Polyformaldehyde polymers containing aldehyde scavengers

Abstract

The present invention provides a method of reducing the aldehyde content in a polyoxymethylene (POM) polymer comprising the step of contacting a 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.

Description

Technical Field

[0001] The present invention relates to polymeric materials, particularly but not limited to polyoxymethylene (POM), to which aldehydes may be undesirably bound, for example due to generation during manufacture of the polymeric material, during downstream melt processing of the polymeric material and / or during use. Background Art

[0002] Polyoxymethylene (POM) is also known as acetal, polyacetal or polyoxymethylene. It is a polymer with a linear ether structure (CH2O-)n along its backbone. This linearity results in a high crystallinity of up to 80% and a high crystallinity of 1.410-1.420 g / cm 3 In some cases, POM can be filled (for example with glass fibers or carbon fibers).

[0003] Polyoxymethylene is increasingly used in a wide range of applications, including electrical and electronics, consumer products, automotive and industrial machinery, medical devices, building and construction.

[0004] POM can be sold as a copolymer or homopolymer. POM homopolymer has the following structure

[0005]

[0006] It is mainly composed of the above-mentioned repeating units.

[0007] POM copolymers include the following repeating units:

[0008]

[0009] It is mainly composed of the above-mentioned repeating units.

[0010] Both POM homopolymers and POM copolymers use methanol as the main base raw material. For POM homopolymers, formaldehyde is synthesized by air oxidation of methanol, followed by the use of ionic initiators to form acetal resins. The resins in POM homopolymers are stabilized by substitution of ester groups for the hydroxyl groups at the ends of the polymer chains. POM copolymers are usually produced using trioxane as a raw material (also starting with methanol). About 2-3% of an epoxy compound is copolymerized with trioxane to give a stable POM copolymer. Chain end-capping agents may also be used. POM copolymer resins have a higher stability, but a reduced crystallinity due to the carbon-carbon bonded groups interspersed in their polymer chains. This polymer structure also has excellent resistance to alkalis, hot water, and other chemicals, as well as a long life at high temperatures and greater freedom in processing conditions. On the other hand, its tensile strength, stiffness, softening point, and melting point are lower than those of acetal homopolymers.

[0011] Polyoxymethylene (POM) is inherently unstable and susceptible 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 results in polymer degradation, which generates formaldehyde. Formaldehyde release leads to workplace safety challenges during polymer processing and limits the use of polymers in applications where air quality is critical, such as automotive applications.

[0012] Formaldehyde produced by polymer degradation can be oxidized to formic acid, which contributes to the hydrolysis of the polymer chains. In addition to formaldehyde release, POM degradation can also lead to mold deposition, reduced mechanical properties and discoloration.

[0013] POM resins can also be sensitive to acid hydrolysis by inorganic acids. For example, low levels of chlorine in drinking water can lead to environmental stress cracking. Therefore, POM parts are stabilized to mitigate this degradation.

[0014] It is known that measures can be taken to stabilize POM and reduce aldehyde release. For example, steps to achieve stabilization can be applied at the final stage of POM production or during melt processing to form an article or masterbatch. Methods that have been developed to prevent POM degradation include phenolic antioxidants to limit oxidative degradation, lubricants to reduce shear forces, acid scavengers to prevent formic acid hydrolysis, scavengers to react with free formaldehyde, the use of end-capping agents, light stabilizers and / or comonomers to improve stability.

[0015] Despite the commercial use of various stabilization assemblies, achieving material emission targets for automotive applications, such as the VDA-275 target of 2 ppm, and the global emission targets of VDA-277 or VDA-278, remains challenging. Most treatments disclosed in the prior art that aim to control formaldehyde do not meet the VDA-275 target or require uneconomical additions for this purpose, result in discoloration and / or adversely affect the properties of the POM. Summary of the invention

[0016] The object of the present invention is to solve the problems associated with aldehydes in POM.

[0017] It is an object of the present invention to solve one or more of the above problems.

[0018] 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 preparation, wherein the liquid preparation comprises a liquid carrier and an aldehyde scavenger.

[0019] The appropriate reduction of aldehydes mentioned in this article refers primarily to formaldehyde, which, as mentioned earlier, is a particular problem in the context of POM.

[0020] Preferably, the method comprises the step of contacting a POM polymer with the liquid formulation.

[0021] Unexpectedly, the liquid formulations have been found to outperform comparable solid formulations, allowing lower amounts of aldehyde scavenger to be delivered to the POM and / or more easily reducing aldehyde release to levels that meet relevant material release targets (eg, VDA-275).

[0022] The material state (e.g. liquid) referred to herein refers to the state at standard temperature and pressure (STP). Thus, suitably, the liquid formulation is a liquid at STP; and suitably, the liquid carrier is a liquid at STP.

[0023] The POM suitably comprises a -(CH2O)- repeating unit (referred to as "repeating unit X"). It may also comprise a -(CH2CH2O)- repeating unit (referred to as "repeating unit Y"). Preferably, in the POM, the sum of the mol % of repeating units X and Y is at least 80 mol %, preferably at least 90 mol %, more preferably at least 95 mol %, especially about 100 mol %.

[0024] In the POM, the weight percentage of the POM polymer composed of repeating units X and Y is at least 80 weight %, preferably at least 90 weight %, more preferably at least 95 weight %, and in particular at least 98 weight %.

[0025] The POM is a POM homopolymer, which suitably consists essentially of repeating units X, or may be a POM copolymer, which suitably consists essentially of repeating units X and Y.

