TPU shrink material

Abstract

The present invention relates to a method for producing a molded body (MB) comprising the production of a thermoplastic polyurethane, the production of a molded body (MB*) from the thermoplastic polyurethane, heating the molded body (MB*) to a temperature below the temperature at which there is permanent deformability of the molded body (MB*), and above the switching temperature of the thermoplastic polyurethanes, elongating the heated molded body (MB*) with obtention of a molded body (MB), and cooling the molded body (MB) to a temperature below the switching temperature of the thermoplastic polyurethane, and the molded body obtained or obtainable by such a method. The present invention further relates to a thermoplastic polyurethane with shape memory and the use of a thermoplastic polyurethane for producing a molded body with shape memory effect in a temperature range from 0 C. to 130 C.

Claims

1. A method for producing a molded body MB, the method comprising: (a) producing a thermoplastic polyurethane by reacting (i) at least one polyisocyanate composition, (ii) at least one chain extender, and (iii) at least one polyol composition, wherein the polyol composition comprises at least one polyol P1 which contains at least one aromatic polyester block B1, wherein the aromatic polyester block B1 is a polyethylene terephthalate block; (b) producing a molded body MB* from the thermoplastic polyurethane, (c) heating the molded body MB* to a temperature below a temperature at which there is permanent deformability of the molded body MB* and above a switching temperature of the thermoplastic polyurethanes, to obtain a heated molded body MB*, (d) elongating the heated molded body MB* to obtain the molded body MB, and (e) cooling the molded body MB to a temperature below the switching temperature of the thermoplastic polyurethane, wherein a start of the permanent deformability corresponds to a start of melting of a hard phase of the thermoplastic polyurethane, and the switching temperature corresponds to a start of phase transition lying highest in the temperature before the melting range.

2. The method of claim 1, wherein the thermoplastic polyurethane is a compact thermoplastic polyurethane.

3. The method of claim 1, wherein the switching temperature of the thermoplastic polyurethane lies in a range from 0 to 130 C.

4. The method of claim 1, wherein the elongation of the molded body MB in (d) in at least one dimension is at least 150% of the elongation of the molded body MB*.

5. The method of claim 1, wherein the molded body MB* in (b) is produced by extrusion, injection molding, a sinter method, or from solution.

6. The method of claim 1, wherein the chain extender used in (a) is a diol with a molecular weight Mw<220 g/mol.

7. The method of claim 1, wherein the chain extender used in (a) and the polyol P1 contained in the polyol composition are used in a molar ratio from 40 to 1 to 1 to 10.

8. The method of claim 1, wherein the polyol composition comprises a further polyol selected from the group consisting of a polyetherol, a polyesterol, a polycarbonate alcohol, and a hybrid polyol.

9. The method of claim 1, wherein the polyisocyanate composition is an aromatic diisocyanate.

10. The method of claim 1, wherein the molded body MB through heating to a temperature above the switching temperature undergoes a recovery.

11. The method of claim 10, wherein the molded body MB through heating to a temperature above the switching temperature undergoes a recovery by at least 20%.

12. A molded body, obtained by the method of claim 1.

13. The molded body of claim 12, which is a tube or a film.

14. A thermoplastic polyurethane, obtained by a method comprising: reacting at least components (i) to (iii): (i) a polyisocyanate composition, (ii) at least one chain extender, and (iii) at least one polyol composition, wherein the polyol composition comprises at least one polyol P1 which contains at least one aromatic polyester block B1, wherein the aromatic polyester block B1 is a polyethylene terephthalate block, wherein the polyol P1 has a molecular weight Mn ranging from 500 to 2500 g/mol and is based on polybutylene terephthalate or polyethylene terephthalate, wherein the polyol P1 contains 1 to 70 wt. % of the aromatic polyester blocks B1, wherein the chain extender is a diol with a molecular weight Mw<220 g/mol, and wherein the polyisocyanate composition is an aromatic diisocyanate.

