Halogen-free flame retardant polymer composition

Abstract

The present invention provides a polymer composition comprising: a first ethylene-based polymer having a crystallinity of 25 wt% or more at 110°C as measured according to the Crystallinity Test; a second ethylene-based polymer having a crystallinity of 40 wt% or less at 23°C as measured according to the Crystallinity Test; and 40 wt% or more of a halogen-free flame retardant filler.

Description

BACKGROUND TECHNICAL FIELD

[0002] The present disclosure relates generally to polymeric compositions, and more specifically to polymeric compositions comprising mineral fillers such as metal hydrates and metal carbonates.

[0003] ABSTRACT

[0004] Halogen-free flame retardant (HFFR) polyolefin-based cable jacket compositions can be used in various applications where the flame retardancy of the insulation / jacket material is important. Flame retardancy is typically achieved by the addition of mineral fillers that dilute the concentration of flammable polymeric material and decompose at a temperature lower than the degradation temperature of the polymer upon exposure to heat. The decomposition of metal hydrates releases water, thereby removing heat from the source of the fire, and the decomposition of metal carbonates produces carbon dioxide that acts as a gas / vapor phase diluent. Conventional HFFR cable jacket compositions are used in indoor, building, train, automotive, or any place where people can be present. In many cases, the polyolefin (or olefinic polymer) is an ethylene-based polymer.

[0005] There are a number of disadvantages to using mineral fillers in polyolefin wire and cable formulations, most of which are due to the relatively high levels of fillers required to meet flame retardant specifications. Polyolefin filler loadings of 40 percent by weight (wt.%) or higher are not uncommon. Such loadings of fillers can affect the properties of the HFFR cable jacket composition and result in compounds with high density, limited flexibility, and reduced mechanical properties such as tensile elongation at break.

[0006] Blends of amorphous or low crystallinity olefinic polymers must typically be used to allow for the inclusion of such high filler loadings. Low crystallinity at room temperature (i.e., 23 °C) is considered advantageous in increasing filler loadings since crystalline regions in the polymer cannot accept fillers. Thus, as the crystalline fraction decreases (and the amorphous fraction increases), the olefinic polymer allows for greater filler loading levels. Despite accommodating high filler loadings, resulting in high tensile elongation at break values, olefinic polymers with high amorphous fractions typically result in lower resistance to mechanical deformation and cannot pass traditional HFFR cable jacket tests such as the “hot press” or “hot knife” indentation tests specified by IEC 60811-508. In essence, there is a tradeoff between the stiffness (modulus) of the olefinic polymer due to crystallinity and the maximum filler loading that the polymer can achieve. To overcome the low resistance to mechanical deformation, crosslinking of the olefinic polymer can be performed to enhance the mechanical properties of the cable jacket, but this typically has a detrimental effect on the tensile elongation at break.

[0007] In view of the above, it is surprising to find a polymer composition having a HFFR content of 40 wt% or greater and a crystallinity of the vinyl polymer at 110°C of 25 wt% or greater that exhibits a hot knife indentation of less than 50% as measured according to IEC 60811-508 and a tensile elongation at break at 23°C of 100% or greater as measured according to ASTM D638. SUMMARY

[0008] The present invention provides a polymer composition having a HFFR content of 40 wt% or greater and a crystallinity of the vinyl polymer at 110°C of 25 wt% or greater that exhibits a hot knife indentation of less than 50% as measured according to IEC 60811-508 and a tensile elongation at break at 23°C of 100% or greater as measured according to ASTM D638.

[0009] The present invention is the result of the discovery that by using a polymer that maintains a crystallinity of 25 wt% or greater at 110°C, the polymer composition is effectively hardened to pass the hot knife test while not unnecessarily reducing the maximum filler content of the polymer composition to maintain a sufficiently high tensile elongation at break at 23°C. The crystallinity of a polymer generally decreases as temperature increases, but the rate of decrease of crystallinity per unit temperature is different for different polymers. For conventionally used polymers, not only does the polymer become softer at elevated temperatures due to loss of crystallinity, but the filler acceptance, which impacts the total filler loading while maintaining a sufficiently high tensile elongation at break at 23°C, is adversely affected by the high crystallinity at 23°C. In essence, the filler acceptance (and thus the total filler loading) is reduced due to the crystallinity that ultimately does not help pass the hot knife test. This relationship is not recognized by the prior art as it generally focuses on the crystallinity at room temperature. In contrast, the present invention uses a polymer that maintains a crystallinity of 25 wt% or greater at 110°C not only makes the polymer composition sufficiently hard to pass the hot knife test, but it also enables the introduction of a HFFR content of 40 wt% or greater while maintaining a sufficiently high tensile elongation at break at 23°C. Surprisingly, it has been found that a crystallinity of 25 wt% or greater at 110°C is sufficient to pass the hot knife test.

[0010] The present invention is particularly suitable for coated conductors.

[0011] According to a first feature of the present disclosure, a polymer composition comprises: a first vinyl polymer having a crystallinity at 110°C of 25 wt% or greater as measured according to the Crystallinity Test; a second vinyl polymer having a crystallinity at 23°C of 40 wt% or less as measured according to the Crystallinity Test; and a halogen-free flame retardant filler of 40 wt% or greater.

[0012] According to a second feature of the present disclosure, the halogen-free flame retardant filler is magnesium hydroxide.

[0013] According to a third feature of the present disclosure, the polymer composition comprises 40 to 65 weight percent of the magnesium hydroxide, based on the total weight of the polymer composition.

[0014] According to a fourth feature of the present disclosure, the polymer composition comprises 5 to 40 weight percent of the second ethylene-based polymer, based on the total weight of the polymer composition.

[0015] According to a fifth feature of the present disclosure, the polymer composition comprises 5 to 40 weight percent of the first ethylene-based polymer, based on the total weight of the polymer composition.

[0016] According to a sixth feature of the present disclosure, the first ethylene-based polymer has a density of 0.925 to 0.950 g / cc.

