Polyoxymethylene polymers incorporating aldehyde scavengers

Abstract

A method for reducing the aldehyde content in a polyoxymethylene (POM) polymer includes contacting the POM polymer, or a monomer, oligomer, or prepolymer involved in preparing the POM polymer, with a liquid formulation, the liquid formulation including a liquid carrier and an aldehyde scavenger.

Description

[Technical Field]

[0001] The present invention relates to polymeric materials, particularly but not exclusively polyoxymethylene (POM), in which aldehydes may be undesirably associated, for example, by generation during manufacture, downstream melt processing and / or during use. [Background technology]

[0002] Polyoxymethylene (POM), also known as acetal, polyacetal, or polyformaldehyde, is a polymer that contains linear ether structures (CHO-) along its backbone. n This linearity is due to the high crystallinity, which can be up to 80%, and the viscosity of the polymer, which is 1.410-1.420 g / cm 3 In some cases, POM may be filled with, for example, glass or carbon fibers.

[0003] POMs are increasingly being used in numerous applications, including electrical and electronic equipment, consumer products, automotive and industrial machinery, medical devices, and building and construction.

[0004] POM may be sold as a copolymer or a homopolymer. Homopolymer POM has the following structure: [ka]

[0005] It consists essentially of the repeating units described above.

[0006] The copolymer POM comprises the following repeating units: [ka]

[0007] It consists essentially of the repeating units described above.

[0008] Both homopolymer and copolymer POMs use methanol as the primary base material. For POM homopolymers, formaldehyde is synthesized by air oxidation of methanol, followed by the formation of acetal resins using an ionic initiator. The replacement of hydroxyl groups at the polymer chain ends with ester groups stabilizes the resin in POM homopolymers. POM copolymers are generally produced using trioxane (also produced starting from methanol) as a raw material. Approximately 2-3% epoxy compounds are copolymerized with trioxane to obtain stable POM copolymers. Chain-end capping may also be used. POM copolymer resins have greater stability but suffer from reduced crystallinity as a result of the interspersed carbon-carbon bond groups in their polymer chains. This polymer structure also confers excellent resistance to alkalis, hot water, and other chemicals, as well as long life at high temperatures and greater tolerance in processing conditions. Meanwhile, their tensile strength, stiffness, softening point, and melting point are all lower than those of acetal homopolymers.

[0009] Polyoxymethylene (POM) is inherently unstable and prone to polymer degradation. POM degradation occurs via chain scission or end-group decomposition. Common degradation products are formaldehyde, formic acid, cyclic acetals, and oligomers. Melt processing of POM causes polymer degradation and results in the production of formaldehyde. Formaldehyde emissions lead to workplace safety issues during polymer processing, limiting the use of this polymer in applications where air quality is critical, such as automotive applications.

[0010] Formaldehyde produced by polymer degradation can oxidize to formic acid and contribute to the hydrolysis of polymer chains. Apart from formaldehyde emissions, POM degradation can also result in mold deposits, loss of mechanical properties, and discoloration.

[0011] POM resins can also be susceptible to acid hydrolysis by mineral acids. For example, even low levels of chlorine in drinking water can lead to environmental stress cracking. Therefore, POM parts are stabilized to mitigate this degradation.

[0012] It is known to take measures to stabilize POM and reduce aldehyde emissions. For example, stabilizing measures may be applied during the final stage of POM production or during melt processing to form articles or masterbatches. Approaches developed to prevent POM degradation include the use of phenolic antioxidants to limit oxidative degradation, lubricants to reduce shear forces, acid scavengers to prevent formic acid hydrolysis, scavengers to react with free formaldehyde, endcapping to improve stability, light stabilizers, and / or comonomers.

[0013] Although various types of stabilization packages are commercially available, it is difficult to meet material emission targets such as the VDA-275 target of 2 ppm for automotive applications, as well as global emission targets such as VDA-277 or VDA-278. Most treatments disclosed in the prior art aimed at controlling formaldehyde either do not meet the VDA-275 target, or, to meet it, require uneconomical addition levels, impart discoloration, and / or adversely affect the properties of POM. Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention is to address the problems associated with aldehydes in POM.

[0015] It is an object of the present invention to address one or more of the above problems. [Means for solving the problem]

[0016] According to a first aspect of the present invention, there is provided a method for reducing the aldehyde, e.g., formaldehyde, content in a polyoxymethylene (POM) polymer, the method comprising the step of contacting the POM polymer, or a monomer, oligomer, or prepolymer involved in the preparation of the POM polymer, with a liquid formulation, the liquid formulation comprising a liquid carrier and an aldehyde scavenger.

[0017] References herein to reducing aldehydes appropriately refer primarily to formaldehyde, which, as noted, is particularly problematic with POM.

[0018] Preferably, the method comprises the step of contacting a POM polymer with the liquid formulation.

[0019] The described liquid formulations have been unexpectedly found to be advantageous over equivalent solid formulations, allowing for lower levels of aldehyde scavengers to be delivered to POM and / or for aldehyde emissions to be more easily reduced to levels that meet relevant material emission targets such as VDA-275.

[0020] References herein to the state of a material (e.g., liquid) refer to the state at standard temperature and pressure (STP). Thus, the liquid formulation is preferably liquid at STP, and the liquid carrier is preferably liquid at STP.

[0021] The POM suitably comprises -(CHO)- repeat units (referred to as "repeating unit X"). The POM may also comprise -(CHCHO)- repeat units (referred to as "repeating unit Y"). Preferably, in the POM, the sum of the mole percent of repeat units X and Y is at least 80 mole percent, preferably at least 90 mole percent, more preferably at least 95 mole percent, and especially about 100 mole percent.

[0022] In said POM, suitably the weight percent of the POM polymer made up of repeat units X and Y is at least 80 wt%, preferably at least 90 wt%, more preferably at least 95 wt%, especially at least 98 wt%.

[0023] The POM may suitably be a homopolymer POM consisting essentially of repeating unit X, or may be a copolymer POM which may comprise, or preferably consist essentially of, repeating units X and Y.

