Process for the preparation of thermoplastic polyurethanes containing polypropylene ether

Abstract

This invention relates to a method for preparing thermoplastic polyurethane containing polypropylene ether, and to the thermoplastic polyurethane containing polypropylene ether obtained or obtainable by such method. The invention also relates to the use of said thermoplastic polyurethane containing polypropylene ether, and articles comprising or made from said thermoplastic polyurethane containing polypropylene ether.

Description

[0001] This invention relates to a method for preparing a thermoplastic polyurethane containing polypropylene ether, and to the thermoplastic polyurethane containing polypropylene ether obtained or obtainable by such method. The invention also relates to the use of said thermoplastic polyurethane containing polypropylene ether, and articles comprising or made from said thermoplastic polyurethane containing polypropylene ether. Existing technology

[0002] Thermoplastic polyurethane (TPU) has long been known. It holds significant industrial importance due to its combination of excellent mechanical properties and cost-effective thermoplastic processing. A wide range of mechanical properties can be achieved through the use of different chemical structural units. For example, Kunststoffe 68 (1978) pp. 819-825 or Kautschuk, Gummi, Kunststoffe 35 (1982) pp. 568-584 provide an overview of TPU, its properties, and applications. TPU is formed from linear polyols (typically polyethers or polyesters), organic diisocyanates, and short-chain diols (chain extenders). TPU is generally solvent-free and can be prepared continuously or discontinuously. Currently, the most commonly used industrial preparation methods are the belt method (GB 1057018 A) and the extruder method (DE 1964834 A-1 and DE 2059570 A-1).

[0003] To adjust performance, the constituent components can be varied over a relatively wide molar ratio. A molar ratio of macromolecular diol to chain extender of 1:1 to 1:12 has proven advantageous. The hardness of TPU can be adjusted over a wide range by varying the amount of chain extender used. The resulting product has a hardness range of approximately Shore A 40 to approximately Shore D 85.

[0004] To improve processing performance, particularly cycle time, TPUs exhibiting very rapid post-processing curing rates are of particular interest across the entire hardness range from approximately Shore A 40 to approximately Shore D 85, especially in the case of injection-molded products. For rigid and soft TPUs, the problem of chemical coupling between hard and soft segments often arises due to the significant polarity differences between these phases. Consequently, the overall potential of mechanical and processing properties is often not fully realized. Specialized methods have been explored to overcome these drawbacks.

[0005] W. Bräuer et al. described a method for preparing thermoplastic processable polyurethane (EP-A 1757632). The homogeneity of TPU was improved using a multi-stage OH prepolymer method. However, the improved homogeneity slowed down the curing speed of the TPU.

[0006] W. Bräuer et al. described a method for preparing soft thermoplastic polyurethane elastomers with low shrinkage and easy demolding (EP-A 1338614). The demolding properties of TPUs with Shore A 45 to Shore A 65 were improved by pre-expanding the soft segments. However, at extremely high hardness, this method has significant drawbacks because incompatibility arises between the hard and soft phases, preventing proper coupling between them. Therefore, the high molecular weight of TPU required for good mechanical properties cannot be obtained. Furthermore, due to the excessively high and fluctuating viscosity of the prepolymer stage, this method is also very unstable in practical applications, failing to work satisfactorily below Shore A 60, thus frequently causing extruder shutdowns.

[0007] To improve the low-temperature impact toughness of polyester-based TPUs in ski boot applications, polyether polyols with a molecular weight greater than 1600 g / mol are typically used as modifiers, such as polytetramethylene ether glycol (US4980445A) and polypropylene glycol ether (WO / 2018 / 158327). Due to the incompatibility between the hard and soft phases in TPU, which leads to poor coupling between the two phases, it is difficult to incorporate these polyethers as a pure soft phase into TPUs with a hardness higher than Shore D 60. Without modifiers, it is difficult to prepare rigid TPUs with good low-temperature impact toughness.

[0008] Polypropylene glycol or poly(propylene oxide) homopolymers (hereinafter also referred to as C3 polyether homopolymer polyols) are of particular interest as polyol components in the preparation of thermoplastic polyurethanes because they are inexpensive starting materials. For example, WO2020 / 109566 A1 discloses the use of polypropylene glycol in the preparation of thermoplastic polyurethanes, wherein a polypropylene glycol-based polyol reacts with a polyisocyanate.

