1. Patent Search
  2. Details

THERMOPLASTIC ALIPHATIC POLYURETHANE POLYMER HAVING A LOWER CRYSTALLIZATION ENTHALPY

20230357483 · 2023-11-09

    Inventors

    Cpc classification

    International classification

    Abstract

    The present invention relates to thermoplastic aliphatic polyurethane polymers, in which the ratio M.sub.z/M.sub.w is in a range from 2.3 to 6 and which have a degree of crystallinity χ in the range from 10% to 51%, to compositions containing such polyurethane polymers, to a method for the production thereof and to the use of these polyurethane polymers.

    Claims

    1. A thermoplastic aliphatic polyurethane polymer, wherein the ratio M.sub.z/M.sub.w of the thermoplastic aliphatic polyurethane polymer is in a range from 2.3 to 6, where M.sub.z is the centrifuge-average molar mass and M.sub.w is the mass-average molar mass, in each case determined by gel permeation chromatography, in which the sample was dissolved in a solution of potassium trifluoroacetate in hexafluoroisopropanol at a concentration of 2 mg/cm.sup.3 and a polymethylmethacrylate standard was used, and the thermoplastic aliphatic polyurethane polymer has a degree of crystallinity χ in the range from 10% to 51%, where the degree of crystallinity χ is determined according to the following equation:
    χ=(ΔH.sub.C,polymer/ΔH.sub.crystal,100%).Math.100%, where ΔH.sub.C,polymer is the measured enthalpy of crystallization in [J/g] of the thermoplastic aliphatic polyurethane polymer, determined by differential scanning calorimetry (DSC) in accordance with DIN EN ISO 11357-1:2017-02 at a cooling rate of 10 K/m in in the range from 250° C. to 20° C., and ΔH.sub.crystal,100% is the enthalpy of fusion of the corresponding 100%-crystalline thermoplastic aliphatic polyurethane polymer in [J/g], determined by differential scanning calorimetry and X-ray scattering analysis.

    2. The thermoplastic aliphatic polyurethane polymer as claimed in claim 1, wherein the thermoplastic aliphatic polyurethane polymer has a degree of crystallinity χ in the range from 20% to 51%.

    3. The thermoplastic aliphatic polyurethane polymer as claimed in claim 1, wherein the ratio M.sub.w/M.sub.n of the thermoplastic aliphatic polyurethane polymer is in a range from 3 to 8. where M.sub.n is the number-average molar mass and M.sub.w is the mass-average molar mass, in each case determined by gel permeation chromatography, in which the sample was dissolved in a solution of potassium trifluoroacetate in hexafluoroisopropanol at a concentration of 2 mg/cm.sup.3 and a polymethylmethacrylate standard was used.

    4. The thermoplastic aliphatic polyurethane polymer as claimed in claim 1, wherein the ratio M.sub.z/M.sub.w of the thermoplastic aliphatic polyurethane polymer is in a range from 2.5 to 5, where M.sub.z is the centrifuge-average molar mass and M.sub.w is the mass-average molar mass, in each case determined by gel permeation chromatography, in which the sample was dissolved in a solution of potassium trifluoroacetate in hexafluoroisopropanol at a concentration of 2 mg/cm.sup.3 and a polymethylmethacrylate standard was used.

    5. The thermoplastic aliphatic polyurethane polymer as claimed in claim 1, wherein the thermoplastic aliphatic polyurethane polymer is obtained by reacting one or more aliphatic polyisocyanates having a molecular weight in the range from ≥140 g/mol to ≤400 g/mol, with one or more aliphatic polols.

    6. The thermoplastic aliphatic polyurethane polymer as claimed in claim 1, wherein the thermoplastic aliphatic polyurethane polymer consists to an extent of at least 80% by weight of the reaction product of the reaction of hexamethylene-1,6-diisocyanate with butane-1,4-diol, based on the total mass of the thermoplastic aliphatic polyurethane polymer.

    7. The thermoplastic aliphatic polyurethane polymer as claimed in claim 1, characterized in that the thermoplastic aliphatic polyurethane polymer has a peak crystallization temperature in the range from 130° C. to 145° C., determined by differential scanning calorimetry (DSC) in accordance with DIN EN ISO 11357-1:2017-02.

    8. A process for preparing a thermoplastic aliphatic polyurethane polymer as claimed in claim 1, wherein, in a first step, at least one or more aliphatic polyisocyanates are reacted with one or more aliphatic polyols, optionally in the presence of a catalyst and/or auxiliaries and additives, to give at least one prepolymer, and the at least one prepolymer obtained in the first step is reacted in a second step with at least one chain extender to give the thermoplastic aliphatic polyurethane polymer.

