Compatibilized Polymer Compositions for Optical Fiber Cable Components

Abstract

The polymer composition comprises (a) 1 wt % to 45 wt % of an ethylene-based polymer, (b) 50 wt % to 90 wt % of polybutylene terephthalate having a melt flow index of 21 g / 10 min to 35 g / 10 min at 250 C and 2.16 Kg, and (c) 3.5 wt % to 10 wt % of a compatibilizer comprising a maleated ethylene-based polymer and ethylene n-butyl acrylate glycidyl methacrylate.

Description

Technical Field

[0001] The present disclosure generally relates to compatibilized polymer compositions, and more specifically to polymer compositions comprising compatibilized polybutylene terephthalate and polyethylene blends.

Background Art

[0002] Materials used for optical fiber buffer tubes need to exhibit a balance of rigidity, flexibility, extrudability, and kink resistance. Conventional buffer tubes are mainly composed of extruded polybutylene terephthalate ("PBT"), which provides rigidity but is prone to kinking during the installation of optical fibers. Kinking of the buffer tube is disadvantageous because it can damage the optical fiber.

[0003] Conventional approaches to enhancing the flexibility of buffer tubes involve blending PBT and polyethylene ("PE"). In such blends, PBT provides rigidity and grease resistance for communication, while PE imparts flexibility and kink resistance. A compatibilizer is incorporated into the blend of PBT and PE due to the polarity of PBT and the non-polarity of PE. An example of a conventional compatibilizer is maleic anhydride grafted polyethylene ("MAH-g-PE"). WO2019 / 050627 discloses the use of PBT and PE blends with MAH-g-PE as a compatibilizer. Alternatively, another example of a conventional compatibilizer for blends of PBT and PE is ethylene-n-butyl acrylate-glycidyl methacrylate terpolymer ("ENBAGMA"). WO2019 / 050627 does not mention the use of ENBAGMA.

[0004] Recently, attempts have been made to replace extrusion-grade PBT (i.e., PBT having a melt flow index of less than 21 grams per 10 minutes (g / 10 min) at 250 °C and 2.16 Kg) with a relatively inexpensive injection molding grade of PBT (i.e., PBT having a melt flow index of 21 g / 10 min or more) in a PBT-PE buffer tube. Using injection molding grade PBT reduces the zero shear viscosity of the PBT-PE blend to less than 3000 Pascal seconds (PaS) at 250 °C, thereby reducing extrudability. Buffer tubes extruded from injection molding grade PBT-PE blends exhibit dimensional stability problems such as kinks and non-uniform tube wall thickness that adversely affect crush resistance.

[0005] Therefore, it is surprising to discover a PBT-PE compatibilizer blend that utilizes PBT having a melt flow index greater than 21 g / 10 min, exhibits a zero shear viscosity greater than 3000 PaS at 250 °C, and resists kinking. SUMMARY OF THE INVENTION

[0006] The present invention provides a solution for providing a PBT-PE compatibilized blend comprising PBT having a melt flow index greater than 21 g / 10 min, yet exhibiting a zero shear viscosity greater than 3000 PaS at 250 °C and resisting kinking.

[0007] The present invention is the result of the discovery that (1) ENBAGMA can increase the zero-shear viscosity of injection molding grades of PBT and PE blends, and (2) neither MAH-g-PE nor ENBAGMA alone can maintain the morphological stability of blended PE and PBT through both blending and extrusion. The inventors have discovered that ENBAGMA can bind to multiple PBT polymer chains, thereby increasing the zero-shear viscosity to above 3000 PaS at 250 °C in the case of blended PE and PBT systems that enable extrusion with high buffer tube dimensional uniformity. The inventors have also discovered that both MAH-g-PE and ENBAGMA must be used to maintain the stability of the mixed phase through high-shear events such as mixing and extrusion. The stability of the mixed-phase morphology prevents phase separation that results in insufficient mechanical properties and kinking of the buffer tube. Thus, a relatively lower-cost injection molding grade of PBT can be used to form buffer tubes that withstand kinking. Examples showing a zero-shear viscosity of less than 3000 PaS at 250 °C and no kinking are still desirable.

[0008] The present invention is particularly useful for buffer tubes in optical fiber installations.

[0009] According to a first aspect of the present disclosure, a polymer composition comprises (a) 1 wt% to 45 wt% of an ethylene-based polymer, (b) 50 wt% to 90 wt% of polybutylene terephthalate having a melt flow index of 21 g / 10 min to 35 g / 10 min at 250 °C and 2.16 Kg, and (c) 3.5 wt% to 10 wt% of a compatibilizer comprising maleated ethylene-based polymer and ethylene n-butyl acrylate glycidyl methacrylate.

Brief Description of the Drawings

[0010] Reference is made to the accompanying drawings.

[0011]

Figure 1

Best Mode for Carrying Out the Invention

[0012] As used herein, the term "and / or" when used in a listing of two or more items means that any one of the listed items can be used by itself or any combination of two or more of the listed items can be used. 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 combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

[0013] Unless otherwise specified, all ranges include endpoints. The subscript values in polymer formulas refer to the molar average number of units per molecule of the specified component of the polymer.

[0014] Test methods refer to the latest test methods at the priority date of this document unless the date is indicated by a two-digit number with a hyphen for the test method number. References to test methods include both the reference of the test society and the test method number. The organization of the test method is referred to by any one of the following abbreviations: ASTM refers to ASTM International (formerly American Society for Testing and Materials), EN refers to European standards, DIN refers to Deutsches Institut fur Normung, and ISO refers to the International Organization for Standardization.

[0015] As used herein, "unimodal" means a polymer material having a molecular weight distribution ("MWD") such that its gel permeation chromatography ("GPC") curve shows only a single peak without a second peak, shoulder, or bump. In contrast, "bimodal" as used herein means that the MWD of the GPC curve indicates the presence of a two-component polymer, such as by having two peaks or when one component shows a bump, shoulder, or tail relative to the peak of the other component polymer.

[0016] As used herein, the term weight percent ("wt%") refers to the percentage by weight that a component occupies in the total weight of the polymer composition, unless otherwise specified.

