Rotationally molded parts for food contact applications

Abstract

Polymer compositions containing polyoxymethylene polymers in granular form for rotational molding applications are disclosed. The polyoxymethylene polymers are selected to have physical properties and are combined with one or more impact-resistant modifiers to produce hollow containers and other products having improved physical properties, such as impact strength. The polymer compositions of this disclosure are formulated to be particularly food-contact grade compliant.

Description

[Technical Field]

[0001] Related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 578,184, filed on 23 August 2023, which is incorporated by reference into this specification. [Background technology]

[0002]

[0002] Hollow containers can be manufactured using a variety of molding methods and techniques. One particular type of method is called rotational molding. During rotational molding, a polymer material is placed in a mold and heated above the softening temperature of the polymer material to melt and flow it. During the heating process, the mold is rotated around at least one axis, and typically around at least two different axes. Centrifugal force presses the polymer material against the walls of the mold, forming a hollow container. Rotational molding offers various advantages because its process is highly complex and can produce seamless hollow products. However, the range of processing available for polymer materials has limited the use of rotational molding to certain types of polymers, such as polyethylene polymers and polyamide polymers.

[0003]

[0003] In some applications, hollow containers formed by rotational molding include storage or containers designed to be in contact with and hold food. In these applications, the polymer compositions used to form the rotationally molded articles must meet all government regulations regarding food contact. As such, many polymers and many polymer compositions do not meet government regulations and therefore have not been used to manufacture food contact containers and other products. For example, most polyethylene polymer grades cannot be used to manufacture rotationally molded articles designed for food contact applications.

[0004]

[0004] Considering the above, most rotationally molded food contact products have been made from polypropylene polymer. However, rotationally molded products made from polypropylene polymer have various drawbacks and defects. For example, polypropylene polymer exhibits relatively insufficient impact strength and tends to show stress whitening and stress fracture during handling. Polypropylene polymer is also susceptible to staining, especially when in contact with various types of food. In addition to problems related to staining, polypropylene polymer also experiences odor retention problems. Furthermore, polypropylene polymer is somewhat difficult to rotationally mold and generates a significant amount of scrap waste during the manufacturing of the product.

[0005]

[0005] Considering the above, there is currently a need for food-contact grade polymers that can replace the use of conventionally used polypropylene polymers and other polymers in industry. One particular class of polymers with excellent strength, temperature resistance, and chemical resistance is polyoxymethylene polymers. However, polyoxymethylene polymers are typically blended with various other components that are not food-contact grade compliant, such as impact modifiers, formaldehyde scavengers, and light stabilizers. Therefore, there have been various obstacles to the possibility of incorporating polyoxymethylene polymers into food-contact grade resins designed for the manufacture of rotational molded articles.

[0006]

[0006] In consideration of the above, there is currently a need for a polyoxymethylene polymer composition that is sufficiently suitable for manufacturing rotational molded articles and complies with all food contact government regulations. In one embodiment, for example, there is a need for an impact-improved polyoxymethylene polymer resin and rotational molded articles made from the same resin, which not only complies with all food grade regulations but also includes at least one impact-improving agent that improves the impact resistance of products made from the resin. In addition, there is a need for a polyoxymethylene polymer composition that includes at least one colorant and is sufficiently suitable for manufacturing rotational molded articles that are fade-resistant. [Overview of the project] [Problems that the invention aims to solve]

[0007]

[0007] The disclosure generally relates to polyoxymethylene polymer compositions that are well suitable not only for rotational molding applications but especially for food contact applications. The polymer compositions of the disclosure can be formulated, for example, to produce a composition in which all components contained in the composition are approved for food contact use, while having good impact resistance and a low formaldehyde elution concentration.

[0008]

[0008] The disclosure also generally relates to fade-resistant polyoxymethylene polymer compositions containing at least one colorant. In one embodiment, the polyoxymethylene polymer composition may contain one or more colorants that are incorporated into the composition so as not to adversely affect the mechanical properties of the composition when formed into a rotational molded article. Fade-resistant polyoxymethylene polymer compositions are not only well-suited for use in food contact applications but also have broader applicability for manufacturing rotational molded articles in other fields. [Means for solving the problem]

[0009]

[0009] In one embodiment, the disclosure relates to a polyoxymethylene polymer composition. The polymer composition is particularly well suited for rotational molding applications and comprises polymer particles. The polymer particles comprise a polyoxymethylene polymer blended with an impact modifier. The impact modifier may, for example, be food grade approved and may meet the requirements of European Food Regulation 10 / 2011 and FDA Food Regulation FDA21CFR177.2470. The impact modifier may include any suitable thermoplastic elastomer. The polyoxymethylene polymer may have a melt flow rate of less than about 10 g / 10 min, for example less than about 5 g / 10 min, and may be present in the polymer composition in an amount of at least about 55% by weight. The impact modifier may be present in the polymer composition in an amount of about 4% to about 27% by weight. The polymer particles may further comprise a nucleating agent and / or an antioxidant. The polymer particles may have an average particle size of about 250 microns to about 800 microns.

[0010]

[0010] In one embodiment, the impact resistance modifier may be a thermoplastic polyurethane elastomer. The impact resistance modifier may include, for example, polyester polyurethane. The thermoplastic polyurethane elastomer may have a melt flow rate greater than about 7 g / 10 min, for example greater than about 8 g / 10 min, for example greater than about 9 g / 10 min, and a melt flow rate less than about 25 g / 10 min, for example less than about 20 g / 10 min, for example less than about 18 g / 10 min, for example less than about 15 g / 10 min, measured at 190°C and a load of 2.16 kg. Thermoplastic polyurethane elastomers, when tested at 190°C and a load of 8.7 kg in accordance with ISO Test 1131-1, may have melt flow rates greater than approximately 20 g / 10 min, for example greater than approximately 30 g / 10 min, for example greater than approximately 40 g / 10 min, for example greater than approximately 45 g / 10 min, and less than approximately 70 g / 10 min, for example less than approximately 60 g / 10 min, for example less than approximately 55 g / 10 min.

[0011]

[0011] Thermoplastic polyurethane elastomers can have a melting temperature of about 150°C to about 180°C. Thermoplastic polyurethane elastomers can exhibit a Shore A hardness greater than about 78, e.g., greater than about 80, e.g., greater than about 82, e.g., greater than about 84, and less than about 95, e.g., less than about 92, e.g., less than about 89, when measured in accordance with ASTM test D2240.

[0012]

[0012] In one embodiment, the impact resistance modifier may be a thermoplastic polyester elastomer. The impact resistance modifier may include, for example, a polyether ester. The thermoplastic polyester elastomer may have a melt flow rate of greater than about 7 g / 10 min, for example greater than about 8 g / 10 min, for example greater than about 9 g / 10 min, and less than about 25 g / 10 min, for example less than about 20 g / 10 min, for example less than about 18 g / 10 min, for example less than about 15 g / 10 min, measured at 190°C and a load of 2.16 kg. Thermoplastic polyester elastomers, when tested at 190°C and a load of 8.7 kg in accordance with ISO Test 1131-1, can have a melt flow rate greater than approximately 20 g / 10 min, for example greater than approximately 30 g / 10 min, for example greater than approximately 40 g / 10 min, for example greater than approximately 45 g / 10 min, and less than approximately 70 g / 10 min, for example less than approximately 60 g / 10 min, for example less than approximately 55 g / 10 min.

[0013]

[0013] Thermoplastic polyester elastomers can have a melting temperature of about 150°C to about 180°C. Thermoplastic polyester elastomers can exhibit a Shore A hardness greater than about 78, e.g., greater than about 80, e.g., greater than about 82, e.g., greater than about 84, and less than about 95, e.g., less than about 92, e.g., less than about 89, when measured in accordance with ASTM test D2240.

[0014]

[0014] As mentioned above, the polymer composition may contain a nucleating agent. In one embodiment, the nucleating agent may be a terpolymer. Alternatively, the nucleating agent may be a mineral nucleating agent, such as talc. In one aspect, the polymer composition does not contain any ultraviolet light stabilizers, and does not comprise a formaldehyde scavenger selected from guanamine, urea, or melamine.

[0015]

[0015] The polymer composition may contain an acid scavenger, such as a carboxylate. The carboxylate may comprise an alkaline earth metal salt of a carboxylic acid. For example, the acid scavenger may comprise calcium citrate, calcium propionate, or a mixture thereof. The acid scavenger may be present in the polymer composition in an amount of from about 0.001 wt% to about 1 wt%. In one specific aspect, the polymer composition contains calcium propionate and tricalcium citrate. Calcium propionate may be present in a weight ratio of from about 4:1 to about 1.2:1 relative to tricalcium citrate.

[0016]

[0016] In one aspect, the one or more acid scavengers may be present in the composition in a relatively small amount. For example, the one or more acid scavengers or calcium salts may be present in the polymer composition in an amount of less than about 0.1 wt%, for example less than about 0.08 wt%, for example less than about 0.06 wt%, and more than about 0.01 wt%.

[0017]

[0017] The polymer composition may also contain a relatively smaller amount of a plasticizer. For example, the plasticizer may comprise polyethylene glycol. The plasticizer may be present in an amount of from about 0.01 wt% to about 2 wt%, for example from about 0.1 wt% to about 0.8 wt%.

[0018]

[0018] In one aspect, the polymer composition may be free of plasticizers, and may also be free of any polyethylene glycol component. For example, in one application, the polymer composition may be formulated to be free of plasticizers to enhance one or more mechanical properties, such as impact strength.

