Thermoplastic elastomer compositions and methods of preparation of the same

Abstract

Various thermoplastic elastomer (TPE) compositions comprise a rubber component comprising: (i) a high molecular weight styrene-ethylene-butylene-styrene (SEBS) polymer having a number average molecular weight of from 75,000 g / mol to 300,000 g / mol; and (ii) a low molecular weight SEBS polymer having a polystyrene content of less than about 30 wt.% and a number average molecular weight of from 10,000 g / mol to less than 75,000 g / mol. The TPE compositions further comprise a polyolefin and an oil. The TPE compositions are suitable for use in rotomolding applications for forming various rotomolded products.

Description

THERMOPLASTIC ELASTOMER COMPOSITIONS AND METHODS OF PREPARATION OF THE SAMECLAIM OF PRIORITY

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 570,801 bearing Attorney Docket Number 1202403 and filed on March 27, 2024, which is hereby incorporated by reference in its entirety.FIELD

[0002] The present disclosure relates to thermoplastic elastomer (TPE) compositions and, more particularly, to TPE compositions for use in rotational molding applications.BACKGROUND

[0003] Conventional rotational molding is typically performed on a carousel machine in which several independent arms are cycled through different stations (e.g., a heating chamber, a cooling area, and a loading / unloading area). Each arm of the carousel machine typically contains one or more molds which are independently rotated on a platform that simultaneously rotates in a perpendicular plane, achieving biaxial rotation. This type of rotation allows for hollow parts to be formed, and the rotation is typically carried out under low rotational speeds (e.g., 2-10 rpm) in each direction. Accordingly, a polymer powder or micropellet material can be loaded into the mold, heated with biaxial rotation in a low shear rate environment, cooled with continued biaxial rotation, and then removed from the mold.

[0004] Rotational molding found its origins in plastics starting with using polyvinyl chloride (PVC) to manufacture toys (e.g., doll heads) before polyethylene and other resins became more widely adopted. Additionally, the low shear conditions of the rotational molding process may preclude materials from successfully filling the mold, which can reduce the amount of detail present in the resultant molded product. Additionally, semi -crystalline polyolefins such as polypropylene (PP) and polyethylene (PE) tend to exhibit low zero-shear viscosity, but there is a limited range of surface properties, haptics, and hardness that can be achieved using such material. For example, a non-rigid surface may be desired for rotomolded furniture applications, which would require the use of a materialother than PE. Although thermoplastic elastomers (TPEs) have replaced PVC in other applications due to their recyclability and potential to be produced from bio-derived feedstocks, TPEs and, in particular, styrenic-based systems, are not typically suitable for use in rotational molding due to their inherently high viscosities in the molten state under low shear conditions.

[0005] Accordingly, there remains a need for alternative materials for use in rotomolding applications.SUMMARY

[0006] The following is a brief summary of subject matter that is described in greater detail herein. This summary is not intended to be limiting as to the scope of the claims.

[0007] According to a first aspect of the present disclosure, a composition comprises a rubber component, a polyolefin, and an oil. The rubber component comprises (i) a high molecular weight styrene-ethylene-butylene-styrene (SEBS) polymer having a number average molecular weight of from 75,000 g / mol to 300,000 g / mol; and (ii) a low molecular weight SEBS polymer having a polystyrene content of less than about 30 wt.% and a number average molecular weight of from 10,000 g / mol to less than 75,000 g / mol.

[0008] In any of the aspects herein, the composition may have a complex viscosity of less than 100 Pa*s at 0.1 rad / s in the temperature range of 200-250 °C, when measured in accordance with ASTM D4440 using a strain amplitude at or below 5%. The low molecular weight SEBS polymer may be a tri-block SEBS polymer. The tri-block SEBS polymer may comprise an ethylene / butylene midblock and one or more styrene-containing end blocks.

[0009] In aspects, the polyolefin comprises a polypropylene homopolymer, a polypropylene random copolymer, a high density polyethylene (HDPE), a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE), and combinations thereof. The polyolefin may comprise a polyethylene having a melt flow index of greater than or equal to 40 g / 10 min, as measured in accordance with ASTM DI 238 at 190 °C and 2.16 kg. The polyolefin may comprise a polypropylenehaving a melt flow index of greater than or equal to 50 g / 10 min, as measured in accordance with ASTM DI 238 at 230 °C and 2.16 kg.

[0010] In any of the aspects, the oil may be present in an amount of greater than or equal to about 20 wt.%, based on a total weight of the composition. The oil may comprise a polyalphaolefin (PAO) or mineral oil. The oil may comprise a bio-derived oil. In aspects, the oil has a flashpoint of greater than about 230 °C, as measured in accordance with ASTM D92. The oil may have a kinematic viscosity of less than or equal to 105 cSt as measured in accordance with ASTM D445 at 40 °C.

[0011] In any preceding aspect, the high molecular weight SEBS polymer may have a number average molecular weight of from 75,000 g / mol to 125,000 g / mol. The low molecular weight SEBS polymer may have a number average molecular weight of 40,000 g / mol to 70,000 g / mol or 55,000 g / mol to 65,000 g / mol. A ratio of an amount of the rubber composition to an amount of the oil may be 1 : 1. A ratio of an amount of the high molecular weight SEBS polymer to an amount of the low molecular weight SEBS polymer may be from 1.1 : 1 to 1.5: 1.

[0012] In aspects disclosed herein, the composition may be formed into a plurality of particles having an average particle size of less than about 1,000 pm. The composition may be formed into the plurality of particles through cryogrinding. The plurality of particles may comprise a plurality of micropellets.

[0013] Aspects of the present disclosure also provide a rotomolded article comprising the compound of any preceding aspect. The rotomolded article may have a wall thickness of from about 0.5 mm to about 50 mm. The rotomolded article may comprise a void therein.

[0014] In various aspects, a process for forming a product comprises forming a rotomolded article by rotomolding a composition according to any of the aspects described herein. In aspects, the process comprises forming a rotomolded article by rotomolding a composition comprising a rubber component, a polyolefin, and an oil. The rubber component comprises (i) a high molecular weight styrene-ethylene-butylene-styrene (SEBS) polymer having a number average molecular weight of from 75,000 g / mol to 300,000 g / mol; and (ii) a low molecular weight SEBS polymer having a polystyrene content of less than about 30 wt.% and a number average molecular weight of from 10,000g / mol to 75,000 g / mol. In aspects, the process further comprises at least partially filling a void in the molded article with foam.

