OA19433A - Thermoplastic compositions, methods, apparatus, and uses. - Google Patents

Abstract

Thermoplastic polyurethane (TPU) compositions, methods for producing TPU compositions, methods of using TPU compositions, and apparatuses produced therefrom are disclosed. Disclosed TPU compositions include a thermoplastic polyurethane polymer, a heat stabilizer, a flow agent, and a filler material. The filler may be a glass fiber. Disclosed TPU compositions have improved thermal stability and improved flow properties suitable for injection molding of articles of manufacture having a large plurality of fine openings or pores. Articles produced from the composition have superior thermal stability, abrasion resistance, and chemical resistance. Example articles include screening members for vibratory screening machines.

Description

[0011] This disclosure generally relates to compositions, apparatus, methods, and uses of thermoplastic polyuréthanes (TPU). Disclosed embodiment TPU compositions may be used in injection molding processes to generate screening members for use in vibratory screening machines. Vibratory screening machines provide a capability to excite an installed screen such that materials placed upon the screen may be separated to a desired level. Oversized materials are separated from undersized materials. The disclosed compositions and screening members may be used in technology areas related to the oil industry, gas/oil séparation, mining, water purification, and other related industrial applications.

[0012] Disclosed embodiments provide screening members that satisfy demanding requirements, such as: fine openings of approximately 43 pm to approximately 100 pm that effectively screen similar-sized particles; large area screens on the order of several square feet having large open screening area on the order of 30% to 35%; screens that are thermally and mechanically stable that can withstand severe conditions during operation, such as compression loading (e.g. forces from 1,500 Ibs. to 3,000 Ibs. applied to edges of screening members and vibrational accélérations of up to 10 G) and loading of high température materials (e.g. between 37° C and 94° C), with significant weight loads and severe Chemical and abrasive conditions of the materials being screened.

[0013] Disclosed embodiment materials and methods provide a hybrid approach in which small screening éléments are micro-molded using disclosed TPU materials to reliably generate fine features on the order of 43 pm to approximately 100 pm to yield screening éléments having large open screening area. The disclosed TPU materials, as discussed in more detail below, include embodiments that feature optimized amounts of filler, heat stabilizer, and flow agent as additives to the appropriate thermoplastic polyuréthane. These additives in turn allow for the small screen éléments to be attached securely, such as via laser welding, to the subgrid structures to provide mechanical stability that may withstand the large mechanical loading and accélérations mentioned above. For example, glass fibers may be used as filler material, which allow for strengthening of the TPU material and in turn allow the screen éléments to be securely attached to the subgrid structures with increased structural stability. However, addition of large amounts of glass fibers may lead to increased difficulty in laser welding, given that the refractive properties of the glass provide obstacles to the laser Systems. Any amount of additive will also necessarily require dilution of the thermoplastic urethane. Similarly, a minimal but effective amount of heat stabilizer should be added, wherein the additive should be of sufficient amount to allow the end structure to withstand the addition of high-temperature materials as described above.

[0014] As discussed in more detail below, the amount of additives in the disclosed TPU compositions may also be varied based on the desired thickness T of the screening element surface éléments, as discussed in detail in U.S. Patent Application Nos. 15/965,195 and 62/648,771, which are hereby incorporated by reference herein. For example, as discussed in U.S. Patent Application No. 15/965,195 in Paragraphe [00366] to [00373] and corresponding Tables 1 to 4, the thickness T of the screening element surface éléments may be varied in an effort to maximize the percentage of open area on the overall screen assembly, which allows for increased effectiveness of the screening assembly when in use.

[0015] A plurality of these optimized subgrid structures may then be assembled into screening structures having large surface areas, on the order of several square feet. The screen assemblies based on the disclosed TPU compositions may be utilized, for example, in the manner described in U.S. Patent Application Nos. 15/965,195 and 62/648,771. For example, as outlined in U.S. Patent Application No. 15/965,195 in Paragraphe [0017] to [0021] ofthe Spécification, the grid framework based upon the disclosed TPU compositions may provide the required durability against damage or deformation under the substantial vibratory load burdens it is subjected to when secured to a vibratory screening machine. The subgrids, when assembled to form the complété screen assembly, are strong enough not only to withstand the forces required to secure the screen assembly to the vibratory screening machine, but also to withstand the extreme conditions that may be présent in the vibratory loading. As discussed in detail in Paragraphs [00280] to [00282] ofthe Spécification ofU.S. Patent Application No. 15/965,195, a preferred method of securing the screen éléments to the subgrid may include laser welding of the fusion bars arranged on the subgrids. The disclosed TPU compositions may therefore be utilized to create the referenced vibratory screening apparatus, capable of withstanding the extreme conditions discussed herein and in U.S. Patent Application No. 15/965,195.

[0016] Screen assemblies based on disclosed TPU compositions may also be configured to be mounted on vibratory screening machines described in U.S. Patent Nos. 7,578,394;

5,332,101; 6,669,027; 6,431,366; and 6,820,748. Such screen assemblies may include: side portions or binder bars including U-shaped members configured to receive over mount type tensioning members, as described in U.S. Patent No. 5,332,101; side portions or binder bars including finger receiving apertures configured to receive under mount type tensioning, as described in U.S. Patent No. 6,669,027; side members or binder bars for compression loading, as described in U.S. Patent No. 7,578,394; or may be configured for attachment and loading on multi-tiered machines, such as the machines described in U.S. Patent No. 6,431,366.

[0017] Screen assemblies and/or screening éléments based on disclosed TPU compositions may also be configured to include features described in U.S. Patent 8,443,984, including the guide assembly technologies described therein and preformed panel technologies described therein. Still further, screen assemblies and screening éléments based on disclosed TPU compositions may be configured to be incorporated into pre-screening technologies, compatible with mounting structures and screen configurations, described in U.S. Patent Nos. 7,578,394; 5,332,101; 4,882,054; 4,857,176; 6,669,027; 7,228,971; 6,431,366; 6,820,748; 8,443,984; and 8,439,203. The disclosure of each of these patent documents, along with their related patent families and applications, and the patents and patent applications referenced in these documents, are expressly incorporated herein by reference in their entireties.

Example Screen Embodiments

[0018] Screening members fabricated from thermosetting and thermoplastic polymers are described in the above referenced patent documents (i.e., U.S. Provisional Patent Application Serial Nos. 61/652,039 and 61/714,882; U.S. Patent Application No. 13/800,826; U.S. Patent No. 9,409,209; U.S. Patent No. 9,884,344; and U.S. Patent Application No. 15/851,099), the disclosures of which are incorporated herein by reference in their entireties.

[0019] FIGS. 1 to 3A illustrate example embodiment screening members generated by injection molding processes using disclosed TPU compositions. FIGS. 1 to IC show an embodiment screen element 416 having substantially parallel screen element end portions 20, and substantially parallel screen element side portions 22, that are substantially perpendicular to the screen element end portions 20. Screen element 416 may include a plurality of tapered counter bores 470, which may facilitate extraction of screen element 416 from a mold, as described in greater detail in the above-referenced patent documents. Screen element 416 may further include location apertures 424, which may be located at a center of screen element 416 and at each of the four corners of screen element 416. Location apertures 424 are useful for attaching screen element 416 to subgrid structures, as described in greater detail below with reference to FIGS. 3 and 3A.

[0020] As shown in FIGS. 1 and IA, screen element 416 has a screening surface 13 that includes solid surface éléments 84 running parallel to the screen element end portions 20 and forming screening openings 86, as also shown in the close-up view of FIG. 2, as described in greater detail below.

[0021] FIGS. IB and IC show a bottom view of screen element 416 having a first screen element support member 28 extending between the end portions 20 and being substantially perpendicular to the end portions 20. FIG. IB also shows a second screen element support member 30 perpendicular to the first screen element support member 28 extending between the side edge portions 22, being approximately parallel to the end portions 20 and being substantially perpendicular to the side portions 22. The screen element may further include a first sériés of reinforcement members 32 substantially parallel to the side edge portions 22, and a second sériés of reinforcement members 34 substantially parallel to the end portions 20. The end portions 20, the side edge portions 22, the first screen element support member 28, the second screen element support member 30, the first sériés reinforcement members 32, and the second sériés of reinforcement members 34, structurally stabilize the screen surface éléments 84 and screening openings 86 during various loadings, including distribution of a compression force and/or vibratory loading conditions.