[0009] However, a drawback of using polypropylene glycol as a polyol component is that it can currently only synthesize thermoplastic polyurethanes with relatively low Shore A or theoretical hardness, exhibiting sufficient mechanical properties and abrasion resistance. Rigid thermoplastic polyurethanes based on polypropylene glycol typically exhibit these typical properties only subtly or not at all, making them unsuitable for applications requiring significantly higher hardness. Furthermore, these thermoplastic polyurethanes have low low-temperature impact toughness, thus limiting their application in products exposed to low temperatures.

[0010] Better hardness and good low-temperature impact toughness can be achieved by using polytetrahydrofuran (hereinafter also known as C4 polyether homopolymer polyol). However, its disadvantages are that it is significantly more expensive than the aforementioned C3 polyether homopolymer polyol and has a poorer CO2 balance.

[0011] The object of this invention is therefore to provide a method for preparing polyether-containing thermoplastic polyurethanes with high hardness and improved mechanical properties, particularly enhanced tensile strength and improved low-temperature impact toughness. In particular, a more economical and efficient method for preparing polyether-containing thermoplastic polyurethanes should be provided, preferably one with improved CO2 balance.

[0012] Surprisingly, the objective is achieved by a method for preparing thermoplastic polyurethane by reacting a composition comprising or consisting of the following components: (A) At least one polyol, which is (A1) at least one C3 polyether homopolymer polyol and (A2) Optionally at least one C2 polyether homopolymer polyol and / or at least one C2 / C3 polyether block copolymer polyol, (B) At least one organic polyisocyanate, (C) At least one chain extender, (D) At least one non-oxidizing acid, (E) Optional at least one catalyst, (F) Optional at least one additive, auxiliary agent, and / or additional substance, and (G) Optional at least one monofunctional chain terminator, The method is characterized by comprising or consisting of the following steps: 1) Providing a first mixture M1 consisting of all amounts of component (A), a portion of component (B), and optionally a portion or all amounts of component (E), component (F), and / or component (G), and reacting it to obtain a second mixture (M2) containing at least one NCO functional prepolymer, wherein the molar ratio of component (B) to component (A) in step 1) is from 1.1:1.0 to 5.0:1.0. 2) In the presence of component (D) and optionally in further partial amounts of components (E), (F) and / or (G), react mixture M2 with the total amount of component (C) to obtain a third mixture (M3) containing at least one OH-functional prepolymer. Components (C) and (D) are added separately or as mixture M2a to mixture M2, wherein i) The pH value of mixture M2a is ≤6, preferably ≤5.5, more preferably ≤5.2 (at 23°C). or ii) If components (C) and (D) are added to mixture M2 separately, the amount of component (D) added should be such that the pH of the theoretical mixture of components (C) and (D) is ≤ 6, preferably ≤ 5.5, more preferably ≤ 5.2 (at 23°C). In order to determine the pH value, a mixture corresponding to the theoretical mixture was prepared and measured; 3) React mixture M3 with the remaining amount of component (B) and optionally the remaining amounts of component (E), component (F) and / or component (G) to obtain a thermoplastic polyurethane. In all method steps, the molar ratio of component (B) to the sum of components (A) and (C) is from 0.9 : 1.0 to 1.2 : 1.0.

[0013] The present invention also relates to thermoplastic polyurethanes obtained or obtainable according to the method of the present invention.

[0014] This invention also relates to the use of thermoplastic polyurethane according to the invention in the production of injection-molded articles, extruded articles, pressed articles, compression-molded articles, 3D-printed articles, mechanical, road and railway engineering articles, medical and dental articles, particularly orthodontic appliances for treating malocclusion, shoes, particularly ski boots, automotive industry articles, electrical industry articles, particularly cable sheaths, housings and plugs, consumer products, coatings, hoses, profiles, belts, films, fibers, nonwoven fabrics, textiles, damping elements, and sealing materials.

[0015] The present invention also relates to articles comprising or composed of thermoplastic polyurethane according to the present invention.