[0017] The melt index (I2) value herein refers to the value determined according to ASTM method D1238 at 190 degrees Celsius (°C) with a mass of 2.16 kilograms (kg).

[0018] Polymer composition The polymer composition of the present invention includes a polyethylene-based polymer, polybutylene terephthalate, and a compatibilizer. As will be described in more detail below, the polyethylene-based polymer may include low-density polyethylene and / or high-density polyethylene. The compatibilizer includes maleated ethylene-based polymer and ethylene n-butyl acrylate glycidyl methacrylate. Such a polymer composition can be extruded to form an optical fiber cable protection component such as a buffer tube.

[0019] Ethylene-based polymer As described above, one component of the polymer composition is an ethylene-based polymer. As used herein, an "ethylene-based" polymer is a polymer in which more than 50 wt% of the monomers are ethylene, although other comonomers can also be used. "Polymer" means a macromolecular compound containing a plurality of the same or different types of monomers bonded together, including homopolymers and interpolymers. "Interpolymer" means a polymer containing at least two different monomer types bonded together. Interpolymers include copolymers (usually used to refer to polymers prepared from two different monomer types), and polymers prepared from three or more different monomer types (e.g., terpolymers (three different monomer types) and quarterpolymers (four different monomer types)).

[0020] The ethylene-based polymer can be an ethylene homopolymer. As used herein, "homopolymer" refers to a polymer containing repeating units derived from a single monomer type, but excluding residual amounts of other components (such as catalysts, initiators, solvents, and chain transfer agents) used in preparing the homopolymer.

[0021] The ethylene-based polymer can be used alone or in combination with one or more other types of ethylene-based polymers (for example, a blend of two or more ethylene-based polymers having different monomer compositions and contents, catalyst preparation methods, molecular weights, molecular weight distributions, densities, etc.). When a blend of ethylene-based polymers is used, the polymers can be blended by any in-reactor process or post-reactor process.

[0022] Examples of suitable commercially available ethylene-based polymers are sold under the trade names AXELERON CX 6944 NT(trademark), DGDA-2300 NT(trademark), and DMDA-1250 NT(trademark), each of which is available from The Dow Chemical Company (Midland, MI, USA).

[0023] The polymer composition may contain an ethylene-based polymer in an amount of 1 wt% or more, or 2 wt% or more, or 4 wt% or more, or 6 wt% or more, or 8 wt% or more, or 10 wt% or more, or 12 wt% or more, or 14 wt% or more, or 16 wt% or more, or 18 wt% or more, or 20 wt% or more, or 22 wt% or more, or 24 wt% or more, or 26 wt% or more, or 28 wt% or more, or 30 wt% or more, or 32 wt% or more, or 34 wt% or more, or 36 wt% or more, or 38 wt% or more, or 40 wt% or more, or 42 wt% or more, or 44 wt% or more, while simultaneously being 45 wt% or less, 44 wt% or less, 42 wt% or less, 40 wt% or less, 38 wt% or less, 36 wt% or less, 34 wt% or less, 32 wt% or less, 30 wt% or less, or 28 wt% or less, or 26 wt% or less, or 24 wt% or less, or 22 wt% or less, or 20 wt% or less, or 18 wt% or less, or 16 wt% or less, or 14 wt% or less, or 12 wt% or less, or 10 wt% or less, or 8 wt% or less, or 6 wt% or less, or 4 wt% or less, or 2 wt% or less.

[0024] The ethylene-based polymer may include low-density polyethylene (「LDPE」). LDPE resins are commercially available and can be produced by any one of a variety of processes including, but not limited to, solution, gas phase or slurry phase Ziegler-Natta, metallocene or constrained geometry catalysts (CGCs). The LDPE resin has a density in the range of 0.91 to 0.94 grams per cubic centimeter (「g / cm 3 」). In various embodiments, the LDPE is at least 0.915 「g / cm 3 」, but less than 0.94 g / cm 3 or less than 0.93 g / cm 3 or less than 0.920 - 0.925 g / cm 3It may have a density within the range of. The polymer density provided herein is determined in accordance with ASTM D792. LDPE may have a melt index I2 of less than 20 grams per 10 minutes ( "g / 10 min"), or in the range of 0.1 g / 10 min to 10 g / 10 min, 2 g / 10 min to 8 g / 10 min, 4 g / 10 min to 8 g / 10 min, or may have an I2 of 1.9 g / 10 min. Generally, LDPE resins have a broad molecular weight distribution ( "MWD") and result in a relatively high polydispersity index (the ratio of weight average molecular weight to number average molecular weight). LDPE may have a polydispersity index ( "PDI") in the range of 1.0 to 30.0, or in the range of 2.0 to 15.0, as determined by gel permeation chromatography. Commercially available LDPE resins are sold under the trade names AXELERON CX B-1258 NT (TM) and DXM 446 (TM), both of which are available from The Dow Chemical Company.

[0025] The polymer composition may contain 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 11 wt% or more, or 12 wt% or more, or 13 wt% or more, or 14 wt% or more, or 15 wt% or more, or 16 wt% or more, or 17 wt% or more, or 18 wt% or more, or 19 wt% or more, or 20 wt% or more, or 21 wt% or more, or 22 wt% or more, or 23 wt% or more, or 24 wt% or more, or 25 wt% or more, while at the same time 24 wt% or less, or 23 wt% or less, or 22 wt% or less, or 21 wt% or less, or 20 wt% or less, or 19 wt% or less, or 18 wt% or less, or 17 wt% or less, or 16 wt% or less, 15 wt% or less, or 14 wt% or less, or 13 wt% or less, or 12 wt% or less, or 11 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 of LDPE.