[0022] As shown in FIGS. IB andlC, screen element 416 may include one or more adhesion arrangements 472, which may include a plurality of extensions, cavities, or a combination of extensions and cavities. In this example, adhesion arrangement 472 is a plurality of cavity pockets. Adhesion arrangement 472 is configured to mate with complementary adhesion arrangements of a subgrid structure. For example, subgrid structure 414 (shown in FIGS. 3 and 3A) has a plurality of fusion bars, 476 and 478, that mate with cavity pockets 472 of screen element 416, as described in greater detail below with reference to FIGS. 3 and 3A.

[0023] As illustrated in FIG. 2, the screening openings 86 may be elongated slots having a length L, and width W, separated by surface éléments 84 hâve a thickness T. Thickness T may be varied depending on the screening application and configuration ofthe screening openings 86. Thickness T may be chosen to be approximately 0.003 inches to about 0.020 inches (i.e., about 76 pm to about 508 pm), depending on the open screening area desired, and the width W of screening openings 86. In an exemplary embodiment, the thickness T ofthe surface éléments may be 0.015 inches (i.e., 381 pm). However, properties of disclosed TPU compositions allow formation of thinner surface éléments, such as surface éléments having a thickness T of 0.007 inches (i.e., 177.8 pm). The smaller the thickness, T, of the surface éléments, the larger the screening area of the screen element. For example, a thickness T of 0.014 inches will provide a screen element that is about 10-15% open, while a thickness T of 0.003 inches will provide a screen element that is about 30-35% open, thus increasing open screening area.

[0024] As mentioned above, screening openings 86 hâve a width W. In exemplary embodiments, the width W may be approximately 38 pm to approximately 150 pm (i.e., about 0.0015 to about 0.0059 inches) between inner surfaces of each screen surface element 84. The length-to-width ratios ofthe openings may be from 1:1 (i.e. corresponding to round pores) to 120:1 (i.e., long narrow slots). In exemplary embodiments, openings may preferably be rectangular and may hâve a length-to-width ratio of between about 20:1 (e.g. length 860 pm; width 43 pm) to about 30:1 (i.e., length about 1290 pm, and width about 43 pm). The screening openings are not required to be rectangular but may be thermoplastic injection molded to include any shape suitable to a particular screening application, including approximately square, circular, and/or oval.

[0025] As described in greater detail below, for increased stability, the screen surface éléments 84 may include intégral fiber materials (e.g., glass fibers) which may run substantially parallel to end portions 20. Screen element 416 may be a single thermoplastic injection molded piece. Screen element 416 may also include multiple thermoplastic injection molded pièces, each configured to span one or more grid openings. Utilizing small thermoplastic injection molded screen éléments 416, which are attached to a grid framework as described below, provides substantial advantages over prior screen assemblies, as described in greater detail in the abovereferenced patent documents.

[0026] FIGS. 3 and 3A illustrate a process for attaching screen éléments 416 to an end subgrid unit 414, according to an embodiment. Screen éléments 416 may be aligned with end subgrid unit 414 via elongated attachment members 444 (of subgrid 414) that engage with location apertures 424 on an underside of the screen element 416 (e.g., see Figures 1 to IC). In this regard, elongated attachment members 444 of subgrid 414 pass into screen element location apertures 424 of screen element 416. Elongated attachment members 444 of end subgrid 414 may then be melted to fill tapered bores of screen element attachment apertures 424, to thereby secure screen element 416 to the subgrid unit 414. Attachment via elongated attachment members 444 and screen element location apertures 424 is only one method for attaching screen member 416 to subgrid 414.

[0027] Altematively, screen element 416 may be secured to end subgrid unit 414 using adhesives, fasteners and fastener apertures, laser welding, etc. As described above, fusion bars 476 and 478, of subgrid 414 (e.g., see FIGS. 3 and 3A), may be configured to fit into cavity pockets 472 of screen element 416 (e.g., see FIGS. 1 to 3C). Upon application of heat (e.g., via laser welding, etc.), fusion bars, 476 and 478, may be melted to form a bond between screen element 416 and subgrid 414 upon cooling.

[0028] Arranging the screen éléments 416 on subgrids (e.g., subgrid 414), which may also be thermoplastic injection molded, allows for easy construction of complété screen assemblies with very fine screening openings. Arranging screen éléments 416 on subgrids also allows for substantial variations in overall size and/or configuration of the screen assembly 10, which may be varied by including greater or fewer subgrids or subgrids having different shapes, etc.

Moreover, a screen assembly may be constructed having a variety of screening opening sizes or a gradient of screening opening sizes simply by incorporating screen éléments 416 with the different size screening openings onto subgrids and joining the subgrids to form a desired configuration.

[0029] The screens described above with reference to Figures 1 to 3, and disclosed in the above-reference patent documents, hâve small screening openings suitable for use as screening members. The disclosed TPU compositions additionally allow these screens to perform effectively in each of the following key areas: structural stability and durability; ability to withstand compression type loading; ability to withstand high températures; extended commercial life despite potential abrasion, cuts, or tearing; and fabrication methods that are not overly complicated, time consuming, or error-prone.

[0030] There is thus a need for improved TPU compositions having improved Chemical properties that may be formed by injection molding into screening members and screening assemblies having improved physical properties.

[0031] Disclosed compositions generally include a TPU material, a heat stabilizer selected to optimize heat résistance of the composition, a flow agent selected to optimize use of the composition in injection molding, and a filler material selected to optimize rigidity of the resulting composite material. The filler may be included in an amount of less than about 10% by weight of the TPU. In one embodiment, the filler is provided in an amount of about 7% by weight of the TPU. In other exemplary embodiments, the filler is provided in amounts of less than about 7%, less than about 5%, or less than about 3%, of the weight of the TPU.

[0032] One example of a filler material includes glass fibers. Glass fibers may be introduced in an amount that allows use of the composition in injection molding, improves rigidity of the composition upon hardening, increases température résistance of the final product, and yet does not preclude laser welding of the composition to other materials.

[0033] An initial length of glass fibers may be between about 1.0 mm to about 4.0 mm. In an embodiment, glass fibers hâve an initial length of about 3.175 mm (i.e., 1/8 inch). Glass fibers may also hâve a diameter of less than about 20 pm, such as between about 2 pm and about 20 pm. In one exemplary embodiment, the glass fibers hâve a diameter of between about 9 pm to about 13 pm.

[0034] The TPU material may be made from a low free isocyanate monomer prepolymer. In an example embodiment, the low free isocyanate monomer prepolymer may be chosen to be pphenylene di-isocyanate. In further embodiments, other prepolymers may be chosen. The TPU may first be generated by reacting a urethane prepolymer with a curing agent. The urethane prepolymer may be chosen to hâve a free polyisocyanate monomer content of less than 1 % by weight.

[0035] The resulting material may then be thermally processed by extrusion at températures of 150° C, or higher, to form the TPU polymer. The urethane prepolymer may be prepared from a polyisocyanate monomer and a polyol including an alkane diol, polyether polyol, polyester polyol, polycaprolactone polyol, and/or polycarbonate polyol. In an example embodiment, the curing agent may include a diol, a triol, a tetrol, an alkylene polyol, a polyether polyol, a polyester polyol, a polycaprolactone polyol, a polycarbonate polyol, a diamine, or a diamine dérivative.

[0036] According to an embodiment, the heat stabilizer, mentioned above, may be included in an amount of about 0.1% to about 5% by weight of the TPU. The heat stabilizer may be a sterically hindered phenolic antioxidant. The sterically hindered phenolic antioxidant may be pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (CAS Registry No. 6683-19-8). Optionally, an ultraviolet (UV) light stabilizer may be included. In some embodiments, the heat stabilizer will also serve as a UV light stabilizer.