[0015] The above summary presents a simplified summary in order to provide a basic understanding of some aspects of the systems and / or methods discussed herein. This summary is not an extensive overview of the systems and / or methods discussed herein. It is not intended to identify key / critical elements or to delineate the scope of such systems and / or methods. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The general inventive concepts, as well as illustrative embodiments and advantages thereof, are described below in greater detail, by way of example, with reference to the drawings in which:

[0017] FIG. 1 shows photographs of sample plaques prepared from the compositions described in Example 1 showing ink pen and permanent marker removal resistance at time 0 and 168 hours;

[0018] FIG. 2 A is a photograph of a rotomolded part prepared from the composition described in Example 3;

[0019] FIG. 2B is a magnified image of a rotomolded part prepared from the composition described in Example 3 showing surface pitting;

[0020] FIG. 2C is the negative of the image of FIG. 2b, resolving the pitting in the surface more clearly;

[0021] FIG. 3A is a graph of the thermogravimetric analysis for various white mineral oils and a polyalphaolefin oil in which temperature (°C) is shown on the x-axis and weight (%) is shown on the y-axis;

[0022] FIG. 3B is a graph of the thermogravi metric analysis for various white mineral oils and a polyalphaolefin oil in which time (minutes) is shown on the x-axis and weight (%) is shown on the y- axis;

[0023] FIG. 3C is a photograph of surfaces prepared from the formula described in Example 4 at 170 °C, 180 °C, and 190 °C, showing that pitting diminished with increasing temperature;

[0024] FIG. 4A is a photograph of the experimental setup for Example 5;

[0025] FIG. 4B is a photograph of a part prepared from Formula I as described in Example 5;

[0026] FIG. 4C is a magnified view of the part shown in FIG. 4B;

[0027] FIG. 5A is a graph of the SAGS temperature sweeps at 1% strain, 0.5 rad / s for Formulas O-R, in which temperature (°C) is on the x-axis, storage modulus and loss modulus (Pa) are on the left-hand y-axis, and tan(6) is on the right-hand y-axis; and

[0028] FIG. 5B is a graph of the SAGS temperature sweeps at 1% strain for Formula P at various temperatures (170 °C, 180 °C, 190 °C, and 200 °C) along with temperature sweeps at 1% strain for Formula I at 240 °C, in which angular frequency (rad / s) is on the x-axis and complex viscosity (Pa*s) is on the y-axis.DETAILED DESCRIPTION

[0029] Disclosed herein are low viscosity thermoplastic elastomer (TPE) compositions including a rubber component, a polyolefin, and an oil, and methods of making the same. In particular, in various aspects described herein, a TPE composition includes a rubber component that comprises a high molecular weight styrene-ethylene / butylene-styrene (SEBS) polymer and a low molecular weight SEBS polymer, a polyolefin, and an oil. The blend of the high molecular weight SEBS polymer and the low molecular weight SEBS polymer provides a low melt viscosity under low shear conditions, which renders the TPE composition suitable for rotational molding applications while reducing or eliminating pitting on the surface. Products formed from the TPE compositions may also exhibitenhanced cleanability with respect to permanent marker and ink. Other advantages are possible and contemplated and may be realized based on the following disclosure.

[0030] The terminology as set forth herein is for description of the various aspects only and should not be construed as limiting the disclosure as a whole. All references to singular characteristics or limitations of the present disclosure shall include the corresponding plural characteristic or limitation, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made. Unless specified otherwise, “a,” “an,” “the,” and “at least one” are used interchangeably. Furthermore, as used in the description and the appended claims, the singular forms “a,” “an,” and “the” are inclusive of their plural forms, unless the context clearly indicates otherwise.

[0031] Unless otherwise expressly defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art.

[0032] Unless otherwise expressly stated, it not intended that any method disclosed herein be construed as requiring that its steps be performed in a specific order, nor that any article set forth herein be construed as requiring specific orders or orientations to its individual components.

[0033] To the extent that the term “includes” or “including” is used in the description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use.

[0034] Any composition described in the present disclosure can comprise, consist of, or consist essentially of the essential elements of the disclosure as described herein, as well as any additional or optional element described herein, or which is otherwise useful in rotational molding applications.

[0035] All percentages, parts, and ratios as used herein are by weight of the total blend on an “dry” basis, i.e., without solvents, unless otherwise specified.

[0036] All ranges and parameters, including but not limited to percentages, parts, and ratios, disclosed herein are understood to encompass any and all sub-ranges assumed and subsumed therein, and every number between the endpoints. For example, a stated range of “1 to 10” should be considered to include any and all sub-ranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 1 to 6.1, or 2.3 to 9.4), and to each integer (1, 2, 3, 4, 5, 6, 7, 8, 9, and 10) contained within the range. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiments includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0037] The term “wt.%,” as described herein, refers to the weight fraction of the individual component based on a total weight of the thermoplastic layer composition, unless otherwise noted.

[0038] Additionally, as used herein, the term “exemplary” is intended to mean serving as an illustration or example of something, and is not intended to indicate a preference.

[0039] The term “melt flow index,” as described herein, refers to the ability of a material’s melt to flow under pressure as measured according to ASTM DI 238 at the given temperature and given weight.

[0040] As used herein, the term “thermoplastic” refers to a polymer that softens when exposed to heat and returns to its original condition when at room temperature.

[0041] In various aspects provided herein, a thermoplastic elastomer (TPE) composition is disclosed that includes a rubber component, a polyolefin, and an oil. In any of the aspects described herein, the rubber component includes a high molecular weight SEBS polymer and a low molecular weight SEBS polymer. The composition may exhibit a relatively low melt viscosity (e.g., less than 100 Pa*s) at low shear rates (e.g., 0.1 rad / s) when measured at 200 °C. Products made through rotational molding of the composition may have reduced surface pitting and may exhibit an enhancedcleanability with respect to permanent marker and ink. Other advantages may be realized, depending on the particular aspects, which will now be described in greater detail.Rubber Component

[0042] As set forth above, the low viscosity TPE composition may comprise a rubber component that includes a high molecular weight SEBS polymer and a low molecular weight SEBS polymer, with the respective molecular weights defined below. In various aspects, the rubber component may consist of or consist essentially of the high molecular weight SEBS polymer and the low molecular weight SEBS polymer. The rubber component is present in the composition in an amount of from about 20 wt.% to about 50 wt.%, based on a total weight of the composition. For example, the rubber component can be included in the composition in an amount of from about 20 wt.% to about 50 wt.%, from about 25 wt.% to about 50 wt.%, from about 30 wt.% to about 50 wt.%, from about 35 wt.% to about 50 wt.%, from about 40 wt.% to about 50 wt.%, from about 45 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%, from about 25 wt.% to about 45 wt.%, from about 30 wt.% to about 45 wt.%, from about 35 wt.% to about 45 wt.%, from about 40 wt.% to about 45 wt.%, from about 20 wt.% to about 40 wt.%, from about 25 wt.% to about 40 wt.%, from about 30 wt.% to about 40 wt.%, from about 35 wt.% to about 40 wt.%, from about 20 wt.% to about 35 wt.%, from about 25 wt.% to about 35 wt.%, or from about 30 wt.% to about 35 wt.%, including any and all ranges and subranges including any of these endpoints.High Molecular Weight SEBS Polymer

[0043] The high molecular weight SEBS polymer is a styrene block copolymer that includes blocks of styrene-ethylene and butylene-styrene polymers. The high molecular weight SEBS polymer can be a diblock or triblock copolymer based on styrene-ethylene and butylene-styrene. In any of the aspects described herein, the high molecular weight SEBS polymer may have a styrene content of greater than or equal to about 20%. However, it is contemplated that in various aspects, the high molecular weight SEBS polymer may have a styrene content of less than 20%. Accordingly, the styrene content is not particularly limited.