[0016] In this invention, C2 polyether homopolymer polyol refers to a polyol based on polyethylene glycol or poly(ethylene oxide), C3 polyether homopolymer polyol refers to a polyol based on polypropylene glycol or poly(propylene oxide), and C2 / C3 polyether block copolymer polyol refers to a polyol based on both polyethylene glycol or poly(ethylene oxide) and polypropylene glycol or poly(propylene oxide). The "C" in "C2", "C3", etc., represents a carbon atom, and the suffix number indicates the number of repeating units / carbon atoms in each polymer unit.

[0017] Preferably, in the method according to the invention, • The number average molecular weight of the C2 polyether homopolymer polyol is 500 to 4000 g / mol, preferably 1000 to 3000 g / mol; • The number average molecular weight of the C3 polyether homopolymer polyol is 500 to 8000 g / mol, preferably 1000 to 4500 g / mol; • The number average molecular weight of the C2 / C3 polyether block copolymer polyol is 1000 to 4000 g / mol, preferably 1500 to 2500 g / mol.

[0018] If component (A2) is used, the mass ratio of component (A1) to (A2) is ≥1:9, preferably ≥3:7, based on the total mass of components (A1) and (A2) in each case.

[0019] Preferably, component (A) is composed entirely of component (A1).

[0020] Organic polyisocyanates used as component (B) in steps 1) and 3) may include, for example, aliphatic, cycloaliphatic, aryliphatic, heterocyclic and aromatic polyisocyanates, as described in Justus Liebigs Annalen der Chemie, 562, pp. 75-136.

[0021] Specific examples include: aliphatic diisocyanates, such as 1,6-hexamethylene diisocyanate; cycloaliphatic diisocyanates, such as isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate and 1-methyl-2,6-cyclohexane diisocyanate and mixtures of their respective isomers, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate and 2,2'-dicyclohexylmethane diisocyanate and mixtures of their respective isomers; aromatic diisocyanates, such as 2,4 -Toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate, a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, carbamate-modified liquid 4,4'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate, 4,4'-diisocyanate-1,2-diphenylethane and 1,5-naphthalene diisocyanate. Preferred ingredients include 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and mixtures of diphenylmethane diisocyanate isomers containing >96% by weight of 4,4'-diphenylmethane diisocyanate, particularly 4,4'-diphenylmethane diisocyanate and 1,5-naphthalene diisocyanate. These diisocyanates can be used alone or as mixtures of each other. They can also be used with up to 15% by weight (based on the total amount of diisocyanate) of polyisocyanates, such as triphenylmethane-4,4',4''-triisocyanate or polyphenylmethylene polyisocyanate.

[0022] In another preferred embodiment of the method of the present invention, the component (B) used is a mixture of diphenylmethane diisocyanate isomers having a 4,4'-diphenylmethane diisocyanate content of more than 96% by weight (based on the total weight of component (B)), and the component (B) used is preferably 4,4'-diphenylmethane diisocyanate.

[0023] In another preferred embodiment of the method of the present invention, the component (B) used is 1,6-hexamethylene diisocyanate.

[0024] Suitable component (C) (chain extender) includes all linear diols with molecular weights from 62 g / mol to 500 g / mol known to those skilled in the art. These diols and / or their precursors may be derived from fossil or biological sources. Suitable diols are preferably aliphatic diols having 2 to 14 carbon atoms, such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, and dipropylene glycol. However, diesters of terephthalic acid with diols having 2 to 4 carbon atoms, such as diethylene glycol terephthalate or bis(1,4-butanediol) terephthalate, hydroxyalkyl ethers of hydroquinone, such as 1,4-di(hydroxyethyl)hydroquinone, and ethoxylated bisphenols are also suitable. Ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,4-di(hydroxyethyl)hydroquinone are particularly preferred as short-chain diols. A mixture of the above-mentioned chain extenders can also be used. In addition, a small amount of diamine and / or triol may be added.

[0025] In another preferred embodiment of the method of the present invention, the component (C) used is one or more diols selected from 1,2-ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethyl)hydroquinone, or a mixture of at least two of them. The component (C) used is preferably 1,2-ethylene glycol, 1,4-butanediol, or a mixture thereof, and the component (C) used is particularly preferably 1,4-butanediol.

