In one embodiment, the formaldehyde stabilizer package may contain at least one emission control agent. In particular, certain substituted hydantoin has been found to be very effective in reducing formaldehyde emissions. The substituted hydantoin can be used in combination with other hydrazides and / or other emission control agents. Molded articles prepared according to this disclosure also exhibit very stable color quality, making the polymer composition ideal for the production of automotive interior trim parts, etc.

[0008] In one embodiment, for example, this disclosure relates to a polyoxymethylene polymer in combination with a formaldehyde stabilizer package, the formaldehyde stabilizer package comprising a combination of a substituted hydantoin and one or more aliphatic carboxylic acid hydrazides. The weight ratio between the aliphatic carboxylic acid hydrazide and the substituted hydantoin can be from about 1:20 to about 10:1, for example from about 1:8 to about 2:1, for example from about 1:4 to about 1.25:1.

[0009] The substituted hydantoin may be present in the polymer composition in amounts less than about 3% by weight, for example less than about 2% by weight, for example less than about 1% by weight, for example less than about 0.8% by weight, for example less than about 0.5% by weight, and generally in amounts greater than about 0.01% by weight, for example greater than about 0.03% by weight, for example greater than about 0.05% by weight, for example greater than about 0.09% by weight, for example greater than about 0.1% by weight, for example greater than about 0.12% by weight, for example greater than about 0.15% by weight, for example greater than about 0.17% by weight, for example greater than about 0.2% by weight. The substituted hydantoin may contain two hydrazyl carbonyl alkyl groups. The substituted hydantoin may have a melting point 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 can 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 specific embodiment, the substituted hydantoin comprises 4-isopropyl-2,5-dioxoimidazolidine-1,3-bis(propionylhydrazine).

[0010] As described above, the substituted hydantoin can be combined with aliphatic carboxylic acid hydrazides. The aliphatic carboxylic acid hydrazides can be dihydrazides. Examples of dihydrazides include sebacic acid dihydrazides, dodecanoic acid dihydrazides, or mixtures thereof. In one aspect, one or more aliphatic carboxylic acid hydrazides may be present in the polymer composition in an amount greater than about 0.01% by weight, for example, greater than about 0.02% by weight, for example, greater than about 0.03% by weight, for example, greater than about 0.04% by weight, and in an amount less than about 3% by weight, for example, less than about 2% by weight, for example, less than about 1% by weight, for example, less than about 0.6% by weight, for example, less than about 0.4% by weight, for example, less than about 0.1% by weight.

[0011] Other optional components that may be included in the polymer composition include 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. For example, the nucleating agent may include a polyoxymethylene terpolymer. The polymer composition may also optionally contain a thermoplastic elastomer, reinforcing fibers, and / or a UV stabilizer.

[0012] The formaldehyde emission performance of molded articles prepared from polymer compositions depends to some extent on the molding temperature. The formaldehyde stabilizer package of this disclosure has been found to perform well at all molding temperatures, which is unexpected given the formaldehyde stabilizer packages used in the past. For example, at a thickness of 1 mm, a molding temperature of 205°C, and after drying at 140°C for 2 hours, the polymer composition can exhibit formaldehyde emissions of less than about 20 ppm, for example, less than about 15 ppm, for example, less than about 10 ppm, for example, less than about 5 ppm, according to test VDA-275. At a molding temperature of 195°C, the polymer composition can exhibit formaldehyde emissions of less than about 15 ppm, for example, less than about 10 ppm, for example, less than about 3 ppm. At a molding temperature of 185°C, the polymer composition can exhibit formaldehyde emissions of less than about 8 ppm, for example, less than about 5 ppm, for example, less than about 3 ppm, for example, less than about 2 ppm, for example, less than about 1 ppm.

[0013] The polymer composition can also be tested for formaldehyde emissions according to a 10-liter bag test. For example, when tested according to a 10-liter bag test at a molding temperature of 195°C and after drying at 140°C for 2 hours, the polymer composition prepared according to this disclosure can show less than about 300 µg / m³. 3 For example, less than about 250 µg / m 3 For example, less than about 200 µg / m 3 For example, less than about 150 µg / m 3Formaldehyde emissions. At a molding temperature of 205°C, the polymer composition can exhibit less than about 10,000 µg / m³. 3 For example, less than about 5,000 µg / m 3 For example, less than about 1,000 µg / m 3 For example, less than about 750 µg / m 3 Formaldehyde emissions. Test samples can have a thickness of 1 mm and a mass of 26 g. For example, a single sample with a size of 100 mm × 200 mm can be tested, or multiple samples with the same surface area can be tested together (e.g., two samples with a size of 100 mm × 100 mm or five samples with a size of 40 mm × 100 mm), where the mass is constant at 26 g.