15. The molded body of claim 12, which has shape memory effect in a temperature range from 0 C. to 130 C.

16. The molded body of claim 12, which is a shrink tube or a shrink film.

Description

EXAMPLES

1 The Following Starting Materials were Used

(1) Polyol 1: Polyester polyol based on adipic acid, 1,4-butanediol and monoethylene glycol with MW 2000 g/mol and an OH number of 56, functionality: 2 Polyol 2: Polyether polyol based on tetramethylene oxide with an OH number of 113.9 and exclusively primary OH groups, functionality: 2 Polyol 3: Polyester polyol based on adipic acid, succinic acid, glutaric acid, PET and diethylene glycol and an OH number of 75.6 and functionality: 2 Polyol 4: Polyester polyol based on adipic acid, succinic acid, glutaric acid, PET and diethylene glycol and an OH number of 110.6 and functionality: 2 Polyol 5: Polyester polyol based on adipic acid, PET and diethylene glycol, and an OH number of 113.8 and functionality: 2 Isocyanate 1: aromatic isocyanate (4,4 methylenediphenyl diisocyanate) CE: 1,4-butanediol Catalyst 1: tin-II isooctoate (50% in dioctyl adipate) Stabilizer 1: hydrolysis stabilizer based on carbodiimides Stabilizer 2: sterically hindered phenol

2 Synthesis of the Polyester Polyols with PET Blocks

(2) 2.1 Synthesis of Polyol 3

(3) Firstly 1040.9 g of dicarboxylic acid mixture (consisting of adipic acid, glutaric acid and succinic acid) and 1016.2 g of diethylene glycol are added to a 3000 ml round-necked flask equipped with thermometer, nitrogen inlet, stirrer and heating mantle. The mixture is then heated at 120 C. until a homogeneous mixture is formed. 750 g of polyethylene terephthalate (PET) are now added to the mixture. The reaction mixture is heated further at 240 C. and the water of reaction formed continuously removed. During the whole synthesis, the PET flakes are slowly decomposed and a transparent mixture is formed, which is condensed until a product with an acid number <1.0 mg KOH/g is obtained.

(4) The polymer obtained has the following properties Hydroxyl number: 75.6 mg KOH/g Acid number: 0.7 mg KOH/g Viscosity at 75 C.: 840 mPas
2.2 Synthesis of Polyol 4

(5) Firstly 819.5 g of dicarboxylic acid mixture (consisting of adipic acid, glutaric acid and succinic acid) and 925.9 g of diethylene glycol are added to a 3000 ml round-necked flask equipped with thermometer, nitrogen inlet, stirrer and heating mantle. The mixture is then heated at 120 C. until a homogeneous mixture is formed. 1000 g of polyethylene terephthalate (PET) are now added to the mixture. The reaction mixture is further heated at 240 C. and the water of reaction formed continuously removed. During the whole synthesis the PET flakes are slowly decomposed and a transparent mixture is formed, which is condensed until a product with an acid number <1.0 mg KOH/g is obtained.

(6) The polymer obtained has the following properties Hydroxyl number: 110.6 mg KOH/g Acid number: 0.6 mg KOH/g Viscosity at 75 C.: 660 mPas
2.3 Synthesis of Polyol 5

(7) Firstly 1008.4 g of adipic acid and 1020.0 g of diethylene glycol are added to a 3000 ml round-necked flask equipped with thermometer, nitrogen inlet, stirrer and heating mantle. The mixture is then heated at 120 C. until a homogenous mixture is formed. 750 g of PET are now added to the mixture. The reaction is further heated at 240 C. and the water of reaction formed continuously removed. During the whole synthesis the PET flakes are slowly decomposed and a transparent mixture is formed, which is condensed until a product with an acid number <1.0 mg KOH/g is obtained.

(8) The polymer obtained has the following properties Hydroxyl number: 113.8 mg KOH/g Acid number: 0.4 mg KOH/g Viscosity at 75 C.: 381 mPas

3 Methods

(9) 3.1 Viscosity Determination:

(10) Unless otherwise stated, the viscosity of the polyols was determined at 75 C. according to DIN EN ISO 3219 (Issue Jan. 10, 1994) with a rotational viscometer Rheotec RC 20 using the spindle CC 25 DIN (spindle diameter: 12.5 mm; measuring cylinder internal diameter: 13.56 mm) at a shear rate of 50 1/s.