[0037] According to an embodiment, the flow agent, mentioned above, may be included in an amount of about 0.1% to about 5% by weight ofthe TPU. The flow agent may be chosen to be an ethylene steramide wax. The ethylene steramide wax may include octadecanamide, N,N'1,2-ethanediylbis (CAS Registry No. 110-30-5) and stearic acid (CAS Registry No. 57-11-4). In other embodiments, other flow agents may be chosen.

[0038] According to an embodiment, glass fibers, mentioned above, may hâve a diameter or width between about 2 to about 20 pm, between about 9 to about 13 pm, or may hâve a diameter or width about 11 pm. The glass fibers may hâve an initial length of between about 3.1 mm to about 3.2 mm. A final average length of the glass fibers, in a hardened State after injection molding, may be less than about 1.5 mm due to breakage of fibers during processing. In a final hardened State after injection molding, the fibers may be characterized by a distribution of lengths ranging from about 1.0 mm to about 3.2 mm, with some fibers remaining unbroken.

[0039] Disclosed embodiments include methods of making and using TPU compositions suitable for use in injection molding of articles of manufacture having fine pores. Embodiment methods include reacting a TPU, a heat stabilizer, a flow agent, and a filler material, at a température greater than about 150° C, to generate a TPU composition. The filler may include a glass fiber having a diameter of between about 2 pm to about 20 pm, in an amount selected to optimize rigidity of articles of manufacture molded from the TPU composition. The TPU may be polycarbonate TPU. The TPU may be a pre-polymer prior to the reacting step. The glass fiber may be présent in an amount between about l% to about 10% by weight of the TPU. In one embodiment, the glass fiber may be présent in an amount of about 7% by weight of the TPU.

[0040] Articles of manufacture molded from compositions disclosed herein are suitable to be joined by various methods including laser welding. In this regard, the resulting articles may be laser welded to other articles, such as support structures.

[0041] Example articles of manufacture include screening members for vibratory shaker screens, as described above. Disclosed TPU material, described above, may then be used in an injection molding process to generate a screening member. In this regard, the TPU material may be introduced/injected into a suitably designed mold at an elevated température. The température may be chosen to be a température at which the TPU material has a sufficiently reduced viscosity to allow the material to flow into the mold. Upon cooling, the resulting solidified screening member may be removed from the mold.

[0042] The resulting screening member may be designed to hâve a plurality of openings having opening widths ranging from about 38 pm to about 150 pm. Screens with such openings may be used for removing particles from various industrial fluids to thereby filter/clean the fluids. Particles that are larger than widths of screening openings may be effectively removed. The désirable thermal properties of the TPU material allows screening members made from the TPU material to effectively screen particles at elevated températures (e.g., service températures of up to about 82 to 94° C).

[0043] Characteristics of disclosed TPU compositions, and products generated therefrom, include température and flow characteristics that facilitate production of very fine, highresolution structures using techniques such as injection molding. Resulting end products also hâve excellent thermal stability at elevated operating températures (e.g. up to about 94° C). Resulting structures also exhibit sufficient structural rigidity to withstand compression loading while maintaining small openings that allow for screening of micron-scale particulate matter. Structures generated from disclosed TPU materials also exhibit eut, tear, and abrasion résistance, as well as Chemical résistance in hydrocarbon-rich environments (e.g. environments including hydrocarbons such as diesel fuel).

Thermoplastic Polyuréthanes

[0044] Disclosed embodiments provide thermoplastic compositions including polyuréthanes, which are a class of macromolecular plastics known as polymers. Generally, polymers, such as polyuréthanes, include smaller, repeating units known as monomers. Monomers may be chemically linked end-to-end to form a primary long-chain backbone molécule with or without attached side groups. In an example embodiment, polyuréthane polymers may be characterized by a molecular backbone including carbonate groups (-NHCO2), for example.

[0045] While generally categorized as plastics, thermoplastic compositions include polymer chains that are not covalently bonded, or crossed linked, to one another. This lack of polymer chain crosslinking allows thermoplastic polymers to be melted when subjected to elevated températures. Moreover, thermoplastics are reversibly thermoformable, meaning that they may be melted, formed into a desired structure, and re-melted in whole or in part at a later time. The ability to re-melt thermoplastics allows optional downstream processing (e.g., recycling) of articles generated from thermoplastics. Such TPU based articles may also be melted at discrète locations by applying a heat source to a spécifie location on an article. In this regard, articles generated from disclosed TPU composition are amenable to joining using welding (e.g., laser welding) to effectively secure TPU-based screening members to suitable screening frames.

[0046] Disclosed TPU materials exhibit désirable properties under extreme conditions of température and harsh Chemical environments. In exemplary embodiments, such TPU materials may be made from a low free isocyanate monomer (LF) prepolymer. An example (LF) prepolymer may include a p-phenylene di-isocyanate (PPDI) with low free isocyanate content. In other embodiments, different suitable prepolymers may be used.

[0047] Example TPU materials may be generated as follows. A TPU polymer may be produced by reacting a urethane prepolymer, having a free polyisocyanate monomer content of less than 1% by weight, with a curing agent. The resulting material may then be thermally processed by extrusion at températures of 150° C (or higher) to form the TPU material. The urethane prepolymer may be prepared from a polyisocyanate monomer and a polyol including an alkane diol, a polyether polyol, a polyester polyol, a polycaprolactone polyol, and/or a polycarbonate polyol. The curing agent may include a diol, a triol, a tetrol, an alkylene polyol, a polyether polyol, a polyester polyol, a polycaprolactone polyol, a polycarbonate polyol, a diamine, or a diamine dérivative.

[0048] Disclosed TPU materials may then be combined with a heat stabilizer, a flow agent, and a filler material, according to varions embodiments. In further embodiments, other additives may be included as needed.

[0049] Generally, disclosed embodiments provide TPU compositions that may be formed by reacting a polyol with a polyisocyanate and polymer chain-extender. Example embodiments include synthetic production methods and processes for making TPU compositions. Disclosed methods may include reacting monomers, curing agents, and chain extenders in a reaction vessel to form pre-polymers. Disclosed methods may further include forming pre-polymers by reacting a di-isocyanate (OCN-R-NCO) with a diol (HO-R-OH). Formation of a pre-polymer includes chemically linking two reactant molécules to produce a Chemical product having an alcohol (OH) at one position and an isocyanate (NCO) at another position of the product molécule. In an embodiment, a disclosed pre-polymer includes both a reactive alcohol (OH) and a reactive isocyanate (NCO). Articles generated using the TPU compositions disclosed herein may be fully cured polymer resins that may be stored as a solid plastic.

[0050] Disclosed embodiments provide pre-polymers that may be prepared from a polyisocyanate monomer and a curing agent. Non-limiting examples of curing agents may include ethane diol, propane diol, butane diol, cyclohexane dimethanol, hydroquinone-bishydroxyalkyl (e.g., hydroquinone-bis-hydroxyethyl ether), diethylene glycol, dipropylene glycol, dibutylene glycol, triethylene glycol, etc., dimethylthio-2,4-toluenediamine, di-p-aminobenzoate, phenyldiethanol amine mixture, methylene dianiline sodium chloride complex, etc.

[0051] In example embodiments, a polyol may include an alkane diol, polyether polyol, polyester polyol, polycaprolactone polyol, and/or polycarbonate polyol. In certain embodiments, the polyol may include a polycarbonate polyol either, alone or in combination with other polyols.

Heat stabilizers

[0052] Disclosed heat/thermal stabilizers may include additives such as organosulfur compounds, which are efficient hydroperoxide decomposers that thermally stabilize polymers. Non-limiting example heat stabilizers include: organophosphites such as triphenyl phosphite, tris-(2,6-dimethylphenyl) phosphite, tris-(mixed mono-and di-nonylphenyl) phosphite etc.; phosphonates such as dimethylbenzene phosphonate, etc.; phosphates such as trimethyl phosphate, etc.; dihexylthiodiformate dicyclohexyl-10,10'-thiodidecylate dicerotylthiodiformate dicerotyl-10, l O'-thiodidecylate dioctyl-4,4-thiodibutyrate diphenyl-2,2'-thiodiacetate (thiodiglycolate) dilauryl-3,3'-thiodipropionate distearyl-3,3'-thiodipropionate di(p-tolyl)-4,4'thiodibutyrate lauryl myristyl-3,3'-thiodipropionate palmityl stearyl-2,2'-thiodiacetate dilauryl-2methyI-2,2'-thiodiacetatedodecyl 3-(dodecyloxycarbonylmethylthio) propionate stearyl 4(myristyloxycarbonylmethylthio) butyrate diheptyl-4,4-thiodibenzoate dicyclohexyl-4,4'thiodicyclohexanoate dilauryl-5,5'-thio-4-methylbenzoate; and mixtures thereof etc. When présent, thermal stabilizers may be included in amounts of about 0.0001% to about 5% by weight, based on the weight of the base-polymer component used in the TPU composition. Inclusion of organosulfur compounds may also improve thermal stability of TPU compositions as well as articles produced therefrom.

