Polyoxymethylene polymer compositions for rotational molding applications

Abstract

A polymer composition for rotational molding applications is disclosed that contains a polyoxymethylene polymer in the form of particles. The polyoxymethylene polymer is selected to have physical properties and combined with one or more impact modifiers to produce hollow containers and other articles with improved physical properties, such as impact strength.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims priority to U.S. Provisional Patent Application No. 63 / 175,783, filed April 16, 2021, U.S. Provisional Patent Application No. 63 / 240,503, filed September 3, 2021, and U.S. Provisional Patent Application No. 63 / 296,578, filed January 5, 2022, each of which is incorporated by reference in its entirety into this specification. [Background technology]

[0002]

[0002] Hollow containers can be made using a variety of different types of molding processes and techniques. One particular type of process is called rotational molding. During rotational molding, a polymeric material is placed in a mold and heated above its softening temperature, which causes the polymeric material to melt and flow. During the heating process, the mold rotates about at least one axis, and typically at least two different axes. Centrifugal force causes the polymeric material to conform to the mold walls, forming a hollow container. Rotational molding offers various advantages, as the process can produce seamless hollow products of high complexity. However, the process window of the polymeric material has limited the use of rotational molding to certain types of polymers, such as polyethylene and polyamide polymers.

[0003]

[0003] Various attempts have been made to incorporate polyoxymethylene polymers into rotomolding applications to produce hollow containers, such as liquid tanks. Polyoxymethylene polymers offer good chemical resistance, rigidity, and elasticity. In fact, many polyoxymethylene polymers have low and sharp melting points and recrystallization characteristics compared to polyamide polymers, which may provide processing cycle time advantages. However, there have been problems in producing rotomolded hollow containers from polyoxymethylene polymers, especially those with suitable impact resistance compared to various other polymers.

[0004] In view of the above, polyoxymethylene polymers have been conventionally combined with various additives to improve the impact resistance of products made from the polymer compositions. For example, U.S. Patent No. 8,008,390 discloses polyoxymethylene polymer blends for rotational molding applications intended to improve impact resistance. U.S. Patent No. 8,008,390 is incorporated herein by reference.

[0005]

[0005] However, combining polyoxymethylene polymers with various additives to improve impact resistance for rotational molding applications has been problematic. For example, many hollow containers produced during rotational molding are intended to contain liquids. Combining polyoxymethylene polymers with various additives can adversely affect the permeability properties of the polymeric material, especially when tested against petroleum-based materials. Furthermore, adding additives to polyoxymethylene polymers during rotational molding can cause phase separation during the process, producing products that are not commercially suitable. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, there is currently a need for polyoxymethylene polymer compositions that are well suited for rotomolding applications. There is also a need for polyoxymethylene polymer compositions that can be rotomolded into single-layer, hollow containers having good fluid permeability properties. [Means for solving the problem]

[0007]

[0007] The present disclosure is generally directed to a powder composition comprised of polymer particles containing polyoxymethylene polymers, the powder composition being particularly formulated for use in rotational molding applications. For example, the powder has a particle size distribution that is not only well suited for the manufacture of articles by rotational molding, but can also be formulated to produce hollow containers with excellent physical properties, including impact strength, when filled with fluids such as gases and liquids, combined with excellent permeability properties that prevent the escape of liquid vapors and gases from the hollow container.

[0008]

[0008] In one embodiment, for example, the disclosure is directed to a polymer composition for rotomolding applications. The polymer composition includes polymer particles containing a polyoxymethylene polymer blended with one or more impact modifiers. The polyoxymethylene polymer can have a relatively low melt flow rate. For example, the melt flow rate of the polyoxymethylene polymer can be less than about 8 g / 10 min, such as less than about 5 g / 10 min, such as less than about 4 g / 10 min, such as less than about 3 g / 10 min, and generally greater than about 0.5 g / 10 min. The polyoxymethylene polymer can be present in the polymer composition in an amount of at least about 55% by weight. The one or more impact modifiers can be present in the polymer composition in an amount of about 4% to about 27% by weight.

[0009] The polymer particles can have a particle size distribution that has been found to be useful for rotational molding applications. For example, the polymer particles can have a particle size distribution such that at least 10% by weight of the particles have a particle size greater than about 625 microns, such as greater than about 630 microns, such as greater than about 635 microns, such as greater than about 640 microns. The polymer particles can also be D 10 The particle size distribution may be such that the particle size is from about 90 microns to about 300 microns, for example from about 110 microns to about 220 microns. 50 The particle size may be from about 150 microns to about 400 microns, for example, from about 175 microns to about 375 microns. 75The particle size may be from about 380 microns to about 680 microns, for example from about 400 microns to about 650 microns. The above particle size ranges are exemplary and smaller particle sizes may be used in certain applications.

[0010] A variety of different impact modifiers can be combined with the polyoxymethylene polymer. For example, the impact modifier can include one or more thermoplastic elastomers. In one aspect, for example, the impact modifier can be a thermoplastic polyurethane elastomer alone or in combination with a thermoplastic copolyester elastomer. In another embodiment, the impact modifier may include one or more thermoplastic copolyester elastomers. The thermoplastic copolyester elastomer can include a block copolymer of polybutylene terephthalate and polyether segments. Alternatively, the thermoplastic copolyester elastomer can include a thermoplastic ester ether elastomer.

[0011] The polyoxymethylene polymer contained in the polymer composition can be a polyoxymethylene copolymer. The polyoxymethylene polymer can contain a variety of different types of end groups or terminal groups. In one embodiment, the polyoxymethylene polymer contains hydroxyl groups in an amount less than about 10 mmol / kg, such as less than about 8 mmol / kg, such as less than about 6 mmol / kg, such as less than about 4 mmol / kg. When containing a relatively small amount of hydroxyl groups, the polymer composition may not contain a polyisocyanate. Alternatively, the polyoxymethylene polymer can have a large amount of hydroxyl groups in combination with a coupling agent that includes a polyisocyanate.

[0012]

[0012] The present disclosure is also directed to a container for liquids and gases, such as petroleum-based fuels. The container can include a seamless rotationally molded housing forming an opening configured to receive a fluid. The housing can include an interior enclosure surrounded by a wall. The wall can be made from a polymer composition including a polyoxymethylene polymer having a melt flow rate of less than about 5 g / 10 min. The polymer composition can further include one or more impact modifiers present in the polymer composition in an amount of about 4% to about 27% by weight. The wall of the housing can be made from only a single layer of the polymer composition and has a melt flow rate of 4 g·mm / m at 40°C according to SAE test J2665. 2 For example, a wall can have a standard permeability of about 3.5 g mm / m at 40°C. 2 / day.

[0013] The wall was also tested in accordance with US EPA 40 CFR Part 1060.520 test method and had a hardness of about 1.1 g / m 2 / day, e.g., about 0.9 g / m 2 / day, e.g., about 0.7 g / m 2 / day (and generally about 0.01 g / m 2 / day). Moreover, even when made from a single layer of material, the walls can exhibit a stabilization parameter (r 2 The above results are obtained with an immersion period of 10 weeks and a test temperature of 28°C.

[0014]

[0014] The container may have a multiaxial impact strength of greater than about 5 ft-lbf at 23°C, such as greater than about 7.5 ft-lbf at 23°C, such as greater than about 10 ft-lbf at 23°C, such as greater than about 15 ft-lbf at 23°C, such as greater than about 20 ft-lbf at 23°C, such as greater than about 30 ft-lbf at 23°C, such as greater than about 40 ft-lbf at 23°C, and generally less than about 80 ft-lbf at 23°C. The wall thickness may be from about 0.5 mm to about 10 mm. In one embodiment, the container may be a fuel tank.

[0015]

[0015] Other features and aspects of the disclosure are described in more detail below.

[0016] A full and enabling disclosure of the present disclosure is more particularly set forth in the remainder of the specification, including reference to the accompanying drawings. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view of one embodiment of a container made in accordance with the present disclosure. [Diagram 2] FIG. 2 is a side view of the container shown in FIG. [Diagram 3] 1 is a graph of the internal temperature profile during a rotomolding cycle according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention.

[0018] It will be understood by those skilled in the art that this discussion is a description of exemplary embodiments only, and is not intended to limit the broad aspects of the present disclosure.

[0018]

[0019] The present disclosure is generally directed to a polymer composition comprising a polyoxymethylene polymer and one or more impact modifiers. The polymer composition is in the form of a powder having a controlled particle size. Furthermore, the polyoxymethylene polymer can be specifically selected to have thermal properties well suited for use in rotational molding applications.

[0019]

[0020] The polymer compositions of the present disclosure containing one or more impact modifiers have been found to have dramatically improved properties that allow them to be more easily processed during rotomolding processes to produce hollow containers or articles with better physical properties and fewer defects. One or more impact modifiers can, for example, reduce the stiffness of polyoxymethylene polymers, increase the impact resistance of articles made from the polymer compositions, and reduce the shrinkage properties of the polymer. The polymer compositions are also formulated to have a particle size that improves the operating window of the polymer. For example, rotomolding is a relatively slow molding process. For example, rotomolding processes typically have longer cycle times than many other processes, such as injection molding. However, the polymer compositions of the present disclosure are formulated to be more thermally stable for longer cycle times and have thermal properties that allow the polymer compositions to flow over the mold in a manner that creates fewer voids.