    9. The process as claimed in claim 8, wherein, independently of one another, as aliphatic polyisocyanate, an aliphatic diisocyanate is used and, as aliphatic polyol, an aliphatic diol is used.

    10. A composition comprising at least one thermoplastic aliphatic polyurethane polymer as claimed in claim 1 and at least one additive and/or a further thermoplastic polymer.

    11. A thermoplastic molding compound, comprising at least one composition as claimed in claim 10.

    12. A molding, film and/or fiber, comprising at least one thermoplastic polyurethane polymer as claimed in claim 1, at least one thermoplastic molding compound as claimed in claim 11, or at least one composition as claimed in claim 10.

    13. A method of producing molding, film, and/or fiber, comprising producing the molding, film, and/or fiber with the thermoplastic polyurethane polymer as claimed in claim 1, a molding compound including the thermoplastic polyurethane polymer as claimed in claim 1, or composition including the thermoplastic polyurethane polymer as claimed in claim 1.

    14. A method of producing a composition, a thermoplastic molding compound, or a polyurethane dispersion, comprising producing the composition, the thermoplastic molding compound, or the polyurethane dispersion with the thermoplastic aliphatic polyurethane polymer as claimed in claim 1.

    15. An article comprising the thermoplastic aliphatic polyurethane polymer as claimed in claim 1 or a composition including the thermoplastic aliphatic polyurethane polymer as claimed in claim 1.

    Description

    [0111] The present invention is more particularly elucidated hereinbelow with reference to FIGS. 1 and 2. These figures show:

    [0112] FIG. 1 shows an apparatus for performing the process according to the invention, and

    [0113] FIG. 2 is a thermogram from a differential thermal analysis of a polyurethane which [0114] a) was prepared by the process according to the invention and [0115] b) was prepared by a process not in accordance with the invention.

    EXAMPLES

    [0116] The present invention is elucidated further by the examples that follow, but without being restricted thereto.

    [0117] Two thermoplastic polyurethane polymers, which had been prepared by different synthesis methods, were compared with one another, during which the enthalpy of fusion and the molecular weight of these two polyurethane polymers were analyzed.

    Determination of the Enthalpy of Crystallization

    [0118] The enthalpy of crystallization is determined by means of differential scanning calorimetry (DSC) on the basis of DIN EN ISO 11357-1:2017-02. The measurement was effected on a Q2000 instrument (TA Instruments). Two heatings and a cooling in the range from 20° C. to 250° C. with a heating/cooling rate of 10 K/min were performed. The sample mass was about 6 mg. The purge gas flow (nitrogen) was 50 ml/min.

    Determination of the Molecular Weight

    [0119] GPC method for the determination of M.sub.n and M.sub.w:

    [0120] The number-average and the mass-average molar mass were determined using gel permeation chromatography (GPC), in which the sample to be analyzed was dissolved in a solution of potassium trifluoroacetate in hexafluoroisopropanol at a concentration of 2 mg/cm.sup.3 and a polymethylmethacrylate standard was used. [0121] Pump: 515 HPLC pump (Waters GmbH) [0122] Detector: Smartline 2300 RI detector (Knauer Wissenschaftliche Gerate GmbH) [0123] Columns: 1 precolumn, 1000 Å PSS PFG 7 μm, 300 Å PSS PFG 7 μm, 100 Å PSS PFG 7 μm in this sequence (PSS Polymer Standards Service GmbH) [0124] Degassing: PSS Degasser (PSS Polymer Standards Service GmbH) [0125] Injection volume: 100 microliters [0126] Temperature: 23° C.-25° C. [0127] Molar mass standard: Polymethylmethacrylate standard kit (PSS Polymer Standards Service GmbH)

    [0128] Unless explicitly stated otherwise, in the present invention, the centrifuge-average molar mass M.sub.z was determined by means of gel permeation chromatography (GPC) using polymethylmethacrylate as standard. The sample to be analyzed was dissolved in a solution of 3 g of potassium trifluoroacetate in 400 cubic centimeters of hexafluoroisopropanol (sample concentration about 2 mg/cubic centimeter), and then applied via a pre-column at a flow rate of 1 cubic centimeter/minute and then separated by means of three series-connected chromatography columns, first by means of a 1000 Å PSS PFG 7 μm chromatography column, then by means of a 300 Å PSS PFG 7 μm chromatography column and lastly by means of a 100 Å PSS PFG 7 μm chromatography column The detector used was a refractive index detector (RI detector). The number-average molecular weight was calculated from the data obtained by the gel permeation chromatography measurement with the aid of the following equation:

    [00004] M _ n = .Math. i n i ⁢ M i .Math. i n i ⁢ g / mol

    where
    M.sub.i is the molar mass of the polymers of the fraction i, such that M.sub.i<M.sub.i+1 for all i, in g/mol, n.sub.i is the molar amount of the polymer of the fraction i, in mol.

