Silica reinforced thermoplastic polyurethane

Abstract

To provide a thermoplastic polyurethane reinforced with hydrophobic fumed silica.SOLUTION: A hydrophobic silica is combined with a polyether in an in-situ process to produce a thermoplastic polyurethane having excellent mechanical properties. The resulting thermoplastic polyurethanes can be used in a variety of applications including footwear midsoles and outsoles, as well as wire insulation, hoses, films, wheels and tires, and drilling / mining screens.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to thermoplastic polyurethanes reinforced with hydrophobic fumed silica. [Background technology]

[0002] The term "polyurethane" refers to a wide range of polymer compositions. Each of these polymer compositions contains a polymer whose repeating units contain -N-CO-O- bonds. In addition, polyurethanes may also contain urea (-N-CO-N-) bonds. However, the composition of the molecular chain between these urethane and urea bonds and the method of producing the polymer affect the final properties. Thus, polyurethanes with different compositions and / or produced by different methods are used in a variety of applications ranging from adhesives to coatings to elastomers to different types of foamed materials. Generally, polyurethanes are produced by the reaction of polyisocyanates and polyols.

[0003] Polyurethanes are versatile materials whose chemistry can be altered for use in a variety of forms, including adhesives, coatings, foams, and high-density thermoplastics. Typically, two different polyols are used to create a block copolymer to form a thermoplastic polyurethane. For example, low-molecular-weight glycols and diisocyanates result in the formation of short chains linked through hydrogen bonds, forming a hard phase that may be crystalline. A second, "softer" block can be formed by using polyether or polyester polyols, which result in amorphous domains. The properties of thermoplastic polyurethanes (TPUs) are determined by the morphology of the two domains. The hard domains or phases act as fillers that provide reinforcement, allowing otherwise elastomeric TPUs to be processed using plastics processing equipment rather than rubber processing equipment, while the TPU material still behaves as an elastomer under strain. The tensile properties of the polymer are determined by how tensile forces interfere with the hydrogen bonding in the hard domains.

[0004] Generally, various fillers are used in polyurethanes to modify their mechanical, electrical and other properties. These fillers can be combined with the polymerized material, for example, by melt mixing, or can be incorporated into the prepolymer composition before polycondensation in an in-situ process. The fillers used in the in-situ process must fulfill two functions: they must not only provide the desired properties to the final product, but also cannot interfere with the polymerization that produces the product.

[0005] WO 2012 / 069264 discloses methods and formulations for incorporating fumed silica, including both hydrophilic and hydrophobic fumed silica, into thermoplastic polyurethanes. However, it is desirable to better optimize the effect of hydrophobic silica on the polymerization and final properties of polyurethane materials. Summary of the Invention

[0006] In one embodiment, a method for producing a thermoplastic polyurethane includes mixing a first polyol having a number average molecular weight of 300 to 5000 with a fumed silica having a surface containing C1 to C8 alkylsilyl groups or acrylate or methacrylate ester groups and a thickness of at least 50 m 2 % or less of a fumed silica having a surface area of ​​0.8 g / g, combining the polyol composition with an aromatic, cycloaliphatic, or araliphatic diisocyanate to form a prepolymer composition, and polymerizing the prepolymer composition to form a thermoplastic polyurethane having a density of 0.8 g / mL or greater. The thermoplastic polyurethane may be molded (i.e., shaped by being placed in a mold).

[0007] The step of polymerizing the prepolymer composition may include adding a catalyst to the prepolymer composition. The prepolymer composition further includes a chain extender. The fumed silica has a viscosity of 50 to 400 m. 2 The fumed silica may have a surface area of ​​1 / g. The fumed silica may have C1 to C3 alkylsilyl groups on the surface.

[0008] The thermoplastic polyurethane composition can have a higher elongation at break than the elongation at break of a control thermoplastic polyurethane having the same composition but without the fumed silica. Alternatively or in addition, the thermoplastic polyurethane composition has a rebound resilience that is 4% or less than the rebound resilience of a control thermoplastic polyurethane having the same composition but without the silica. Alternatively or in addition, the thermoplastic polyurethane can have a compression set (Ct) greater than the compression set (Ct) of a control thermoplastic polyurethane having the same composition but without the silica, as measured by ASTM D-395.

[0009] The prepolymer composition may further comprise one or more surfactants, fillers, flame retardants, nucleating agents, solvents, antioxidants, lubricants, mold release agents, dyes, pigments, plasticizers, or UV stabilizers. The polyol composition may comprise up to 15 wt% fumed silica.