[0026] In the method, the aldehyde scavenger may be any chemical that reduces aldehydes, for example by reacting with the aldehyde. Thus, the amount of aldehyde bound to the POM in the presence of the aldehyde scavenger is suitably less than in the absence of the scavenger.

[0027] In one embodiment, preferred aldehyde scavengers include amine moieties and amide moieties. In one embodiment, preferred aldehyde scavengers include substituted phenyl moieties. In a preferred embodiment, the aldehyde scavenger may include amine moieties (particularly -NH2), amide moieties (particularly -CONH2) and substituted phenyl moieties. In this case, preferably 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.

[0028] One class of aldehyde scavengers (referred to as scavenger AS1) may include polyamides selected from 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 isophthalamide)-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. The most preferred low molecular weight aliphatic polyamide is polyhexamethylene adipamide having a number average molecular weight of 3000 to 6000 and an intrinsic viscosity of 0.4 to 0.9 dL / g.

[0029] Another type of aldehyde scavenger (referred to as scavenger AS2) can include at least two component molecular fragments, each component molecular fragment containing at least two hydrogen-substituted heteroatoms, which are bonded to the carbon of the corresponding component molecular fragment. The component molecular fragments of the organic additive compound each react with the aldehyde in the polyester to form water and the resulting organic molecular fragment, which contains an unbranched five-membered or six-membered ring with at least two heteroatoms. Preferably, the molecular weight of the organic additive compound is at least twice the molecular weight of the individual component molecular fragments. The heteroatoms present in each molecular fragment capable of reacting with the aldehyde include oxygen (O), nitrogen (N) and sulfur (S). Suitably, the heteroatoms of the component molecular fragments have at least one bond connected to active hydrogen (H), and water should be separated during the condensation process with the aldehyde. Preferred functional groups containing these heteroatoms include amines (NH2 and NHR), hydroxyl groups (OH), carboxyl groups (CO2H), amides (CONH2 and CONHR), sulfonamides (SO2NH2) and thiols (SH). These functional groups must be spatially arranged so that an unbranched five- or six-membered ring can be formed upon condensation with the aldehyde. Preferably, the structural arrangement allows for the formation of a six-membered ring. It is particularly preferred that the heteroatom of the organic additive is attached to a preformed ring. Most preferably, the preformed ring is an aromatic ring, so that the unbranched five- or six-membered ring of the resulting organic compound is bonded to the aromatic ring. Suitable organic additive compounds are substantially thermally stable at the temperatures required to melt process the polyester. It is also preferred that the functional groups present on the organic additive are relatively unreactive to the ester bonds present in the polyester. Examples of preferred scavengers include 1,2-bis(2-aminobenzamido)ethane; 1,2-bis(2-aminobenzamido)propane; 1,3-bis(2-aminobenzamido)propane; 1,3-bis(2-aminobenzamido)pentane; 1,5-bis(2-aminobenzamido)hexane; 1,6-bis(2-aminobenzamido)hexane; and 1,2-bis(2-aminobenzamido)cyclohexane. More preferred are scavengers in which the component molecular fragments are derived from o-aminobenzamide.

[0030] Another class of aldehyde scavengers suitable for the present invention (referred to as scavenger AS3) includes o-aminobenzamide, 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, triglycerides, trimethylolpropane, dipentaerythritol, tripentaerythritol, D-mannitol, D-sorbitol and xylitol. From the above group, o-aminobenzamide, 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.

[0031] 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.

[0032] The hydroxy compounds preferably contain 3 to about 8 hydroxyl groups. They may contain one or more substituents, such as ether groups, carboxylic acid groups, carboxylic acid amide groups or carboxylic acid ester groups.

[0033] Preferred hydroxy compounds include those compounds having a pair of hydroxy groups attached to corresponding carbon atoms, wherein the carbon atoms are separated from each other by at least one atom. Particularly preferred hydroxy compounds are those compounds wherein a pair of hydroxy groups attached to corresponding carbon atoms are separated from each other by a single carbon atom.

[0034] As examples of suitable hydroxy compounds, mention may be made of diols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,2-hexanediol, 2-methyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 1,2-cyclohexanediol, 1,1-cyclohexanedimethanol, diethylene glycol, triethylene glycol and polyethylene glycols (e.g., having a molecular weight of about 800 to about 2000) (e.g., Carbowax™ 1000, with a molecular weight of about 950 to about 1050, and each molecule containing about 20 to about 24 ethyleneoxy groups); triols, such as glycerol, trimethylolpropane, 2,3-di-(2'-hydroxyethyl)-1-cyclohexanol, 1,2,6-hexanetriol, 1,1,1-tris-(hydroxymethyl)-ethane, 3-(2'-hydroxyethoxy)-1,2-propylene glycol, 3-(2'-hydroxypropoxy)-1,2-propylene glycol, 2-(2'-hydroxyethoxy)-1,2-hexanediol, 6-(2'-hydroxypropoxy)-1 , 2-hexanediol, 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 following general formula:

[0035]

[0036] Where n is an integer,

[0037] Or trimethylolpropane propoxylate of the following general formula:

[0038]

[0039] Wherein 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-arabitol or L-arabitol, xylitol, iditol, talitol, allitol, altritol, guilitol, erythritol, threitol and D-gulonic-γ-lactone; and the like. A mixture of two or more such compounds may be used. Particularly preferred are aliphatic hydroxy compounds containing 3 to about 8 hydroxyl groups.