[0044] In various aspects provided herein, the high molecular weight SEBS polymer has a number average molecular weight (Mn) of greater than or equal to 75,000 g / mol. In certain aspects, the high molecular weight SEBS polymer may have a Mnof greater than or equal to 80,000 g / mol, greater than or equal to 90,000 g / mol, or even greater than or equal to 100,000 g / mol. In these or other aspects, the high molecular weight SEBS may have a Mnless than or equal to 300,000 g / mol, less than or equal to 250,000 g / mol, less than or equal to 200,000 g / mol, less than or equal to 175,000 g / mol, less than or equal to 150,000 g / mol, less than or equal to 140,000 g / mol, or even less than or equal to 130,000 g / mol. For example, the high molecular weight SEBS may have a Mngreater than or equal to 75,000 g / mol and less than or equal to 300,000 g / mol, greater than or equal to 75,000 g / mol and less than or equal to 250,000 g / mol, greater than or equal to 75,000 g / mol and less than or equal to 200,000 g / mol, greater than or equal to 75,000 g / mol and less than or equal to 175,000 g / mol, greater than or equal to 75,000 g / mol and less than or equal to 150,000 g / mol, greater than or equal to 75,000 g / mol and less than or equal to 140,000 g / mol, greater than or equal to 75,000 g / mol and less than or equal to 130,000 g / mol, greater than or equal to 75,000 g / mol and less than or equal to 125,000 g / mol, greater than or equal to 80,000 g / mol and less than or equal to 300,000 g / mol, greater than or equal to 80,000 g / mol and less than or equal to 250,000 g / mol, greater than or equal to 80,000 g / mol and less than or equal to 200,000 g / mol, greater than or equal to 80,000 g / mol and less than or equal to 175,000 g / mol, greater than or equal to 80,000 g / mol and less than or equal to 150,000 g / mol, greater than or equal to 80,000 g / mol and less than or equal to 140,000 g / mol, greater than or equal to 80,000 g / mol and less than or equal to 130,000 g / mol, greater than or equal to 80,000 g / mol and less than or equal to 125,000 g / mol, greater than or equal to 90,000 g / mol and less than or equal to 300,000 g / mol, greater than or equal to 90,000 g / mol and less than or equal to 250,000 g / mol, greater than or equal to 90,000 g / mol and less than or equal to 200,000 g / mol, greater than or equal to 90,000 g / mol and less than or equal to 175,000 g / mol, greater than or equal to 90,000 g / mol and less than or equal to 150,000 g / mol, greater than or equal to 90,000 g / mol and less than or equal to 140,000 g / mol, greater than or equal to 90,000 g / mol and less than or equal to 130,000 g / mol, greater than or equal to 90,000 g / mol and less than or equal to 125,000 g / mol, greater than or equal to 100,000 g / mol and less than or equal to 300,000 g / mol, greater than or equal to 100,000 g / mol and less than or equal to 250,000 g / mol, greater than or equal to 100,000 g / mol and less than or equal to 200,000 g / mol, greater than or equal to 100,000 g / mol and less than or equal to 175,000 g / mol, greater than or equal to 100,000 g / mol and less than or equal to150,000 g / mol, greater than or equal to 100,000 g / mol and less than or equal to 140,000 g / mol, or even greater than or equal to 100,000 g / mol and less than or equal to 130,000 g / mol, or greater than or equal to 100,000 g / mol and less than or equal to 125,000 g / mol, or any and all sub-ranges formed from any of these endpoints. In various aspects, the Mnof the SEBS polymer is measured using gel permeation chromatography (GPC) and a polystyrene (PS) standard.

[0045] The high molecular weight SEBS may be included in the rubber component in an amount of from about 40 wt.% to about 80 wt.%, based on a total weight of the rubber component. In aspects described herein, the high molecular weight SEBS is included in the rubber component in an amount of from about 40 wt.% to about 80 wt.%, from about 40 wt.% to about 75 wt.%, from about 40 wt.% to about 70 wt.%, from about 40 wt.% to about 65 wt.%, from about 40 wt.% to about 60 wt.%, from about 40 wt.% to about 55 wt.%, from about 40 wt.% to about 50 wt.%, from about 45 wt.% to about 80 wt.%, from about 45 wt.% to about 75 wt.%, from about 45 wt.% to about 70 wt.%, from about 45 wt.% to about 65 wt.%, from about 45 wt.% to about 60 wt.%, from about 45 wt.% to about 55 wt.%, from about 50 wt.% to about 80 wt.%, from about 50 wt.% to about 75 wt.%, from about 50 wt.% to about 70 wt.%, from about 50 wt.% to about 65 wt.%, from about 50 wt.% to about 60 wt.%, from about 50 wt.% to about 55 wt.%, from about 55 wt.% to about 80 wt.%, from about 55 wt.% to about 75 wt.%, from about 55 wt.% to about 70 wt.%, from about 55 wt.% to about 65 wt.%, from about 55 wt.% to about 60 wt.%, from about 60 wt.% to about 80 wt.%, from about 60 wt.% to about 75 wt.%, from about 60 wt.% to about 70 wt.%, or from about 60 wt.% to about 65 wt.%, based on a total weight of the rubber component, including any and all sub-ranges formed from any of these endpoints.Low Molecular Weight SEBS Polymer

[0046] The rubber component also includes a low molecular weight SEBS polymer. The low molecular weight SEBS polymer is a styrene block copolymer that includes blocks of styrene-ethylene and butyl ene-styrene polymers. The low molecular weight SEBS polymer can be a di -block or triblock copolymer based on styrene-ethylene and butylene-styrene. Although di-blocks may be used in aspects described herein, products formed from compositions including a di-block low molecular weight SEBS polymer may lack mechanical performance (e.g., tear strength) that can be achievedusing tri-block polymers. In any of the aspects described herein, the low molecular weight SEBS polymer is a triblock copolymer having ethylene-butylene mid-blocks and styrene end blocks.

[0047] In any of the aspects described herein, the low molecular weight SEBS polymer has a styrene content of less than about 30%. For example, the low molecular weight SEBS polymer may have a styrene content of less than about 27%, less than about 25%, less than about 22%, or less than about 20%.

[0048] In various aspects provided herein, the low molecular weight SEBS polymer has a Mnof less than or equal to 75,000 g / mol. In aspects, the low molecular weight SEBS polymer has a Mnof less than 75,000 g / mol, less than or equal to 50,000 g / mol, or even less than or equal to 25,000 g / mol. In aspects, the low molecular weight SEBS may have a Mngreater than or equal to 10,000 g / mol, greater than or equal to 25,000 g / mol, or greater than or equal to 50,000 g / mol. For example, the low molecular weight SEBS may have a Mnfrom 10,000 g / mol to less than 75,000 g / mol, from 10,000 g / mol to 70,000 g / mol, from 10,000 g / mol to 60,000 g / mol, from 10,000 g / mol to 50,000 g / mol, from 10,000 g / mol to 40,000 g / mol, from 10,000 g / mol to 30,000 g / mol, from 20,000 g / mol to less than 75,000 g / mol, from 20,000 g / mol to 70,000 g / mol, from 20,000 g / mol to 60,000 g / mol, from 20,000 g / mol to 50,000 g / mol, from 20,000 g / mol to 40,000 g / mol, from 20,000 g / mol to 30,000 g / mol, from 30,000 g / mol to less than 75,000 g / mol, from 30,000 g / mol to 70,000 g / mol, from 30,000 g / mol to 60,000 g / mol, from 30,000 g / mol to 50,000 g / mol, from 30,000 g / mol to 40,000 g / mol, from 40,000 g / mol to less than 75,000 g / mol, from 40,000 g / mol to 70,000 g / mol, from 40,000 g / mol to 60,000 g / mol, from 40,000 g / mol to 50,000 g / mol, from 50,000 g / mol to less than 75,000 g / mol, from 50,000 g / mol to 70,000 g / mol, or from 50,000 g / mol to 60,000 g / mol, including any and all sub-ranges formed from any of these endpoints.