[0010] In another embodiment, the thermoplastic polyurethane is produced by any combination or subcombination of the above methods. The thermoplastic polyurethane may contain 10 wt% or less fumed silica. The thermoplastic polyurethane may be molded. The thermoplastic polyurethane may have an elongation at break greater than the elongation at break of a control thermoplastic polyurethane having the same composition but without the fumed silica. Alternatively or additionally, the thermoplastic polyurethane may have a rebound resilience that is 4% or less less than the rebound resilience of the same control thermoplastic polyurethane but without the silica. Alternatively or additionally, the thermoplastic polyurethane may have a compression set (Ct) greater than the compression set (Ct) of a control thermoplastic polyurethane having the same composition but without the silica, as measured by ASTM D-395.

[0011] Alternatively or additionally, the thermoplastic polyurethane composition includes particulate fumed silica having a density of at least 0.8 g / mL and having C1-C8 alkylsilyl groups or acrylate or methacrylate ester groups on its surface. The thermoplastic polyurethane has an elongation at break that is higher than the elongation at break of a control thermoplastic polyurethane having the same composition except without the fumed silica. The thermoplastic polyurethane may be molded.

[0012] Alternatively or in addition, the thermoplastic polyurethane may have a rebound resilience that is 4% or less than that of a control thermoplastic polyurethane having the same composition but without the silica.Alternatively or in addition, the thermoplastic polyurethane may have a compression set (Ct) greater than that of a control thermoplastic polyurethane having the same composition but without the silica, as measured by ASTM D-395.

[0013] Fumed silica may be present in an amount of 0.1 wt% to 10 wt%, and 2 / g~400m 2 / g and may have C1-C3 alkylsilyl groups on its surface. The thermoplastic polyurethane may further include one or more surfactants, fillers, flame retardants, nucleating agents, solvents, antioxidants, lubricants, mold release agents, dyes, pigments, plasticizers, or UV stabilizers.

[0014] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed.

[0015] The invention will now be described with reference to several drawings. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a graph showing Shore A hardness for TPU materials made according to an embodiment of the invention having silica at various loadings (dots=0 wt%, horizontal lines=0.63 wt%, checkered=3.17 wt%, diagonal lines=6.44 wt%). [Figure 2] 1 is a graph showing rebound resilience for TPU materials made according to an embodiment of the present invention having silica at various loadings (dots=0 wt%, horizontal lines=0.63 wt%, checkered=3.17 wt%, diagonal lines=6.44 wt%). [Figure 3]1 is a graph showing the modulus of elasticity for TPU materials made according to an embodiment of the invention having silica at various loadings (dots=0 wt%, horizontal lines=0.63 wt%, checkered=3.17 wt%, diagonal lines=6.44 wt%). [Figure 4] 1 is a graph showing elongation at break for TPU materials made according to an embodiment of the invention having silica at various loadings (dots=0 wt%, horizontal lines=0.63 wt%, checkered=3.17 wt%, diagonal lines=6.44 wt%). [Figure 5] 1 is a graph showing toughness for TPU materials made according to an embodiment of the present invention having silica at various loadings (dots=0 wt%, horizontal lines=0.63 wt%, checkered=3.17 wt%, diagonal lines=6.44 wt%). [Figure 6] 1 is a graph showing abrasion resistance for TPU materials made according to an embodiment of the present invention having silica at various loadings (dots=0 wt%, horizontal lines=0.63 wt%, checkered=3.17 wt%, diagonal lines=6.44 wt%). [Figure 7] 1 is a graph showing tear strength for TPU materials made according to an embodiment of the present invention having silica at various loadings (dots=0 wt%, horizontal lines=0.63 wt%, checkered=3.17 wt%, diagonal lines=6.44 wt%). [Figure 8] 1 is a graph showing compression set (Ct) for TPU materials made according to embodiments of the present invention having silica at various loadings (narrowly spaced horizontal lines = no silica, dotted pattern = Example 1, widely spaced horizontal lines = Example 2, diagonal lines = Example 3). [Figure 9] 1 is a graph showing heat resistance for TPU materials made according to an embodiment of the present invention having silica at various loadings (dots=0 wt%, horizontal lines=0.63 wt%, checkered=3.17 wt%, diagonal lines=6.44 wt%). [Figure 10] 1 is a graph showing Shore A hardness for TPU materials made using melt blends with silica at various loadings (dotted: none, horizontal lines: low loading, checkered: medium loading, diagonal lines=highest loading). [Figure 11] 1 is a graph showing the modulus of elasticity for TPU materials made using melt blends with silica at various loadings (dotted: none, horizontal lines: low loading, checkered: medium loading, diagonal lines=maximum loading). [Figure 12] 1 is a graph showing the elongation at break for TPU materials made using melt blends with silica at various loadings (dotted: none, horizontal lines: low loading, checkered: medium loading, diagonal lines=maximum loading). [Figure 13] 1 is a graph showing the rebound resilience for TPU materials made using melt blends with silica at various loadings (dots: none, horizontal lines: low loading, checkered: medium loading, diagonal lines=maximum loading). DETAILED DESCRIPTION OF THE INVENTION