[0024] The aldehyde scavenger can be any chemical that reduces aldehydes in the process, for example by reacting with the aldehydes, and thus the amount of aldehyde associated with the POM in the presence of the aldehyde scavenger is preferably less than in the absence of the scavenger.

[0025] In one embodiment, a preferred aldehyde scavenger comprises both an amine moiety and an amide moiety. In one embodiment, a preferred aldehyde scavenger comprises a substituted phenyl moiety. In one preferred embodiment, the aldehyde scavenger may comprise an amine moiety (especially -NH), an amide moiety (especially -CONH), and a substituted phenyl moiety. In this case, it is preferred that both the amine moiety and the amide moiety are directly bonded to the phenyl moiety. Preferably, the amine moiety and the amide moiety are bonded ortho to each other.

[0026] One class of aldehyde scavengers (referred to as Scavenger AS1) may include polyamides selected from the group consisting of low molecular weight partially aromatic polyamides having a number average molecular weight of less than 15,000, low molecular weight aliphatic polyamides having a number average molecular weight of less than 7,000, and combinations thereof. Preferred low molecular weight partially aromatic polyamides include poly(m-xylylene adipamide), poly(hexamethylene isophthalamide), poly(hexamethylene adipamide-co-isophthalamide), poly(hexamethylene adipamide-co-terephthalamide), and poly(hexamethylene isophthalamide-co-terephthalamide). The most preferred low molecular weight partially aromatic polyamide is poly(m-xylylene adipamide) having a number average molecular weight of 4,000 to 7,000 and an intrinsic viscosity of 0.3 to 0.6 dL / g. Preferred low molecular weight aliphatic polyamides include poly(hexamethylene adipamide) and poly(caprolactam). The most preferred low molecular weight aliphatic polyamide is poly(hexamethylene adipamide) having a number average molecular weight of 3,000 to 6,000 and an intrinsic viscosity of 0.4 to 0.9 dL / g.

[0027] Another class of aldehyde scavengers (referred to as Scavenger AS2) may comprise at least two component molecular fragments, each containing at least two hydrogen-substituted heteroatoms bonded to a carbon of the respective component molecular fragment. Each of the component molecular fragments of the organic additive compound is reactive with an aldehyde in the polyester to form water and a resulting organic molecular fragment containing an unbridged five- or six-membered ring containing the at least two heteroatoms. Preferably, the organic additive compound has a molecular weight at least twice that of the component molecular fragments alone. Heteroatoms present in each molecular fragment capable of reacting with the aldehyde include oxygen (O), nitrogen (N), and sulfur (S). The heteroatoms of the component molecular fragments suitably have at least one bond to an active hydrogen (H) to split off water during condensation with the aldehyde. Preferred heteroatom-containing functional groups include amine (NH2 and NHR), hydroxyl (OH), carboxyl (CO2H), amide (CONH2 and CONHR), sulfonamide (SON2NH2), and thiol (SH). These functional groups should be sterically arranged so as to form unbridged five- or six-membered rings upon condensation with an aldehyde. Preferably, the structural arrangement allows for the formation of a six-membered ring. It is particularly preferred that the heteroatoms of the organic additive are bonded to a preformed ring(s). Most preferably, the preformed ring is aromatic, and the unbridged five- or six-membered rings of the resulting organic compound are bonded to this aromatic ring. Suitable organic additive compounds may also be substantially thermally stable at temperatures required for melt processing of polyesters. It is also preferred that the functional groups present on the organic additive are relatively unreactive toward ester linkages present in the polyester.Examples of preferred scavengers include 1,2-bis(2-aminobenzamidoyl)ethane, 1,2-bis(2-aminobenzamidoyl)propane, 1,3-bis(2-aminobenzamidoyl)propane, 1,3-bis(2-aminobenzamidoyl)pentane, 1,5-bis(2-aminobenzamidoyl)hexane, 1,6-bis(2-aminobenzamidoyl)hexane, and 1,2-bis(2-aminobenzamidoyl)cyclohexane. More preferred are scavengers whose constituent molecular fragments are derived from anthranilamide.

[0028] Another class of aldehyde scavengers suitable for use in the present invention (referred to as Scavenger AS3) includes anthranilamide, 1,8-diaminonaphthalene, allantoin, 3,4-diaminobenzoic acid, malonamide, salicylanilide, uracil, 6-amino-1,3-dimethyluracil (DMU), 6-aminoisocytosine, 6-aminouracil, 6-amino-1-methyluracil, α-tocopherol, triglycerin, trimethylolpropane, dipentaerythritol, tripentaerythritol, D-mannitol, D-sorbitol, and xylitol. From the above group, anthranilamide, 1,8-diaminonaphthalene, allantoin, 3,4-diaminobenzoic acid, malonamide, salicylanilide, 6-amino-1,3-dimethyluracil (DMU), 6-aminoisocytosine, 6-aminouracil, 6-amino-1-methyluracil are preferred.

[0029] Another class of aldehyde scavengers (referred to as Scavenger AS4) may include hydroxyl compounds selected from aliphatic hydroxyl compounds containing at least two hydroxyl groups, aliphatic-alicyclic compounds containing at least two hydroxyl groups, and alicyclic hydroxyl compounds containing at least two hydroxyl groups.

[0030] The hydroxyl compounds preferably contain from 3 to about 8 hydroxy groups, which may contain one or more substituents such as ether, carboxylic acid, carboxylic acid amide or carboxylic acid ester groups.

[0031] Preferred hydroxyl compounds include those having a pair of hydroxyl groups attached to respective carbon atoms separated from each other by at least one atom, and particularly preferred hydroxyl compounds have a pair of hydroxyl groups attached to respective carbon atoms separated from each other by one carbon atom.