[0014] It has been found that lower formaldehyde emission levels can be achieved when the polymer composition does not contain any alkaline earth metal salts of aliphatic carboxylic acids, as taught in U.S. Patent No. 11,555,111, which is incorporated herein by reference. For example, the polymer composition may be free of calcium stearate and / or calcium 12-hydroxystearate. Given this '111 patent, the formaldehyde emission levels achieved with the polymer compositions disclosed herein are surprising and unexpected.

[0015] All types of molded articles can be prepared from polymer compositions containing a formaldehyde stabilizer packet according to this disclosure. For example, molded articles may include automotive interior parts. Molded articles may include latches, levers, gears, pivot housings, speaker grilles, door handles, decorative trim pieces, brackets, seat rails, etc. Medical products may also be prepared from polymer compositions, such as components of inhalers or syringes.

[0016] Other features and aspects of this disclosure are discussed in more detail below. Attached Figure Description

[0017] The full and implementation disclosure of this disclosure is set forth in more detail in the remainder of the specification, including with reference to the accompanying drawings, wherein:

[0018] Figure 1 It is a perspective view of the interior of a car, showing various molded articles that can be manufactured according to this disclosure;

[0019] Figure 2 It is a perspective view of a medical inhaler that can be manufactured from a molded part according to this disclosure; and

[0020] Figure 3 It is a perspective view of a medical syringe containing a molded part manufactured according to this disclosure.

[0021] In this specification and the accompanying drawings, reference numerals are used repeatedly to indicate the same or similar features or elements of the invention. Detailed Implementation

[0022] Those skilled in the art will understand that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this disclosure.

[0023] In general, this disclosure relates to a polymer composition exhibiting low formaldehyde emissions, comprising a polyacetal resin, particularly a polyoxymethylene copolymer. This polymer composition is ideally suited for molding processes used to produce molded articles. The polymer composition may contain one or more colorants for producing molded articles with any desired color. The molded articles can be used in an infinite number of different applications and fields. In one embodiment, for example, the molded article can be prepared according to this disclosure and designed to serve as an automotive part, such as an automotive part designed for use inside a vehicle (e.g., a car or truck).

[0024] More specifically, this disclosure relates to a polymer composition comprising a combination of a polyacetal resin and a formaldehyde stabilizer package. The formaldehyde stabilizer package contains at least one emission control agent. In particular, substituted hydantoin (optionally in combination with other hydrazides) with specific properties has been found to be a very effective emission control agent. Furthermore, it has been found that formaldehyde emissions are significantly and surprisingly low when the polymer composition is formulated to contain various alkaline earth metal salts that do not contain aliphatic carboxylic acids. For example, it has been found that formaldehyde emissions are significantly lower when the composition does not contain calcium salts of carboxylic acids (e.g., calcium stearate, including calcium 12-hydroxystearate). Optionally, the polymer composition may be formulated to contain metal salts that do not contain any organic acids (e.g., calcium citrate, including tricalcium citrate).

[0025] In one aspect, the substituted hydantoin contains two hydrazyl carbonyl alkyl groups. In another aspect, the specific substituted hydantoin used for incorporation into a polymer composition may have a relatively low melting point and a relatively low curing temperature. For example, the melting point of the substituted hydantoin may be 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, for example less than about 122°C. The melting point may be greater than about 100°C, for example greater than about 110°C, for example greater than about 115°C, for example greater than about 118°C. The substituted hydantoin may be configured to cure at a temperature less than about 125°C, for example less than about 120°C, for example less than about 115°C, for example less than about 112°C, and generally greater than about 100°C, for example greater than about 105°C (after exposure to the above temperatures for one hour).

[0026] In one specific embodiment, the substituted hydantoin may include 4-isopropyl-2,5-dioxoimidazolidine-1,3-bis(propionylhydrazine).

[0027] In the past, it has been proposed to use hydantoin compounds having two hydrazinocarbonyl alkyl groups in polyacetal resin compositions to reduce formaldehyde generation in molded articles. For example, U.S. Patent No. 11,555,111 relates to polyacetal resin compositions and is incorporated herein by reference. However, in stark contrast to the polymer compositions prepared according to this disclosure, the '111 patent discloses polyacetal resin compositions that must contain an alkaline earth metal salt of an aliphatic carboxylic acid (e.g., calcium stearate or 12-hydroxystearate). However, it has been found that by formulating compositions that do not contain calcium stearate, 12-hydroxystearate, or other alkaline earth metal salts of aliphatic carboxylic acids, formaldehyde emissions can actually be reduced. This result is unexpected from the perspective of the '111 patent.

[0028] In one embodiment, the formaldehyde stabilizer package of the present invention may contain a combination of a substituted hydantoin emission control agent and one or more aliphatic carboxylic acid hydrazides. For example, the substituted hydantoin emission control agent may contain two hydrazinocarbonyl alkyl groups. In one aspect, the substituted hydantoin comprises 4-isopropyl-2,5-dioxoimidazolidine-1,3-bis(propionylhydrazine). The aliphatic carboxylic acid hydrazide may be a diacylhydrazine. Specific examples of diacylhydrazides include, for example, sebacate diacylhydrazine, dodecanoic acid diacylhydrazine, or mixtures thereof.