[0020]

[0021] The use of polyoxymethylene polymers in rotational molding processes can provide various advantages and benefits. For example, polyoxymethylene copolymers have a linear structure with high crystalline quality, providing various properties including excellent abrasion resistance, long-term fatigue resistance, toughness, and creep resistance, as well as excellent resistance to moisture, solvents, and strong alkalis. The chemical structure of polyoxymethylene polymers provides high stability against thermal and oxidative degradation compared to many different polymers. The use of polyoxymethylene copolymers is actually more thermally stable and resistant to degradation than polyoxymethylene homopolymers. Polyoxymethylene polymers are formulated to enhance impact resistance while maintaining excellent permeability properties. For example, the polymer compositions of the present disclosure can be used to manufacture containers or hollow containers for containing any of a variety of types of fluids, including compressed gases and fuels. The containers have excellent impact resistance while being relatively impermeable to fuel vapors and other gases. Indeed, the polymer compositions of the present disclosure can be used to manufacture single-layer containers or vessels that provide impact resistance and excellent permeation properties without the need to add an additional layer to the container wall or to subject the container to a secondary process such as fluorination.

[0021]

[0022] As mentioned above, the polymer composition of the present disclosure is in the form of a powder. The powder composition has a controlled particle size distribution, which has been found to provide advantages and benefits during the rotational molding process. For example, the powder can have flow properties like a fluid. Thus, the polymer composition is easy to handle when loading into a mold and circulates uniformly within the mold during the rotation of the mold. For example, the particle size distribution can lead to the formation of articles with higher precision and resistance.

[0022]

[0023] The particle size distribution, in combination with the combination of the various components that make up the polymer composition, can also produce a polymer composition with less shrinkage and less internal stress during the molding process. The particle size distribution in combination with the blending also provides a relatively large operating window during the molding process. For example, the polymer composition has thermal properties that make the composition more stable and well suited for longer cycle times. In this way, when the polymer composition is melted, it flows uniformly over the surface of the mold, resulting in a molded article with little or no voids.

[0023]

[0024] In one embodiment, the particle size distribution of the polymer composition includes a relatively large particle size to allow for longer cycle times (although smaller particle sizes may be used in some applications).For example, in one aspect, more than 10% by weight of the particles can have a particle size of more than about 625 microns, such as more than about 630 microns, such as more than about 635 microns, such as more than about 640 microns.In certain applications, more than 10% by weight of the particles can have a particle size of more than about 660 microns, such as more than about 680 microns, such as more than about 700 microns.The above 10% by weight of the particles generally have an average particle size of less than about 1200 microns, such as less than about 1000 microns, such as less than about 900 microns, such as less than about 850 microns.

[0024]

[0025] D 10 In addition to the particle size, the particle size distribution of the polymer composition is determined by D 50 Particle size, D 75 Particle size, and D 10 It can also be described as a particle size. For example, the powder composition generally has a D of more than 150 microns, such as more than about 160 microns, for example more than about 175 microns, for example more than about 200 microns, for example more than about 225 microns, for example more than about 250 microns, for example more than about 275 microns, for example more than about 290 microns. 50 It can have a particle size. 50 The particle size is generally less than about 600 microns, such as less than about 550 microns, for example less than about 500 microns, such as less than about 450 microns.

[0025]

[0026] The polymer composition in the form of a powder generally has a D of greater than about 90 microns, such as greater than about 100 microns, for example greater than about 110 microns, such as greater than about 120 microns, for example greater than about 130 microns, and generally less than about 300 microns, for example less than about 250 microns, for example less than about 220 microns. 10 The powder composition may have a particle size (smallest particle) of generally more than about 380 microns, such as more than about 400 microns, such as more than about 420 microns, such as more than about 440 microns, and generally less than about 700 microns, such as less than about 650 microns, such as less than about 625 microns, such as less than about 600 microns, such as less than about 590 microns. 75 The particle size can be determined using a laser scattering particle size distribution analyzer, such as a Beckman Coulter LS 13 320 particle size analyzer.

[0026]

[0027] In an alternative embodiment, the particle size distribution of the polymer composition may include smaller particles than those described above when using certain types of polyoxymethylene polymers in combination with various impact modifiers.For example, in another embodiment, the polymer composition may have a particle size distribution such that 90% of the particles have a size less than about 500 microns.50% of the particles may have a particle size of about 450 microns to about 250 microns, for example, about 420 microns to about 300 microns.About 30% to about 50% by weight of the particles may have a particle size of about 250 microns to about 500 microns.

[0027]

[0028] In yet another embodiment, the particle size distribution of the polymer composition can be such that 90% of the particles have a size of less than about 420 microns, such as less than about 400 microns, such as less than about 380 microns. 50% by weight of the particles can have a particle size of about 250 microns to about 177 microns. About 45% by weight to about 60% by weight of the particles can have a particle size of about 420 microns to about 177 microns, such as about 350 microns to about 170 microns, such as about 280 microns to about 177 microns. In addition to using light scattering to determine particle size, in an alternative embodiment, sieve testing can be used. For example, particle size (by weight) can be determined using a RO-TAP sieve shaker.

[0028]

[0029] As mentioned above, the polymer compositions of the present disclosure generally contain a polyoxymethylene polymer in combination with one or more impact modifiers, in addition to various other ingredients. The polyoxymethylene polymer may be a polyoxymethylene copolymer.

[0029]

[0030] The preparation of polyoxymethylene polymers can be carried out by polymerizing polyoxymethylene-forming monomers, such as trioxane or a mixture of trioxane and a cyclic acetal, such as dioxolane, in the presence of a molecular weight regulator, such as a glycol. According to one embodiment, the polyoxymethylene is at least 50 mol%, such as at least 75 mol%, such as at least 90 mol%, and even such as at least 97 mol% -CH 2 It is a homopolymer or copolymer containing O-repeating units.

[0030]

[0031] In one embodiment, a polyoxymethylene copolymer is used. The copolymer can contain about 0.1 mol% to about 20 mol%, and in particular about 0.5 mol% to about 10 mol% of repeating units, which include a saturated or ethylenically unsaturated alkylene group having at least two carbon atoms, or a cycloalkylene group having a sulfur atom or an oxygen atom in the chain, and may include one or more substituents selected from the group consisting of alkylcycloalkyl, aryl, aralkyl, heteroaryl, halogen, or alkoxy. In one embodiment, a cyclic ether or acetal is used, which can be introduced into the copolymer via a ring-opening reaction.

[0031]

[0032] Preferred cyclic ethers or acetals are of the formula:

[0032] [ka]

[0033] (wherein x is 0 or 1; R 2 is C 2 ~C 4 - an alkylene group, where appropriate, C 1 ~C 4 - an alkyl group or C 1 ~C 4 -alkoxy groups and / or one or more substituents which are halogen atoms, preferably chlorine atoms). Merely by way of example, mention may be made of ethylene oxide, propylene 1,2-oxide, butylene 1,2-oxide, butylene 1,3-oxide, 1,3-dioxane, 1,3-dioxolane, 1,3-dioxepane as cyclic ethers and also linear oligo- or polyformals, such as polydioxolanes or polydioxepanes, as comonomers. It is particularly advantageous to use copolymers consisting of 99.5 to 95 mol % of trioxane and 0.5 to 5 mol %, for example 0.5 to 4 mol %, of one of the abovementioned comonomers.

[0034]

[0033] In certain embodiments of the present disclosure, the polyoxymethylene copolymer incorporated in the powder composition contains a relatively small amount of comonomer. For example, the polyoxymethylene copolymer can contain a comonomer such as dioxolane in an amount of less than about 5% by weight, such as less than about 2% by weight, such as less than about 1.5% by weight, such as less than about 1% by weight, such as less than about 0.75% by weight, such as less than about 0.7% by weight. The comonomer content is generally greater than about 0.3% by weight, such as greater than about 0.5% by weight.

[0035]

[0034] The polymerization can be carried out as a precipitation polymerization or a melt polymerization. By suitable selection of the polymerization parameters such as the polymerization time or the amount of the molecular weight regulator, the molecular weight of the resulting polymer, and therefore the MVR value, can be adjusted.

[0036]

[0035] The polyoxymethylene polymer incorporated into the polymer composition can have a variety of different end groups or terminal groups depending on the specific application and other components contained in the composition. In one aspect, the polyoxymethylene polymer is relatively thermally stable. For example, the polyoxymethylene polymer can contain hemiformal groups in an amount of less than about 2 mol%, for example, less than about 1.5 mol%, for example, less than about 1 mol%, for example, less than about 0.8 mol%, for example, less than about 0.6 mol%.

[0037] The amount of hydroxyl end groups of the polyoxymethylene polymer may depend on whether a polyisocyanate coupling agent is present in the composition. In the absence of a polyisocyanate coupling agent, for example, the polyoxymethylene polymer may have a terminal hydroxyl group content of less than about 10 mmol / kg, for example less than about 8 mmol / kg, for example less than about 6 mmol / kg, for example less than about 4 mmol / kg.