[0032] Examples of suitable hydroxyl compounds include diols, such as ethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,2-diol, 2-methylpentane-2,4-diol, 2,5-dimethyl-hexane-2,5-diol, cyclohexane-1,2-diol, cyclohexane-1,1-dimethanol, diethylene glycol, triethylene glycol, and polyethylene glycols, for example, having a molecular weight of about 800 to about 2000, such as Carbowax™ 1000, having a molecular weight of about 950 to about 1050 and containing about 20 to about 24 ethyleneoxy groups per molecule; triols, such as glycerol, trimethylolpropane, 2,3-di-(2′-hydroxyethyl)-cyclohexane-1-ol, hexane-1,2,6-triol, 1, 1,1-Tris-(hydroxymethyl)ethane, 3-(2'-hydroxyethoxy)-propane-1,2-diol, 3-(2'-hydroxypropoxy)-propane-1,2-diol, 2-(2'-hydroxyethoxy)-hexane-1,2-diol, 6-(2'-hydroxypropoxy)-hexane-1,2-diol, 1,1,1-tris-[(2'-hydroxyethoxy)-methyl]-ethane, 1,1,1-tris-[(2 '-hydroxypropoxy)-methyl]-propane, 1,1,1-tris-(4'-hydroxyphenyl)-ethane, 1,1,1,-tris-(hydroxyphenyl)-propane, 1,1,3-tris-(dihydroxy-3-methylphenyl)-propane, 1,1,4-tris-(dihydroxyphenyl)-butane, 1,1,5-tris-(hydroxyphenyl)-3-methylpentane, trimethylolpropane ethoxylates of the formula: [ka] where n is an integer, or trimethylolpropane propoxylate of the formula: [ka] (where n is an integer), for example, trimethylolpropane propoxylate having a molecular weight of about 1000; polyols such as pentaerythritol, dipentaerythritol, and tripentaerythritol; and sugars such as cyclodextrin, D-mannose, glucose, galactose, sucrose, fructose, xylose, arabinose, D-mannitol, D-sorbitol, D- or L-arabitol, xylitol, iditol, talitol, allitol, altritol, guilitol, erythritol, threitol, and D-gulonic acid-Y-lactone; and the like. Mixtures of two or more such compounds can be used. Particularly preferred are aliphatic hydroxy compounds containing 3 to about 8 hydroxy groups.

[0033] Another class of aldehyde scavengers (called Scavenger AS5) is (I) The following part [ka] and the following part NH (B) wherein a carbon atom of portion (A) and a nitrogen atom of portion (B) are separated by at least one atom and not more than two atoms; (II) The following part [ka] and the following part NH (B) wherein a carbon atom of portion (A) and a nitrogen atom of portion (B) are separated by at least one atom and not more than two atoms; (III) The following part [ka] and the following part NH (B) and a third fragment containing The compound (A) comprises:

[0034] The first fragment may comprise the following portion: [ka] In the formula, R' represents a substituent, n1 is 0 to 4, for example, 0 to 1, and preferably n1 is 0. R' represents an optionally substituted alkyl group, for example, an optionally substituted C 1~20 , e.g. C 1~10 It may be an alkyl group. R' may be configured to improve the compatibility of compound (A) in the polymeric material with which it comes into contact in the method, for example by R' containing an associated functional group to improve compatibility. Alternatively and / or additionally, R' may be configured to increase the mass of compound (A).

[0035] The moiety (B) in the first fragment is preferably NH2, and / or the NH moiety attached to the benzene moiety is preferably NH2.

[0036] Moiety (C) is suitably capable of reacting with an aldehyde in a condensation reaction to produce the moiety: [ka] where the bond with * represents the attachment of moiety (D) to another portion of compound (A) and the bond with ‡ represents the portion of the aldehyde that reacts with moiety (C). Once the level of aldehyde is reduced in the process, compound (D) may be of the formula: [ka]

[0037] As a result, the aldehyde is captured by the above reaction and its residue is covalently bonded to compound (A).

[0038] The second fragment may comprise the following portion: [ka] In the formula, R' represents a substituent, n1 is 0 to 4, for example, 0 to 1, and preferably n1 is 0. R' represents an optionally substituted alkyl group, for example, an optionally substituted C 1~20 , e.g. C 1~10 It may be an alkyl group. R' may be configured to improve the compatibility of compound (A) in the polymeric material with which it is contacted in the method, for example by R' containing an associated functional group to improve compatibility. Alternatively and / or additionally, R' may be configured to increase the mass of compound (A).

[0039] The portion (B) of the second fragment is preferably NH2, and / or the NH moiety attached to the benzene moiety is preferably NH2.

[0040] The third fragment may comprise: [ka] In the formula, R' represents a substituent, n1 is 0 to 4, for example, 0 to 1, and preferably n1 is 0. R' represents an optionally substituted alkyl group, for example, an optionally substituted C 1~20 , e.g. C 1~10 It may be an alkyl group. R' may be configured to improve the compatibility of compound (A) in the polymeric material with which compound (A) is contacted in the method, for example by R' containing an associated functional group to improve compatibility. Alternatively and / or additionally, R' may be configured to increase the mass of compound (A). Moiety (B) of the third fragment is preferably NH2, and / or the NH moiety attached to the benzene moiety is preferably NH2.

[0041] The first fragment, the second fragment, and the third fragment are preferably bonded to the main fragment of compound (A) via the nitrogen atom of the CO.NH moiety of each of the first fragment, the second fragment, and the third fragment. In a preferred embodiment, compound (A) consists essentially of the first fragment, the second fragment, the third fragment, and the main fragment.

[0042] The main fragment may contain only carbon atoms, hydrogen atoms, and optionally nitrogen atoms.

[0043] Preferably, the main fragment is substantially free of primary amine moieties (-NH2), except, optionally, for primary amine moieties (-NH2) separated from a carbonyl moiety (C=O) by at least one atom and not more than two atoms.

[0044] Optionally, the main fragment may contain one or more secondary or tertiary amine moieties. Except for any aromatic carbon atoms and carbonyl moieties, the main fragment preferably does not contain any unsaturated carbon atoms. The main fragment preferably does not contain any alkenyl or alkynyl groups.

[0045] A preferred capture agent AS5 comprises the structure detailed below. [ka] wherein M represents a main fragment comprising atoms selected from carbon, hydrogen, oxygen, and nitrogen atoms. More preferably, M represents a main fragment comprising atoms selected from carbon, hydrogen, and nitrogen atoms. This main fragment may comprise a saturated hydrocarbon moiety, such as a secondary amine moiety, which may incorporate a nitrogen atom.