[0040] Another class of aldehyde scavengers (referred to as scavenger AS5) includes compound (A) comprising:

[0041] (I) The first fragment comprises part (A):

[0042]

[0043] and part (B):

[0044] NH(B)

[0045] wherein the carbon atoms of part (A) and the nitrogen atoms of part (B) are separated by at least one and not more than two atoms;

[0046] (II) the second fragment comprises part (A):

[0047]

[0048] and part (B):

[0049] NH(B)

[0050] wherein the carbon atoms of part (A) and the nitrogen atoms of part (B) are separated by at least one and not more than two atoms; and

[0051] (III) the third fragment comprises part (A):

[0052]

[0053] and part (B):

[0054] NH(B).

[0055] The first fragment may include part (C):

[0056]

[0057] wherein R' represents a substituent, and n1 is 0 to 4, such as 0 to 1, and preferably, n1 is 0. R' may be an optionally substituted alkyl group, such as an optionally substituted C 1-20 Alkyl, such as optionally substituted C 1-10 Alkyl. R' may be arranged to improve the compatibility of compound (A) in the polymer material with which it is in contact during the process, for example by R' comprising a relevant functional group to improve the compatibility. Alternatively and / or additionally, R' may be arranged to increase the mass of compound (A).

[0058] The moiety (B) in the first fragment is preferably NH2, and / or the NH moiety bonded to the benzene moiety is preferably NH2.

[0059] Suitably, moiety (C) is capable of reacting with an aldehyde in a condensation reaction to produce moiety (D).

[0060]

[0061] Wherein the bond with * represents the connection of the part (D) to another part of the compound (A), having The bond represents a portion of the aldehyde that reacts with part (C). When the content of aldehyde is reduced in the method, compound (D) can be the following formula:

[0062]

[0063] Thus, through this reaction, the aldehyde is eliminated and its residue is covalently bonded to the compound (A).

[0064] The second fragment may include part (C):

[0065]

[0066] wherein R' represents a substituent, and n1 is 0 to 4, such as 0 to 1, and preferably, n1 is 0. R' may be an optionally substituted alkyl group, such as an optionally substituted C 1-20 Alkyl, such as optionally substituted C 1-10 Alkyl. R' may be arranged to improve the compatibility of compound (A) in the polymer material with which it is in contact during the process, for example by R' comprising a relevant functional group to improve the compatibility. Alternatively and / or additionally, R' may be arranged to increase the mass of compound (A).

[0067] The moiety (B) in the second fragment is preferably NH2, and / or the NH moiety combined with the benzene moiety is preferably NH2.

[0068] The third segment may include the following parts:

[0069]

[0070] wherein R' represents a substituent, and n1 is 0 to 4, such as 0 to 1, and preferably, n1 is 0. R' may be an optionally substituted alkyl group, such as an optionally substituted C 1-20 Alkyl, such as optionally substituted C 1-10 R' may be arranged to improve the compatibility of compound (A) in the polymeric material with which it is in contact during the process, for example by including relevant functional groups in R'. Alternatively and / or additionally, R' may be arranged to increase the mass of compound (A). The portion (B) in the third fragment is preferably NH2, and / or the NH portion combined with the benzene portion is preferably NH2.

[0071] Preferably, the first fragment, the second fragment and the third fragment are appropriately bonded to the main fragment in compound (A) through the nitrogen atom of the CONH part of the corresponding part (A) of the first fragment, the second fragment and the third fragment. In a preferred embodiment, the compound (A) is essentially composed of the first fragment, the second fragment, the third fragment and the main fragment.

[0072] The main fragment may comprise only carbon, hydrogen and optionally nitrogen atoms.

[0073] Preferably, the main fragment comprises essentially no primary amine moieties (-NH2) other than those optionally separated from the carbonyl moiety (C=O) by at least one and not more than two atoms.

[0074] Optionally, the main fragment may include one or more secondary or tertiary amine moieties. In addition to any aromatic carbon atoms and carbonyl moieties, the main fragment preferably does not include any unsaturated carbon atoms. The main fragment preferably does not include any alkenyl or alkynyl groups.

[0075] The preferred scavenger AS5 comprises the following detailed structure:

[0076]

[0077] Wherein M represents the main fragment, and it comprises the atom selected from carbon, hydrogen, oxygen and nitrogen atom.More preferably, M represents the main fragment, and it comprises the atom selected from carbon, hydrogen and nitrogen atom.It can comprise saturated hydrocarbon part, and this saturated hydrocarbon part can be combined with nitrogen atom, for example secondary amine part.

[0078] Another class of aldehyde scavengers (referred to as scavenger AS6) includes compounds XX, which include at least three moieties (AA) of the formula

[0079]

[0080] wherein each moiety (AA) comprises an amine moiety (-NH2) bonded ortho or meta to an amide moiety (-CONH);

[0081] Each R 1 independently represent a substituent, m is an integer from 0 to 4; and

[0082] wherein the three moieties (AA) are bonded via their respective amide nitrogen atoms to respective carbon atoms of the main fragment, wherein the main fragment comprises only carbon and hydrogen atoms and is saturated.

[0083] One R 1 or each R 1Can be selected from halogen atoms, or optionally substituted hydrocarbyl, alkoxyl, amido, amide groups, phenolic or carboxyl groups. The optionally substituted hydrocarbyl can be substituted by one or more halogen atoms or alkoxyl, amido, amide groups, phenolic or carboxyl groups. The optionally substituted hydrocarbon is preferably unsubstituted.

[0084] One R 1 or multiple R 1 It may be optionally substituted, preferably unsubstituted alkyl, for example optionally substituted, more preferably unsubstituted C 1-20 (For example, C 1-10 ) alkyl. 1 can be arranged to improve the compatibility of compound XX in the polymeric material into which it can be incorporated, for example by R 1 Relevant functional groups are included to improve compatibility.

