Low-emission polyoxymethylene compositions

Abstract

A polyoxymethylene polymer composition is disclosed, comprising a formaldehyde stabilizer package. This formaldehyde stabilizer package, containing at least two emission control agents, significantly and unexpectedly reduces formaldehyde emissions. The formaldehyde stabilizer package includes at least two emission control agents selected from benzoguanamine compounds, hydantoin, substituted hydantoin, amino acids, and alkylene ureas such as ethylene urea.

Description

[0001] Related applications

[0002] This application is based on and claims priority to U.S. Provisional Patent Application Serial No. 62 / 483108, filed on April 7, 2017, which is incorporated herein by reference. background

[0003] Polyacetal polymers (commonly known as polyoxymethylene) have been recognized as particularly useful engineering materials in many applications. For example, polyoxymethylene polymers are widely used to construct molded parts, such as those used in the automotive and power industries. Polyoxymethylene polymers also possess excellent mechanical properties, fatigue resistance, abrasion resistance, chemical resistance, and moldability.

[0004] While polyacetal resins possess many useful properties, this polymer is prone to degradation upon heating and is inherently unstable in oxidizing atmospheres or in acidic or alkaline environments. In particular, polyacetal resins tend to release formaldehyde during processing and after the polymer is molded into parts. Formaldehyde is not only a pollutant but also adversely affects 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.

[0005] In light of the above, those skilled in the art have explored combining polyacetal polymers with various compounds to reduce formaldehyde emissions. In the past, for example, polyacetal polymers have been combined with melamine to achieve formaldehyde emission reduction. Furthermore, various other chemical compounds have been proposed for reducing formaldehyde emissions.

[0006] While various chemical compounds used in the past have successfully reduced formaldehyde emissions from products made from polyoxymethylene polymers, further improvements are needed in formaldehyde emission control. For example, increasingly stringent government regulations continue to demand further improvements in formaldehyde emission reduction.

[0007] Unfortunately, when additives are combined with polyacetal polymers to enhance one property, the additive can adversely affect another. For example, adding a larger amount of formaldehyde scavenger to a polyacetal polymer composition can jeopardize one or more properties of the polymer. For instance, excessive formaldehyde scavenger can increase the occurrence of mold deposits and / or begin to adversely affect other physical properties.

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

[0009] Overview

[0010] Generally, this disclosure relates to a polymer composition primarily comprising a polyacetal resin and to molded products made from the composition. The polymer compositions of this disclosure are specially formulated to exhibit extremely low formaldehyde emissions. For example, polyacetal polymer compositions formulated according to this disclosure can exhibit formaldehyde emissions of less than about 5 ppm, for example less than about 4 ppm, or even less than about 3 ppm when tested according to VDA Test 275. VDA 275 Test (German Automotive Industry Recommendation No. 275) was recorded by Kraftfahrwesen eV in July 1994.

[0011] For example, in one embodiment, 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 comprise a blend of emission control agents. The blend comprises at least two emission control agents selected from guanidine compounds, hydantoin, substituted hydantoin, amino acids, and alkylene ureas such as ethylene urea. For example, in one embodiment, the formaldehyde stabilizer package may comprise a blend of a guanidine compound and a substituted hydantoin such as allantoin. Alternatively, the formaldehyde stabilizer package may comprise a blend of a guanidine compound and a hydantoin. In yet another embodiment, the formaldehyde stabilizer package comprises a blend of a guanidine compound and an amino acid. The amino acid may, for example, comprise arginine. The substituted hydantoin, hydantoin, or amino acid may typically be present in the polymer composition in an amount less than about 0.5% by weight, for example, less than about 0.3% by weight, for example, less than about 0.2% by weight. The aforementioned emission control agent is typically present in the polymer composition in an amount greater than about 0.001% by weight.

[0012] In one embodiment, the guanidine compound comprises benzoguanidine. When present, the benzoguanidine may be included in the composition in an amount greater than about 0.2% by weight, for example, greater than about 0.3% by weight, for example, greater than about 0.4% by weight, and typically less than about 2% by weight, for example, less than about 1.5% by weight. The guanidine compound may be present relative to another emission control agent in a weight ratio of about 20:1 to about 1:1, for example, about 15:1 to about 2:1, for example, about 8:1 to about 3:1.

[0013] In an alternative embodiment, particularly when the polyoxymethylene polymer composition is used to manufacture medical products, the formaldehyde stabilizer package comprises a blend of substituted hydantoin and an amino acid. The substituted hydantoin may contain allantoin. The amino acid may contain arginine.

[0014] In one embodiment, the formaldehyde stabilizer package contains ethylurea, for example, in an amount of about 0.001% by weight to about 5% by weight. The ethylurea can be combined with any other formaldehyde stabilizer mentioned above (including benzoguanidine and / or allantoin).

[0015] Typically, any suitable polyoxymethylene polymer can be included in this polymer composition. In one embodiment, the polyoxymethylene polymer has a diameter of approximately 5 cm. 3 / 10min to approximately 15cm 3 The melt flow rate is approximately 10 min. In an alternative embodiment, the polyoxymethylene polymer has a melt flow rate of approximately 18 cm⁻¹. 3 / 10min to approximately 40cm 3 Melt flow rate per 10 min.

[0016] Various other additives may be included in the polymer composition. In one embodiment, the composition further contains, for example, an acid-scavenging agent such as a calcium salt. The composition may also contain a colorant. The colorant may be present in the composition in an amount from about 0.1% by weight to about 5% by weight. When the colorant is present in the composition, the acid-scavenging agent may comprise calcium propionate.

[0017] In one embodiment, the polymer composition contains about 0.05% to about 1% by weight of a nucleating agent, about 0.05% to about 2% by weight of an antioxidant, and about 0.05% to about 1.5% by weight of a lubricant.

[0018] In one embodiment, the polymer composition may include an impact modifier. The impact modifier may, for example, comprise a thermoplastic elastomer such as a thermoplastic polyurethane elastomer. The impact modifier may be present in an amount from about 5% by weight to about 30% by weight.

[0019] The polymer composition may also contain one or more reinforcing agents. These reinforcing agents may include, for example, reinforcing fibers such as glass fibers. The reinforcing fibers are typically present in the polymer composition in an amount from about 3% to about 40% by weight.

[0020] In one embodiment, the polymer composition may further include a UV stabilizer.

[0021] Polymer compositions manufactured according to this disclosure can possess an excellent balance of physical properties. For example, the polymer composition can have a tensile modulus of at least 1200 MPa at 23°C when tested according to ISO Test 527, a yield tensile strain greater than about 7% at 23°C when tested according to ISO Test 527, and a tensile strain greater than about 3 kJ / m² at 23°C when tested according to ISO Test 179-1.2 Impact strength of a simply supported beam with a notch.

