Rotomolding blends including recycled polyethylene

Abstract

Disclosed herein are rotomolding compositions and processes for making the same. The rotomolding composition according to embodiments disclosed herein comprises a polyethylene, a recycled polyethylene composition, and an ethylene-based elastomer. The specific types and amounts of each of the composition has been shown to allow for incorporation of recycled polyethylene compositions in processes such as rotomolding processes with a maintenance or improvement of toughness and other properties.

Description

[0001] ROTOMOLDING BLENDS INCLUDING RECYCLED POLYETHYLENE

[0002] FIELD

[0003] Embodiments of the present disclosure relate to rotomolding compositions including recycled polyethylene compositions, and processes for making the same.

[0004] INTRODUCTION

[0005] Rotational molding or “rotomolding” can be used to form articles (e.g., trash cans, liquid tanks, traffic-safety barriers, canoes and kayaks) from polymers. The rotomolding process generally includes the following steps: (1) a loading step where a polymer can be loaded into a mold that is in the shape of the intended finished item; (2) a heating step where the mold is heated to a molding temperature for the polymer to melt and the mold can be maintained at the molding temperature while being continuously rotated in two perpendicular directions to form an even distribution on the inside of the mold; (3) a cooling step where the mold can be cooled to solidify the polymer, forming solid walls of a molded item; and (4) an extraction step where the mold is opened and the molded article is recovered. Polyethylene is a common polymer used for rotomolding processes and articles due to its versatility in terms of flow and mechanical properties, among other things. For example, polyethylene can be selected for flow properties for coating and consolidation in the mold. In addition, polyethylene can be ground to a powder or formed as micropellets to speed melting and provide more uniform distribution in the mold.

[0006] Given societal and regulatory pressure to reduce plastic waste, manufacturers of polyethylene articles such as articles formed from rotomolding are attempting to incorporate recycled polymers into their products. Recycling polymers and incorporating post recycled polymers into new products presents challenges. Waste is often contaminated, degraded, mixed, or incompatible with other types of materials. Moreover, post recycled polymers can have significantly different properties such as mechanical and optical properties than virgin polymers, which limits their applications and market value. There is a need for innovative technologies that can enhance the compatibility and blendability of recycled polymers and permit the use of recycled polymers without compromising performance.

[0007] Rotomolding presents unique challenges for incorporation of recycled polymers. For instance, in extruded products, a discrete layer of recycled polyethylene can be sequestered between two layers of virgin polyethylene, but rotomolded articles necessitate a homogeneous monolayer structure where any recycled and virgin polyethylene must be blended to form the structure. Furthermore, rotomolding subjects polyethylene to longer heating cycles with lower shear than other forms of molding. The long heat cycles with low shear in the rotomolding process allow impurities and other materials mixed in recycled polymers to phase separate from the polyethylene. Phase separation undesirably results in lower toughness and lower stress-crack resistance of rotomolded articles.

[0008] Accordingly, a rotomolding composition is needed that can incorporate recycled polymers and produce articles that have a good balance of properties, including toughness and stress-crack resistance. SUMMARY

[0009] A first aspect disclosed herein is a rotomolding composition. The rotomolding composition comprises the following: (a) from 50 to 94 wt.% of a polyethylene having a density from 0.910 g / cm3to 0.950 g / cm3and a melt index (f) from 1.0 g / 10 min to 10.0 g / 10 min; (b) from 5 to 40 wt.% of a recycled polyethylene composition comprising from 1 to 25 wt.% propylene-content, based on the total weight of the recycled polyethylene composition; and (c) from 1 to 15 wt.% of an ethylene-based elastomer having a density from 0.850 g / cm3to 0.900 g / cm3and a melt index (f) from 0.5 to 30.0 g / 10 min, wherein weight percentages of components (a), (b) and (c) are based on the total weight of the rotomolding composition.

[0010] A second aspect disclosed herein is a rotomolding process. The rotomolding process comprises the steps of: (a) loading a rotomolding composition into a mold and closing the mold (the “loading step”); (b) heating the mold to a temperature at which the rotomolding composition melts, while rotating the mold on at least two axes to form a coating of the rotomolding composition adhered to an internal surface of the mold (the “heating step”); (d) cooling the mold to solidify the rotomolding composition adhered to the internal surface of the mold to form a molded article (the “cooling step”); and (e) releasing the molded article from the mold (the “extraction step”); wherein the rotomolding composition is in accordance with the first aspect.

[0011] A third aspect of this invention is a molded article that is made by the process of the second aspect of the invention.

[0012] A fourth aspect of the invention is a molded article that comprises the rotomolding composition from the first aspect of the invention.

[0013] DETAILED DESCRIPTION

[0014] Definitions:

[0015] The terms “polyethylene” or “ethylene-based polymer” shall mean polymers comprising a majority amount (>50 mol %) of units which have been derived from ethylene monomer. This includes polyethylene homopolymers and copolymers (meaning units derived from two or more comonomers). The terms “ethylene-based polymer” and “polyethylene” may be used interchangeably. Generally, polyethylene may be produced in gas-phase, fluidized bed reactors, liquid phase slurry process reactors, or liquid phase solution process reactors, using a heterogeneous catalyst system, such as Ziegler-Natta catalyst, a homogeneous catalyst system, comprising Group 4 transition metals and ligand structures such as metallocene, non-metallocene metal-centered, heteroaryl, heterovalent aryloxyether, phosphinimine, and others. Combinations of heterogeneous and / or homogeneous catalysts also may be used in either single reactor or dual reactor configurations. Common forms of polyethylene known in the art include Low Density Polyethylene (LDPE); Linear Low Density Polyethylene (LLDPE); Ultra Low Density Polyethylene (ULDPE); Very Low Density Polyethylene (VLDPE); single-site catalyzed Linear Low Density Polyethylene, including both linear and substantially linear low density resins (m-LLDPE); ethylene -based plastomers (POP) and ethylene-based elastomers (POE); Medium Density Polyethylene (MDPE); and High Density Polyethylene (HDPE).

[0016] The term “ethylene / a-olefin interpolymer” shall mean an ethylene-based polymer comprising at least one alpha-olefin comonomer that is polymerized with ethylene to make the interpolymer. As such, ethylene / a-olefin interpolymers include both copolymers and terpolymers. Alpha-olefin comonomers include C3-C20 alpha-olefins, especially propene, isobutylene, 1 -butene, 1- hexene, 4-methyl-l -pentene, 1- heptene, 1 -octene, 1 -nonene, and 1 -decene, 1 -butene, 1 -hexene, 4-methyl-l -pentene and 1 -octene.