[0029] In one aspect, one or more aliphatic carboxylic acid hydrazides may be present relative to the substituted hydantoin at a weight ratio of about 1:20 to about 10:1, for example about 1:8 to about 2:1, for example about 1:4 to about 1.25:1. Although the weight ratio may vary depending on the specific application, the above weight ratios have been found to be particularly effective in reducing formaldehyde emissions, making molded articles particularly suitable for the production of trim parts for vehicle (e.g., automobile) interiors or for the production of parts for consumer home appliances.

[0030] One or more aliphatic carboxylic acid hydrazides are typically present in the polymer composition in amounts from about 0.001% by weight to about 3% by weight (including all increments of 0.1% by weight therein). In one aspect, one or more aliphatic carboxylic acid hydrazides are present in the polymer composition in smaller amounts (e.g., less than about 0.2% by weight, for example, less than about 0.15% by weight, for example, less than about 0.12% by weight, for example, less than about 0.1% by weight, for example, less than about 0.09% by weight, for example, less than about 0.08% by weight). Minimizing the amount of aliphatic carboxylic acid hydrazides present in the composition can provide various advantages and benefits, including minimizing free hydrazides in the composition and providing color stability.

[0031] The amount of 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. Typically, the substituted hydantoin can be present in the polymer composition in an amount from about 0.0001% by weight to about 4% by weight (including all increments of 0.01% by weight therebetween). In one embodiment, the substituted hydantoin is present in the polymer composition in an amount greater than that of any other emission control agent present in the composition. In various embodiments, the substituted hydantoin can be present in the polymer composition in an amount greater than 0.03% by weight, for example, greater than about 0.04% by weight, for example, greater than about 0.1% by weight, for example, greater than about 0.12% by weight, for example, greater than about 0.15% by weight, for example, greater than about 0.17% by weight, for example, greater than about 0.2% by weight, for example, greater than about 0.22% by weight, for example, greater than about 0.24% by weight. In various embodiments, the substituted hydantoin may be present in the polymer composition in an amount of less than about 0.8% by weight, for example, less than about 0.6% by weight, for example, less than about 0.55% by weight, for example, less than about 0.5% by weight, for example, less than about 0.45% by weight, for example, less than about 0.4% by weight, for example, less than about 0.35% by weight, for example, less than about 0.3% by weight.

[0032] In one embodiment, the formaldehyde stabilizer package includes the aforementioned emission control agent while excluding other formaldehyde scavengers previously used. For example, the polymer composition can be formulated to be melamine-free. In fact, the polymer composition can be formulated to be free of any melamine or any melamine derivatives. In one aspect, the polymer composition does not contain any guanidine compounds.

[0033] Other emission control agents that may be present in formaldehyde stabilizer packages include amino acids (e.g., arginine) or alkylene ureas (e.g., ethylene urea). Additional emission control agents may typically be present in the polymer composition in amounts from about 0.01% by weight to about 0.5% by weight (including all increments of 0.01% by weight therebetween).

[0034] When combined with polyoxymethylene polymers, the formaldehyde stabilizer package of this disclosure as described above can produce polymer compositions and molded articles that not only have low formaldehyde emission performance, but also excellent mechanical properties and visual appeal.

[0035] For example, in one embodiment, according to VDA 275, the polymer composition containing the polyoxymethylene polymer exhibits formaldehyde emissions of less than about 3 ppm, for example less than about 2 ppm (μg / g), for example less than about 1.5 ppm, for example less than about 1 ppm, for example less than about 0.8 ppm. In one aspect, a sample (1 mm thick) can be molded at 185°C and the test can be run after the resin used to produce the test sample has been dried at 140°C for two hours. During the test, the sample is extracted in water at 60°C for 3 hours as specified in the test procedure. The released formaldehyde can be measured 24 hours or 7 days after extraction.

[0036] When the polymer composition is dried at 140°C for 2 hours and molded at 195°C, according to VDA 275, a test sample with a thickness of 1 mm can show formaldehyde emissions of less than about 15 ppm, for example, less than about 10 ppm, for example, less than about 5 ppm, for example, less than about 3 ppm, for example, less than about 2 ppm. When the polymer composition is dried at 140°C for 2 hours and molded at 205°C, according to VDA 275, a test sample with a thickness of 1 mm can show formaldehyde emissions of less than about 20 ppm, for example, less than about 15 ppm, for example, less than about 10 ppm, for example, less than about 5 ppm, for example, less than about 4 ppm.