[0022] A wide variety of articles can be molded from this polymer composition. Due to its low formaldehyde emissions, this polymer composition is particularly well-suited for producing molded articles for automotive interiors. These molded articles can include, for example, levers, gears, pivot sleeves, decorative trim pieces, door handles, brackets, speaker covers, or seat rails. Alternatively, this polymer composition can be used to produce medical products. These medical products can include, for example, inhalers or syringes.

[0023] Other features and aspects of this disclosure are discussed in more detail below. Attached Figure Description

[0024] The complete and full disclosure of this disclosure is set forth in more detail in the remainder of the specification, including with reference to the accompanying drawings, in which:

[0025] Figure 1 It is a perspective view of the interior of a car, showing various molded articles that can be manufactured according to the present disclosure;

[0026] Figure 2 This is a perspective view of a medical inhaler, which can be manufactured from a molded part according to this disclosure; and

[0027] Figure 3 It is a perspective view of a medical syringe containing a molded part manufactured in accordance with the present disclosure.

[0028] Figure 4 A device for measuring formaldehyde emissions is shown, as described in the following examples.

[0029] Reference numerals used repeatedly in this application specification and drawings are intended to indicate the same or similar features or elements of the invention. Detailed description

[0030] Those skilled in the art will understand that the present discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this disclosure.

[0031] Generally, this disclosure relates to a polymer composition exhibiting low formaldehyde emissions, comprising a polyacetal resin, particularly a polyoxymethylene copolymer. This polymer composition is particularly suitable for use in molding processes for producing molded articles. The polymer composition may contain one or more colorants for producing molded articles with any desired color. The molded article can be used in an unlimited number of different applications and in multiple fields. In one embodiment, for example, the molded article can be manufactured according to this disclosure and designed to function as an automotive part, such as an automotive part designed for use inside vehicles (e.g., cars and trucks).

[0032] 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 a blend of emission control agents. Emission control agents that can be used in the formaldehyde stabilizer package include guanidine compounds, hydantoin, substituted hydantoin, amino acids, and alkylene ureas such as ethylene urea. The guanidine compound may, for example, comprise benzoguanidine.

[0033] In one embodiment, the formaldehyde stabilizer package comprises a blend of at least one of hydantoin, a substituted hydantoin, an amino acid, or an ethylurea, and a guanidine compound. In another embodiment, for example, the formaldehyde stabilizer package comprises a combination of a guanidine compound and allantoin (which is a substituted hydantoin). Alternatively, the formaldehyde stabilizer package may comprise a blend of a guanidine compound and an amino acid such as arginine. In some embodiments, the formaldehyde stabilizer package significantly and effectively reduces formaldehyde emissions from the polymer composition without compromising other properties.

[0034] For example, in one embodiment, the polymer composition containing the polyoxymethylene polymer exhibits formaldehyde emissions of less than about 5 ppm (μg / g), for example less than about 4 ppm, or for example less than about 3 ppm according to VDA275. The formaldehyde emissions of the polymer composition can be substantially zero.

[0035] Typically, any suitable polyoxymethylene polymer can be incorporated into this polymer composition.

[0036] The preparation of this polyoxymethylene polymer can be achieved by polymerizing polyoxymethylene monomers, such as trioxymethylene, in the presence of a molecular weight regulator (e.g., diol). Alkane or trialkyl The mixture is made from alkyl groups and cyclic acetals (e.g., dioxolane). The polyoxymethylene polymer used in this polymer composition may comprise homopolymers or copolymers. According to one embodiment, the polyoxymethylene is a homopolymer or copolymer containing at least 50 mol%, for example at least 75 mol%, for example at least 90 mol%, and for example even at least 97 mol% of -CH2O- repeating units.

[0037] In one embodiment, a polyoxymethylene copolymer is used. The copolymer may contain about 0.01 mol% to about 20 mol%, and particularly about 0.5 mol% to about 10 mol%, repeating units comprising a saturated or olefinically unsaturated alkylene group or a cycloalkylene group having at least two carbon atoms, 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 cyclic acetal that can be introduced into the copolymer via a ring-opening reaction is used.

[0038] Preferred cyclic ethers or cyclic acetals are those of the following formula:

[0039]

[0040] Where x is 0 or 1 and R 2 It is a C2-C4 alkylene group, which, if appropriate, has one or more substituents, which are C1-C4 alkyl or C1-C4 alkoxy groups, and / or halogen atoms, preferably chlorine atoms. By way of example only, ethylene oxide, 1,2-epoxypropane, 1,2-epoxybutane, 1,3-epoxybutane, and 1,3-di(ethylene oxide) may be mentioned. Alkane, 1,3-dioxolane, and 1,3-dioxane-heptane are mentioned as cyclic ethers, and linear oligooxymethylene or polyoxymethylene, such as polydioxolane or polydioxane-heptane, are also mentioned as comonomers. Particularly advantageous is the use of trialkylene oxide containing 99.5-95 mol% of trialkylene oxide. A copolymer of alkane and 0.01-5 mol%, for example 0.5-4 mol%, of one of the aforementioned comonomers. In one embodiment, the polyoxymethylene polymer contains a relatively low amount of comonomer. For example, the comonomer may be present in an amount of 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%.

[0041] The polymerization can be carried out via precipitation polymerization or in a melt. By appropriately selecting polymerization parameters such as polymerization duration or the amount of molecular weight regulator, the molecular weight of the resulting polymer and thus the MVR value can be adjusted.

[0042] 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 end positions. These reactive groups may, for example, include -OH or -NH2 groups.

[0043] In one embodiment, the polyoxymethylene polymer may have terminal hydroxyl groups, such as hydroxyethylidene and / or hydroxyl side groups, in at least more than about 50% of all end positions on the polymer. For example, the polyoxymethylene polymer may have at least about 70%, for example at least about 80%, for example at least about 85%, of its end groups as hydroxyl groups, based on the total number of end groups present. It should be understood that the total number of end groups present includes all side end groups.

[0044] In one embodiment, the polyoxymethylene polymer has a terminal hydroxyl content of at least 15 mmol / kg, for example, at least 18 mmol / kg, for example, at least 20 mmol / kg. In another embodiment, the terminal hydroxyl content is 18-50 mmol / kg. In an alternative embodiment, the polyoxymethylene polymer may contain terminal hydroxyl groups in an amount of 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 terminal hydroxyl groups in an amount of about 5 mmol / kg to about 20 mmol / kg, for example, about 5 mmol / kg to about 15 mmol / kg. For example, a polyoxymethylene polymer with a lower terminal hydroxyl content but a higher melt volume flow rate can be used.

[0045] In addition to or in place of the terminal hydroxyl groups, the polyoxymethylene polymer may also have other end groups commonly used in these polymers. Examples of these are alkoxy, formate, acetate, or aldehyde groups. According to one embodiment, the polyoxymethylene is a homopolymer or copolymer containing at least 50 mol%, for example at least 75 mol%, for example at least 90 mol%, and for example even at least 95 mol% of -CH2O- repeating units.