[0049] The low molecular weight SEBS may be included in the rubber component in an amount of from about 20 wt.% to about 60 wt.%, based on a total weight of the rubber component. In aspects described herein, the low molecular weight SEBS is included in the rubber component in an amount of from about 20 wt.% to about 60 wt.%, from about 20 wt.% to about 55 wt.%, from about20 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%, from about 20 wt.% to about 40 wt.%, from about 20 wt.% to about 35 wt.%, from about 20 wt.% to about 30 wt.%, from about 25wt.% to about 60 wt.%, from about 25 wt.% to about 55 wt.%, from about 25 wt.% to about 50 wt.%, from about 25 wt.% to about 45 wt.%, from about 25 wt.% to about 40 wt.%, from about 25 wt.% to about 35 wt.%, from about 30 wt.% to about 60 wt.%, from about 30 wt.% to about 55 wt.%, from about 30 wt.% to about 50 wt.%, from about 30 wt.% to about 45 wt.%, from about 30 wt.% to about 40 wt.%, from about 30 wt.% to about 35 wt.%, from about 35 wt.% to about 60 wt.%, from about 35 wt.% to about 55 wt.%, from about 35 wt.% to about 50 wt.%, from about 35 wt.% to about 45 wt.%, from about 35 wt.% to about 40 wt.%, from about 40 wt.% to about 60 wt.%, from about 40 wt.% to about 55 wt.%, from about 40 wt.% to about 50 wt.%, or from about 40 wt.% to about 45 wt.%, based on a total weight of the rubber component, including any and all sub-ranges formed from any of these endpoints.

[0050] In any of the aspects described herein, a ratio of an amount of the high molecular weightSEBS polymer to an amount of the low molecular weight SEBS polymer is from 1.1 :1 to 1.5: 1. For example, the ratio of the amount of the high molecular weight SEBS polymer to the amount of the low molecular weight SEBS polymer can be from 1.1 : 1 to 1.5:1, from 1.1 : 1 to 1.4: 1, from 1.1 : 1 to 1.3: 1, from 1.1 :1 to 1.2: 1, from 1.2:1 to 1.5: 1, from 1.2: 1 to 1.4: 1, from 1.2: 1 to 1.3:1, from 1.3: 1 to 1.5:1, from 1.3: 1 to 1.4: 1, or from 1.4: 1 to 1.5: 1, including any and all sub-ranges formed from any of these endpoints.

[0051] Without being bound by theory, it is believed that the low molecular weight SEBS polymer causes the order-disorder transition (ODT) temperature of the high molecular weight SEBS polymer. The ODT occurs at a temperature in which the styrene block segments become miscible with the ethyl ene-butylene block, and the polymer behaves as a random / disordered melt. At temperatures below the ODT, but above the glass transition temperature for SEBS (e.g., approximately 100 °C), SEBS block copolymers demonstrate “melt-ordering” in which the styrene domains are still associated and the X parameter is too large to fully mix with the ethylene-butylene blocks. The X parameter was first used in Flory -Huggins polymer theory and now is widely used in different systems to describe the interaction between two components in the same molecule or from different molecules. The ODT has been observed to increase in temperature with increasing styrene wt.% and molecular weight of the styrene domains. Accordingly, it is believed that incorporating the low molecular weightSEBS polymer lowers the ODT temperature, and allows access to lower viscosities at low shear rates (e g., 0.1 rad / s).

[0052] In any of the aspects described herein, the TPE composition may have an ODT of equal or less than 240 °C, equal or less than 235 °C, equal or less than 230 °C, equal or less than 225 °C, equal or less than 220 °C, equal or less than 215 °C, equal or less than 210 °C, equal or less than 205 °C, equal or less than 200 °C, equal or less than 195 °C, equal or less than 190 °C, equal or less than 185 °C, equal or less than 180 °C, equal or less than 175 °C, equal or less than 170 °C, equal or less than 165 °C, or equal or less than 160 °C. In any of the aspects described herein, the TPE composition may have an ODT of equal or greater than 155 °C, equal or greater than 160 °C, equal or greater than 165 °C, equal or greater than 170 °C, equal or greater than 175 °C, equal or greater than 180 °C, equal or greater than 185 °C, equal or greater than 190 °C, equal or greater than 195 °C, equal or greater than 200 °C, equal or greater than 205 °C, equal or greater than 210 °C, equal or greater than 215 °C, equal or greater than 220 °C, equal or greater than 225 °C, equal or greater than 230 °C, or equal or greater than 235 °C. In any of the aspects described herein, the TPE composition may have an ODT in the range of about 155 °C to 240 °C, in the range of about 160 °C to 235 °C, in the range of about 165 °C to 230 °C, in the range of about 160 °C to 170 °C, in the range of about 170 °C to 180 °C, in the range of about 180 °C to 190 °C, in the range of about 190 °C to 200 °C, in the range of about 200 °C to 210 °C, in the range of about 210 °C to 220 °C, in the range of about 220 °C to 230 °C, or in the range of about 230 °C to 240 °C, including any and all sub-ranges formed from any of these endpoints.Manufacture

[0053] In any of the aspects described herein, the rubber component can be formed by compounding or otherwise combining the high molecular weight SEBS polymer and the low molecular weight SEBS polymer to produce a rubber component. Alternatively, the high molecular weight SEBS polymer and the low molecular weight SEBS polymer can be added independently tothe oil and polyolefin (described below) to form the composition, without forming a separate rubber component first.Polyolefin

[0054] In various aspects provided herein, the TPE composition also includes at least one polyolefin. The polyolefin may include, for example, polypropylene (PP), including a polypropylene random copolymer or a polypropylene homopolymer, or polyethylene (PE), including a high-density polyethylene (HDPE), a low-density polyethylene (LDPE), or a linear low-density polyethylene (LLDPE), or combinations thereof. The polyolefin, and particularly PP, may improve clarity, reduce stiffness and increase flexibility, and may enable the oil content to be reduced while maintaining a similar modulus for the composition.

[0055] In aspects including a polyethylene (PE) as the polyolefin, the polyethylene can have a melt flow index of greater than or equal to 40 g / 10 min when measured in accordance with ASTM D1238 at 190 °C and 2.16 kg. For example, the PE can have a melt flow index of from about 40 g / 10 min to about 100 g / 10 min, from about from about 40 g / 10 min to about 90 g / 10 min, from about 40 g / 10 min to about 80 g / 10 min, from about 40 g / 10 min to about 70 g / 10 min, from about 40 g / 10 min to about 60 g / 10 min, from about 40 g / 10 min to about 50 g / 10 min, from about 45 g / 10 min to about 100 g / 10 min, from about from about 45 g / 10 min to about 90 g / 10 min, from about 45 g / 10 min to about 80 g / 10 min, from about 45 g / 10 min to about 70 g / 10 min, from about 45 g / 10 min to about 60 g / 10 min, from about 45 g / 10 min to about 50 g / 10 min, from about 50 g / 10 min to about 100 g / 10 min, from about from about 50 g / 10 min to about 90 g / 10 min, from about 50 g / 10 min to about 80 g / 10 min, from about 50 g / 10 min to about 70 g / 10 min, or from about 50 g / 10 min to about 60 g / 10 min, including any and all sub-ranges formed from any of these endpoints.

