OPTIMUM COMPOSITION OF TPU PRODUCT FOR TIRES

Abstract

A molded body contains foamed pellets, containing a composition (M1) containing a thermoplastic elastomer (TPE-1), having a ratio of average surface area to average volume of the pellets (A/V) determined according to method-example 1 and 2 in a range of from 1.4 to 3.0. A process for preparing the molded body involves providing the foamed pellets comprising the composition (M1), and fusing the foamed pellets to obtain the molded body. A molded body obtained or obtainable by the process is useful in furniture, seating, cushioning, car wheels or parts of car wheels, toys, animal toys, tires or parts of a tire, saddles, balls and sports equipment, sports mats, or as floor covering or wall paneling, especially for sports surfaces, track and field surfaces, sports halls, children's playgrounds, and pathways.

Claims

1-20. (canceled)

21: A molded body, comprising: foamed pellets comprising a composition (M1) comprising a thermoplastic elastomer (TPE-1) having a ratio of an average surface area to an average volume of the foamed pellets (A/V) in a range of from 1.4 to 3.0, wherein the volume V and the surface A are calculated according to equation 1 and 2: $\begin{array}{cc}A\approx 4{n^{*}\left(\left({\left(a^{*}b\right)}^{1.6075}+{\left(a^{*}c\right)}^{1.6075}+{\left(b^{*}c\right)}^{1.6075}\right)/3\right)}^{1/1.6075},& \left(1\right)\end{array}$ $\begin{array}{cc}V=4/4^{*}{n}^{*}{a}^{*}{b}^{*}c,& \left(2\right)\end{array}$ wherein n=π=3.141592653589793, with a=Flength and b=c=FThickness, wherein a, b, and c are determined in mm.

22: The molded body according to claim 21, wherein an average length of the foamed pellets is in a range of from 1 to 8 mm.

23: The molded body according to claim 21, wherein a ratio of an average length of the foamed pellets to an average width of the foamed pellets is in a range of from 1.0 to 2.0.

24: The molded body according to claim 21, wherein the thermoplastic elastomer (TPE-1) has a soft phase with a glass transition temperature T.sub.g of <10° C. determined by dynamic mechanical thermal analysis determined by loss factor (tan δ) according to DIN EN ISO 6721-2011-08 at a heating rate of 2 K/min at a frequency of 1 Hz.

25: The molded body according to claim 21, wherein the composition (M1) has a G′ modulus of a compact material at room temperature in a range of from 10 to 90 MPa, determined using DMA of a tempered body (20 h/100° C.) according to DIN EN ISO 6721-1-7:2018-03 with a heating program of 2 K/min at a frequency of 1 Hz.

26: The molded body according to claim 21, wherein the thermoplastic elastomer (TPE-1) is selected from the group consisting of thermoplastic polyurethane, thermoplastic polyamide, thermoplastic polyetherester, thermoplastic polyesterester, thermoplastic vulcanizate, thermoplastic polyolefin, thermoplastic styrenic elastomer, and a mixture thereof.

27: The molded body according to claim 21, wherein the composition (M1) comprises a filler in an amount in a range of from 0.1 to 20 wt.-%, based on a weight of the composition (M1).

28: The molded body according to claim 21, wherein the molded body consists of the foamed pellets.

29: A process for preparing a molded body, comprising: (i) providing foamed pellets comprising a composition (M1) comprising a thermoplastic elastomer (TPE-1) having a ratio of an average surface area to an average volume of the foamed pellets (A/V) in a range of from 1.4 to 3.0, and (ii) fusing the foamed pellets to obtain the molded body, wherein the volume V and the surface A are calculated according to equation 1 and 2: $\begin{array}{cc}A\approx 4{n^{*}\left(\left({\left(a^{*}b\right)}^{1.6075}+{\left(a^{*}c\right)}^{1.6075}+{\left(b^{*}c\right)}^{1.6075}\right)/3\right)}^{1/1.6075},& \left(1\right)\end{array}$ $\begin{array}{cc}V=4/4^{*}{n}^{*}{a}^{*}{b}^{*}c,& \left(2\right)\end{array}$ wherein n=π=3.141592653589793, with a=Flength and b=c=FThickness, wherein a, b, and c are determined in mm.

30: The process according to claim 29, wherein an average length of the foamed pellets is in a range of from 1 to 8 mm.

31: The process according to claim 29, wherein a ratio of an average length of the foamed pellets to an average width of the foamed pellets is in a range of from 1.0 to 2.0.