[0046] Another class of aldehyde scavengers (referred to as scavengers AS6) is a compound XX comprising at least three moieties of the formula: [ka] wherein each moiety (AA) comprises an amine moiety (-NH) attached ortho or meta to an amide moiety (-CONH); Each R 1 each independently represents a substituent, and m is an integer of 0 to 4. The three moieties (AA) are bonded through their respective amide nitrogen atoms to respective carbon atoms of the main fragment, which contains only carbon and hydrogen atoms and is saturated. Contains compound XX.

[0047] One R 1 Or each R 1 may be selected from a halogen atom, or an optionally substituted hydrocarbon group, an alkoxy group, an amine group, an amide group, a phenol group, or a carboxylic acid group. The optionally substituted hydrocarbon may be substituted with one or more halogen atoms, or with an alkoxy group, an amine group, an amide group, a phenol group, or a carboxylic acid group. The optionally substituted hydrocarbon is preferably unsubstituted.

[0048] One R 1 Or each R 1 is an optionally substituted, preferably unsubstituted alkyl group, such as an optionally substituted, preferably unsubstituted C 1~20 , e.g. C 1~10 It may be an alkyl group. 1 For example, R can be used to add related functional groups to improve compatibility. 1 may be configured to improve the compatibility of compound XX in polymeric materials in which compound XX may be incorporated.

[0049] The or each m may be 0 or 1. Preferably, each m is 0. That is, other than the amine and amide moieties, each moiety (A) is unsubstituted.

[0050] Preferably, in compound XX, at least one moiety (AA) comprises an amine moiety (-NH2) attached ortho to an amide moiety (-CONH). Preferably, in each moiety (AA) in compound XX, the amine moiety is attached ortho to the amide moiety. In this case, preferably, m=0.

[0051] Preferably, the main fragment does not contain any cyclic or aromatic moieties. Preferably, the main fragment contains straight or branched chains.

[0052] The main fragment may contain 3 to 20 carbon atoms. Preferably, the main fragment contains 5 to 15 carbon atoms, more preferably 7 to 12 carbon atoms, and especially 8 to 10 carbon atoms. If the number of carbon atoms is n, the number of hydrogen atoms may be equal to 2n-1. Preferably, the main fragment contains 5 to 39 hydrogen atoms. Preferably, the main fragment contains 9 to 29 hydrogen atoms, more preferably 13 to 23 hydrogen atoms, and especially 15 to 19 hydrogen atoms.

[0053] In a preferred embodiment, the major fragment is C9H 17 It is a part.

[0054] The main fragment may comprise a linear chain containing 6 to 14 carbon atoms, preferably 6 to 10 carbon atoms, which may contain branching points to which chains containing 1 to 4 carbon atoms are attached.

[0055] The main fragment has the following general formula: [ka] where p, q and r are suitably integers in the range 1 to 10, preferably 1 to 5. Preferably, p is in the range 2 to 4, q is in the range 1 to 3 and r is in the range 2 to 6.

[0056] Preferably, the sum of the integers p, q and r is at least 4, preferably at least 6, more preferably at least 7. The sum may be less than 20, preferably less than 15, more preferably less than 10.

[0057] In compound XX, preferably the nitrogen atoms of the amide moiety (-CONH) are separated by at least 2, preferably at least 4, carbon atoms, and suitably not more than 10, for example not more than 7, carbon atoms.

[0058] The compound XX is represented by the following formula: [ka] where p, q and r are as defined above.

[0059] The compound XX is preferably [ka] is.

[0060] In one embodiment, the aldehyde scavenger may be selected from polyethyleneimine or other ethyleneamines; hydrazides; carbodiimides; aminotriazines such as melamine; guanamine-related compounds; triethanolamine; acrylamide copolymers; urea and organic derivatives.

[0061] Another class of aldehyde scavengers (referred to as Scavenger AS7) may be of the general formula: [ka] In the formula, R 60 and R 61 independently represent a hydrogen atom or an optionally substituted, preferably unsubstituted, alkyl, cycloalkyl or aromatic group; R 62 and R 63independently represent a hydrogen atom or an optionally substituted, preferably unsubstituted, alkyl, cycloalkyl or aromatic group.

[0062] In a preferred embodiment of the compound of formula XXV above, R 60 and R 61 each independently represents a hydrogen atom or an unsubstituted alkyl or cycloalkyl group; R 62 are independently a hydrogen atom or an unsubstituted alkyl or cycloalkyl group. In a particularly preferred embodiment, R 60 , R 61 , R 62 and R 63 Each represents a hydrogen atom.

[0063] Preferred aldehyde scavengers include at least one amide moiety. Preferably, the carbon atom of the at least one amide moiety is separated from the nitrogen atom by at least two other atoms, preferably carbon atoms. At least one of the two carbon atoms is preferably unsaturated. Such preferred aldehyde scavengers may include the following moiety: [ka] wherein multiple carbon atoms may be unsaturated, for example part of a phenyl ring, or preferred aldehyde scavengers include the moiety: [ka]

[0064] Particularly preferred aldehydes, such as formaldehyde, scavengers are selected from anthranilamide, compound XX and cyanoacetamide.

[0065] References herein to "ppm" refer to "parts per million" by weight.

[0066] The formulation may comprise at least 30% by weight, preferably at least 40% by weight, and more preferably at least 50% by weight of the liquid carrier. The formulation may comprise less than 90% by weight, preferably less than 80% by weight of the liquid carrier. The liquid formulation may comprise 50 to 90% by weight (e.g., 50 to 80% by weight) of the liquid carrier and 10 to 50% by weight (e.g., 20 to 50% by weight) of the aldehyde scavenger. The liquid carrier is preferably liquid at 25°C and atmospheric pressure. A suitable liquid carrier has good solubility in the POM to which it is added. It may comprise an oil (e.g., vegetable oil or mineral oil) or a glycol. Typical carriers include hydrocarbons, hydrocarbon mixtures, alcohols, esters, polyethers, and mixtures of two or more thereof. The POM-compatible organic liquid carrier may be an oil-based vehicle. Examples of such vehicles are the materials sold as Clearslip™ 2, Clearslip™ 3 and Process Aid-1 by ColorMatrix Europe Ltd, Units 9-11 Unity Grove, Knowsley Business Park, Merseyside, L34 9GT.