[0026] Non-oxidizing acids (D) that can be used include, for example, phosphoric acid, p-toluenesulfonic acid monohydrate and adipic acid.

[0027] The catalysts (E) that can be used include those commonly known in polyurethane chemistry. Suitable catalysts include tertiary amines that are known and commonly used, such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine, 2-(dimethylaminoethoxy)ethanol, diazabicyclo[2.2.2]octane, etc., especially organometallic compounds, such as titanates, iron compounds, bismuth compounds, tin compounds such as tin diacetate, tin dioctanoate, tin dilaurate, or dialkyltin salts of aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate, etc. Preferred catalysts are organometallic compounds, especially titanates, iron compounds, or tin compounds. Dibutyltin dilaurate, tin dioctanoate, and titanates are particularly preferred.

[0028] Adaptable additives, auxiliaries, and contrasts (F) include, for example, lubricants such as fatty acid esters, their metal soaps, fatty acid amides, and silicon compounds; antiblocking agents; inhibitors; hydrolysis-resistant, light-resistant, heat-resistant, and color-resistant stabilizers; flame retardants; dyes; pigments; inorganic or organic fillers; nucleating agents; and reinforcing agents. Reinforcing agents are particularly fibrous reinforcing materials, such as inorganic fibers produced according to existing technology and possibly already sized. More detailed information on the aforementioned auxiliaries and contrasts can be found in professional literature such as JH Saunders and KC Frisch, “High Polymers,” Volume XVI, Polyurethanes, Parts 1 and 2, Interscience Publishers, 1962 or 1964; R. Gächter and H. Müller (eds.), *Taschenbuch der Kunststoff-Additive*, 3rd edition, Hanser Verlag, Munich, 1989; or DE-A 29 01 774.

[0029] The monofunctional chain terminator (G) that can be used includes monools such as 1-butanol, 1-hexanol, 1-octanol and stearyl alcohol, or monoamines such as 1-butanamine and stearylamine, to adjust the specific TPU molecular weight.

[0030] In step 1), the amount of the reactive component used to form the NCO functional prepolymer is selected such that the NCO / OH ratio of the polyisocyanate to the polyol in step 1) is 1.1:1 to 5.0:1.

[0031] Mix the components thoroughly and ensure that the NCO prepolymer reaction in step 1) is preferably completely converted (based on the polyol component).

[0032] Subsequently, component (C) is incorporated as a chain extender (step 2) to form a prepolymer with major OH functionality.

[0033] In this context, "major" means that at least 95 mol%, preferably at least 98 mol%, particularly preferably at least 99 mol%, more preferably at least 99.5 mol%, even more preferably at least 99.8 mol%, and most preferably 100 mol% of the total molar amount of the prepolymer formed is an OH functional prepolymer.

[0034] Component (D) can be mixed with component (C) or mixed in as a separate component.

[0035] In the first case, component (D) is used to adjust the pH of the mixture to the value described in claim 1.

[0036] In the second case, component (D) is added to the reactor in an amount such that the pH of the theoretical mixture of components (C) and (D) corresponds to the value described in claim 1. To determine the pH, a mixture corresponding to the theoretical mixture is prepared and measured.

[0037] pH values ​​were determined electrochemically according to DIN 19268:2021-10 at 23°C. Measurements were taken using a Solvotrode Easy Clean 6.0229.010 pH electrode from Methrom AG. This Solvotrode was supplied with a 2 mol / L LiCl ethanol solution as the reference electrolyte.

[0038] In step 3), the remaining amount of component (B) is added, wherein the NCO / OH ratio is from 0.9:1 to 1.2:1. Preferably, the same component (B) as in step 1) is used in step 3).

[0039] In a preferred embodiment of the method of the present invention, in step 2), the molar ratio of the NCO functional prepolymer to component (C) is less than 1.0. Therefore, component (C) exists in molar excess.