[0046] 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 such as ethylene glycol or methyl acetal can be used as chain terminators. Heteropolyacids, trifluoromethanesulfonic acid, or boron compounds can be used as catalysts.

[0047] The polyoxymethylene polymer can have any suitable molecular weight. For example, the molecular weight of the polymer can be from about 4000 g / mol to about 20000 g / mol. However, in other embodiments, the molecular weight can be much higher than 20000 g / mol, for example from about 20000 g / mol to about 100000 g / mol.

[0048] The polyoxymethylene polymer present in this composition can typically have a thickness of about 0.1 to about 80 cm³, as measured according to ISO 1133 at 190°C and 2.16 kg. 3 The melt flow index (MFI) is approximately 5 cm⁻¹ / 10 min. In one embodiment, the polyoxymethylene polymer can have a melt flow index of approximately 5 cm⁻¹ / 10 min. 3 / 10min to approximately 15cm 3 / 10min, for example, about 8cm 3 / 10min to approximately 12cm 3 The 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, this polyoxymethylene polymer may 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.

[0049] Suitable commercially available polyoxymethylene polymers are those listed under the trademark. Available in Celanese under (HF).

[0050] 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%, wherein this weight is based on the total weight of the polyoxymethylene polymer composition.

[0051] The aforementioned polyoxymethylene polymer is combined with a formaldehyde stabilizer package that significantly and effectively reduces formaldehyde emissions from the polymer composition. The formaldehyde stabilizer package of this disclosure comprises a blend of emission control agents. For example, the blend includes at least two emission control agents selected from guanidine compounds, hydantoin, substituted hydantoin, amino acids, and alkylene ureas such as ethylene urea.

[0052] In one embodiment, the formaldehyde stabilizer comprises a guanidine compound. The guanidine compound may include aliphatic guanidine compounds, alicyclic guanidine compounds, aromatic guanidine compounds, heteroatom-containing guanidine compounds, etc. In one embodiment, the guanidine compound comprises benzoguanidine. When included in the composition, the guanidine compound may be present in the polymer composition in an amount of at least about 0.05% by weight, for example, at least about 0.1% by weight, for example, at least about 0.3% by weight, for example, at least about 0.5% by weight. The guanidine compound is typically present in the composition in an amount of less than about 2% by weight, for example, less than about 1.5% by weight, for example, less than about 1% by weight, for example, less than about 0.8% by weight.

[0053] The formaldehyde stabilizer package may also include hydantoin or substituted hydantoin. An example of a substituted hydantoin is allantoin. Allantoin is also known as (2,5-dioxa-4-imidazolidinyl)urea and has the chemical formula C4H6N4O3. Allantoin has been found to reduce formaldehyde emissions, even when one or more light stabilizers are present in the composition. When included in the composition, hydantoin or substituted hydantoin may typically be present in amounts less than about 1.5% by weight, for example, less than about 1% by weight, for example, less than about 0.5% by weight, for example, less than about 0.3% by weight, for example, less than about 0.2% by weight. Hydantoin or substituted hydantoin may typically be present in amounts greater than about 0.001% by weight.

[0054] The formaldehyde stabilizer package may also contain an amino acid combined with at least one other emission control agent. This amino acid may, for example, comprise α-amino acids, β-amino acids, γ-amino acids, δ-amino acids, and mixtures thereof. For example, the amino acid may comprise a monoamino monocarboxylic acid or a monoamino dicarboxylic acid. Examples include glycine, alanine, valine, n-valine, leucine, n-leucine, isoleucine, phenylalanine, tyrosine, diiodotyrosine, ketaline, threonine, serine, proline, hydroxyproline, tryptophan, methionine, cystine, cysteine, citrulline, α-aminobutyric acid, hexahydropyridinecarboxylic acid, theanine, aspartic acid, glutamic acid, asparagine, glutamine, hexahydropyridine dicarboxylic acid, hexahydroquinoline acid, and mixtures thereof. Other amino acids that may be used include diamino monocarboxylic acids such as lysine, hydroxylysine, arginine, histidine, or mixtures thereof. An amino acid particularly suitable for use in this disclosure is, for example, arginine. Arginine can be considered an aliphatic amino acid.

[0055] When present in the composition, the amino acid may be included in an amount typically less than about 2% by weight, for example, less than about 1.5% by weight, for example, less than about 1% by weight, for example, less than about 0.5% by weight, for example, less than about 0.3% by weight, for example, less than about 0.2% by weight. The amino acid is typically present in an amount greater than about 0.001% by weight.

[0056] The formaldehyde stabilizer package disclosed herein can consist of a variety of different combinations of emission control agents, depending on the specific application and desired results. In one embodiment, for example, the formaldehyde stabilizer package includes a combination of a guanidine compound with at least one other emission control agent. For example, the guanidine compound may be combined with allantoin and / or arginine. In one embodiment, the formaldehyde stabilizer package includes a combination of a guanidine compound, hydantoin, substituted hydantoin, and an amino acid.

[0057] In an alternative embodiment, the formaldehyde stabilizer package does not contain guanidine compounds such as benzoguanidine. For example, the formaldehyde stabilizer package may be guanidine-free. In one embodiment, the formaldehyde stabilizer package may contain, for example, a combination of substituted hydantoin (such as allantoin) and an amino acid (such as arginine). In yet another embodiment, the formaldehyde stabilizer package may contain a blend of hydantoin, substituted hydantoin, amino acids, and ethylurea.

[0058] In one embodiment, the formaldehyde stabilizer package may also contain ethylidene urea such as 2-imidazolidone or 2-imidazolinone. For example, one embodiment may contain a compound of the following formula:

[0059]

[0060] The ethylurea may be present in some embodiments in amounts greater than about 0.001% by weight, for example greater than about 0.01% by weight, for example greater than about 0.1% by weight, for example greater than about 1% by weight, for example greater than about 3% by weight. In some embodiments, the ethylurea may be present in amounts less than about 5% by weight, for example less than about 3% by weight, for example less than about 1% by weight, for example less than about 0.1% by weight.

[0061] Advantageously, in some embodiments, the ethylidene urea can be combined with at least one other formaldehyde stabilizing compound for a synergistic effect. For example, ethylidene urea can be combined with benzoguanamine and / or allantoin.

[0062] In each of the above formaldehyde stabilizer packages, the stabilizer package may include a single amino acid and / or a single substituted hydantoin or at least two amino acids and / or at least two substituted hydantoins.

[0063] In addition to the polyoxymethylene polymer and formaldehyde stabilizer package, the polymer compositions of this disclosure may contain a variety of other additives and ingredients. For example, in one embodiment, the polymer composition may contain an acid scavenger. The acid scavenger may comprise a carboxylate.

[0064] For example, the carboxylate can contain salts of fatty acids, such as metal salts of fatty acids. For example, the carboxylate can contain alkaline earth metal salts of fatty acids. The cations of the salt can include, for example, calcium, barium, lithium, sodium, magnesium, zinc, etc.