[0017] The term “ethylene-based elastomer” shall mean an ethylene / a-olefin interpolymer that (i) comprise units derived from ethylene and units derived from at least one C3-C10 a-olefin comonomer, or at least one C4-C8 a-olefin comonomer, or at least one C6-C8 a-olefin comonomer; and (ii) has a density from 0.865 g / cm3. or 0.870 g / cm3, or 0.880 g / cm3, or 0.890 g / cm3to 0.900 g / cm3, or 0.902 g / cm3, or 0.904 g / cm3, or 0.909 g / cm3, or 0.910 g / cm3. This includes substantially linear, or linear, ethylene / a- olefin copolymers containing homogeneous short-chain branching distribution and ethylene / a-olefin multiblock copolymers. Nonlimiting examples of ethylene-based elastomers include commercially available plastomers or elastomers such as ENGAGE™ Polyolefin Elastomers, and INFUSE™ Olefin Block Copolymers (available from The Dow Chemical Company), EXACT™ plastomers (available from ExxonMobil Chemical), Tafmer (available from Mitsui), Nexlene™ (available from SK Chemicals Co.), and Lucene™ (available LG Chem Ltd.).

[0018] The term “propylene-content” means weight percent of repeating units in a polymer that are derived from propylene monomer. For clarity, repeating units derived from propylene monomer that are measured in “propylene-content” may be incorporated into polypropylene polymers, or may be comonomers in other polymers such polyethylene, or may be both.

[0019] The polymers described herein are “virgin” polymers, unless the word “recycled” is used in conjunction with the polymer or polymeric composition. “Virgin” polyethylene or polymers are polyethylene or polymers that have not previously been converted or extruded or melted into an article. This is in distinction to a “recycled polyethylene composition” as used herein, which is a polyethylene or polymer that has been exposed to at least one heat history (e.g., via previous extrusion or conversion or melting into an article). Non-limiting examples of recycled polyethylene compositions include Post Consumer Recycled (“PCR”) compositions such as HDPE PCR polyethylene compositions sold under the KW Plastics and RENUVA™ trademarks.

[0020] The term “composition,” as used herein, refers to a mixture of materials that comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0021] The terms “comprising,” “including,” “having,” and their derivatives, are not intended to exclude the presence of any additional component, step or procedure, whether or not the same is specifically disclosed. In order to avoid any doubt, all compositions claimed through use of the term “comprising” may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, “consisting essentially of’ excludes from the scope of any succeeding recitation any other component, step or procedure, excepting those that are not essential to operability. The term “consisting of’ excludes any component, step or procedure not specifically delineated or listed.

[0022] Rotomolding Compositions

[0023] The rotomolding composition according to embodiments disclosed herein comprises: (a) a polyethylene; (b) a recycled polyethylene composition; and (c) an ethylene-based elastomer. The rotomolding compositions is suitable for use in rotomolding, and may also be useful in other fabrication processes, such as blow molding or compression molding.

[0024] In some embodiments, the rotomolding composition has a density of at least 0.910 g / cm3or at least 0.915 g / cm3or at least 0.920 g / cm3or at least 0.925 g / cm3or at least 0.930 g / cm3or at least 0.932 g / cm3or at least 0.935 g / cm3. In some embodiments, the rotomolding composition has a density of at most 0.942 g / cm3or at most 0.940 g / cm3or at most 0.938 g / cm3.

[0025] In some embodiments, the rotomolding composition has a melt index (f) of at least 1.0 g / 10 min or at least 2.0 g / 10 min or at least 3.0 g / 10 min or at least 4.0 g / 10 min or at least 4.3 g / 10 min or at least 4.5 g / 10 min. In some embodiments, the rotomolding composition has a melt index (I2) of at most 9.0 g / 10 min, or at most 8.0 g / 10 min or at most 7.0 g / 10 min or at most 6.0 g / 10 min or at most 5.5 g / 10 min or at most 5.0 g / 10 min or at most 4.8 g / 10 min.

[0026] In some embodiments, the rotomolding composition has a zero shear viscosity (T|O) of at least 2000 Pa*s or at least 2100 Pa*s or at least 2200 Pa*s or at least 2300 Pa*s or at least 2400 Pa*s. In some embodiments, the rotomolding composition has a zero shear viscosity (r|o) of at most 3000 Pa*s, or at most 2800 Pa*s or at most 2600 Pa*s or at most 2500 Pa*s.

[0027] Components of the Rotomolding Composition

[0028] The rotomolding composition comprises a polyethylene, a recycled polyethylene composition, and an ethylene-based elastomer, where each is present in a weight percent (or percentage wt.%) based on the total weight of the rotomolding composition. Polyethylenes and ethylene-based elastomers that are known to be suitable for use in rotomolding compositions are commercially available.

[0029] Polyethylene

[0030] The rotomolding composition comprises a polyethylene having a density from 0.910 g / cm3to 0.950 g / cm3. The polyethylene can be a blend of one or more polymers as long as the polyethylene of the rotomolding composition is in accordance with the embodiments disclosed herein. For instance, if the rotomolding composition comprises a 30 wt.% of a HDPE and 30 wt.% of a MDPE, where the resulting polyethylene in the composition from the HDPE and MDPE has a density from 0.910 g / cm3to 0.950 g / cm3and a melt index (E) from 1.0 g / 10 min to 10.0 g / 10 min, then the polyethylene includes the HDPE and MDPE and includes from 50 to 94 wt.% (i.e., 60 wt.%) of a polyethylene having a density from 0.910 g / cm3to 0.950 g / cm3and a melt index (E) from I.O g / IO min to lO.O g / IO min. This concept or calculation is true with respect to the other components (e.g., the recycled polyethylene composition and ethylenebased elastomer) in the composition and understood by those skilled in the art based on the teachings herein. In some embodiments, the polyethylene has a density of at least 0.910 g / cm3or at least 0.920 g / cm3or at least 0.925 g / cm3or at least 0.930 g / cm3or at least 0.932 g / cm3or at least 0.935 g / cm3. In some embodiments, the polyethylene has a density of at most 0.945 g / cm3or at most 0.943 g / cm3or at most 0.941 g / cm3or at most 0.939 g / cm3or at most 0.937 g / cm3or at most 0.936 g / cm3or at most 0.935 g / cm3. In some embodiments, the polyethylene is an MDPE. In some embodiments, the polyethylene is an LLDPE. In some embodiments, the polyethylene is an HDPE having a density of at least 0.935 to no more than 0.950 g / cm3.