[0037] Another formaldehyde emission test is the 10-liter bag test (using a 1mm, approximately 26g VDA test piece). The 10-liter bag test can be performed on a 26g sample consisting of one or more pieces: (one or more pieces) 1mm thick with a total surface area of ​​100mm × 200mm on one side. The polymer compositions prepared according to this disclosure can show less than approximately 300 μg / m³ when tested according to the 10-liter bag test. 3 For example, less than about 250 μg / m 3 For example, less than about 200 μg / m 3 For example, less than about 150 μg / m 3 Formaldehyde emissions. The 10-liter bag test can be performed on a molded sample at a temperature of 195°C.

[0038] The 10-liter bag test can be performed on a molded sample at 205°C, and the polymer composition prepared according to this disclosure can exhibit less than about 10,000 μg / m³. 3 For example, less than about 5,000 μg / m 3 For example, less than about 1,000 μg / m 3 For example, less than about 750 μg / m 3 Formaldehyde emissions.

[0039] The formaldehyde stabilizer package disclosed herein is specifically formulated in combination with polyoxymethylene polymers.

[0040] Typically, any suitable polyoxymethylene polymer can be incorporated into the polymer composition.

[0041] The preparation of polyoxymethylene polymers can be carried out by polymerizing monomers that form polyoxymethylene (e.g., trioxane or a mixture of trioxane and cycloacetals (e.g., dioxol)) in the presence of a molecular weight regulator (e.g., glycol). The polyoxymethylene polymer used in polymer compositions can comprise homopolymers or copolymers. According to one embodiment, polyoxymethylene is a homopolymer or copolymer containing at least 50 mol.%, for example at least 75 mol.%, for example at least 90 mol.%, and for example even at least 97 mol.%, -CH2O- repeating units.

[0042] In one embodiment, a polyoxymethylene copolymer is used. The copolymer may contain about 0.01 mol.% to about 20 mol.%, particularly about 0.5 mol.% to about 10 mol.%, of repeating units comprising a saturated or olefinically unsaturated alkylene group having at least two carbon atoms, or a cycloalkylene group having a sulfur or oxygen atom in the chain, and may include one or more substituents selected from alkyl, cycloalkyl, aryl, aralkyl, heteroaryl, halogen, or alkoxy groups. In one embodiment, a cyclic ether or acetal is used, which may be introduced into the copolymer via a ring-opening reaction.

[0043] Preferred cyclic ethers or acetals are those having the following formula:

[0044]

[0045] Where x is 0 or 1, R 2The C2-C4 alkylene group, where appropriate, has one or more substituents, which are C1-C4 alkyl groups or C1-C4 alkoxy groups, and / or halogen atoms, preferably chlorine atoms. Examples only include ethylene oxide, 1,2-epoxypropane, 1,2-epoxybutane, 1,3-epoxybutane, 1,3-dioxane, 1,3-dioxane, and 1,3-dioxane-heptane as cyclic ethers, and linear oligomers or polyformaldehydes (e.g., polydioxane- or polydioxane-heptane) as comonomers. Copolymers consisting of 99.5 mol.% to 95 mol.% trioxane and 0.01 mol.% to 5 mol.% (e.g., 0.5 mol.% to 4 mol.%) of one of the above comonomers are particularly advantageous. In one embodiment, the polyoxymethylene polymer contains a relatively low amount of comonomer. For example, the comonomer may be present in amounts less than about 2 mol.%, for example less than about 1.5 mol.%, for example less than about 1 mol.%, for example less than about 0.8 mol.%, for example less than about 0.6 mol.%.

[0046] Polymerization can be carried out as precipitation polymerization or in the melt. For example, polyoxymethylene copolymers can be formed by solution hydrolysis, in which precipitates or powders with very few unstable end groups are formed. By appropriately selecting polymerization parameters, such as polymerization duration 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 controlled.

[0047] In one embodiment, the polyoxymethylene polymer used in the polymer composition may contain a relatively high amount of reactive groups or functional groups at the terminal positions. For example, the reactive groups may include -OH or -NH2 groups.

[0048] In one embodiment, the polyoxymethylene polymer may have terminal hydroxyl groups, such as hydroxyethylidene groups and / or hydroxyl side groups, in at least more than 50% of all terminal sites on the polymer. For example, based on the total number of terminal groups present, at least about 70%, for example at least about 80%, for example 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.

[0049] In one embodiment, the polyoxymethylene polymer has a content of at least 15 mmol / kg, for example, at least 18 mmol / kg, for example, at least 20 mmol / kg of terminal hydroxyl groups. In another embodiment, the content of terminal hydroxyl groups 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, for example, less than 18 mmol / kg, for example, 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, for example, from about 5 mmol / kg to about 15 mmol / kg. For example, a polyoxymethylene polymer having a lower content of terminal hydroxyl groups but a higher melt flow rate can be used.

[0050] In addition to or in place of terminal hydroxyl groups, polyoxymethylene polymers may also have other terminal groups commonly used in these polymers. Examples of these groups are alkoxy groups, formate groups, acetate groups, or aldehyde groups. According to one embodiment, polyoxymethylene is a homopolymer or copolymer containing at least 50 mol%, for example at least 75 mol%, for example at least 90 mol%, and for example even at least 95 mol% of -CH2O- repeating units.