[0026] The ethylene-based polymer may include high-density polyethylene ( "HDPE"). HDPE has at least 0.94 g / cm3 or at least 0.94 g / cm 3 ~0.98 g / cm 3 and is an ethylene polymer having a density of. HDPE has a melt index of 0.1 g / 10 min to 25 g / 10 min. HDPE can contain ethylene and one or more C3 - C 20 α - olefin comonomers. The comonomer can be linear or branched. Non - limiting examples of suitable comonomers include propylene, 1 - butene, 1 - pentene, 4 - methyl - 1 - pentene, 1 - hexene, and 1 - octene. HDPE can be prepared using any of Ziegler - Natta catalysts, chromium - based catalysts, constrained geometry catalysts or metallocene catalysts in a slurry reactor, a gas - phase reactor or a solution reactor. The ethylene / C3 - C 20 α - olefin comonomer contains at least 50 wt%, or at least 70 wt%, or at least 80 wt%, or at least 85 wt%, or at least 90 wt%, or at least 95 wt% of ethylene in polymerized form. In certain embodiments, HDPE is an ethylene / α - olefin copolymer having a density of 0.95 g / cm 3 ~0.98 g / cm 3 and a melt index of 0.1 g / 10 min to 10 g / 10 min. In certain embodiments, HDPE has a density of 0.960 g / cm 3 ~0.980 g / cm 3 and a melt index of 0.1 g / 10 min to 10 g / 10 min. Non - limiting examples of suitable HDPEs are sold under the trade names ELITE 5960G™, HDPE KT 10000 UE™, HDPE KS 10100 UE™, HDPE 35057E™, and AXELERON CX - A - 6944 NT™, each of which is available from The Dow Chemical Company (Midland, Michigan, USA).

[0027] HDPE can be either unimodal or bimodal. In other embodiments, HDPE is bimodal. Suitable preparation methods for making unimodal HDPE can be found, for example, in U.S. Patent Nos. 4,303,771 or 5,324,800. An example of a commercially available unimodal HDPE is sold under the trade name DGDL-3364NT and is available from The Dow Chemical Company (Midland, MI, USA).

[0028] The polymer composition can include bimodal HDPE. The HDPE includes a first polymer component and a second polymer component. The first component can be an ethylene-based polymer. For example, the first component can be a high molecular weight ethylene homopolymer or an ethylene / alpha-olefin copolymer. The first component can include any amount of one or more alpha-olefin copolymers. For example, the first component can include less than 10 wt% of one or more alpha-olefin comonomers based on the total weight of the first component. The first component can include any amount of ethylene. For example, the first component can include at least 90 wt% ethylene or at least 95 wt% ethylene based on the total weight of the first component. The alpha-olefin comonomer present in the first component of the bimodal HDPE typically has 20 or fewer carbon atoms. For example, the alpha-olefin comonomer can have 3 to 10 carbon atoms, or 3 to 8 carbon atoms. Exemplary alpha-olefin comonomers include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 4-methyl-1-pentene. In one embodiment, the alpha-olefin comonomer can be selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene. In other embodiments, the alpha-olefin comonomer can be selected from the group consisting of 1-hexene and 1-octene.

[0029] The first component of the bimodal HDPE is 0.915 g / cm3 ~0.940 g / cm 3 、0.920 g / cm 3 ~0.940 g / cm 3 、 or 0.921 g / cm 3 ~0.936 g / cm 3 may have a density in the range of. The first component may have a melt index, I2 (190 °C / 2.16 kg), in the range of 0.5 × 10 g / 10 min to 10 g / 10 min, 1 × 10 g / 10 min to 7 g / 10 min, or 1.3 × 10 g / 10 min to 5 g / 10 min. The first component may have a molecular weight in the range of 150,000 g / mol to 375,000 g / mol, 175,000 g / mol to 375,000 g / mol, or 200,000 g / mol to 375,000 g / mol.

[0030] The second polymer component of the bimodal HDPE can be an ethylene-based polymer. For example, the second component can be a low molecular weight ethylene homopolymer. The ethylene homopolymer can contain trace amounts of comonomers, such as alpha-olefin comonomers. In various embodiments, the second component can include less than 1 wt% of one or more alpha-olefin comonomers based on the weight of the second component. For example, the second component can include 0.0001 to 1.00 wt% of one or more alpha-olefin comonomers or 0.001 to 1.00 weight percent of one or more alpha-olefin comonomers. The second component can include at least 99 wt% ethylene or ethylene in the range of 99.5 wt% to 100 wt% based on the weight of the second component.

[0031] The second component of the bimodal HDPE is 0.965 - 0.980 g / cm 3 or 0.970 - 0.975 g / cm 3It may have a density in the range of. The second component may have a melt index (I2) in the range of 50 g / 10 min to 1,500 g / 10 min, 200 g / 10 min to 1,500 g / 10 min, or 500 g / 10 min to 1,500 g / 10 min. The second component may have a molecular weight in the range of 12,000 to 40,000 g / mol, 15,000 to 40,000 g / mol, or 20,000 to 40,000 g / mol.

[0032] Suitable preparation methods for producing bimodal HDPE can be found, for example, in paragraphs

[0063] to

[0086] of US Patent Application Publication No. 2009 / 0068429.

[0033] Examples of commercially available bimodal HDPE are sold under the trade names DMDA-1250NT (trademark) and DMDC 1250 (trademark), both of which are available from The Dow Chemical Company (Midland, MI, USA).

[0034] The polymer composition may contain HDPE at 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 11 wt% or more, or 12 wt% or more, or 13 wt% or more, or 14 wt% or more, or 15 wt% or more, or 16 wt% or more, or 17 wt% or more, or 18 wt% or more, or 19 wt% or more, or 20 wt% or more, or 21 wt% or more, or 22 wt% or more, or 23 wt% or more, or 24 wt% or more, or 25 wt% or more, while simultaneously being 24 wt% or less, or 23 wt% or less, or 22 wt% or less, or 21 wt% or less, or 20 wt% or less, or 19 wt% or less, or 18 wt% or less, or 17 wt% or less, or 16 wt% or less, 15 wt% or less, or 14 wt% or less, or 13 wt% or less, or 12 wt% or less, or 11 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.