[0065] This fatty acid can contain a carbon chain that typically consists of about 3 to about 20 carbon atoms. It can contain dicarboxylic acids or tricarboxylic acids.

[0066] In one embodiment, the metal salt of the fatty acid may comprise metal salts of citric acid, propionic acid, stearic acid, butyric acid, hexanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, etc. In a particular embodiment, the metal salt of the fatty acid may comprise calcium propionate, calcium 12-hydroxystearate, calcium citrate such as tricalcium citrate, and mixtures thereof. In one embodiment, when the polyoxymethylene polymer composition includes one or more colorants, various benefits and advantages are obtained by combining the colorant with calcium propionate.

[0067] One or more carboxylates are typically present in the polymer composition in an amount greater than about 0.05% by weight, for example, greater than about 0.1% by weight, for example, greater than about 0.2% by weight, for example, greater than about 0.3% by weight, for example, greater than about 0.4% by weight, for example, greater than about 0.5% by weight. One or more carboxylates are typically present in the polymer composition in an amount less than about 5% by weight, for example, less than about 3% by weight, for example, less than about 2% by weight, for example, less than about 1.5% by weight, for example, less than about 1% by weight.

[0068] 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. Additionally, the compositions may contain processing aids such as adhesion promoters, lubricants, nucleating agents, release agents, fillers or antistatic agents, as well as additives that impart desired properties to the composition and articles or parts produced therefrom.

[0069] In one embodiment, a UV stabilizer may be present. The UV stabilizer may comprise benzophenone, benzotriazole, or a benzoate. A UV absorber, when present, 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 compositions.

[0070] In one embodiment, a nucleating agent may be present. This nucleating agent can increase crystallinity and may contain an oxymethylene terpolymer. In a particular embodiment, for example, the nucleating agent may contain butanediol diglycidyl ether, ethylene oxide, and trimethylolpropane. A terpolymer of alkane. 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%, wherein the weight is based on the total weight of the respective polymer compositions.

[0071] In one embodiment, an antioxidant such as a sterically hindered phenol may be present. Commercially available examples are pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 3,3′-bis[3-(3,5-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%, wherein the weight is based on the total weight of the respective polymer compositions.

[0072] In one embodiment, in addition to the UV light stabilizer, a light stabilizer such as a sterically hindered amine may be present. Hindered amine light stabilizers that can be used include N-methylated oligomeric hindered amine compounds. For example, the hindered amine light stabilizer may comprise a high molecular weight hindered amine stabilizer. Other embodiments of the light stabilizer include 2,2,6,6-tetramethyl-4-piperidinyl compounds such as bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate or dimethyl succinate and a polymer of 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine. In one embodiment, the light stabilizer may comprise 2-(2H-benzotriazol-2-yl)4,6-bis(1-ethyl-1-phenyl-ethyl)phenol. The light stabilizer, when present, may be present in the polymer composition in an amount of at least about 0.01 wt%, 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 compositions.

[0073] In one embodiment, a lubricant may be present. The lubricant may comprise a polymer wax composition. Furthermore, 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, PEG-75 may be present, for example. 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%, or, for example, at least about 0.075 wt%, and less than about 1 wt%, for example, less than about 0.75 wt%, or, for example, less than about 0.5 wt%, where the weight is based on the total weight of the respective polymer compositions.

[0074] In one embodiment, a colorant may be present. Colorants that can be used include any desired inorganic pigments such as titanium dioxide, ultramarine, cobalt blue, and other organic pigments and dyes such as phthalocyanine, anthraquinone, etc. Other colorants include carbon black or various other polymer-soluble dyes. In one embodiment, a combination of colorants may be included in the polymer composition. For example, the polymer composition may 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 with at least one coloring pigment (e.g., yellow and green pigments), and optionally further combined with carbon black. The colorant 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%, 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%, wherein the weight is based on the total weight of the respective polymer compositions.

[0075] Fillers that may be included in the composition include glass beads, wollastonite, loam, molybdenum disulfide or graphite, and / or inorganic or organic fibers.

[0076] The reinforcing fibers that may be included in the composition are mineral fibers such as glass fibers, polymer fibers, especially organic high-modulus fibers such as polyaramid fibers, metal fibers such as steel fibers, carbon fibers, natural fibers, and / or fibers derived from renewable resources.

[0077] These fibers can be in modified or unmodified forms (such as those with sizing or chemical treatment) to improve adhesion to polymers. Glass fibers are particularly preferred.

[0078] Glass fibers are sizing agents used to protect the glass fibers, smooth the fibers, and improve the adhesion between the fibers and the matrix material. Sizing agents typically contain silanes, film-forming agents, lubricants, wetting agents, adhesives, optional antistatic agents and plasticizers, emulsifiers, and optional additional additives.

[0079] Specific examples of silanes are aminosilanes such as 3-trimethoxysilylpropylamine, N-(2-aminoethyl)-3-aminopropyltrimethoxy-silane, N-(3-trimethoxysilylpropyl)ethane-1,2-diamine, 3-(2-aminoethyl-amino)propyltrimethoxysilane, and N-[3-(trimethoxysilyl)propyl]-1,2-ethane-diamine.

[0080] Film-forming agents are, for example, polyvinyl acetate, polyester, and polyurethane. Polyurethane-based sizing agents can be used advantageously.

[0081] Reinforcing fibers can be incorporated into the polyoxymethylene matrix, for example, in an extruder or kneader. However, the reinforcing fibers can also advantageously be in the form of continuous filament fibers coated or impregnated with a polyoxymethylene molding composition in a process suitable for this purpose, and then processed or wound as continuous strips, or cut to the desired pellet length so that the fiber length and pellet length are the same. An example of a process particularly suitable for this purpose is pultrusion.

[0082] The reinforcing fibers may be present in the molding composition in an amount of 5-45 wt%, for example 10-40 wt%, where the weight is based on the total weight of the composition.

[0083] The polymer composition may further include impact modifiers such as thermoplastic elastomers. Thermoplastic elastomers are materials that possess both thermoplastic and elastomer properties. Thermoplastic elastomers include styrene block copolymers, polyolefin blends (called thermoplastic olefin elastomers), elastomer alloys, thermoplastic polyurethanes, thermoplastic copolyesters, and thermoplastic polyamides.

[0084] Thermoplastic elastomers particularly suitable for use in this disclosure are polyester elastomers (TPE-E), thermoplastic polyamide elastomers (TPE-A), and especially thermoplastic polyurethane elastomers (TPE-U).