[0051] 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 cationic polymerization, glycols (e.g., ethylene glycol) or methyl acetal can be used as chain terminators. Heteropolyacids, trifluoromethanesulfonic acid, or boron compounds can be used as catalysts.

[0052] Polyoxymethylene polymers can have any suitable molecular weight. The molecular weight of the polymer can be, for example, 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, for example from about 20,000 g / mol to about 100,000 g / mol.

[0053] The polyoxymethylene polymer present in the composition typically has a viscosity of approximately 0.1 cm⁻¹, as determined according to ISO 1133 at 190°C and 2.16 kg. 3 / 10min to approximately 80cm 3 Melt flow index (MFI) of approximately 5 cm⁻¹ / 10 min. In one embodiment, the polyoxymethylene polymer may have a melt flow index of approximately 5 cm⁻¹ / 10 min. 3 / 10 min to approximately 15cm 3 / 10min, for example, about 8cm 3 / 10min to approximately 12cm 3The melt flow index is 1 / 10 min. In an alternative embodiment, a polyoxymethylene polymer with a relatively high melt flow index can be used. For example, the polyoxymethylene polymer can have a melt flow index of approximately 18 cm⁻¹. 3 / 10min to approximately 40cm 3 / 10min, for example, about 20cm 3 / 10min to approximately 35cm 3 Melt flow index per 10 minutes.

[0054] Suitable commercially available polyoxymethylene polymers are available under Celanese’s trademark name Hostaform® (HF).

[0055] The polyoxymethylene polymer may be present in the polyoxymethylene polymer composition in an amount of at least 50 wt.%, for example, at least 60 wt.%, for example, at least 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.%. Typically, 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.

[0056] The polymer compositions disclosed herein may also contain other known additives, such as antioxidants, UV stabilizers or heat stabilizers, impact modifiers and / or reinforcing fibers. Furthermore, the compositions may contain processing aids, such as tackifiers, lubricants, nucleating agents, release agents, fillers or antistatic agents, and additives that impart desired properties to the composition and articles or parts made therefrom.

[0057] In one embodiment, a UV stabilizer may be present. The UV stabilizer may include benzophenone, benzotriazole, or benzoate. When present, the UV 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.

[0058] In one embodiment, a nucleating agent may be present. The nucleating agent can increase crystallinity and may comprise a formaldehyde terpolymer. In one 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 amounts of at least about 0.01 wt.%, for example, at least about 0.05 wt.%, for example, at least about 0.1 wt.%, and less than about 2 wt.%, for example, less than about 1.5 wt.%, for example, less than about 1 wt.%, where the weight is based on the total weight of the respective polymer composition.

[0059] In one embodiment, an antioxidant, such as a sterically hindered phenol, may be present. Commercially available examples include 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)propionylhydrazine], and hexamethylene glycol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The antioxidant may be present in the polymer composition in amounts 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, in addition to the UV light stabilizer, a light stabilizer, such as a sterically hindered amine, may also be present. Suitable sterically hindered amine light stabilizers include N-methylated oligomeric hindered amine compounds. For example, sterically hindered amine light stabilizers may include high molecular weight sterically hindered amine stabilizers. Other embodiments of the light stabilizer include 2,2,6,6-tetramethyl-4-piperidinyl compounds, such as polymers of di(2,2,6,6-tetramethyl-4-piperidinyl) sebacate or dimethyl succinate with 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.%, wherein the weight is based on the total weight of the respective polymer composition.

[0061] 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, for example, have a molecular weight of about 1000 to about 5000, or, for example, about 3000 to about 4000. In one embodiment, for example, PEG-75 may be present. In another embodiment, a fatty acid amide, such as ethylene bis(stearamide), may be present. The lubricant may typically 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.

[0062] 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 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 contain a combination of titanium dioxide and carbon black. In an alternative embodiment, the colorant present in the polymer composition may comprise a combination of titanium dioxide and at least one colored pigment (e.g., yellow and green pigments), and optionally further combined with 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 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.

[0063] Fillers that may be included in the composition include glass beads, wollastonite, loam, molybdenum disulfide or graphite, and / or inorganic or organic fibers.

[0064] The reinforcing fibers that may be included in the composition are mineral fibers (e.g., glass fibers), polymer fibers (especially organic high-modulus fibers, such as aramid fibers), metal fibers (e.g., steel fibers), carbon fibers, natural fibers, and / or fibers derived from renewable resources.

[0065] These fibers can be in modified or unmodified forms, such as those formulated with sizing agents or chemically treated to improve adhesion to polymers. Glass fibers are particularly preferred.

[0066] Glass fibers are sized with sizing agents to protect the fibers, smooth them, and improve adhesion between the fibers and the matrix material. Sizing agents typically include silanes, film-forming agents, lubricants, wetting agents, adhesives, optional antistatic agents and plasticizers, emulsifiers, and other optional additives.