[0017] Detailed Description of the Invention In one embodiment, a method for producing a thermoplastic polyurethane includes combining up to 15 wt. % fumed silica with a first polyol having a number average molecular weight of 300 to 5000 to form a silica-polyol dispersion. The silica-polyol dispersion is combined with an aromatic, cycloaliphatic, or araliphatic diisocyanate and polymerized. The fumed silica has a molecular weight of at least 50 m 2 / g and is hydrophobized using a surface treatment that leaves C1-C8 alkylsilyl groups or acrylate or methacrylate ester groups, preferably C1-C3 alkylsilyl groups, on the surface. The resulting thermoplastic elastomer has a very low concentration of cells or voids and is supported by a density of 0.8 g / mL or greater, e.g., at least 1 g / mL or 1-2 g / mL.

[0018] Suitable isocyanates for use in the formulations and processes provided herein include organic diisocyanates capable of forming crystalline domains in thermoplastic polyurethanes. The formation of crystalline domains is particularly promoted by aromatic isocyanates, although cycloaliphatic and araliphatic isocyanates can be used as well. Exemplary isocyanates include, for example, m-phenylene diisocyanate, 2,4- and / or 2,6-toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate, hydrogenated MDI (H12 MDI), naphthalene-1,5-diisocyanate, methoxyphenyl-2,4-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 3,3'-dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate, phenylene diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorone diisocyanate, I PDI), 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), 1,4-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate, 1-methyl-2,6-dicyclohexylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 2,4'-dicyclohexylmethane diisocyanate, various isomers of 2,2'-dicyclohexylmethane diisocyanate, and mixtures thereof.

[0019] Suitable polymer polyols for use in the formulations and processes provided herein include both polyether polyols and polyester polyols, as well as other polymer polyols known to those skilled in the art. Suitable polyols have a molecular weight, preferably a number average molecular weight, of 300 to 5000, e.g., 500 to 4000 or 1000 to 3000, and typically have a functionality of 2 (i.e., are diols). If the polyol has a molecular weight less than 300, the thermoplastic elastomer composition may lose elasticity as a result of insufficient length of soft polyether segments. If the molecular weight is greater than 5000, it may be more difficult to achieve phase separation to produce soft and hard phases and / or it may be more difficult to balance hard and soft properties to provide a unique blend of elasticity and plasticity (e.g., the ability to use plastic molding equipment). Polyether polyols can be obtained by polymerization of alkylene oxides, for example C2 to C4 alkylene oxides such as ethylene oxide, 1,2-propylene oxide, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide, tetramethylene oxide and / or tetrahydrofuran.

[0020] Polyester polyols can be obtained by reacting a low molecular weight polyol with a polyester. Exemplary low molecular weight polyols include, but are not limited to, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-polypropylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, glycerol, diglycerol, sorbitol, pentaerythritol, sucrose, and bisphenol A. Exemplary polyesters include any polyester known to those skilled in the art for use in thermoplastic polyurethanes and can be prepared from organic dicarboxylic acids, such as C2-C12 unbranched aliphatic chains terminated with carboxylic acid groups, and difunctional or trifunctional alcohols, such as C2-C12 alkylene glycols or polyether alcohols. Alternatively or additionally, polyesters for use in polyester polyols can be prepared by the polymerization of lactones or hydroxycarboxylic acids.

[0021] Typically, a chain extender is also incorporated into the thermoplastic polyurethane. Suitable chain extenders include those known to those skilled in the art for use in TPUs, such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-butanediol, 1,5-pentanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol.