[0038] Alternatively, the polyoxymethylene polymer may contain a higher amount of terminal hydroxyl groups. In one embodiment, the polyoxymethylene polymer has a terminal hydroxyl group content of at least 15 mmol / kg, such as at least 18 mmol / kg, such as at least 20 mmol / kg, such as more than about 25 mmol / kg, such as more than about 30 mmol / kg, such as more than about 40 mmol / kg, such as more than about 50 mmol / kg. The terminal hydroxyl group content is generally less than about 300 mmol / kg, such as less than about 200 mmol / kg, such as less than about 100 mmol / kg. In one embodiment, the terminal hydroxyl group content is in the range of 18 to 50 mmol / kg. The determination of the hydroxyl group content in the polyoxymethylene polymer may be carried out by the method described in JP-A-2001-11143.

[0039] In addition to the terminal hydroxyl groups, the polyoxymethylene polymers may have other terminal groups conventional for these polymers. Examples of these include alkoxy groups, formates, acetate groups, or aldehyde groups. In one embodiment, the polyoxymethylene polymer has a terminal NH 2 According to one embodiment, the polyoxymethylene may contain at least 50 mol%, such as at least 75 mol%, such as at least 90 mol%, or even at least 95 mol% -CH 2 It is a copolymer containing O-repeating units.

[0040]

[0039] The polyoxymethylene polymer can have any suitable molecular weight. The molecular weight of the polymer can be, for example, from about 4,000 grams / mol to about 100,000 grams / mol. The polyoxymethylene polymer can have, for example, a molecular weight greater than about 10,000 grams / mol, for example, greater than about 15,000 grams / mol, for example, greater than about 20,000 grams / mol, for example, greater than about 30,000 grams / mol, for example, greater than about 40,000 grams / mol, and generally less than about 90,000 grams / mol.

[0041]

[0040] The polyoxymethylene polymer present in the composition can generally have a melt flow index (MFI) in the range of about 0.1 to about 200 g / 10 min, as determined according to ISO 1133 at 190°C and 2.16 kg. However, in one embodiment, the polyoxymethylene polymer has a relatively low melt flow index. It has been found that a lower melt flow index results in a polymer composition with a larger operating window when used in a rotational molding process. Furthermore, a lower melt flow rate can lead to better physical properties. For example, the polyoxymethylene polymer can have a melt flow rate of less than about 8 g / 10 min, such as less than about 5 g / 10 min, such as less than about 4 g / 10 min, such as less than about 3 g / 10 min, such as less than about 2 g / 10 min, such as less than about 1 g / 10 min, and generally greater than about 0.5 g / 10 min.

[0042] The polyoxymethylene polymer may be present in the polyoxymethylene polymer composition in an amount of at least 40% by weight, such as at least 45% by weight, such as at least 55% by weight, such as at least 60% by weight, such as at least 70% by weight, such as at least 80% by weight. The polyoxymethylene polymer may be present in an amount of less than about 96% by weight, such as less than about 85% by weight, such as less than about 80% by weight, such as less than about 75% by weight.

[0043]

[0042] In accordance with the present disclosure, the polyoxymethylene polymer is combined with one or more impact modifiers. Examples of impact modifiers that can be incorporated into the composition include thermoplastic elastomers, methacrylate butadiene styrene, styrene acrylonitrile, and mixtures thereof. In one embodiment, the impact modifier can be a core-shell impact modifier. Combinations of different impact modifiers may be used to improve various properties of the polymer composition or articles made therefrom. For example, the polymer composition can include two or more thermoplastic elastomers.

[0044] A variety of different thermoplastic elastomers can be used as impact modifiers. Thermoplastic elastomers well suited for use in the present disclosure are polyester elastomers (TPE-E), thermoplastic polyamide elastomers (TPE-A), and especially thermoplastic polyurethane elastomers (TPE-U). The above thermoplastic elastomers have active hydrogen atoms that can react with coupling agents and / or polyoxymethylene polymers. Examples of such groups include urethane groups, amide groups, amino groups, or hydroxyl groups. For example, the flexible segments of the terminal polyester diols of the thermoplastic polyurethane elastomers have hydrogen atoms that can react with, for example, isocyanate groups.

[0045] In certain embodiments, thermoplastic polyurethane elastomers are used as impact modifiers alone or in combination with other impact modifiers. For example, the thermoplastic polyurethane elastomers may have a soft segment of a long-chain diol (dial) and a hard segment derived from a diisocyanate and a chain extender. In one embodiment, the polyurethane elastomer is a type of polyester prepared by reacting a long-chain diol with a diisocyanate to produce a polyurethane prepolymer with isocyanate-terminated groups, and then chain extending the prepolymer with a diol chain extender. Representative long-chain diols are polyester diols, such as poly(butylene adipate) diol, polyethylene adipate) diol, and poly(E-caprolactone) diol; and polyether diols, such as poly(tetramethylene ether) glycol, poly(propylene oxide) glycol, and poly(ethylene oxide) glycol. Suitable diisocyanates include 4,4'-methylenebis(phenylisocyanate), 2,4-toluene diisocyanate, 1,6-hexamethylene diisocyanate and 4,4'-methylenebis-(cycloxylisocyanate). Suitable chain extenders include C 2 ~C 6Aliphatic diols, such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol. One example of a thermoplastic polyurethane is characterized as being essentially poly(adipic acid-co-butylene glycol-co-diphenylmethane diisocyanate).

[0046] In one embodiment, the impact modifier may be a polyester-based thermoplastic polyurethane. The polyester-based thermoplastic polyurethane may have, for example, a Shore A hardness of about 80 to about 90, such as about 83 to about 87. The thermoplastic polyurethane may have a Shore D hardness of about 33 to about 43, such as about 35 to about 39.

[0047] In an alternative embodiment, a carbonate-based thermoplastic polyurethane block copolymer can be used. The carbonate-based thermoplastic polyurethane elastomer can have the same Shore A and Shore D hardness ranges as described above.

[0048] In one embodiment, the thermoplastic elastomer may include a thermoplastic polyester elastomer. The thermoplastic polyester elastomer may be, for example, a thermoplastic copolyester elastomer including a thermoplastic ester ether elastomer. In one aspect, the thermoplastic polyester elastomer may be a thermoplastic copolyester elastomer including a block copolymer of polybutylene terephthalate and polyether segments.

[0049] In one embodiment, the polymer composition may contain a segmented thermoplastic copolyester. The thermoplastic polyester elastomer may include, for example, a multi-block copolymer. Useful segmented thermoplastic copolyester elastomers include a multiplicity of repeating long and short chain ester units linked from head to tail via ester linkages. The long chain units are represented by the formula:

[0050] [ka]

[0051] The short chain unit is represented by the formula

[0052] [ka]

[0053] where G is a divalent radical remaining after removal of a terminal hydroxyl group from a long chain polymeric glycol having a number average molecular weight in the range of about 600 to 6,000 and a melting point less than about 55° C., R is a hydrocarbon radical remaining after removal of a carboxyl group from a dicarboxylic acid having a molecular weight less than about 300, and D is a divalent radical remaining after removal of a hydroxyl group from a low molecular weight diol having a molecular weight less than about 250.

[0054] The short chain ester units in the copolyetherester provide from about 15 to 95% by weight of the copolyetherester, and from about 50 to 100% of the short chain ester units in the copolyetherester are identical.

[0055] The term "long chain ester unit" refers to the reaction product of a long chain glycol with a dicarboxylic acid. The long chain glycol is a polymeric glycol having a terminal (or as close to terminal as possible) hydroxy group, a molecular weight greater than about 600, for example about 600 to 6000, a melting point less than about 55°C, and a carbon to oxygen ratio of about 2.0 or greater. The long chain glycol is generally a poly(alkylene oxide) glycol or a glycol ester of a poly(alkylene oxide) dicarboxylic acid. Optionally, any substituent that does not prevent polymerization of the compound with the glycol or dicarboxylic acid can be present. The hydroxy functionality of the long chain glycol reacted to form the copolyester can be a terminal group as far as possible. The terminal hydroxy group can be located in an end-capping glycol unit different from the chain, i.e., the ethylene oxide end group of a poly(propylene oxide glycol).

[0056] The term "short chain ester units" refers to low molecular weight compounds or polymer chain units having a molecular weight less than about 550. They are made by reacting low molecular weight diols (less than about 250) with dicarboxylic acids.

[0057]

[0052] The dicarboxylic acids may include the condensation polymerization equivalents of the dicarboxylic acids, i.e., their esters, or ester-forming derivatives such as acid chlorides and anhydrides, or other derivatives which behave substantially similarly to the dicarboxylic acids in polymerization reactions with glycols.

[0058]

[0053] The dicarboxylic acid monomers for the elastomers have a molecular weight of less than about 300. They can be aromatic, aliphatic, or cycloaliphatic. The dicarboxylic acids can contain any substituent or combination thereof that does not interfere with the polymerization reaction. Representative dicarboxylic acids include terephthalic acid, and isophthalic acid, bibenzoic acid, substituted dicarboxy compounds having a benzene nucleus, such as bis(p-carboxyphenyl)methane, p-oxy-(p-carboxyphenyl)benzoic acid, ethylene-bis(p-oxybenzoic acid), 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, phenanthralenedicarboxylic acid, anthracenedicarboxylic acid, 4,4'-sulfonyldibenzoic acid, and the like, as well as C 1 ~C 10 Included are alkyl and other ring substituted derivatives thereof, such as halo, alkoxy or aryl derivatives. Hydroxy acids such as p(β-hydroxyethoxy)benzoic acid can also be used, so long as an aromatic dicarboxylic acid is also present.