[0085] One or each m is 0 or 1. Preferably, each m = 0. That is, except for the amine moiety and the amide moiety, each moiety (A) is unsubstituted.

[0086] Preferably, in compound XX, at least one moiety (AA) comprises an amine moiety (-NH2) ortho-bonded to an amide moiety (-CONH). Preferably, in each moiety (AA) in compound (XX), the amine moiety is ortho-bonded to the amide moiety. Preferably, in this case, m=0.

[0087] Preferably, the main segment does not include any cyclic or aromatic moieties.Preferably, the main segment includes a linear or branched chain.

[0088] The main fragment may comprise 3 to 20 carbon atoms. Preferably, it comprises 5 to 15 carbon atoms, more preferably 7 to 12 carbon atoms, and in particular 8 to 10 carbon atoms. When the number of carbon atoms is n, the number of hydrogen atoms may be equal to 2n-1. Preferably, the main fragment comprises 5 to 39 hydrogen atoms. Preferably, it comprises 9 to 29 hydrogen atoms, more preferably 13 to 23 hydrogen atoms and in particular 15 to 19 hydrogen atoms.

[0089] In a preferred embodiment, the major fragment is C9H 17 part.

[0090] The main fragment may comprise a linear chain comprising 6 to 14 carbon atoms, preferably 6 to 10 carbon atoms. The linear chain may comprise branching points to which chains comprising 1 to 4 carbon atoms are attached.

[0091] The main fragment may have the following general formula (BB)

[0092]

[0093] wherein p, q and r are integers, suitably in the range of 1 to 10, preferably in the range of 1 to 5. Preferably, p is in the range of 2 to 4, q is in the range of 1 to 3 and r is in the range of 2 to 6.

[0094] 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.

[0095] In compound XX, the nitrogen atoms of the amide moiety (-CONH) are preferably spaced at least 2 carbon atoms apart, preferably at least 4 carbon atoms apart; and suitably not more than 10 carbon atoms apart, for example not more than 7 carbon atoms apart.

[0096] The compound XX may have the formula

[0097]

[0098] where p, q and r are as described above.

[0099] The compound XX is preferably

[0100]

[0101] 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.

[0102] Another class of aldehyde scavengers (referred to as scavenger AS7) may have the general formula XXV

[0103]

[0104] Where R 60 and R 61 independently represent a hydrogen atom or an optionally substituted, preferably unsubstituted alkyl, cycloalkyl or aromatic group; and

[0105] Where R 62 and R 63 independently represents a hydrogen atom or an optionally substituted, preferably unsubstituted alkyl, cycloalkyl or aromatic group.

[0106] In a preferred embodiment of the compound of formula XXV, R 60 and R 61 independently represent a hydrogen atom or an unsubstituted alkyl or cycloalkyl group, and R 62 R independently represents a hydrogen atom or an unsubstituted alkyl or cycloalkyl group. In a particularly preferred embodiment, R 60 , R61 , R 62 and R 63 Each represents a hydrogen atom.

[0107] 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 moieties:

[0108]

[0109] The carbon atom may be unsaturated, for example, part of a benzene ring; or the preferred aldehyde scavenger comprises the following moiety:

[0110]

[0111] Particularly preferred aldehyde scavengers (eg formaldehyde scavengers) are selected from anthranilamide, compound XX and cyanoacetamide.

[0112] The term "ppm" used herein refers to "parts per million" by weight.

[0113] The formulation may include at least 30 wt%, preferably at least 40 wt%, more preferably at least 50 wt% of a liquid carrier. It may include less than 90 wt%, preferably less than 80 wt% of a liquid carrier. The liquid formulation may contain 50 wt% to 90 wt% (e.g., 50 wt% to 80 wt%) of a liquid carrier and 10 wt% to 50 wt% (e.g., 20 wt% to 50 wt%) of the aldehyde scavenger. The liquid carrier is preferably a liquid at 25°C and atmospheric pressure. The liquid carrier should ensure that it has good solubility in the POM to be added. It may include oil (e.g., vegetable oil or mineral oil) or ethylene glycol. Typical carriers include hydrocarbons, hydrocarbon mixtures, alcohols, esters, polyethers, and mixtures of two or more thereof. An organic liquid carrier compatible with POM may be an oil-based carrier. An example of such a carrier is ColorMatrix Europe Ltd. (Address: Unity Grove 9-11, Knowsley Business Park, Merseyside, L349GT) under the trade name Clearslip TM 2. Clearslip TM 3 and materials sold by Process Aid-1.

[0114] The formulation may include 0 to 10 wt% of other additives. It may include 0 to 5 wt%, for example 0 to 3 wt% of a dispersant.

[0115] Studies have shown that adding an antioxidant to a liquid formulation can act synergistically to improve aldehyde scavenging performance. The formulation can include 0 to 10 wt% of one or more antioxidants. The sum of the weight percentages of the antioxidants in the formulation can be in the range of 0 to 10 wt%, preferably in the range of 0.5 w% to 10 wt% or 0.5 wt% to 7.0 wt%. The liquid formulation preferably includes at least 1.0 wt% of an antioxidant.

[0116] The formulation may optionally include a phosphorus-containing antioxidant (eg, phosphite series compounds such as triphenyl phosphite, triphenyl phosphate series compounds such as tris(2,4-di-tert-butylphenyl)phosphate, diphosphonate series compounds, and metal salts of hypophosphorous acid).