[0056] In aspects including a polypropylene as the polyolefin, the polypropylene (PP) can have a melt flow index of greater than or equal to 50 g / 10 min when measured in accordance with ASTM D1238 at 230 °C and 2.16 kg. For example, the PP can have a melt flow index of from about 50 g / 10 min to about 1200 g / 10 min, from about from about 50 g / 10 min to about 1000 g / 10 min, from about from about 50 g / 10 min to about 750 g / 10 min, from about from about 50 g / 10 min to about 500 g / 10min, from about from about 50 g / 10 min to about 250 g / 10 min, from about from about 50 g / 10 min to about 100 g / 10 min, from about from about 50 g / 10 min to about 90 g / 10 min, from about 50 g / 10 min to about 80 g / 10 min, from about 50 g / 10 min to about 70 g / 10 min, from about 50 g / 10 min to about 60 g / 10 min, from about 55 g / 10 min to about 1200 g / 10 min, from about from about 55 g / 10 min to about 1000 g / 10 min, from about from about 55 g / 10 min to about 750 g / 10 min, from about from about 55 g / 10 min to about 500 g / 10 min, from about from about 55 g / 10 min to about 250 g / 10 min, from about 55 g / 10 min to about 100 g / 10 min, from about from about 55 g / 10 min to about 90 g / 10 min, from about 55 g / 10 min to about 80 g / 10 min, from about 55 g / 10 min to about 70 g / 10 min, from about 55 g / 10 min to about 60 g / 10 min, from about 60 g / 10 min to about 1200 g / 10 min, from about from about 60 g / 10 min to about 1000 g / 10 min, from about from about 60 g / 10 min to about 750 g / 10 min, from about from about 60 g / 10 min to about 500 g / 10 min, from about from about 60 g / 10 min to about 250 g / 10 min, from about 60 g / 10 min to about 100 g / 10 min, from about from about 60 g / 10 min to about 90 g / 10 min, from about 60 g / 10 min to about 80 g / 10 min, or from about 60 g / 10 min to about 70 g / 10 min, including any and all sub-ranges formed from any of these endpoints.

[0057] Commercially available polyolefins suitable for inclusion in the composition include, by way of example and not limitation, TOTAL™ 3860X (a polypropylene homopolymer having a melt flow index of 100 g / 10 min (2.16 kg; 230 °C) available from Total Energies,), PINNACLE™ PP 6180 C3 (a polypropylene random copolymer having a melt flow index of 80 g / 10 min (2.16 kg; 230 °C) available from Pinnacle Polymers), and METOCENE™ MF650X (a polypropylene homopolymer having a melt flow index of 1200 g / 10 min (2.16 kg; 230 °C) available from LyondellBasell Industries).

[0058] In any of the aspects described herein, the polyolefin is included in the composition in an amount of from about 20 wt.% to about 60 wt.%. The specific amount of polyolefin included in the composition can vary depending on the melt flow index of the polyolefin, the desired hardness of the final product prepared from the composition, and the processing parameters to which the composition will be subjected. For example, the composition can include the polyolefin in an amount of from about 20 wt.% to about 60 wt.%, from about 20 wt.% to about 55 wt.%, from about 20 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%, from about 20 wt.% to about 40 wt.%, from about 20 wt.% to about 35 wt.%, from about 25 wt.% to about 60 wt.%, from about 25 wt.% to about55 wt.%, from about 25 wt.% to about 50 wt.%, from about 25 wt.% to about 45 wt.%, from about 25 wt.% to about 40 wt.%, from about 25 wt.% to about 35 wt.%, from about 30 wt.% to about 60 wt.%, from about 30 wt.% to about 55 wt.%, from about 30 wt.% to about 50 wt.%, from about 30 wt.% to about 45 wt.%, from about 30 wt.% to about 40 wt.%, from about 30 wt.% to about 35 wt.%, from about 35 wt.% to about 60 wt.%, from about 35 wt.% to about 55 wt.%, from about 35 wt.% to about 50 wt.%, from about 35 wt.% to about 45 wt.%, or from about 35 wt.% to about 40 wt.%, based on a total weight of the composition, including any and all sub-ranges formed from any of these endpoints.Oil

[0059] As described above, the composition further includes at least one oil. Without being bound by theory, it is believed that the oil can contribute to graffiti, permanent marker, and ink removal performance. Accordingly, in any of the exemplary aspects, the TPE composition may be ink / marker stain and graffiti resistant. Moreover, the oil may contribute to the processing temperatures for the composition. In particular, limitations in the processing temperatures of the composition may be related to the vaporization of the oil and, as such, selection of the oil can enable varying processing temperatures. The oil may further be used to adjust the softness and / or improve flow of the composition.

[0060] In various aspects provided herein, the oil may comprise a polyalphaolefin (PAO), mineral oil, or a combination thereof. The oil can be, in any of the aspects, a bio-derived oil. In various aspects, the oil has a flashpoint of greater than about 230 °C, as measured in accordance with ASTM D92. For example, the oil may have a flashpoint of from about 230 °C to about 300 °C, from about 230 °C to about 290 °C, from about 230 °C to about 280 °C, from about 230 °C to about 270 °C, from about 230 °C to about 260 °C, from about 230 °C to about 250 °C, from about 235 °C to about 300 °C, from about 235 °C to about 290 °C, from about 235 °C to about 280 °C, from about 235 °C to about 270 °C, from about 235 °C to about 260 °C, from about 235 °C to about 250 °C, from about 240 °C to about 300 °C, from about 240 °C to about 290 °C, from about 240 °C to about 280 °C, from about 240 °C to about 270 °C, from about 240 °C to about 260 °C, from about 240 °C to about 250 °C, from about 245 °C to about 300 °C, from about 245 °C to about 290 °C, from about 245 °C to about 280 °C, from about 245 °C to about 270 °C, from about 245 °C to about 260 °C, fromabout 245 °C to about 250 °C, from about 250 °C to about 300 °C, from about 250 °C to about 290 °C, from about 250 °C to about 280 °C, from about 250 °C to about 270 °C, or from about 250 °C to about 260 °C, as measured in accordance with ASTM D92, including any and all sub-ranges formed from any of these endpoints.

[0061] The oils included in the composition of various aspects may also have a relatively low kinematic viscosity (e.g., 105 cSt or less at 40 °C). The kinematic viscosity of the oil is measured in accordance with ASTM D445. In various aspects, the oil has a kinematic viscosity of from about 15 cSt to about 105 cst, from about 15 cSt to about 100 cSt, from about 15 cSt to about 95 cSt, from about 15 cSt to about 90 cSt, from about 15 cSt to about 85 cSt, from about 15 cSt to about 80 cSt, from about 15 cSt to about 75 cSt, from about 15 cSt to about 70 cSt, about 25 cSt to about 105 cst, from about 25 cSt to about 100 cSt, from about 25 cSt to about 95 cSt, from about 25 cSt to about 90 cSt, from about 25 cSt to about 85 cSt, from about 25 cSt to about 80 cSt, from about 25 cSt to about 75 cSt, from about 25 cSt to about 70 cSt, about 35 cSt to about 105 cst, from about 35 cSt to about 100 cSt, from about 35 cSt to about 95 cSt, from about 35 cSt to about 90 cSt, from about 35 cSt to about 85 cSt, from about 35 cSt to about 80 cSt, from about 35 cSt to about 75 cSt, from about 35 cSt to about 70 cSt, about 45 cSt to about 105 cst, from about 45 cSt to about 100 cSt, from about 45 cSt to about 95 cSt, from about 45 cSt to about 90 cSt, from about 45 cSt to about 85 cSt, from about 45 cSt to about 80 cSt, from about 45 cSt to about 75 cSt, from about 45 cSt to about 70 cSt, about 50 cSt to about 105 cst, from about 50 cSt to about 100 cSt, from about 50 cSt to about 95 cSt, from about 50 cSt to about 90 cSt, from about 50 cSt to about 85 cSt, from about 50 cSt to about 80 cSt, from about 50 cSt to about 75 cSt, or from about 50 cSt to about 70 cSt, measured in accordance with ASTM D445 at 40 °C.