    [0129] The mass-average molar mass (M.sub.w) was likewise calculated from the data obtained by the gel permeation chromatography measurement with the aid of the following equation:

    [00005] M _ w = .Math. i n i ⁢ M i 2 .Math. i n i ⁢ M i ⁢ g / mol

    where:
    M.sub.i is the molar mass of the polymers of the fraction i, such that M.sub.i<M.sub.i+1 for all i, in g/mol, n.sub.i is the molar amount of the polymer of the fraction i, in mol.

    [0130] The centrifuge-average molecular weight was calculated from the data obtained by the gel permeation chromatography measurement with the aid of the following equation:

    [00006] M _ z = .Math. i n i ⁢ M i 3 .Math. i n i ⁢ M i 2

    where
    M.sub.i is the molar mass of the polymers of the fraction i, such that M.sub.i<M.sub.i+1 for all i, in g/mol, n.sub.i is the molar amount of the polymer of the fraction i, in mol.

    Example 1 According to the Invention

    [0131] An annular gear pump 2 (HNP, MZR 7255) was used to convey a polyisocyanate stream A consisting of hexamethylene 1,6-diisocyanate from a 250 liter reservoir 1 for hexamethylene 1,6-diisocyanate to a static mixer 7. The throughput of the polyisocyanate stream A was measured using a mass flow meter 3 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 12 kg/h). The temperature of the hexamethylene 1,6-diisocyanate was room temperature.

    [0132] An annular gear pump 5 (HNP, MZR 7205) was used to convey a polyol stream B consisting of butane-1,4-diol from a 250 liter reservoir 4 for butane-1,4-diol to the static mixer 7. The throughput of the polyol stream B was measured using a mass flow meter 6 (Bronkhorst, Mini Con-Flow M1X, max. flow rate 8 kg/h). The temperature of the butane-1,4-diol was 40° C.

    [0133] In the static mixer 7 (Sulzer SMX, diameter 6 mm, ratio of length to diameter L/D=10), polyisocyanate stream A and polyol stream B were mixed with one another so as to obtain a mixed stream C. The mass flow rates of the polyisocyanate stream A and of the polyol stream B were adjusted such that the isocyanate index in the mixed stream C was 78.

    [0134] Mixed stream C was fed via a junction 28 into the circulation conduit 29 in which a circulation stream D was circulated. Downstream of the junction 28, the circulation stream D was guided into a static mixer 8 (static mixer equivalent to Sulzer SMX, internal diameter 34 mm, L/D=20). The temperature of prepolymer stream D was 182° C.

    [0135] Downstream of static mixer 8, circulation stream D was guided into a temperature-controllable static mixer 9. The oligomerization of the circulation stream D with the mixed stream C took place there for the most part and the heat of reaction formed was removed. The temperature-controllable static mixer 9 was of similar construction to a Sulzer SMR reactor with internal crossed tubes. It had an internal volume of 1.9 liters and a heat exchange surface area of 0.44 square meters. It was heated/cooled with heat-transfer oil. The heating medium temperature at the inlet was 180° C.

    [0136] The circulation stream D exited the temperature-controllable static mixer 9 at a temperature of 183° C. Downstream of the temperature-controllable static mixer 9, a prepolymer stream E was separated from circulation stream D at a junction 11, and the circulation stream D was guided onward to a gear pump 10. The prepolymer stream E was guided into an extruder 18.

    [0137] The pressure of circulation stream D was increased in a gear pump 10. The gear pump 10 (Witte Chem 25, 6-3) had a volume per revolution of 25.6 cubic centimeters and a speed of 50 revolutions per minute. Circulation stream D was combined with mixed stream C downstream of the pump at junction 28, as already described.

    [0138] Circulation conduit 29 consisted of jacketed pipe conduits heated with thermal oil. The heating medium temperature was 182° C. The static mixer 8, the temperature-controllable static mixer 9 and the gear pump 10 consisted of apparatuses heated with thermal oil. The heating medium temperature was 182° C.