[0067] The formulation may contain 0 to 10% by weight of other additives. The formulation may contain 0 to 5% by weight, for example 0 to 3% by weight, of a dispersant.

[0068] It has been found that the inclusion of antioxidants can act synergistically in liquid formulations to improve aldehyde scavenging performance. The formulation may contain 0-10 wt% of one or more antioxidants. The total wt% of antioxidants in the formulation may be in the range of 0-10 wt%, preferably in the range of 0.5-10 wt%, or in the range of 0.5-7.0 wt%. The liquid formulation preferably contains at least 1.0 wt% antioxidant.

[0069] The formulation may optionally include a phosphorus-containing antioxidant (e.g., phosphite-based compounds such as triphenyl phosphite, triphenyl phosphate-based compounds such as tris(2,4-di-t-butylphenyl) phosphate, diphosphonite-based compounds, and metal salts of hypophosphorous acid).

[0070] The antioxidant may comprise a sterically hindered phenol compound having the moiety: [ka] wherein R 50 and R 51 R independently contains at least four atoms, preferably selected from C atoms, H atoms, O atoms and N atoms, more preferably selected from C atoms and H atoms. 50 and R 51 is preferably saturated. 50 may represent a tertiary alkyl moiety, for example, a tertiary alkyl moiety containing at least 4 carbon atoms. 50 preferably represents a t-butyl moiety. 51 is C 1~4 It may also represent an alkyl moiety, especially a methyl group.

[0071] The antioxidant may comprise at least two moieties XXX.

[0072] The antioxidant may contain one or more oxyalkylene moieties, such as oxyethylene moieties.

[0073] The antioxidant may include one or more ester moieties.

[0074] The antioxidant preferably contains only C, H and O atoms.

[0075] The antioxidant has the following formula: [ka] wherein L 50 is preferably a linking moiety comprising an oxyalkylene moiety and one or more ester moieties. The antioxidant may be: [ka]

[0076] The method preferably reduces the aldehyde content in the POM polymer, the POM polymer containing 2 ppm or less aldehydes when evaluated according to VDA-275.

[0077] According to a second aspect of the present invention there is provided a polyoxymethylene (POM) polymer having reduced aldehyde levels, the polyoxymethylene (POM) polymer incorporating an aldehyde scavenger according to the first aspect or the product of the reaction of an aldehyde scavenger according to the first aspect with an aldehyde.

[0078] The POM polymer preferably contains no more than 2 ppm aldehydes when evaluated according to VDA-275.

[0079] The POM polymer preferably comprises a carrier as described according to the remaining first aspect.

[0080] The POM polymer preferably comprises an antioxidant as described according to the first aspect.

[0081] The POM polymer may be in pellet form.

[0082] The liquid formulations described may be used in the manufacture of parts or in the manufacture of pellets, e.g. masterbatch pellets, which may be used in the manufacture of subsequent parts. Thus, according to a third aspect of the present invention, there is provided a method for producing an article, e.g. a moulded article, or pellets from a polyoxymethylene (POM) polymer, comprising: (a) selecting a liquid formulation comprising a liquid carrier and an aldehyde scavenger as described in the first and / or second aspects; (b) contacting a POM polymer with the liquid formulation; (c) forming the POM polymer into an article, such as a molded article, or into pellets; A method is provided that includes:

[0083] The article or pellets preferably contain no more than 2 ppm of aldehydes when evaluated according to VDA-275.

[0084] Preferably, in step (c), the POM polymer is suitably melt processed to define the article or pellet.

[0085] The articles or pellets may be defined by any process known in the art, including, for example, injection molding, blow molding, thermoforming, or extrusion.

[0086] The article or pellets may contain one or more colorants, for example, when an article is produced, it may contain 5 to 500 ppm of colorant. The ppm mentioned above is preferably based on the amount of POM polymer. The colorants described herein may be dyes or pigments. When pellets are produced, the pellets may contain up to 60% by weight of a colorant, for example, titanium dioxide. Such pellets may suitably define a masterbatch containing 5 to 35% by weight of a filler, for example, suitably a colorant as described.

[0087] Preferably, in the molded article, the sum of the weight percent of the one or more POM polymers and the aldehyde scavenger is at least 90 weight percent, at least 95 weight percent, or at least 98 weight percent.

[0088] According to a fourth aspect of the present invention there is provided an article or pellet having reduced aldehyde levels, produced as described in the fourth aspect and / or comprising a (POM) polymer and an aldehyde scavenger as described.

[0089] The article preferably contains no more than 2 ppm of aldehydes when evaluated according to VDA-275.

[0090] Any aspect of any invention described herein may be combined, mutatis mutandis, with any other aspect of any invention described herein. DETAILED DESCRIPTION OF THE INVENTION

[0091] Specific embodiments of the present invention will now be described by way of example.

[0092] The following materials are referenced hereinafter: Anthranilamide - commercially available from Sigma Aldrich 2-Cyanoacetamide - commercially available from Fisher Scientific Irganox 1010 - commercially available pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) obtained from Sigma Aldrich Carrier A - refers to Clearslip™ 2 available from ColorMatrix. Carrier A was selected to have good solubility for the POM copolymer used. Copolymer POM - refers to Ultraform S2320 POM copolymer obtained from BASF [Example]

[0093] Rating 1 - General procedure for determining the formaldehyde content of plaques The formaldehyde content of the samples is determined on injection-molded plaques (40 x 100 x 3 mm (W x L x D)). Formaldehyde levels are determined using a Markes Micro-Chamber / Thermal Extractor™ (µ-CTE™). This device is a versatile, compact unit with up to four small cylindrical chambers that allows sampling of chemicals emitted from products or materials. Emitted volatile and semivolatile organic compounds (VOCs and SVOCs) are collected in cartridges containing 2,4-dinitrophenylhydrazine for analysis by HPLC according to ISO 16000-3. Formaldehyde reduction is calculated based on the percentage reduction observed in formaldehyde levels of parts with the additive compared to a reference part without the additive. The evaluations described have been shown to be comparable to the automotive standard formaldehyde test, VDA-275.