[0062] Examples of commercially available oils include those available under the PURETOL™ brand from Petro-Canada (including PURETOL™ 380 and PURETOL™ 550), the DURASYN® brand from Ineos Oligomers (including DURASYN® 170), and the PURENOVA® brand from Novvi, LLC (including PURENOVA® 2609).

[0063] In any of the aspects described herein, the oil is included in the composition in an amount of greater than about 20 wt.%, based on a total weight of the composition. In aspects, the oilis included in the composition in an amount of from about 20 wt.% to about 50 wt.%, based on a total weight of the composition. For example, the oil can be included in the composition in an amount of from about 20 wt.% to about 50 wt.%, from about 25 wt.% to about 50 wt.%, from about 30 wt.% to about 50 wt.%, from about 35 wt.% to about 50 wt.%, from about 40 wt.% to about 50 wt.%, from about 45 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%, from about 25 wt.% to about 45 wt.%, from about 30 wt.% to about 45 wt.%, from about 35 wt.% to about 45 wt.%, from about 40 wt.% to about 45 wt.%, from about 20 wt.% to about 40 wt.%, from about 25 wt.% to about 40 wt.%, from about 30 wt.% to about 40 wt.%, from about 35 wt.% to about 40 wt.%, from about 20 wt.% to about 35 wt.%, from about 25 wt.% to about 35 wt.%, or from about 30 wt.% to about 35 wt.%, including any and all ranges and subranges including any of these endpoints.

[0064] In any of the aspects, the amount of oil is added to the composition in a ratio of an amount of the rubber composition to an amount of the oil of from about 1.3: 1 to 0.7: 1. For example, the ratio of the amount of rubber composition to the amount of oil can be from 1.3: 1 to 0.7: 1, from 1.3: 1 to 0.8: 1, from 1.3: 1 to 0.9:1, from 1.3: 1 to 1 : 1, from 1.3:1 to 1.1 : 1, from 1.2: 1 to 0.7:1, from1.2: 1 to 0.8: 1, from 1.2: 1 to 0.9: 1, from 1.2: 1 to 1: 1, from 1.2:1 to 1.1 : 1, from 1.1: 1 to 0.7: 1, from1.1 : 1 to 0.8: 1, from 1.1 : 1 to 0.9: 1, or from 1.1 : 1 to 1 : 1, including any and all ranges and subranges including any of these endpoints. In any of the aspects described herein, the ratio of the amount of rubber composition to the amount of oil in the composition can be approximately 1 :1.Properties and Articles

[0065] In any of the aspects described herein, in addition to the components described hereinabove, one or more additives can be incorporated into the composition. Additives can include, by way of example and not limitation, stabilizers, anti-oxidants, adhesion promoters, biocides, antistatic agents, dispersants, fillers and extenders, lubricants, initiators, pigments, colorants and dyes, release agents, and any other additive known and used in the art.

[0066] While fillers may be employed in certain described herein, it may be advantageous to prepare a composition that does not include fillers. It has been found that fillers, such as for example calcium carbonate, may result in a surface that is more susceptible to permanent marker and inkstaining. In any of the aspects, the amount of filler is added to the composition may be less than 5 wt.%, less than 1 wt.% or less than 0.5 wt.%. In any of the aspects, the composition may be free of fillers. In any of the aspects, the composition may be free of calcium carbonate.

[0067] As described hereinabove, in various aspects, the rubber component can be formed by compounding or otherwise combining the high molecular weight SEBS polymer and the low molecular weight SEBS polymer to produce a rubber component, which is subsequently mixed with the oil and the polyolefin to form the composition. Alternatively, the high molecular weight SEBS polymer and the low molecular weight SEBS polymer can be added independently to the oil and polyolefin to form the composition, without forming a separate rubber component first. The rubber component, the oil, and the polyolefin can be mixed or blended in any suitable way to form the composition. In any of the aspects, the components can be added to an extruder for mixing to form the composition.

[0068] In various aspects, the resultant composition has a complex viscosity (n*) of less than about 150 Pa*s at 0.1 rad / s in the temperature range of 200-250 °C, when measured in accordance with ASTM D4440 using a strain amplitude at or below 5%. Complex viscosity (n*) is a measure of the total resistance to flow as a function of angular frequency and is given by the quotient of the maximum stress amplitude and maximum strain amplitude. For example, the composition may have a complex viscosity of from about 75 Pa*s to about 150 Pa*s, from about 75 Pa*s to about 140 Pa*s, from about 75 Pa*s to about 130 Pa*s, from about 75 Pa*s to about 120 Pa*s, from about 75 Pa*s to about 110 Pa*s, from about 75 Pa*s to about 100 Pa*s, from about 75 Pa*s to about 95 Pa*s, from about 85 Pa*s to about 150 Pa*s, from about 85 Pa*s to about 140 Pa*s, from about 85 Pa*s to about 130 Pa*s, from about 85 Pa*s to about 120 Pa*s, from about 85 Pa*s to about 110 Pa*s, from about 85 Pa*s to about 100 Pa*s, from about 85 Pa*s to about 95 Pa*s, from about 95 Pa*s to about 150 Pa*s, from about 95 Pa*s to about 140 Pa*s, from about 95 Pa*s to about 130 Pa*s, from about 95 Pa*s to about 120 Pa*s, from about 95 Pa*s to about 110 Pa*s, or from about 95 Pa*s to about 100 Pa*s, including any and all ranges and subranges including any of these endpoints, at 0.1 rad / s in the temperature range of 200-250 °C, when measured in accordance with ASTM D4440 using a strain amplitude at or below 5%.

[0069] In various aspects, the composition can be formed into a plurality of particles via extrusion, which can then be ground, milled, or otherwise processed to form minipellets, micropellets, pellets cryopowder, or the like. In some aspects described herein, the composition can be formed into micropellets via the extrusion process. In aspects, the particles may be formed by a cryogrinding process in which the extruded composition is ground into a powder, submerged in cryogenic liquid, then milled. In some aspects, the particles may be screened to obtain a polymeric material having an average particle size of less than about 1,000 pm, less than about 600 pm, or even less than 500 pm. In aspects, the particles of the composition may be screened using a size 35 mesh screen, although screens of other sizes may be employed depending on the desired particle size.

[0070] The pellets and / or powder can be used in extrusion or molding processes to form a molded or extruded article. Subsequent extrusion or molding processes are well known to those skilled in the art of thermoplastics polymer engineering. Without undue experimentation but with such references as “Extrusion, The Definitive Processing Guide and Handbook”; “Handbook of Molded Part Shrinkage and Warpage”; “Specialized Molding Techniques”; “Rotational Molding Technology”; and “Handbook of Mold, Tool and Die Repair Welding”, all published by Plastics Design Library (www.williamandrew.com), one may make articles of any conceivable shape and appearance using compounds of any of the aspects described herein. In any of the aspects described herein, the pellets and / or powder can be used to form a rotomolded article.