[0017] According to a seventh feature of the present disclosure, the first ethylene-based polymer comprises a low density component having a density in the range of 0.910 to 0.935 g / cc as measured according to ASTM D792.

[0018] According to an eighth feature of the present disclosure, the first ethylene-based polymer comprises a high density component having a density in the range of 0.945 to 0.965 g / cc as measured according to ASTM D792.

[0019] According to a ninth feature of the present disclosure, the first ethylene-based polymer has an oxidation induction time of 20 minutes or more at 200°C as measured according to ASTM D3895.

[0020] According to a tenth feature of the present disclosure, a coated conductor comprises a conductor and a polymer composition disposed at least partially around the conductor. DETAILED DESCRIPTION

[0021] As used herein, the term "and / or," when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0022] All ranges include endpoints unless otherwise indicated.

[0023] Test methods refer to the latest test method as of the priority date of this document unless the date is indicated with the test method number as a two-digit number with a hyphen. References to test methods include both a reference to the test society and the test method number. Test method organizations are referenced by one of the following abbreviations: ASTM refers to ASTM International (formerly known as American Society for Testing and Materials); IEC refers to International Electrotechnical Commission; EN refers to European Standard; DIN refers to Deutsches Institut fur Normung; and ISO refers to International Organization for Standardization.

[0024] As used herein, unless otherwise indicated, the term weight percent (“wt%”) means the weight percent of a component based on the total weight of the polymer composition.

[0025] Melt index (I2) values herein refer to values determined according to ASTM method D1238 at 190 degrees Celsius (°C) and 2.16 kilogram (Kg) mass and are provided in units of grams eluted per ten minutes (“g / 10 min”).

[0026] Density values herein refer to values determined according to ASTM D792 at 23 °C and are provided in units of grams per cubic centimeter (“g / cc”).

[0027] As used herein, Chemical Abstracts Service Registry Number (“CAS #”) refers to the unique numerical identifier assigned to a chemical compound by the Chemical Abstracts Service as of the priority date of this document.

[0028] Polymer composition

[0029] The present disclosure relates to a polymer composition. The polymer composition includes a first ethylene-based polymer, a second ethylene-based polymer, and a halogen-free flame retardant filler.

[0030] Ethylene-based polymer

[0031] As noted above, the polymer composition includes a first ethylene-based polymer and a second ethylene-based polymer. As used herein, an “ethylene-based polymer” is a polymer in which greater than 50 wt% of the monomers are ethylene, although other comonomers can also be used. “Polymer” means a macromolecular compound composed of a plurality of identical or different types of monomers bonded together, and includes homopolymers and interpolymers. “Interpolymer” means a polymer comprising at least two different monomer types bonded together. Interpolymers include copolymers (typically used to refer to polymers prepared from two different monomer types) and polymers prepared from more than two different monomer types (e.g., terpolymers (three different monomer types) and tetrapolymers (four different monomer types)). The ethylene-based polymer can be an ethylene homopolymer. As used herein, “homopolymer” denotes a polymer comprising repeat units derived from a single monomer type, although not precluding residual amounts of other components such as catalysts, initiators, solvents, and chain transfer agents used to prepare the homopolymer.

[0032] The ethylene-based polymer can include 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, 85 wt% or more, 90 wt% or more, or 91 wt% or more, or 92 wt% or more, or 93 wt% or more, or 94 wt% or more, or 95 wt% or more, or 96 wt% or more, or 97 wt% or more, or 97.5 wt% or more, or 98 wt% or more, or 99 wt% or more while at the same time 100 wt% or less, 99.5 wt% or less, or 99 wt% or less, or 98 wt% or less, or 97 wt% or less, or 96 wt% or less, or 95 wt% or less, or 94 wt% or less, or 93 wt% or less, or 92 wt% or less, or 91 wt% or less, or 90 wt% or less, or 85 wt% or less, or 80 wt% or less, or 70 wt% or less, or 60 wt% or less of ethylene as measured using nuclear magnetic resonance (NMR) or Fourier transform infrared (FTIR) spectroscopy. Non-limiting examples of suitable ethylene-based polymers include ethylene / alpha-olefin (alpha-olefin) copolymers, ethylene / C3-C8 alpha-olefin copolymers, ethylene / C4-C8 alpha-olefin copolymers, and copolymers of ethylene with one or more of the following comonomers: acrylic esters, (meth)acrylic acid, (meth)acrylic esters, carbon monoxide, maleic anhydride, vinyl acetate, vinyl propionate, maleic acid monoester, maleic acid diester, vinyl trialkoxy silane, vinyl trialkyl silane, and any combination thereof. Suitable ethylene-based polymers also include those in which these comonomers are grafted onto the ethylene-based polymer. Other units of the ethylene-based polymer can include C3 alpha-olefins, or C4 alpha-olefins, or C6 alpha-olefins, or C8 alpha-olefins, or C 10 alpha-olefins, or C 12alpha-olefins, or C 16 alpha-olefins, or C 18 alpha-olefins, or C 20 alpha-olefins, such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene.

[0033] The ethylene-based polymers can have a unimodal or multimodal molecular weight distribution and can be used alone or in combination with one or more other types of ethylene-based polymers (e.g., a blend of two or more ethylene-based polymers that differ from one another in monomer composition and content, catalytic production method, molecular weight, molecular weight distribution, density, etc.). If a blend of ethylene-based polymers is employed, the polymers can be blended by any in-reactor or post-reactor method.

[0034] The polymer composition includes a first ethylene-based polymer and a second ethylene-based polymer. The first ethylene-based polymer and the second ethylene-based polymer for the polymer composition can differ from one another in density, melt flow index, chemical composition, molecular weight distribution, crystallinity at different temperatures, and oxidation induction time.

[0035] First ethylene-based polymer

[0036] The first ethylene-based polymer can have a density of 0.925 g / cc to 0.950 g / cc. For example, the first ethylene-based polymer can have a density of 0.925 g / cc or greater, or 0.930 g / cc or greater, or 0.935 g / cc or greater, or 0.940 g / cc or greater, or 0.945 g / cc or greater while at the same time 0.950 g / cc or less, or 0.945 g / cc or less, or 0.940 g / cc or less, or 0.935 g / cc or less, or 0.930 g / cc or less.