[0053] In an exemplary embodiment, a heat stabilizer may be a sterically hindered phenolic antioxidant, such as Pentaerythritol Tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (CAS Registry No. 6683-19-8). In example embodiments, the heat stabilizer may be included in amounts ranging from about 0.1% to about 5% by weight of the TPU.

Flow agents

[0054] Flow agents are used to enhance flow characteristics of TPU materials so that such TPU materials may be easily injected into a mold. Injection times for disclosed TPU materials are preferably between about 1 to about 2 seconds. In an embodiment, flow times averaging about 1.6 seconds hâve been achieved. Flow agents are used to achieve such injection times.

[0055] Disclosed TPU compositions may include flow agents that improve lubrication to increase the flow of melted polymer compositions relative to an external surface (i.e., to increase external flow). Flow agents may also increase the flow of individual polymer chains within a thermoplastic melt (i.e., to increase internai flow).

[0056] Disclosed embodiments provide TPU compositions that may include an internai flow agent that may be readily compatible with the polymer matrix. For example the internai flow agent may hâve a similar polarity that improves the ease of flow of the melt by preventing internai friction between the individual particles of the polymer. In certain embodiments, TPU compositions including internai flow agents may improve molding characteristics. For example, in a spécifie embodiment, TPU compositions may be used to produce articles having small or very small openings. In another embodiment, TPU compositions may be used to produce articles having very fine openings by injection molding. In further embodiments, the improved flow of the TPU compositions allows production of high-resolution articles having small or very small openings.

[0057] Disclosed embodiments provide TPU compositions that may include an extemal flow agent that may be more or less compatible with the polymer matrix of a TPU composition. For example, an extemal flow agent may hâve a different polarity relative to the TPU composition polymer. Since external flow agents may not be compatible with the TPU polymer matrix of the composition, extemal flow agents may act as an extemal lubricating film between the polymer and hot metallic surfaces of processing machines. Thus, extemal lubricants may prevent a polymer melt from adhering to machine parts (e.g., such as an extruder), and may also reduce the force required to remove a cured polymer from a mold (i.e., may improve demolding) in the case of injection molding.

[0058] Non-limiting, examples of flow agents that may be included in TPU compositions include amines (e.g., ethylene bisstearamide), waxes, lubricants, talc, and dispersants. Disclosed embodiments provide TPU compositions that may also include one or more inorganic flow agents such as hydrated silicas, amorphous alumina, glassy silicas, glassy phosphates, glassy borates, glassy oxides, titania, talc, mica, fumed silicas, kaolin, attapulgite, calcium silicates, alumina, and magnésium silicates. The amount of flow agent may vary with the nature and particle size of the particular flow agent selected.

[0059] In exemplary embodiments, the flow agent may be a wax, such as an ethylene steramide wax. An ethylene steramide wax may include octadecanamide, N,N'-l,2-ethanediylbis (C₃₈H7₆N₂O2; CAS Registry No. 100-30-5) and stearic acid [CH₃(CH₂)i₆COOH; CAS Registry No. 57-11-4], In exemplary embodiments, the flow agent may be présent in amounts from about 0.1% to about 5% by weight of the TPU.

[0060] Improved flow characteristics of TPU compositions may be achieved by reducing or eliminating the presence of certain compounds, such as calcium stéarate, for example.

Fillers

[0061] As described above, disclosed embodiments provide TPU compositions that may also include fillers that may include inorganic materials. Fillers strengthen and stiffen the TPU based material, enhancing properties of objects injection molded from the TPU material. For example, fillers help to maintain shapes of small openings, holes, or pores, formed in objects injection molded from the TPU composition. In some embodiments, for example, the fibers allow transmission of light for use in laser welding of molded TPU components to support structures.

[0062] In exemplary embodiments, glass fibers may be used as filler material, as described above. Glass fibers may take the form of solid or hollow glass tubes. In exemplary embodiments, glass tubes may hâve a diameter (or width, if not round) of between about 2 pm to about 20 pm. In an exemplary embodiment, glass fibers may hâve a diameter (or width, if not round) of between about 9 pm to about 13 pm. In an embodiment, glass fibers may hâve a 11 pm diameter or width. Glass fibers may hâve an initial length of between about 3.0 mm to about 3.4 mm. In an exemplary embodiment, glass fibers may hâve an initial length of 1/8 inch (i.e., 3.175 mm). During processing ofthe TPU material, however, glass fibers may break and thereby become shorter. In a hardened State after injection molding, glass fibers may hâve an average length of less than about 1.5 mm, with a range of most fibers being between about 1.0 mm to about 3.2 mm. Some ofthe fibers retain their original length, but most are broken into smaller pièces.

[0063] To allow laser welding of the TPU composition, it is désirable to use as little glass fiber as possible. Too much glass fiber leads to an unacceptably high amount of reflection/refraction of laser light. Additionally, desired properties of the TPU composition may dégradé with increasing glass fiber content. Glass fibers having a sufficiently large diameter may work better for laser weldable compositions. Such large diameter fibers may also provide désirable strengthening and stiffening properties. The diameter of glass fibers should not be too large, however, as désirable flow properties may dégradé with increasing diameter of glass fibers, reducing the suitability of the resulting composition for injection molding.

[0064] Glass fiber filler materials should not contain fibers having a diameter of greater than 50 pm, and should preferably hâve a diameter of less than 20 pm, in compositions developed for injection molding of structures having features on a sub-millimeter scale. Carbon fibers should be avoided in that they may not work for laser welding because they are not translucent. TPU based objects that are designed to be joinable via laser welding may hâve optical properties that allow laser light to pass through the TPU material. As such, laser light may pass through the TPU object and may hit an adjacent structure such as to a nylon subgrid. The nylon material of the subgrid is a thermoplastic having a dark color that absorbs laser light and may thereby be heated by the laser. Upon absorption of laser light, the TPU and the adjacent nylon may be heated to a température above their respective melting températures. In this way, both materials may be melted and, upon cooling, a mechanical bond may be formed at an interface between the TPU and the nylon, thereby welding the components together.

[0065] Disclosed embodiments provide TPU compositions that may also include particulate fillers, which may be of any configuration including, for example, spheres, plates, fibers, acicular (i.e., needle like) structures, flakes, whiskers, or irregular shapes. Suitable fillers may hâve an average longest dimension in a range from about 1 nm to about 500 pm. Some embodiments may include filler materials with average longest dimension in a range from about 10 nm to about 100 pm. Some fibrous, acicular, or whisker-shaped filler materials (e.g., glass or wollastonite) may hâve an average aspect ratio (i.e., length/diameter) in a range from about 1.5 to about 1000. Longer fibers may also be used in further embodiments.

[0066] Plate-like filler materials (e.g., mica, talc, or kaolin) may hâve a mean aspect ratio (i.e., mean diameter of a circle of the same area/mean thickness) that is greater than about 5. In an embodiment, plate-like filter materials may hâve an aspect ratio in a range from about 10 to about 1000. In a further embodiment, such plate-like materials may hâve an aspect ratio in a range from about 10 to about 200. Bimodal, trimodal, or higher mixtures of aspect ratios may also be used. Combinations of fillers may also be used in certain embodiments.