[0059] Representative aliphatic and cycloaliphatic acids are sebacic acid, 1,3- or 1,4-cyclohexanedicarboxylic acid, adipic acid, glutaric acid, succinic acid, carbonic acid, oxalic acid, itaconic acid, azelaic acid, diethylmalonic acid, fumaric acid, citraconic acid, allylmalonic acid, 4-cyclohexene-1,2-dicarboxylic acid, pimelic acid, suberic acid, 2,5-diethyladipic acid, 2-ethylsuberic acid, 2,2,3,3-tetramethylsuccinic acid, cyclopentanedicarboxylic acid, decahydro-1,5-(or 2,6-)naphthylenedicarboxylic acid, 4,4'-bicyclohexyldicarboxylic acid, 4,4'-methylenebis(cyclohexylcarboxylic acid), 3,4-furandicarboxylate, and 1,1-cyclobutanedicarboxylate.

[0060]

[0055] The dicarboxylic acids may have a molecular weight of less than about 300. In one embodiment, phenylenedicarboxylic acids such as terephthalic acid and isophthalic acid are used. Among the low molecular weight (less than about 250) diols that react to form the short chain ester units of the copolyester are acyclic, alicyclic, and aromatic dihydroxy compounds. Included are diols having 2 to 15 carbon atoms, such as ethylene, propylene, isobutylene, tetramethylene, pentamethylene, 2,2-dimethyltrimethylene, hexamethylene, and decamethylene glycols, dihydroxycyclohexane, cyclohexanedimethanol, resorcinol, hydroquinone, 1,5-dihydroxynaphthalene, and the like. Also included are aliphatic diols containing 2 to 8 carbon atoms. Among the bisphenols that can be used are bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)methane, and bis(p-hydroxyphenyl)propane. Equivalent ester-forming derivatives of the diols are also useful (e.g., ethylene oxide or ethylene carbonate can be used in place of ethylene glycol). The low molecular weight diols also include such equivalent ester-forming derivatives.

[0061]

[0057] Long chain glycols which can be used in preparing the polymers include poly(alkylene oxide) glycols, such as polyethylene glycol, poly(1,2- and 1,3-propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(pentamethylene oxide) glycol, poly(hexamethylene oxide) glycol, poly(heptamethylene oxide) glycol, poly(octamethylene oxide) glycol, poly(nonamethylene oxide) glycol, and poly(1,2-butylene oxide) glycol; random and block copolymers of ethylene oxide and 1,2-propylene oxide, and polyformals prepared by reacting formaldehyde with a glycol, such as pentamethylene glycol, or a mixture of glycols, such as a mixture of tetramethylene and pentamethylene glycol.

[0062] Additionally, dicarboxymethyl acids of poly(alkylene oxides), such as polytetramethylene oxide HOOCCH 2 (OCH 2 CH 2 CH 2 CH 2 ) x OCH 2 Long chain glycols can be formed in situ, such as those derived from COOH IV. Polythioether glycols and polyester glycols also provide useful products. When using polyester glycols, care must generally be taken to suppress the tendency for interconversion during melt polymerization, although certain sterically hindered polyesters, such as poly(2,2-dimethyl-1,3-propylene adipate), poly(2,2-dimethyl-1,3-propylene / 2-methyl-2-ethyl-1,3-propylene 2,5-dimethyl terephthalate), poly(2,2-dimethyl-1,3-propylene / 2,2-diethyl-1,3-propylene, 1,4-cyclohexanedicarboxylate) and poly(1,2-cyclohexylenedimethylene / 2,2-dimethyl-1,3-propylene-1,4-cyclohexanedicarboxylate), are available under normal reaction conditions, and other more reactive polyester glycols can be used if short residence times are employed. Either polybutadiene or polyisoprene glycols, their copolymers, and the saturated hydrogenation products of these materials are also satisfactory long chain polymeric glycols. Additionally, glycol esters of dicarboxylic acids formed by oxidation of polyisobutylene diene copolymers are useful raw materials.

[0063] The above long chain dicarboxylic acids (IV) can be added as acids to the polymerization reaction mixture, but they will react with the low molecular weight diols present, which are always in excess, to form the corresponding poly(alkylene oxide) ester glycols, which then polymerize to form the G units of the polymer chain; these particular G units, when only one low molecular weight diol (corresponding to D) is employed, will have the structure

[0064] [ka]

[0065] When more than one diol is used, there can be a different diol cap at each end of the polymer chain unit. Such dicarboxylic acids can also react with long chain glycols, if present, to give materials having the same formula as V above, except that D is replaced with the polymeric residue of a long chain glycol. However, the extent to which this reaction occurs is fairly small, since the low molecular weight diol is present in significant molar excess.

[0066] Instead of a single low molecular weight diol, a mixture of such diols can be used. Instead of a single long chain glycol or its equivalent, a mixture of such compounds can be utilized, and instead of a single low molecular weight dicarboxylic acid or its equivalent, a mixture of two or more can be used in the preparation of the thermoplastic copolyester elastomers that can be employed in the compositions of the present invention. Thus, the letter "G" in formula II above can represent the residue of a single long chain glycol or the residue of several different glycols, the letter D in formula III can represent the residue of one or several low molecular weight diols, and the letter R in formulas II and III can represent the residue of one or several dicarboxylic acids. When using an aliphatic acid that contains a mixture of geometric isomers, such as the cis-trans isomers of cyclohexanedicarboxylic acid, the different isomers should be considered as different compounds that form different short chain ester units with the same diol in the copolyester. The copolyester elastomers can be produced by conventional transesterification reactions.

[0067]

[0061] Copolyetheresters with alternating random length sequences of long or short chain oxyalkylene glycols can contain repeating high melting blocks that are crystallizable and substantially amorphous blocks with relatively low glass transition temperatures. In one embodiment, the hard segments can be composed of tetramethylene terephthalate units, and the soft segments can be derived from aliphatic polyethers and polyester glycols. Particularly advantageously, the material resists deformation at surface temperatures due to the presence of a network of microcrystals formed by partial crystallization of the hard segments. The ratio of hard and soft segments determines the properties of the material. Therefore, another advantage of thermoplastic polyester elastomers is that soft elastomers and hard elastoplastics can be produced by varying the ratio of hard and soft segments.

[0068] In one particular embodiment, the polyester thermoplastic elastomer has the formula: -[4GT] x [BT] y where 4G is butylene glycol, such as 1,4-butanediol, B is poly(tetramethylene ether glycol), T is terephthalate, x is from about 0.60 to about 0.99, and y is from about 0.01 to about 0.40.

[0069] In one embodiment, the thermoplastic polyester elastomer can be a block copolymer of polybutylene terephthalate and polyether segments and can have a structure as follows:

[0070] [ka]

[0071] where a and b are integers and can range from 2 to 10,000. The ratio between the hard and soft segments in the block copolymers described above can be varied to change the properties of the elastomer. In one embodiment, the density of the polyester elastomer shown above is about 1.05 g / cm 3 to about 1.15 g / cm 3 , for example, about 1.08 g / cm 3 to about 1.1 g / cm 3 It could be.

[0072] In one embodiment, the polyoxymethylene polymer is combined with an impact modifier, such as a thermoplastic polyester elastomer, having a melting temperature similar to that of the polyoxymethylene polymer. For example, in one aspect, the impact modifier is selected such that the melting temperature of the impact modifier is within about 8°C, such as within about 5°C, such as within about 4°C, such as within about 3°C, of ​​the melting temperature of the polyoxymethylene polymer. For example, an impact modifier, such as a polyester elastomer, can be selected with a melting temperature of about 150°C to about 185°C, such as about 158°C to about 172°C, such as about 163°C to about 169°C. The melting temperature can be determined according to ISO test 11357-1 / -3 (10°C / min) or according to ASTM test D3417 (DSC).

[0073] In one embodiment, the impact modifier, such as a thermoplastic polyester elastomer, can be selected to have a melting temperature lower than the melting temperature of the polyoxymethylene polymer. For example, the melting temperature of the impact modifier can be less than about 164°C, such as less than about 161°C, such as less than about 158°C, such as less than about 155°C, such as less than about 153°C, and generally greater than about 140°C, such as greater than about 145°C, such as greater than about 148°C.

[0074] In an alternative embodiment, the impact modifier may include a non-aromatic polymer, which refers to a polymer that does not contain aromatic groups on the polymer backbone. Such polymers include acrylate polymers and / or graft copolymers containing olefins. For example, an olefin polymer may serve as the graft base and may be grafted to at least one vinyl polymer or one ether polymer. In yet another embodiment, the graft copolymer may have a polydiene-based elastomeric core and a hard or soft graft envelope made of (meth)acrylate and / or (meth)acrylonitrile.

[0075] Examples of the impact modifiers mentioned above include ethylene-acrylic acid copolymers, ethylene-maleic anhydride copolymers, ethylene-alkyl (meth)acrylate-maleic anhydride terpolymers, ethylene-alkyl (meth)acrylate-glycidyl (meth)acrylate terpolymers, ethylene-acrylic acid ester-methacrylic acid terpolymers, ethylene-acrylic acid ester-maleic anhydride terpolymers, ethylene-methacrylic acid-alkali metal salt of methacrylic acid (ionomer) terpolymers, and the like. In one embodiment, for example, the impact modifier can include a random terpolymer of ethylene, methyl acrylate, and glycidyl methacrylate. The terpolymer can have a glycidyl methacrylate content of about 5% to about 20%, for example about 6% to about 10%. The terpolymer may have a methyl acrylate content of about 20% to about 30%, for example about 24%.