[0117] The antioxidant may include a sterically hindered phenolic compound. The antioxidant may include the following moieties:

[0118]

[0119] Where R 50 and R 51 R independently comprises at least four atoms, preferably selected from C, H, O and N atoms; more preferably selected from C and H atoms. 50 and R 51 Preferably it is saturated. 50 R may represent a tertiary alkyl moiety, for example a tertiary alkyl moiety comprising at least 4 carbon atoms. 50 Preferably represents a tert-butyl moiety. 51 Can represent C 1-4 Alkyl moieties, especially methyl.

[0120] The antioxidant may comprise at least two moieties XXX.

[0121] The antioxidant may include one or more oxyalkylene moieties, such as oxyethylene moieties.

[0122] The antioxidant may include one or more ester moieties.

[0123] The antioxidant preferably comprises only C, H and O atoms.

[0124] The antioxidant may have the following chemical formula

[0125]

[0126] Where L 50 is a linking moiety which suitably comprises the oxyalkylene moiety and one or more ester moieties. The antioxidant may be as follows:

[0127]

[0128] The method preferably reduces the aldehyde content in the POM polymer so that the POM polymer contains less than 2 ppm of aldehydes when evaluated according to VDA-275.

[0129] According to a second aspect of the present invention, there is provided a polyoxymethylene (POM) polymer having a reduced aldehyde content, the POM polymer incorporating an aldehyde scavenger according to the first aspect or a reaction product between the aldehyde scavenger according to the first aspect and an aldehyde.

[0130] The POM polymer preferably contains less than 2 ppm of aldehydes when evaluated according to VDA-275.

[0131] The POM polymer preferably comprises the residual carrier according to the first aspect.

[0132] The POM polymer preferably includes the antioxidant according to the first aspect.

[0133] The POM polymer may be in the form of particles.

[0134] The liquid formulation can be used to make parts or to make particles (e.g., masterbatch particles), which can be used for subsequent part manufacturing. Therefore, according to a third aspect of the present invention, there is provided a method for making an article (e.g., a shaped article) or particles from a polyoxymethylene (POM) polymer, the method comprising:

[0135] (a) selecting a liquid preparation, wherein the liquid preparation comprises the liquid carrier as described in the first aspect and / or the second aspect and an aldehyde scavenger;

[0136] (b) contacting a POM polymer with the liquid formulation; and

[0137] (c) forming the POM polymer into an article or particles, such as a shaped article.

[0138] The article or granules preferably contain less than 2 ppm of aldehydes when evaluated according to VDA-275.

[0139] Preferably, in step (c) the POM polymer is suitably melt processed to define said article or particles.

[0140] The article or particle may be defined by any method known in the art. For example, the method may include injection molding, blow molding, thermoforming or extrusion.

[0141] The article or particle may include one or more colorants, and for example, when manufacturing an article, 5-500 ppm of a colorant may be included. Suitably, the above ppm is based on the amount of the POM polymer. The colorant described herein may be a dye or a pigment. When manufacturing particles, the particles may include up to 60 wt% of a colorant, such as titanium dioxide. Suitably, as previously described, such particles may define a masterbatch, which suitably includes 5 wt% to 35 wt% of a filler (e.g., a colorant).

[0142] Preferably, in the shaped article, the sum of the weight percentages of the one or more POM polymers and the aldehyde scavenger is at least 90 wt%, at least 95 wt% or at least 98 wt%.

[0143] According to a fourth aspect of the present invention, there is provided an article or particle having a reduced aldehyde content, the article or particle being made as described in the fourth aspect and / or comprising a POM polymer and an aldehyde scavenger as described herein.

[0144] The article or granules preferably contain less than 2 ppm of aldehydes when evaluated according to VDA-275.

[0145] Any aspect of any invention described herein may be combined with any other aspect of any invention described herein mutatis mutandis. DETAILED DESCRIPTION

[0146] Specific embodiments of the present invention will now be described by way of example.

[0147] The following materials are described below:

[0148] o-Aminobenzamide - commercially available product purchased from Sigma-Aldrich;

[0149] 2-Cyanoacetamide - commercially available from Fisher Scientific;

[0150] Irganox 1010 - commercially available pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) purchased from Sigma-Aldrich;

[0151] Vector A - refers to Clearslip available from ColorMatrix TM 2. Carrier A is selected to have good solubility in the POM copolymer used.

[0152] POM copolymer - refers to Ultraform S2320 POM copolymer obtained from BASF; Assessment 1 - Assay Plate General steps for formaldehyde content

[0153] The formaldehyde content of the samples was determined on injection molded plaques (40 x 100 x 3 mm (W x L x H)). TM (μ-CTE TM ) determines the formaldehyde content. The device is a versatile and compact unit with up to four small cylindrical chambers that allows sampling of chemicals released from products or materials. The released volatile and semi-volatile organic compounds (VOC and SVOC) are collected in a column containing 2,4-dinitrophenylhydrazine for analysis by HPLC according to ISO 16000-3. The formaldehyde reduction is calculated based on the percentage reduction in the formaldehyde content of the part containing the additive compared to a reference part without additive. The described evaluation has been shown to be comparable to VDA-275, a standard formaldehyde test for automobiles.

[0154] Evaluation 2 - Optical Performance Measurement Procedure

[0155] Plaques (dimensions 95 x 165 x 3 mm (W x L x H)) and related controls were prepared in a manner similar to that described below and the optical properties (i.e., L*, a*, and b*) were evaluated in transmission mode using a Minolta CM-3700d spectrophotometer equipped with a D65 / 10° illuminant.