[0022] Typically, fumed silica is produced by an exothermic process in which a gaseous feedstock containing fuel, such as methane or hydrogen, oxygen, and a volatile silicon compound is supplied to a burner. The water formed by the combustion of the fuel in oxygen reacts with the volatile silicon compound, either in liquid or gas form, to produce silicon dioxide particles. These particles coalesce and agglomerate with the resulting fumed silica. Non-limiting examples of fumed silica include CAB-O-SIL® fumed silica available from Cabot Corporation, HDK® fumed silica available from Wacker Chemie AG, and AEROSIL® fumed silica available from Evonik Industries (Essen, Germany).

[0023] During the formation of thermoplastic polyurethanes, it is desirable to adjust the properties of the formulation to balance the formation of hydrogen bonds between the silica and the polymer with the formation of the polymer itself. Increasing the surface area of ​​the silica increases the available surface area for interaction with the polymer. Thus, in a preferred embodiment, the fumed silica used herein has a surface area of ​​at least 50 m as measured by nitrogen adsorption (ASTM D1993). 2 / g, e.g., at least 90m 2 / g, at least 150m 2 / g, at least 175m 2 / g, at least 200m 2 / g, 50-400m 2 / g or 175-300m 2 / g or 80~250m 2 / g or 150-200m 2 / g of surface area.

[0024] As produced, fumed silica is hydrophilic and has multiple Si-OH groups on its surface. These silanol groups can interact with alcohols through hydrogen bonding and with oxyalkylene groups of polyethers through acid group interactions. Combined with the thixotropy provided by the branched structure of silica, the interaction of silanols with the hydrophobic components of the prepolymer formulation can increase viscosity. Hydrophobizing the silica endcaps some of the silanol groups, reducing their thickening effect. Furthermore, the hydrophobizing treatment preferably does not interfere with the polymerization reaction.

[0025] It has been unexpectedly discovered that fumed silica hydrophobized with an agent that leaves short alkylsilyl groups on the surface can affect the polymer microstructure, e.g., the arrangement of hard and soft phases, without affecting the viscosity of the prepolymer composition, thereby improving its mechanical properties. Without being bound by any particular theory, the short alkylsilyl groups enable hydrogen bonding of unreacted silanols with the polyol components on the silica surface. In contrast, surface treatment with longer alkyl or siloxyl chains actually increases the viscosity of the prepolymer. Suitable surface treatments leave C1-C3 alkylsilyl groups on the surface, such as trimethylsilyl, vinylsilyl, dimethylsilyl, ethylsilyl, or methylethylsilyl groups. The silyl groups may be attached to the surface of the fumed silica by one, two, or three siloxane bonds, or may be linked to one or two adjacent alkylsilane groups via siloxane bonds. Surface treatments that leave longer chains, such as C5 or C8, and / or vinyl, acrylate ester, or methacrylate ester groups, can also be used. The appropriate length of the alkyl chain (either by itself or as a linker between the silicon atom and the vinyl, acrylate, or methacrylate group) varies depending on the ratio of long-chain polyol to short-chain polyol and should be controlled to reduce the viscosity of the prepolymer composition or any components mixed with the silica so that the silica does not reach yield stress. The silica particles should not be so hydrophobic that they form a separate network in the polyol, thereby increasing viscosity rather than primarily interacting with the polyol or polyether molecules.

[0026] In certain embodiments, the fumed silica may be hydrophobized with a silazane, such as hexamethyldisilazane, or an alkylsilane, such as dimethyldichlorosilane, methyltrimethoxysilane, methyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylchlorosilane, trimethylmethoxysilane, trimethylethoxysilane, ethyltriethoxysilane, ethyltrichlorosilane, ethyltrimethoxysilane, propyltrichlorosilane, propyltrimethoxysilane, propyltriethoxysilane, ethylmethyldichlorosilane, and other C1-C3 straight and branched alkylsilanes.

[0027] The components of the thermoplastic polyurethane can be combined and polymerized using any method known to those skilled in the art. Preferably, silica is combined with the thermoplastic polyurethane before polymerization. More preferably, fumed silica can be dispersed in a polyol by methods known to those skilled in the art and then combined with one or more remaining non-isocyanate components of the polyurethane before combining with the polyisocyanate and polymerizing. Because silica does not provide reinforcement itself, small amounts such as 0.1 wt %, e.g., 0.1 wt % to 10 wt %, e.g., 0.5 wt % to 7 wt %, or 1 wt % to 5 wt %, may be used in the thermoplastic polyurethane. The polyol may contain up to 15 wt% of fumed silica, for example, 0.2 wt% to 12 wt%, 0.5 wt% to 10 wt%, 1 wt% to 7 wt%, 2 wt% to 5 wt%, 3 wt% to 8 wt%, or 5 wt% to 13 wt%.