(11) 3.2 Measurement of the Hydroxyl Number:

(12) The hydroxyl numbers were determined by the phthalic anhydride method DIN 53240 (Issue: Jan. 12, 1971) and stated in mg KOH/g.

(13) 3.3 Measurement of the Acid Number:

(14) The acid number was determined according to DIN EN 1241 (Issue: Jan. 5, 1998) and is stated in mg KOH/g.

4 General Production Example

(15) The polyols were placed at 80 C. in a vessel and mixed with the components according to table 1 with vigorous stirring. The reaction mixture heated itself to over 110 C. and was then poured out onto a heated, Teflon-coated bench. The cast slab obtained was heated for 15 hours at 80 C., then granulated and processed by injection molding.

(16) TABLE-US-00001 TABLE 1 Compounds Used Comparison 1 Example 1 Example 2 Example 3 Comparison 2 Example 4 Polyol 1 [g] 800.0 Polyol 2 [g] 800.0 160.0 Polyol 3 [g] 800.0 Polyol 4 [g] 800.0 640.0 Polyol 5 [g] 800.0 CE [g] 100.9 104.7 111.7 112.3 108.3 107.8 Isocyanate 1 [g] 384.0 428.7 510.5 518.0 504.0 497.9 Stabilizer 1 [g] 6.4 6.4 6.4 6.4 Stabilizer 2 [g] 14.2 14.2 Index 1000 1000 1000 1000 1000 1000 Hard segment 29.7% 29.7% 29.7% 29.7% 29.0% 29.0% content Start temperature 80 C. 80 C. 80 C. 80 C. 80 C. 80 C. Casting temperature 110 C. 110 C. 110 C. 110 C. 110 C. 110 C.

5 Mechanical Properties

(17) The measured values compiled in table 2 were obtained from injection molded plates or from extrusion products of example 1 and 2.

(18) TABLE-US-00002 TABLE 2 Mechanical properties for examples 1 and 2 Example 1 Example 2 Shore D 52 77 Tensile strength 46 Mpa 42 Mpa Elongation at break 580% 500% Tear growth resistance 120 kN/m 237 kN/m Abrasion 48 mm.sup.3 43 mm.sup.3

(19) The following properties of the polyurethanes obtained were determined by said methods:

(20) Hardness: DIN ISO 7619-1

(21) Tensile strength and elongation at break: DIN 53504

(22) Tear growth resistance: DIN ISO 34-1, B (b)

(23) Abrasion measurement: DIN ISO 4649

6 Determination of the Shrinkage Behavior

(24) Ca. 1.5 cm wide and 9.3 cm long strips are cut out from injection molding plates (MB*) and heated for 30 mins at 120 C. in the heating oven. Next, the strips are elongated by means of two grippers and cooled under running cold water. After this, the molded body MB is again placed into the heating oven at 120 C. and the nature of the recovery behavior observed.

(25) For various samples, the shrinkage behavior was determined according to the general determination method. The results are summarized in Table 3.

(26) TABLE-US-00003 TABLE 3 Observation in Length after Stretching hot water after Shrinkage Sample pulling (MB) to shrinkage by Comparison 1 10 cm 107% shrinks to 9.7 cm 3% Example 1 16 cm 172% shrinks to 9.6 cm 40% Example 2 15.5 cm 167% shrinks to 9.5 cm 39% Example 3 14.2 cm 153% shrinks to 9.5 cm 33% Comparison 2 9.8 cm 105% shrinks to 9.6 cm 2% Example 4 17 cm 183% shrinks to 9.5 cm 44%

LITERATURE CITED

(27) JP 2005102953 WO 2011/060970 A1 US 2012/0279101 A1 WO 2015/144435 A1 U.S. Pat. No. 7,524,914 B2 Kunststoffhandbuch, Band 7, Polyurethane, Carl Hanser Verlag, 3. Auflage, 1993, Kapitel 3.1 and S. 103-113