[0031] In some embodiments, the polyethylene has a melt index (I2) of at least 1.0 g / 10 min or at least 2.0 g / 10 min or at least 3.0 g / 10 min or at least 4.0 g / 10 min or at least 4.5 g / 10 min or at least 5.0 g / 10 min or at least 5.3 g / 10 min. In some embodiments, the polyethylene has a melt index (I2) of at most 10.0 g / 10 min, or at most 9.0 g / 10 min or at most 8.0 g / 10 min or at most 7.0 g / 10 min or at most 6.0 g / 10 min or at most 5.8 g / 10 min or at most 5.5 g / 10 min. In some embodiments, that polyethylene has a melt index (I2) of from 3.0 g / 10 min. to 8.0 g / 10 min. or from 4.0 g / 10 min. to 6.0 g / 10 min.

[0032] The rotomolding composition comprises from 50 to 94 wt.% of the polyethylene, wherein weight percent is based on the total weight of the rotomolding composition. In some embodiments, the rotomolding composition comprises at least 55 wt.% polyethylene, or at least 60 wt.% or at least 65 wt.% or at least 67 wt.% or at least 70 wt.% or at least 72 wt.% or at least 75 wt.%. In some embodiments, the rotomolding composition comprises at most 90 wt.% polyethylene, or at most 85 wt.% or at most 83 wt.% or at most 80 wt.% or at most 78 wt.% or at most 76 wt.%.

[0033] Recycled Polyethylene Composition

[0034] The rotomolding composition comprises a recycled polyethylene composition.

[0035] In some embodiments, the recycled polyethylene composition is a recycled HDPE composition or a recycled PCR HDPE. In some embodiments, the recycled polyethylene composition has a density of at least 0.935 g / cm3or at least 0.940 g / cm3or at least 0.942 g / cm3or at least 0.944 g / cm3or at least 0.946 g / cm3. In some embodiments, the recycled polyethylene composition has a density of at most 0.970 g / cm3or at most 0.960 g / cm3or at most 0.955 g / cm3or at most 0.950 g / cm3or at most 0.948 g / cm3. For example, the recycled polyethylene composition can have a density from 0.935 g / cm3to 0.970 g / cm3or from 0.940 g / cm3to 0.960 g / cm3.

[0036] In some embodiments, the recycled polyethylene composition is a recycled MDPE or a recycled LLDPE composition. In some embodiments, the recycled polyethylene composition has a density of at least 0.910 g / cm3or at least 0.915 g / cm3or at least 0.920 g / cm3or at least 0.925 g / cm3. In some embodiments, the recycled polyethylene composition has a density of at most 0.940 g / cm3or at most 0.937 g / cm3or at most 0.935 g / cm3. For example, the recycled polyethylene composition can have density from 0.910 g / cm3to 0.940 g / cm3or from 0.920 g / cm3to 0.935 g / cm3.

[0037] In some embodiments, the recycled polyethylene composition has a melt index (I2) of at least 0.5 g / 10 min or at least 1.0 g / 10 min or at least 1.5 g / 10 min or at least 2.0 g / 10 min or at least 3.0 g / 10 min or at least 3.5 g / 10 min or at least 4.0 g / 10 min. In some embodiments, the recycled polyethylene composition has a melt index (I2) of at most 9.0 g / 10 min, or at most 8.0 g / 10 min, or at most 7.0 g / 10 min, or at most 6.0 g / lO min, or at most 5.0 g / lO min, or at most 4.5 g / lO min. In some embodiments, recycled polyethylene composition has a melt index (I2) from 2.0 g / 10 min. to 7.0 g / 10 min. or from 3.0 g / 10 min. to 6.0 g / 10 min.

[0038] In some embodiments, the recycled polyethylene composition comprises from 1 to 25 wt.% propylene -content, based on the total weight of the recycled polyethylene composition. In some embodiments, the recycled polyethylene composition comprises at least 2 wt.% propylene-content or at least 3 wt.% or at least 5 wt.% or at least 7 wt.% or at least 9 wt.% or at least 10 wt.% or at least 11 wt.% or at least 13 wt.% or at least 15 wt.%. In some embodiments, the recycled polyethylene composition comprises at most 25 wt.% or at most 22 wt.% or at most 20 wt.% or at most 18 wt.% or at most 16 wt.% propylene -content, based on the total weight of the recycled polyethylene composition.

[0039] The rotomolding composition comprises from 5 to 40 wt.% the recycled polyethylene composition, wherein weight percentages is based on the total weight of the recycled polyethylene composition. In some embodiments, the rotomolding composition comprises at least 10 wt.% recylced polyethylene composition, or at least 15 wt.% or at least 18 wt.% or at least 20 wt.% or at least 23 wt.% or at least 25 wt.%. In some embodiments, the rotomolding composition comprises at most 38 wt.% recycled polyethylene composition, or at most 35 wt.% or at most 33 wt.% or at most 30 wt.% or at most 28 wt.% or at most 26 wt.%.

[0040] In some embodiments, the recycled polyethylene composition comprises polypropylene. In some embodiments, the rotomolding composition comprises at least 1 wt.% polypropylene or at least 2 wt.% or at least 3 wt.% or at least 4 wt.% or at least 5 wt.%, based on the total weight of the rotomolding composition. In some embodiments, the rotomolding composition comprises at most 10 wt.% polypropylene or at most 9 wt.% or at most 8 wt.% or at most 7 wt.% or at most 6 wt.%, based on the total weight of the rotomolding composition.

[0041] In some embodiments, the rotomolding composition has a propylene -content of at least 1 wt.% or at least 2 wt.% or at least 3 wt.% or at least 4 wt.% or at least 5 wt.%, based on the total weight of the rotomolding composition. In some embodiments, the rotomolding composition has a propylene-content of at most 10 wt.% polypropylene or at most 9 wt.% or at most 8 wt.% or at most 7 wt.% or at most 6 wt.%, based on the total weight of the rotomolding composition.

[0042] Ethylene -Based Elastomer

[0043] The rotomolding composition comprises from 1 to 15 wt.% of an ethylene-based elastomer having a density from 0.850 g / cm3to 0.900 g / cm3and a melt index (I2) from 0.5 to 30.0 g / 10 min. Without intending to be bound by theory, the ethylene-based elastomer can serve multiple functions in the composition and can serve, for example, to add toughness or as a compatibilizer between polypropylene contaminants in the recycled polyethylene composition and polyethylene, where these functions are important and unique in particular for rotomolding where the process involves different heating, temperature, and mixing parameters than typical extrusion processes.