[0040] The reaction is preferably carried out under conditions where the isocyanate index is 0.9 to 1.2, more preferably 0.95 to 1.1, and particularly preferably 0.97 to 1.03. The isocyanate index (also called the index, NCO / OH index, or isocyanate index) is the quotient of the molar amount [mol] of the isocyanate groups actually used and the molar amount [mol] of the isocyanate reactive groups actually used. In other words, the index represents the percentage of the amount of isocyanate actually used relative to the stoichiometry, i.e., the amount of isocyanate calculated for an OH equivalent reaction. Equal amounts of NCO groups and NCO reactive hydrogen atoms correspond to an NCO / OH index of 1. The formula for calculating the isocyanate index is as follows: Index = [(moles of isocyanate groups) / (moles of isocyanate reactive groups)].

[0041] The method of the present invention can be carried out in a solvent or under solvent-free conditions. Preferably, the method is carried out under solvent-free conditions.

[0042] Thermoplastic polyurethane polymers can be prepared discontinuously (by hand casting) or continuously by the methods of this invention, with continuous operation, especially on an industrial scale (e.g., as an online one-off process), being preferred. The most common industrial methods for preparing TPU include belt methods (GB-A 1 057018) and extrusion methods (DE-A 1 964 834, DE-A2 059570, and US-A 5 795 948). Suitable equipment for preparing thermoplastic processable polyurethane polymers includes mixing equipment known per se, preferably mixing equipment operating at high shear energy. For continuous preparation, co-kneaders can be mentioned, for example, and extruders, such as twin-screw extruders and Buss kneaders, are preferred.

[0043] For example, thermoplastic polyurethane polymers can be prepared in a twin-screw extruder by preparing a prepolymer in the first stage of the extruder, followed by chain extender and polyisocyanate addition in the second stage. According to the invention, the metered addition of the chain extender (component (C)) must be carried out before the further metered addition of the polyisocyanate. The chain extender and polyisocyanate must not be added simultaneously to the same metering port of the extruder.

[0044] However, NCO and OH prepolymers can also be prepared in a separate upstream prepolymer reactor outside the extruder, discontinuously in a tank, or continuously in a tube or stirred tube with a static mixer (tubular mixer).

[0045] However, the OH prepolymer prepared in a separate prepolymer reactor can also be mixed with diisocyanate via a first mixing device (e.g., a static mixer) and with the remaining amount of polyisocyanate via a second mixing device (e.g., a mixing head). Similar to known belt methods, the reaction mixture is then continuously applied to a carrier, preferably a conveyor belt, where it is reacted until the material cures (optionally if the belt is heated) to obtain TPU.

[0046] In one preferred embodiment, the method is carried out at a reaction temperature of 140°C to 240°C. In another preferred embodiment, the method is carried out in an extruder at a reaction temperature of 140°C to 240°C.

[0047] It has proven advantageous to carry out the method of the present invention in the presence of nitrogen. This is beneficial because it minimizes the oxidation process that occurs during the preparation of TPU at high temperatures, such as 180°C to 240°C, thereby obtaining a significantly lower color value of the TPU granules. In the manual casting method, nitrogen is introduced into the reaction vessel and nitrogen protection is maintained at a rate of 1 to 10 liters per hour during the metered addition of the components. In the extrusion method, it is advantageous to introduce a nitrogen gas flow into the initial barrel of the extruder (e.g., barrels 1 to 3). The introduced nitrogen flow rate is 10 to 1000 liters per hour, preferably 100 to 750 liters per hour, and more preferably 100 to 500 liters per hour.

[0048] The thermoplastic polyurethane obtained according to the present invention has a theoretical hardness >30%, wherein the theoretical hardness is calculated according to the following formula: Theoretical hardness = (n(chain extender) × M(polyisocyanate) + m(chain extender)) / m 总 Where n = molar amount of each component, M = molar mass of each component, and m = mass of each component.

[0049] The thermoplastic polyurethane according to the present invention preferably has • Tensile strength greater than 17 MPa, preferably at least 18 MPa, more preferably at least 20 MPa, as measured according to ISO 53504 (2009-10), and / or • At least 30 KJ / m 2 Preferred strength is 50 to 140 KJ / m 2 Charpy impact toughness measured at -20°C according to DIN EN ISO179 / 1eA (2010).

[0050] In this invention, the Charpy impact toughness measured at -20°C according to DIN EN ISO 179 / 1eA (2010) refers to a measure of low-temperature impact toughness. The Charpy impact toughness test is performed on injection-molded specimens at -20°C according to DIN EN ISO 179 / 1eA (2010). The specimens have the following dimensions: length 80 ± 2 mm, width 10.0 ± 0.2 mm, and thickness 4.0 ± 0.2 mm. The specimens have a notch. The radius rN at the bottom of the notch is 0.25 ± 0.05 mm.