[0028] The use of fumed silica surfaces modified with short hydrophobic groups in an in situ polymerization process, in which the silica is combined with a polyol prior to polymerization, provides molded parts, particularly compression molded parts, with advantages that fumed silica simply masterbatched with a thermoplastic polyurethane cannot offer. In some embodiments, the thermoplastic polyurethane or molded thermoplastic polyurethane has a break elongation, as measured by ASTM D412, that is greater than the break elongation of a similar material having the same composition but without the silica, for example, at least 4% greater, at least 5% greater, at least 10% greater, at least 15% greater, at least 20% greater, or up to 60% greater. Alternatively or in addition, the thermoplastic polyurethane or molded thermoplastic polyurethane can have a rebound resilience, as measured by ASTM D-2362 (Bashore rebound), that is 4% or less less, e.g., 2% or less less, 0% or less less, 3% or less more, 6% or less more, 9% or less more, 12% or less more, or 18% or less more than that of a similar material having the same composition but without the silica. Alternatively or in addition, the thermoplastic polyurethane or molded thermoplastic polyurethane can have a compression set (Ct) that is greater, e.g., at least 10% greater, at least 15% greater, at least 20% greater, at least 30% greater, or at most 90% greater, than that of a similar material having the same composition but without the silica, as measured by ASTM D-395.

[0029] Other components known to those skilled in the art for use in thermoplastic polyurethanes can also be used.Exemplary additives include, but are not limited to, surfactants, fillers, flame retardants, nucleating agents, solvents, antioxidants, lubricants, mold release agents, dyes, pigments, plasticizers and UV stabilizers.Similarly, thermoplastic polyurethanes can be combined with other polymers.

[0030] Any thermoplastic polyurethane composition can benefit from the teachings herein. Exemplary thermoplastic polyurethane compositions are provided in WO 2012 / 069264, EP 111122, EP 922552, and U.S. Pat. No. 8,993,690, the contents of which are incorporated herein by reference.

[0031] The thermoplastic polyurethanes provided herein according to various embodiments can be used as midsoles and outsoles in footwear, as well as in wire insulation, hoses, films, wheels and tires, drilling / mining screens.

[0032] The present invention is further clarified by the following examples, which are merely illustrative in nature. [Example]

[0033] Example 1 Approximately 90m 2 Fumed silica with a surface area of ​​1 / g was surface-treated with hexamethyldisilazane to leave trimethylsilyl groups on the surface. The surface-treated silica was dispersed in polytetramethylene glycol (PTMG 1000 with 0.05-0.07% BHT as a stabilizer) with a molecular weight of 1000 using a FlackTek DAC600 Speedmixer to produce a 10 wt% dispersion. This dispersion was dehydrated in a 1 L reaction kettle under stirring and a vacuum of less than 2 mm Hg for 5 hours. Using the dehydrated dispersion, 100 g of each of 1 and 5 wt% dispersions was prepared in a 300 g Speedmixer cup by dilution with PTMG 1000 (Aldrich Chemistry with 0.05-0.07% BHT as a stabilizer) using a Flacktek DAC 400 FV Speedmixer at 2200 rpm.

[0034] A TPU was prepared using 1,4-butanediol (Nexeo Solutions) as the chain extender and diphenylmethane 4,4'-diisocyanate (4,4'-MDI, Mondur MB, Covestro) as the isocyanate, along with Dabco T-12 dibutyltin dilaurate catalyst (Air Products), in a polyol / chain extender / isocyanate equivalent ratio of 1 / 1 / 2 and an isocyanate index of 1.02. Prior to use, the 1,4-butanediol was dried in a 250 mL round-bottom flask at 70°C under vacuum and magnetic stirring at less than 2 mm Hg. The composition is shown in Table 1 below. [Table 1]

[0035] The TPU was prepared using the following procedure: (Degassed and preheated polyol and chain extender were weighed into a Speed ​​Mixer cup and mixed for at least 20 seconds at 2200 rpm using a Speed ​​Mixer (Flacktek DAC 400), followed by heating at 100°C for 10 minutes in an air-circulating oven.) Liquid isocyanate, conditioned at 70°C, was added via syringe to the polyol and chain extender mixture. All components were mixed in the Speed ​​Mixer at 2200 rpm for 30 seconds and transferred into a Teflon-sheet-covered aluminum mold preheated to 120°C. The gel time, measured as thread formation, was adjusted to approximately 1-2 minutes by adding Debco T-12 catalyst (Table 4). At the gel time, the mold was closed and the TPU was cured at 120°C for 2 hours at a pressure of approximately 20,000 psi. The samples were then post-cured in an air-circulating oven at 100°C for 20 hours. Following post-cure, the samples were aged at room conditions for 7 days before testing. Round samples and sheets were prepared and compressed in a Carver press to test the TPU properties.