[0076] The impact modifier may be a linear or branched, homopolymer or copolymer (e.g., random, graft, block, etc.) containing epoxy functionalization, e.g., terminal epoxy groups, backbone oxirane units, and / or pendant epoxy groups. For example, the impact modifier may be a copolymer containing at least one monomer component having epoxy functionalization. The monomer units of the impact modifier may be different. For example, the impact modifier may contain epoxy-functional methacrylic monomer units. As used herein, the term methacrylic generally refers to both acrylic and methacrylic monomers, as well as their salts and esters, e.g., acrylate and methacrylate monomers. Epoxy-functional methacrylic monomers that may be incorporated into the impact modifier include, but are not limited to, those containing 1,2-epoxy groups, such as glycidyl acrylate and glycidyl methacrylate. Other suitable epoxy-functional monomers include allyl glycidyl ether, glycidyl ethacrylate, and glycidyl itaconate.

[0077]

[0069] Examples of other monomers include, for example, ester monomers, olefin monomers, amide monomers, and the like. In one embodiment, the impact modifier can include at least one linear or branched α-olefin monomer, such as one having 2 to 20 carbon atoms, or 2 to 8 carbon atoms. Specific examples include ethylene; propylene; 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene; 1-pentene; 1-pentene with one or more methyl, ethyl, or propyl substituents; 1-hexene with one or more methyl, ethyl, or propyl substituents; 1-heptene with one or more methyl, ethyl, or propyl substituents; 1-octene with one or more methyl, ethyl, or propyl substituents; 1-nonene with one or more methyl, ethyl, or propyl substituents; ethyl, methyl, or dimethyl substituted 1-decene; 1-dodecene; and styrene.

[0078] In one embodiment, the impact modifier can be a terpolymer with epoxy functionalization. For example, the impact modifier can include a methacrylic component with epoxy functionalization, an α-olefin component, and a methacrylic component without epoxy functionalization. For example, the impact modifier can be poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate), which has the following structure:

[0079] [ka]

[0080] where a, b, and c are 1 or greater. In another embodiment, the impact modifier may be a random copolymer of ethylene, ethyl acrylate and maleic anhydride having the following structure:

[0081] [ka]

[0082] where x, y and z are 1 or greater.

[0072] The relative proportions of the various monomer components of the copolymer impact modifier are not particularly limited. For example, in one embodiment, the epoxy-functional methacrylic monomer component can form about 1% to about 25% by weight, or about 2% to about 20% by weight of the copolymer impact modifier. The α-olefin monomer can form about 55% to about 95% by weight, or about 60% to about 90% by weight of the copolymer impact modifier. If employed, other monomer components (e.g., non-epoxy-functional methacrylic monomers) may comprise about 5% to about 35% by weight, or about 8% to about 30% by weight of the copolymer impact modifier.

[0083] The molecular weight of the impact modifiers can vary widely. For example, the impact modifiers can have a number average molecular weight of about 7,500 to about 250,000 g / mole, in some embodiments about 15,000 to about 150,000 g / mole, in some embodiments about 20,000 to 100,000 g / mole, with a polydispersity index typically ranging from 2.5 to 7.

[0084]

[0074] In general, the impact modifier(s) may be present in the polymer composition in an amount of about 2% to about 45% by weight, such as about 4% to about 27% by weight, including all increments of 1% by weight therebetween.For example, the impact modifier(s) may be present in the polymer composition in an amount greater than about 6% by weight, such as greater than about 8% by weight, such as greater than about 10% by weight, such as greater than about 12% by weight, such as greater than about 14% by weight, such as greater than about 16% by weight, such as greater than about 20% by weight, such as greater than about 25% by weight, such as greater than about 30% by weight, such as greater than about 35% by weight, and generally less than about 50% by weight, such as less than about 40% by weight, such as less than about 25% by weight, such as less than about 23% by weight.

[0085] As mentioned above, in various embodiments, the polymer composition can contain more than one impact modifier. For example, in one embodiment, the polymer composition can contain a thermoplastic polyurethane elastomer in combination with a thermoplastic polyester elastomer. For example, the thermoplastic polyester elastomer can be a thermoplastic ester ether elastomer. In one embodiment, the thermoplastic polyurethane elastomer can be combined with a thermoplastic copolyester elastomer comprising a block copolymer of polybutylene terephthalate and polyether segments. By incorporating the block copolymer of polybutylene terephthalate and polyether segments into the polymer composition, the impact resistance can be significantly improved, especially at low temperatures. The weight ratio between the thermoplastic polyurethane elastomer and the thermoplastic copolyester elastomer can be from about 1:5 to about 5:1, such as from about 1:3 to about 3:1, such as from about 1.5:1 to about 1:1.5. In one aspect, for example, the thermoplastic polyurethane elastomer can be present in the polymer composition in an amount of about 5% to about 12% by weight, and the thermoplastic copolyester elastomer can be present in the polymer composition in an amount of about 5% to about 12% by weight. In one embodiment, the thermoplastic polyurethane elastomer can be present in the polymer composition in an amount of about 8% to about 15% by weight, for example, about 9% to about 11% by weight, and the thermoplastic copolyester elastomer can also be present in the polymer composition in an amount of about 8% to about 15% by weight, for example, about 9% to about 11% by weight.

[0086] In addition to the polyoxymethylene polymer and one or more impact modifiers, the polymer composition of the present disclosure can contain various other ingredients. For example, in one embodiment, polyalkylene glycols can be incorporated into the polymer composition to provide various advantages and benefits. For example, polyalkylene glycols can improve the flow properties of the particles and / or improve impact strength.

[0087] Polyalkylene glycols particularly well suited for use in the polymeric composition include polyethylene glycol, polypropylene glycol, and mixtures thereof. The molecular weight of the polyalkylene glycol varies depending on various factors, including the properties of the polyoxymethylene polymer and the processing conditions for producing the molded article. In one aspect, the polyalkylene glycol, such as polyethylene glycol, can have a relatively low molecular weight. For example, the molecular weight can be less than about 10,000 g / mol, such as less than about 8,000 g / mol, such as less than about 6,000 g / mol, such as less than about 4,000 g / mol, and generally greater than about 1000 g / mol, such as greater than about 2000 g / mol. In one embodiment, a polyethylene glycol plasticizer having a molecular weight of about 2000 g / mol to about 5000 g / mol is incorporated into the polymer composition.

[0088] In another embodiment, the polyalkylene glycol, such as polyethylene glycol, can be selected to have a higher molecular weight. For example, the molecular weight of the polyalkylene glycol can be about 10,000 g / mol or more, such as more than about 20,000 g / mol, such as more than about 30,000 g / mol, such as more than about 35,000 g / mol, and generally less than about 100,000 g / mol, such as less than about 50,000 g / mol, such as less than about 45,000 g / mol, such as less than about 40,000 g / mol.

[0089]

[0080] When present in the polymer composition, the polyalkylene glycol may be added in an amount greater than about 0.1 wt%, such as greater than about 0.3 wt%. The polyalkylene glycol may generally be present in the polymer composition in an amount less than about 5 wt%, such as less than about 3 wt%, such as less than about 1 wt%.

[0090] In one embodiment, in addition to one or more impact modifiers, the polymer composition may contain a coupling agent. The coupling agent may be used to compatibilize different components. For example, the coupling agent may bond the polyoxymethylene polymer and one or more impact modifiers. However, it should be understood that in one embodiment, the polymer composition is formulated to not contain a coupling agent.

[0091] In one embodiment, the coupling agent comprises a polyisocyanate, for example a diisocyanate, such as an aliphatic, cycloaliphatic and / or aromatic diisocyanate. The coupling agent may be in the form of an oligomer, such as a trimer or dimer.