[0051] Experimental Section Examples and comparative examples: The present invention will be described below with reference to embodiments, but is not limited thereto.

[0052] Components used: • Polyol 1 = Polypropylene glycol (C3 polyether homopolymer polyol), initiator propylene glycol (poly(propylene oxide) homopolymer); OH value approximately 56; proportion of secondary terminal OH groups: >90%; • Polyol 2 = Poly(propylene oxide)-poly(ethylene oxide) block copolymer (C2 / C3 polyether block copolymer polyol): propylene glycol (initiator) and polymerized ethylene oxide (molar ratio of ethylene oxide units to propylene oxide units approximately 51:49); OH value approximately 56, primary terminal OH group ratio: >90%), KOH catalysis. • Polyol 3 = Polypropylene glycol (C3 polyether homopolymer polyol), initiator propylene glycol (poly(propylene oxide) homopolymer); OH value approximately 28; proportion of secondary terminal OH groups: >90% • Polyol 4 = Terathane® 1000 (Invista's commercially available product: polytetramethylene glycol; molecular weight approximately 2000 g / mol) • Polyol 5 = Terathane® 2000 (Invista's commercially available product: polytetramethylene glycol; molecular weight approximately 2000 g / mol) • BDO = 1,4-Butanediol (BDO, purity ≥99% by weight), purchased from Ashland Corporation • MDI = 4,4'-diphenylmethane diisocyanate (MDI, purity ≥99% by weight), purchased from Covestro AG.

[0053] The measurement method used: • The OH value was titrated according to DIN 53240-2:2007-11. • Tensile test: Measured according to ISO 53504 (2009-10), with a tensile speed of 200 mm / min; • Charpy impact toughness test (low-temperature impact toughness): The Charpy impact toughness of the injection-molded specimens was tested at -20°C according to DIN EN ISO 179 / 1eA (2010). The specimens had the following dimensions: length 80 ± 2 mm, width 10.0 ± 0.2 mm, and thickness 4.0 ± 0.2 mm. The specimens were notched. The radius rN at the bottom of the notch was 0.25 ± 0.05 mm. • pH measurement: based on DIN 19268:2021-10 Dissolve 10 g of acid in 90 g of 1,2-ethylene glycol aqueous solution (10% water content). Dilute the solution with butanediol to the concentration required for TPU preparation. Measure the pH of the mixture.

[0054] Instruments used: Titrando 905, equipped with two Dosino 800s, Tiamo 2.5 software, Solvotrode Easy Clean 6.0229.010 electrodes, Metrohm AG.

[0055] Example: Table 1 illustrates the present invention through several examples. The preparation method used is described below.

[0056] Preparation (discontinuous method): Stage 1: A portion of MDI (see Table 1) is reacted with 1 mole of polyol or a mixture of polyols at approximately 140°C with stirring until the conversion is >90 mol%, based on the polyol.

[0057] Stage 2: Add the chain extender to the stirred reaction mixture and stir vigorously for about 10 seconds. Then add acid in the specified amounts (Table 1).

[0058] Phase 3: Add a portion of MDI from Phase 2 (see Table 1) to the stirred reaction mixture. Continue stirring the reaction mixture for 20 seconds, then pour it onto a metal plate and heat-treat at 120°C for 30 minutes.

[0059] The resulting TPU castings were shredded and granulated. The granules were processed using an Arburg Allrounder 470S injection molding machine at a temperature range of 180 to 230°C and a pressure range of 650 to 750 bar at an injection flow rate of 10 to 35 cm³ / s to obtain rods (mold temperature: 40°C; rod size: 80x10x4mm) or sheets (mold temperature: 70°C; size: 125x50x2 mm).

[0060] Determine the mechanical properties (tensile strength and elongation) and Charpy low-temperature impact toughness of the manufactured TPU product.

[0061] Preparation (continuous methods, e.g., reactive extruders): Similar to discontinuous experiments, TPU can also be prepared continuously, for example using a twin-screw reactive extruder (but preparation is not limited to this method; see “belt method”).