[0037] The first ethylene-based polymer can have a melt index of 0.1 g / 10 min. to 5 g / 10 min. For example, the first ethylene-based polymer can have a melt index of 0.1 g / 10 min. or more, or 0.5 g / 10 min. or more, or 1.0 g / 10 min. or more, or 1.5 g / 10 min. or more, or 2.0 g / 10 min. or more, or 2.5 g / 10 min. or more, or 3.0 g / 10 min. or more, or 3.5 g / 10 min. or more, or 4.0 g / 10 min. or more, or 4.5 g / 10 min. or more, while 5.0 g / 10 min. or less, or 4.5 g / 10 min. or less, or 4.0 g / 10 min. or less, or 3.5 g / 10 min. or less, or 3.0 g / 10 min. or less, or 2.5 g / 10 min. or less, or 2.0 g / 10 min. or less, or 1.5 g / 10 min. or less, or 1.0 g / 10 min. or less, or 0.5 g / 10 min. or less. The melt index is measured according to ASTM D1238 at 190 °C and 2.16 kg.

[0038] In a multimodal specific example, the first ethylene-based polymer comprises a high molecular weight (“low density”) component and a low molecular weight (“high density”) component.

[0039] The low density component of the ethylene-based polymer can have a density of 0.910 g / cc to 0.935 g / cc. For example, the low density component of the first ethylene-based polymer can have a density of 0.910 g / cc or more, or 0.915 g / cc or more, or 0.920 g / cc or more, or 0.925 g / cc or more, or 0.930 g / cc or more, while 0.935 g / cc or less, or 0.930 g / cc or less, or 0.925 g / cc or less, or 0.920 g / cc or less, or 0.915 g / cc or less.

[0040] The low density component of the first ethylene-based polymer can have a melt index of 0.1 g / 10 min. to 1.0 g / 10 min. For example, the melt index of the low density component can be 0.01 g / 10 min. or more, or 0.1 g / 10 min. or more, or 0.2 g / 10 min. or more, or 0.3 g / 10 min. or more, or 0.4 g / 10 min. or more, or 0.5 g / 10 min. or more, or 0.6 g / 10 min. or more, or 0.7 g / 10 min. or more, or 0.8 g / 10 min. or more, or 0.9 g / 10 min. or more, while 1.0 g / 10 min. or less, or 0.9 g / 10 min. or less, or 0.8 g / 10 min. or less, or 0.7 g / 10 min. or less, or 0.6 g / 10 min. or less, or 0.5 g / 10 min. or less, or 0.4 g / 10 min. or less, or 0.3 g / 10 min. or less, or 0.2 g / 10 min. or less, or 0.1 g / 10 min. or less. The melt index is measured according to ASTM D1238 at 190 °C and 2.16 kg.

[0041] The high density component of the first ethylene-based polymer can have a density of 0.945 g / cc to 0.965 g / cc. For example, the density of the high density component of the first ethylene-based polymer can be 0.945 g / cc or more, or 0.950 g / cc or more, or 0.955 g / cc or more, or 0.960 g / cc or more, while 0.965 g / cc or less, or 0.960 g / cc or less, or 0.955 g / cc or less, or 0.950 g / cc or less.

[0042] The high density component of the first ethylene-based polymer can have a melt index of 2.0 g / 10 min. to 200 g / 10 min. For example, the melt index of the high density component can be 2.0 g / 10 min. or more, or 10 g / 10 min. or more, or 20 g / 10 min. or more, or 50 g / 10 min. or more, or 100 g / 10 min. or more, or 150 g / 10 min. or more, while 200 g / 10 min. or less, or 150 g / 10 min. or less, or 100 g / 10 min. or less, or 50 g / 10 min. or less, or 20 g / 10 min. or less, or 10 g / 10 min. or less, or 5 g / 10 min. or less. The melt index is measured according to ASTM D1238 at 190 °C and 2.16 kg.

[0043] The first ethylene-based polymer has a crystallinity at 110°C of 25 wt% or more as measured according to the Crystallinity Test. The Crystallinity Test is defined in detail in the Examples section below. The first ethylene-based polymer has a crystallinity at 110°C of 25 wt% or more, or 30 wt% or more, or 35 wt% or more, or 40 wt% or more, or 45 wt% or more, or 50 wt% or more, or 55 wt% or more, or 60 wt% or more, or 65 wt% or more while 70 wt% or less, or 65 wt% or less, or 60 wt% or less, or 55 wt% or less, or 50 wt% or less, or 45 wt% or less, or 40 wt% or less, or 35 wt% or less, or 30 wt% or less as measured according to the Crystallinity Test. The first ethylene-based polymer can have a crystallinity at 23°C of 40 wt% to 70 wt% as measured according to the Crystallinity Test. For example, the first ethylene-based polymer has a crystallinity at 23°C of 40 wt% or more, or 45 wt% or more, or 50 wt% or more, or 55 wt% or more, or 60 wt% or more, or 65 wt% or more while 70 wt% or less, or 65 wt% or less, or 60 wt% or less, or 55 wt% or less, or 50 wt% or less, or 45 wt% or less as measured according to the Crystallinity Test.

[0044] The first ethylene-based polymer has an oxidation induction time (“OIT”) at 200°C of 20 minutes or more as measured according to ASTM D3895. For example, the first ethylene-based polymer can have an oxidation induction time at 200°C of 20 minutes or more, or 30 minutes or more, or 40 minutes or more, or 50 minutes or more, or 60 minutes or more, or 70 minutes or more, or 80 minutes or more, or 90 minutes or more, or 100 minutes or more, or 110 minutes or more, or 120 minutes or more, or 130 minutes or more, or 140 minutes or more, or 150 minutes or more while 160 minutes or less, or 150 minutes or less, or 140 minutes or less, or 130 minutes or less, or 120 minutes or less, or 110 minutes or less, or 100 minutes or less, or 90 minutes or less, or 80 minutes or less, or 70 minutes or less, or 60 minutes or less as measured according to ASTM D3895. It is believed that an increase in OIT value at 200°C beneficially resists degradation in modulus of the polymer composition after heat exposure, allowing for better performance in hot knife testing.