[0067] According to an embodiment, a TPU composition may include natural, synthetic, minerai, or non-mineral filler materials. Suitable filler materials may be chosen to hâve sufficient thermal résistance so that a solid physical structure of the filler material may be maintained, at least at the processing température of the TPU composition with which it is combined. In certain embodiments, suitable fillers may include clays, nanoclays, carbon black, wood flour (with or without oil), and various forms of silica. Silica materials may be precipitated or hydrated, fumed or pyrogenic, vitreous, fused or colloïdal. Such silica materials may include common sand, glass, metals, and inorganic oxides. Inorganic oxides may include oxides of metals in periods 2, 3, 4, 5 and 6 of groups IB, IIB, ΠΙΑ, ΙΠΒ, IVA, IVB (except carbon), VA, VIA, VIIA, and VIII, of the periodic table.

[0068] Filler materials may also include oxides of metals, such as aluminum oxide, titanium oxide, zirconium oxide, titanium dioxide, nanoscale titanium oxide, aluminum trihydrate, vanadium oxide, magnésium oxide, antimony trioxide, hydroxides of aluminum, ammonium, or magnésium. Filler materials may further include carbonates of alkali and alkaline earth metals, such as calcium carbonate, barium carbonate, and magnésium carbonate. Minerai based materials may include calcium silicate, diatomaceous earth, fuller earth, kieselguhr, mica, talc, slate flour, volcanic ash, cotton flock, asbestos, and kaolin.

[0069] Filler materials may further include alkali and alkaline earth métal sulfates, for example, sulfates of barium and calcium sulfate, titanium, zeolites, wollastonite, titanium boride, zinc borate, tungsten carbide, ferrites, molybdenum disulfide, cristobalite, aluminosilicates including vermiculite, bentonite, montmorillonite, Na-montmorillonite, Ca-montmorillonite, hydrated sodium calcium aluminum magnésium silicate hydroxide, pyrophyllite, magnésium aluminum silicates, lithium aluminum silicates, zirconium silicates, and combinations ofthe above-described filler materials.

[0070] Disclosed embodiments provide TPU compositions that may include fibrous fillers such as glass fibers (as described above), basait fibers, aramid fibers, carbon fibers, carbon nanofibers, carbon nanotubes, carbon buckyballs, ultra-high molecular weight polyethylene fibers, melamine fibers, polyamide fibers, cellulose fiber, métal fibers, potassium titanate whiskers, and aluminum borate whiskers.

[0071] In certain embodiments, TPU compositions may include glass fiber fillers, as described above. Glass fiber fillers may be of E-glass, S-glass, AR-glass, T-glass, D-glass and Rglass. In certain embodiments, the glass fiber diameter may be within a range from about 5 pm to about 35 pm. In other embodiments, the diameter of the glass fibers may be in a range from about 9 to about 20 pm. In further embodiments, glass fibers may hâve a length of about 3.2 mm or less. As described above, TPU compositions including glass fillers may confer improved thermal stability to the TPU compositions and articles produced them.

[0072] Disclosed embodiments may include compositions containing a glass filler with concentrations in a range from about 0.1% to about 7% by weight. Embodiments may also include glass filler at concentrations ranging from about 1% to about 2%; about 2% to about 3%; 3% to about 4%; about 4% to about 5%; about 5% to about 6%; about 6% to about 7%; about 7% to about 8%; about 8% to about 9%; about 9% to about 10%; about 10% to about 11%; about 11% to about 12%; about 12% to about 13%; about 13% to about 14%; about 14% to about 15%; about 15% to about 16%; about 16% to about 17%; about 17% to about 18%; about 18% to about 19%; and about 19% to about 20%. In certain embodiments a glass fdler concentration may be about 1%. In certain embodiments a glass fdler concentration may be about 3%. In certain embodiments a glass fïller concentration may be about 5%. In certain embodiments a glass fïller concentration may be about 7%. In certain embodiments a glass filler concentration may be about 10%.

[0073] As described above, embodiments may include glass filler material wherein individual glass fibers may hâve a diameter or width in a range from about 1 gm to about 50 gm. In certain embodiments, the glass filler may be characterized by a narrow distribution of fiber diameters such that at least 90% of the glass fibers hâve a spécifie diameter or width. Other embodiments may include a glass filler having a broader distribution of diameters or widths spanning a range from about 1 gm to about 20 gm. Further embodiments may include glass filler having a glass fiber diameter or width distribution spanning a range: from about 1 gm to about 2 gm; from about 2 gm to about 3 gm; from about 3 gm to about 4 gm; from about 4 gm to about 5 gm; from about 5 gm to about 6 gm; from about 6 gm to about 7 gm; from about 7 gm to about 8 gm; from about 8 gm to about 9 gm; from about 9 gm to about 10 gm; from about 10 gm to about 11 gm; from about 11 gm to about 12 gm; from about 12 gm to about 13 gm; from about 13 gm to about 14 gm; from about 14 gm to about 15 gm; from about 15 gm to about 16 gm; from about 16 gm to about 17 gm; from about 17 gm to about 18 gm; from about 18 gm to about 19 gm; and from about 19 gm to about 20 gm. In certain embodiments the glass filler may hâve a diameter or width distribution centered about a spécifie value. For example, the spécifie diameter or width value may be 10 gm ± 2 gm, according to an embodiment.

[0074] TPU compositions may include glass fiber fillers that include a surface treatment agent and optionally a coupling agent, according to an embodiment. Many suitable materials may be used as a coupling agent. Examples include silane-based coupling agents, titanate-based coupling agents, or a mixture thereof. Applicable silane-based coupling agents, for example, may include aminosilane, epoxysilane, amidesilane, azidesilane, and acrylsilane.

[0075] Disclosed embodiments provide TPU compositions that may also include other suitable inorganic fibers such as: carbon fibers, carbon/glass hybrid fibers, boron fibers, graphite fibers, etc. Various ceramic fibers can also be utilized such as alumina-silica fibers, alumina fibers, Silicon Carbide fibers, etc. Metallic fibers, such as aluminum fibers, nickel fibers, Steel, stainless Steel fibers, etc., may also be used.

[0076] Disclosed TPU compositions may be generated by a process in which TPU reactants may be combined with filler materials (e.g., fiber fillers) and other optional additives. The combination of materials may then be physically mixed in a mixing or blending apparatus.

[0077] An example mixing or blending apparatus may include: a Banbury, a twin-screw extrader, a Buss Kneader, etc. In certain embodiments, filler and base TPU composition materials may be mixed or blended to generate a TPU composition blend having fibers incorporated therein. The resulting TPU composition having fillers (e.g., glass fibers), and optionally other additional additives, may be cooled to generate a solid mass. The resulting solid mass may then be pelletized or otherwise divided into suitable size particles (e.g., granulated) for use in an injection molding process. The injection molding process may be used to generate an article of manufacture such as a screen or screening element.

[0078] Optional additives to TPU compositions, mentioned above, may include dispersants. In certain embodiments, dispersants may help to generate a uniform dispersion of base TPU composition and additional components such as fillers. In certain embodiments, a dispersant may also improve mechanical and optical properties of a resulting TPU composition that includes fillers.

[0079] In certain embodiments, waxes may be used as dispersants. Non-limiting examples of wax dispersants, suitable for use in disclosed TPU compositions, include: polyethylene waxes, amide waxes, and montan waxes. TPU compositions disclosed herein may include an amide wax dispersant, such as Ν,Ν-bis-stearyl ethylenediamine. The use of such a wax dispersant may increase thermal stability of the TPU composition yet may hâve little impact on polymer transparency. As such, inclusion of dispersants in disclosed TPU compositions may hâve at least to désirable effects: (1) improved thermal stability of compositions and articles produced therefrom, and (2) désirable optical properties that are suitable for downstream processing including laser welding.

[0080] Disclosed TPU compositions may further include antioxidants, according to an embodiment. Antioxidants may be use to terminate oxidation reactions, that may occur due to various weathering conditions, and/or may be used to reduce dégradation of a TPU composition. For example, articles formed of synthetic polymers may react with atmospheric oxygen when placed into service. In addition, articles formed of synthetic polymers may undergo autooxidization due to free-radical chain reactions. Oxygen sources (e.g., atmospheric oxygen, alone or in combination with a free radical initiator) may react with substrates included in disclosed TPU compositions. Such reactions may compromise integrity of the TPU composition and articles produced therefrom. Inclusion of antioxidants, therefore, may improve Chemical stability of TPU compositions as well as improving Chemical stability of articles generated therefrom.