[0062] A portion 1 of MDI, preheated to 60°C, is metered into a tube equipped with a pin mixer using a gear pump. A second gear pump, heated to 140°C, pumps a polyol or polyol mixture into the same tube. The tube has an aspect ratio of 8:1. The reaction mixture flows continuously into a connected twin-screw extruder, which is externally heated to 140°C to 220°C. The acid is metered into the chain extender, and the chain extender and portion 2 of MDI are added at the midpoint of the screw. The screw shaft rotates at 300 rpm. At the screw tip, the hot melt is granulated and cooled. The granules are then injection molded into test specimens, and the properties listed in the table are measured.

[0063] Examples 9, 11, and 12 describe a continuous method (extruder method).

[0064] - Comparative Examples 1 and 2 (Table 1) are TPU formulations without added acid. Comparative Example 1 has very low tensile strength. Under the condition of increased theoretical hardness (Comparative Example 2), the TPU cannot be prepared and / or cannot be processed by injection molding.

[0065] - Examples 3-12 (Table 1) show TPU formulations with added acid that exhibit good tear strength.

[0066] Examples 3, 10, 11, and 12 (Tables 2 and 1) show TPU formulations with added acid that exhibit improved theoretical hardness, good tear strength, and good low-temperature impact toughness (Charpy impact toughness). The Charpy impact toughness is comparable to that of TPUs based on C4 polyether homopolymer polyols. However, using C3 polyether homopolymer polyols is more economical, and these polyols have a better CO2 balance than C4 polyether homopolymer polyols.

Claims

1. A method for preparing thermoplastic polyurethane by reacting a composition comprising or consisting of the following components: (A) At least one polyol, which is (A1) at least one C3 polyether homopolymer polyol and (A2) Optionally at least one C2 polyether homopolymer polyol and / or at least one C2 / C3 polyether block copolymer polyol, (B) At least one organic polyisocyanate, (C) At least one chain extender, (D) At least one non-oxidizing acid, (E) Optional at least one catalyst, (F) Optional at least one additive, auxiliary agent, and / or additional substance, and (G) Optional at least one monofunctional chain terminator, Its features are, The method includes or consists of the following steps: 1) Providing a first mixture M1 consisting of all amounts of component (A), a portion of component (B), and optionally a portion or all amounts of components (E), (F), and / or (G), and reacting it to obtain a second mixture (M2) containing at least one NCO functional prepolymer, wherein the molar ratio of component (B) to component (A) in step 1) is from 1.1 : 1.0 to 5.0 : 1.

0. 2) In the presence of component (D) and optionally in further partial amounts of components (E), (F) and / or (G), react mixture M2 with the total amount of component (C) to obtain a third mixture (M3) containing at least one OH-functional prepolymer. Components (C) and (D) are added to mixture M2 separately or as mixture M2a, wherein i) The pH value of mixture M2a is ≤6, preferably ≤5.5, more preferably ≤5.2 (at 23°C). or ii) If components (C) and (D) are added to mixture M2 separately, the amount of component (D) added should be such that the pH of the theoretical mixture of components (C) and (D) is ≤ 6, preferably ≤ 5.5, more preferably ≤ 5.2 (at 23°C). In order to determine the pH value, a mixture corresponding to the theoretical mixture was prepared and measured; 3) React mixture M3 with the remaining amount of component (B) and optionally the remaining amounts of component (E), component (F) and / or component (G) to obtain a thermoplastic polyurethane. In all method steps, the molar ratio of component (B) to the sum of components (A) and (C) is from 0.9 : 1.0 to 1.2 : 1.

0.

2. The method according to claim 1, characterized in that: - The number average molecular weight of the C3 polyether homopolymer polyol is 500 to 8000 g / mol, preferably 1000 to 4500 g / mol.

3. The method according to claim 2, characterized in that: - The number average molecular weight of the C2 polyether homopolymer polyol is 500 to 4000 g / mol, preferably 1000 to 3000 g / mol. and / or - The number average molecular weight of the C2 / C3 polyether block copolymer polyol is 1000 to 4000 g / mol, preferably 1500 to 2500 g / mol.