[0044] In some embodiments, the ethylene -based elastomer is a random copolymer. In some embodiments, the random copolymer ethylene -based elastomer has a density of at most 0.900 g / cm3or at most 0.890 g / cm3or at most 0.885 g / cm3or at most 0.880 g / cm3or at most 0.875 g / cm3. In some embodiments, the random copolymer ethylene -based elastomer has a density of at least 0.854 g / cm3or at least 0.860 g / cm3or at least 0.865 g / cm3or at least 0.870 g / cm3.

[0045] In some embodiments, the random copolymer ethylene-based elastomer has a melt index (I2) of at least 2.0 g / 10 min or at least 3.0 g / 10 min or at least 4.0 g / 10 min or at least 4.5 g / 10 min or at least 5.0 g / 10 min. In some embodiments, the random copolymer ethylene -based elastomer has a melt index (I2) of at most 20.0 g / 10 min, or at most 15.0 g / 10 min, or at most 10.0 g / 10 min, or at most 9.0 g / 10 min, or at most 8.0 g / 10 min, or at most 7.0 g / 10 min, or at most 6.0 g / 10 min, or at most 5.8 g / 10 min, or at most 5.5 g / 10 min. In some embodiments, the random copolymer ethylene -based elastomer has a melt index (I2) of from 3.0 g / 10 min. to 8.0 g / 10 min. or from 4.0 g / 10 min. to 6.0 g / 10 min.

[0046] In some embodiments, the random copolymer ethylene-based elastomer has a weight average molecular weight (Mw) of at least 50,000 g / mol, or at least 65,000 g / mol or at least 68,000 g / mol or at least 70,000 g / mol or at least 72,000 g / mol or at least 74,000 g / mol. In some embodiments, the random copolymer ethylene-based elastomer has a weight average molecular weight (Mw) of at most 100,000 g / mol, or at most 85,000 g / mol or at most 80,000 g / mol or at most 78,000 g / mol or at most 76,000 g / mol or at most 75,000 g / mol.

[0047] In some embodiments, the random ethylene-based elastomer has a number average molecular weight (Mn) of at least 25,000 g / mol, or at least 26,000 g / mol or at least 27,000 g / mol or at least 28,000 g / mol or at least 29,000 g / mol or at least 31,000 g / mol. In some embodiments, the random ethylene-based elastomer has a number average molecular weight (Mn) of at most 50,000 g / mol, or at most 38,000 g / mol or at most 36,000 g / mol or at most 34,000 g / mol or at most 33,000 g / mol or at most 32,000 g / mol.

[0048] In some embodiments, the random ethylene-based elastomer has a polydispersity index (Mw / Mn) of at least 1.5, or at least 1.7 or at least 1.9 or at least 2.0 or at least 2.1 or at least 2.2. In some embodiments, the random ethylene -based elastomer has a polydispersity index (Mw / Mn) of at most 4, or at most 3.5 or at most 3.0 or at most 2.8 or at most 2.6 or at most 2.4.

[0049] In some embodiments, the ethylene-based elastomer is an ethylene / a-olefin multi-block interpolymer (“multi -block interpolymer”). A multi -block interpolymer comprises “hard” and “soft” segments.

[0050] “Hard” segments are blocks of polymerized units in which ethylene is present in an amount greater than 94 weight percent, or greater than 98 weight percent based on the weight of the hard blocks in the polymer, up to 100 weight percent. In other words, the comonomer content (content of monomers other than ethylene) in the hard segments is less than 6 weight percent, or less than 2 weight percent based on the weight of the hard blocks in the polymer, and can be as low as zero. In some embodiments, the hard segments include all, or substantially all, units derived from ethylene.

[0051] “Soft” segments are blocks of polymerized units in which the comonomer content (content of monomers other than ethylene) is greater than 5 weight percent, or greater than 8 weight percent, greater than 10 weight percent, or greater than 15 weight percent based on the weight of the soft blocks in the polymer. In some embodiments, the comonomer content in the soft segments can be greater than 20 weight percent, greater than 25 weight percent, greater than 30 weight percent, greater than 35 weight percent, greater than 40 weight percent, greater than 45 weight percent, greater than 50 weight percent, or greater than 60 weight percent and can be up to 100 weight percent.

[0052] The soft segments can be present in the multi-block interpolymer from 1 weight percent to 99 weight percent of the total weight of the multi-block interpolymer, or from 5 weight percent to 95 weight percent, from 10 weight percent to 90 weight percent, from 15 weight percent to 85 weight percent, from 20 weight percent to 80 weight percent, from 25 weight percent to 75 weight percent, from 30 weight percent to 70 weight percent, from 35 weight percent to 65 weight percent, from 40 weight percent to 60 weight percent, or from 45 weight percent to 55 weight percent of the total weight of the multi -block interpolymer. Conversely, the hard segments can be present in similar ranges. The soft segment weight percentage and the hard segment weight percentage can be calculated from DSC or NMR. Such methods and calculations are disclosed in, for example, USP 7,608,668, the disclosure of which is incorporated by reference herein, in its entirety. For example, the hard segment and the soft segment weight percentages may be determined as described in column 57 to column 63 of U.S. Patent 7,608,668, incorporated herein by reference.

[0053] In some embodiments, the multi -block interpolymer has a density of at most 0.910 g / cm3or at most 0.900 g / cm3or at most 0.890 g / cm3or at most 0.885 g / cm3or at most 0.883 g / cm3or at most 0.881 g / cm3or at most 0.879 g / cm3. In some embodiments, the multi-block interpolymer has a density of at least 0.854 g / cm3or at least 0.860 g / cm3or at least 0.865 g / cm3or at least 0.870 g / cm3or at least 0.875 g / cm3.

[0054] In some embodiments, the multi-block interpolymer has a melt index (I2) of at least 2.0 g / 10 min. or at least 3.0 g / 10 min. or at least 4.0 g / 10 min or at least 4.5 g / 10 min. or at least 5.0 g / 10 min. In some embodiments, the melt index (I2) of the multi-block interpolymer is at most 9.0 g / 10 min, or at most 8.0 g / 10 min. or at most 7.0 g / 10 min. or at most 6.0 g / 10 min. or at most 5.8 g / 10 min. or at most 5.5 g / 10 min. In some embodiments, the melt index (I2) of the multi-block interpolymer is from 3.0 g / 10 min. to 8.0 g / 10 min. or from 4.0 g / 10 min. to 6.0 g / 10 min.