[0035] The ethylene-based polymer can comprise, consist of, or consist essentially of HDPE. The ethylene-based polymer can comprise, consist of, or consist essentially of LDPE. HDPE and LDPE can be present in equal weight percentages of the ethylene-based polymer or in different amounts. The ethylene-based polymer can be 0 wt% or more, or 5 wt% or more, or 10 wt% or more, or 20 wt% or more, or 30 wt% or more, or 40 wt% or more, or 50 wt% or more, or 60 wt% or more, or 70 wt% or more, or 80 wt% or more, or 90 wt% or more, or 99 wt% or more, while at the same time being 100 wt% or less, or 90 wt% or less, or 80 wt% or less, or 70 wt% or less, or 60 wt% or less, or 50 wt% or less, or 40 wt% or less, or 30 wt% or less, or 20 wt% or less, or 10 wt% or less, or 5 wt% or less of HDPE. The ethylene-based polymer can be 0 wt% or more, or 5 wt% or more, or 10 wt% or more, or 20 wt% or more, or 30 wt% or more, or 40 wt% or more, or 50 wt% or more, or 60 wt% or more, or 70 wt% or more, or 80 wt% or more, or 90 wt% or more, or 99 wt% or more, while at the same time being 100 wt% or less, or 90 wt% or less, or 80 wt% or less, or 70 wt% or less, or 60 wt% or less, or 50 wt% or less, or 40 wt% or less, or 30 wt% or less, or 20 wt% or less, or 10 wt% or less, or 5 wt% or less of LDPE.

[0036] Polybutylene terephthalate PBT has a density in the range of 1.26 g / cm 3 ~1.41 g / cm 3 or 1.30 g / cm 3 ~1.35 g / cm 3 In one or more embodiments, PBT can have a melt index (I2) in the range of 7 g / 10 min to 15 g / 10 min or 8 g / 10 min to 10 g / 10 min. The melt index of PBT is determined at 250°C and 2.16 Kg.

[0037] In various embodiments, the PBT can be an extrusion grade PBT. In another embodiment, the PBT can be an injection molding grade PBT. Injection molding grade PBT is typically characterized by a lower molecular weight, as evidenced by a relatively higher melt index. Thus, in one or more embodiments, the PBT can have a melt index (I2) of at least 10 g / 10 min, at least 15 g / 10 min, at least 20 g / 10 min, at least 25 g / 10 min, at least 30 g / 10 min, at least 35 g / 10 min, at least 40 g / 10 min, or at least 45 g / 10 min. In such embodiments, the PBT can have a melt index (I2) of up to 75 g / 10 min, up to 70 g / 10 min, up to 65 g / 10 min, up to 60 g / 10 min, up to 55 g / 10 min, or up to 50 g / 10 min.

[0038] Examples of commercially available extrusion grade PBT include those sold under the trade names PBT-61008 (trademark) from Suzhou Yingmao Plastics Company (Jiangsu, China), ULTRADUR BN6550 (trademark) from BASF (Ludwigshafen, Germany), CRASTIN 6129 NC010 (trademark) from DuPont (Wilmington, Delaware, USA), and PBT VALOX176 (trademark) from Sabic Innovative Plastics (Pittsfield, Massachusetts, USA). An example of commercially available injection molding grade PBT is sold under the trade name CRASTIN 6134 (trademark) from DuPont (Wilmington, Delaware, USA).

[0039] The polymer composition contains 50% to 90% by weight of PBT. The polymer composition can contain PBT in an amount of 50% by weight or more, or 52% by weight or more, or 54% by weight or more, or 56% by weight or more, or 58% by weight or more, or 60% by weight or more, or 62% by weight or more, or 64% by weight or more, or 66% by weight or more, or 68% by weight or more, or 70% by weight or more, or 72% by weight or more, or 74% by weight or more, or 76% by weight or more, or 78% by weight or more, or 80% by weight or more, or 82% by weight or more, or 84% by weight or more, or 86% by weight or more, or 88% by weight or more, while simultaneously being 90% by weight or less, or 88% by weight or less, or 86% by weight or less, or 84% by weight or less, or 82% by weight or less, or 80% by weight or less, or 78% by weight or less, or 76% by weight or less, or 74% by weight or less, or 72% by weight or less, or 70% by weight or less, or 68% by weight or less, or 66% by weight or less, or 64% by weight or less, or 62% by weight or less, or 60% by weight or less, or 58% by weight or less, or 56% by weight or less, or 54% by weight or less, or 52% by weight or less.

[0040] Compatibilizer The polymer composition further contains a compatibilizer. The compatibilizer includes both a maleated ethylene-based polymer and ethylene n-butyl acrylate glycidyl methacrylate.

[0041] As used herein, the term "maleated" refers to a polymer (e.g., an ethylene-based polymer) incorporating maleic anhydride monomer. The maleated ethylene-based polymer can be an interpolymer of maleic anhydride monomer (i.e., along the polymer backbone) and ethylene and other monomers. Additionally, or alternatively, maleic anhydride can be bonded to the ethylene-based polymer in a grafted orientation. The above description of the ethylene-based polymer is equally applicable to the maleated ethylene-based polymer.

[0042] The maleated ethylene-based polymer has a density of 0.90 g / cm 3 or more, or 0.91 g / cm 3or more, or 0.92 g / cm 3 or more, or 0.93 g / cm 3 or more, or 0.933 g / cm 3 or more, or 0.935 g / cm 3 or more, or 0.937 g / cm 3 or more, or 0.94 g / cm 3 or more, or 0.943 g / cm 3 or more, or 0.945 g / cm 3 or more, or 0.947 g / cm 3 or more, or 0.95 g / cm 3 or more, or 0.958 g / cm 3 or more, 0.965 g / cm 3 or more, while at the same time 0.97 g / cm 3 or less, or 0.965 g / cm 3 or less, or 0.96 g / cm 3 or less, or 0.95 g / cm 3 or less, or 0.94 g / cm 3 or less, or 0.93 g / cm 3 may have a density of less than.

[0043] The maleated ethylene polymer may have a melt index in the range of 0.1 to 10 g / 10 min, 0.2 to 8 g / 10 min, or 0.5 to 5 g / 10 min at 190 °C and 2.16 Kg.

[0044] "Maleic anhydride content" is defined herein as the amount of reacted maleic anhydride bonded to the ethylene-based polymer. The maleated ethylene-based polymer may 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 at the same time 3.00 wt% or less, 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 ethylene-based polymer. The maleic anhydride content is determined by titration analysis. The titration analysis is carried out by using a dry resin, titrating with 0.02N KOH to determine the amount of maleic anhydride. The dry polymer is titrated by dissolving 0.3 - 0.5 grams of the maleated polymer in about 150 mL of refluxing xylene. After complete dissolution, deionized water (4 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 titrated with 0.02N KOH in ethanol as indicated by the formation of a purple color. Next, the solution is back-titrated with an isopropanol solution of 0.05N HCl to a yellow end point.