[0045] The polymer composition can include 5 wt% or more, or 10 wt% or more, or 15 wt% or more, or 20 wt% or more, or 25 wt% or more, or 30 wt% or more, or 35 wt% or more while 40 wt% or less, or 35 wt% or less, or 30 wt% or less, or 25 wt% or less, or 20 wt% or less, or 15 wt% or less, or 10 wt% or less of the first ethylene-based polymer, based on the total weight of the polymer composition.

[0046] Second ethylene-based polymer

[0047] The second ethylene-based polymer can have a density of 0.860 g / cc or more, or 0.865 g / cc or more, or 0.870 g / cc or more, or 0.880 g / cc or more, or 0.885 g / cc or more, or 0.890 g / cc or more, or 0.900 g / cc or more, or 0.910 g / cc or more, or 0.920 g / cc or more while 1.000 g / cc or less, or 0.990 g / cc or less, or 0.980 g / cc or less, or 0.970 g / cc or less, or 0.960 g / cc or less, or 0.950 g / cc or less, or 0.940 g / cc or less, or 0.930 g / cc or less, or 0.920 g / cc or less, or 0.910 g / cc or less, or 0.900 g / cc or less, or 0.890 g / cc or less, or 0.880 g / cc or less, or 0.870 g / cc or less, as measured according to ASTM D792.

[0048] The second ethylene-based polymer can have a solubility index of 1 g / 10 min. or more, or 2 g / 10 min. or more, 3 g / 10 min. or more, 4 g / 10 min. or more, 5 g / 10 min. or more, 6 g / 10 min. or more, 7 g / 10 min. or more, 8 g / 10 min. or more, 9 g / 10 min. or more, 10 g / 10 min. or more, or 11 g / 10 min. or more, or 12 g / 10 min. or more, 13 g / 10 min. or more, 14 g / 10 min. or more, 15 g / 10 min. or more, 16 g / 10 min. or more, 17 g / 10 min. or more, 18 g / 10 min. or more, 19 g / 10 min. or more while at the same time 20 g / 10 min. or less, or 19 g / 10 min. or less, or 18 g / 10 min. or less, or 17 g / 10 min. or less, or 16 g / 10 min. or less, or 15 g / 10 min. or less, or 14 g / 10 min. or less, or 13 g / 10 min. or less, or 12 g / 10 min. or less, or 11 g / 10 min. or less, or 10 g / 10 min. or less, or 9 g / 10 min. or less, or 8 g / 10 min. or less, or 7 g / 10 min. or less, or 6 g / 10 min. or less, or 5 g / 10 min. or less, or 4 g / 10 min. or less, or 3 g / 10 min. or less, or 2 g / 10 min. or less. The melt index is measured according to ASTM D1238 at 190 °C and 2.16 kg.

[0049] The second ethylene-based polymer has a crystallinity at 23 °C of 40 wt% or less as measured according to the Crystallinity Test. For example, the second ethylene-based polymer can have a crystallinity at 23 °C of 40 wt% or less, or 35 wt% or less, or 30 wt% or less, or 25 wt% or less, or 20 wt% or less, or 15 wt% or less, or 10 wt% or less, or 5 wt% or less, or 0 wt% while at the same time 1 wt% or more, or 5 wt% or more, or 10 wt% or more, or 15 wt% or more, or 20 wt% or more, or 25 wt% or more, or 30 wt% or more, or 35 wt% or more as measured according to the Crystallinity Test.

[0050] The polymer composition can include 5 wt.% or more, or 10 wt.% or more, or 15 wt.% or more, or 20 wt.% or more, or 25 wt.% or more, or 30 wt.% or more, or 35 wt.% or more while 40 wt.% or less, or 35 wt.% or less, or 30 wt.% or less, or 25 wt.% or less, or 20 wt.% or less, or 15 wt.% or less, or 10 wt.% or less, or 9 wt.% or less, or 8 wt.% or less, or 7 wt.% or less, or 6 wt.% or less, or 5 wt.% or less, or 4 wt.% or less, or 3 wt.% or less, or 2 wt.% or less, or 1 wt.% or less of the second ethylene-based polymer, based on the total weight of the polymer composition.

[0051] In some examples, the polymer composition can include a second ethylene-based polymer that is a copolymer of ethylene with one or more (co)polymerized or grafted) of a comonomer selected from the group consisting of: acrylate, (meth)acrylic acid, (meth)acrylate, carbon monoxide, maleic anhydride, vinyl acetate, vinyl propionate, maleic acid monoester, maleic acid diester, vinyl trialkoxysilane, vinyl trialkylsilane, and combinations thereof. The polymer composition can include a concentration of 0 wt.% or more, or 1 wt.% or more, or 2 wt.% or more, or 3 wt.% or more, or 4 wt.% or more, or 5 wt.% or more, or 6 wt.% or more, or 7 wt.% or more, or 8 wt.% or more, or 9 wt.% or more, or 10 wt.% or more, or 15 wt.% or more, or 20 wt.% or more, or 25 wt.% or more while 30 wt.% or less, or 25 wt.% or less, or 20 wt.% or less, or 15 wt.% or less, or 10 wt.% or less, or 9 wt.% or less, or 8 wt.% or less, or 7 wt.% or less, or 6 wt.% or less, or 5 wt.% or less, or 4 wt.% or less, or 3 wt.% or less, or 2 wt.% or less, or 1 wt.% or less of the second ethylene-based polymer, based on the total weight of the polymer composition, of such examples.