[0085] In one particular embodiment, a thermoplastic polyurethane elastomer is used. This thermoplastic polyurethane elastomer may, for example, have soft segments of a long-chain diol and hard segments derived from diisocyanates and chain extenders. In one embodiment, the polyurethane elastomer is a polyester type prepared by reacting a long-chain diol with a diisocyanate to produce a polyurethane prepolymer having 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(butylene adipate) diol, poly(ethylene adipate) diol, and poly(ε-caprolactone) diol; and polyether diols such as poly(tetramethylene ether) diol, poly(propylene oxide) diol, poly(ethylene oxide) diol, polycarbonate diol, and / or polyester polycarbonate diol. Suitable diisocyanates include 4,4′-methylenebis(phenylisocyanate), 2,4-toluene diisocyanate, 1,6-hexamethylene diisocyanate, and 4,4′-methylenebis(cyclohexylisocyanate). Suitable chain extenders are C2-C6 aliphatic glycols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol. An example of a thermoplastic polyurethane is characterized as essentially poly(adipic acid-copolymer-butanediol-copolymer-diphenylmethane diisocyanate).

[0086] The amount of thermoplastic elastomer contained 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.

[0087] In one embodiment, when an impact modifier or thermoplastic elastomer is present in the composition, the composition may further include a coupling agent. The coupling agent may comprise a polyisocyanate such as a diisocyanate or a triisocyanate. The coupling agent may typically be present in an amount of about 0.1 to about 2% by weight, for example, about 0.1 to about 1% by weight.

[0088] The compositions disclosed herein can be formulated and shaped into polymer articles using any techniques known in the art. For example, the respective compositions can be vigorously mixed to form a substantially homogeneous blend. This blend can be melt-kneaded at elevated temperatures, such as above the melting point of the polymer used in the polymer composition but below its degradation temperature. Alternatively, the respective compositions can be melt-mixed together in a conventional single or twin-screw extruder. Preferably, the melt mixing is carried out at temperatures of 100-280°C, for example 120-260°C, for example 140-240°C, or 180-220°C.

[0089] 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.

[0090] The polymer compositions of this disclosure 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 manufactured according to this disclosure include handles, door handles, automotive decorative trim pieces, etc., without limitation. Other polymer articles (such as those that can be manufactured according to this disclosure) include levers, gears, pivot sleeves, speaker covers, etc.

[0091] For example, see Figure 1 The image shows the interior of a car, illustrating various automotive parts that can be manufactured according to this disclosure. The polymer composition can, for example, 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 frame, such as trim 14.

[0092] As described above, in one embodiment, the formaldehyde stabilizer package does not include guanidine compounds. Alternatively, the formaldehyde stabilizer package may include combinations of hydantoin, substituted hydantoin, amino acids, and / or ethylurea. Guanidine-free compositions are particularly well-suited for use in the manufacture of medical products. See, for example, [link to relevant documentation]. Figure 2 The image shows an inhaler 20. The inhaler 20 includes a housing 22 connected to an interface tube 24. Connected to the housing 22 during operation is a plunger 26 for receiving a canister containing a composition to be inhaled. This composition may contain a spray or powder.

[0093] During use, the inhaler 20 delivers a measured dose of medication, such as asthma medication, to the patient. The asthma medication may be suspended or dissolved in a propellant or may be contained in powder. When the patient activates the inhaler to inhale the medication, a valve opens, allowing the medication to exit the interface tube. According to this disclosure, the housing 22, the interface tube 24, and the plunger 26 may all be made of the aforementioned polymer composition.

[0094] See Figure 3 This shows another medical product that can be manufactured according to the content of this disclosure. Figure 3 The image shows a medical syringe 30. The medical syringe 30 includes a housing 32 operatively connected to a plunger 34. The housing 32 is slidable relative to the plunger 34. The medical syringe 30 may be a loaded spring. The medical syringe is used to inject medication into a patient, typically into the thigh or buttock. The medical syringe may be needle-free or may contain a needle. When containing a needle, the needle tip is typically concealed within the housing before injection. On the other hand, a needle-free syringe may contain a cylinder of pressurized gas that propels the 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 the aforementioned polymer composition.

[0095] While the polyoxymethylene polymer compositions and polymer articles made therefrom of this disclosure offer improved emissions performance, 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 composition may have a tensile modulus greater than about 1200 MPa, for example greater than about 2000 MPa. Tensile modulus is typically less than about 10000 MPa.

[0096] This polymer composition can exhibit a strength greater than approximately 3 kJ / m 2 For example, greater than approximately 6 kJ / m 2 The impact strength of a notched simply supported beam at 23°C (ISO Test 179-1). The impact strength of a notched simply supported beam is typically less than about 20 kJ / m. 2 .

[0097] This disclosure can be better understood by referring to the following embodiments. Example

[0098] The following examples are provided to demonstrate some of the advantages and benefits of the polymer compositions manufactured in accordance with this disclosure.

[0099] Example 1

[0100] Various polymer compositions were formulated, molded into test samples, and formaldehyde emissions were tested. The polymer compositions contained formaldehyde copolymers. The polyoxymethylene polymer had a density of approximately 9 cm³ according to ISO Test 1133. 3 The melt volume rate is 10 min / min. In addition to the polyoxymethylene polymer, the polymer composition contains 0.25 wt% nucleating agent, 0.3 wt% antioxidant (unless otherwise specified, pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)), 0.18 wt% lubricant, and 0.07 wt% calcium 12-hydroxystearate. Additionally, the polymer composition contains 1 wt% black concentrate.

[0101] 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.

[0102] In the initial test group, formaldehyde emissions were tested in accordance with the 2011 China Government Test, test number GB / T27630-2011. However, instead of using the Tedlar bag sampling method to capture and evaluate formaldehyde emissions, a fixed-volume chamber was used. As used herein, this test will be referred to as the “Modified GB / T27630-2011 Test” and the procedure is as follows:

[0103] Changes to GB / T27630-2011 testing

[0104] Sample considerations:

[0105] The samples were POM specimens (54×79mm) molded according to VDA 275 specifications. Two specimens were used for each measurement. The specimens were conditioned at 23°C and 50% RH for 24±2 hours prior to analysis. Samples were analyzed within 15 days of molding.

[0106] Formaldehyde collection device:

[0107] The collection device is displayed Figure 4In the test, a 2-liter collection container was heated to 145–160°C via a heating mantle. Two POM samples were suspended by hooks and separated by a Teflon isolator. The temperature at the center of the sample was 65°C, with a 10°C variation along its vertical length. During the test, the container was purged with nitrogen at a rate of 500 mL / min. The gas entered the top of the container and exited through a DNPH derivatization tube at the distal end of the gas flow path. Formaldehyde emissions were collected for 2 hours, followed by sample removal and purging for 30 minutes before proceeding with the next test. The formaldehyde-DNPH tube was then washed with 5 mL of acetonitrile and analyzed by HPLC using the parameters listed below. Quantification was performed using a commercially available 13DNPH-derived aldehyde and ketone mixture (Cerilliant) (which includes formaldehyde-DNPH). Standards of 0.03–15 μg / mL were fitted using linear regression (R0.03). 2 >0.9999).