[0019]

[0019] In another embodiment, the present disclosure is directed to a polymer composition for rotational molding applications. The polymer composition contains polymer particles comprising a polyoxymethylene polymer blended with an impact modifier. The impact modifier may comprise a thermoplastic elastomer. The polyoxymethylene polymer may have a melt flow rate of less than about 20 g / 10 min, such as less than about 15 g / 10 min, such as less than about 10 g / 10 min, such as less than about 5 g / 10 min. The impact modifier may be present in the polymer composition in an amount of from about 4% by weight to about 27% by weight. The polymer composition may be in the form of particles having an average particle diameter of from about 250 microns to about 800 microns. The polymer composition may further contain at least one colorant. The colorant may be incorporated into the polymer composition as a masterbatch containing the colorant in combination with a polymer. The polymer may, for example, comprise a polyoxymethylene polymer or a polyolefin polymer, such as a polyethylene polymer.

[0020]

[0020] The polymer composition may also optionally contain one or more ultraviolet stabilizers. According to the present disclosure, the polymer composition can, when tested at 500kJ / m 2 and in accordance with SAE test J2527, exhibit a color difference delta E of less than about 10, such as less than about 7, such as less than about 5, such as less than about 3, such as less than about 2.5, such as less than about 2, such as less than about 1.5.

[0021]

[0021] The polymer composition may further contain at least one colorant. The colorant may include a yellow colorant, a blue colorant, a red colorant, an orange colorant, a green colorant, a white colorant, a black colorant, or a mixture thereof. In one embodiment, the colorant includes carbon black or graphite in combination with a carrier polymer. The carrier polymer may be present in the masterbatch in an amount of about 1% to about 60% by weight. The colorant, for example carbon black, may be present in the polymer composition in an amount of less than about 2% by weight, for example less than about 1.5% by weight, for example less than about 1% by weight, for example less than about 0.5% by weight, while still exhibiting the above-mentioned fade resistance or low Delta E properties.

[0022]

[0022] In another embodiment, the disclosure relates to rotationally molded containers, for example, food contact products. Food contact products may include seamless rotationally molded food containers that define an internal space that comes into contact with food. Food containers may include walls made of the polymer composition described above. For example, food contact products may include food storage containers, beverage coolers, and the like. In other embodiments, rotationally molded articles made according to the disclosure may include any suitable tote or large-capacity tank for any suitable application. The walls may have a thickness of about 0.5 mm to about 10 mm. The container may have an internal capacity greater than approximately 11.4 L (3 gallons), for example greater than approximately 18.9 L (5 gallons), for example greater than approximately 37.9 L (10 gallons), for example greater than approximately 75.7 L (20 gallons), for example greater than approximately 151.4 L (40 gallons), for example greater than approximately 227.1 L (60 gallons), for example greater than approximately 378.5 L (100 gallons), and an internal capacity less than approximately 3028.3 L (800 gallons), for example less than approximately 1892.7 L (500 gallons), for example less than approximately 1514.2 L (400 gallons), for example less than approximately 1135.6 L (300 gallons), for example less than approximately 757.1 L (200 gallons).

[0023]

[0023] Rotational molded articles manufactured in accordance with this disclosure can exhibit excellent properties. For example, the polymer composition used to manufacture the rotational molded article or product is about 9 kJ / m 2 Larger than that, for example, about 10 kJ / m³ 2 Larger than that, for example, about 12 kJ / m³ 2 Larger than that, for example, about 14 kJ / m³ 2 Larger than that, and approximately 90 kJ / m³ 2 The polymer composition can exhibit a notched Charpy impact strength of less than 1 g / cc at 23°C in accordance with ISO Test 179. The polymer composition can exhibit a thermal deflection temperature of 0.45 MPa in accordance with ISO Test 75, above about 100°C, e.g., above about 110°C, e.g., above about 120°C, e.g., above about 130°C, and below about 160°C. The polymer composition can exhibit a tensile yield strength of greater than about 30 MPa, e.g., greater than about 35 MPa, e.g., greater than about 38 MPa, and below about 80 MPa, in accordance with ISO Test 527. The wall of the food container can have a density of greater than about 1 g / cc, e.g., greater than about 1.1 g / cc, e.g., greater than about 1.2 g / cc, e.g., greater than about 1.3 g / cc, and below about 1.6 g / cc, in accordance with ISO Test 1183. Polymer compositions used to form food contact products can exhibit melt flow rates greater than approximately 1 g / 10 min and less than approximately 10 g / 10 min, for example, melt flow rates of approximately 1 g / 10 min to approximately 6 g / 10 min, or for example, melt flow rates of approximately 2 g / 10 min to approximately 4.5 g / 10 min.

[0024]

[0024] Other features and aspects of the present disclosure are discussed in further detail below.

[0025] The complete and possible disclosure of this disclosure is provided in more detail in the remainder of the specification, including by reference to the accompanying drawings. [Brief explanation of the drawing]

[0025] [Figure 1] This is a perspective view of one embodiment of a rotationally molded product manufactured in accordance with this disclosure. [Figure 2] This is a perspective view of another embodiment of a rotationally molded product manufactured in accordance with this disclosure. [Modes for carrying out the invention]

[0026]

[0026] The repeated use of reference numerals in this specification and drawings is intended to represent the same or similar features or elements of the present invention.

[0027] Those skilled in the art will understand that the discussion of the present invention is merely a description of exemplary embodiments and does not limit the broader aspects of the present disclosure.

[0027]

[0028] In general, this disclosure covers polyoxymethylene polymer compositions in particulate form that are well-suited for use in rotational molding applications. According to this disclosure, polyoxymethylene polymer compositions can be formulated so that the composition meets all the requirements and government regulations necessary for polymer compositions used in food contact applications. Accordingly, this disclosure also covers rotational molded articles that are well-suited for holding and / or coming into contact with food.

[0028]

[0029] The polymer compositions of this disclosure are not limited to food applications. For example, in one embodiment, a polymer composition may be formulated to have excellent fade resistance while still retaining important mechanical properties such as impact resistance. A fade-resistant composition is not only well-suited for food contact applications but also suitable for virtually all other fields.

[0029]

[0030] Polymer compositions and rotational molded articles produced according to this disclosure offer various advantages and benefits compared, in particular, to polypropylene polymers used to date. For example, the polymer compositions can not only produce products with superior impact strength, but can also contain food-contact-compatible impact-resistant modifiers that can be incorporated into the polymer composition without experiencing phase separation during rotational molding applications. Thus, relatively large food containers or hollow containers can be produced from a single layer of the polymer composition, while having reduced rigidity and increased impact resistance. In addition, rotational molded articles produced according to this disclosure do not exhibit stress cracking, which is typically found in polypropylene polymers. Furthermore, the rotational molded articles are stain-resistant and do not experience odor-related problems. Moreover, the polymer compositions of this disclosure can withstand higher temperatures than many polymers used to date, which is particularly useful when cleaning and / or sterilizing products between uses.

[0030]

[0031] It has also become clear that the polymer compositions of this disclosure accept colorants, such as pigments and dyes. Therefore, rotationally molded polymer products capable of representing a wide variety of colors can be manufactured in accordance with this disclosure. Thus, color can be used to identify rotationally molded articles for specific applications and to distinguish them from other similar-looking products, which may be used to accommodate a variety of items or products. It has been found that the polymer compositions of this disclosure are well-suited to accepting a wide variety of colorants without sacrificing any mechanical properties.

[0031]

[0032] In one embodiment, for example, one or more colorants may be incorporated into a polymer composition to produce a colored molded article having improved fade resistance. These fade resistance properties can occur in almost any color, even black. For example, until now, it has been a significant problem to produce a black composition with fade resistance. However, according to this disclosure, fade resistance can be achieved even when using only a small amount of black colorant. For example, a polymer composition formulated according to this disclosure can have a colorant content of 500 kJ / m³.2 When tested in accordance with SAE test J2527, it is possible to exhibit a color difference delta E of less than approximately 10, e.g., less than approximately 9, e.g., less than approximately 8, e.g., less than approximately 7, e.g., less than approximately 6, e.g., less than approximately 5, e.g., less than approximately 4, e.g., less than approximately 3, e.g., less than approximately 2.5, e.g., less than approximately 2, e.g., less than approximately 1.5.

[0032]

[0033] In addition to the above, the use of polyoxymethylene polymers for rotational molding methods can yield various benefits and advantages. Polyoxymethylene copolymers possess a linear structure of high crystalline quality, resulting in a variety of characteristics, including, for example, remarkable abrasion resistance, long-term fatigue resistance, toughness resistance, and creep resistance, as well as excellent resistance to moisture, solvents, and strong alkalis. The chemical structure of polyoxymethylene polymers provides greater stability against thermal and oxidative degradation compared to many other polymers. In fact, the use of polyoxymethylene copolymers is more thermally stable and more resistant to degradation than that of polyoxymethylene homopolymers. Polyoxymethylene polymers are formulated to increase impact resistance while maintaining excellent permeability.

[0033]

[0034] As described above, the polymer compositions of this disclosure are in powder form. The powder compositions have a controlled particle size distribution, which has been found to provide advantages and benefits during rotational molding. For example, the powder may have fluid flow properties. Thus, the polymer composition can be easier to handle for filling into a mold and will circulate uniformly within the mold during rotation. The particle size distribution may result in, for example, better accuracy and tolerance in product formation.

[0034]

[0035] The particle size distribution in combination with various components that make up the polymer composition can also produce a polymer composition having less shrinkage and lower internal stress during the molding process. The particle size distribution in combination with the formulation also provides a relatively large operating range during the molding process. For example, the polymer composition has thermal properties that make the composition well suited for longer cycle times and better stability. Thus, when melted, the polymer composition flows uniformly across the surface of the mold to produce a molded article with substantially no or no voids at all.

[0035]

[0036] In one aspect, the powder composition generally has an average particle size D that is larger than 250 microns, for example larger than about 300 microns, for example larger than about 350 microns, for example larger than about 400 microns. 50 The particle size is generally less than about 800 microns, for example less than about 750 microns, for example less than about 700 microns, for example about 650 microns. 50

[0036]

[0037] The particle size can be determined using a laser scattering particle size distribution analyzer, for example a Beckman Coulter LS13 320 particle size analyzer.