[0052] In some examples, the polymer composition can include a maleated second ethylene-based polymer. As used herein, the term “maleated” denotes an ethylene-based polymer that has been modified to incorporate maleic anhydride monomers. The maleated ethylene-based polymer can be formed by copolymerization of maleic anhydride monomers with ethylene and other monomers, if present, to produce an interpolymer having maleic anhydride incorporated into the polymer backbone. Additionally or alternatively, the maleic anhydride can be grafted to the ethylene-based polymer. Maleated examples of the second ethylene-based polymer can be used to act as a compatibilizer between the ethylene-based polymer and the HFFR of the polymer composition.

[0053] The maleated second vinyl polymer can have a maleic anhydride content of 0.25 wt-% or more, or 0.50 wt-% or more, or 0.75 wt-% or more, or 1.00 wt-% or more, or 1.25 wt-% or more, or 1.50 wt-% or more, or 1.75 wt-% or more, or 2.00 wt-% or more, or 2.25 wt-% or more, or 2.50 wt-% or more, or 2.75 wt-% or more, while 3.00 wt-% or less, or 2.75 wt-% or less, or 2.50 wt-% or less, or 2.25 wt-% or less, or 2.00 wt-% or less, or 1.75 wt-% or less, or 1.50 wt-% or less, or 1.25 wt-% or less, or 1.00 wt-% or less, or 0.75 wt-% or less, or 0.5 wt-% or less, based on the total weight of the maleated second vinyl polymer. The maleic anhydride concentration is determined by titration analysis. The titration analysis is performed by using dry resin and titrating with 0.02 N KOH to determine the amount of maleic anhydride. The dry polymer is titrated by dissolving 0.3 to 0.5 grams of the maleated polymer in about 150 mL of refluxing xylene. After complete dissolution, deionized water (four drops) is added to the solution and the solution is refluxed for 1 hour. Next, 1% thymol blue (a few drops) is added to the solution and the solution is over-titrated with 0.02 N KOH in ethanol as indicated by the formation of a purple color. The solution is then back-titrated to a yellow end point with 0.05 N HC1 in isopropyl alcohol.

[0054] The polymer composition can comprise 0 wt-% or more, or 1 wt-% or more, or 2 wt-% or more, or 3 wt-% or more, or 4 wt-% or more, or 5 wt-% or more, or 6 wt-% or more, or 7 wt-% or more, or 8 wt-% or more, or 9 wt-% or more, while 10 wt-% or less, or 9 wt-% or less, or 8 wt-% or less, or 7 wt-% or less, or 6 wt-% or less, or 5 wt-% or less, or 4 wt-% or less, or 3 wt-% or less, or 2 wt-% or less, or 1 wt-% or less of the maleated second vinyl polymer, based on the total weight of the polymer composition.

[0055] Halogen-free flame retardant filler

[0056] The halogen-free flame retardant of the polymer composition can suppress, retard, or delay the production of flames. Examples of halogen-free flame retardants suitable for use in the polymer composition include, but are not limited to, metal hydrates, metal carbonates, red phosphorus, silicon dioxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium oxide, carbon nanotubes, talc, clay, organically modified clay, calcium carbonate, zinc borate, antimony trioxide, wollastonite, mica, ammonium octamolybdate, glass frit, hollow glass microspheres, intumescent compounds, expanded graphite, and combinations thereof. In one embodiment, the halogen-free flame retardant can be selected from the group consisting of aluminum hydroxide, magnesium hydroxide, calcium carbonate, and combinations thereof. The halogen-free flame retardant can optionally be surface treated (coated) with a saturated or unsaturated carboxylic acid having 8 to 24 carbon atoms or 12 to 18 carbon atoms or a metal salt of the acid. Exemplary surface treatments are described in US 4,255,303, US 5,034,442, US 7,514,489, US 2008 / 0251273, and WO 2013 / 116283. Alternatively, the acid or salt can be added to the composition in similar amounts without using a surface treatment procedure. Other surface treatments known in the art can also be used, including silanes, titanates, phosphates, and zirconates.

[0057] Examples of commercially available halogen-free flame retardants suitable for use in the compositions according to the present disclosure include, but are not limited to: APYRAL TM 40CD aluminum hydroxide, MAGNIFIN TM H5 magnesium hydroxide, Microcarb 95T ultrafine and treated calcium carbonate, available from Reverte, and combinations thereof.

[0058] The polymer composition can include the HFFR filler in a concentration of 40 wt% or more, or 42 wt% or more, or 44 wt% or more, or 46 wt% or more, or 48 wt% or more, or 50 wt% or more, or 52 wt% or more, or 54 wt% or more, or 56 wt% or more, or 58 wt% or more, or 60 wt% or more, or 62 wt% or more, or 64 wt% or more, or 66 wt% or more, or 68 wt% or more, or 70 wt% or more, or 72 wt% or more, or 74 wt% or more, or 76 wt% or more, or 78 wt% or more, while 80 wt% or less, or 78 wt% or less, or 76 wt% or less, or 74 wt% or less, or 72 wt% or less, or 70 wt% or less, or 68 wt% or less, or 66 wt% or less, or 64 wt% or less, or 62 wt% or less, or 60 wt% or less, or 58 wt% or less, or 56 wt% or less, or 54 wt% or less, or 52 wt% or less, or 50 wt% or less, or 48 wt% or less, or 46 wt% or less, or 44 wt% or less, or 42 wt% or less, based on the weight of the polymer composition.

[0059] Additive

[0060] The polymer composition can include additional additives in the form of antioxidants, crosslinking coagents, cure accelerators and scorch retarders, processing aids, coupling agents, ultraviolet light stabilizers (including UV absorbers), antistatic agents, additional nucleating agents, slip agents, lubricants, viscosity control agents, tackifiers, anti-blocking agents, surfactants, extender oils, acid scavengers, flame retardants, anti-drip agents (such as ethylene vinyl acetate), and metal deactivators. The polymer composition can include from 0.01 wt% to 20 wt% of one or more of the additional additives.