[0045] The polymer composition may contain 2.5 wt% to 7.5 wt% of a maleated ethylene-based polymer. For example, the polymer composition may contain 2.5 wt% or more, or 3.0 wt% or more, or 3.5 wt% or more, or 4.0 wt% or more, or 4.5 wt% or more, or 5.0 wt% or more, or 5.5 wt% or more, or 6.0 wt% or more, or 6.5 wt% or more, or 7.0 wt% or more, while simultaneously containing 7.5 wt% or less, or 7.0 wt% or less, or 6.5 wt% or less, or 6.0 wt% or less, or 5.5 wt% or less, or 5.0 wt% or less, or 4.5 wt% or less, or 4.0 wt% or less, or 3.5 wt% or less, or 3.0 wt% or less.

[0046] Examples of suitable commercially available maleated ethylene-based polymers are AMPLIFY TY1053H (trademark), AMPLIFY GR204 (trademark), and AMPLIFY GR205 (trademark) available from The Dow Chemical Company (Midland, MI, USA); the BYNEL (trademark) 4000 series and FUSABOND (trademark) P series products available from DuPont (Wilmington, DE, USA); OREVAC (trademark) grafted polyethylene available from Arkema (Colombes, France); and POLYBOND (trademark) 3000 series grafted polyethylene available from Addivant (Danbury, CT, USA), which are sold under these trade names.

[0047] The compatibilizer also contains ethylene n-butyl acrylate glycidyl methacrylate. ENBAGMA is a random terpolymer of ethylene, acrylic ester, and glycidyl methacrylate.

[0048] ENBAGMA is 0.93 g / cm 3 or more, or 0.933 g / cm 3 or more, or 0.935 g / cm 3 or more, or 0.937 g / cm 3 or more, or 0.94 g / cm 3 or more, or 0.943 g / cm3 or more, or 0.945 g / cm 3 or more, or 0.947 g / cm 3 or more, or 0.95 g / cm 3 or more, or 0.958 g / cm 3 or more, 0.965 g / cm 3 or more, while at the same time 0.97 g / cm 3 or less, or 0.965 g / cm 3 or less, or 0.96 g / cm 3 It may have a density of or less. ENBAGMA may have a melt index in the range of 6 to 14 g / 10 min or 8 to 12 g / 10 min at 190 °C and 2.16 kg.

[0049] ENBAGMA may have a glycidyl methacrylate content of 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 11 wt% or more, or 12 wt% or more, or 13 wt% or more, while at the same time 14 wt% or less, 13 wt% or less, or 12 wt% or less, or 11 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, based on the total weight of ENBAGMA.

[0050] The polymer composition may contain 2.5 wt% to 7.5 wt% of ENBAGMA. For example, the polymer composition may contain 2.5 wt% or more, or 3.0 wt% or more, or 3.5 wt% or more, or 4.0 wt% or more, or 4.5 wt% or more, or 5.0 wt% or more, or 5.5 wt% or more, or 6.0 wt% or more, or 6.5 wt% or more, or 7.0 wt% or more, while at the same time 7.5 wt% or less, or 7.0 wt% or less, or 6.5 wt% or less, or 6.0 wt% or less, or 5.5 wt% or less, or 5.0 wt% or less, or 4.5 wt% or less, or 4.0 wt% or less, or 3.5 wt% or less, or 3.0 wt% or less of ENBAGMA.

[0051] Examples of suitable commercially available ENBAGAs include, but are not limited to, ELVALOY PTW™ and ELVALOY 4170™ from DuPont (Wilmington, Delaware, USA).

[0052] Additives The polymer composition can include one or more particulate fillers such as various mineral-based fillers including glass fibers or nanocomposites. Fillers, particularly those including elongated or platelet-shaped particles that provide a higher aspect ratio (length / thickness), can improve the modulus of elasticity and shrinkage characteristics after extrusion. The filler can have a median size or d50 of less than 20 μm, less than 10 μm, or less than 5 μm. The filler may be surface-treated to promote wetting or dispersion in the polymer composition. Specific examples of suitable fillers include, but are not limited to, calcium carbonate, silica, quartz, fused quartz, talc, mica, clay, kaolin, wollastonite, feldspar, aluminum hydroxide, carbon black, and graphite. The filler may be included in the polymer composition in an amount in the range of 2 to 30 wt%, or 5 to 30 wt%, based on the total weight of the polymer composition.

[0053] The polymer composition can include a nucleating agent. Examples of suitable nucleating agents include ADK NA-11™ commercially available from Asahi Denim Kokai, and HYPERFORM HPN-20E™ available from Milliken Chemical. The nucleating agent may be included in the polymer composition in an amount in the range of 0.08 wt% to 0.3 wt%, 0.09 wt% to 0.25 wt%, or 0.1 to 0.22 wt%, based on the total polymer composition weight.

[0054] The polymer composition may include additional additives in the form of antioxidants, crosslinking aids, curing accelerators and scorch inhibitors, processing aids, coupling agents, ultraviolet stabilizers (including UV absorbers), antistatic agents, additional nucleating agents, slip agents, lubricants, viscosity modifiers, tackifiers, antiblocking agents, surfactants, extender oils, acid scavengers, flame retardants, and metal deactivators. The polymer composition may include 0.01 wt% to 10 wt% of the additives (i.e., one or more of the additives).

[0055] The UV light stabilizers may include hindered amine light stabilizers (“HALS”) and UV light absorber (“UVA”) additives. Representative UVA additives include benzotriazole types such as TINUVIN 326 (trademark) and TINUVIN 328 (trademark) commercially available from Ciba, Inc. Blends of HAL and UVA additives are also effective.