[0038] In another embodiment, the particle size distribution of the polymer composition can be such that 90% of the particles have a size less than about 800 microns, for example less than about 750 microns. 50% by mass of the particles can have a particle size from about 250 microns to about 600 microns. In addition to using light scattering to determine particle size, in other embodiments, a sieve test can be used. For example, the particle size (on a mass basis) can be determined using a RO-TAP sieve shaker.

[0037]

[0039] ​As described above, the polymer compositions of this disclosure may be formulated such that each raw material or component contained in the composition is food contact grade compliant. In this regard, a food contact grade compliant polyoxymethylene polymer may be combined with a food contact grade compliant impact modifier, which may include an elastomer. The impact modifier is selected to have a variety of properties such as being not only food contact grade compliant, but also sufficiently suitable for blending with the polyoxymethylene polymer and for use in rotational molding methods. The polymer compositions of this disclosure may also contain a nucleating agent. The nucleating agent can increase the degree of crystallinity, stiffness, and thermal deflection temperature. By increasing the degree of crystallinity, the polymer composition is better suited to grinding methods to produce particles of a uniform size as well as a desired size.

[0038]

[0040] In addition to containing the above components, polymer compositions may also be formulated to avoid the use of certain raw materials and components. For example, polymer compositions may be formulated without conventional formaldehyde scavengers, such as guanamine, urea, melamine, and their derivatives. Polymer compositions may also be formulated without various light stabilizers, particularly UV stabilizers. However, in another embodiment, polymer compositions may be formulated to contain UV stabilizers. One or more UV stabilizers may be incorporated into the polymer composition in an amount of less than about 2% by weight, for example less than about 1.5% by weight, for example less than about 1% by weight, for example less than about 0.8% by weight, and more than about 0.01% by weight. Adding one or more UV stabilizers may be one factor in controlling fade resistance, for example. The way in which components are added together and the components present may also significantly contribute to fade resistance properties.

[0039]

[0041] The polymer compositions of this disclosure may be formulated to comply with all kinds of food contact government regulations. For example, the polymer compositions may be formulated to be food contact compliant under U.S. and / or European law.

[0040]

[0042] Title 21 CFR generally deals with food and pharmaceuticals. In particular, 21 CFR §177.2470 and §177.2480 deal with POM copolymers and POM homopolymers, respectively. Suitable adjuvants, such as stabilizers or pigments, may be added. POM polymers should have a food contact area of ​​0.0775 mg / cm³. 2 (0.5 mg / in 2 The net chloroform-soluble eluate must not exceed 121°C (250°F), and its use is restricted to temperatures not exceeding 121°C (250°F). The eluate is prepared according to the simulated use scenario set forth in 21 CFR §175.300(d), and repeated below:

[0041] [Table 1]

[0042] [Table 2]

[0043]

[0043] 21 CFR §177.2470 and §177.2480 further detail the requirements for POM polymers. When POM polymers are ground or cut into particles that pass through USA Standard Sieve No. 6 and are held in USA Standard Sieve No. 10, with or without any adjuvants, the total elute should not exceed (i) 0.2% by weight when eluted in distilled water at reflux temperature for 6 hours, and (ii) 0.15% by weight when eluted in n-heptane at reflux temperature for 6 hours. POM homopolymers should not produce more than 0.005% by weight of formaldehyde. Furthermore, POM homopolymers should contain no more than 1.9% by weight of stabilizers. The minimum number average molecular weight of the copolymer is 25,000 and the density is 1.39 g / cm³. 3 ~1.44 g / cm³ 3It has a melting point of 172°C to 184°C. The approved POM copolymer may be a reaction product of trioxane and either ethylene oxide or butanediol formal up to 5% by weight. The minimum number average molecular weight of the copolymer is 15,000. The approved copolymer should contain stabilizers at a concentration of 2.0% by weight or less, with the amount of any single stabilizer not exceeding 1.0% by weight.

[0044]

[0044] European regulations for food contact standards of polymers are found in EC10 / 2011. Similar to 21 CFR, the regulations enumerate numerous simulated scenarios and simulated materials to provide test conditions that mimic realistic worst-case scenarios of the intended use of the material. For example, Tables 1 and 2 of Annex V detail the contact times and contact temperatures of the test scenarios using the simulated eluents listed in Table 1 of Annex III.

[0045]

[0045] EC10 / 2011 also lists the total migration limits for various metals per unit mass of food or food substitute: barium 1 ppm; cobalt 0.05 ppm; copper 5 ppm; iron 48 ppm; lithium 0.6 ppm; manganese 0.6 ppm; and zinc 25 ppm. Primary aromatic amines not listed in Table 1 of Annex I shall not be released in detectable amounts (less than 0.01 ppm).

[0046]

[0046] Various EU publications have further set restrictions on additives, such as colorants (coloring additives). For example, EC10 / 2011 limits the amount of carbon black to 2.5% by weight or less, benzo(a)pyrene to 0.25 ppm or less, and the toluene elution fraction not exceeding 0.1% by weight. As described in more detail below, carbon black can be incorporated into the polymer compositions of the present disclosure in relatively small amounts, for example less than about 1% by weight, for example less than about 0.8% by weight, while still producing a vivid black product that does not fade much or at all after exposure to UV light.

[0047]

[0047] For example, AP(89)1 specifies that the metals and metalloids in the colorant may be soluble in 0.1 M HCl in amounts not exceeding: antimony 0.05 wt%; arsenic 0.01 wt%; barium 0.01 wt%; cadmium 0.01 wt%; chromium 0.1 wt%; lead 0.01 wt%; mercury 0.005 wt%; and selenium 0.01 wt%. Primary aromatic amines in the colorant, soluble in 1 M HCl and expressed as aniline, should be present in amounts not exceeding 500 ppm. Carbon black, in particular, should not contain more than 0.15 wt% toluene eluting fraction. Leachable polychlorinated biphenyls should not exceed 25 ppm.

[0048]

[0048] German BfR IX sets the same metal purity limits as AP(89)1 and further requires that the colorants must withstand temperatures in the range of approximately 150°C to approximately 300°C while the plastics are being processed.

[0049]

[0049] Spanish Royal Decree 847 / 2011 sets the same metal purity limits as AP(89)1, except that it specifies 0.1N HCl.

[0050]

[0050] Italian Ministerial Decree 21 / 3 / 73 sets forth the same metal purity restrictions as AP(89)1, except that it specifies 0.1N HCl and further restricts arsenic to 0.005% by weight or less.

[0051]

[0051] In some embodiments, the polymer composition is formulated to conform to at least one of the above certifications by paying close attention to process parameters and the selection of compositional raw materials. For example, the preparation of the polyoxymethylene polymer and the selection of any additives (e.g., coloring additives) may be specifically and skillfully carried out to produce a final product (e.g., material, equipment component, or finished equipment) that conforms to at least one of the above standards.

[0052]

[0052] In one embodiment as described above, the main raw material or matrix polymer contained in the polymer composition is a polyoxymethylene polymer. The preparation of the polyoxymethylene polymer can be carried out by polymerization of a polyoxymethylene-forming monomer, such as trioxane or a mixture of trioxane and a cyclic acetal such as dioxolane, in the presence of a molecular weight modifier, such as glycol. According to one embodiment, the polyoxymethylene is a homopolymer or copolymer containing at least 50 mol%, for example at least 75 mol%, for example at least 90 mol%, and for example further at least 97 mol% of -CH2O- repeating units.

[0053]

[0053] In one embodiment, a polyoxymethylene copolymer is used. The copolymer may contain about 0.1 mol% to about 20 mol%, particularly about 0.5 mol% to about 10 mol%, of repeating units having at least two carbon atoms, which include saturated or ethylenically unsaturated alkylene groups or cycloalkylene groups, and may contain one or more substituents selected from the group consisting of alkylcycloalkyl, aryl, aralkyl, heteroaryl, halogen, or alkoxy, which have a sulfur atom or an oxygen atom in the molecular chain. In one embodiment, a cyclic ether or cyclic acetal is used, which can be introduced into the copolymer by a ring-opening reaction.

[0054]

[0054] Preferred cyclic ethers or cyclic acetals are those of the following formula:

[0055] [ka]

[0056] In the formula, x is either 0 or 1, and R 2The C2-C4 alkylene group having one or more substituents, which are, as appropriate, a C1-C4 alkyl group or a C1-C4 alkoxy group and / or a halogen atom, preferably a chlorine atom. Just as examples, cyclic ethers such as ethylene oxide, propylene 1,2-oxide, butylene 1,2-oxide, butylene 1,3-oxide, 1,3-dioxane, 1,3-dioxolane, and 1,3-dioxepane may be used, as well as linear oligoformals or polyformals, such as polydioxolane or polydioxepane, also as comonomers. It is particularly advantageous to use copolymers composed of 99.5-95 mol% trioxane and 0.5-5 mol%, for example 0.5-4 mol%, of one of the aforementioned comonomers.

[0057]

[0055] In a particular aspect of the present disclosure, the polyoxymethylene copolymer incorporated into the powder composition contains a relatively small amount of comonomer. For example, the polyoxymethylene copolymer may contain a comonomer such as dioxolane in an amount of less than about 5% by weight, for example less than about 2% by weight, for example less than about 1.5% by weight, for example less than about 1% by weight, for example less than about 0.75% by weight, for example less than about 0.7% by weight. The comonomer content is generally higher than about 0.3% by weight, for example higher than about 0.5% by weight.

[0058]

[0056] Polymerization may be carried out as precipitation polymerization or in a solution. The molecular weight of the resulting polymer, and therefore the MVR value, can be adjusted by a suitable selection of polymerization parameters, such as polymerization time or the amount of molecular weight modifier.