[0092] In one embodiment, the coupling agent comprises a diisocyanate or triisocyanate, such as 2,2'-, 2,4'-, and 4,4'-diphenylmethane diisocyanate (MDI); 3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODD); toluene diisocyanate (TDI); polymeric MDI; carbodiimide modified 4,4'-diphenylmethane diisocyanate; para-phenylene diisocyanate (PPDI); meta-phenylene diisocyanate (MPDI); triphenylmethane-4,4'- and and triphenylmethane-4,4"-triisocyanate;naphthylene-1,5-diisocyanate;2,4'-, 4,4'- and 2,2-biphenyl diisocyanate;polyphenylene polymethylene polyisocyanate (PMDI) (also known as polymeric PMDI);mixtures of MDI and PMDI;mixtures of PMDI and TDI;ethylene diisocyanate;propylene-1,2-diisocyanate;trimethylene diisocyanate;butylene diisocyanate;bitolylene diisocyanate;tolidine diisocyanate;tetramethylene 1,2-Diisocyanate;Tetramethylene-1,3-diisocyanate;Tetramethylene-1,4-diisocyanate;Pentamethylene diisocyanate;1,6-Hexamethylene diisocyanate (HDI);Octamethylene diisocyanate;Decamethylene diisocyanate;2,2,4-Trimethylhexamethylene diisocyanate;2,4,4-Trimethylhexamethylene diisocyanate;Dodecane-1,12-diisocyanate;Dicyclohexylmethane diisocyanate;Cyclobutane-1,3-diisocyanate;Cyclohexyl San-1,2-diisocyanate;Cyclohexane-1,3-diisocyanate;Cyclohexane-1,4-diisocyanate;Diethylidene diisocyanate;Methylcyclohexylene diisocyanate (HTDI);2,4-Methylcyclohexane diisocyanate;2,6-Methylcyclohexane diisocyanate;4,4'-Dicyclohexyl diisocyanate;2,4'-Dicyclohexyl diisocyanate;1,3,5-Cyclohexane triisocyanate;Isocyanatomethylcyclohexane isocyanate;1-Isocyanato-3,3,5-Trimethyl-5-isocyanatomethylcyclohexane;Isocyanatoethylcyclohexane isocyanate;Bis(isocyanatomethyl)-cyclohexane diisocyanate;4,4'-Bis(isocyanatomethyl)dicyclohexane;2,4'-Bis(isocyanatomethyl)dicyclohexane;Isophorone diisocyanate (IPDI);Dimeryl diisocyanate, Dodecane-1,12-diisocyanate, 1,10-decamethylene diisocyanate, Cyclohexylene-1,2-diisocyanate, 1,10-decamethylene diisocyanate 1-chlorobenzene-2,4-diisocyanate, furfurylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,3-cyclobutane diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 4,4'-methylenebis(phenyl isocyanate), 1-methylene 1,3-bis(isocyanatomethyl)cyclohexane, 1,6-diisocyanato-2,2,4,4-tetramethylhexane, 1,6-diisocyanato-2,4,4-tetramethylhexane, trans-cyclohexane-1,4-diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, cyclo -Hexyl isocyanate, dicyclohexylmethane 4,4'-diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, m-phenylene diisocyanate, m-xylylene diisocyanate, m-tetramethylxylylene diisocyanate, p-phenylene diisocyanate, p,p'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-diphenyl-4,4'-biphenylene diisocyanate, 4,4'-Biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, metaxylylene diisocyanate, 2,4-toluene diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,4-chlorophenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, p,p'-diphenylmethane The diisocyanate is selected from 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, 4,4'-toluidine diisocyanate, dianidin diisocyanate, 4,4'-diphenylether diisocyanate, 1,3-xylylene diisocyanate, 1,4-naphthylene diisocyanate, azobenzene-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, or mixtures thereof.

[0093] In one embodiment, aromatic polyisocyanates are used, such as 4,4'-diphenylmethane diisocyanate (MDI).

[0085] When present, the coupling agent can be present in the composition in an amount generally from about 0.1% to about 5% by weight. In one embodiment, for example, the coupling agent can be present in an amount of from about 0.1% to about 2% by weight, for example, from about 0.2% to about 1% by weight. In an alternative embodiment, the coupling agent can be added to the polymer composition in a molar excess amount when comparing the amount of reactive groups of the coupling agent to the amount of functional groups of the polyoxymethylene polymer. As mentioned above, in one embodiment, the polymer composition does not contain a coupling agent. For example, in one embodiment, the polymer composition may be free of polyisocyanates. Indeed, in one aspect, various advantages and benefits may be realized by not including polyisocyanate compounds.

[0094] The polymer compositions of the present disclosure may also optionally contain stabilizers and / or various other additives. Such additives may include, for example, antioxidants, acid scavengers, UV stabilizers, or thermal stabilizers. Additionally, the polymer compositions may contain processing aids, such as adhesion promoters, or antistatic agents.

[0095] For example, in one embodiment, a UV stabilizer may be present. The UV stabilizer may include benzophenone, benzotriazole, or benzoic acid ester. Specific examples of UV stabilizers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 5,5'-methylenebiphenyl. 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol; 2-(2'-hydroxyphenyl)benzotriazoles, such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole, 2-(2' -hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole, and 2,2'-methylenebis(4-t-octyl-6-benzotriazolyl)phenol, phenyl salicylate, resorcinol monobenzoate, 2,4-di-t-butylphenyl-3',5'-di-t substituted oxanilides such as 2-ethyl-2'-ethoxyoxanilide and 2-ethoxy-4'-dodecyloxanilide; cyanoacrylates such as ethyl-.alpha.-cyano-.beta.,.beta.-diphenylacrylate and methyl-2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate or mixtures thereof.A specific example of an ultraviolet light absorber that may be present is UV 234, a high molecular weight ultraviolet light absorber of the hydroxylphenylbenzotriazole class. When present, the UV light absorber can be present in the polymer composition in an amount ranging from about 0.1% to about 2% by weight, for example from about 0.25% to about 1% by weight, based on the total weight of the polymer composition.

[0096] In one embodiment, the polymer composition may also contain formaldehyde scavengers, such as nitrogen-containing compounds. Primarily, among these are heterocyclic compounds having at least one nitrogen atom as a heteroatom adjacent to a carbon atom or carbonyl group substituted with an amino group, such as pyridine, pyrimidine, pyrazine, pyrrolidone, aminopyridine and compounds derived therefrom. Advantageous compounds of this nature are aminopyridines and compounds derived therefrom. Any aminopyridine is in principle suitable, such as 2,6-diaminopyridine, substituted aminopyridines and dimeric aminopyridines, as well as mixtures prepared from these compounds. Other advantageous materials are polyamides and dicyandiamide, urea and its derivatives, as well as pyrrolidones and compounds derived therefrom. Examples of suitable pyrrolidones include imidazolidinones and compounds derived therefrom, such as hydantoins, the derivatives of which are particularly advantageous, and among these compounds, particularly advantageous is allantoin and its derivatives. Other particularly advantageous compounds are triamino-1,3,5-triazine (melamine) and its derivatives, such as melamine-formaldehyde condensates and methylolmelamine. Oligomeric polyamides are also suitable in principle for use as formaldehyde scavengers. In one aspect, the formaldehyde scavengers can include melamine. In an alternative embodiment, the acid scavengers can be copolyamides. The copolyamides can be used alone or in combination with melamine.

[0097]

[0089] Additionally, the formaldehyde scavenger can be a guanidine compound, which can include aliphatic guanamine compounds, alicyclic guanamine compounds, aromatic guanamine compounds, heteroatom-containing guanamine compounds, etc. The formaldehyde scavenger can be present in the polymer composition in an amount ranging from about 0.005% to about 2% by weight, for example, from about 0.0075% to about 1% by weight, based on the total weight of the polymer composition.

[0098] However, in one embodiment, the polymer composition of the present disclosure can be formulated to be free of various formaldehyde scavengers that may in some embodiments adversely affect rotomolded articles made from the composition. For example, in one embodiment, the polymer composition can be formulated to be free of all formaldehyde scavengers, and in particular free of nitrogen-containing formaldehyde scavengers. Formaldehyde scavengers that may be excluded from the composition include guanamines, such as benzoguanamine, melamine, and melamine derivatives. In one embodiment, the only formaldehyde scavengers present in the polymer composition may be a copolyamide.

[0099] Still other additives which may be present in the composition are sterically hindered phenolic compounds which may function as antioxidants. Commercially available examples of such compounds include pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (IRGANOX® 1010, BASF), triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] (IRGANOX® 245, BASF), 3,3′-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionohydrazide] (IRGANOX® MD 1024, BASF), hexamethylene glycol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (IRGANOX® 259, BASF), and 3,5-di-tert-butyl-4-hydroxytoluene (LOWINOX® BHT, Chemtura). The above compounds may be present in the polymer composition in an amount ranging from about 0.01% by weight to about 1% by weight, based on the total weight of the polymer composition.

[0100] In one embodiment, the polymer composition of the present disclosure contains a significant amount of antioxidants and other stabilizers. For example, the polymer composition can be formulated to contain one or more sterically hindered phenolic compounds in an amount greater than about 0.2% by weight, such as greater than about 0.22% by weight, such as greater than about 0.3% by weight, and less than about 5% by weight, such as less than about 2% by weight. The inclusion of a large amount of antioxidant can improve the thermal stability of the polymer composition.

[0101]

[0093] Light stabilizers that may be present in the composition in addition to the UV stabilizer include sterically hindered amines. Hindered amine light stabilizers that can be used include N-methylated oligomeric compounds. In one embodiment, the light stabilizer can include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate. For example, one example of a hindered amine light stabilizer is ADK STAB LA-63 light stabilizer available from Adeka Palmarole. When present, the light stabilizer can be present in the polymer composition in an amount ranging from about 0.1% to about 2% by weight, for example, from about 0.25% to about 1% by weight, based on the total weight of the polymer composition.

[0102] In addition to the above components, the polymer composition can also contain an acid scavenger. The acid scavenger may include, for example, an alkaline earth metal salt. For example, the acid scavenger may include a calcium salt, such as calcium citrate. In one aspect, the calcium citrate is tricalcium citrate. Another acid scavenger well suited for use in the polymer composition is anhydrous calcium propionate. In one embodiment, the acid scavenger selected for use in the polymer composition is calcium stearate. Calcium stearate has been found to provide various advantages and benefits with respect to the properties obtained from molded articles made from the polymer composition. The calcium stearate can be, for example, calcium 12-hydroxystearate. The acid scavenger may be present in an amount ranging from about 0.01% to about 1% by weight, based on the total weight of the polymer composition.