[0067] Specific examples of silanes are aminosilanes, such as 3-trimethoxysilylpropylamine, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(3-trimethoxysilylpropyl)ethane-1,2-diamine, 3-(2-aminoethyl-amino)propyltrimethoxysilane, and N-[3-(trimethoxysilyl)propyl]-1,2-ethane-diamine.

[0068] For example, film-forming agents are polyvinyl acetate, polyester, and polyurethane. Polyurethane-based sizing agents can be used advantageously.

[0069] The reinforcing fibers can be compounded into the polyoxymethylene matrix, for example, in an extruder or kneader. However, in a suitable process, the reinforcing fibers can also advantageously be in the form of continuous filament fibers coated or impregnated with a polyoxymethylene molding composition, which are then processed or wound as continuous tows, or cut to the desired pellet lengths such that the fiber length and pellet length are the same. An example of a process particularly suitable for this purpose is the pultrusion molding process.

[0070] The reinforcing fibers may 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.

[0071] The polymer composition may also contain impact modifiers, such as thermoplastic elastomers. Thermoplastic elastomers are materials that possess both 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.

[0072] The thermoplastic elastomers well suited for use in this disclosure are polyester elastomers (TPE-E), thermoplastic polyamide elastomers (TPE-A), and, in particular, thermoplastic polyurethane elastomers (TPE-U).

[0073] In one specific embodiment, a thermoplastic polyurethane elastomer is used. For example, the thermoplastic polyurethane elastomer may have flexible segments of a long-chain diol and hard segments derived from diisocyanates, along with a chain extender. In one embodiment, the polyurethane elastomer is polyester-type, prepared by reacting a long-chain diol with a diisocyanate to produce a polyurethane prepolymer with isocyanate end groups, followed by chain extension of the prepolymer with a diol chain extender. Representative long-chain diols are polyester diols, such as poly(butene 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(phenylisocyanate), 2,4-toluene diisocyanate, 1,6-hexamethylene diisocyanate, and 4,4'-methylenebis(epoxyisocyanate). 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 has been characterized as essentially poly(adipic acid-co-butanediol-co-diphenylmethane diisocyanate).

[0074] The amount of thermoplastic elastomer included in the polymer composition can vary depending on various factors. For example, the thermoplastic elastomer can be present in an amount from about 0.5% by weight to about 50% by weight. In one embodiment, for example, the thermoplastic elastomer or impact modifier can be present in the composition in an amount less than about 25% by weight, for example, less than about 15% by weight, for example, less than about 10% by weight. The thermoplastic elastomer or impact modifier is typically present in an amount greater than about 2% by weight, for example, greater than about 5% by weight, for example, greater than about 8% by weight, for example, greater than about 10% by weight.

[0075] In one embodiment, when an impact modifier or thermoplastic elastomer is present in the composition, the composition may also contain a coupling agent. The coupling agent may include a polyisocyanate, such as a diisocyanate or a triisocyanate. The coupling agent is typically present in amounts from about 0.1% by weight to about 2% by weight, for example, from about 0.1% by weight to about 1% by weight.

[0076] As described above, the composition can also be formulated to contain various alkaline earth metal salts that do not contain aliphatic carboxylic acids. For example, in one embodiment, the polymer composition and the molded article prepared from the composition may be free of calcium stearate and / or 12-hydroxystearate. Optionally, the polymer composition may also be free of other metal salts of carboxylic acids, such as calcium citrate (including tricalcium citrate). However, in one aspect, a small amount of calcium citrate may be present, for example, in an amount from about 0.001% by weight to about 0.4% by weight.

[0077] The compositions disclosed herein can be formulated and formed into polymer articles using any technique known in the art. For example, the respective compositions can be vigorously mixed to form a substantially homogeneous blend. The blend can be melt-kneaded at elevated temperatures (e.g., above the melting point of the polymer used in the polymer composition but below the degradation temperature). Alternatively, the respective compositions can be melt-mixed together in a conventional single-screw or twin-screw extruder. Preferably, melt mixing is carried out at temperatures of 100°C to 280°C, for example 120°C to 260°C, for example 140°C to 240°C, or 180°C to 220°C.

[0078] After extrusion, the composition can be formed into granules. The granules can be molded into polymer articles using techniques known in the art, such as injection molding, thermoforming, blow molding, rotational molding, etc.

[0079] The polymer compositions disclosed herein can be used to produce a variety of molded parts. These parts can be formed by any suitable molding process, such as injection molding or blow molding. Polymer articles that can be prepared according to this disclosure include, but are not limited to, knobs, door handles, automotive decorative trim parts, etc. Other polymer articles that can be manufactured according to this disclosure include, for example, latches, levers, gears, pivot housings, speaker grilles, etc.