4. The method according to any one of claims 1 to 3, characterized in that, The theoretical hardness of thermoplastic polyurethane is >30%, where the theoretical hardness is calculated using the following formula: Theoretical hardness = (n (chain extender) x M (polyisocyanate) + m (chain extender)) / m 总 Where n = molar amount of each component, M = molar mass of each component, and m = mass of each component.

5. The method according to any one of claims 1 to 4, characterized in that, The polyisocyanate of component (B) is selected from the group consisting of or composed of the following substances: 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate, 1-methyl-2,6-cyclohexane diisocyanate and mixtures of the corresponding isomers, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, 2,2'-dicyclohexylmethane diisocyanate and mixtures of the corresponding isomers, 2,4-toluene diisocyanate, Mixtures of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate, mixtures of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, carbamate-modified liquid 4,4'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate, 4,4'-diisocyanate-1,2-diphenylethane, 1,5-naphthalene diisocyanate and mixtures thereof.

6. The method according to any one of claims 1 to 5, characterized in that, The chain extender of component (C) is selected from the group consisting of or composed of the following substances: ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, dipropylene glycol, diesters of terephthalic acid and diols having 2 to 4 carbon atoms, such as diethylene glycol terephthalate or bis(1,4-butanediol) terephthalate, hydroxyalkyl ethers of hydroquinone, such as 1,4-di(hydroxyethyl)hydroquinone, and ethoxylated bisphenols and mixtures thereof.

7. The method according to any one of claims 1 to 6, characterized in that, The non-oxidizing acid of component (D) is selected from the group consisting of or composed of the following substances: phosphoric acid, p-toluenesulfonic acid monohydrate, adipic acid and mixtures thereof.

8. The method according to any one of claims 1 to 7, characterized in that: - The catalyst of component (E) is selected from the group consisting of or composed of: tertiary amines, such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine, 2-(dimethylaminoethoxy)ethanol, diazabicyclo[2.2.2]octane, organometallic compounds such as titanates, iron compounds, bismuth compounds, tin compounds such as tin diacetate, tin dioctanoate, tin dilaurate, or dialkyltin salts of aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate, and mixtures thereof. and / or - The additives, auxiliaries and / or additional substances of component (F) are selected from the group consisting of or composed of: lubricants such as fatty acid esters, their metal soaps, fatty acid amides and silicon compounds, anti-blocking agents, inhibitors, anti-hydrolysis, anti-light, anti-heat and anti-discoloration stabilizers, flame retardants, dyes, pigments, inorganic or organic fillers, nucleating agents and reinforcing agents and mixtures thereof. and / or - The monofunctional chain terminator of component (G) is selected from the group consisting of or composed of: monools such as 1-butanol, 1-hexanol, 1-octanol and stearyl alcohol, or monoamines such as 1-butanamine and stearylamine and mixtures thereof.

9. The method according to any one of claims 1 to 8, characterized in that, The reaction is carried out under conditions where the isocyanate index is 0.9 to 1.2, more preferably 0.95 to 1.1, and particularly preferably 0.97 to 1.

03.

10. The thermoplastic polyurethane obtained or obtainable by the method according to any one of claims 1 to 9.

11. The thermoplastic polyurethane according to claim 10, characterized in that, The thermoplastic polyurethane has - A tensile strength greater than 17 MPa, preferably at least 18 MPa, more preferably at least 20 MPa, as measured according to ISO 53504 (2009-10), and / or - a Charpy impact toughness measured at -20°C according to DIN EN ISO 179 / 1 eA (2010) of at least 30 KJ / m 2 , preferably 50 to 140 KJ / m 2 .

12. The thermoplastic polyurethane according to claim 10 or 11 is used in the production of injection-molded articles, extruded articles, pressed articles, compression-molded articles, 3D-printed articles, mechanical, road and railway engineering articles, medical and dental articles, especially orthodontic appliances for treating malocclusion, shoes, especially ski boots, automotive industry articles, electrical industry articles, especially cable sheaths, housings and plugs, consumer products, coatings, hoses, profiles, belts, films, fibers, nonwovens, textiles, damping elements or sealing materials.

13. Articles comprising or composed of the thermoplastic polyurethane as described in claim 10 or 11.

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