[0103]

[0095] In one embodiment, a lubricant may be present. The lubricant may include a polymer wax composition. For example, a fatty acid amide may be used. One example of a fatty acid amide is ethylene bis(stearamide). Alternatively, the lubricant may include a polyethylene wax. The lubricant may generally be present in the polymer composition in an amount of about 0.01% to about 1% by weight.

[0104]

[0096] The polymer composition can also contain a nucleating agent that can enhance the crystallinity of the polyoxymethylene polymer. The nucleating agent can include, for example, oxymethylene terpolymers, talc particles, etc. Alternatively, the polymer composition can be formulated to not contain a nucleating agent. When present, the nucleating agent can be added to the polymer composition in an amount greater than about 0.1% by weight, for example greater than about 0.2% by weight, and generally less than about 1.5% by weight, for example less than about 0.8% by weight.

[0105] In one embodiment, one or more colorants can also be added to the polymer composition. The colorant can be a pigment or a dye. In one aspect, the colorant can be added as a masterbatch in combination with the polyoxymethylene polymer. The one or more colorants can be present in the polymer composition in an amount generally greater than about 0.1% by weight and generally less than about 2% by weight.

[0106] Any of the above additives can be added to the polymer composition alone or in combination with other additives. Generally, each additive is present in the polymer composition in an amount of less than about 5% by weight, for example, in an amount ranging from about 0.005% to about 2% by weight, for example, from about 0.0075% to about 1% by weight, for example, from about 0.01% to about 0.5% by weight, based on the total weight of the polymer composition.

[0107]

[0099] To form a powder from the polymer composition of the present disclosure, in one aspect, the components of the polymer composition can be mixed together and then melt mixed. For example, the components can be melt mixed in an extruder. The processing temperature can vary depending on the type of polyoxymethylene polymer selected for use in the application. In one embodiment, the processing temperature can be from about 165°C to about 200°C.

[0108]

[0100] Extruded strands can be produced which can then be pelletized. The pelletized compound can then be ground to a suitable particle size and suitable particle size distribution to produce a powder well suited for use in rotomolding.

[0109]

[0101] For example, any suitable hammer mill or granulator can be used to produce the powder composition. In one embodiment, cryogenic grinding can be used to produce particles having a relatively small size and uniform particle size distribution. Cryogenic grinding can produce powders having particles that are not only uniform in size, but also approximately spherical in shape.

[0110]

[0102] Once the polymer composition has been compounded and formed into a powder with a controlled particle size distribution, the polymer particles are loaded into a mold to produce a molded article. The polymer particles are particularly well suited for use in a rotational molding process. During rotational molding, the polymer particles are loaded into a mold, and the mold rotates about at least a first axis and a second axis while being heated. By heating the polymer composition to a melting temperature, the polymer composition flows and coats the inner wall of the mold to produce a hollow container.

[0111]

[0103] Particularly advantageously, the polymer composition of the present disclosure containing polyoxymethylene polymer can be incorporated into rotational molding applications without modification using conventional equipment. For example, the polymer particles of the present disclosure can be formulated to have bulk density and flow properties well suited for rotational molding. For example, when tested according to the ARM funnel test (100 grams), the particles can exhibit a funnel flow of less than about 35 seconds, such as less than about 30 seconds, such as less than about 25 seconds, such as less than about 20 seconds, and generally more than about 5 seconds. The particles can have an unapplied bulk density of more than about 0.37 g / cc, such as more than about 0.4 g / cc, such as more than about 0.42 g / cc, and generally less than about 0.6 g / cc.

[0112]

[0104] When producing rotational molded articles, no pre-drying of the powder is required, and no nitrogen is required during molding. Moreover, the polymer composition of the present disclosure does not require special coatings or tools, and can be easily demolded from the mold after cooling. The polymer composition of the present disclosure also shows excellent flow properties, even when molding complex designs.

[0113] Rotational molded articles can be produced in relatively fast cycle times according to the present disclosure. For example, at oven temperatures of about 400°F to about 450°F, a rotational molded article having a wall thickness of 3.8 mm can be produced in less than about 20 minutes, such as less than about 18 minutes, and generally more than about 10 minutes, such as more than about 15 minutes. At a wall thickness of 5.1 mm, the article can be produced in generally less than about 25 minutes, such as less than about 21 minutes, and generally more than about 12 minutes, such as more than about 18 minutes. Air cooling times are generally less than about 30 minutes. For example, when rotating in air, the cooling time can be about 0 to about 10 minutes. When rotating with forced air, the cooling time can be about 10 to about 20 minutes.

[0114]

[0106] For illustrative purposes only, Figure 3 shows one embodiment of a temperature cycle for rotomolding an article according to the present disclosure. Of particular advantage, the temperature profile is very similar to rotomolding polyethylene polymers or other polymers, including polyamide polymers. Thus, according to the present disclosure, polyoxymethylene polymers can be used to produce articles with dramatically improved properties at similar temperature and energy requirements. For example, when rotomolding, articles can be produced with an outer wall temperature below about 232°C, such as below about 228°C, such as below about 225°C, such as below about 220°C, and generally above about 210°C. The air temperature inside the part can generally be below about 220°C, such as below about 202°C, such as below about 198°C, such as below about 193°C, such as below about 190°C, and generally above about 150°C, such as above about 170°C. The above-mentioned internal air temperature is generally maintained for about 4 minutes to about 12 minutes. The demold temperature of the part can generally be up to about 93°C, for example from about 70°C to about 93°C.

[0115]

[0107] Thus, in accordance with the present disclosure, rotationally molded articles made from a single layer of material having a wall thickness of about 3.8 mm to about 5.1 mm can be produced in total cycle times (heating and cooling) of less than about 60 minutes, such as less than about 51 minutes, such as less than about 45 minutes, such as less than about 30 minutes, and generally more than about 15 minutes.

[0116] In one embodiment, the polymer composition can be used to manufacture a container 10, as shown in Figures 1 and 2. The container 10 can be, for example, a fuel tank and / or a tank designed to hold compressed gas. The fuel tank 10 can include a spout 12 for receiving a fluid and can include one or more walls 14.

[0117]

[0109] As shown in Figures 1 and 2, the container 10 can be formed without any seams. In this way, the container has no seams, which can dramatically improve the strength of the container, especially the impact resistance strength. The wall 14 can generally have a thickness of more than about 0.5 mm, for example more than about 1 mm, for example more than about 2 mm, and generally less than about 10 mm, for example less than about 8 mm, for example less than about 6 mm.

[0118]

[0110] Rotomoulded containers made according to the present disclosure have fewer voids and can therefore be formed with high density. The density of the polymer layer used to form the container, when containing impact modifiers, is about 1250 kg / m 3 For example, about 1260 kg / m 3 For example, about 1270 kg / m 3 For example, about 1280 kg / m 3 For example, about 1290 kg / m 3 For example, about 1300 kg / m 3 For example, about 1310 kg / m 3 For example, about 1350 kg / m 3 , and generally about 1450 kg / m 3 It may be less than.

[0119]

[0111] Any of a variety of different types of containers can be made according to the present disclosure. The containers can include fuel tanks, hydraulic tanks, water tanks, compressed gas tanks, thermocoolers, hydraulic oil tanks, diesel exhaust fluid tanks, and the like. In an embodiment, the containers can have a relatively small volume. For example, the containers can have a volume of less than about 10 gallons, such as less than about 5 gallons, such as less than about 4 gallons, such as less than about 2 gallons, and generally greater than about 0.1 gallons. Alternatively, larger tanks can be manufactured. For example, the tank may have a volume greater than about 10 gallons, such as greater than about 15 gallons, such as greater than about 20 gallons, and generally less than about 100 gallons, such as less than about 50 gallons, such as less than about 30 gallons. In one embodiment, fuel tanks for marine or boat applications may be constructed having volumes between about 15 gallons and about 35 gallons.

[0120]

[0112] Containers made according to the present disclosure can have excellent permeability properties combined with excellent impact resistance. The permeability of the container or container wall can be tested according to SAE test J2665 (latest edition 2021). SAE test J2665 tests the permeability of the material with test fuels including 10% ethanol, 45% toluene, and 45% isooctane. Steady state flux measurements are expressed in gmm / m 2 / day and is performed in accordance with SAE test J2665, section 10. Containers made in accordance with the present disclosure have a melting point of about 3.5 g mm / m at 40° C. 2 / day, e.g., about 3 g mm / m at 40°C 2 / day, e.g., about 2.8 g mm / m at 40°C 2 It can have a standard (relative to thickness) permeability of less than 1 / day.

[0121] The walls were also tested according to US EPA 40 CFR Part 1060.520 test method and had a hardness of approximately 1.1 g / m 2 / day, e.g., about 0.9 g / m 2 / day, e.g., about 0.7 g / m 2 / day (and generally about 0.01 g / m 2 / day). Moreover, even when made from a single layer of material, the walls can exhibit a stabilization parameter (r 2 The above results are obtained after a immersion period of 10 weeks and a test temperature of 28°C.

[0122] The polymer composition also has a viscosity of about 9 kJ / m 2 More than, for example, about 10 kJ / m 2 More than, for example, about 12 kJ / m 2 More than, for example, about 14 kJ / m 2 More than, for example, about 16 kJ / m 2 More than, for example, about 18 kJ / m 2 More than 50 kJ / m 2 The Charpy notched impact strength may be measured according to ISO test 179 using injection molded specimens.