[0156]

[0157]

[0158] Evaluation 3 - Oxidation Induction Time Test

[0159] Oxidation induction time (OIT) tests were performed using heat flux differential scanning calorimetry (DSC) to analyze the thermal stability of POM samples. About 5-6 mg of sample was heated from room temperature to 230°C under nitrogen flow (50 ml / min) and held for 5 minutes. The gas flow was switched to oxygen (50 ml / min) and kept constant to study the induction time. As discussed in "Oxidation induction time studies on the thermal degradation behavior ofpolyoxymethylene" by V. Archodoulaki, S. Lüftl and S. Seidler, Polymer Testing, Vol. 25, No. 1, 2006, pp. 83-90, the maximum peak of the OIT response was used as the OIT result instead of the onset temperature because it was observed that it was difficult to determine a clear onset temperature.

[0160] Example 1 - Acetaldehyde scavenger N,N'-(2-(4-(2-aminobenzamido)butyl)pentane-1,5-diyl)

[0161] Preparation of bis(2-aminobenzamide) (referred to as compound X)

[0162] Compound X has the following structure.

[0163]

[0164] 2H-Benzo[d][1,3]oxazine-2,4(1H)-dione (98.84 g, 3.5 Eq, 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 Eq, 173.1 mmol) in dimethylformamide (250 ml) was added dropwise to the reaction mixture. The reaction mixture was stirred overnight at room temperature until LC-MS confirmed complete conversion. The dimethylformamide was removed under reduced pressure to give a dark brown oil. Water (1 liter), ammonium hydroxide (25%, 50 ml) were added thereto, 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, yield 55.5%). The structure of the compound was confirmed by NMR and LC-MS, and the melting point was 160°C.

[0165] Example 2 - Preparation of N,N'-(hexane-1,6-diyl)bis(2-aminobenzamide) (referred to as Compound Y)

[0166] To a stirred mixture of 2H-benzo[d][1,3]oxazine-2,4(1H)-dione (175g, 2.5Eq, 1.08mol) in DMSO (1000ml) was slowly added a solution of hexane-1,6-diamine (50.0g, 1Eq, 430mmol) in DMSO (150ml). The reaction mixture was stirred overnight and then water was added. The resulting solid was collected by filtration and dissolved in hot EtOAc and 2N HCl was added. The solid was removed by filtration and dissolved in EtOAc and 25% ammonium hydroxide solution. The mother liquor was washed with EtOAc. The organic extract was collected and dried over anhydrous sodium sulfate. The solvent was removed to obtain a brown solid. The crude product was filtered and washed with EtOAc and DCM. The solid was collected and dried to obtain N,N'-(hexane-1,6-diyl)bis(2-aminobenzamide) (102.2g, 67.0%).

[0167] Example 3 - General steps for preparing solid dosage forms

[0168] Solid masterbatch formulations were prepared by mixing the required amounts of base polymer, formaldehyde reducing agent and antioxidant stabilizer in a twin screw extruder. The pellets were cut using a strand cutter. The material was prepared using a Labtech LTE444-16 twin screw extruder under the following conditions:

[0169]

[0170]

[0171] Example 4 - General steps for preparing liquid formulations

[0172] The liquid formulation is prepared by mixing the liquid carrier A and the dispersant in a liquid mixing vessel. To this is added an aldehyde scavenger and an antioxidant. Optionally, the formulation may be ground to produce the desired particle size. A rheology modifier may optionally be added. The dispersant is also optional. The formulation is mixed under vacuum to remove any residual air.

[0173] Liquid and solid formulations containing aldehyde scavengers were prepared and compared when added to copolymer POM as described in the following examples.

[0174] Example 5-2-Preparation of solid preparation of cyanoacetamide

[0175] Following the steps generally described in Example 3, a solid formulation having the following composition was prepared:

[0176]

[0177] Example 6-2-Preparation of a Liquid Formulation of Cyanoacetamide, Compound X and Anthranilide

[0178] Liquid formulations having the following compositions were prepared following the procedure described in Example 4. Note that the carrier was Carrier A and the antioxidant was Irganox 1010 in each case.

[0179]

[0180]

[0181] Examples 8 to 11 - Evaluation of solid and liquid formulations

[0182] The solid formulations or liquid formulations (I to IV) described in Examples 5 and 6 were added to the POM copolymer at the dosage rates detailed in the table below and formed into plaques with dimensions of 40 mm x 100 mm x 20 mm. Formaldehyde emission was evaluated as described in Evaluation 1, and L*, a*(D65), b*(D65) were evaluated as described in Evaluation 2.

[0183] The results are shown in the following table:

[0184]

[0185] The control refers to the POM copolymer without additives.

[0186] It should be noted from the results that Examples 8 and 11 include the same aldehyde scavenger delivered to the polymer at the same concentration. The liquid dispersion (Formulation IV) was found to provide better efficacy at lower addition levels and significantly reduced discoloration.

[0187] Example 12 - Preparation of solid and liquid formulations containing o-aminobenzamide.

[0188] Solid and liquid formulations containing o-aminobenzamide were prepared according to the procedures described in Examples 5 and 6, and their compositions are shown in the following table. In the following, the aldehyde scavenger (AS) component is o-aminobenzamide, the antioxidant is Irganox 1010, the liquid carrier of Formulation VI is Carrier A, and the solid carrier of Formulation V is POM copolymer.

[0189]

[0190] Examples 13 to 14 - Evaluation of solid and liquid formulations containing o-aminobenzamide

[0191] Solid and liquid formulations V and VI were added to Ultraform S2320-POM copolymers and plaques produced by injection molding with the let-down-ratios (LDR) shown in the table below. Formaldehyde emission was evaluated as described in Evaluation 1, and L*, a*(D65), b*(D65) were evaluated as described in Evaluation 2.