[0081] Polymers may undergo weathering in response to absorption of UV light that causes radical initiated auto-oxidation. Such auto-oxidation may lead to cleavage of hydroperoxides and carbonyl compounds. Embodiment TPU compositions may include Hydrogen-donating antioxidants (AH), such as hindered phénols and secondary aromatic amines. Such AH additives may inhibit oxidation of TPU compositions by competing with organic substrates for peroxy radicals. Such compétition for peroxy radicals may terminate chain reactions and thereby stabilize or prevent further oxidation reactions. Inclusion of antioxidants in disclosed TPU compositions may inhibit formation of free radicals. In addition to AH being a light stabilizer, AH may also provide thermal stability when included in disclosed TPU compositions. Accordingly, certain embodiments may include additives (e.g., AH) that enhance stability of polymers exposed to UV light and heat. Articles generated from disclosed TPU compositions having antioxidants may, therefore, be résistant to weathering and hâve improved function and/or lifespan, when deployed under high-temperature conditions, relative to articles generated from TPU compositions lacking antioxidants.

[0082] Disclosed TPU compositions may further include UV absorbers, according to an embodiment. UV absorbers couvert absorbed UV radiation to heat by réversible intramolecular proton transfer reactions. In some embodiments, UV absorbers may absorb UV radiation that would otherwise be absorbed by the TPU composition. The resulting reduced absorption of UV rays by the TPU composition may help to reduce UV radiation induced weathering of the TPU composition. Non-limiting example UV-absorbers may include oxanilides for polyamides, benzophenones for polyvinyl chloride (PVC), and benzotriazoles and hydroxyphenyltriazines for polycarbonate materials. In an embodiment, 2-(2'-Hydroxy-3'-sec-butyI-5'-tertbutylphenyl)benzotriazole may provide UV light stabilization for polycarbonate, polyester, polyacetal, polyamides, TPU materials, styrene-based homopolymers, and copolymers. These and other UV absorbers may improve the stability of disclosed TPU compositions and articles produced therefrom, according to various embodiments.

[0083] TPU compositions may further include anti-ozonants which may prevent or slow dégradation of TPU materials caused by ozone gas in the air (i.e., may reduce ozone cracking). Non-limiting exemplary embodiments of antiozonates may include: p-Phenylenediamines, such as 6PPP (N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) or IPPD (N-isopropyl-N'phenyl-p-phenylenediamine); 6-ethoxy-2,2,4-trimethyl-l,2-dihydroquinoline, (ETMQ) ethylene diurea (EDU), and paraffin waxes that may form a surface barrier. These and other antiozonants may improve the stability of disclosed TPU compositions as well as articles produced therefrom, according to various embodiments.

[0084] According to an embodiment, an example mixture may be prepared as follows. The starting material may be chosen to be a polycarbonate-based thermoplastic polyuréthane. A filler material may be chosen to be small diameter (as described above) glass fïbers included in an amount from between about 3% and about 10% by weight. A flow agent may then be chosen to be included in an amount of between about 0.1% to about 5% by weight. In this example, the flow agent may be taken to be a mixture of octadecanamide, N,N'-l,2-ethanediylbis and stearic acid. A thermal-stabilizing agent may be chosen to be pentaérythritol tetrakis(3-(3,5-di-tertbutyl-4-hydroxyphenyl)propionate) included in an amount of between about 0.1% to about 5% by weight. The above-described thermoplastic mixture may then be injected into bulk thermoplastic rods then pelletized for downstream injection molding.

Methods

[0085] Disclosed embodiments provide methods and processes for generating TPU compositions. Disclosed methods may include reacting (i.e., linking) pre-polymer units including an alcohol (OH) and an isocyanate (NCO) to effectively “grow” and/or extend a polymer chain or backbone. For example, in an embodiment, a TPU composition may be prepared by reacting a polyuréthane pre-polymer and a curing agent, typically at températures from about 50° C to about 150° C, for example, or from about 50° C to about 100° C. Températures outside these ranges may also be employed in certain embodiments.

[0086] Disclosed TPU compositions may be melted and formed into a desired shape, for example, by injection molding. Disclosed methods may further include a post curing step including heating the TPU material at températures from about 50° C to about 200° C, or from about 100° C to about 150° C, for a predetermined period of time. For example, TPU materials may be heated for about 1 hour to about 24 hours. Altematively, various methods may include an extrusion step wherein a post-cured TPU composition may be extruded at températures from about 150° C to about 270° C, or from about 190° C or higher, to render the TPU composition in an intermediate form. The intermediate form may be suitable for downstream processing to generate a final form, such as a TPU based screening element.

[0087] Disclosed methods may include a variety of additional processing operations. For example, a disclosed method or process may include: reacting a polyuréthane pre-polymer and a curing agent (i.e., polymerization); post curing the polyuréthane; optionally grinding the material to generate a post cured polyuréthane polymer in granulated form; extruding the post cured and/or optionally granulated polyuréthane polymer; and optionally pelletizing the extruded TPU.

[0088] In an embodiment, the TPU composition may be generated by a process in which a pre-polymer is mixed with a curing agent at températures of from about 50° C to about 150° C to form a polymer. The method may then include heating the polymer at températures from about 50° C to about 200° C for about 1 to about 24 hours to obtain a post-cured polymer. The postcured polymer may then optionally be ground to generate a granulated polymer. Optionally, the method may further include processing either the post-cured polymer or the granulated polymer in an extrader at températures from about 150° C, or higher, to yield a TPU composition.

Further operations may optionally include pelletizing the TPU composition, re-melting the pelletized TPU composition, and extruding the melted TPU composition.

[0089] Disclosed methods may further include generating TPU compositions containing optional additives. In an embodiment, optional additives may include antioxidants (including phenolics, phosphites, thioesters, and/or amines), antiozonants, thermal stabilizers, inert fillers, lubricants, inhibitors, hydrolysis stabilizers, light stabilizers, hindered amine light stabilizers, UV absorbers (e.g., benzotriazoles), heat stabilizers, stabilizers to prevent discoloration, dyes, pigments, inorganic and organic fillers, organosulfur compounds, thermal stabilizers, reinforcing agents, and combinations thereof.

[0090] Disclosed methods include generating TPU compositions containing optional additives in effective amounts customary for each respective additive. In various embodiments, such optional additional additives may be incorporated into the components of, or into the reaction mixture for, the préparation of the TPU composition. In other embodiments, a base TPU composition lacking optional additives may be generated and optionally processed. Optional processing operations may include grinding TPU materials to generate a granulated material, or to form a powdered base TPU composition material to which optional additives may then be mixed prier to further processing.

[0091] In other embodiments, powdered mixtures including a base TPU composition and optional additives may be mixed, melted, and extruded to form a composition. In other embodiments, the TPU composition may be prepared through a reactive extrusion process wherein pre-polymer, curing agent, and any optional additives are fed directly into an extruder, and then are mixed, reacted, and extruded at an elevated température. Various alternative combinations of these formulation operations may also be employed in various embodiments.

Articles of Manufacture

[0092] Disclosed embodiments include apparatus, articles of manufacture, and products generated using TPU compositions. Non-limiting example embodiments may include coatings or adhesives, and/or articles having a predetermined three-dimensional structure upon curing after being cast or extruded into a mold. Disclosed embodiments provide TPU compositions that may exhibit significantly higher load bearing properties than other materials based on natural and synthetic rubber, for example.

[0093] In various embodiments, articles generated from disclosed TPU compositions may be thermostable. In this regard, although thermoplastics may generally be re-melted and reformed, articles produced from disclosed TPU compositions may exhibit résistance to effects resulting from thermal strain at températures sufficiently lower than a melting température. For example, articles generated from disclosed TPU compositions may retain their shape (i.e., they may exhibit modulus rétention) at elevated températures corresponding to service conditions, including températures in a range from about 170° C to about 200 C. Disclosed TPU compositions may be used to form articles that may retain their structure, mechanical strength, and overall performance at elevated températures.