[0108] LC experimental conditions:

[0109] System: Dionex Ultimate 3000; LC4

[0110] Column: Phenomenex Kinetex C18 2.1×100mm, 2.6μm

[0111] SN#: H15-038929

[0112] Column temperature 40℃

[0113] Injection volume 2μL

[0114] Flow rate 0.400 mL / min

[0115] Detector wavelength 365nm

[0116] Detector bandwidth 10nm

[0117]

[0118]

[0119] Blank sample and control:

[0120] Unused DNPH traps were analyzed directly by HPLC without any exposure to the exposed vessel. This blank sample test produced no peaks, confirming that using only the DNPH trap resulted in zero background. A control run was also performed using the normal operating procedure but without any sample and subsequent vessel purging. The resulting peak was 0.12% of the area observed in typical samples. This indicates that a 30-minute purging is effective in removing emissions from the reactor vessel.

[0121] Three commercially available formulations were also tested. The first two commercially available formulations (reference 1 and reference 2) contained 0.5% by weight of benzoguanidine. The chemical composition of the third commercial sample was unknown. The following compositions were tested and the following results were obtained:

[0122] Table 1

[0123]

[0124]

[0125] As shown above, samples 11, 13 and 14 demonstrate a significant reduction in formaldehyde emissions, especially compared to compositions containing only guanidine compounds.

[0126] Then, another polyoxymethylene polymer composition was formulated and tested using the same formaldehyde emission test, along with benzoguanidine (BZG), arginine (ARG), and allantoin (ALT). The following results were obtained:

[0127] Table 2

[0128]

[0129] Then, another polyoxymethylene polymer composition containing a combination of benzoguanamine and allantoin was formulated. Additionally, two different deacidifying agents were tested. Specifically, calcium propionate was tested in addition to calcium 12-hydroxystearate.

[0130] The composition was then tested for formaldehyde emissions using different tests, and total volatile organic compounds (TVOCs) were also tested. The physical properties of the formulation were also tested. The first test for formaldehyde emissions was performed as described above. The second test for formaldehyde emissions was performed according to VDA Test 275. The test for total volatile organic compounds (TVOCs) was similar to the first formaldehyde emission test, performed using a fixed-volume chamber. However, the exhaust gas from this chamber was sent to a Tenac cartridge and analyzed by GC-MS.

[0131] Tensile modulus, yield tensile stress, and yield tensile strain were all tested at 23°C according to ISO Test 527. Impact strength of the notched simply supported beam was tested at 23°C according to ISO Test 179-1.

[0132] For comparative purposes, two control compounds were also tested. Control compound 1 was the same as in Table 1 above and contained 0.5% benzoguanidine. Control compound 4, on the other hand, was a commercially available product with unknown composition. The following results were obtained:

[0133] Table 3

[0134]

[0135] During testing, it should be noted that calcium propionate deacidifier is more compatible with colorant (1% carbon black concentrate) than calcium 12-hydroxystearate.

[0136] Example 2

[0137] Further tests were conducted using the formulation prepared according to this disclosure. These tests were the same as those described in Example 1 above. In this example, the polyoxymethylene polymer exhibited a high melt flow rate. Specifically, the polyoxymethylene polymer had a melt flow rate of 27 cm⁻¹. 3 The melt flow rate was 10 min. The composition was identical to that of Example 1, except that the UV stabilizer dosage was 0.4%, the lubricant dosage was 0.5%, and calcium propionate was used instead of calcium 12-hydroxystearate. However, Control 5 used 0.05% tricalcium citrate instead of calcium propionate and 0.2% lubricant instead of 0.18% lubricant.

[0138] In this test, different colorant packets were introduced into the polymer composition and 0.5% of different hindered amine light stabilizers (HAL) were used. This formulation was compared with control 5, which contained the same polyoxymethylene polymer and 0.5% by weight benzoguanidine. Control 5 and sample 22 were produced on a twin-screw extruder, and samples 23-28 were produced on a single-screw compounding mill. The following results were obtained:

[0139] Table 4

[0140]

[0141] Example 3

[0142] The other compositions were tested using the same base resin and additives as in Example 1. Table 5 shows further results regarding the synergistic effect of arginine (ARG) and benzoguanidine (BZG) on POM emission performance. Control 6 contained 0.5% benzoguanidine. Samples 29, 30, and 31 contained arginine alone, a combination of arginine and benzoguanidine, and benzoguanidine alone, respectively, at the same loading level (i.e., 0.6%). Compared to the arginine alone or benzoguanidine alone samples, the combination of 0.1% arginine and 0.5% benzoguanidine exhibited significantly lower formaldehyde (FA) emissions (by altering both the GB method and the VDA275 method) and TVOC emissions. This indicates a synergistic effect between arginine and benzoguanidine in formaldehyde removal. Compared with the control, the combination of 0.1% arginine and 0.5% benzoguanidine demonstrated improvements in formaldehyde emissions to approximately 1 / 5.8 (by modified GB test), to 1 / 2 (by VDA275 method), and to approximately 1 / 11 in TVOC emissions.

[0143] Table 5

[0144]

[0145] Example 4

[0146] The other compositions were tested using the same base resin and additives as in Example 1. Table 6 shows example combinations of allantoin (ALT) and arginine and their emission performance. Control 7 is a POM sample that does not contain formaldehyde scavengers such as benzoguanamine, allantoin, or arginine. Sample 32 comprises a combination of 0.1% allantoin and 0.1% arginine. By adding the combination of 0.1% allantoin and 0.1% arginine to the POM of Control 7, formaldehyde emissions decreased to approximately 1 / 145 (via modified GB test) and 1 / 26 (via VDA275). This is better than Control 6 in terms of formaldehyde emissions, to approximately 1 / 25 (via modified GB test) and 1 / 1.1 (via VDA275).

[0147] Table 6

[0148]

[0149] Benzoguanidine may be unsuitable for some applications; for example, various regulations may restrict the amount of benzoguanidine used in specific products. Conversely, arginine (L-arginine, CAS#74-79-3) is an amino acid, and allantoin (CAS#97-59-6) is widely used in cosmetic and pharmaceutical applications. Using less restricted ingredients such as allantoin and arginine not only achieves better performance than existing solutions but also expands the application of low-emission POMs, such as for strictly regulated products.

[0150] Example 5

[0151] The other compositions were tested using the same base resin and additives as in Example 1, except that samples 34-36 were tested with a melt volumetric flow rate of approximately 8 cm⁻¹. 3The production of substituted POM polymers at 10 min (according to ISO Test 1133) and samples 35 and 36 contained 1% black concentrate. Formaldehyde emission performance of combinations of allantoin, arginine, and benzoguanamine was also investigated. The following mixtures were considered: allantoin at loadings of 0%, 0.075%, 0.15%, and 0.225%; arginine at loadings of 0%, 0.05%, 0.075%, 0.15%, and 0.225%; benzoguanamine at loadings of 0%, 0.25%, 0.5%, and 0.75%; and combinations thereof. Some examples from this study are shown in Table 7. Among the samples studied, the combination of 0.1% allantoin, 0.15% arginine, and 0.5% benzoguanamine (samples 34 and 36) performed best in terms of formaldehyde and TVOC emissions.