[0055] In some embodiments, the multi-block interpolymer has a weight average molecular weight (Mw) of at least 50,000 g / mol, or at least 75,000 g / mol or at least 78,000 g / mol or at least 80,000 g / mol or at least 82,000 g / mol or at least 84,000 g / mol. In some embodiments, the multi-block interpolymer has a weight average molecular weight (Mw) of at most 100,000 g / mol, or at most 95,000 g / mol or at most 90,000 g / mol or at most 88,000 g / mol or at most 86,000 g / mol or at most 85,000 g / mol.

[0056] In some embodiments, the multi-block interpolymer has a number average molecular weight (Mn) of at least 25,000 g / mol, or at least 28,000 g / mol or at least 29,000 g / mol or at least 30,000 g / mol or at least 31,000 g / mol or at least 32,000 g / mol. In some embodiments, the multi-block interpolymer has a number average molecular weight (Mn) of at most 50,000 g / mol, or at most 40,000 g / mol or at most 38,000 g / mol or at most 36,000 g / mol or at most 35,000 g / mol or at most 34,000 g / mol. In some embodiments, the multi-block interpolymer has a polydispersity index (Mw / Mn) of at least 1.7, or at least 1.8 or at least 2.0 or at least 2.2 or at least 2.3 or at least 2.4 or at least 2.5. In some embodiments, the multi -block interpolymer has a polydispersity index (Mw / Mn) of at most 8.0, or at most 6.0 or at most 4.0 or at most 3.5 or at most 3.0 or at most 2.8 or at most 2.7.

[0057] In some embodiments, the rotomolding composition comprises at least 2 wt.% of the ethylenebased elastomer or at least 3 wt.% or at least 4 wt.% or at least 5 wt.% or at least 6 wt.% or at least 7 wt.%, wherein weight percentages are based on the total weight of polymers in the rotomolding composition. In some embodiments, the rotomolding composition comprises at most 14 wt.% of the ethylene-based elastomer or at most 13 wt.% or at most 12 wt.% or at most 11 wt.% or at most 10 wt.% or at most 9 wt.% or at most 8 wt.% or at most 7 wt.% or at most 6 wt.%.

[0058] Additives

[0059] In some embodiments, the rotomolding composition further comprises additives. Additives for polyethylene polymers are well known and commercially-available. Examples of common additives include densification aids, heat stabilizers, primary and secondary antioxidants, light stabilizers, acid scavengers, processing aids (such as lubricants, rheology control agents, mold release agents, antiblock additives and slip agents), antistatic additives, flame retardants, pigments and fdlers. In some embodiments, the rotomolding composition contains at least 750 ppm heat stabilizer or at least 850 ppm or at least 900 ppm or at least 950 ppm or at least 1000 ppm. In some embodiments, the rotomolding composition contains both the heat stabilizer as previously described plus primary antioxidant.

[0060] Preparation of the Rotomolding Composition

[0061] Rotomolding compositions are typically in the form of powders or micropellets when they are used in the rotomolding process.

[0062] Micropellets can be made by extruding the components of the rotomolding composition using known equipment. In some embodiments, the micropellets have an average particle size less than 1000 microns or no more than 800 microns or no more than 700 microns or no more than 600 microns. In some embodiments, the micropellets have an average particle size of at least 300 microns or at least 400 microns or at least 500 microns.

[0063] Powders can be made by grinding or pulverizing pellets of the components. Common grinders and pulverizers that may be useful to make the powders include jaw crushers, crushing rollers, ball mills, rod mills, tube mills, pin / peg mills and hammer mills.

[0064] Optimal powder sizes for the rotomolding composition may vary depending on the equipment and processes used for grinding and rotomolding. In some cases, median particle sizes are no more than 28 mesh (600 microns) or 35 mesh (500 microns) or 45 mesh (350 microns). In some cases, median particle sizes are at least 140 mesh (100 microns) or at least 100 mesh (150 microns) or at least 60 mesh (250 microns) or at least 50 mesh (300 microns).

[0065] In some embodiments, components of the rotomolding composition are separately extruded to make micropellets, and the micropellets are blended together to make the rotomolding composition. In some embodiments, components of the rotomolding composition are separately ground or pulverized to make powders, and the powders are blended together to make the rotomolding composition.

[0066] In some embodiments, two or more components of the rotomolding composition are blended and extruded as micropellets. In some embodiments, two or more components of the rotomolding composition are blended and extruded to make pellets of the blend; the pellets may be ground or pulverized later to make a blended powder. Any remaining components of the rotomolding composition can be added to the powder or micropellets.

[0067] In a first example, the polyethylene, the recycled polyethylene composition and the ethylene-based elastomer components of the rotomolding composition are coextruded to make pellets or micropellets, optionally with some additives such as the heat stabilizer. Pellets are later converted to powders for use. Further additives, such as colorants, may optionally be added to the rotomolding composition micropellets or powder by physical blending when it is used.

[0068] In a second example, the polyethylene and the ethylene -based elastomer components of the rotomolding composition are coextruded to make pellets or micropellets, optionally with additional additives. Pellets are later converted to powders for use. Powders or micropellets of the recycled polyethylene composition, optionally with further additives, can be added to the rotomolding composition by physical blending when it is used.

[0069] Rotomolding Process and Product

[0070] The rotomolding composition may be used in an ordinary rotomolding process, which comprises the steps of: a) loading the rotomolding composition into a mold and closing the mold (the “loading step”); b) heating the mold to a temperature at which the polymer melts, while rotating the mold on at least two axes to form a coating of the rotomolding composition adhered to the internal surface of the mold (the “heating step”); c) cooling the mold to solidify the rotomolding composition adhered to the internal surface of the mold (the “cooling step”); and d) releasing the molded article from the mold (the “extraction step”).

[0071] Suitable rotational molding equipment to perform these steps and operating instructions to use the equipment are known and commercially available.

[0072] Rotational molding produces hollow articles. Therefore, the amount of rotomolding composition loaded into the mold in the loading step may be less than is needed to entirely fdl the mold. In some embodiments, the amount of rotomolding composition loaded into the mold is sufficient to produce molded articles having an average wall thickness of at least 1.0 mm or at least 1.5 mm or at least 2.0 mm or at least 3.0 mm. In some embodiments, the amount of rotomolding composition loaded into the mold is sufficient to produce molded articles having an average wall thickness of at most 50 mm or at least most 40 mm or at most 30 mm or at most 25 mm. The closed mold typically comprises a vent to allow air to escape during the heating step. The vent usually protrudes into the center of the mold, so that molten and powdered rotomolding composition does not come out of the vent as the mold rotates.