[0071] In various aspects, a rotomolded article formed from or including the composition of any of the aspects described herein may have a wall thickness of from about 0.5 mm to about 50 mm. For example, the rotomolded article can have a wall thickness of from about 0.5 mm to about 50 mm, from about 0.5 mm to about 45 mm, from about 0.5 mm to about 40 mm, from about 0.5 mm to about 35 mm, from about 0.5 mm to about 30 mm, from about 0.5 mm to about 25 mm, from about 1 mm to about 50 mm, from about 1 mm to about 45 mm, from about 1 mm to about 40 mm, from about 1 mm to about 35 mm, from about 1 mm to about 30 mm, from about 1 mm to about 25 mm, from about 5 mm to about 50 mm, from about 5 mm to about 45 mm, from about 5 mm to about 40 mm, from about 5 mm to about 35 mm, from about 5 mm to about 30 mm, or from about 5 mm to about 25 mm, including any and all ranges and subranges including any of these endpoints.

[0072] In various aspects, the rotomolded article comprises a void therein. For example, a void may be defined by the inner surface of one or more walls of the rotomolded article. In any of the aspects herein, at least a portion of the void may be filled. For example, at least a portion of the void may be filled with a foam material. Additionally or alternatively, at least a portion of the void may remain unfilled.

[0073] The rotomolded article of any of the aspects herein can take any form, such as a bin or container, automotive part, road cone or barrier, toy, sporting equipment, commercial, agricultural or industrial product, or the like. Other articles in other industries are possible and contemplated.

[0074] The general inventive concepts have been described above both generally and with regard to various specific aspects. Although the general inventive concepts have been set forth in what are believed to be exemplary illustrative aspects, a wide variety of alternatives will be apparent to those of skill in the art from reading this disclosure. The general inventive concepts are not otherwise limited, except for those instances when presented in specific claims.EXAMPLES

[0075] The following examples are included for the purposes of illustration, and do not limit the scope of the general inventive concepts described herein.

[0076] The materials provided in Table 1 below were used in the examples described herein.Table 1.

[0077] In the following examples, hardness was measured in accordance with ASTM D2240 and values are reported on the Shore A scale.Example 1

[0078] A benchmark study to evaluate permanent marker cleanability and rotational molding viability was conducted using a blend of SEBS, oil, and polypropylene (25:45:30) and a comparative composition comprising DOWLEX™ 2035 (LLDPE). Injection molded plaques were formed with each material, and a SHARPIE® marker and a PAPERMATE™ ink pen were used to write on each of the plaques. The plaques aged for 48 or 168 hours before cleaning was attempted with WINDEX™. As shown in FIG. 1, the blend of SEBS, oil, and polypropylene (Formulation A; images on the left side of FIG. 1) outperformed the LLDPE (Formulation B; images on the right side of FIG. 1) in the test. Specifically, the plaque made from Formulation A exhibited limited ghosting and / or residual permanent staining after cleaning with WINDEX™. It is believed that the presence of oil was the biggest contributor to permanent marker and ink removal performance. It has also been found that theinclusion of a fdler, such as a calcium carbonate fdler, made permanent marker and ink removal very difficult.Example 2

[0079] Next, a brief ladder study was performed to evaluate various blends of high molecular weight SEBS with a styrene content of about 20 wt.% (KRATON™ G1642HU) with and without KRATON™ G1643M, as well as to explore different PP and oil ratios. In this example, a Shore A hardness of 85 was targeted for the samples. The blends containing the KRATON™ G1643M exhibited lower viscosity. Additionally, the samples containing greater loadings of PP and oil relative to SEBS also demonstrated a lower viscosity. However, attempts at rotomolding samples containing KRATON™ G1643M revealed significant melt-pooling with pockets rich in polypropylene and very poor tear resistance. It was presumed that the di -block content of the KRATON™ G1643M prevented adequate mixing during compounding and was also limiting mechanical performance. Samples containing KRATON™ G1642HU without KRATON™ G1643M performed fairly well, although considerable pitting was observed on the part surface, as shown in FIGS. 2A-2C.

[0080] FIG. 2A is an image of a successfully rotomolded, in-tact part formed from Formula X. Formula X included about 29 wt.% TOTAL™ 3860X, about 33 wt.% KRATON™ G1642HU, and about 33 wt.% PURETOL™ 380. FIG. 2B is a magnified image formed from Formula X demonstrating surface pitting. FIG. 2C is the negative of the image in FIG. 2B, which resolves the pitting in the surface more clearly. Although the parts shown in FIGS. 2A-2C were prepared from Formula X, the specific composition used to prepare the part in FIG. 2A included a different colorant than the composition used to prepare the part in FIGS. 2B and 2C.Example 3

[0081] Without being bound by theory, it is believed that the bubbles or surface pitting in rotational molding results from trapped air / gasses. While bubble dissolution is highly dependent on the size of the gas molecules and the material chemistry, reducing the pitting phenomenon can be achieved by utilizing a lower viscosity material or the application of positive pressure during molding. One way to access a lower viscosity material is to increase the temperature or shear rate at which agiven material is molded. Most polymers follow an exponential decay, represented by the following Equation 1 : 1 7JO= C RT + ln / f (1) where r|o is the material viscosity, Enis the activation energy for viscous flow, T is temperature, and R and K are constants. Since only low shear rates are accessible during rotational molding, a deeper probe into the thermal stability and, specifically, the volatility of the oil was performed.

[0082] It is known that SEBS and PP have a degradation onset temperature of greater than 300 °C, and the limitations in processing temperature for the formulations are often related to the vaporization of the oil. Accordingly, various oils (PURETOL™ 380 (white mineral oil), PURETOL™ 550 (white mineral oil), and DURASYN® 170 polyalphaolefin oil (PAO)) were compared by thermogravimetric analysis (TGA) to determine the onset of vaporization and the total volatility at 230 °C over the course of 30 minutes. The results are shown in FIGS. 3A and 3B.

[0083] The TGA data clearly shows that the PAO selected would offer reduced volatility at higher temperatures, and would allow for higher processing temperatures to be utilized. To test this concept, pellets were formulated from a composition comprising about 31 wt.% KRATON™ G1642HU, about 38 wt.% TOTAL™ 3860X, and about 31 wt.% DURASYN® 170 and placed on a hot plate at different temperatures (170 °C, 180 °C, and 190 °C) for approximately 15 minutes. As shown in FIG. 3C, the appearance of pitting on the surface in contact with the plate appeared to diminish with increasing temperature. Accordingly, the hot plate test appeared to demonstrate a potential formulation that would be successful in eliminating bubbles at a processing temperature of > 190 °C.Example 4

[0084] To more closely mimic the rotational molding process, a SUPERDANNY® rotisserie oven and paint cans were utilized to simulate a rotational molding tool. The rotisserie was rotated at 6 rpm, and the oven temperature was adjustable up to 230 °C, with an option for “dehydration” thatacted as a cooling cycle with a minimum temperature of 50 °C with continual rotation. FIG. 4A shows an image of this experimental setup.