[0059]

[0057] Polyoxymethylene polymers incorporated into polymer compositions can have a variety of end groups or end groups and other components contained in the composition depending on the specific application. In one embodiment, polyoxymethylene polymers are relatively thermally stable. For example, polyoxymethylene polymers 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 0.6 mol%.

[0060]

[0058] The amount of hydroxyl terminal groups in the polyoxymethylene polymer may depend on whether a polyisocyanate coupling agent is present in the composition. If a polyisocyanate coupling agent is not present, 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 4 mmol / kg.

[0061]

[0059] Alternatively, the polyoxymethylene polymer may contain a larger amount of terminal hydroxyl groups. In one embodiment, the polyoxymethylene polymer has a terminal hydroxyl group content of at least 15 mmol / kg, for example, at least 18 mmol / kg, for example, at least 20 mmol / kg, for example, more than about 25 mmol / kg, for example, more than about 30 mmol / kg, for example, more than about 40 mmol / kg, for example, more than about 50 mmol / kg. The terminal hydroxyl content is generally less than about 300 mmol / kg, for example, less than about 200 mmol / kg, for example, 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 quantification of the hydroxyl group content in the polyoxymethylene polymer can be performed by the method described in Japanese Patent Application Publication No. 2001-11143.

[0062]

[0060] In addition to terminal hydroxyl groups, polyoxymethylene polymers may also have other terminal groups commonly found in these polymers. Examples of these are alkoxy groups, formic groups, acetate groups, or aldehyde groups. In one embodiment, the polyoxymethylene polymer may also contain terminal NH2 groups. According to one embodiment, the polyoxymethylene is a copolymer containing at least 50 mol%, for example at least 75 mol%, for example at least 90 mol%, and for example further at least 95 mol% of -CH2O- repeating units.

[0063]

[0061] The polyoxymethylene polymer can have any preferred molecular weight. The molecular weight of the polymer may be, for example, about 4,000 g / mol to about 100,000 g / mol. The polyoxymethylene polymer can have a molecular weight that is, for example, higher than about 10,000 g / mol, for example higher than about 15,000 g / mol, for example higher than about 20,000 g / mol, for example higher than about 30,000 g / mol, for example higher than about 40,000 g / mol, and generally less than about 90,000 g / mol.

[0064]

[0062] Polyoxymethylene polymers present in a composition can generally have a melt flow index (MFI) in the range of about 0.1 g / 10 min to about 200 g / 10 min. The melt flow is determined in accordance with ISO 1133 at 190°C and 2.16 kg. However, in one embodiment, polyoxymethylene polymers have 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 range when used in rotational molding methods. In addition, a lower melt flow rate can result in better physical properties. For example, polyoxymethylene polymers can have a melt flow rate of less than about 8 g / 10 min, e.g., less than about 5 g / 10 min, e.g., less than about 4 g / 10 min, e.g., less than about 3 g / 10 min, e.g., less than about 2 g / 10 min, e.g., less than about 1 g / 10 min, and generally greater than about 0.5 g / 10 min.

[0065]

[0063] The polyoxymethylene polymer may be present in the polyoxymethylene polymer composition in an amount of at least 40% by weight, for example, at least 45% by weight, for example, at least 55% by weight, for example, at least 60% by weight, for example, at least 70% by weight, for example, at least 80% by weight. The polyoxymethylene polymer may be present in an amount of less than about 96% by weight, for example, less than about 85% by weight, for example, less than about 80% by weight, for example, less than about 75% by weight.

[0066]

[0064] According to the present disclosure, a polyoxymethylene polymer is combined with one or more impact modifiers. More specifically, an impact modifier that is food contact grade compliant is selected for use in the polymer composition. In one embodiment, the impact modifier may include any suitable elastomer. The elastomer may include, for example, a thermoplastic polyurethane elastomer, a thermoplastic polyester elastomer, or a combination thereof. In one embodiment, the polymer composition does not include impact modifiers including other impact modifiers, such as methacrylate butadiene styrene, styrene acrylonitrile, and mixtures thereof.

[0067]

[0065] In one embodiment, the impact resistance modifier is a combination of a thermoplastic polyurethane elastomer and a thermoplastic polyester elastomer. The two elastomers can be present in any suitable weight ratio. For example, the thermoplastic polyurethane elastomer and the thermoplastic polyester elastomer can be present in a weight ratio of 1:10 to 10:1, for example, a weight ratio of 1:10 to 2:1, for example, a weight ratio of 1:8 to 3:1.

[0068]

[0066] As described above, in one embodiment, the impact resistance modifier includes a food-contact approved thermoplastic polyurethane elastomer having specific properties. The thermoplastic polyurethane elastomer may have, for example, 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 polyester species prepared by reacting a long-chain diol with a diisocyanate to produce a polyurethane prepolymer having isocyanate end groups, followed by chain extension of the prepolymer using a diol chain extender. Typical long-chain diols are polyester diols, e.g., poly(butylene adipate)diol, poly(ethylene adipate)diol, and poly(ε-caprolactone)diol; and polyether diols, e.g., poly(tetramethylene ether)glycol, poly(propylene oxide)glycol, and poly(ethylene oxide)glycol. Suitable diisocyanates include 4,4'-methylenebis(phenyl isocyanate), 2,4-toluene diisocyanate, 1,6-hexamethylene diisocyanate, and 4,4'-methylenebis-(cycloxyl isocyanate). Suitable chain extenders are C2-C6 aliphatic diols (dials), such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol (hexanedial), and neopentyl glycol. An example of a thermoplastic polyurethane is essentially characterized as poly(adipic acid-co-butylene glycol-co-diphenylmethane diisocyanate).

[0069]

[0067] In one embodiment, the impact modifier comprises a food-contact approved thermoplastic polyester elastomer having specific properties. The impact modifier may be, for example, a thermoplastic copolyester elastomer comprising a thermoplastic ester ether elastomer. In one embodiment, the thermoplastic polyester elastomer may be a thermoplastic copolyester elastomer comprising a block copolymer of polybutylene terephthalate segments and polyether segments.

[0070]

[0068] In one embodiment, impact modifiers having a specific hardness and melt flow rate contained in the polymer composition of the present disclosure include thermoplastic polyurethane elastomers, thermoplastic polyester elastomers, or combinations thereof. For example, an impact modifier may have a Shore A hardness greater than about 78, e.g., greater than about 80, e.g., greater than about 82, e.g., greater than about 84. The Shore A hardness of an impact modifier may be less than about 95, e.g., less than about 92, e.g., less than about 89, e.g., less than about 88, when measured in accordance with ASTM test D2240. Impact modifiers or thermoplastic polyurethane elastomers can exhibit melt flow rates greater than approximately 7 g / 10 min at 190°C and a load of 2.16 kg, e.g., greater than approximately 8 g / 10 min, e.g., greater than approximately 9 g / 10 min, e.g., greater than approximately 10 g / 10 min, e.g., greater than approximately 11 g / 10 min, e.g., greater than approximately 12 g / 10 min, e.g., greater than approximately 13 g / 10 min, e.g., greater than approximately 14 g / 10 min, e.g., greater than approximately 15 g / 10 min. The melt flow rate is generally less than approximately 25 g / 10 min, e.g., less than approximately 23 g / 10 min, e.g., less than approximately 20 g / 10 min, e.g., less than approximately 18 g / 10 min, e.g., less than approximately 15 g / 10 min.

[0071]

[0069] In one embodiment, the polyoxymethylene polymer is combined with an impact modifier having a melting temperature equivalent to that of the polyoxymethylene polymer, such as a thermoplastic polyurethane elastomer, a thermoplastic polyester elastomer, or a combination thereof. For example, in one embodiment, the impact modifier is selected such that the melting temperature of the impact modifier is within a range of about 8°C, for example, within a range of about 5°C, for example, within a range of about 4°C, or for example, within a range of about 3°C, of ​​the melting temperature of the polyoxymethylene polymer. For example, the impact modifier, such as a polyurethane elastomer, a thermoplastic polyester elastomer, or a combination thereof, may be selected considering a melting temperature of about 150°C to about 185°C, for example, a melting temperature of about 158°C to about 172°C, or for example, a melting temperature of about 163°C to about 169°C. The melting temperature can be determined in accordance with ISO test 11357-1 / -3 (10°C / min) or ASTM test D3417 (DSC).

[0072]

[0070] In one embodiment, an impact modifier having a melting temperature below the melting temperature of the polyoxymethylene polymer, such as a thermoplastic polyurethane elastomer, a thermoplastic polyester elastomer, or a combination thereof may be selected. For example, the melting temperature of the impact modifier may be less than about 166°C.

[0073]

[0071] Generally, one or more impact modifiers can be present in the polymer composition in amounts of about 2% to about 45% by weight, for example, about 4% to about 27% by weight, including all values ​​in 1% by weight increments between them. For example, one or more impact modifiers can be present in the polymer composition in amounts of more than about 6% by weight, for example, more than about 8% by weight, for example, more than about 10% by weight, for example, more than about 12% by weight, for example, more than about 14% by weight, for example, more than about 16% by weight, for example, more than about 20% by weight, for example, more than about 25% by weight, for example, more than about 30% by weight, for example, more than about 35% by weight, and generally in amounts of less than about 50% by weight, for example, less than about 40% by weight, for example, less than about 25% by weight, for example, less than about 23% by weight.

[0074]

[0072] In addition to the polyoxymethylene polymer and one or more impact-resistant modifiers, the polymer compositions of the present disclosure may contain a variety of other components. For example, in one embodiment, plasticizers such as polyalkylene glycol may be incorporated into the polymer composition, providing a variety of advantages and benefits. Polyalkylene glycol can, for example, improve the flow properties of particles and / or improve impact strength.

[0075]

[0073] Polyalkylene glycols that are particularly suitable for use in polymer compositions include polyethylene glycol, polypropylene glycol, and mixtures thereof.