[0073] The temperature of rotomolding is frequently measured as “peak internal air temperature,” which is the maximum temperature achieved in the air space at the center of the mold. In some embodiments, the peak internal air temperature (PIAT) achieved in the heating and cooling step is at least 160°C or at least 165°C or at least 170°C or at least 180°C. In some embodiments, the peak internal air temperature (PIAT) achieved in the heating and cooling step is at most 220°C or at most 220°C or at most 210°C or at most 200°C or at most 190°C.

[0074] The heated mold is rotated on at least two axes, so that the rotomolding composition can contact all internal surfaces of the mold. In some embodiments, the axes of rotation are substantially perpendicular to each other. In some embodiments the rotation speed is at least 1 rpm or at least 3 rpm or at least 5 rpm. In some embodiments, the rotation speed is at most 40 rpm or at most 30 rpm or at most 20 rpm. Rotation in both axes is not necessarily the same speed. Depending on the shape of the mold, it may be desirable to rotate the longer axis at a speed faster or slower than the shorter axis.

[0075] The time of the heating step varies depending on the equipment and the item being made. In most embodiments, it is desirable to maintain the heating step until the rotomolding composition coalesces to form a molded article. In some embodiments, times of 5 to 40 minutes are used.

[0076] After the heating step, the mold is cooled in the cooling step. Cooling may be speeded by blowing cool air on the mold or spraying cooling water on the mold or both. In most embodiments, the cooling step is maintained until the molded article solidifies enough to maintain its shape outside the mold. In some embodiments, the mold is cooled to a temperature below the Vicat softening temperature of the rotomolding composition. In some embodiments, the mold is cooled to atemperature ofatmost 110°C or at most 100°C or at most 90°C or at most 80°C.

[0077] When the mold reaches the desired temperature, the mold is opened, and the molded article is recovered in the extraction step.

[0078] The resulting molded article has walls that comprise the rotomolding composition of this invention, which has coalesced from powder or micropellets to solid walls. Embodiments of the thickness of the walls are as previously described.

[0079] In some embodiments, 5 inch by 5 inch plaques made by rotomolding the rotomolding composition have an ARM Impact Strength (at 40°C) of at least 200 Ib-ft / in. thickness, or at least 240 Ib-ft / in. or at least 280 Ib-ft / in. or at least 320 Ib-ft / in. or at least 360 Ib-ft / in. or at least 400 Ib-ft / in. or at least 440 Ib-ft / in. In some embodiments, the rotomolded plaques have a thickness of 0. 125 inches.

[0080] The rotomolding composition may also be formed into shaped articles by other processes, such as extrusion, blow molding or compression molding. In some embodiments, compression-molded plaques made from the rotomolding composition according to the Test Methods have an Elongation to Break of at least 700% or at least 750% or at least 800% or at least 840% or at least 900% or at least 910% or at least 920% or at least 950%. In some embodiments, compression-molded plaques made from the rotomolding composition according to the Test Methods have an Elongation to Break of at most 1200% or at most 1100% or at most 1000% or at most 960%.

[0081] In some embodiments, compression-molded plaques made from the rotomolding composition according to the Test Methods have a Charpy Impact Strength of at least 2.5 kJ / m2or at least 2.9 kJ / m2or at least 3.0 kJ / m2or at least 3. 1 kJ / m2.

[0082] In some embodiments, compression-molded plaques made from the rotomolding composition according to the Test Methods have a Secant Modulus (1%) of at least 80 ksi or at least 85 ksi or at least 90 ksi or at least 95 ksi or at least 97 ksi or at least 100 ksi. In some embodiments, plaques made from the rotomolding composition according to the Test Methods have a Secant Modulus (1%) of at most 120 ksi or at most 110 ksi or at most 105 ksi.

[0083] In some embodiments, compression-molded plaques made from the rotomolding composition according to the Test Methods have an Environmental Stress Crack Resistance (ESCR) of at least 200 hours or at least 350 hours or at least 400 hours or at least 500 hours or at least 600 hours or at least 700 hours or at least 750 hours or at least 800 hours or at least 900 hours or at least 1000 hours.

[0084] ASPECTS -

[0085] Aspect 1 - A rotomolding composition comprising the following:

[0086] (a) from 50 to 94 wt.% of a polyethylene having a density from 0.910 g / cm3to 0.950 g / cm3and a melt index (E) from 1.0 g / 10 min to 10.0 g / 10 min;

[0087] (b) from 5 to 40 wt.% of a recycled polyethylene composition comprising from 1 to 25 wt.% propylene -content, based on the total weight of the recycled polyethylene composition; and

[0088] (c) from 1 to 15 wt.% of an ethylene-based elastomer having a density from 0.850 g / cm3to 0.900 g / cm3and a melt index (E) from 0.5 to 30.0 g / 10 min, wherein weight percentages of components (a), (b) and (c) are based on the total weight of the rotomolding composition.

[0089] Aspect 2 - The rotomolding composition of aspect 1, wherein the rotomolding composition comprises from 60 to 80 wt.% of the polyethylene and wherein the polyethylene has a density from 0.925 g / cm3to 0.939 g / cm3and a melt index (I2) from 3.0 g / 10 min to 8.0 g / 10 min.

[0090] Aspect 3- The rotomolding composition of any one of the preceding aspects, wherein the recycled polyethylene composition has a density from 0.940 g / cm3to 0.960 g / cm3, a melt index (I2) from 0.5 g / 10 min. to 8.0 g / 10 min; and a propylene content from 10 to 20 wt.%, based on the total weight of the recycled polyethylene composition.

[0091] Aspect 3 - The rotomolding composition of any one of the preceding aspects, wherein the rotomolding composition comprises from 15 to 30 wt.% of recycled polyethylene composition, based on the total weight of the rotomolding composition. Aspect 4 - The rotomolding composition of any one of the preceding aspects, wherein the recycled polyethylene composition has a density from 0.910 g / cm3to 0.940 g / cm3; a melt index (I2) from 0.5 g / 10 min. to 8.0 g / 10 min; and a propylene content from 10 to 20 wt.%, based on the total weight of the rotomolding composition.