[0056] The antioxidant may include tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydro-cinnamate)]methane; bis[(beta-(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 thiodiethylene bis(3,5-di-tert-butyl-4-hydroxy)-hydrocinnamate; phosphites and phosphonites such as tris(2,4-di-tert-butylphenyl)phosphite and di-tert-butylphenyl-phosphonite; thio compounds such as dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiodipropionate; various siloxanes, polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, n,n'-bis(1,4-dimethylpentyl-p-phenylenediamine), alkylated diphenylamine, 4,4'-bis(alpha,alpha-dimethylbenzyl)diphenylamine, diphenyl-p-phenylenediamine, mixed di-aryl-p-phenylenediamine and other hindered phenols, as well as other hindered amine degradation inhibitors or stabilizers.

[0057] The processing aid 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; aliphatic amides such as stearamide, oleamide, erucamide, or Ν,Ν'-ethylenebis-stearamide; polyethylene wax; oxidized polyethylene wax; polymers of ethylene oxide; copolymers of ethylene oxide and propylene oxide; vegetable waxes; petroleum waxes; nonionic surfactants; silicone fluids and polysiloxanes.

[0058] Formulation The polymer composition can be added to a batch or continuous mixer for melt blending. The components can be blended with other components in any order, or one or more masterbatches can be prepared first and then added. The melt blending can be carried out at a temperature higher than the highest melting point polymer but lower than the maximum compounding temperature of 285°C. The melt-blended composition is delivered to an extruder or an injection molding machine, or is formed into a desired article by passing through a die, or is converted into pellets, tapes, strips or films, or other forms for storage or preparation of materials for the next molding or processing step. Optionally, when formed into pellets or some similar configuration, the pellets etc. can be coated with an anti-sticking agent to facilitate handling during storage.

[0059] Examples of compounding devices that can be used include internal batch mixers, continuous single-screw or twin-screw mixers, or kneading continuous extruders. The type of mixer used and the operating conditions of the mixer affect the properties of the composition such as viscosity, volume resistivity, and extruded surface smoothness.

[0060] The polymer composition can exhibit a flexural modulus in the range of 1,500 to 2,400 megapascals ("MPa"), 1,550 to 2,350 MPa, or 1,600 to 2,000 MPa. The flexural modulus is determined according to the procedure described in the following test method section. The polymer composition can exhibit a maximum tensile stress in the range of 35 to 50 MPa or 35 to 45 MPa. The maximum tensile stress is determined according to the procedure described in the following test method section.

[0061] In various embodiments, particularly in embodiments where the polymer composition is intended for use in a buffer tube containing a hydrocarbon filling compound, the polymer composition may exhibit a weight gain of less than 3 wt%, less than 2 wt%, less than 1 wt%, or less than 0.5 wt% when immersed in INFOGEL LA 444 (trademark) (optical fiber cable buffer tube filling compound). INFOGEL LA 444 (trademark) is composed of at least about 70 wt% mineral oil and up to about 10 wt% styrene-butadiene-styrene block copolymer and is commercially available from Honghui Corp. (China).

[0062] The polymer composition may exhibit a melt index of 4 to 11 g / 10 min at 250 °C and 2.16 Kg. For example, the melt flow index may be 4 g / 10 min or more, or 4.5 / 10 min or more, or 5 g / 10 min or more, or 5.5 / 10 min or more, or 6 g / 10 min or more, or 6.5 g / 10 min or more, or 7 g / 10 min or more, or 7.5 g / 10 min or more, or 8 g / 10 min or more, or 8.5 g / 10 min or more, or 9 g / 10 min or more, or 9.5 g / 10 min or more, or 10 g / 10 min or more, or 10.5 g / 10 min or more, while at the same time being 11 g / 10 min or less, or 10.5 g / 10 min or less, or 10 g / 10 min or less, or 9.5 g / 10 min or less, or 9 g / 10 min or less, or 8.5 g / 10 min or less, or 8 g / 10 min or less, or 7.5 g / 10 min or less, or 7 g / 10 min or less, or 6.5 g / 10 min or less, or 6 g / 10 min or less, or 5.5 g / 10 min or less, or 5 g / 10 min or less, or 4.5 g / 10 min or less.

[0063] The polymer composition may exhibit a zero-shear viscosity of 200 Pa·s or more, or 500 Pa·s or more, or 1,000 Pa·s or more, or 5,000 Pa·s or more, or 10,000 Pa·s or more, or 15,000 Pa·s or more, or 20,000 Pa·s or more, or 25,000 Pa·s or more at 250 °C, while simultaneously being 30,000 Pa·s or less, or 25,000 Pa·s or less, or 20,000 Pa·s or less, or 15,000 Pa·s or less, or 10,000 Pa·s or less, or 5,000 Pa·s or less, or 1,000 Pa·s or less, or 500 Pa·s or less. The test method for zero-shear viscosity will be detailed below.

[0064] The polymer composition may exhibit a breaking stress of 25 MPa or more, or 26 MPa or more, or 27 MPa or more, or 28 MPa or more, or 29 MPa or more, or 30 MPa or more, or 31 MPa or more, or 32 MPa or more, or 33 MPa or more, or 34 MPa or more, or 35 MPa or more, or 36 MPa or more, or 37 MPa or more, or 38 MPa or more, or 39 MPa or more, or 40 MPa or more, or 41 MPa or more, or 42 MPa or more, or 43 MPa or more, or 44 MPa or more, while simultaneously being 45 MPa or less, or 44 MPa or less, or 43 MPa or less, or 42 MPa or less, or 41 MPa or less, or 40 MPa or less, or 39 MPa or less, or 38 MPa or less, or 37 MPa or less, or 36 MPa or less, or 35 MPa or less, or 34 MPa or less, or 33 MPa or less, or 32 MPa or less, or 31 MPa or less, or 30 MPa or less, or 29 MPa or less, or 28 MPa or less, or 27 MPa or less, or 26 MPa or less.