[0076]

[0074] The molecular weight of polyalkylene glycol can vary depending on various factors such as the characteristics of the polyoxymethylene polymer and the process conditions for manufacturing the molded article. In one embodiment, polyalkylene glycol, for example polyethylene glycol, can have a relatively low molecular weight. For example, the molecular weight may be less than about 10,000 g / mol, for example less than about 8,000 g / mol, for example less than about 6,000 g / mol, for example less than about 4,000 g / mol, and may generally be higher than about 1,000 g / mol, for example higher than about 2,000 g / mol. In one embodiment, a polyethylene glycol plasticizer having a molecular weight of about 2,000 g / mol to about 5,000 g / mol is incorporated into the polymer composition.

[0077]

[0075] When present in the polymer composition, polyalkylene glycol may be added in an amount greater than about 0.1% by weight, for example, greater than about 0.3% by weight. Generally, polyalkylene glycol can be present in the polymer composition in an amount less than about 5% by weight, for example, less than about 3% by weight, for example, less than about 1% by weight.

[0078]

[0076] Although plasticizers such as polyethylene glycol can offer various advantages in some applications, polymer compositions can be formulated to be free of plasticizers in other applications. For example, a polymer composition can be formulated to be free of polyethylene glycol. Formulating a composition without plasticizers such as polyethylene glycol can improve the mechanical properties of the composition, particularly its impact strength.

[0079]

[0077] In one embodiment, the polymer composition may contain an acid scavenger. The acid scavenger may include a carboxylate salt. For example, the carboxylate salt may include a salt of a fatty acid, such as a metal salt of a fatty acid. For example, the carboxylate salt may include an alkaline earth metal salt of a fatty acid. The cation of the salt may include, for example, calcium, barium, lithium, sodium, magnesium, zinc, and the like.

[0080]

[0078] Fatty acids generally may contain carbon chains of about 3 to about 20 carbon atoms. Fatty acids may also contain dicarboxylic acids or tricarboxylic acids.

[0079] In one embodiment, the metal salt of the fatty acid may include metal salts of citric acid, propionic acid, stearic acid, butanoic acid, hexanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, etc. In a particular embodiment, the metal salt of the fatty acid may include calcium propionate, calcium 12-hydroxystearate, calcium citrate, for example, tricalcium citrate, and mixtures thereof. In one embodiment, if the polyoxymethylene polymer composition contains one or more colorants, various benefits and advantages can be obtained by combining the colorants with calcium propionate.

[0081]

[0080] One or more carboxylates are generally present in the polymer composition in an amount greater than about 0.001% by weight, for example, greater than about 0.01% by weight, for example, greater than about 0.08% by weight, for example, greater than about 0.1% by weight, for example, greater than about 0.12% by weight, for example, greater than about 0.14% by weight. One or more carboxylates are generally present in the polymer composition in an amount less than about 5% by weight, for example, less than about 3% by weight, for example, less than about 2% by weight, for example, less than about 1.5% by weight, for example, less than about 1% by weight.

[0082]

[0081] In one embodiment, the polymer composition contains at least two acid scavengers. For example, the polymer composition may contain a combination of calcium citrate, such as tricalcium citrate, and calcium propionate. The calcium citrate may be present in a weight ratio of about 1:1 to about 1:5, for example, about 1:1.5 to about 1:3, relative to calcium propionate. For example, in a particular embodiment, the polymer composition may contain tricalcium citrate in an amount of about 0.01% to about 0.08% by weight, and anhydrous calcium propionate in an amount of about 0.7% to about 1.3% by weight.

[0083]

[0082] In one embodiment, the amount of acid scavenger contained in the polymer composition can be minimized. For example, the polymer composition may contain one or more acid scavengers or calcium salts in an amount of less than about 0.1% by weight, for example less than about 0.08% by weight, for example less than about 0.06% by weight, and more than about 0.01% by weight.

[0084]

[0083] In one embodiment, a nucleating agent may be present. The nucleating agent can increase the degree of crystallinity and may include an oxymethylene terpolymer. In a particular embodiment, for example, the nucleating agent may include a terpolymer of butanediol diglycidyl ether, ethylene oxide, and trioxane. Alternatively, the nucleating agent may include a mineral nucleating agent, such as talc particles. The nucleating agent may be present in the composition in an amount of at least about 0.01% by weight, for example, at least about 0.05% by weight, for example, at least about 0.1% by weight, and less than about 2% by weight, for example, less than about 1.5% by weight, for example, less than 1% by weight, the weight being based on the total weight of each polymer composition.

[0085]

[0084] Many conventional polymer compositions containing polyoxymethylene polymers have contained formaldehyde scavengers. Conventional formaldehyde scavengers were typically nitrogen-containing compounds. These were mainly heterocyclic compounds having at least one nitrogen atom as a heteroatom adjacent to an amino-substituted carbon atom or carbonyl group, such as pyridine, pyrimidine, pyrazine, pyrrolidone, aminopyridine, and compounds derived therefrom. Compounds of this nature are aminopyridine and compounds derived therefrom.

[0086]

[0085] Specific examples of formaldehyde scavengers used to date include guanamine, urea, melamine, and their derivatives. However, according to the present disclosure, polymer compositions may be formulated to contain none of the above formaldehyde scavengers, or to contain one or more of the above formaldehyde scavengers in relatively low concentrations. For example, nitrogen-containing formaldehyde scavengers, such as urea, melamine, or guanamine, may be present in the composition in an amount of less than about 0.5% by weight, for example, less than about 0.4% by weight. However, in one embodiment, the polymer composition is formulated to be free of urea, melamine, and / or guanamine.

[0087]

[0086] In one embodiment, for example, the formaldehyde scavenger may include polyamides, particularly copolyamides. Such scavengers do not contain melamine. The copolyamide may be present in relatively small amounts, for example, less than about 1% by weight, for example less than about 0.5% by weight, for example less than about 0.3% by weight, for example less than about 0.1% by weight, and more than about 0.0001% by weight, for example more than about 0.01% by weight.

[0088]

[0087] Another additive that may be present in the composition is a sterically hindered phenol compound, which may act as an antioxidant. Examples of commercially available compounds of this type include pentaerythrityltetrakis[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® MD1024, BASF), hexamethylene glycol bis[3-(3,5-di-cert-butyl-4-hydroxyphenyl)propionate] (IRGANOX® 259, BASF), and 3,5-di-tert-butyl-4-hydroxytoluene (LOWINOX® BHT, Chemtura). The above compounds can be present in the polymer composition in an amount ranging from about 0.01% to about 1% by weight, based on the total weight of the polymer composition. In one embodiment, one or more hindered phenol antioxidants can be present in the polymer composition in an amount greater than about 0.2% by weight, for example, greater than about 0.24% by weight, for example, greater than about 0.28% by weight.

[0089]

[0088] 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. An example of a fatty acid amide is ethylenebis(stearic acid amide). Alternatively, the lubricant may include polyethylene wax. The lubricant may generally be present in the polymer composition in an amount of about 0.01% to about 1% by weight.

[0090]

[0089] In addition to limiting the amount of a specific formaldehyde scavenger, the polymer compositions of the present disclosure may also be formulated to be free of various other components. For example, in one embodiment, the composition may be free of any coupling agent, and in particular free of isocyanate coupling agents. In addition, the composition may be formulated to be free of UV stabilizers. In this regard, the composition may be formulated to be free of benzophenone, benzotriazole, or benzoate. In one embodiment, the composition may also be formulated to be free of sterically hindered amine light stabilizers. For example, the composition may be formulated to be free of sebacate.

[0091]

[0090] Alternatively, the composition may contain one or more UV stabilizers. UV stabilizers can be incorporated into the composition, for example, while still being suitable for food contact applications. UV stabilizers may include benzophenone, benzotriazole, or benzoate. UV stabilizers may be selected from the group consisting of 2-hydroxyphenylbenzotriazole or its derivatives, hydroxybenzophenone or its derivatives, and 2-hydroxyphenyltriazine and its derivatives. A particularly preferred UV stabilizer is 2-[2-hydroxy-3,5-di-(1,1-dimethylbenzyl)]-2H-benzotriazole. UV light absorbers, if present, may be present in the polymer composition in an amount of at least about 0.01% by weight, for example, at least about 0.05% by weight, for example, at least about 0.075% by weight, and less than about 1% by weight, for example, less than about 0.75% by weight, for example, less than about 0.5% by weight, where the weight is based on the total weight of each polymer composition.

[0092]

[0091] Light stabilizers may also include hindered amine light stabilizers. Examples of hindered amine light stabilizers include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][2,2,6,6-tetramethyl-4-piperidyl]imino]hexamethylene[2,2,6,6-tetramethyl-4-piperidyl]imino], methyl 1,2,2,6,6-pentamethyl-4-piperidinyl sebacate, and bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate. One or more hindered light stabilizers may be present in the polymer composition in an amount of at least about 0.01% by weight, for example, at least about 0.05% by weight, for example, at least about 0.075% by weight, and less than about 1% by weight, for example, less than about 0.75% by weight, for example, less than about 0.5% by weight, the weight being based on the total weight of each polymer composition.

[0093]

[0092] In one embodiment, one or more colorants may also be added to the polymer composition. The colorants may be pigments or dyes. In one embodiment, the colorants may be added as a masterbatch in combination with a carrier polymer. Various types of carrier polymers may be used. In one embodiment, for example, the carrier polymer may be a polyolefin polymer, such as a polyethylene polymer. The polyethylene polymer may be, for example, linear low-density polyethylene. Alternatively, the carrier polymer may be a polyoxymethylene polymer. One or more colorants may 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. For example, one or more colorants may be present in the polymer composition in an amount of less than about 1.5% by weight, for example less than about 1% by weight, for example less than about 0.8% by weight, for example less than about 0.6% by weight and greater than about 0.1% by weight.