[0036] Example 2 Approximately 250m 2Fumed silica having a surface area of ​​1 / g was surface treated with hexamethyldisilazane to leave trimethylsilyl groups on the surface. TPU was prepared with silica obtained as described in Example 1, except that the various components were mixed at 2200 rpm for 40 seconds before being transferred to the mold. The composition is shown in Table 2 below. [Table 2]

[0037] Example 3 Approximately 220m 2 Fumed silica having a surface area of ​​1 / g was surface treated with dimethyldichlorosilane to leave dimethylsilyl groups on the surface. TPU was prepared with silica obtained as described in Example 1, except that the various components were mixed at 2200 rpm for 40 seconds before being transferred to a mold. The composition is shown in Table 3 below. [Table 3]

[0038] Example 4 The TPU samples of Examples 1, 2 and 3 were analyzed for mechanical properties as listed in Table 4 below. [Table 4]

[0039] As shown in Figures 1 and 2, Shore A hardness increased with silica loading for all three silicas, and rebound resilience either remained unchanged or increased with the use of all three silicas relative to the comparative example. Modulus and elongation at break (Figures 3 and 4) also increased relative to the unfilled TPU, reaching a maximum at a loading of 3.17%. Consequently, silica improved toughness (area under the stress / strain curve) relative to the comparative example (Figure 5), reaching a maximum at a loading of 3.17 wt% for the higher surface area silica and 6.44% with the use of the lower surface area silica in Example 1. Abrasion resistance for the filled TPU systems (Figure 6) was acceptable, despite greater weight loss than the softer unfilled TPU system. Tear strength (Die C) (Figure 7) was improved with the addition of silica. The compression set (Ct) for all TPU systems (Figure 8) was small and not significantly affected by the addition of hydrophobic fumed silica. Similarly, the heat resistance of the TPU systems (Figure 9) was not significantly affected by the addition of hydrophobic fumed silica. Heat resistance was measured as the ratio of tensile stress at 50% strain (i.e., σ) at 50°C and room temperature. hot / σ cool ) is reported.

[0040] Example 5 The TPUs of Examples 1, 2, and 3 were combined with tetrahydrofuran (THF) at 10 wt %. Both the comparative sample and the silica-filled sample were dissolved. The fumed silica did not exhibit significant covalent crosslinking in the TPU. Additionally, the TPUs of Examples 2 and 3 were analyzed by differential scanning calorimetry (TA Instruments Universal V4 instrument) (Figure 5). With increasing silica concentration, the glass transition temperature (Tg) decreased and the melt transition temperature (Tm) increased, suggesting that the fumed silica is present in both the soft (representing Tg) and hard (representing Tm) segments of the polymer. The enthalpy of crystallization, calculated by integrating the area encompassed between the crystallization peak and the baseline of the DSC thermogram, also increased with silica loading. The changes in Tm and crystallization enthalpy suggest that silica affects the morphology of the hard segments of TPU, increasing the proportion of MDI segments in the hard segments and decreasing the amount of MDI in the soft and mixed phases of TPU. As the tensile behavior of TPU is driven by the movement of polymer chains in the hard crystalline segments, it behaves similarly to a reinforcing filler, and this change in morphology is expected to affect the mechanical properties of TPU. The change in MDI distribution in TPU is also expected to affect the solid-state 13 The sharp peaks of the samples with varying silica concentration in Example 1 are confirmed by C CPMAS NMR. 13 Figure 1 shows a shift in intensity from the C signal to a broad signal. The sharp signal indicates a short relaxation time and is caused by MDI in the soft segments, while the broad signal indicates a long relaxation time and is caused by MDI in the hard segments. Thus, an increase in the molar contribution to the broad signal indicates the presence of increased MDI in the hard segments. [Table 5] [Table 5A]

[0041] Example 6 Irogan A85 P4394 thermoplastic polyurethane (Huntsman) was mixed with the silica of Examples 1, 2, and 3 at the loading levels specified in Table 6 below. The fumed silica was incorporated into the commercial TPU by melt compounding using a Leistritz iMaxx coupled co-rotating twin-screw extruder with a lab-scale modular screw design (screw diameter = 27 mm, length / diameter ratio (L / D) = 48). The commercial TPU was fed into the hopper (main throat) using a Coperion K-Tron S60 gravimetric feeder, while the silica was introduced into the TPU melt stream via a Coperion K-Tron KT20 gravimetric side feeder.