[0192]

[0193] The control refers to the POM copolymer without additives.

[0194] The use of a solid masterbatch (Example 13) failed to achieve the target value of 2 ppm for automotive applications. The liquid formulation (Example 14) provided the desired formaldehyde reduction while significantly reducing the addition level and reducing discoloration. Note that there were no significant differences in the release profiles or oxidation induction times between the formulation choices.

[0195] Example 15 - Preparation of solid and liquid formulations containing compound X

[0196] According to the procedures described in Examples 5 and 6, solid preparations and liquid preparations containing Compound X were prepared, and their compositions are shown in the following table.

[0197] Hereinafter, the aldehyde scavenger (AS) component is Compound X, the antioxidant is Irganox 1010, the liquid carrier of Formulation VIII is Carrier A, and the solid carrier of Formulation VII is POM copolymer.

[0198]

[0199] Examples 16 to 17 - Evaluation of solid and liquid formulations containing Compound X

[0200] Solid and liquid formulations VII and VIII were added to Ultraform S2320-POM copolymers and plaques produced by injection molding with the following LDRs. Formaldehyde emission was evaluated as described in Evaluation 1, and L*, a*(D65), b*(D65) were evaluated as described in Evaluation 2.

[0201]

[0202] The control refers to the POM copolymer without additives.

[0203] The use of a solid masterbatch failed to achieve the target of 2 ppm in automotive applications (Example 16). The liquid formulation (Example 17) provided the desired formaldehyde reduction while significantly reducing the addition level and reducing discoloration. No significant differences in release profiles or oxidation induction times were observed between the formulation selections.

[0204] Example 18 - Preparation of solid and liquid formulations containing 2-cyanoacetamide

[0205] Solid and liquid formulations containing cyanoacetamide were prepared according to the procedures described in Examples 5 and 6, and their compositions are shown in the following table. In the following, the aldehyde scavenger (AS) component is 2-cyanoacetamide, the antioxidant is Irganox 1010, the liquid carrier of Formulation X is Carrier A, and the solid carrier of Formulation IX is POM copolymer.

[0206]

[0207] Examples 19 and 20 - Evaluation of Solid and Liquid Formulations Containing 2-Cyanoacetamide

[0208] Solid and liquid formulations IX and X were added to Ultraform S2320-POM copolymers and plaques produced by injection molding with the following LDRs. Formaldehyde emission was evaluated as described in Evaluation 1, and L*, a*(D65), b*(D65) were evaluated as described in Evaluation 2.

[0209]

[0210] The control refers to the POM copolymer without additives.

[0211] The use of a solid masterbatch failed to achieve the target of 2 ppm in automotive applications (Example 19). The liquid formulation (Example 20) provided the desired formaldehyde reduction while significantly reducing the addition level and reducing discoloration. No significant differences in release profiles or oxidation induction times were observed between the formulation selections.

[0212] Examples 21 to 24 - Use of o-aminobenzamide as an aldehyde scavenger and synergistic effects of formulation components on formaldehyde release Same influence

[0213] Following the procedures generally described in Examples 8 to 11, the individual components or component mixtures contained in the liquid formulations were added to the POM copolymers at the indicated levels and then evaluated to determine the individual and / or collective effects on formaldehyde emission and optical properties. The details of the components and mixtures were evaluated and the results are provided in the following table.

[0214] In the case where a carrier and an antioxidant were used, the components were carrier A and Irganox 1010, respectively.

[0215]

[0216] The results show that the combination of aldehyde scavenger and liquid in Example 22 also provides very low formaldehyde emissions; and, when the scavenger, liquid and antioxidant are combined (Example 23), the formaldehyde emissions are even lower.

[0217] Examples 25 to 27 - Use of Compound X as an aldehyde scavenger and synergistic effects of formulation components on formaldehyde release

[0218] The individual components or mixtures of components contained in the liquid formulations were added to the POM copolymers at the indicated levels following the procedures generally described in Examples 8 to 11 and then evaluated to determine the individual and / or collective effects on formaldehyde emission and optical properties. The details of the components and mixtures were evaluated and the results are provided in the following table.

[0219] In the case where a carrier and an antioxidant were used, the components were carrier A and Irganox 1010, respectively.

[0220]

[0221] The results show that in Example 25, the combination of aldehyde scavenger and liquid provided low formaldehyde release; and, when the scavenger, liquid and antioxidant were combined (Example 27), the formaldehyde release was even lower.

[0222] Examples 28 to 31 - Use of Compound Y as an aldehyde scavenger and synergistic effects of formulation components on formaldehyde release

[0223] The individual components or mixtures of components contained in the liquid formulations were added to the copolymer POM at the indicated levels following the procedures generally described in, for example, Examples 8 to 11 and then evaluated to determine the individual and / or collective effects on formaldehyde emission and optical properties. The details of the ingredients and mixtures were evaluated and the results are provided in the following table.

[0224] In the case where a carrier and an antioxidant were used, the components were carrier A and Irganox 1010, respectively.

[0225]

[0226] For POM preparations, a variety of materials can be added to the preparations, including stabilizers such as hindered amine light stabilizers (HALS); acid scavengers such as calcium stearate and hydrotalcite; lubricants such as wax; BaSO4; TiO2; carbon black; pigments; aromatic polyamides; silica powder; polytetrafluoroethylene and UV stabilizers.

[0227] The invention is not limited to the details of the foregoing embodiments. The invention extends to any novel feature or any novel combination of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel step or any novel combination of the steps of any method or process disclosed in this specification (including any accompanying claims, abstract and drawings).