[0094] Disclosed TPU compositions may exhibit thermal stability in a température range from about 160° C to about 210° C. Embodiment TPU compositions may also exhibit thermal stability for températures in a range from about 170° C to about 200° C, while further embodiments may exhibit thermal stability for températures in a range from about 175° C to about 195° C. Disclosed embodiments may also provide a TPU composition that may exhibit thermal stability for températures near 180° C.

[0095] Disclosed embodiments include TPU compositions having favorable mechanical properties, as characterized by cut/tear/abrasion résistance data, relative to known thermoplastic compositions. In certain embodiments, improved properties may include: greater tear strength, better modulus rétention at high température, low compression set, improved rétention of physical properties over time and upon exposure to harmful environments. Certain embodiments provide TPU compositions that may hâve a combination of improved characteristics such as superior thermal stability, abrasion résistance, and Chemical résistance (e.g., to oils and grease). In certain embodiments, articles generated from disclosed TPU compositions may hâve characteristics that are highly désirable for oil, gas, Chemical, mining, automotive, and other industries.

[0096] In an exemplary embodiment, an example TPU composition, provided in pellet form, may be loaded into a cylinder of an injection press. Once loaded into the cylinder, the pellet may be heated for a period of time to thereby melt the TPU composition material. The injection press may then extrade the melted exemplary TPU composition material into a mold cavity according to a predetermined injection rate. The injection press may be adapted to include specialized tips and/or nozzles configured to achieve a desired injection output.

[0097] Various parameters may be controlled or adjusted to achieve desired results. Such parameters may include, but are not limited to, barrel température, nozzle température, mold température, injection pressure, injection speed, injection time, cooling température, and cooling time.

[0098] In an embodiment method, barrel températures of an injection molding apparatus may be chosen to range from about 148° C to about 260° C, from about 176° C to about 233 C, from about 204° C to about 233° C, from about 210° C to about 227° C, and from about 215° C to about 235° C. Nozzle températures of an injection molding apparatus may be chosen to range from about 204° C to about 260° C, from about 218° C to about 246° C, from about 234° C to about 238° C, and from about 229° C to about 235° C.

[0099] In an embodiment method, injection pressure of an injection molding apparatus may be chosen to range from about 400 PSI to about 900 PSI, from about 500 PSI to about 700 PSI, from about 600 PSI to about 700 PSI, and from about 620 PSI to about 675 PSI. Injection speed of an injection molding apparatus may be chosen to range from about 1.0 cubic inch/second to about 3.0 cubic inch/second, from about 1.5 to about 2.5 cubic inch/second, from about 1.75 cubic inch/second to about 2.5 cubic inch/second, and from about 2.1 cubic inch/second to about 2.4 cubic inch/second.

[00100] In an embodiment method, injection time may be chosen to range from about 0.25 seconds to about 3.00 seconds, from about 0.50 second to about 2.50 seconds, from about 0.75 seconds to about 2.00 seconds, and from about 1.00 second to about 1.80 seconds. Moreover, the injection time may be modified to include a “hold” for a certain period of time in which injection is paused. Hold periods may be any particular time. In an exemplary embodiment, the hold time may range from 0.10 seconds to 10.0 minutes. Other hold times may be use in other embodiments.

[00101] In an embodiment method, mold températures may be chosen to range from about 37° C to about 94° C, from about 43° C to about 66° C, and from about 49° C to about 60° C. Cooling températures may be gradually reduced to control curing of a disclosed TPU composition. The température may be gradually reduced from that of the mold température to ambient température over a period of time. The time period for cooling may be chosen to be virtually any time period ranging from second to hours. In an embodiment, the cooling time period may range from about 0.1 to about 10 minutes.

[00102] The following method describes an injection molding process that generates screening members based on disclosed TPU compositions. As described above, TPU compositions may be formed as TPU pellets. The TPU composition material may first be injected into a mold that is designed to generate a screening member. The TPU composition may then be heated to a température suitable for injection molding to thereby melt the TPU material. The melted TPU material may then be loaded into an injection molding machine. In an embodiment, the mold may be a two-cavity screening member mold. The mold containing the injected melted TPU material may then be allowed to cool. Upon cooling, the TPU material solidifies into a screening member shape defined by the mold. The resulting screening members may then be removed from the mold for further processing.

Development of Suitable Compositions

[00103] The above-described embodiments provide TPU compositions expressed in ranges of the various components. Improved materials were obtained by varying the composition of TPU materials and percentages of fillers, flow agents, and other additives. Screening members were generated using injection molding processes based on the various compositions. The screening members were attached to subgrid structures and assembled into large-area screening assemblies that were used in field testing applications.

[00104] FIG. 4 illustrâtes an example screening assembly that was generated from screening members and subgrid structures as described above with reference to FIGS. 1 to 3A, according to disclosed embodiments.

[00105] FIG. 5 illustrâtes results of actual field testing of screening assemblies, accord to an embodiment. The data presented in FIG. 5 represents results of testing embodiment screening assemblies for screening materials produced during oil and gas exploration at depths extending to at least about 100,000 feet ± 5,000 feet. The best performing composition BB had a glass fiber (10 pm diameter) content of about 7%, while the next-best performing composition BA had a glass fiber (10 pm diameter) content of about 5%. Each composition also had flow agent content of about 0.5%, and a heat stabilizer content of about 1.5%. The screening element surface éléments 84 (e.g., see FIG. 2) had thickness T about 0.014 inches in ail of the tests for which results are presented in FIG. 5.

[00106] In additional embodiments, screening members having surface éléments 84 having smaller thicknesses including T = 0.007 inch, 0.005 inch, and 0.03 inch, where generated. For these embodiments, it was advantageous to use lower concentrations of filler, flow agent, and thermal stabilizers as shown in the table below.

	T = 0.014 inch	T = 0.007 inch	T = 0.005 inch	T = 0.003 inch
filler	7%	5%	3%	2%
heat stabilizer	1.5%	1.5%	1.13%	0.85%
flow agent	0.5%	0.5%	0.38%	0.28%

[00107] Example embodiments are described in the foregoing. Such example embodiments, however, should not be interpreted as limiting. In this regard, various modifications and changes may be made thereunto without departing from the broader spirit and scope hereof. The spécification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.

Claims (48)

1. A screening element, comprising:

a composition including a thermoplastic polyuréthane and a modified ester, wherein the screening element is a single injection molded piece including openings having a size that is in a range from approximately 35 pm to approximately 150 pm.

2. The screening element of claim 1, wherein the openings hâve a shape that is approximately rectangular, square, circular, or oval.

3. The screening element of claim 1, wherein the openings are elongated slots having a substantially uniform length L along a first direction, and a substantially uniform width W along a second direction, separated by surface éléments having a thickness T along the second direction.

4. The screening element of claim 3, wherein the thickness T of the surface éléments is in a range from approximately 0.003 inch to 0.020 inch.

5. The screening element of claim 3, wherein the thickness W of the surface éléments is in a range from approximately 0.0015 inch to approximately 0.0059 inch.

6. The screening element of claim 3, wherein a length-to-width ratio L/W of the elongated slots has a value in a range from approximately 1:1 to approximately 30:1.

7. The screening element of claim 3, wherein:

the surface éléments hâve a thickness T that is approximately 0.014 inch.

8. The screening elementof Claim 1, wherein the open screening area of the screen element is from approximately 10% to approximately 35% of a total screening area.

9. The screening element of claim 7, wherein the screening element has an open screening area in a range from approximately 10% to approximately 15% of a total screening area.

10. The screening element of claim 3, wherein:

the surface éléments hâve a thickness T that is approximately 0.007 inch.

11. The screening element of claim 3, wherein:

the surface éléments hâve a thickness T that is approximately 0.005 inch.

12. The screening element of claim 3, wherein:

the surface éléments hâve a thickness T that is approximately 0.003 inch.

13. The screening element of claim 11, wherein the screening element has an open screening area in a range from approximately 30% to approximately 35% of a total screening area.