[0042] The temperature profile for silica mixing from the feed zone to the die exit was: 165-170-170-170-170-170-170-170-170-160-160-160°C. For all compounds, 350 min -1 A screw speed of 1000 kJ / s and a throughput of 15 kg / hr were used. Prior to pelletization, the extrudates were cooled in a water bath and air-dried. After melt processing, the extruded material was dried overnight in a dehumidifying oven at 70°C. Silica-TPU composites were then injection molded using a Wittmann-Battenfeld Smart Power 60 / 210 injection molding machine. The mechanical properties of the resulting thermoplastics were measured as described above. Resilience data was not measured at low or intermediate loading levels for the silicas in Examples 1 or 2. Shore A hardness, modulus, elongation at break, and resilience are shown in Figures 10-13 (the neat polymer control is indicated by a dotted pattern). These figures demonstrate that the effect of fumed silica in the melt-mixed composites is less beneficial than when fumed silica is combined with the TPU formulation prior to polymerization. [Table 6]

[0043] The foregoing description of preferred embodiments of the present invention is provided for purposes of illustration and example. It is not intended to limit the invention to the precise form or to be exhaustive. Modifications and variations are possible in light of the above teachings or from the practice of the invention. The embodiments have been chosen and described to explain the principles and practical application of the invention and to enable those skilled in the art to utilize the invention in various embodiments and with various modifications suited to the particular uses expected. It is intended that the scope of the invention be defined by the appended claims and their equivalents.

Claims

1. a first polyol having a number average molecular weight of 300 to 5000; and a fumed silica having a surface containing C1 to C8 alkylsilyl groups or acrylate or methacrylate ester groups and a thickness of at least 50 m. 2 providing a polyol composition comprising at least 15 wt % or less of fumed silica having a surface area of ​​1 / g; combining the polyol composition with an aromatic, cycloaliphatic, or araliphatic diisocyanate to form a prepolymer composition; and polymerizing the prepolymer composition to form a thermoplastic polyurethane having a density of 0.8 g / mL or greater. A method for producing a thermoplastic polyurethane, comprising:

2. The method of claim 1 , wherein the step of polymerizing the prepolymer composition comprises adding a catalyst to the prepolymer composition.

3. The method of claim 1 or 2, wherein the prepolymer composition further comprises a chain extender.

4. The fumed silica has a thickness of 50 to 400 m 2 The method according to any one of claims 1 to 3, wherein the surface area of ​​the SiO2 nanoparticles is 1 / g.

5. The method according to any one of claims 1 to 4, wherein the fumed silica has C1 to C3 alkylsilyl groups on the surface.

6. The method of any one of claims 1 to 5, further comprising molding the thermoplastic polyurethane.

7. 7. The method of any one of claims 1 to 6, wherein the thermoplastic polyurethane composition has an elongation at break that is greater than the elongation at break of a control thermoplastic polyurethane having the same composition except that it does not contain the fumed silica.

8. The method of any one of claims 1 to 7, wherein the thermoplastic polyurethane composition has a rebound resilience that is 4% or less than that of a control thermoplastic polyurethane having the same composition except that it does not contain silica.

9. 9. The method of any one of claims 1 to 8, wherein the thermoplastic polyurethane has a compression set (Ct) that is greater than the compression set (Ct) of a control thermoplastic polyurethane having the same composition except that it does not have silica.

10. The thermoplastic polyurethane has the following characteristics: a) an elongation at break that is at least 4% greater, at least 5% greater, at least 10% greater, at least 15% greater, at least 20% greater, or no greater than 60% greater than the elongation at break of a control thermoplastic polyurethane having the same composition but without the silica; b) a rebound resilience that is no more than 2% less, no more than 0% less, no more than 3% more, no more than 6% more, no more than 9% more, no more than 12% more, no more than 15% more, or no more than 18% more than that of a control thermoplastic polyurethane having the same composition but without the silica; or c) a compression set that is at least 10% greater, at least 15% greater, at least 20% greater, at least 30% greater, or up to 90% greater than the compression set of a control thermoplastic polyurethane having the same composition but without the silica. The method of any one of claims 1 to 9, comprising one or more of:

11. 11. The method of any one of claims 1 to 10, wherein the prepolymer composition further comprises one or more surfactants, fillers, flame retardants, nucleating agents, solvents, antioxidants, lubricants, mold release agents, dyes, pigments, plasticizers, or UV stabilizers.