[0085] To prepare the parts, various formulations were prepared as set forth in Table 3 below. Amounts reported in Table 3 are in weight percent (wt.%) based on a total weight of the composition. After blending, the material prepared from each formulation was cryogenically frozen and ground using a high-speed spice grinder and passed through a 30-mesh sieve. Approximately 60-90 grams of the powder was loaded into a 1 qt. paint can and rotated at temperatures between 190-230 °C for 25- 35 minutes, then cooled under rotation until the oven reached an internal temperature of 50 °C.Table 3.

[0086] Tear resistance was measured in accordance with ASTM D624. Tensile strength was measured in accordance with ASTM D412, die C. Tensile elongation was measured in accordance with ASTM D412, die C. Viscosity is the complex viscosity and is measured in accordance with ASTM D4440 at 0.1 rad / s and 200 °C, using a strain amplitude of 1%, except for Formula I, which was measured at 240 °C. Surface pitting refers to visual observation of the surface for the rotationally molded parts prepared. FIGS. 4B and 4C are photographs of the part molded from Formula I. As seen in FIGS. 4B and 4C, the part prepared from Formula I included minor surface pitting.

[0087] Earlier findings suggested that the incorporation of di-block would be detrimental to mechanical performance, so reducing the order-disorder transition (ODT) temperature was explored. Specifically, it was hypothesized that incorporating a low polystyrene content SEBS with a lower overall molecular weight could reduce the ODT temperature and allow access to lower viscosities at lower shear rates (e g., 0.1 rad / s). A ladder study was performed which in low flow KRATON™ G1642HU was incrementally replaced with high flow KRATON™ MD 1648V, and the ODT was measured using temperature sweeps on a parallel plate rheometer. The ratio of the KRATON™ grades for each of the formulations used in the ladder study are reported in Table 4 below. Each formulation reported in Table 4 also included 100 phr TOTAL™ 3860X and 100 phr PURETOL™ 550 oil. Formulation N could not be pelletized, so only Formulas O-R were evaluated.Table 4.

[0088] The SAGS temperature sweeps at 1% strain, 0.5 rad / s for Formulas O-R are shown in FIG. 5A. From the peak in tan(8) following the glass transition, it was observed that increasing the content of the high flow SEBS could shift the ODT from greater than 230 °C (Formula R) down to approximately 160 °C (Formula O).

[0089] The SAGS temperature sweeps at 1% strain for Formula P at various temperatures (170 °C, 180 °C, 190 °C, and 200 °C) are shown in FIG. 5B along with temperature sweeps at 1% strain for Formula I at 240 °C. As shown in FIG. 5B, the utility of the shifting of the ODT is shown as comparable low shear viscosities were achieved at 190 °C for Formula P as compared to 240 °C for Formula I.

[0090] The formulations prepared in Table 4 further demonstrated that when a tri-block copolymer of SEBS was used instead of a di-block for promoting flowability, the mechanical properties were substantially preserved. For example, the tear resistance of Formula P was only reduced by about 7.5%, and the tensile strength decreased approximately 5% relative to Formula R.The largest property change was a decrease in elongation from 500% (Formula R) to 400% (Formula P). However, gaining access to viscosities of less than or equal to 100 Pa*s at 0.1 rad / s appeared to be necessary for producing a pit-free finish.

[0091] Every document cited herein is incorporated herein by reference in its entirety unless otherwise specified. The citation of any document is not to be construed as an admission that it is prior art with respect to any invention disclosed or claimed herein. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0092] It will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

Claims

CLAIMSWhat is claimed is:

1. A composition comprising: a rubber component comprising:(i) a high molecular weight styrene-ethylene-butylene-styrene (SEBS) polymer having a number average molecular weight of from 75,000 g / mol to 300,000 g / mol; and(ii) a low molecular weight SEBS polymer having a polystyrene content of less than about 30 wt.% and a number average molecular weight of from 10,000 g / mol to less than 75,000 g / mol; a polyolefin; and an oil.

2. The composition of claim 1, wherein the composition has a complex viscosity of less than 100 Pa*s at 0.1 rad / s in the temperature range of 200-250 °C, when measured in accordance with ASTM D4440 using a strain amplitude at or below 5%.

3. The composition of claim 1 or claim 2, wherein the low molecular weight SEBS polymer is a tri -block SEBS polymer.

4. The composition of claim 3, wherein the tri-block SEBS polymer comprises an ethylene / butylene mid-block and one or more styrene-containing end blocks.

5. The composition of any preceding claim, wherein the polyolefin comprises a polypropylene homopolymer, a polypropylene random copolymer, a high density polyethylene (HDPE), a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE), and combinations thereof.

6. The composition of any preceding claim, wherein the polyolefin comprises a polyethylene having a melt flow index of greater than or equal to 40 g / 10 min, as measured in accordance with ASTM D1238 at 190 °C and 2.16 kg.

7. The composition of any one of claims 1-5, wherein the polyolefin comprises a polypropylene having a melt flow index of greater than or equal to 50 g / 10 min, as measured in accordance with ASTM D1238 at 230 °C and 2.16 kg.

8. The composition of any preceding claim, wherein the oil is present in an amount of greater than or equal to about 20 wt.%, based on a total weight of the composition.

9. The composition of any preceding claim, wherein the oil comprises a polyalphaolefin (PAO) or mineral oil.

10. The composition of any preceding claim, wherein the oil comprises a bio-derived oil.

11. The composition of any preceding claim, wherein the oil has a flashpoint of greater than about 230 °C, as measured in accordance with ASTM D92.

12. The composition of any preceding claim, wherein the oil has a kinematic viscosity of less than or equal to 105 cSt as measured in accordance with ASTM D445 at 40 °C.

13. The composition of any preceding claim, wherein the high molecular weight SEBS polymer has a number average molecular weight of from 75,000 g / mol to 125,000 g / mol.

14. The composition of any preceding claim, wherein the low molecular weight SEBS polymer has a number average molecular weight of 40,000 g / mol to 70,000 g / mol.

15. The composition of any preceding claim, wherein the low molecular weight SEBS polymer has a number average molecular weight of 55,000 g / mol to 65,000 g / mol.

16. The composition of any preceding claim, wherein a ratio of an amount of the rubber composition to an amount of the oil is 1 :1.

17. The composition of any preceding claim, wherein a ratio of an amount of the high molecular weight SEBS polymer to an amount of the low molecular weight SEBS polymer is from 1.1 : 1 to 1.5: 1.

18. The composition of any preceding claim, wherein the composition is formed into a plurality of particles having an average particle size of less than about 1,000 pm.

19. The composition of claim 18, wherein the composition is formed into the plurality of particles through cryogrinding.

20. The composition of claim 18, wherein the plurality of particles comprises a plurality of micropellets.

21. A rotomolded article comprising the compound of any preceding claim.

22. The rotomolded article of claim 21, wherein the rotomolded article has a wall thickness of from about 0.5 mm to about 50 mm.

23. The rotomolded article of claim 21 or claim 22, wherein the rotomolded article comprises a void therein.

24. A process for forming a product comprising: forming a rotomolded article by rotomolding a composition comprising: a rubber component comprising:(i) a high molecular weight styrene-ethylene-butylene-styrene (SEBS) polymer having a number average molecular weight of from 75,000 g / mol to 300,000 g / mol; and(ii) a low molecular weight SEBS polymer having a polystyrene content of less than about 30 wt.% and a number average molecular weight of from 10,000 g / mol to 75,000 g / mol; a polyolefin; and an oil.

24. The process of claim 23, further comprising at least partially filling a void in the molded article with foam.

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