[0152] Table 7

[0153]

[0154] Two natural-colored samples and a sample stained with a mixture of 1% black concentrate were tested. Compared to control 6, the combination in the natural-colored POM sample showed a reduction in formaldehyde emissions to approximately 1 / 87 (by modified GB test), a reduction in formaldehyde emissions to 1 / 15 (by VDA275), and a reduction in TVOC emissions to 1 / 230. Compared to the control, the same combination in the black sample showed a reduction in formaldehyde emissions to 1 / 173 (by modified GB test), a reduction in formaldehyde emissions to 1 / 6.3 (by VDA275), and a reduction in TVOC emissions to 1 / 230. The natural-colored sample (sample 34) with 0.1% allantoin, 0.15% arginine, and 0.5% benzoguanamine showed a significant yellowing compared to typical unfilled POM. The black sample (sample 36) remained usable because the yellowing caused by the additives was masked by the black pigment.

[0155] The combination of 0.1% allantoin, 0.05% arginine, and 0.5% benzoguanamine exhibited the second-best formaldehyde emission removal performance. In the natural-colored sample (Sample 33), this combination showed a reduction in formaldehyde emissions to approximately 1 / 22 (by modified GB test), approximately 1 / 1.4 (by VDA275), and TVOC to 1 / 230 compared to control 6. In the black sample (Sample 35), the same combination showed a reduction in formaldehyde emissions to approximately 1 / 29 (by modified GB test), approximately 1 / 5 (by VDA275), and TVOC to 1 / 115 compared to the control. While these results represent a significant improvement over the control and the aforementioned combinations, these samples demonstrate slightly higher formaldehyde emissions than 0.1% allantoin, 0.15% arginine, and 0.5% benzoguanamine, while being slightly more yellow than typically unfilled POM.

[0156] Example 6

[0157] Compositions of 0.1% allantoin, 0.05% arginine, and 0.5% benzoguanamine, and compositions of 0.1% allantoin, 0.15% arginine, and 0.5% benzoguanamine, were both tested in UV-stabilized formulations containing 0.5% HAL (phenol UV stabilizer), polyethylene glycol, and POM (grey, brown, and black). Emission levels obtained by modified GB tests ranged from 0.05 ppm to 0.1 ppm, representing improvements of 1 / 20 to 1 / 40 compared to the control. Formaldehyde emissions obtained by the VDA275 method were improved to approximately 1 / 5 compared to the control.

[0158] Example 7

[0159] The other compositions were tested using the same base resin and additives as those used in Sample 34 of Example 5, except that the level of antioxidant was increased to 0.4%. In the following examples, the combination of 0.1% allantoin, 0.05% arginine, and 0.5% benzoguanidine was further optimized to lighten the yellowing and improve the emission performance of Sample 33. Some examples are shown in Table 8.

[0160] Table 8

[0161]

[0162]

[0163] In Sample 37, the antioxidant (AO) loading was increased to 0.4% in this study, in contrast to Sample 33. Formaldehyde emissions from Sample 37 were reduced to approximately 1 / 2.4 (by modified GB testing) and 1 / 6.7 (by VDA275) compared to Sample 33. The same antioxidant loading levels were also used in Samples 38 and 39, and both samples included a 0.01% loading of fluorescent whitening agent (OB). Sample 38 used AO-2 (ethylene bis(oxyethylene)bis-(3-(5-tert-butyl-4-hydroxym-tolyl)propionate)) and Sample 39 used AO-1 (pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)) as the antioxidant.

[0164] Samples 38 and 39 demonstrate a slightly improved level of similar emissions compared to sample 37. When a fluorescent whitening agent is used, the yellowing of the composition of 0.1% allantoin, 0.05% arginine, and 0.5% benzoguanamine is improved, as indicated by the “b” grade in LAB color measurements.

[0165] However, after 1000 hours of exposure to fluorescence, the color shift in samples 38 and 39 was noticeable because the fluorescent whitening agent lost its effect. Initially, sample 56 was more yellow than samples 38 and 39, but showed no color shift because it lacked a fluorescent whitening agent. Sample 56 exhibited significantly improved formaldehyde emission performance. Sample 56 possessed acceptable yellowing (though not optimal) and good formaldehyde emission performance, and can be used as a general-purpose, medium-flow, very low-emission POM.

[0166] Example 8

[0167] Some scavenging agents (e.g., those that may use 0.5% benzoguanamine) are generally not used in certain grades of POM, such as those in which the impact modifier thermoplastic polyurethane (TPU) is conjugated to the POM. Benzoguanamine is believed to interfere with the coupling reaction between TPU and POM in some cases. To achieve lower formaldehyde emissions in such POM grades, higher antioxidant loadings have been used. The possibility of using a combination of allantoin and arginine in such grades was investigated using the grade represented by Control 8, as shown in Table 9. Control 9 is a low-emission form of Control 8, achieved not by 0.5% benzoguanamine, but by a 0.5% antioxidant loading. Unless otherwise indicated, this composition comprises 18% TPU, 0.2% antioxidant, 0.15% lubricant, 0.5% diisocyanate coupling agent, and the balance percentage of POM resin.

[0168] When allantoin or arginine was used alone at 0.1%, formaldehyde emissions were significantly reduced compared to the control. The reduction in formaldehyde was pronounced when the combination of allantoin and arginine was used. The combination of 0.05% allantoin and 0.05% arginine (sample 42) demonstrated almost half the formaldehyde emission level compared to 0.1% loadings of either allantoin or arginine alone, showing a synergistic effect of the combination. The combination of 0.075% allantoin and 0.075% arginine (sample 43) showed a reduction in formaldehyde emissions to 1 / 80 (by modified GB test) and approximately 1 / 9.4 (by VDA275).

[0169] Table 9

[0170]

[0171] Example 9

[0172] The efficiency of ethylene urea (EU) as a formaldehyde scavenger was evaluated using 0.1% loaded ethylene urea in a POM composition, using the same base resin and additives used in Sample 34 of Example 5. Table 10 shows the formaldehyde emission results with the addition of 0.1% ethylene urea to POM with three different hydrations and purities. As shown in Table 10, ethylene urea at a 0.1% loading is highly effective in reducing formaldehyde emissions. By a modified GB test method, the formaldehyde emissions of the 99% pure hemihydrated ethylene urea-containing sample (Sample 44) were as low as 1 / 12 compared to control 10. By the VDA275 method, the formaldehyde emissions of the same sample were approximately 1 / 2.5 lower than control 10. When comparing Sample 44 and Sample 46, the formaldehyde emissions were lower when using the hemihydrate compared to the anhydrous formaldehyde; however, both were effective in formaldehyde scavenging. Without being limited to any particular theory, hydration may help the nitrogen in ethylene urea become more electrophilic to accept formaldehyde.