[0092] Aspect 5 - The rotomolding composition of any one of the preceding aspects, wherein the ethylene-based elastomer has a density from 0.860 g / cm3to 0.900 g / cm3and a melt index (I2) from 3.0 g / 10 min. to 8.0 g / 10 min.

[0093] Aspect 6 - The rotomolding composition any one of the preceding aspects, wherein the rotomolding composition comprises from 2 to 12 wt.% of the ethylene-based elastomer, wherein weight percentages are based on the total weight of the rotomolding composition.

[0094] Aspect 7 - The rotomolding composition of any one of the preceding aspects, wherein the ethylene-based elastomer is a random copolymer.

[0095] Aspect 8 - The rotomolding composition of any one of the preceding aspects, wherein the rotomolding composition comprises from 60 to 80 wt.% of the polyethylene and from 15 to 30 wt.% of the recycled polyethylene composition, based on the total weight of the rotomolding composition, and wherein the polyethylene has a density from 0.925 g / cm3to 0.939 g / cm3and a melt index (I2) from 3.0 g / 10 min. to 8.0 g / 10 min; and the recycled polyethylene composition has a density from 0.940 g / cm3to 0.960 g / cm3; a melt index (I2) from 0.5 g / 10 min. to 8.0 g / 10 min; a propylene -content from 2 to 8 wt.%, based on the total weight of the recycled polyethylene composition.

[0096] Aspect 9 - The rotomolding composition of any one of aspects 1-7, 9, wherein the ethylene-based elastomer is an ethylene / a-olefin multi-block interpolymer.

[0097] Aspect 10 - The rotomolding composition of any one of the preceding aspects, wherein the rotomolding composition comprises from 60 to 80 wt.% of the polyethylene and from 15 to 30 wt.% recycled polyethylene composition, based on the total weight of the rotomolding composition, and wherein the polyethylene has a density from 0.925 g / cm3to 0.939 g / cm3and a melt index (I2) from 3.0 g / 10 min to 8.0 g / 10 min, and the recycled polyethylene composition has a density from 0.940 g / cm3to 0.960 g / cm3, a melt index (I2) from 0.5 g / 10 min. to 8.0 g / 10 min, and a propylene content from 2 to 8 wt.%.

[0098] Aspect 11 - The rotomolding composition any one of the preceding aspects, wherein the rotomolding composition has a density from 0.925 g / cm3to 0.940 g / cm3.

[0099] Aspect 12 - The rotomolding composition of any one of the preceding aspects, wherein the rotomolding composition has a melt index (I2) from 3.0 g / 10 min. to 8.0 g / 10 min.

[0100] Aspect 13 - The rotomolding composition of any of one of the preceding aspects, wherein the rotomolding composition is in the form of powder having a median particle size from 100 microns to less than 1000 microns.

[0101] Aspect 14 - A rotomolding process comprising the steps of: (a) loading a rotomolding composition into a mold and closing the mold (the “loading step”); (b) heating the mold to a temperature at which the rotomolding composition melts, while rotating the mold on at least two axes to form a coating of the rotomolding composition adhered to an internal surface of the mold (the “heating step”); (c) cooling the mold to solidify the rotomolding composition adhered to the internal surface of the mold to form a molded article (the “cooling step”); and (d) releasing the molded article from the mold (the “extraction step”); wherein the rotomolding composition is in accordance with any one of the preceding claims.

[0102] Test Methods

[0103] Unless stated otherwise, measurements listed in this application are made using the following test methods: Zero Shear Viscosity (no) Test:

[0104] Disk-shaped samples are cut from cool plaques using a 25mm diameter die cutter to extract a sample for creep testing.

[0105] A DMS (dynamic mechanical spectroscopy) frequency sweep is conducted on the disc-shaped samples using 25mm parallel plates at frequencies ranging from 0.1 to 100 rad / s. The test gap separating -I4 the plates is 1.5mm. A strain that satisfies linear viscoelastic conditions is applied, typically 10% strain. Each test is conducted under nitrogen atmosphere and isothermal conditions at 190°C. To initiate the DMS test, the rheometer oven is allowed to equilibrate at the desired testing temperature for at least 30 min before loading the sample into the test geometry. The sample is then equilibrated in the oven, with the door closed, for 5 min. The test gap is set to 1.5mm, which produces an axial force on the sample. After the sample relaxes this axial force, the oven was quickly opened, and the sample is trimmed so that no bulge is present. The DMS measurement is then initiated in the oven. During the test, the shear elastic modulus (G’), viscous modulus (G”) and complex viscosity are measured.

[0106] Immediately after the DMS frequency sweep measurement, under the same temperature and atmospheric conditions, the creep test is initiated using an applied stress of 20 Pa. During the test, a loglog plot of creep compliance with respect to time is continuously monitored for the achievement of steady state conditions, which is noted by obtaining a slope between 0.97 and unity in the plot; the creep test is stopped once steady state conditions are obtained. Afterwards, the measured shear strain during the test is plotted against the time elapsed in order to analyze the shear rate at the end of testing. The zero-shear viscosity of the melt sample was then obtained by dividing the applied shear stress (20 Pa) by the shear rate noted previously.

[0107] Finally, the melt sample is evaluated for signs of degradation, whether it be due to cross-linking or chain scission, by subjecting the sample to an additional DMS frequency sweep measurement immediately following the creep test (please note that the DMS test is consistently conducted at the same temperature and atmosphere as the creep measurement and with 10% strain). The sample is considered thermally stable when the viscosity documented at 0.1 rad / s is within 5% deviation from the viscosity of the same frequency that was measured in the initial DMS test that was performed before the creep assessment.

[0108] All creep, including the associated DMS frequency sweep, tests are conducted on either the DHR-3 or AR-G2 rheometers, both of which are manufactured by TA Instruments. Data analyses are conducted via TA Instruments TRIOS software.

[0109] Examples

[0110] The following examples illustrate specific embodiments of the invention, but do not limit the broadest scope of the invention.

[0111] The materials in Table 1 are used for the Examples:

[0112] Table 1

[0113] Preparation of Samples

[0114] Compounding:

[0115] Polymer mixtures as shown in Table 2 are compounded on a twin screw extruder, extruded through a die, cooled, and pelletized, and then ground to powders. Examples IE1 to IE4 are examples of the invention. Examples CE1 and CE2 are comparative examples.