[0061] The UV light stabilizers can include hindered amine light stabilizers (“HALS”) and UV light absorbers (“UVA”) additives. Representative UVA additives include benzotriazole types such as TINUVIN 326 TM TINUVIN 328 TM TINUVIN 328

[0062] Antioxidants may include hindered phenols such as tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydro-cinnamate)]methane; bis[(β-(3,5-di-tert-butyl-4-hydroxybenzyl)methylcarboxyethyl)]-sulfide, 4,4'-thiobis(2-methyl-6-tert-butylphenol), 4,4'-thiobis(2-tert-butyl-5-methylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol) and thiodiethylenebis(3,5-di-tert-butyl-4-hydroxy)-hydrocinnamate; phosphites and phosphonites , such as tris(2,4-di-tert-butylphenyl)phosphite and di-tert-butylphenyl-phosphite; thio compounds, such as dilaurylthiodipropionate, dimyristylthiodipropionate and distearylthiodipropionate; various siloxanes; polymeric 2,2,4-trimethyl-1,2-dihydroquinoline, n,n'-bis(1,4-dimethylpentyl-p-phenylenediamine), alkylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, diphenyl-p-phenylenediamine, mixed diaryl-p-phenylenediamines and other hindered amine antidegradants or stabilizers.

[0063] Processing aids may include metal salts of carboxylic acids, such as zinc stearate or calcium stearate; fatty acids, such as stearic acid, oleic acid or erucic acid; fatty amides, such as stearamide, oleamide, erucamide or N,N'-ethylenebisstearamide; polyethylene waxes; oxidized polyethylene waxes; polymers of ethylene oxide; copolymers of ethylene oxide and propylene oxide; vegetable waxes; petroleum waxes; nonionic surfactants; silicone fluids and polysiloxanes.

[0064] Compounding and coating of the conductor

[0065] The component of polymer composition can be added in batches or continuous mixer to form the composition of melt blending.Can add component in any order or first prepare one or more masterbatches to be blended with other components.Melt blending can be carried out at a temperature higher than the melting point of the highest molten polymer.Then the melt blended composition can be transported in an extruder or injection molding machine, or be formed into required goods through a mold, or be converted into pellets, adhesive tape, strips or films or some other forms to be used for storage or preparation and be supplied to the material of next shaping or processing step.Optionally, if shaped as pellets or some similar configurations, pellets etc. can be coated with a release agent so that the processing when storage.

[0066] Examples of compounding equipment used include internal batch mixers such as the BANBURY TM or BOLLING TM Internal mixer. Alternatively, a continuous single screw or twin screw mixer such as a FARRELL TM Continuous mixer, WERNER TM and PFLEIDERERTM Twin screw mixer or BUSS TM Kneading Continuous Extruder. The type of mixer utilized and the operating conditions of the mixer will affect the properties of the composition, such as viscosity, volume resistivity and extruded surface smoothness.

[0067] A coated conductor can be made from a polymer composition. The coated conductor includes a conductor and a coating. The coating comprises a polymer composition. The polymer composition is at least partially disposed around the conductor to produce the coated conductor. The conductor can include a conductive metal or an optically transparent structure.

[0068] A method for preparing a coated conductor comprises mixing and heating a polymer composition in an extruder to at least the melting temperature of the polymer components to form a polymer melt blend, and then applying the polymer melt blend to a conductor. The term "onto" includes direct or indirect contact between the polymer melt blend and the conductor. The polymer melt blend is in an extrudable state.

[0069] The polymer composition is disposed on and / or around the conductor to form a coating. The coating may be one or more inner layers, such as an insulating layer. The coating may completely or partially cover or otherwise surround or encase the conductor. The coating may be the sole component surrounding the conductor. Alternatively, the coating may be a layer of a multi-layer jacket or sheath surrounding the conductor. The coating may directly contact the conductor. The coating may directly contact the insulating layer surrounding the conductor.

[0070] Examples

[0071] Materials

[0072] The following materials were used in the following examples.

[0073] 2EP(A) is an ethylene-based polymer with octene comonomer and exhibiting a density of 0.885 g / cc, a melt index of 1.0 g / 10 min., a crystallinity of 23 wt% at 23°C, and is commercially available from The Dow Chemical Company, Midland, MI.

[0074] 2EP(B) is an ethylene-based polymer having a butene comonomer and exhibiting a density of 0.865 g / cc and a melt index of 5.0 g / 10 min., a crystallinity of 9 wt% at 23°C, and is commercially available from The Dow Chemical Company, Midland, MI.

[0075] LLDPE is a linear low density polyethylene having a density of 0.92 g / cc, a melt index of 1.0 g / 10 min., a total crystallinity of 52 wt%, a crystallinity at 23°C of 50 wt%, a crystallinity at 110°C of 20 wt%, an OIT at 200°C of 25 minutes, and is commercially available from The Dow Chemical Company, Midland, MI.

[0076] 1 EP(A) is an ethylene-based polymer having a density of 0.931 g / cc, a melt index of 0.70 g / 10 min., a total crystallinity of 57 wt%, a crystallinity at 23°C of 56 wt%, a crystallinity at 110°C of 35 wt%, an OIT at 200°C of 123 minutes, and is commercially available from The Dow Chemical Company, Midland, MI.

[0077] 1 EP(B) is an ethylene-based polymer having a density of 0.941 g / cc, a melt index of 0.55 g / 10 min., a total crystallinity of 66 wt%, a crystallinity at 23°C of 65 wt%, a crystallinity at 110°C of 50 wt%, an OIT at 200°C of 146 minutes, and is commercially available from The Dow Chemical Company, Midland, MI.

[0078] 1 EP(C) is an ethylene-based polymer having a density of 0.940 g / cc, a melt index of 1.0 g / 10 min., a total crystallinity of 64 wt%, a crystallinity at 23°C of 63 wt%, a crystallinity at 110°C of 48 wt%, an OIT at 200°C of 25 minutes, and is commercially available from The Dow Chemical Company, Midland, MI.