12. The method of any one of claims 1 to 11, wherein the polyol composition comprises no more than 15 wt% of the fumed silica.

13. A thermoplastic polyurethane produced by the method of any one of claims 1 to 12.

14. 14. The thermoplastic polyurethane of claim 13, comprising up to 10 wt% of said fumed silica.

15. 15. The thermoplastic polyurethane of claim 13 or 14, having an elongation at break that is greater than the elongation at break of a control thermoplastic polyurethane having the same composition but without the fumed silica.

16. The thermoplastic polyurethane of any one of claims 13 to 15, wherein the thermoplastic polyurethane is molded.

17. 17. The thermoplastic polyurethane of any one of claims 13 to 16, having a rebound resilience that is no more than 4% less than that of a control thermoplastic polyurethane having the same composition except that it does not contain silica.

18. 18. The thermoplastic polyurethane of any one of claims 13 to 17, which has a compression set (Ct) that is greater than the compression set (Ct) of a control thermoplastic polyurethane having the same composition but without the silica.

19. The following characteristics: a) an elongation at break that is at least 4% greater, at least 5% greater, at least 10% greater, at least 15% greater, at least 20% greater, or no greater than 60% greater than the elongation at break of a control thermoplastic polyurethane having the same composition but without the silica; b) a rebound resilience that is no more than 2% less, no more than 0% less, no more than 3% more, no more than 6% more, no more than 9% more, no more than 12% more, no more than 15% more, or no more than 18% more than that of a control thermoplastic polyurethane having the same composition but without the silica; or c) a compression set that is at least 10% greater, at least 15% greater, at least 20% greater, at least 30% greater, or up to 90% greater than the compression set of a control thermoplastic polyurethane having the same composition but without the silica. The thermoplastic polyurethane of any one of claims 13 to 18, having one or more of:

20. 1. A thermoplastic polyurethane composition having a density of at least 0.8 g / mL and comprising particulate fumed silica having C1-C8 alkylsilyl groups or acrylate or methacrylate ester groups on its surface, the thermoplastic polyurethane composition having an elongation at break greater than the elongation at break of a control thermoplastic polyurethane having the same composition except that it does not contain the fumed silica.

21. 21. The thermoplastic polyurethane of claim 20 which is molded.

22. 22. The thermoplastic polyurethane of claim 20 or 21, having a rebound resilience that is no more than 4% less than that of a control thermoplastic polyurethane having the same composition except that it does not contain silica.

23. 23. The thermoplastic polyurethane of any one of claims 20 to 22, having a compression set (Ct) that is greater than the compression set (Ct) of a control thermoplastic polyurethane having the same composition but without the silica.

24. The following characteristics: a) an elongation at break that is at least 4% greater, at least 5% greater, at least 10% greater, at least 15% greater, at least 20% greater, or no greater than 60% greater than the elongation at break of a control thermoplastic polyurethane having the same composition but without the silica; b) a rebound resilience that is no more than 2% less, no more than 0% less, no more than 3% more, no more than 6% more, no more than 9% more, no more than 12% more, no more than 15% more, or no more than 18% more than that of a control thermoplastic polyurethane having the same composition but without the silica; or c) a compression set that is at least 10% greater, at least 15% greater, at least 20% greater, at least 30% greater, or up to 90% greater than the compression set of a control thermoplastic polyurethane having the same composition but without the silica. The thermoplastic polyurethane of any one of claims 20 to 23, having one or more of:

25. The thermoplastic polyurethane of any one of claims 20 to 24, wherein the fumed silica is present in an amount of from 0.1 wt% to 10 wt%.

26. The fumed silica is 50 m 2 / g~400m 2 The thermoplastic polyurethane of any one of claims 20 to 25, having a surface area of ​​1 / g.

27. 27. The thermoplastic polyurethane of any one of claims 20 to 26, further comprising one or more surfactants, fillers, flame retardants, nucleating agents, solvents, antioxidants, lubricants, mold release agents, dyes, pigments, plasticizers, or UV stabilizers.

28. The thermoplastic polyurethane according to any one of claims 20 to 27, wherein the fumed silica has C1 to C3 alkylsilyl groups on the surface.

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