32: The process according to claim 29, wherein the thermoplastic elastomer (TPE-1) has a soft phase with a glass transition temperature T.sub.g of <10° C., determined by dynamic mechanical thermal analysis determined by loss factor (tan δ) according to DIN EN ISO 6721-2011-08 at a heating rate of 2 K/min at a frequency of 1 Hz.

33: The process according to claim 29, wherein the composition (M1) has a G′ modulus of a compact material at room temperature in a range of from 10 to 90 MPa, determined using DMA of a tempered body (20 h/100° C.) according to DIN EN ISO 6721-1-7:2018-03 with a heating program of 2 K/min at a frequency of 1 Hz.

34: The process according to claim 29, wherein the thermoplastic elastomer (TPE-1) is selected from the group consisting of thermoplastic polyurethane, thermoplastic polyamide, thermoplastic polyetherester, thermoplastic polyesterester, thermoplastic vulcanizate, thermoplastic polyolefin, thermoplastic styrenic elastomer, and a mixture thereof.

35: The process according to claim 34, wherein the thermoplastic elastomer (TPE-1) is selected from the group consisting of thermoplastic polyurethane, thermoplastic polyamide, thermoplastic polyetherester, thermoplastic polyesterester, and a mixture thereof.

36: The process according to claim 35, wherein the thermoplastic elastomer (TPE-1) is a thermoplastic polyurethane.

37: The process according to claim 29, wherein the composition (M1) comprises a filler in an amount in a range of from 0.1 to 20 wt.-%, based on a weight of the composition (M1).

38: The process according to claim 29, wherein (ii) is carried out by thermal fusing.

39: A molded body, obtained or obtainable by the process according to claim 29.

40: An article, comprising the molded body according to claim 39, wherein the article is selected from the group consisting of furniture, seating, cushioning, a car wheel, a part of a car wheel, a toy, an animal toy, a tire, a part of a tire, a saddle, a ball, sports equipment, a floor covering, and wall paneling.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0167] FIG. 1: gives a schematic overview over the measurement principle of the PartAn 3D.

[0168] FIG. 2: depicts a schematic particle showing the definition of the width (a) and length (b) of one particle

[0169] FIG. 3: depicts a schematic view of a spheroid, i.e. an ellipsoids with two equal semidiameters.

[0170] The present invention is further illustrated by the following reference examples, comparative examples, and examples.

EXAMPLES

[0171] I. Preparation

[0172] 1. TPU Synthesis [0173] The synthesis of the TPU precursor was carried out using a 48D (12 zones) twin-screw-extruder (ZSK58 MC, co. Coperion). The temperature of the extruder housing/zones was between 150 to 230° C. and a screw-speed of 180 to 240 1/min at a through-put of 180 220 kg/h. In the first zone the polyol, chain extender, catalyst and diisocyanate was added. Further additives were added in zone 8. The formulation is listed in table 1. [0174] After a gear pump and a melt filter the polymer melt at 180-210° C. was granulated using an underwater granulation. The granulate was subsequently dried using a heating fluidized bed (40-90° C.).

TABLE-US-00001 TABLE 1 Formulation of the used precursor. Ingredients TPU 1 Polyether based polyol having an OH-number of 112.2 and 1000 primary OH groups (based on tetramethylene oxide, functionality: 2) [parts] aromatic Isocyanate (4,4′-methylene diphenyl 500 diisocyanate) [parts] 1,4-butanediol [parts] 89.9 Stabilizer [parts] 25 Tin II isooctoate (50% in dioctyl adipate) [parts] 50 ppm

[0175] 2. eTPU Preparation [0176] The manufacturing of E-TPU was carried out on a twin screw extruder (Berstorff ZE 40) having a screw diameter of 44 mm and a L/D of 48, followed by a melt pump, a starting valve with screen changer, a die plate and an underwater pelletizer. The TPU was predried according to the processing guide at 80° C. for 3 hours for a residual humidity lower than 0.02 wt. %. For the materials, a Polystyrene resin (PS) was used. The content in wt. % of the total throughput was adapted according to table 2. [0177] The materials (TPU 1 and PS) were dosed separately by gravimetric dosing units into the main feed of the twin screw extruder. Furthermore, beside these components a further thermoplastic polyurethane (Modified TPU) was dosed at 0.6 wt. % into the extruder. This modified TPU consists of a TPU which is compounded in a separate extrusion process with 4,4′-Diphenylmethandiisocianate with an average functionality of 2.05. [0178] After the dosing, the material was molten and mixed in the extruder and afterwards a mixture of CO 2 and N.sub.2 was added as blowing agents. In the remaining extruder barrels, the polymer and the blowing agents were mixed into a homogenous mixture. The mixture is pressed by a melt pump to a starting valve including screen changer and finally through a die plate into the water box of an underwater pelletizing system. There the mixture is cut to granulates, and foamed in the pressurized, tempered water system. The water flow transports the beads to a centrifuge dryer where they are separated from the water stream. The total throughput was set to 40 kg/h (including polymers, blowing agents). [0179] In the following table 2, the individual settings and material compositions can be seen.