[0065] The polymer composition may exhibit a flexural modulus of 1,000 MPa or more, or 1,100 MPa or more, or 1,200 MPa or more, or 1,300 MPa or more, or 1,400 MPa or more, or 1,500 MPa or more, or 1,600 MPa or more, or 1,700 MPa or more, or 1,800 MPa or more, or 1,900 MPa or more, or 2,000 MPa or more, or 2,100 MPa or more, or 2,200 MPa or more, or 2,300 MPa or more, or 2,400 MPa or more, or 2,500 MPa or more, or 2,600 MPa or more, or 2,700 MPa or more, or 2,800 MPa or more, or 2,900 MPa or more, while simultaneously being 3,000 MPa or less, or 2,900 MPa or less, or 2,800 MPa or less, or 2,700 MPa or less, or 2,600 MPa or less, or 2,500 MPa or less, or 2,400 MPa or less, or 2,300 MPa or less, or 2,200 MPa or less, or 2,100 MPa or less, or 2,000 MPa or less, or 1,900 MPa or less, or 1,800 MPa or less, or 1,700 MPa or less, or 1,600 MPa or less, or 1,500 MPa or less, or 1,400 MPa or less, or 1,300 MPa or less, or 1,200 MPa or less, or 1,100 MPa or less.

[0066] The polymer composition can exhibit a tube crush strength of 55 MPa or more, or 56 MPa or more, or 57 MPa or more, or 58 MPa or more, or 59 MPa or more, or 60 MPa or more, or 61 MPa or more, or 62 MPa or more, or 63 MPa or more, or 64 MPa or more, or 65 MPa or more, or 66 MPa or more, or 67 MPa or more, or 68 MPa or more, or 69 MPa or more, or 70 MPa or more, or 71 MPa or more, or 72 MPa or more, or 73 MPa or more, or 74 MPa or more, while simultaneously 75 MPa or less, or 74 MPa or less, or 73 MPa or less, or 72 MPa or less, or 71 MPa or less, or 70 MPa or less, or 69 MPa or less, or 68 MPa or less, or 67 MPa or less, or 66 MPa or less, or 65 MPa or less, or 64 MPa or less, or 63 MPa or less, or 62 MPa or less, or 61 MPa or less, or 60 MPa or less, or 59 MPa or less, or 58 MPa or less, or 57 MPa or less, or 56 MPa or less.

[0067] Optical fiber cable Referring now to FIG. 1, a cross-sectional view of an exemplary optical fiber cable 1 is shown. In the illustrated example, the optical fiber cable 1 is of a "loose buffer tube" design. In such a cable design, the buffer tubes 2 are radially positioned around the central strength member 4 with a helical rotation about the buffer tubes 2 along the axial length of the optical fiber 1. The helical rotation of the buffer tubes 2 allows the cable to be bent without significantly stretching the tubes or the optical fiber 6. If it is necessary to reduce the number of buffer tubes 2, a foamed filler rod can be used as a spacer to occupy the position 10 of one or more buffer tubes to maintain the shape of the cable 1. The cable jacket 14 is generally made from a polyethylene-based material. The buffer tube 2 can comprise, consist of, or consist essentially of a polymer composition. Thus, the buffer tube 2 can be a polymer tube. The buffer tube 2 is optionally filled with an optical cable grease or gel 8. The gel and grease compounds can include hydrocarbon-based greases incorporating hydrocarbon oils and / or polymer-based greases using low-viscosity polymers compounded with hydrocarbon oils. These greases and gels provide the suspension and protection required in the surrounding environment surrounding the optical fiber 6, including the exclusion of airspace. The gel and grease also provide a barrier against the penetration of water that can adversely affect the performance of the optical fiber 6.

[0068] The buffer tube 2 comprising, consisting of, or consisting essentially of a polymer composition can be advantageous for various reasons. First, since the polymer is resistant to kinking, the possibility of damage to the optical fiber 1 is reduced. Second, since a relatively lower cost injection molding grade of PBT can be utilized, the cost associated with the buffer tube 2 is reduced.

Example

[0069] Materials The following materials are used in the following examples.

[0070] PBT has a viscosity of 1.30 g / cm at 250°C. 3 and a melt index of 33.5 g / 10 min (i.e., injection molding grade) PBT, available commercially as CRASTIN 6134™ from DuPont, Wilmington, Delaware, USA.

[0071] LDPE is 0.921g / cm 3 and a melt index of 1.9 g / 10 min and is commercially available as DXM-446™ from The Dow Chemical Company, Midland, Mich., USA.

[0072] HDPE has a viscosity of 0.955 g / cm at 190°C. 3 and a melt index (I2) of 1.5 g / 10 min and is commercially available as DMDC-1250 NT™ from The Dow Chemical Company (Midland, Mich., USA).

[0073] MAH-HDPE is 0.958g / cm 3 A maleic anhydride grafted HDPE having a density of 1.0 g / 10 min, a melt index of 2.0 g / 10 min, and a maleic anhydride content of greater than 1.0 wt. % and is commercially available as AMPLIFY TY 1053H™ from The Dow Chemical Company, Midland, Mich., USA.

[0074] ENBAGMA1 has a viscosity of 0.94 g / cm at 190°C. 3 and 5% by weight of glycidyl methacrylate by weight of ENBAGMA1, having a density of 1.0 g / 10 min, a melt index of 12 g / 10 min, and is commercially available as Elvaloy PTW™ from The Dow Chemical Company (Midland, Mich., USA).

[0075] ENBAGMA2 is 0.94 g / cm at 190°C. 3 and 9% by weight of glycidyl methacrylate by weight of ENBAGMA2, having a density of 1000 mg / g, a melt index of 8 g / 10 min, and is commercially available as Elvaloy 4170™ from The Dow Chemical Company (Midland, Mich., USA).

[0076] NA-11A is a nucleating agent with the chemical name sodium 2,2'-methylene-bis-(4,6-di-tert-butylphenyl)phosphate (CAS number 85209-91-2) and is commercially available from ADEKA Corporation (Tokyo, Japan).

[0077] AO1 is a sterically hindered phenolic antioxidant with the chemical name pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and is commercially available as IRGANOX 1010™ from BASF (Ludwigshafen, Germany).

[0078] AO2 is a hydrolytically stable phosphite treatment stabilizer having the chemical name tris(2,4-ditert-butylphenyl)phosphite and is commercially available as IRGAFOS 168 from BASF, Ludwigshafen, Germany.