[0080] For example, refer to Figure 1 The image shows the interior of a car, illustrating various automotive parts that can be manufactured according to this 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 the steering column, such as automotive part 12. Generally, the polymer composition can be used to mold any suitable decorative trim or border, such as trim piece 14.

[0081] This composition is also particularly suitable for the manufacture of medical products. For example, see reference. Figure 2 The image shows an inhaler 20. The inhaler 20 includes a housing 22 attached to a mouthpiece 24. A plunger 26 is operatively associated with the housing 22 and is used to receive a cartridge containing a composition to be inhaled. The composition may include a spray or powder.

[0082] During use, the inhaler 20 administers a measured dose of medication, such as an asthma medication, to the patient. The asthma medication may be suspended or dissolved in a propellant, or it may be contained in powder. When the patient activates the inhaler to inhale the medication, a valve opens to allow the medication to exit the mouthpiece. According to this disclosure, the housing 22, mouthpiece 24, and plunger 26 may all be made of the polymer composition described above.

[0083] refer to Figure 3 This demonstrates another medical product that can be manufactured according to this disclosure. Figure 3 The image shows a medical injector 30. 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 be spring-loaded. The medical injector is used to inject medication into a patient, typically into the thigh or buttock. The medical injector may be needle-free or may contain a needle. When a needle is included, the needle tip is typically concealed within the housing before injection. Alternatively, a needle-free injector may contain a cylinder of pressurized gas that can propel medication through the skin without the use of a needle. According to this disclosure, the housing 32 and / or the plunger 34 may be made of a polymer composition as described above.

[0084] While the polyoxymethylene polymer compositions and polymer articles derived therefrom of this disclosure offer improved emissions performance, the compositions and articles also exhibit excellent mechanical properties (ISO 527 test). For example, when tested according to ISO 527, the polymer compositions can have a tensile modulus greater than about 1,200 MPa, for example greater than about 2,000 MPa. Tensile modulus is typically less than about 10,000 MPa.

[0085] The polymer composition can exhibit a value greater than about 3 kJ / m at 23°C. 2 For example, greater than about 6 kJ / m 2 Impact strength of a notched simply supported beam (ISO 179-1 test). The impact strength of a notched simply supported beam is typically less than about 20 kJ / m. 2 .

[0086] The following examples can be used to better understand this disclosure.

[0087] Example

[0088] The following examples demonstrate some advantages and benefits of the polymer compositions prepared according to this disclosure.

[0089] Various polymer compositions were formulated, molded into test specimens, and formaldehyde emissions were tested. The polymer compositions contained polyoxymethylene copolymers. According to ISO 1133 testing, the polyoxymethylene polymer had a density of approximately 9 cm⁻¹. 3 The melt volume rate is 10 min. In addition to the polyoxymethylene polymer, the polymer composition also contains 0.2 wt% of the antioxidant triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate and 0.2 wt% of ethylene bis(stearamide).

[0090] Various additives were then combined with the polymer composition described above, and formaldehyde emissions were tested. Each formulation was compounded on a 32mm co-rotating twin-screw extruder (ZSK 32, Coperion, Germany). Test samples were injection molded. Test samples were formed from granules dried at 140°C for two hours at temperatures of 185°C, 195°C, and 205°C. The test samples had a thickness of 1mm. As specified in the VDA test, the sample size was 40mm × 100mm.

[0091] According to the Ford 10-liter bag method (hereinafter referred to as the "10-liter bag method") of test reference number BZ 108-01 (July 2, 2018), the sample was tested using a 1mm test piece with a total mass of approximately 26g. Before testing, the sample was conditioned for 72 hours at 23°C and 50% humidity as specified in the test.

[0092] Formaldehyde emissions from the formulation were also tested using 1mm samples according to VDA 275 testing. The samples were stored at 23°C and 50% humidity for 24 hours. Then, as specified in the test, the samples were extracted with 50mL of ultrapure water at 60°C for 3 hours. After 24 hours, the released formaldehyde was measured as specified in the test.

[0093] In addition to the components mentioned above, the tested polymer composition also contained a formaldehyde stabilizer package. The formaldehyde stabilizer comprised a combination of substituted hydantoin and aliphatic carboxylic acid hydrazide. The table below lists the components combined with the polyoxymethylene polymer, including the emission control agent and formaldehyde emission results. Results were extrapolated to 7 days based on a 2 mm thick sample.

[0094]

[0095] As shown above, sample 6 does not contain calcium salts of carboxylic acids and exhibits surprisingly low formaldehyde emissions. Even at relatively low concentrations, samples 4 and 5, which contain calcium stearate, showed elevated formaldehyde emissions.

[0096] These and other modifications and variations can be made to the invention by those skilled in the art without departing from the spirit and scope of the invention, which are more specifically set forth in the appended claims. Furthermore, it should be understood that aspects of the various embodiments can be interchanged in whole or in part. Moreover, those skilled in the art will understand that the foregoing description is merely illustrative and not intended to limit the invention further described in the appended claims.