TABLE-US-00002 TABLE 2 Temperature profile of machine parts Temperature Temperature Pressure Temperature GPPS Temperature staring die underwater underwater eTPU TPU content extruder valve plate pelletizer pelletizer pellets used (wt. %) (° C.) (° C.) (° C.) (bar) (° C.) Ex. 1 TPU 1 7.5 170-220 175 220 15 55 Ex. 2 TPU 1 12.5 190-220 185 220 15 55 Comp. TPU 1 7.5 170-220 155 220 15 40 ex. 1 Comp. TPU 1 12.5 170-220 155 220 15 40 ex. 2 [0180] The blowing agent compositions of CO.sub.2 and N.sub.2 that were used are listed in the following table 3. The amounts of the blowing agents are calculated on the total throughput of polymers.

TABLE-US-00003 TABLE 3 Blowing agent compositions for foaming eTPU pellets CO2 [Gew. %] N2 [Gew. %] Example 1 2.3 0.1 Example 2 2.3 0.1 Comp. exa. 1 2.15 0.1 Comp. exa. 2 2.3 0.1 [0181] The resulting bulk density of the expanded beads can be found in table 4.

TABLE-US-00004 TABLE 4 Resulting Bulk Density eTPU pellets Bulk density (g/l) Example 1 124 ± 6 Example 2 119 ± 5 Comp. exa. 1 122 ± 6 Comp. exa. 2 128 ± 7 [0182] The E-TPU's used as examples and comparative examples are characterized in table 5. The average length and the average surface area to average volume ration are determined as explained in method example 1 and 2.

TABLE-US-00005 TABLE 4 Average Length and Average surface area/average volume ration of the E-TPU's used as examples and comparative examples Particle Average surface eTPU mass Average area/average pellets [mg] Length volume Example 1 4 3.8 2.1 Example 2 4 3.8 2.0 Comp. exa. 1 32 8.0 1.1 Comp. exa. 2 32 7.7 1.2 [0183] The foamed pellets (Examples 1 and 2 and comparative example 1 and 2) are molded on a steam chest molder type Boost Energy Foamer K68 from company Kurtz ersa GmbH to quadratic plates (example plates 1-2 and comparative example plates 1-2) with the dimension of 200*200*10 mm and 200*200*20 mm (dimensions could vary slightly due to shrinkage). Molding conditions are presented in table 6. [0184] By comparing example plate 1 with comparative example plate 1 and example plate 2 with comparative example plate 2, which were all molded with the same steaming conditions, it can be shown that by decreasing the average surface area to average volume ratio for foamed beads made from the same TPU, higher tensile strength can be reached at comparable rebound and compression hardness. This enables to mold beads with lower average surface area to average volume ratio with less intensive steaming conditions, which allows to produce parts with higher compression hardness at comparable tensile strength and rebound (compare example plate 1 to 3) (table 7). Tensile strength, compression hardness and rebound are determined as explained in method example 3 to 5.

TABLE-US-00006 TABLE 6 Steaming conditions during steam chest molding (Besides crack size and cooling time 10 and 20 mm test plates are molded under the same conditions; * Cooling time is set to the same values on static and movable side) Example Example Comp. exp Comp. exp Molded plate plate 1 plate 2 plate1 plate2 E-TPU Example 1 Example 2 Comp. exp 1 Comp. exp 2 Crack size - 10/20 10/20 10/20 10/20 10/20 mm mm mm mm mm plate (mm) Crack steam — — — — static side (bar) Crack steam — — — — static side (s) Crack steam — — — — movable side (bar Crack steam — — — — movable side (s) Cross steam 1.2 1.2 1.2 1.2 static side (bar) Cross steam 7 7 7 7 static side (s) Cross steam 1.2 1.2 1.2 1.2 movable side (bar) Cross steam 5 5 5 5 movable side (s) Autoclave  1.3/1.45  1.3/1.45  1.3/1.45  1.3/1.45 steam static/ movable side (bar) Autoclave 40 40 40 40 steam (s) Cooling time* - 100/120 100/120 100/120 100/120 10/20 mm plate