[0094] Evaluation 2 - Procedures for measuring optical properties Plaques (size 95 x 165 x 3 mm (W x L x D)) prepared in a similar manner as described below and related controls were prepared and their optical properties (i.e., L * , a * and b * ) was evaluated using a Minolta CM-3700d spectrophotometer in transmission mode equipped with a D65 / 10° light source.

[0095] [Table 1]

[0096] Rating 3 - Oxidation Induction Time Test Oxidation induction time (OIT) tests were performed using heat flux differential scanning calorimetry (DSC) to analyze the thermal stability of POM samples. Approximately 5–6 mg of sample was heated from room temperature to 230°C under a nitrogen gas flow (50 ml / min) and held for 5 minutes. This gas flow was then switched to oxygen (50 ml / min) and held constant to determine the induction time. As discussed in V. Archodoulaki, S. Lueftl, and S. Seidler, “Oxidation induction time studies on the thermal degradation behavior of polyoxymethylene,” Polymer Testing, Vol. 25, No. 1, pp. 83–90, 2006, observations indicate that it is difficult to determine a clear onset temperature; therefore, the peak maximum of the OIT response, rather than the onset temperature, is interpreted as the OIT result.

[0097] Example 1 - Preparation of the acetaldehyde scavenger N,N'-(2-(4-(2-aminobenzamido)butyl)pentane-1,5-diyl)bis(2-aminobenzamide) (designated Compound X) Compound X has the following structure: [ka]

[0098] 2H-Benzo[d][1,3]oxazine-2,4(1H)-dione (98.84 g, 3.5 equivalents, 605.9 mmol) was dissolved in dimethylformamide (500 mL) at room temperature. A solution of 4-(aminomethyl)octane-1,8-diamine (30.00 g, 1 equivalent, 173.1 mmol) in dimethylformamide (250 mL) was added dropwise to the reaction mixture. The reaction mixture was stirred overnight at room temperature until complete conversion was confirmed by LC-MS. The dimethylformamide was removed under reduced pressure to give a dark brown oil. Water (1 L) and ammonium hydroxide (25%, 50 mL) were added, and the product was extracted with dichloromethane. The dichloromethane was removed under reduced pressure, and the product was recrystallized in a mixture of methanol and acetonitrile. The solid was collected by filtration and dried to give N,N'-(2-(4-(2-aminobenzamido)butyl)pentane-1,5-diyl)bis(2-aminobenzamide) (51.0 g, 55.5% yield), the structure of which was confirmed by NMR and LC-MS, and the melting point was 160°C.

[0099] Example 2 - Preparation of N,N'-(hexane-1,6-diyl)bis(2-aminobenzamide) (designated Compound Y) To a stirred mixture of 2H-benzo[d][1,3]oxazine-2,4(1H)-dione (175 g, 2.5 equiv., 1.08 mol) in DMSO (1000 ml) was slowly added a solution of hexane-1,6-diamine (50.0 g, 1 equiv., 430 mmol) in DMSO (150 ml). The reaction mixture was stirred overnight, followed by the addition of water. The resulting solid was collected by filtration and dissolved in hot EtOAc with the addition of 2N HCl. The solid was filtered off and dissolved in EtOH and 25% ammonium hydroxide solution. The mother liquor was washed with EtOAc. The organic extracts were collected and dried over anhydrous sodium sulfate. The solvent was removed to give a brown solid. The crude product was filtered and washed with EtOAc and DCM. The solid was collected and dried to give N,N'-(hexane-1,6-diyl)bis(2-aminobenzamide) (102.2 g, 67.0%).

[0100] Example 3 - General procedure for preparing solid formulations Solid masterbatch formulations were prepared by blending the required amounts of base polymer, formaldehyde reducing agent, and antioxidant stabilizer in a twin-screw extruder. Pellets were cut using a strand cutter. Materials were prepared using a Labtech LTE444-16 twin-screw extruder using the following conditions:

[0101] [Table 2]

[0102] Example 4 - General Procedure for Preparing Liquid Formulations The liquid formulation was prepared by combining Liquid Carrier A and a dispersant in a liquid mixing vessel. To this was added an aldehyde scavenger and an antioxidant. Optionally, the formulation may be milled to obtain the desired particle size. Optionally, a rheology modifier may be added. A dispersant is also optional. The formulation was mixed under vacuum to remove any remaining air.

[0103] As described in the Examples below, liquid and solid formulations containing aldehyde scavengers were prepared and compared when added to copolymer POM.

[0104] Example 5 - Preparation of a solid formulation of 2-cyanoacetamide Following the procedure outlined in Example 3, a solid formulation was prepared having the following composition:

[0105] [Table 3]

[0106] Example 6 - Preparation of a liquid blend of 2-cyanoacetamide, Compound X and anthranilamide Following the procedure described in Example 4, liquid formulations were prepared having the following compositions. Note that in each case the carrier was Carrier A and the antioxidant was Irganox 1010.

[0107] [Table 4]

[0108] Examples 8-11 - Evaluation of solid and liquid formulations The solid or liquid formulations (I-IV) described in Examples 5 and 6 were added to copolymer POM at the addition rates detailed in the table below to prepare plaques with dimensions of 40 mm x 100 mm x 20 mm. Formaldehyde emissions were evaluated as described in Evaluation 1, and the L * , a * (D65), b * (D65) was evaluated as described in Evaluation 2.

[0109] The results are shown in the table below.

[0110] [Table 5]

[0111] The control refers to the copolymer POM without any additives.

[0112] It should be noted from the results that Examples 8 and 11 contain the same aldehyde scavenger delivered to the polymer at the same concentration, but the liquid dispersion (Formulation IV) provides greater efficacy at lower loading levels, significantly reducing discoloration.

[0113] Example 12 - Preparation of solid and liquid formulations containing anthranilamide Following the procedures described in Examples 5 and 6, solid and liquid formulations containing anthranilamide were prepared having the compositions detailed in the tables below, where the aldehyde scavenger (AS) component was anthranilamide, the antioxidant was Irganox 1010, the liquid carrier for Formulation No. VI was Carrier A, and the solid carrier for Formulation No. V was copolymer POM.