Claims

1. A polymer composition comprising: Polyoxymethylene polymers; and A formaldehyde stabilizer package for reducing formaldehyde emissions, the formaldehyde stabilizer package comprising at least two emission control agents, the emission control agents comprising a combination of aliphatic carboxylic acid hydrazide and substituted hydantoin; and The polymer composition therein does not contain calcium stearate and calcium 12-hydroxystearate.

2. The polymer composition according to claim 1, wherein the polymer composition is free of alkaline earth metal salts of aliphatic carboxylic acids.

3. The polymer composition according to claim 1, wherein the aliphatic carboxylic acid hydrazide is present in a weight ratio of about 1:20 to about 10:1, for example about 1:8 to about 2:1, relative to the substituted hydantoin.

4. The polymer composition according to claim 1, wherein the substituted hydantoin contains two hydrazinocarbonyl alkyl groups.

5. The polymer composition according to claim 1, wherein the substituted hydantoin comprises 4-isopropyl-2,5-dioxoimidazolidine-1,3-bis(propionylhydrazine).

6. The polymer composition according to any one of the preceding claims, wherein the aliphatic carboxylic acid hydrazide comprises sebacate dihydrazide, dodecanoic acid dihydrazide, or a mixture thereof.

7. 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 of less than about 0.15% by weight.

8. The polymer composition according to any one of the preceding claims, wherein when tested according to test VDA-275 at a thickness of 1 mm and a molding temperature of 205°C, the polymer composition exhibits formaldehyde emissions of less than about 20 ppm.

9. The polymer composition according to any one of the preceding claims, wherein when tested according to test VDA-275 at a thickness of 1 mm and a molding temperature of 185°C, the polymer composition exhibits formaldehyde emissions of less than about 8 ppm, for example less than about 5 ppm, for example less than about 3 ppm; and when tested according to test VDA-275 at a thickness of 1 mm and a molding temperature of 195°C, the polymer composition exhibits formaldehyde emissions of less than about 15 ppm, for example less than about 10 ppm.

10. The polymer composition according to any one of the preceding claims, wherein, when tested according to the 10-liter bag test at a molding temperature of 195°C, the polymer composition exhibits less than about 300 μg / m³. 3 For example, less than about 250 μg / m 3 For example, less than about 200 μg / m 3 For example, less than about 150 μg / m 3 Formaldehyde emissions.

11. The polymer composition according to any one of the preceding claims, wherein, when tested according to the 10-liter bag test at a molding temperature of 205°C, the polymer composition exhibits less than about 10,000 μg / m³. 3 For example, less than about 5,000 μg / m 3 For example, less than about 1,000 μg / m 3 For example, less than about 750 μg / m 3 Formaldehyde emissions.

12. 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 0.01% by weight, for example, in an amount greater than about 0.03% by weight, for example, in an amount greater than about 0.07% by weight, for example, in an amount greater than about 0.08% by weight, and in an amount less than about 0.5% by weight.

13. The polymer composition according to any one of the preceding claims, wherein the polyoxymethylene polymer has a density of about 5 cm² when tested at 190°C and a load of 2.16 kg. 3 / 10min to approximately 15cm 3 Melt flow rate per 10 min.

14. The polymer composition according to any one of the preceding claims, wherein the polymer composition further comprises about 0.05% by weight to about 1% by weight of a nucleating agent.

15. The polymer composition according to any one of the preceding claims, wherein the polymer composition further comprises about 0.05% to about 2% by weight of a phenolic antioxidant and about 0.05% to about 1.5% by weight of a lubricant.

16. The polymer composition according to any one of the preceding claims, wherein the polymer composition further comprises about 5% to about 30% by weight of a thermoplastic elastomer.

17. 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% to about 40% by weight.

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

19. A polymer composition comprising: Polyoxymethylene polymer; A formaldehyde stabilizer package for reducing formaldehyde emissions, the formaldehyde stabilizer package comprising a combination of an aliphatic carboxylic acid hydrazine and a substituted hydantoin, the substituted hydantoin containing two hydrazyl carbonyl alkyl groups; and When tested according to the VDA-275 standard at a thickness of 1 mm and a molding temperature of 205°C, formaldehyde emissions were less than approximately 20 ppm, and when tested according to the 10-liter bag standard at a molding temperature of 205°C, formaldehyde emissions were less than approximately 1000 μg / m³. 3 .

20. The polymer composition of claim 19, wherein the polymer composition is free of alkaline earth metal salts of aliphatic carboxylic acids.

21. A molded article made of the polymer composition of any one of the preceding claims.

22. The molded article of claim 21, wherein the molded article comprises automotive interior parts.

23. The molded article of claim 21, wherein the molded article comprises a latch, lever, gear, pivot housing, speaker grille, door handle, decorative trim, bracket, or seat rail.

24. The molded article of claim 21, wherein the molded article comprises an inhaler or a syringe.

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