[0079] MAH-2 EP(A) is a maleic anhydride grafted ethylene-based polymer having a density of 0.93 g / cc, a melt index of 1.75 g / 10 min., and a maleic anhydride content of 0.9 wt%, and is commercially available from The Dow Chemical Company, Midland, MI.

[0080] MAH-2 EP(B) is a maleic anhydride grafted ethylene-based polymer having a density of 0.88 g / cc, a melt index of 3.7 g / 10 min., and a maleic anhydride content of 0.9 wt%, and is commercially available from The Dow Chemical Company, Midland, MI.

[0081] HFFR1 is magnesium hydroxide, an example of which can be obtained under the trade designation MAGNIFIN® HFFR 1 from Magnifin GmbH, Germany. TMH-5MV was commercially available from Huber (Martinswerk GMBH), Bergheim, Germany.

[0082] HFFR2 was magnesium hydroxide (brucite) coated with 1.5% fatty acid, commercially available as Ecopiren 3.5 LC from Europiren, Rotterdam, Netherlands.

[0083] VA-2EP(A) was an ethylene vinyl acetate copolymer with a vinyl acetate content of 28 wt%, a density of 0.95 g / cc, a melt index of 6.0 g / 10 min, and a total crystallinity of 21 wt%, and was commercially available from The Dow Chemical Company, Midland, MI.

[0084] VA-2EP(B) was an ethylene vinyl acetate copolymer with a vinyl acetate content of 28 wt%, a density of 0.951 g / cc, a melt index of 400 g / 10 min, and a total crystallinity of 21 wt%, and was commercially available from The Dow Chemical Company, Midland, MI.

[0085] Stabilizer MB was a masterbatch for stabilizing olefin polymer compounds, commercially available as SILMASTAB TM AX1440 was a single-component thermal processing metal passivation aging stabilizer commercially available from Silma s.r.l., Italy.

[0086] Anti-hydrolysis MB was a masterbatch for stabilizing olefin polymer compounds, commercially available as SILMASTAB TM AX2244 was commercially available from Silma s.r.l., Italy.

[0087] SiMB1 was a master pelletized formulation containing 50 wt% ultra-high molecular weight siloxane polymer dispersed in low density polyethylene, and was obtained as Siloxane MB 50-002 from DuPont, Wilmington, Delaware.

[0088] SiMB2 was a polydimethylsiloxane-based masterbatch for use as a slip agent, external lubricant, and mold release agent, and was commercially available as SILMAPROCESS TM AL1142A was commercially available from Silma s.r.l., Italy.

[0089] Test methods

[0090] Crystallinity Test: The melting peak and percent (%) or weight percent (wt%) crystallinity of the ethylene-based polymer is determined using a differential scanning calorimeter (DSC) instrument, DSC Q1000 (TA Instruments). (A) Baseline calibrate the DSC instrument. Use the software calibration wizard. Obtain the baseline by heating the cell from -80 °C to 280 °C in an aluminum DSC pan without any sample. Then use the sapphire standard indicated by the calibration wizard. Analyze a fresh indium sample of 1 milligram (mg) to 2 mg by heating the standard sample to 180 °C, cooling to 120 °C at a cooling rate of 10 °C / minute, then isothermally holding the standard sample at 120 °C for 1 minute, then heating the standard sample from 120 °C to 180 °C at a heating rate of 10 °C / minute. Determine the heat of fusion of the indium standard sample = 28.71 ± 0.50 Joules / gram (J / g) and the melting onset = 156.6 °C ± 0.5 °C. (B) Perform a DSC measurement on the test sample using the baseline calibrated DSC instrument. Press the test sample of semi-crystalline ethylene-based polymer into a thin film at a temperature of 160 °C. Weigh 5 mg to 8 mg of the test sample film in an aluminum DSC pan. Press the lid onto the pan to seal the pan and ensure a closed atmosphere. Place the pan sealed with the lid into the DSC cell, equilibrate the cell at 30 °C, then heat to 190 °C at a rate of about 100 °C / minute, hold the sample at 190 °C for 3 minutes, cool the sample to -60 °C at a rate of 10 °C / minute to obtain the cold curve heat of fusion (AHcold) and isothermally hold at -60 °C for 3 minutes. Then heat the sample again to 190 °C at a rate of 10 °C / minute to obtain the second heat curve heat of fusion (AHsecond). Using the second heat curve, calculate the “total” heat of fusion (J / g) by integrating from -20 °C (in the case of ethylene homopolymers, copolymers of ethylene and hydrolysable silane monomers, and ethylene alpha-olefin copolymers having a density greater than or equal to 0.90 g / cc) or -40 °C (in the case of copolymers of ethylene and unsaturated ester, and ethylene alpha-olefin copolymers having a density less than 0.90 g / cc) to the melting end point. Using the second heat curve, calculate the “room temperature” heat of fusion (J / g) from 23 °C (room temperature) to the melting end point by vertical drop at 23 °C. Using the second heat curve, calculate the “110 °C” heat of fusion (J / g) from 110 °C to the melting end point by vertical drop at 110 °C. Measure and report the “total crystallinity” (calculated from the “total” heat of fusion) as well as the “crystallinity at room temperature” (calculated from the 23 °C heat of fusion) and the “crystallinity at 110 °C” (calculated from the 110 °C heat of fusion). From the second heat curve heat of fusion (AHsecond) of the test sample, calculate the “total crystallinity” (wt%) using the following equation: Total Crystallinity (wt%) = (AHsecond) x (0.218) x 100 f ), and isothermally hold at -60 °C for 3 minutes. Then heat the sample again to 190 °C at a rate of 10 °C / minute to obtain the second heat curve heat of fusion (AH f ). Using the second heat curve, calculate the “total” heat of fusion (J / g) by integrating from -20 °C (in the case of ethylene homopolymers, copolymers of ethylene and hydrolysable silane monomers, and ethylene alpha-olefin copolymers having a density greater than or equal to 0.90 g / cc) or -40 °C (in the case of copolymers of ethylene and unsaturated ester, and ethylene alpha-olefin copolymers having a density less than 0.90 g / cc) to the melting end point. Using the second heat curve, calculate the “room temperature” heat of fusion (J / g) from 23 °C (room temperature) to the melting end point by vertical drop at 23 °C. Using the second heat curve, calculate the “110 °C” heat of fusion (J / g) from 110 °C to the melting end point by vertical drop at 110 °C. Measure and report the “total crystallinity” (calculated from the “total” heat of fusion) as well as the “crystallinity at room temperature” (calculated from the 23 °C heat of fusion) and the “crystallinity at 110 °C” (calculated from the 110 °C heat of fusion). From the second heat curve heat of fusion (AHsecond) of the test sample, calculate the “total crystallinity” (wt%) using the following equation: Total Crystallinity (wt%) = (AHsecond) x (0.218) x 100 f) and normalized to the heat of fusion of 100% crystalline polyethylene to measure crystallinity and reported as a percentage (%) or weight percent (wt%) crystallinity of the polymer, where % crystallinity or wt% crystallinity = (ΔH f * 100%) / 292 J / g, where ΔH f As defined above, * denotes mathematical multiplication, / denotes mathematical division, and 292 J / g is the literature value for the heat of fusion (ΔH f ) of 100% crystalline polyethylene.