[0094]

[0093] When adding a colorant, the use of a masterbatch in combination with a carrier polymer may be preferred in various applications. The carrier polymer may help disperse the colorant, for example, to improve the mechanical properties of the polymer composition and to promote fade resistance. The carrier polymer may be present in weight ratios of about 0.5:1 to about 100:1 relative to the colorant, for example, in weight ratios of about 1:1 to about 50:1.

[0095]

[0094] In one embodiment, a masterbatch containing a colorant may be incorporated into a polymer composition in an amount greater than about 1% by weight, for example, greater than about 2% by weight, for example, greater than about 4% by weight, for example, greater than about 8% by weight, for example, greater than about 10% by weight, for example, greater than about 15% by weight, and less than about 25% by weight, for example, less than about 20% by weight, for example, less than about 15% by weight. The colorant may be contained in the masterbatch in an amount of about 1% to about 50% by weight, for example, about 2% to about 30% by weight, for example, about 3% to about 25% by weight. For example, the carrier polymer may be present in the masterbatch in an amount greater than approximately 50% by weight, for example, greater than approximately 60% by weight, for example, greater than approximately 70% by weight, for example, greater than approximately 80% by weight, for example, greater than approximately 90% by weight, for example, greater than approximately 94% by weight, for example, greater than approximately 96% by weight, and less than approximately 99.9% by weight, for example, less than approximately 90% by weight, for example, less than approximately 70% by weight.

[0096]

[0095] In one embodiment, the colorants incorporated into the composition are selected to be food contact grade compliant. Examples of colorants that may be incorporated into the composition include, but are not limited to, Shikotan Yellow K2112, Chronos 2220, Chronos 2211, Chronos 2233, Printex FP, PV Fast Green GNX, PV Fast Yellow HG, Irgazine Yellow K2070, Byferox 3910, Irgazine Red K3840, Chromophthal Orange GP, Heliogen Blue K7090, and Heliogen Green K8730. The pigments disclosed in detail should be understood as merely representative examples of the various pigments that may be used.

[0097]

[0096] Rutile pigment based on chromium-III oxide, antimony pentoxide, and titanium dioxide, Shikotan Yellow K2112. Any acid-soluble antimony is present in amounts of less than approximately 20 ppm. Furthermore, unavoidable impurities are kept to less than 30 ppm for arsenic, 50 ppm for lead, less than 10 ppm for cadmium, less than 10 ppm for cobalt, less than 10 ppm for copper, less than 50 ppm for nickel, less than 1 ppm for selenium, less than 1 ppm for mercury, and less than 100 ppm for zinc. Shikotan Yellow K2112 conforms to the following provisions and regulations: EU Regulation No. 1935 / 2004 / EC-Article 3, AP(89)1, German BfR IX, and Australian Regulation AS2070-1999, or is authorized by them to conditionally conform to the restrictions on use under EU (EC) Regulation 10 / 2011, France Brochure 1227, Spanish Royal Decree 847 / 2011, Italian Ministerial Decree 21 / 3 / 73, FDA 21CFR, Japan JHOSPA, and Chinese Regulation GB9685-2008. This pigment does not conform to Japan JHPA.

[0098]

[0097] Kronos 2211, Kronos 2220, and Kronos 2233 are representative rutile pigments produced by the chloride process and represent the R2 compound corresponding to DIN EN ISO 591 Part 1, containing at least 95.5% by weight, 92.5% by weight, and 96% by weight of TiO2, respectively, and are stabilized with aluminum, aluminum and silicon, and aluminum and silicon-containing compounds, respectively. The scattering forces of plastisol formulations containing the same may be approximately 10⁵, 99, and 10⁴, respectively. Various grades of titanium dioxide may be used depending on the intended design requirements. For example, Kronos 2233 is a titanium dioxide that is unaffected by the decomposition of the carrier polymer and maintains its coloring effect even at high processing temperatures.

[0099]

[0098] Printex FP is representative of Pigment Black 7 (Color Index #77266) conforming to 21 CFR §178.3297. Other black pigments that may be used include carbon black particles and graphite particles.

[0100]

[0099] PV Fast Green GNX represents, but is not limited to, Pigment Green 7 (copper phthalocyanine) that is FDA compliant under 21 CFR §178.3297.

[0101] [000100]PV Fast Yellow HG represents Pigment Yellow 180 (benzimidazolone), which is FDA compliant under 21 CFR §176.170 for applications where the food-contact surface meets the conditions of Use B, Use C, Use D, Use E, Use F, and Use G from Table 2. The pigment was not explicitly stated as compliant for applications meeting the conditions of Use A or Use H.

[0102] [000101] Irgazine Yellow K2070 is representative of Pigment Yellow 110 (Isoindolinone) and conforms to the following provisions and regulations: EU Regulation No. 1935 / 2004 / EC-Article 3, EU (EC) Regulation 10 / 2011, AP(89)1, German BfR IX, Spanish Royal Decree 847 / 2011, Italian Ministerial Decree 21 / 3 / 73, Australian Regulation AS2070-1999, and Chinese Regulation GB9685-2008, or authorized by them, and conditionally conforms to the restrictions on use under French Official Journal 1227, FDA 21CFR, and Japanese JHOSPA and JHPA.

[0103] [000102] Biferox 3910 is representative of Pigment Yellow 42 (Yellow Iron Oxide: FeO(OH)·xH2O). The pigments will not lose any arsenic (3 ppm or less), cadmium (1 ppm or less), lead (10 ppm or less), or mercury (1 ppm or less) during drying, and the pigments will not lose any of the following provisions and regulations: EU AP(89)1, Germany BfR IX, France Circulaire 176 dated 2 December 1959, Netherlands Goods Law / Packaging Regulations; Implementation Guidelines CIII-55, Spain Resolution 4.1L1982 dated 4.1L1982 under Article 5 of Royal Decree 211 / 1992, Australia AS2070.6, USA 21CFR178.3297, and Japan JHOSPA, or will be authorized by them.

[0104] [000103] Irgazine Red K3840 is representative of Pigment Red 254 (Diketopyrrolopyrrole) and conforms to the following provisions and regulations: EU Regulation No. 1935 / 2004 / EC-Article 3, EU (EC) Regulation 10 / 2011, AP(89)1, German BfR IX, French Official Journal 1227, Spanish Royal Decree 847 / 2011, Italian Ministerial Decree 21 / 3 / 73, and Australian Regulation AS2070-1999, or authorized by them, and conditionally conforms to the restrictions on use under FDA 21CFR, Japan JHOSPA and JHPA, and Chinese Regulation GB9685-2008.

[0105] [000104] Chromophthal Orange GP is representative of Pigment Orange 64 (disazo condensate) and conforms to the following provisions and regulations: EU Regulation No. 1935 / 2004 / EC-Article 3, EU (EC) Regulation 10 / 2011, AP(89)1, German BfR IX, French Official Journal 1227, Spanish Royal Decree 847 / 2011, Italian Ministerial Decree 21 / 3 / 73, and Australian Regulation AS2070-1999, or authorized by them, and conditionally conforms to the restrictions on use under FDA 21CFR, Japan JHOSPA, and Chinese Regulation GB9685-2008.

[0106] [000105] Heliogen Blue K7090 represents Pigment Blue 15:3 or non-chlorinated copper phthalocyanine (beta form containing approximately 11% by weight of copper) and conforms to the following provisions and regulations: EU Regulation No. 1935 / 2004 / EC-3, AP(89)1, German BfR IX, Japanese JHPA, and Australian Regulation AS2070-1999, or authorized by them, and conditionally conforms to the restrictions on use under EU (EC) Regulation 10 / 2011, French Official Journal 1227, Spanish Royal Decree 847 / 2011, Italian Ministerial Decree 21 / 3 / 73, FDA 21CFR, Japanese JHOSPA, and Chinese Regulation GB9685-2008. Inevitably, impurities are limited to less than 20 ppm of antimony, less than 20 ppm of arsenic, less than 20 ppm of lead, less than 30 ppm of cadmium, less than 50 ppm of chromium, less than 20 ppm of selenium, less than 20 ppm of mercury, and less than 20 ppm of zinc. Any primary aromatic amines are also limited to less than 100 ppm.

[0107] [000106] Heliogen Green K8730 is representative of Pigment Green 7 or Chlorinated Copper Phthalocyanine (containing approximately 5.6% by weight of copper) and conforms to or is authorized by the following provisions and regulations: AP(89)1 and, conditionally, conforms to the restrictions on use under EU Regulation No. 1935 / 2004 / EC-Article 3, EU(EC) Regulation 10 / 2011, German BfR IX, French Official Journal 1227, Spanish Royal Decree 847 / 2011, Italian Ministerial Decree 21 / 3 / 73, FDA 21CFR, Japan JHOSPA, Japan JHPA, Australian Regulation AS2070-1999, and Chinese Regulation GB9685-2008. Inevitably, impurities are limited to less than 20 ppm of antimony, less than 20 ppm of arsenic, less than 20 ppm of lead, less than 30 ppm of cadmium, less than 50 ppm of chromium, less than 20 ppm of selenium, less than 20 ppm of mercury, and less than 20 ppm of zinc. Any primary aromatic amines are also limited to less than 100 ppm.

[0108] [000107] In order to form a powder from the polymer composition of the present disclosure, in one embodiment, the components of the polymer composition may be mixed together and then melt-blended. For example, the components may be melt-blended in an extruder. The processing temperature may vary depending on the type of polyoxymethylene polymer selected for use in the application. In one embodiment, the processing temperature may be about 165°C to about 200°C.

[0109] [000108] Extruded strands can be manufactured, which are then pelletized. The pelletized compound can then be ground to a suitable particle size and a suitable particle size distribution to produce a powder that is well suitable for use in rotational molding.

[0110] [000109] For example, the powder composition can be produced using any suitable hammer mill or granulator. In one embodiment, cryogenic grinding is used to produce particles having a relatively small size and a uniform particle size distribution. Cryogenic grinding can produce powder having particles that are not only uniform in size but also nearly spherical in shape.