[0114] [Table 6]

[0115] Examples 13-14 - Evaluation of solid and liquid formulations containing anthranilamide Solid Formulation V and Liquid Formulation VI were added to Ultraform S2320 POM copolymer and plaques were produced by injection molding at let-down ratios (LDR) as listed in the table below. Formaldehyde emissions were evaluated as described in Evaluation 1, and LDR was 0.01. * , a * (D65), b * (D65) was evaluated as described in Evaluation 2.

[0116] [Table 7]

[0117] The control refers to the copolymer POM without any additives.

[0118] Use of the solid masterbatch (Example 13) failed to achieve the 2 ppm target for automotive applications. The liquid formulation (Example 14) provided the required formaldehyde reduction, along with reduced discoloration, at significantly reduced dosage levels. No discernible differences in release profiles or oxidation induction times were observed between the formulation options.

[0119] Example 15 - Preparation of solid and liquid formulations containing Compound X Following the procedures described in Examples 5 and 6, solid and liquid formulations containing Compound X were prepared having the compositions detailed in the tables below.

[0120] Below, the aldehyde scavenger (AS) component was Compound X, the antioxidant was Irganox 1010, the liquid carrier for Formulation No. VIII was Carrier A, and the solid carrier for Formulation No. VII was Copolymer POM.

[0121] [Table 8]

[0122] Examples 16-17 - Evaluation of solid and liquid formulations containing Compound X Solid Formulation VII and Liquid Formulation VIII were added to Ultraform S2320 POM copolymer and plaques were produced by injection molding at let-down ratios (LDR) as listed in the table below. Formaldehyde emissions were evaluated as described in Evaluation 1, and LDR was 0.01. * , a * (D65), b * (D65) was evaluated as described in Evaluation 2.

[0123] [Table 9]

[0124] The control refers to the copolymer POM without any additives.

[0125] The use of a solid masterbatch failed to achieve the 2 ppm target for automotive applications (Example 16). The liquid formulation (Example 17) provided the required formaldehyde reduction, along with reduced discoloration, at significantly reduced dosage levels. No discernible differences in release profiles or oxidation induction times between formulation options were observed.

[0126] Example 18 - Preparation of solid and liquid formulations containing 2-cyanoacetamide Following the procedures described in Examples 5 and 6, solid and liquid formulations containing cyanoacetamide were prepared having the compositions detailed in the tables below, where the aldehyde scavenger (AS) component was 2-cyanoacetamide, the antioxidant was Irganox 1010, the liquid carrier for Formulation No. X was Carrier A, and the solid carrier for Formulation No. IX was copolymer POM.

[0127] [Table 10]

[0128] Examples 19 and 20 - Evaluation of solid and liquid formulations containing 2-cyanoacetamide Solid Formulation IX and Liquid Formulation X were added to Ultraform S2320 POM copolymer and plaques were produced by injection molding at let down ratios (LDR) as listed in the table below. Formaldehyde emissions were evaluated as described in Evaluation 1, and LDR was 0.01. * , a * (D65), b * (D65) was evaluated as described in Evaluation 2.

[0129] [Table 11]

[0130] The control refers to the copolymer POM without any additives.

[0131] The use of a solid masterbatch failed to achieve the 2 ppm target for automotive applications (Example 19). The liquid formulation (Example 20) provided the required formaldehyde reduction, along with reduced discoloration, at significantly reduced dosage levels. No discernible differences in release profiles or oxidation induction times between formulation options were observed.

[0132] Examples 21-24 - Use of Anthranilamide as an Aldehyde Scavenger and the Synergistic Impact of Formulation Components on Formaldehyde Emissions Following the procedures outlined for Examples 8-11, individual components or mixtures of components contained in the described liquid formulations were dosed at the indicated levels into copolymer POM and then evaluated to determine their individual and / or joint effects on formaldehyde emissions and optical properties. Details of the components and mixtures evaluated and the results are provided in the table below.

[0133] When a carrier and antioxidant were used, these components were Carrier A and Irganox 1010, respectively.

[0134] [Table 12]

[0135] The results show that the combination of aldehyde scavenger and liquid in Example 22 also results in very low formaldehyde emissions, and when the scavenger, liquid and antioxidant are combined (Example 23), formaldehyde emissions are even lower.

[0136] Examples 25-27 - Use of Compound X as an Aldehyde Scavenger and the Synergistic Impact of Formulation Components on Formaldehyde Emissions Following the procedures outlined for Examples 8-11, individual components or mixtures of components contained in the described liquid formulations were dosed at the indicated levels into copolymer POM and then evaluated to determine their individual and / or joint effects on formaldehyde emissions and optical properties. Details of the components and mixtures evaluated and the results are provided in the table below.

[0137] When a carrier and antioxidant were used, these components were Carrier A and Irganox 1010, respectively.

[0138] [Table 13]

[0139] The results show that in Example 25, the combination of an aldehyde scavenger and a liquid results in low formaldehyde emissions, and when the scavenger, liquid and antioxidant are combined (Example 27), formaldehyde emissions are even lower.

[0140] Examples 28-31 - Use of Compound Y as an Aldehyde Scavenger and the Synergistic Impact of Formulation Components on Formaldehyde Emissions Following the procedures outlined for Examples 8-11, individual components or mixtures of components contained in the described liquid formulations were dosed at the indicated levels into copolymer POM and then evaluated to determine their individual and / or joint effects on formaldehyde emissions and optical properties. Details of the components and mixtures evaluated and the results are provided in the table below.

[0141] When a carrier and antioxidant were used, these components were Carrier A and Irganox 1010, respectively.

[0142] [Table 14]

[0143] In the case of POM formulations, a wide range of materials may be incorporated into the formulation, including stabilizers such as hindered amine light stabilizers (HALS); acid scavengers, e.g., calcium stearate, hydrotalcite; lubricants, e.g., waxes; BaSO4, TiO2, carbon black, pigments, aromatic polyamides, silicon powder, polytetrafluoroethylene, and UV stabilizers.

[0144] The invention is not limited to the details of the above-described embodiments, and extends to any novel one or any novel combination of features disclosed in this specification (including the accompanying claims, abstract and drawings), or to any novel one or any novel combination of steps of any method or process so disclosed.