[0079] Tube sample preparation Coated wire extrusion is performed to prepare inventive and comparative examples. The coated wire extrusion models both the buffer tube dimensions and tests the extrusion performance of the polymer composition. Coated wire extrusion is performed using a BRABENDER Mini wireline with 14 gauge copper wire. The BRABENDER Mini wireline settings are shown in Table 1. [Table 1]

[0080] The invention examples and comparative examples have a final diameter of approximately 2.9 mm (0.114 inches) and a wall thickness of approximately 0.635 mm (25 mils) on a 14 American wire gauge solid copper conductor with a diameter of 1.63 mm (0.064 inches). The conductor is pulled from the wire, leaving the tubes of the invention examples and comparative examples. Mechanical tests are performed on the tubes.

[0081] Test Methods The following test methods are used to determine the properties of the materials and the following invention examples and comparative examples.

[0082] Density Unless otherwise specified, the polymer density is determined at 23 °C according to ASTM D792.

[0083] Tensile Strength The tube is cut to a length of 10.16 cm. The tube is clamped in an INSTRON 4202 tensile test unit with a 2.54 cm jaw spacing equipped with a 100-pound load cell. The crosshead speed is set to 5.08 cm / min, and the stress at the tensile break point of the tube is measured. Repeat 5 times and take the average.

[0084] Flexural Modulus Rectangular samples of 1.27 cm width × 7.62 cm length × 0.0127 cm thickness are die-cut from compression-molded plaques. The samples are placed in the flex fixture of an INSTRON 4202 tester, and three-point deflection is performed using a 5.08 cm span and a crosshead speed of 0.127 cm / min. The flexural modulus at the maximum flexural stress that persists during the test is determined.

[0085] Kink Tube sample 1 is completely wrapped around a 6 mm mandrel and held at 23 °C for 10 seconds. The kink formed is observed.

[0086] Tube Crush Place the tube on the INSTRON 4202 between the upper movable plate (dimensions 50 mm × 100 mm) and the lower fixed plate (dimensions 50 mm × 100 mm) attached to the crosshead. Align the tube with the longer dimension of the plate and move the top plate to just touch the top of the tube. Set the crosshead speed to 0.127 cm / min and record the compressive force at the yield point of the tube.

[0087] Zero shear viscosity Using a RHEOMETRICS SR-200 controlled stress rheometer equipped with 25 mm parallel plates, apply a stress of 300 Pa at 250 °C for 3 minutes. Calculate the zero shear viscosity in the range of data where the measured time rate of change of strain is constant. A recovery time of 15 minutes should be considered.

[0088] Results Table 2 provides the compositions and related mechanical properties of Comparative Examples 1 - 5 ("CE1 - CE5") and Inventive Examples 1 - 10 ("IE1 - IE10"). [Table 2]

[0089] As can be seen from Table 2, when only MAH-g-HDPE or ENBAGMA is present in CE1~CE5, the samples show kinks. CE1 is a proper PBT sample representing conventional buffer tube manufacturing. CE2 and CE5 are samples having the same composition as the inventive examples except that only MAH-g-HDPE is utilized. CE3 and CE4 are samples having the same composition as the inventive examples except that only ENBAGMA is utilized. CE1 provides a greater breaking stress than IE1~IE7, but CE1 shows a severe kink consistent with the experience of the prior art. CE2~CE5 individually incorporate MAH-g-HDPE or ENBAGMA, but due to their unstable morphology, they have lower breaking stress values and larger kinks than IE1~IE7. Kinks are undesirable in buffer tubes because they can impose additional stress (bending stress) on the fibers within the buffer tube.

[0090] As is clear from Table 2, using a combination of MAH-g-HDPE and ENBAGMA as compatibilizers results in (1) a zero-shear strength high enough for extrusion in the inventive examples, (2) no kinks, and (3) a greater breaking stress than in the comparative examples. For example, IE1 has a composition substantially the same as CE2~CE5, but unlike CE2~CE5, it does not show kinks. IE1~IE7 show that the combination of MAH-g-HDPE and ENBAGMA as compatibilizers functions over a wide range of compositions.

[0091] It is important to note that it is not the total amount of the compatibilizer that is the main factor, but the presence of both MAH-g-HDPE and ENBAGMA. For example, both CE4 and CE5 contain the same total amount of compatibilizer (i.e., 5 wt%) as IE1 and IE4~IE7, but unlike IE1 and IE4~IE7, they show kinks. Therefore, the combination of MAH-g-HDPE and ENBAGMA has been demonstrated to yield advantageous and surprising results.

Claims

1. A polymer composition comprising: (a) 10% to 45% by weight of an ethylene-based polymer; (b) 50% to 86% by weight of polybutylene terephthalate having a melt flow index of 21 g / 10 min to 35 g / 10 min at 250 °C and 2.16 kg; (c) 3.5% to 10% by weight of a compatibilizer comprising maleated ethylene-based polymer and ethylene n-butyl acrylate glycidyl methacrylate; wherein the ethylene-based polymer consists of low density polyethylene and high density polyethylene, and further, the low density polyethylene is 5% by weight or more of the polymer composition, and the high density polyethylene is 5% by weight or more of the polymer composition.

2. The polymer composition according to claim 1, wherein the polymer composition comprises 10% to 30% by weight of an ethylene-based polymer and 60% to 86% by weight of polybutylene terephthalate.

3. The polymer composition according to claim 1, wherein the maleated ethylene-based polymer has a density of 0.958 g / cm ３ .

4. The polymer composition according to claim 1, wherein the ethylene-based polymer comprises low density polyethylene having a density of 0.921 g / cm ３ and high density polyethylene having a density of 0.955 g / cm ３ .

5. The polymer composition according to claim 1, wherein the polymer composition comprises 4% to 10% by weight of the compatibilizer.

6. The polymer composition according to any one of claims 1 to 5, wherein the polymer composition comprises 2.5% to 7.5% by weight of maleated ethylene-based polymer.

7. The polymer composition according to any one of claims 1 to 5, wherein the polymer composition contains 2.5% to 7.5% by weight of ethylene n-butyl acrylate glycidyl methacrylate.

8. An article comprising a polymer tube, wherein the polymer tube contains the polymer composition according to any one of claims 1 to 7.

9. The article according to claim 8, wherein the article is an optical fiber cable, and the polymer tube is a buffer tube of the optical fiber cable.

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