[0111] [000110] Once the polymer composition is formulated and formed into a powder having a controlled particle size distribution, the polymer particles are filled into a mold for manufacturing a molded article. The polymer particles are particularly well suited for use in rotational molding methods. During rotational molding, the polymer particles are filled into the mold, and the mold is rotated at least around a first axis and a second axis while being heated. The polymer composition is heated to its melting temperature, causing the polymer composition to flow and coat the inner wall of the mold to produce a hollow container.

[0112] [000111] Particularly advantageous is that the polymer compositions of the present disclosure containing polyoxymethylene polymers can be incorporated into rotational molding applications using conventional equipment without modification. For example, the polymer particles of the present disclosure can be formulated to have bulk density and flow properties that are well suitable for rotational molding. For example, the particles can exhibit a funnel flow of less than about 35 seconds, e.g., less than about 30 seconds, e.g., less than about 25 seconds, e.g., less than about 20 seconds, and generally more than about 5 seconds, when measured in accordance with the ARM funnel test (100 grams). The particles can have a loose bulk density higher than about 0.37 g / cc, e.g., higher than about 0.4 g / cc, e.g., higher than about 0.42 g / cc, and generally less than about 0.6 g / cc.

[0113] [000112] When manufacturing rotationally molded articles, it is necessary not to pre-dry the powder, and the use of nitrogen during molding is unnecessary. In addition, the polymer compositions of the present disclosure can be easily removed from the mold after cooling without the need for special coatings or tools. The polymer compositions of the present disclosure also exhibit excellent flow properties, even when molding intricate designs.

[0114] [000113] Rotational molded articles can be manufactured in relatively fast cycle times according to the present disclosure. For example, a rotational molded article having a wall thickness of 3.8 mm can be manufactured in less than about 20 minutes, for example, less than about 18 minutes, and generally more than about 10 minutes, for example more than about 15 minutes, at an oven temperature of about 204°C (400°F) to about 232°C (450°F). With a wall thickness of 5.1 mm, the article can be manufactured in generally less than about 25 minutes, for example less than about 21 minutes, and generally more than about 12 minutes, for example more than about 18 minutes. The air cooling time is generally less than about 30 minutes. For example, when rotated in air, the cooling time may be about 0 to about 10 minutes. When rotated in forced air, the cooling time may be about 10 to about 20 minutes.

[0115] [000114] Accordingly, according to the present disclosure, a rotationally molded article made from a single layer of material having a wall thickness of about 3.8 mm to about 5.1 mm can be manufactured in a total cycle time (heating and cooling) of less than about 60 minutes, for example less than about 51 minutes, for example less than about 45 minutes, for example less than about 30 minutes, and generally more than about 15 minutes.

[0116] [000115] All kinds of rotational molded articles can be manufactured according to the present disclosure. Generally, rotational molded articles generally contain internal hollows. Therefore, the polymer compositions of the present disclosure are well suited in particular to manufacturing containers for food. The containers may be, for example, food totes, food storage containers, or any suitable food container designed to be stored at room temperature, in a refrigerator, or in a freezer.

[0117] [000116] Referring to Figure 1, one embodiment of a food container 10 manufactured according to the present disclosure is shown. In this embodiment, the food container 10 is a food tote having a relatively large storage capacity. The food tote 10 comprises an internal hollow portion 12 defined and surrounded by a plurality of container walls 14. In one embodiment, the container walls 14 may be made of a single layer of polymer composition. In addition, the container 10 may be seamless, thereby dramatically improving its strength, in particular the impact strength of the container.

[0118] [000117] Referring to Figure 2, another embodiment of a food container 20 manufactured according to the present disclosure is shown. In this embodiment, the food container 20 is a food storage container. The food storage container 20 includes a lid 22 that is rotatably attached to a container body 24. The container body 24 defines the internal volume and is formed by one or more container walls.

[0119] [000118] Rotationally molded containers manufactured in accordance with this disclosure can be formed with low voids and therefore high density. The density of the polymer layer used to form the container is about 1250 kg / m³ when it contains an impact modifier. 3 It can be higher than that, for example, about 1260 kg / m³3 It can be higher than that, for example, about 1270 kg / m³ 3 It can be higher than that, for example, about 1280 kg / m³ 3 It can be higher than that, for example, about 1290 kg / m³ 3 It can be higher than that, for example, about 1300 kg / m 3 It can be higher than that, for example, about 1310 kg / m³ 3 It can be higher than that, for example, about 1350 kg / m³ 3 It can be higher than that, and generally around 2000 kg / m 3 It can be less than 1450 kg / m³, for example. 3 It is acceptable to be less than [a certain value].

[0120] [000119] In one embodiment, the container can have a relatively small capacity. For example, the container can have a capacity of less than about 37.9 L (10 gallons), for example less than about 18.9 L (5 gallons), for example less than about 15.1 L (4 gallons), for example less than about 7.6 L (2 gallons), and generally greater than about 0.4 L (0.1 gallons). Alternatively, larger capacity tanks can be manufactured. For example, a tank can have a capacity greater than approximately 37.9 L (10 gallons), for example greater than approximately 56.8 L (15 gallons), for example greater than approximately 75.7 L (20 gallons), for example greater than approximately 189.3 L (50 gallons), for example greater than approximately 378.5 L (100 gallons), for example greater than approximately 567.8 L (150 gallons), for example greater than approximately 757.1 L (200 gallons), and generally less than approximately 2271.2 L (600 gallons), for example less than approximately 1892.7 L (500 gallons), for example less than approximately 1514.2 L (400 gallons).

[0121] [000120] The polymer compositions of this disclosure and rotational molded articles produced in accordance with this disclosure can have an excellent balance of mechanical properties. The polymer compositions have a density of about 9 kJ / m 2 Larger than that, for example, about 10 kJ / m³ 2 Larger than that, for example, about 12 kJ / m³ 2 Larger than that, for example, about 14 kJ / m³2 Larger than that, for example, about 16 kJ / m³ 2 Larger than that, for example, about 18 kJ / m³ 2 Larger than that, and generally around 90 kJ / m³ 2 A notched Charpy impact strength of less than 23°C can be observed. The notched Charpy impact strength can be measured using injection-molded specimens in accordance with ISO Test 179.

[0122] [000121] Vessels manufactured in accordance with this disclosure may also be tested for multiaxial impact strength in accordance with the ARM low-temperature impact test (V4) at 23°C (t=3mm). The multiaxial impact strength may be greater than about 6.78 Nm (about 5 ft-lbs), for example greater than about 10.17 Nm (about 7.5 ft-lbs), for example greater than about 12.204 Nm (about 9 ft-lbs), for example greater than about 13.56 Nm (about 10 ft-lbs), for example greater than about 16.273 Nm (about 12 ft-lbs), for example about 18.984 Nm (about 14 ft It may be greater than -lbs, for example greater than approximately 21.696 Nm (approximately 16 ft-lbs), for example greater than approximately 24.408 Nm (approximately 18 ft-lbs), for example greater than approximately 27.12 Nm (approximately 20 ft-lbs), for example greater than approximately 29.832 Nm (approximately 22 ft-lbs), and generally less than approximately 135.601 Nm (approximately 100 ft-lbs).

[0123] [000122] When tested in accordance with ISO Test 527, the polymer composition may exhibit a tensile yield strength greater than about 30 MPa, for example greater than about 35 MPa, for example greater than about 38 MPa, and generally less than about 80 MPa.

[0124] [000123] The polymer composition can exhibit a relatively high thermal deflection temperature. For example, the polymer composition can exhibit a thermal deflection temperature at 0.45 MPa in accordance with ISO Test 75 that is higher than about 100°C, e.g., higher than about 110°C, e.g., higher than about 120°C, e.g., higher than about 130°C, and generally below about 160°C. When tested at 1.8 MPa, the thermal deflection temperature may be higher than about 60°C, e.g., higher than about 62°C, e.g., higher than about 64°C, e.g., higher than about 66°C, e.g., higher than about 68°C, and below about 90°C. [Examples]

[0125] [000124]This disclosure may be better understood by referring to the following embodiments. Example 1 [000125] Polymer compositions were formulated in accordance with this disclosure and tested for various properties. The polymer compositions contained a food-grade polyoxymethylene polymer combined with a food-grade thermoplastic elastomer. The thermoplastic elastomer was a thermoplastic polyurethane polyester elastomer. The thermoplastic elastomer had a Shore A hardness of approximately 85 to 87 when tested in accordance with ASTM test D2240 and a melt flow rate of 50 g / 10 min when tested at 190°C and a load of 8.7 kg in accordance with ISO test 1131-1. The polymer compositions were formulated so as not to contain any UV stabilizers or coupling agents. In addition, the amount of antioxidants was relatively high when the compositions were formulated. When the raw materials were extruded together, a powder with an average particle size of 500 microns (35 mesh) was formed. The formulations tested were as follows:

[0126] [Table 3]

[0127] [000126] The composition was tested for various physical properties and the following results were obtained.

[0128] [Table 4]

[0129] [000127] The above-mentioned compounded compositions were compared with food-contact-compatible polypropylene compositions. Only the polypropylene compositions had a density of 0.9 g / cc, a tensile yield strength of 24 MPa, and a flexural modulus of 1150 MPa. Only the polypropylene compositions also showed a thermal deflection temperature of 90°C at 0.45 MPa and a thermal deflection temperature of 50°C at 1.8 MPa. Only the polypropylene compositions also showed a notched Charpy impact strength of 8.2 kJ / m at 23°C. 2 This was shown.

[0130] Example 2 [000128] Further polymer compositions were formulated in accordance with the present disclosure and tested for various properties, similar to the methods and procedures described in Example 1.

[0131] [000129] The following polymer compositions were formulated and tested.