TABLE-US-00007 TABLE 7 Density and mechanical properties of the molded parts produced from the examples and comparative examples Compresssion Compresssion Density 10 Density 20 Tensile hardness hardness mm plate mm plate strength Rebound (10%) (50%) Molded plates (g/L) (g/L) (MPa) (%) (kPa) (kPa) Example 257 262 1.56 60 73 423 plate 1 Example 274 272 1.55 57 128 541 plate 2 Comp. exp 267 267 1.25 62 74 434 plate1 Comp. exp 284 284 1.36 59 103 558 plate 2

II. Method Examples

1. Method Example 1: Average Particle Diameter (Length) and Width

[0185] a. Free Particles [0186] The average particle length (defined here as diameter) and width of the free particles are received from particle size distribution measured with PartAn3D form Company Microtrac MRB. [0187] The PartAn 3D uses an image evaluation according to an ISO 13322-2 to determine shape and size parameters for particles. The schematic structure of the device is shown in Fehler! Verweisquelle konnte nicht gefunden werden. [0188] The measurement sequence for one sample of particles is as follows. 1 L of beads (for example 1 corresponding to a number of around 5,000 particles) are filled into a funnel (1) mounted over a vibrating channel (2). When the measurement stars the funnel is moving upwards and the vibration channel regulates the conveyance of the particles towards the camera. The camera is entrapped in a box (3) which has hole on the top. After reaching the end of the vibration channel the beads fall into the hole. On their way to the bottom the particles fell through the camera's field of view and several pictures are taken. As the particles rotate on their way down, pictures from different orientations are taken, what provides 3D information. Vibration channel and funnel movement are regulated so that the image area is obscured to 0.8% by the shadow of the particles falling from above (Further settings are listed in table 8). The camera is a 5 MP high-speed camera that captures at about 120 fps. Thus, an average of 8 images can be picked up from one falling particle. The corresponding evaluation software maps the individual images to each other and thus determines a data set for a measured particle from several images. [0189] The size parameters for one particle are determined as an image analysis of all available images of this specific particle. Length and width are determined by applying parallel tangents to the outer edge of the particle on the respective image. The Length is defined as the largest, the width as the shortest possible distance between two parallel tangents (Fehler! Verweisquelle konnte nicht gefunden werden.). To receive one value for length, width and thickness for one particle the parameter Flength, Fwidth and FThickness are taken from the software. They are defined as follows: Flength: Largest value of all length values determined from all single pictures for the specific bead; Fwidth Largest value of all width values determined from all single pictures for the specific bead; FThickness: Smallest value of all width values determined from all single pictures for the specific bead. To get average values for one sample of particles the median of all Flength, Fwidth and FThickness values are taken.

TABLE-US-00008 TABLE 5 PartAn 3D settings for measuring the particle size distribution of E-TPU Parameter Unit Dosing control Start Startup area % 0 Startup timeout s 300 Stop measurement — Area 0.03 Vibration control Gain — 444 Time — 422 Delay — 0 Max — 25 Min — 10 Threshold level % 25.9

[0190] b. Particles in the Molded Body: [0191] The average particle length (defined here as diameter) and width of the foamed pellets in the molded body are received from particle size distribution measured with computer tomocraphy (CT-scan) using standard parameters. [0192] The average diameter is determined by measurement of at least 20 different particles in the cross section of a molded part in two perpendicular directions.

2. Method Example 2: Average Particle Surface and Volume

[0193] Average particle surface and volume are calculated by assuming that the particles are spheroids (ellipsoids with two equal semi-diameters (Fehler! Verweisquelle konnte nicht gefunden werden.). For calculation equation 1 and 2 were used. Based on this, the volume V and the surface A are calculated according to equation 1 and 2.

[00001]$\begin{array}{cc}A\approx 4{n^{*}\left(\left({\left(a^{*}b\right)}^{1.6075}+{\left(a^{*}c\right)}^{1.6075}+{\left(b^{*}c\right)}^{1.6075}\right)/3\right)}^{1/1.6075}& \left(1\right)\end{array}$$\begin{array}{cc}V=4/4^{*}{n}^{*}{a}^{*}{b}^{*}c& \left(2\right)\end{array}$$n=\Pi =3.141592653589793$ [0194] with a=Flength and b=c=FThickness [0195] In the context of the present invention, the ratio of the average surface area to the average volume of the pellets (A/V) determined according to method-example 1 and 2 in a range of from 1.4 to 3.0 based on the absolute values of the average surface area to the average volume of the pellets unless noted otherwise. [0196] Unless otherwise noted, a, b, and c are determined in mm in the context of the present invention and the volume V and the surface A are calculated on the respective values unless noted otherwise in the context of the present invention.