[0116] Compression Molded Samples for Testing:

[0117] The powders of IE1 to IE4 and CE1 and CE2 are compression molded into plaques in a 9.75 in. by 10.25 in. rectangular chase of thickness 1.85mm at a pressure of 25,000 lbs. for 6.5 min. at 190°C. The plaques are used to test Zero Shear Viscosity, Elongation to Break, Charpy Impact Resistance, Secant Modulus and Environmental Stress Crack Resistance as described in the Test Methods. The results are shown in Table 2.

[0118] Table 2

[0119] Rotomolding Samples for ARM Testing

[0120] Rotomolding is performed using a Rotoline Lab 0.50 rotational molder with a 12in x 12in x 12in cube-shapes mold.

[0121] The oven temperature is set to 288°C (550 °F). A shot size of 2.9 lbs. of powder is sealed in the mold and provides a wall thickness of approximately 0.125 in (3.17 mm). The primary axis rotation is set to 6 rpm and the secondary axis rotation is set to 1.5 rpm. The arm rotation was reversed every 3 minutes.

[0122] The temperature inside the mold is monitored with a thermocouple in the center of the mold. The Rotoline Wireless Temperature Control (RWTC) feature is used to process parts to a specific peak internal air temperature (PIAT) of 170°C, 190°C, 200°C, 210°C, or 220°C as shown in Table 3. Each part is cooled to an internal air temperature of 90°C before being removed from the mold.

[0123] A total of 16 test specimens for ARM impact testing (5 in x 5 in plaques) are obtained from each rotomolded cube. The top and bottom sides of the cube are discarded. Each test specimen is subjected to ARM Impact testing. The average results are shown in Table 3.

[0124] Table 3

Claims

CLAIMS:We claim:

1. A rotomolding composition comprising the following:(a) from 50 to 94 wt.% of a polyethylene having a density from 0.910 g / cm3to 0.950 g / cm3and a melt index (L) from 1.0 g / 10 min to 10.0 g / 10 min;(b) from 5 to 40 wt.% of a recycled polyethylene composition comprising from 1 to 25 wt.% propylene -content, based on the total weight of the recycled polyethylene composition; and(c) from 1 to 15 wt.% of an ethylene-based elastomer having a density from 0.850 g / cm3to 0.900 g / cm3and a melt index (L) from 0.5 to 30.0 g / 10 min, wherein weight percentages of (a), (b) and (c) are based on the total weight of the rotomolding composition.

2. The rotomolding composition of claim 1, wherein the rotomolding composition comprises from 60 to 80 wt.% of the polyethylene and wherein the polyethylene has a density from 0.925 g / cm3to 0.939 g / cm3and a melt index (L) from 3.0 g / 10 min to 8.0 g / 10 min.

3. The rotomolding composition of any one of the preceding claims, wherein the recycled polyethylene composition has a density from 0.940 g / cm3to 0.960 g / cm3, a melt index (L) from 0.5 g / 10 min. to 8.0 g / 10 min; and a propylene-content from 10 to 20 wt.%, based on the total weight of the recycled polyethylene composition.

4. The rotomolding composition of any one of the preceding claims, wherein the rotomolding composition comprises from 15 to 30 wt.% of recycled polyethylene composition, based on the total weight of the rotomolding composition.

5. The rotomolding composition of any one of the preceding claims, wherein the recycled polyethylene composition has a density from 0.910 g / cm3to 0.940 g / cm3; a melt index (L) from 0.5 g / 10 min. to 8.0 g / 10 min; and a propylene-content from 10 to 20 wt.%, based on the total weight of the rotomolding composition.

6. The rotomolding composition of any one of the preceding claims, wherein the ethylene-based elastomer has a density from 0.860 g / cm3to 0.900 g / cm3and a melt index (L) from 3.0 g / 10 min. to 8.0 g / 10 min.

7. The rotomolding composition any one of the preceding claims, wherein the rotomolding composition comprises from 2 to 12 wt.% of the ethylene-based elastomer, wherein weight percentages are based on the total weight of the rotomolding composition.

8. The rotomolding composition of any one of the preceding claims, wherein the ethylene-based elastomer is a random copolymer.

9. The rotomolding composition of any one of the preceding claims, wherein the rotomolding composition comprises from 60 to 80 wt.% of the polyethylene and from 15 to 30 wt.% of the recycledpolyethylene composition, based on the total weight of the rotomolding composition; and wherein the polyethylene has a density from 0.925 g / cm3to 0.939 g / cm3and a melt index (I2) from 3.0 g / 10 min. to 8.0 g / 10 min, and the recycled polyethylene composition has a density from 0.940 g / cm3to 0.960 g / cm3, a melt index (I2) from 0.5 g / 10 min. to 8.0 g / 10 min, a propylene content from 2 to 8 wt.%, based on the total weight of the recycled polyethylene composition.

10. The rotomolding composition of any one of 1-7, 9, wherein the ethylene-based elastomer is an ethylene / a-olefin multi-block interpolymer.

11. The rotomolding composition of any one of the preceding claims, wherein the rotomolding composition comprises from 65 to 80 wt.% of the polyethylene and from 20 to 30 wt.% recycled polyethylene composition, based on the total weight of the rotomolding composition, and wherein the polyethylene has a density from 0.925 g / cm3to 0.939 g / cm3and a melt index (I2) from 3.0 g / 10 min to 8.0 g / 10 min, and the recycled polyethylene composition has a density from 0.940 g / cm3to 0.960 g / cm3, a melt index (I2) from 0.5 g / 10 min. to 8.0 g / 10 min, and a propylene content from 2 to 8 wt.%.

12. The rotomolding composition any one of the preceding claims, wherein the rotomolding composition has a density from 0.925 g / cm3to 0.940 g / cm3.

13. The rotomolding composition of any one of the preceding claims, wherein the rotomolding composition has a melt index (I2) from 3.0 g / 10 min. to 8.0 g / 10 min.

14. The rotomolding composition of any of one of the preceding claims, wherein the rotomolding composition is in the form of powder having a median particle size from 100 microns to less than 1000 microns.

15. A rotomolding process comprising the steps of:(a) loading a rotomolding composition into a mold and closing the mold (the “loading step”);(b) heating the mold to a temperature at which the rotomolding composition melts, while rotating the mold on at least two axes to form a coating of the rotomolding composition adhered to an internal surface of the mold (the “heating step”);(c) cooling the mold to solidify the rotomolding composition adhered to the internal surface of the mold to form a molded article (the “cooling step”); and(d) releasing the molded article from the mold (the “extraction step”); wherein the rotomolding composition is in accordance with any one of the preceding claims.

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