Claims

1. A method for reducing the aldehyde content in a polyoxymethylene (POM) polymer, comprising the step of contacting the POM polymer, or a monomer, oligomer, or prepolymer involved in the preparation of the POM polymer, with a liquid formulation, wherein the liquid formulation comprises a liquid carrier and an aldehyde scavenger.

2. The method according to claim 1, comprising the step of bringing a POM polymer into contact with the liquid formulation.

3. The method according to claim 1, wherein the POM is a homopolymer POM or a copolymer POM.

4. The method according to claim 1, wherein the liquid compound is a liquid in STP.

5. The aldehyde scavenger mentioned above is a scavenger of the following class: (i) A scavenger AS2 comprising at least two constituent molecular fragments, wherein each constituent molecular fragment comprises at least two hydrogen-substituted heteroatoms bonded to the carbon of the respective constituent molecular fragment, (ii) A scavenger AS5 comprising compound (A) containing the first fragment, the second fragment and the third fragment, The first fragment mentioned above includes the following portion: 【Chemistry 1】 In the formula, R' represents a substituent, and n1 is between 0 and 4. The second fragment mentioned above includes the following portion: 【Chemistry 2】 In the formula, R' represents a substituent, and n1 is between 0 and 4. The third fragment mentioned above includes the following portion: 【Transformation 3】 In the formula, R' represents a substituent, and n1 is 0 to 4 for the scavenger AS5. (iii) The following general formula of scavenging agent AS7, 【Chemistry 4】 In the formula, R ６０ and R ６１ Each independently represents a hydrogen atom or an alkyl, cycloalkyl, or aromatic group, which may be substituted, preferably unsubstituted. R ６２ and R ６３ AS7 is a scavenger representing a hydrogen atom or, optionally, an alkyl, cycloalkyl, or aromatic group, which may be substituted, preferably unsubstituted. The method according to claim 1, selected from among.

6. The aldehyde scavenger is as follows: Anthranilamide, 1,8-diaminonaphthalene, allantoin, 3,4-diaminobenzoic acid, malonamide, salicylanilide, 6-amino-1,3-dimethyluracil (DMU), 6-aminoisocytosine, 6-aminouracil, 6-amino-1-methyluracil, A scavenger AS5 comprising the following structure, 【Transformation 5】 In the formula, M represents the scavenger AS5, which contains a saturated hydrocarbon moiety that may incorporate a nitrogen atom. R ６０ and R ６１ However, independently, R represents a hydrogen atom or an unsubstituted alkyl group or cycloalkyl group. ６２ and R ６３ However, independently, the scavenger AS7 of formula XXV represents a hydrogen atom or an unsubstituted alkyl or cycloalkyl group. The method according to claim 5, selected from among.

7. The aldehyde scavenger is anthranilamide, cyanoacetamide, or 【Transformation 6】 The method according to claim 1, wherein compound XX is selected from the compound XX.

8. The aldehyde scavenger includes the following portion: 【Transformation 7】 In the formula, the carbon atom is part of the phenyl ring, or the aldehyde scavenger is part of the following 【Transformation 8】 The method according to claim 1, including the method described in claim 1.

9. The method according to claim 1, wherein the compound comprises at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight of a liquid carrier, and / or less than 90% by weight, preferably less than 80% by weight of a liquid carrier.

10. The method according to claim 1, wherein the liquid formulation comprises 50 to 90% by weight (for example, 50 to 80% by weight) of a liquid carrier and 10 to 50% by weight (for example, 20 to 50% by weight) of the aldehyde scavenger.

11. The method according to claim 1, wherein the liquid carrier is oil or glycol.

12. The method according to claim 1, wherein the compound comprises 0.5 to 10% by weight of an antioxidant.

13. The method according to claim 12, wherein the antioxidant comprises a highly sterically hindered phenol compound.

14. The aforementioned antioxidant is given by the following formula: 【Chemistry 9】 In the formula, L ５０ is a linking moiety containing an oxyalkylene moiety and one or more ester moieties The method according to claim 13.

15. The method according to claim 1, wherein the method reduces the aldehyde content in the POM polymer, and the POM polymer contains 2 ppm or less of aldehyde when evaluated according to VDA-275.

16. A polyoxymethylene (POM) polymer having a reduced aldehyde level, comprising an aldehyde scavenger according to any one of claims 1 to 15 or a product of a reaction between the aldehyde scavenger according to any one of claims 1 to 15 and an aldehyde.

17. The polymer according to claim 16, wherein the POM polymer contains 2 ppm or less of aldehyde when evaluated according to VDA-275.

18. The polymer according to claim 16, wherein the POM polymer comprises a carrier according to any one of claims 1 to 15 that remains.

19. The POM polymer is the polymer according to claim 16, comprising the antioxidant described in any one of claims 1 to 15.

20. The polymer according to claim 16, wherein the POM polymer is in pellet form.

21. A method for producing articles or pellets from polyoxymethylene (POM) polymer, (a) A step of selecting a liquid formulation comprising a liquid carrier and an aldehyde scavenger according to any one of claims 1 to 15, (b) A step of bringing the POM polymer into contact with the liquid formulation, (c) A step of molding the POM polymer into an article, for example, a molded article, or pellets. A method that includes this.

22. The method according to claim 21, wherein the article or pellet contains 2 ppm or less of aldehyde when evaluated according to VDA-275.

23. The method according to claim 21, wherein in step (c), the POM polymer is melt-processed to define the article or pellet.

24. The method according to claim 21, wherein the article or pellet contains one or more colorants, and if the article is manufactured, it contains 5 to 500 ppm of colorants, and if pellets are produced, the pellet contains up to 35% by weight of colorants.

25. The method according to claim 21, wherein in the molded article, the total weight percentage of one or more POM polymers and the aldehyde scavenger is at least 90% by weight, at least 95% by weight, or at least 98% by weight.

26. Articles or pellets having a reduced aldehyde level, manufactured as described in claim 21, comprising a POM polymer and an aldehyde scavenger as described in any one of claims 1 to 15.

27. The article or pellet according to claim 26, wherein the article, when evaluated in accordance with VDA-275, contains 2 ppm or less of aldehyde.

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