3. Method Example 3: Tensile Strength

[0197] Tensile strength and elongation at break are measured with a universal testing machine, which is equipped with a 2.5 kN force sensor (class 0.5 (ab 10N), DIN EN ISO 7500-1, 2018), a long-stroke-extensometer (class 1 after DIN EN ISO 9513, 2013) and pneumatic clamps (6 bar, clamping jaws out of pyramid grid (Zwick T600 R)). [0198] The specimens (150 mm×25.4 mm×thickness of the test plate) are culled from a 200×200×10 mm test plate (dimensions could vary slightly due to shrinkage) with a cutting die. Before, the test plates were stored for at least 16 h under standardized climate conditions (23±2° C. and 50±5% humidity). The measurement is also carried out in standard climate. For each specimen density is determined. Therefore, mass (precision scale; accuracy: ±0,001 g) and thickness (caliper; accuracy: ±0.01 mm, contact pressure 100 Pa, value is only measured once in the middle of the specimen) are measured. Length (150 mm) and width (25.4 mm) are known from the dimension of the cutting die. [0199] The L.sub.E-position (75 mm) and the distance of the long-stroke-extensometer d (50 mm) are checked before stating the measurement. The specimen is placed on the upper clamp and the force is tared. Then the specimen is clamped and measurement could be started. The measurement is carried out with a testing speed of 100 mm/min and a force of 1 N. The calculation of tensile strength α.sub.max (specified in MPa) is done by equation (3), which is the maximum tension. This tension can be identical to the tension at breakage. Elongation at break (specified in %) is calculated using equation (4). Three specimens are tested for each material. The mean value from the three measurements is given. If the test specimen tears outside the selected area, this is noted. A repetition with another test specimen is not performed

[00002]$\begin{array}{cc}{\sigma }_{\max }=\frac{F_{\max }}{d.Math.b}& \left(3\right)\end{array}$ [0200] F.sub.max=Maximum tention [N] [0201] d=Thickness of the specimen [mm] [0202] b=Width of the specimen [mm]

[00003]$\begin{array}{cc}\epsilon =\frac{L_B-L_0}{L_0}.Math.100\%& \left(4\right)\end{array}$ [0203] L.sub.B=Length at breakage [mm] [0204] L.sub.0=Length before starting measurement [mm]

4. Method Example 4: Compression Hardness

[0205] For determination of the compression behaviour of the molded plates three specimens with the dimensions 50 mm*50 mm*original thickness of the plate (in general 20 mm but thickness can vary slightly due to shrinkage, skin is not removed) are taken from the plate by a band saw. [0206] For each specimen the mass (precision scale; accuracy: ±0.001 g) and the length and thickness (calliper; accuracy: ±0.01 mm, contact pressure 100 Pa, value is only measured once in the middle of the specimen) are measured. [0207] Compression behaviour is then measured with a 50 kN force transducer (class 1 according to DIN EN ISO 7500-1:2018-06), a crosshead travel encoder (class 1 according to DIN EN ISO 9513:2013) and two parallel pressure plates (Diameter 2000 mm, max. permissible force 250 kN, max. permissible surface pressure 300 N/mm 2) without holes. For determining the density of the specimen, the measured mass, length and thickness values are entered into the test specifications of the software of the test machine from company Zwick. The thickness of the specimen is determined by the universal test machine via the traverse path measuring system (accuracy: ±0.25 mm). The measurement itself is carried out with a test speed of 50 mm/min and a pre-force of 1 N. The force in kPa is recorded at a stint of 10 and 50 and. The values of the 1st cycle are used for evaluation. The sample during the measurement is compressed to 76%. [0208] Measurement is conducted from 3 specimens taken from one plate. As result the average from all three measurements is taken.

5. Method Example 5: Rebound

[0209] Within the context of the present invention, unless otherwise stated, the rebound is determined analogously to DIN 53512, April 2000; the deviation from the standard is the test specimen height which should be 12 mm, but in this test 20 mm is used in order to avoid “penetration through” the sample and measurement of the substrate.

CITED LITERATURE

[0210] Ullmann's “Encyclopedia of Technical Chemistry”, 4th edition, volume 20, p. 416 ff [0211] WO 94/20568A1 [0212] WO 2007/082838 A1 [0213] WO2017/030835 A1 [0214] WO 2013/153190 A1 [0215] WO2010/010010 A1 [0216] WO 2019/185687 A1 [0217] WO2017/039451 A1 [0218] WO2018/004344 A1 [0219] Plastics Additives Handbook, 5th edn., H. Zweifel, ed., Hanser Publishers, Munich, 2001 ([1]), pp. 98-136 [0220] Kunststoff-Handbuch Band 4, “Polystyrol” [Plastics handbook, vol. 4, “Polystyrene”], by Becker/Braun (1996)