14. The screening element of claim 1, wherein the thermoplastic polyuréthane is obtained by a process in which a polyuréthane prepolymer having a free polyisocyanate monomer content of less than 1% by weight is reacted with a curing agent and then processed by extrusion at températures of 150° C or higher.

15. The screening element.ofdaim14, wherein the urethane prepolymer is prepared from a polyisocyanate monomer and a polyol comprising an alkane diol, polyether polyol, polyester polyol, polycaprolactone polyol and/or polycarbonate polyol, and the curing agent includes a diol, triol, tetrol, alkylene polyol, polyether polyol, polyester polyol, polycaprolactone polyol, polycarbonate polyol, diamine or diamine dérivative.

16. A method of manufacturing a screening element, the method comprising: injection molding the screening element using a polyuréthane that contains a glass fiber filler at a température greater than about 150 °C such that the resulting screening element is a single injection molded piece having openings, wherein the size of the openings is from approximately 43 pm to approximately 150 pm, wherein the filler has a concentration from approximately 1% to 10% by weight of the thermoplastic polyuréthane, the. concentration being chosen based on one or more of the size of the openings, the spacing of the openings, and the thermoplastic polyuréthane composition, and wherein the openings in the screening element having an open screening area in a range from approximately 10% to approximately 35% of a total area of the screening element.

17. The method of claim 16, wherein injection molding the screening element further comprises using a mold to generate the openings to be elongated slots having a substantially uniform length L along a first direction, and a substantially uniform width W along a second direction, separated by surface éléments having a thickness T along the second direction.

18. The method of claim 17, wherein:

the surface éléments hâve a thickness T that is approximately 0.014 inch, and the filler has a concentration that is approximately 10% by weight of the thermoplastic polyuréthane.

19. The method of claim 18, wherein the screening element has an open screening area from approximately 10% to approximately 15% of a total area of the screening element.

20. The method of claim 17, wherein:

the surface éléments hâve a thickness T that is approximately 0.007 inch, and the filler has a concentration that is approximately 7% by weight ofthe thermoplastic polyuréthane.

21. The method of claim 17, wherein:

the surface éléments hâve a thickness T that is approximately 0.005 inch, and the filler has a concentration that is approximately 5% by weight of the thermoplastic polyuréthane.

22. The method of claim 17, wherein:

the surface éléments hâve a thickness T that is approximately 0.003 inch, and the filler has a concentration that is approximately 3% by weight of the thermoplastic polyuréthane.

23. The method of claim 22. wherein the screening element has an open screening area that is in a range from approximately 30% to approximately 35% of a total area of the screening element.

24. The method of claim 16, wherein generating the composition further comprises:

reacting the thermoplastic polyuréthane and filler with a flow agent, the flow agent having a concentration in a range from approximately 0.1% to 5% by weight of the thermoplastic polyuréthane.

25. The method of claim 16, wherein the thermoplastic polyuréthane is obtained by a process in which a thermoplastic polyuréthane polymer is produced by reacting a urethane prepolymer having a free diisocyanate monomer content of less than 1% by weight with a curing agent to form a polyuréthane that is thermally processed by extrusion at températures of 150° C or higher.

26. A method of manufacturing a composition for injection molding of articles of manufacture containing fine pores, the method comprising:

reacting a thermoplastic polyuréthane and a filler at a température greater than approximately 150° C to produce a thermoplastic polyuréthane composition;

choosing the filler material to include glass fibers having a concentration from approximately 1% to approximately 10% by weight of the thermoplastic polyuréthane, the concentration of the filler is chosen based on one or more of the pore sizes of articles, the spacing of the pores, and the thermoplastic polyuréthane composition, the articles having pores sizes from approximately 43 pm to approximately 150 pm.

27. The method of claim 26, further comprising:

choosing the filler concentration to be approximately 10% by weight of the thermoplastic polyuréthane such that the concentration is suitable for injection molding articles having surface éléments with thickness of approximately 0.014 inch.

28. The method of claim 27, further comprising:

reacting the thermoplastic polyuréthane and filler with a heat stabilizer and a flow agent, wherein the heat stabilizer has a concentration that is approximately 1.5% by weight of the thermoplastic polyuréthane, and wherein the flow agent has a concentration that is approximately 0.5% by weight of the thermoplastic polyuréthane.

29. The method of claim 26, further comprising;

choosing the filler concentration to be approximately 7% by weight of the thermoplastic polyuréthane such that the concentration is suitable for injection molding articles having surface éléments with thickness of approximately 0.007 inch.

30. The method of claim 29, further comprising:

reacting the thermoplastic polyuréthane and filler with a heat stabilizer and a flow agent, wherein the heat stabilizer has a concentration that is approximately 1.5% by weight of the thermoplastic polyuréthane, and wherein the flow agent has a concentration that is approximately 0.5% by weight of the thermoplastic polyuréthane.

31. The method of claim 26, further comprising:

choosing the filler concentration to be approximately 5% by weight of the thermoplastic polyuréthane such that the concentration is suitable for injection molding articles having surface éléments with thickness of approximately 0.005 inch.

32. The method of claim 31, further comprising:

reacting the thermoplastic polyuréthane and filler with a heat stabilizer and a flow agent, wherein the heat stabilizer has a concentration that is approximately 1.13% by weight of the thermoplastic polyuréthane, and wherein the flow agent has a concentration that is approximately 0.38% by weight of the thermoplastic polyuréthane.

33. The method of claim 26, further comprising:

choosing the filler concentration to be approximately 3% by weight of the thermoplastic polyuréthane such that the concentration is suitable for injection molding articles having surface éléments with thickness of approximately 0.003 inch.

34. The method of claim 33, further comprising:

reacting the thermoplastic polyuréthane and filler with a heat stabilizer and a flow agent, wherein the heat stabilizer has a concentration that is approximately 0.85% by weight of the thermoplastic polyuréthane, and wherein the flow agent has a concentration that is approximately 0.28% by weight of the thermoplastic polyuréthane.

35. The method of claim 26, wherein the glass fibers hâve a diameter or width of less than about

20 pm.

36. The method of claim 26, wherein the glass fibers hâve a diameter or width having a value in a range from approximately 9 pm to approximately 13 pm.

37. The method of claim 26, wherein the glass fibers hâve a length of less than approximately 3.4 mm.

38. A composition comprising:

a thermoplastic polyuréthane; and a filler comprising glass fibers, wherein the glass fibers are less than about 10% by weight ofthe thermoplastic polyuréthane, wherein the thermoplastic polyuréthane is obtained by a process in which polyuréthane prepolymer having a free polyisocyanate monomer content of less than 1% by weight is reacted with a curing agent then processed by extrusion at températures of 150° C or higher, and wherein the composition is suitable for injection molding articles of manufacture containing fine pores having sizes in a range from approximately 43 pm to approximately 150 pm.

39. The composition of claim 38, wherein the urethane prepolymer is prepared from a polyisocyanate monomer and a polyol comprising an alkane diol, polyether polyol, polyester polyol, polycaprolactone polyol and/or polycarbonate polyol, and the curing agent comprises a diol, triol, tetrol, alkylene polyol, polyether polyol, polyester polyol, polycaprolactone polyol, polycarbonate polyol, diamine or diamine dérivative.

40. The composition of claim 38, further comprising a heat stabilizer.

41. The composition of claim 40, wherein the heat stabilizer is about 0.1 percent to about 5 percent by weight of the thermoplastic polyuréthane.

42. The composition of claim 41, wherein the heat stabilizer comprises a sterically hindered phenolic antioxidant.

43. The composition of claim 42, wherein the sterically hindered phenolic antioxidant is pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate).

44. The composition of claim 38, further comprising a flow agent selected to optimize use of the composition in injection molding.

45. The composition of claim 44, wherein the flow agent is about 0.1 percent to about 5 percent by weight of the thermoplastic polyuréthane.

46. The composition of claim 45, wherein the flow agent comprises an ethylene steramide wax.

47. The composition of claim 46, wherein the ethylene steramide wax comprises N,N'-1,2- ethanediylbisoctadecanamide and stearic acid.

48. The composition of claim 38, wherein the glass fibers hâve a diameter or width that is less than about 20 pm.