[0132] [Table 5]

[0133] The above composition exhibited the following properties.

[0134] [Table 6]

[0135] [000130] These modifications and changes to the present invention, as well as other modifications and changes, may be carried out by those skilled in the art without departing from the spirit and scope of the invention, which are shown in more detail in the appended claims. In addition, it should be understood that the various embodiments are interchangeable, either in whole or in part. Furthermore, those skilled in the art will recognize that the foregoing descriptions are merely illustrative and not intended to limit the invention as further described in the appended claims.

Claims

1. A polymer composition for rotational molding applications comprising polymer particles containing a polyoxymethylene polymer blended with an impact modifier, wherein the impact modifier comprises a thermoplastic elastomer, the polyoxymethylene polymer has a melt flow rate of less than about 5 g / 10 min, the polyoxymethylene polymer is present in the polymer composition in an amount of at least about 55% by weight, the impact modifier is present in the polymer composition in an amount of about 4% to about 27% by weight, the polymer particles further contain a nucleating agent and an antioxidant, and the polymer particles have an average particle size of about 250 microns to about 800 microns.

2. The polymer composition according to claim 1, wherein the impact-resistant modifier satisfies the requirements of European Food Regulation 10 / 2011 and FDA Food Regulation FDA 21CFR 177.2470, U.S. Code of Federal Regulations, Title 21.

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

4. The polymer composition according to claim 1, 2, or 3, wherein the impact resistance modifier comprises a thermoplastic polyurethane elastomer.

5. The polymer composition according to claim 4, wherein the impact resistance modifier includes polyester polyurethane.

6. The polymer composition according to claim 4 or 5, wherein the thermoplastic polyurethane elastomer has a melt flow rate, measured at 190°C and a load of 2.16 kg, greater than about 7 g / 10 min, for example greater than about 8 g / 10 min, for example greater than about 9 g / 10 min, and less than about 25 g / 10 min, for example less than about 20 g / 10 min, for example less than about 18 g / 10 min, for example less than about 15 g / 10 min.

7. The polymer composition according to any one of claims 4 to 6, wherein the thermoplastic polyurethane elastomer has a melting temperature of about 150°C to about 180°C.

8. The polymer composition according to any one of claims 4 to 7, wherein the thermoplastic polyurethane elastomer has a Shore A hardness greater than about 78, for example greater than about 80, for example greater than about 82, for example greater than about 84, and less than about 95, for example less than about 92, for example less than about 89, as measured in accordance with ASTM Test D2240.

9. The polymer composition according to claim 1, 2, or 3, wherein the impact resistance modifier comprises a thermoplastic polyester elastomer.

10. The polymer composition according to claim 9, wherein the impact resistance modifier comprises a polyether ester.

11. The polymer composition according to claim 9 or 10, wherein the thermoplastic polyester elastomer has a melt flow rate, measured at 190°C and a load of 2.16 kg, greater than about 7 g / 10 min, for example greater than about 8 g / 10 min, for example greater than about 9 g / 10 min, and less than about 25 g / 10 min, for example less than about 20 g / 10 min, for example less than about 18 g / 10 min, for example less than about 15 g / 10 min.

12. The polymer composition according to any one of claims 9 to 11, wherein the thermoplastic polyester elastomer has a melting temperature of about 150°C to about 180°C.

13. The polymer composition according to any one of claims 9 to 12, wherein the thermoplastic polyester elastomer has a Shore A hardness greater than about 78, for example greater than about 80, for example greater than about 82, for example greater than about 84, and less than about 95, for example less than about 92, for example less than about 89, as measured in accordance with ASTM Test D2240.

14. The polymer composition according to claim 1, 2, or 3, wherein the impact resistance modifier comprises a thermoplastic polyurethane elastomer, a thermoplastic polyester elastomer, or a combination thereof.

15. The polymer composition according to any one of claims 1 to 14, wherein the nucleating agent comprises a terpolymer.

16. A polymer composition according to any one of claims 1 to 15, which does not contain any ultraviolet stabilizers.

17. The polymer composition according to any one of claims 1 to 16, further comprising an acid scavenger, wherein the acid scavenger comprises a carboxylate salt.

18. The polymer composition according to claim 17, wherein the carboxylate salt comprises an alkaline earth metal salt of a carboxylic acid.

19. The polymer composition according to claim 18, wherein the acid scavenger comprises calcium citrate, calcium propionate, or a mixture thereof, and the acid scavenger is present in the polymer composition in an amount of about 0.001% to about 1% by weight.

20. The polymer composition according to claim 18, wherein one or more acid scavengers are present in the polymer composition in an amount of less than about 0.08% by weight.

21. The polymer composition according to any one of claims 1 to 20, wherein the polymer composition contains calcium propionate and tricalcium citrate, and the calcium propionate is present in a weight ratio of about 4:1 to about 1.2:1 with respect to the calcium citrate.

22. A polymer composition according to any one of claims 1 to 21, which does not contain guanamine, urea, or melamine formaldehyde scavenger.

23. A polymer composition according to any one of claims 1 to 22, further comprising a plasticizer.

24. The polymer composition according to claim 23, wherein the plasticizer contains polyethylene glycol, and the polyethylene glycol is present in the polymer composition in an amount of about 0.01% to about 2% by weight, for example, about 0.1% to about 0.8% by weight.

25. A polymer composition according to any one of claims 1 to 22, which does not contain polyethylene glycol.

26. A polymer composition according to any one of claims 1 to 25, comprising at least one coloring agent, including a yellow coloring agent, a blue coloring agent, a red coloring agent, an orange coloring agent, a green coloring agent, a white coloring agent, a black coloring agent, or a mixture thereof.

27. A polymer composition for rotational molding applications comprising polymer particles containing a polyoxymethylene polymer blended with an impact modifier, wherein the impact modifier comprises a thermoplastic elastomer, the polyoxymethylene polymer has a melt flow rate of less than about 10 g / 10 min, the polyoxymethylene polymer is present in the polymer composition in an amount of at least about 55% by weight, the impact modifier is present in the polymer composition in an amount of about 4% to about 27% by weight, the polymer particles have an average particle size of about 250 microns to about 800 microns, the polymer composition further comprises a masterbatch containing a colorant combined with a carrier polymer, the colorant is present in the polymer composition in an amount of less than about 1% by weight, and the polymer composition has a strength of 500 kJ / m ２ A polymer composition exhibiting a color difference delta E of less than approximately 10, in accordance with SAE test J2527.

28. The polymer composition according to claim 27, exhibiting a color difference delta E of less than approximately 5, for example less than approximately 4, for example less than approximately 3, for example less than approximately 2.5, for example less than approximately 2, for example less than approximately 1.

5.

29. The polymer composition according to claim 27 or 28, wherein the coloring agent comprises carbon black or graphite.

30. The polymer composition according to any one of claims 27 to 29, wherein the carrier polymer comprises a polyethylene polymer or a polyoxymethylene polymer and is present in the masterbatch in an amount of about 50% to about 99% by weight.

31. A food contact product comprising a seamless rotationally molded food container that defines an internal space in contact with food ingredients, wherein the food container includes a wall surface made of a polymer composition according to any one of claims 1 to 30.

32. A food contact product according to claim 31, comprising a food storage container or food tote.

33. The food contact product according to claim 31 or 32, wherein the wall surface has a thickness of approximately 0.5 mm to approximately 10 mm.

34. The food contact product according to any one of claims 31 to 33, wherein the polymer composition satisfies the requirements of European Food Regulation 10 / 2011 and U.S. Code of Federal Regulations 21 relating to food contact polymers.

35. The food contact product according to any one of claims 31 to 34, wherein the food container has an internal volume greater than about 11.4 L (3 gallons), for example greater than about 18.9 L (5 gallons), for example greater than about 37.9 L (10 gallons), for example greater than about 75.7 L (20 gallons), for example greater than about 151.4 L (40 gallons), for example greater than about 227.1 L (60 gallons), for example greater than about 378.5 L (100 gallons), and less than about 3028.3 L (800 gallons), for example less than about 1892.7 L (500 gallons), for example less than about 1514.2 L (400 gallons), for example less than about 1135.6 L (300 gallons), for example less than about 757.1 L (200 gallons).

36. The polymer composition contains approximately 9 kJ / m³ ２ Larger than that, for example, about 10 kJ / m³ ２ Larger than that, for example, about 12 kJ / m³ ２ Larger than that, for example, about 14 kJ / m³ ２ Larger than that, and approximately 90 kJ / m³ ２ A food contact product according to any one of claims 31 to 35, exhibiting a notched Charpy impact strength of less than 23°C in accordance with ISO Test 179.

37. The food contact product according to any one of claims 31 to 36, wherein the polymer composition exhibits a thermal deflection temperature at 0.45 MPa in accordance with ISO Test 75, which is higher than about 100°C, for example, higher than about 110°C, for example, higher than about 120°C, for example, higher than about 130°C, and less than about 160°C.

38. The food contact product according to any one of claims 31 to 37, wherein the polymer composition exhibits a tensile yield strength in accordance with ISO Test 527, which is greater than about 30 MPa, for example, greater than about 35 MPa, for example, greater than about 38 MPa, and less than about 80 MPa.

39. The food contact product according to any one of claims 31 to 38, wherein the wall surface of the food container has a density in accordance with ISO test 1183, which is higher than 1 g / cc, for example, higher than about 1.1 g / cc, for example, higher than about 1.2 g / cc, for example, higher than about 1.3 g / cc, and less than about 1.6 g / cc.

40. The food contact product according to any one of claims 31 to 39, wherein the polymer composition exhibits a melt flow rate greater than about 1 g / 10 min and less than about 10 g / 10 min, for example, a melt flow rate of about 1 g / 10 min to about 6 g / 10 min, for example, a melt flow rate of about 2 g / 10 min to about 4.5 g / 10 min.

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