Claims

1. A method for reducing the aldehyde 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 preparation, wherein: The liquid formulation includes a liquid carrier and an aldehyde scavenger.

2. The method according to claim 1, characterized in that The method comprises the step of contacting a POM polymer with the liquid formulation.

3. The method according to claim 1 or 2, characterized in that: The POM is a POM homopolymer or a POM copolymer.

4. A method according to any preceding claim, wherein: The liquid formulation is a liquid at STP.

5. A method according to any preceding claim, wherein: The aldehyde scavenger is selected from the following classes of scavengers: (i) a scavenger AS2 comprising at least two component molecular fragments, each component molecular fragment comprising at least two hydrogen-substituted heteroatoms bonded to carbon atoms of the corresponding component molecular fragment; (ii) a scavenger AS5 comprising a compound (A), wherein the compound (A) comprises a first fragment, a second fragment and a third fragment, wherein: The first segment includes the following parts: wherein R' represents a substituent, and n is 0 to 4; The second segment includes the following parts: wherein R' represents a substituent, and n is 0 to 4; and The third segment includes the following parts: wherein R' represents a substituent, and n is 0 to 4; (iii) Scavenger AS7 having the general formula XXV: Where R 60 and R 61 independently represent a hydrogen atom or an optionally substituted, preferably unsubstituted alkyl, cycloalkyl or aromatic group; and Where R 62 and R 63 independently represents a hydrogen atom or an optionally substituted, preferably unsubstituted alkyl, cycloalkyl or aromatic group.

6. The method according to claim 5, wherein the aldehyde scavenger is selected from the following: o-aminobenzamide, 1,8-diaminonaphthalene, allantoin, 3,4-diaminobenzoic acid, malonamide, salicylanilide, 6-amino-1,3-dimethyluracil (DMU), 6-aminoisocytosine, 6-aminouracil, 6-amino-1-methyluracil; Scavenger AS5, which includes the following structure: wherein M represents a main fragment comprising a saturated hydrocarbon portion optionally containing a nitrogen atom; The scavenger AS7 has the formula XXV, wherein R 60 and R 61 independently represent a hydrogen atom or an unsubstituted alkyl or cycloalkyl group, R62 and R 63 independently represents a hydrogen atom or an unsubstituted alkyl or cycloalkyl group.

7. A method according to any preceding claim, wherein the aldehyde scavenger is selected from anthranilamide, cyanoacetamide or compound XX, wherein compound XX is 8. A method according to any preceding claim, wherein the aldehyde scavenger comprises the following moieties: wherein the carbon atom is part of a benzene ring; or the aldehyde scavenger comprises the following moiety:

9. A method according to any preceding claim, wherein the formulation comprises at least 30 wt%, preferably at least 40 wt%, more preferably at least 50 wt% of a liquid carrier; and / or comprises less than 90 wt%, preferably less than 80 wt% of a liquid carrier.

10. A method according to any preceding claim, wherein the liquid formulation comprises 50 to 90 wt% (e.g. 50 to 80 wt%) of a liquid carrier and 10 to 50 wt% (e.g. 20 to 50 wt%) of the aldehyde scavenger.

11. A method according to any preceding claim, wherein the liquid carrier is oil or glycol.

12. A method according to any preceding claim, wherein the formulation comprises 0.5 wt% to 10 wt% antioxidant.

13. The method of claim 12, wherein the antioxidant comprises a sterically hindered phenolic compound.

14. The method of claim 13, wherein the antioxidant has the formula: Where L 50 is a linking moiety that includes an oxyalkylene moiety and one or more ester moieties.

15. The method according to any of the preceding claims, wherein the method reduces the aldehyde content in the POM polymer so that the POM polymer contains less than 2 ppm of aldehydes when evaluated according to VDA-275.

16. A polyoxymethylene (POM) polymer having a reduced aldehyde content, the POM polymer comprising an aldehyde scavenger according to any preceding claim or a reaction product between an aldehyde scavenger according to any preceding claim and an aldehyde.

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

18. The polymer of claim 16 or 17, wherein the POM polymer comprises a residual support according to any one of claims 1 to 15.

19. The polymer according to any one of claims 16 to 18, wherein the POM polymer comprises an antioxidant as described in any one of claims 1 to 15.

20. The polymer of any one of claims 16 to 19, wherein the POM polymer is in the form of particles.

21. A method for preparing an article or particle from a polyoxymethylene (POM) polymer, the method comprising: (a) selecting a liquid formulation comprising a liquid carrier as claimed in any one of claims 1 to 15 and an aldehyde scavenger; (b) contacting a POM polymer with the liquid formulation; and (c) forming the POM polymer into an article or particles, such as a shaped article.

22. The method of claim 21, wherein the article or particle comprises less than 2 ppm of aldehydes when evaluated according to VDA-275.

23. The method according to claim 21 or 22, wherein: In step (c), the POM polymer is melt processed to define the article or particle.

24. A method according to any one of claims 21 to 23, wherein the article or particles comprise one or more colorants and when formed into an article, the article comprises from 5 ppm to 500 ppm of colorant; when formed into particles, the particles comprise up to 35 wt% of colorant.

25. The method according to any one of claims 21 to 24, wherein: In the shaped article, the sum of the weight percentages of the one or more POM polymers and the aldehyde scavenger is at least 90 wt%, at least 95 wt%, or at least 98 wt%.

26. An article or particle having reduced aldehyde content made according to the method of any one of claims 21 to 25 and comprising a POM polymer and an aldehyde scavenger according to any one of the preceding claims.

27. The article or particle of claim 26, wherein the article comprises less than 2 ppm of aldehydes when evaluated according to VDA-275.

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