    [0139] The reactive extrusion was conducted in an extruder 18 at a temperature of 200° C. and a speed of 66 revolutions per minute. The extruder 18 was a ZSK 26 MC from Coperion, with a screw diameter of 26 mm and a length to diameter ratio of 36 to 40.

    [0140] The extruder 18 had a venting means 17 that was operated at a negative pressure of about 1 mbar relative to standard pressure, and in which prepolymer stream E was freed of any inert gases entrained with the polyisocyanate stream A and the polyol stream B, and possible gaseous reaction products.

    [0141] A micro annular gear pump 15 (MZR 6355 from HNP) was used to withdraw an isocyanate feed stream F consisting of hexamethylene 1,6-diisocyanate from reservoir 1. The throughput of the isocyanate feed stream F was measured by means of a mass flow meter 16 (Bronkhorst, Mini Cori-Flow M1X, maximum flow rate 2 kg/h). The temperature of the hexamethylene 1,6-diisocyanate was room temperature. Isocyanate feed stream F was guided into the extruder 18 downstream of prepolymer stream E. In the extruder 18, the prepolymer stream E was reacted with the isocyanate feed stream F at an isocyanate index of 99 to give a thermoplastic polyurethane G.

    [0142] A devolatilizer 19 arranged in the last third of the extruder 18 in flow direction was used to free the thermoplastic polyurethane G of volatile constituents at 200 mbar below standard pressure with the aid of a vacuum dome arranged on top of a devolatilization shaft of the extruder. The thermoplastic polyurethane G after exiting from the extruder 18 through two nozzles was cooled in a water bath 20 filled with deionized water (DM water) and chopped into pellets by means of a pelletizer 21.

    TABLE-US-00001 TABLE 1 Material streams in the preparation of the TPU in example 1 [kg/h] Stream A (HDI) 2.911 Stream B (BDO) 2.000 Stream J (HDI) 0.784 Stream E (prepolymer) 120

    Reference Example 2

    [0143] In a stirred tank (250 ml), 24.59 g of butane-1,4-diol was heated to 90° C. while stirring (170 revolutions per minute (rpm)) and with introduction of nitrogen, for 30 minutes. Subsequently, 45.39 g of HDI was metered continuously into the butanediol over a period of 45 minutes. In the course of this, the temperature of the reaction mixture was increased constantly by 4° C. per minute until a temperature of 190° C. had been attained (25 minutes). As soon as a product temperature of 190° C. had been attained, the stirrer speed was increased to 300 rpm. The temperature in the stirred tank was kept constant between 190° C. and 200° C.

    [0144] After the metered addition of HDI had ended, the melt was stirred for a further 5 minutes. Subsequently, it was poured into an aluminum mold in the hot state.

    Results

    [0145] The enthalpy of fusion and the molecular weights of the thermoplastic polyurethanes obtained from examples 1 and 2 were analyzed by the methods described above. The results are compiled in table 2:

    TABLE-US-00002 TABLE 2 Enthalpy of fusion and molecular weight of the polyurethanes obtained Example 1 according Comparative to the invention example 2 M.sub.w [g/mol] 58510 60020 M.sub.w/M.sub.n 4.97 2.55 M.sub.z/M.sub.w 2.71 2.05 Enthalpy of crystallization ΔH.sub.C 93.5 97.7 [J/g] Onset crystallization 150.1 152.7 temperature [C. °] Peak crystallization 143.6 146.8 temperature [C. °] ΔH.sub.crystal, 100% [J/g] 188 188 Degree of crystallinity χ [%] 49.7 52.0

    [0146] The DSC thermograms of the two materials analyzed are shown in FIG. 2. The thermoplastic polyurethanes from examples 1 and 2 each have a mass-average molecular weight in a similar range of 58 000 g/mol to approx. 60 000 g/mol and also have similar melting temperatures in the range from 183° C. to 186° C. However, the TPU according to the invention has an enthalpy of crystallization that is 4.3% lower compared to the TPU of the comparative example. Due to the lower enthalpy of crystallization of the TPU according to the invention, in the further processing by melting and subsequent shaping less energy needs to be supplied for the melting than for the further processing of the TPU from the comparative example. If the same amount of energy is used to melt the thermoplastic polyurethanes from each of the two examples, the TPU according to the invention melts quicker. The thermoplastic polyurethane of the invention furthermore has the advantage that, compared to the example not in accordance with the invention, it leads to lower shrinkage and hence to higher dimensional stability during further processing, for example extrusion or injection molding.