[0123]

[0115] Containers made according to the present disclosure can also be tested for multiaxial impact strength according to the ARM low temperature impact test (V4) at 23°C (t=3mm). The multiaxial impact strength can be greater than about 5 ft-pounds force, such as greater than about 7.5 ft-pounds force, such as greater than about 9 ft-pounds force, such as greater than about 10 ft-pounds force, such as greater than about 12 ft-pounds force, such as greater than about 14 ft-pounds force, and generally less than about 30 ft-pounds force.

[0124] For example, articles made according to the present disclosure can generally have a relatively high density. In one embodiment, an article made from a powder composition of the present disclosure has a density of about 1.2 g / cm 3 More than, for example, about 1.25 g / cm 3 For example, about 1.3 g / cm 3 The density is generally about 2 g / cm. 3 Less than about 1.6 g / cm 3 is less than.

[0125]

[0117] The present disclosure will be better understood with reference to the following examples. EXAMPLES

[0126] Example 1

[0118] Various polymer formulations were formulated and powder compositions made from the formulations were tested for various properties to demonstrate that they are well suited for rotational molding applications.

[0127]

[0119] More specifically, the table below includes the formulated polymer compositions.

[0128] [Table 1]

[0129] [Table 2]

[0130] The above compositions were tested for various physical properties with the following results:

[0131] [Table 3-1]

[0132] [Table 3-2]

[0133] [Table 4-1]

[0134] [Table 4-2]

[0135] Example 2 The polymer formulation identified as sample number 2 in Example 1 above was used to manufacture a rotomolded container or tank. The molded tank had a nominal volume of 4.15 liters and an internal surface area of ​​0.103 m 2 and has a volume to surface area ratio of 40.29 l / m 2 The tank was made from a single layer of the polymer composition.

[0136] The tank was then tested for permeability and stabilization in accordance with US EPA 40 CFR Part 1060.520. The tank was tested with an immersion period of 10 weeks and a test temperature of 28°C. The tank had a permeability of only 0.6 g / m 2 This tank has a permeability of 1.5 g / m2 / day, which is the EPA requirement. 2 Unexpectedly, the tank also exhibited a stabilization parameter of 0.99, even though the tank was constructed from a single layer of material.

[0137] The tank was also tested for fuel permeability in accordance with California Air Resources Board test TP-901. The tank was found to have a permeability of only 1.132 g / m2 based on the internal surface area of ​​the fuel tank. 2 The transmittance per day is shown.

[0138]

[0124] The rotomolded tank also passed ABYC flammability and impact tests. The tank material was also tested for resistance to UV light according to SAE J1960 test procedure (2008). The material was subjected to continuous UV exposure using a Weatherometer in a manner equivalent to 5 years of exposure (DE<2). The material was subjected to 1250 kJ / m 2 The material passed the test.

[0139] Example 3

[0126] To demonstrate that the polymer compositions of the present disclosure can be varied to control mechanical properties in a desired manner, various polymer formulations were prepared and tested for various mechanical properties.

[0140] The following polymer compositions were prepared:

[0141] [Table 5]

[0142] The above formulations were tested for mechanical properties with the following results:

[0143] [Table 6]

[0144] As indicated above, varying the relative amounts of the components can affect the resulting properties. Example 4

[0130] Various polymer formulations were compounded and tested for various mechanical properties. More specifically, the table below includes the compounded polymer compositions.

[0145] [Table 7-1]

[0146] [Table 7-2]

[0147]

[0131] Samples Nos. 19, 20, and 21 were tested for various physical properties with the following results:

[0148] [Table 8]

[0149]

[0132] These and other modifications and variations to the present invention may be implemented by those skilled in the art without departing from the spirit and scope of the present invention as more particularly described by the appended claims. It should further be understood that aspects of the various embodiments may be interchanged in whole or in part. Moreover, those skilled in the art will appreciate that the foregoing description is illustrative only and is not intended to limit the invention as further described in such appended claims.

Claims

1. 1. A polymer composition for rotomolding applications comprising: polymer particles comprising a polyoxymethylene polymer blended with an impact modifier, said impact modifier comprising a thermoplastic elastomer, a methacrylate butadiene styrene, a styrene acrylonitrile, or a mixture thereof; said polyoxymethylene polymer having a melt flow rate of less than about 5 g / 10 min; said polyoxymethylene polymer being present in said polymer composition in an amount of at least about 55% by weight; and said one or more impact modifiers being present in said polymer composition in an amount of from about 4% to about 27% by weight.

2. 10. The polymer composition of claim 1, wherein the polymer particles have a particle size distribution such that at least about 10% by weight of the particles have a particle size greater than about 625 microns.

3. 3. The polymer composition of claim 1 or 2, wherein the polyoxymethylene polymer has a melt flow rate of less than about 4 g / 10 min, such as less than about 3 g / 10 min, and greater than about 0.5 g / 10 min.

4. 4. The polymer composition of any one of claims 1 to 3, wherein said impact modifier comprises a thermoplastic polyurethane elastomer alone or in combination with a thermoplastic copolyester elastomer.

5. 5. The polymer composition of claim 1, wherein the impact modifier comprises a thermoplastic copolyester elastomer.

6. 6. The polymer composition of claim 5, wherein the thermoplastic copolyester elastomer comprises a block copolymer of polybutylene terephthalate and polyether segments.

7. The polymer composition of claim 5 , wherein the thermoplastic copolyester elastomer comprises a thermoplastic ester ether elastomer.

8. 8. The polymer composition of claim 5, wherein the thermoplastic copolyester elastomer has a melting point within about 5° C. of the melting point of the polyoxymethylene polymer.

9. 9. The polymer composition according to any one of claims 1 to 8, wherein the polyoxymethylene polymer contains hydroxyl groups in an amount less than about 10 mmol / kg, such as less than about 8 mmol / kg, such as less than about 6 mmol / kg, such as less than about 4 mmol / kg, and is free of polyisocyanates.

10. 10. The polymer composition of claim 1, wherein the impact modifier comprises methacrylate butadiene styrene, styrene acrylonitrile, or a mixture thereof.

11. 1. A container for a fuel comprising a seamless rotationally molded housing forming an opening configured to receive a fluid, the housing comprising a walled interior enclosure, the wall being made from a polymer composition, the polymer composition comprising: a) a polyoxymethylene polymer having a melt flow rate of less than about 8 g / 10 min; and b) one or more impact modifiers present in said polymer composition in an amount of from about 4% to about 27% by weight. Including, The walls of the housing have a strength of 4 g mm / m at 40° C. according to SAE test J2665. ２ The container has a standard transmittance of less than 100 / day.

12. 12. The container of claim 11, wherein the polyoxymethylene polymer has a melt flow rate of less than about 4 g / 10 min, such as less than about 3 g / 10 min, and greater than about 0.5 g / 10 min.

13. 13. The container of claim 11 or 12, wherein the impact modifier comprises a thermoplastic polyurethane elastomer.

14. 13. The container of claim 11 or 12, wherein the impact modifier comprises a thermoplastic polyurethane elastomer in combination with a thermoplastic copolyester elastomer.

15. 15. The container of claim 11, 12 or 14, wherein the impact modifier comprises a block copolymer of polybutylene terephthalate and polyether segments.

16. 15. The container of claim 11, 12 or 14, wherein the impact modifier has a melting temperature, the melting temperature of the impact modifier being within about 5°C of the melting temperature of the polyoxymethylene polymer.

17. The wall of the container has a viscosity of about 3.5 g mm / m at 40° C. ２ 17. The container of claim 11, having a standard permeability of less than 100 / day.

18. 18. The container of any one of claims 11 to 17, wherein the container has a multiaxial impact strength of greater than about 7.5 ft-lbf at 23°C, such as greater than about 10 ft-lbf at 23°C, such as greater than about 15 ft-lbf at 23°C.

19. 19. The container according to any one of claims 11 to 18, wherein the wall has a thickness of from about 0.5 mm to about 10 mm.

20. 20. The container of any one of claims 11 to 19, wherein the polyoxymethylene polymer contains hydroxyl groups in an amount of less than about 10 mmol / kg, such as less than about 8 mmol / kg, such as less than about 6 mmol / kg, such as less than about 4 mmol / kg, and is free of polyisocyanates.

21. 12. The container of claim 11 comprising a fuel tank.

22. The walls of the housing have a strength of about 1 g / m2 when tested according to US EPA test 40 CFR Part 1060.

520. ２ / day, e.g., less than about 0.8 g / m ２ 12. The container of claim 11, having a permeability of less than 100 μg / day.

23. 23. The container according to claim 11 or 22, wherein the wall of the housing exhibits a stabilization parameter of greater than about 0.96, such as greater than about 0.97, such as greater than about 0.98, when tested according to US EPA test 40 CFR Part 1060.520 at 28°C for a 10 week immersion period.

24. 24. A container according to any one of claims 11 to 20 or 22 to 23 comprising a hydraulic oil tank, a compressed gas tank, a water tank, or a diesel exhaust liquid tank.

25. 12. The polymer composition according to claim 11, wherein the polymer composition does not contain a nitrogen-containing formaldehyde scavenger.

25. A container as described in any one of claims 24.

26. A container as described in any one of claims 11 to 25, wherein the wall of the housing is made from only a single layer of the polymer composition.

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