[0091] Hot knife testing was tested according to IEC 60811-508 and passed by achieving a maximum indentation value of 50% or less after aging in circulating air at 110°C for 6 hours.

[0092] Tensile elongation at break was measured according to ASTM D638 on a 5565 tensile testing machine from Instron Calibration Lab using International Organization for Standardization 527 Type 5a dog bone.

[0093] Sample preparation

[0094] The polymer and masterbatch ingredients of Comparative Examples 1 and 2 and Inventive Examples 1-4 were prepared as follows. About 500 grams of each example was produced on a two-roll mill by first adding the polymer components at 160°C, and second adding the additives to form a blend. After melting and homogenizing for 3 minutes, the HFFR was added to the blend. After complete incorporation of the filler, the molten compound was left on the rolls for 10 minutes, removed as a 1 mm thick sheet, and cooled under ambient conditions. Test specimens for mechanical property testing were cut directly from the sheet.

[0095] Inventive Examples 5-10 were compounded by extrusion on a 25 mm, 42 L / D co-rotating twin-screw extruder via a 300 mm flat slot die. The extrudate was then fed into a three-roll calender to shape 1 mm thick sheet samples. Samples for mechanical testing were then cut from the sheet.

[0096] Results

[0097] Table 1 provides the composition of Comparative (“CE”) Examples 1 and 2 and Inventive Examples (“IE”) 1-IE10. Table 1 provides the tensile elongation at break (“TE”) and hot knife mechanical property data for each example.

[0098]

[0099] As can be seen from Table 1, CE1 and CE2 do not contain a first ethylene-based polymer (i.e., an ethylene-based polymer having a crystallinity at 110°C of 25 wt% or greater) and thus are not able to meet the hot knife performance requirements. Although the crystallinity of 2EP(A) or LLDPE is low enough to allow incorporation of HFFR and meet the TE requirements, the crystallinity at 110°C is too low to pass the hot knife test. IE1-IE10 are all able to meet the TE and hot knife requirements by incorporating a first ethylene-based polymer (i.e., an ethylene-based polymer having a crystallinity at 110°C of 25 wt% or greater). IE1-IE10 demonstrate that the use of an ethylene-based polymer having a crystallinity at 110°C of 35 wt% or greater allows the polymer composition to pass the TE and hot knife requirements. It is believed that the incorporation of an ethylene-based polymer having a crystallinity at 110°C as low as 25 wt% will allow the polymer composition to pass the TE and hot knife requirements. IE1-IE10 also demonstrate that a wide range (i.e., 8 wt% to about 30 wt%) of first ethylene-based polymers can be used in the polymer composition and still achieve the TE and hot knife mechanical properties. It is believed that the use of 5 wt% to 40 wt% of a first ethylene-based polymer will allow the polymer composition to achieve the TE and hot knife mechanical properties. It is also believed that the increased or satisfactory OIT of 1EP(A), 1EP(B), and 1EP(C) at 200°C beneficially resists the deterioration of the modulus of the samples after heat exposure, allowing for better performance in the hot knife test.

Claims

1. A polymer composition comprising: a first ethylene-based polymer having a crystallinity of 25 wt% or greater at 110°C as measured according to the Crystallinity Test; a second ethylene-based polymer having a crystallinity of 40 wt% or less at 23°C as measured according to the Crystallinity Test; and 40 wt% or greater of a halogen-free flame retardant filler.

2. The polymer composition of claim 1, wherein the halogen-free flame retardant filler is magnesium hydroxide.

3. The polymer composition of claim 2, wherein the polymer composition comprises 40 wt% to 65 wt% of magnesium hydroxide, based on the total weight of the polymer composition.

4. The polymer composition of claim 1, wherein the polymer composition comprises 5 wt% to 40 wt% of the second ethylene-based polymer, based on the total weight of the polymer composition.

5. The polymer composition of claim 1, wherein the polymer composition comprises 5 wt% to 40 wt% of the first ethylene-based polymer, based on the total weight of the polymer composition.

6. The polymer composition of claim 5, wherein the first ethylene-based polymer has a density of 0.925 g / cc to 0.950 g / cc.

7. The polymer composition of claim 6, wherein the first ethylene-based polymer comprises a low density component having a density in the range of 0.910 g / cc to 0.935 g / cc as measured according to ASTM D792.

8. The polymer composition of claim 7, wherein the first ethylene-based polymer comprises a high density component having a density in the range of 0.945 g / cc to 0.965 g / cc as measured according to ASTM D792.

9. The polymer composition of claim 1, wherein the first ethylene-based polymer has an oxidation induction time of 20 minutes or greater at 200°C as measured according to ASTM D3895.

10. A coated conductor comprising: a conductor; and the polymer composition of any one of claims 1 to 9 disposed at least partially around the conductor.

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