[0173] Table 10

[0174]

[0175] Example 10

[0176] Further examples were conducted to investigate the efficiency of ethylurea as a formaldehyde scavenger in the presence of other scavengers in a POM composition using the same base resin and additives as used in Sample 34 of Example 5. The ethylurea used in this example was in a 99% pure hemihydrate form. Sample 55 replaced the antioxidant with 0.4% AO-2 and omitted calcium 12-hydroxystearate.

[0177] Table 11 shows some exemplary combinations and results of formaldehyde removers. It appears that the addition of ethylurea significantly reduces formaldehyde emission levels, for example, compared to the results of its counterparts alone. Optimal emission performance was achieved when all four formaldehyde removers were used (sample 49). However, yellowing was noticeable in sample 49.

[0178] Sample 55 is similar to Sample 56, but with 0.05% arginine replaced by 0.05% ethylurea. The formaldehyde emission performance of Sample 55 is similar to that of Sample 56 (by modified GB testing), but almost twice as high by VDA275. This could be because arginine is particularly effective in removal under VDA275 emission test conditions. However, it is noteworthy that Sample 55 exhibits significantly better performance in terms of color: its yellowing is comparable to the sample without a formaldehyde remover (Sample 47). It appears that the ethylurea loading level in Sample 55 could be further optimized to achieve formaldehyde emission levels similar to Samples 38, 39, or 56 without compromising the yellowing.

[0179] Table 11

[0180]

[0181] Example 11

[0182] Further tests were conducted to characterize the efficiency of ethyl urea in combination with other formaldehyde scavengers.

[0183] The samples were prepared as follows. Control 11 and samples 57-60 contained polyoxymethylene polymer 1 (POM-1) with a dissolved oxygen content of 5.6%. Control 12 and samples 61-64 contained polyoxymethylene polymer 2 (POM-2) with a dissolved oxygen content of 2.8%. Specifically, POM-2 had a dissolved oxygen content of 2.2 cm⁻¹ as measured according to ISO 1133. 3 Melt flow rate per 10 min.

[0184] Reference 12 and samples 61-64 also contained 4.5% polyvinyl acrylonitrile-styrene copolymer.

[0185] Each sample and control included 0.25% polyoxymethylene terpolymer as a nucleating agent, ethylene bis(oxyethylene)bis-(3-(5-tert-butyl-4-hydroxym-tolyl)propionate) as an antioxidant (AO), 0.2% ethylene bis(stearamide), and 0.05% tricalcium citrate. Additional additives were included in the amounts shown in Table 12.

[0186] Table 12

[0187] Composition Control 11 AO 0.25%, BZG 0.5% Control 12 AO 0.3%, BZG 0.5% Sample 57 AO 0.25%, EU 0.1% Sample 58 AO 0.25%, BZG 0.5%, EU 0.1% Sample 59 AO 0.25%, EU 0.1%, ALT 0.1% Sample 60 AO 0.25%, BZG 0.5%, EU 0.1%, ALT 0.1% Sample 61 AO 0.3%, EU 0.1% Sample 62 AO 0.3%, BZG 0.5%, EU 0.1% Sample 63 AO 0.3%, EU 0.1%, ALT 0.1% Sample 64 AO 0.3%, BZG 0.5%, EU 0.1%, ALT 0.1%

[0188] The test results are provided in Table 13.

[0189] Table 13

[0190]

[0191] The above results demonstrate the synergistic emission reduction effect of the combination of ethylurea with benzoguanidine and / or allantoin. This effect is particularly significant at higher temperatures.

[0192] These and other changes and variations of this disclosure can be practiced by those skilled in the art without departing from the spirit and scope of the invention, which is set forth more specifically in the appended claims. Furthermore, it should be understood that various 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 exemplary and is not intended to limit the invention as further described in such appended claims.

Claims

1. A polymer composition, comprising: A polyoxymethylene polymer; and A formaldehyde stabilizer package for reducing formaldehyde emissions, the formaldehyde stabilizer package comprising a blend of emission control agents, wherein the blend comprises: (1) A substituted hydantoin, a guanamine compound, and an amino acid, wherein the substituted hydantoin is present in the polymer composition in an amount less than 0.5% by weight and greater than 0.001% by weight; or (2) Ethylene urea, a guanamine compound, and allantoin, ethylene urea being present in the polymer composition in an amount from 0.001% by weight to 5% by weight, and The guanamine compound is present in a weight ratio of 20:1 to 2:1 relative to other emission control agents, and is present in the composition in an amount greater than 0.2% by weight and less than 2% by weight.

2. The polymer composition as defined in claim 1, wherein the formaldehyde stabilizer package comprises a blend of a substituted hydantoin, a guanamine compound, and an amino acid, the substituted hydantoin comprising allantoin.

3. The polymer composition as defined in claim 1, wherein the formaldehyde stabilizer package comprises a blend of: ethylene urea, a guanamine compound, and allantoin.

4. The polymer composition as defined in claim 1, wherein the amino acid comprises arginine.

5. The polymer composition as defined in claim 1, wherein the guanamine compound comprises benzoguanamine.

6. The polymer composition as defined in claim 1, wherein the polymer composition exhibits a formaldehyde emission of less than 5 ppm when tested according to VDA Test 275.

7. The polymer composition as defined in claim 1, wherein the polymer composition exhibits a formaldehyde emission of less than 4 ppm when tested according to VDA Test 275.

8. The polymer composition as defined in claim 1, wherein the polymer composition exhibits a formaldehyde emission of less than 3 ppm when tested according to VDA Test 275.

9. The polymer composition as defined in claim 1, wherein the polymer composition further comprises a nucleating agent in an amount of 0.05% by weight to 1% by weight, an antioxidant in an amount of 0.05% by weight to 2% by weight, and a lubricant in an amount of 0.05% by weight to 1.5% by weight.

10. The polymer composition as defined in claim 2, wherein the guanamine compound is present in the polymer composition in an amount of 0.3% by weight to 0.8% by weight, and wherein the substituted hydantoin is present in the polymer composition in an amount of 0.01% by weight to 0.3% by weight.

11. The polymer composition as defined in claim 1, wherein the polymer composition has a tensile modulus of at least 1200 MPa at 23 °C when tested according to ISO Test 527, a yield tensile strain greater than 7% at 23 °C when tested according to ISO Test 527, and a Charpy impact strength of greater than 3 kJ / m 2 at 23 °C when tested according to ISO Test 179-1. 2 of the notched Izod impact strength.

12. A molded article made from the polymer composition according to any one of claims 1 to 11.

13. The molded article as defined in claim 12, wherein the molded article comprises a medical product.

14. The molded article as defined in claim 13, the medical product comprising an inhaler or a syringe.

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