ANTISTATIC STRETCH FILM

Abstract

A stretchable antistatic film can be formed in a production process using a specific thermoplastic polyurethane. The thermoplastic polyurethane is useful for the production of said film.

Claims

1. A stretchable film, comprising: at least two layers, comprising a layer A and a layer B, each layer having an inner surface being in contact with the respective other layer, and an outer surface being opposite the inner surface, wherein layer A comprises a polymer 1 composition, and layer B comprises a thermoplastic polyurethane composition, and optionally a polymer 2 composition, wherein a polyurethane in the thermoplastic polyurethane composition is prepared from: an organic diisocyanate, a polyol comprising a diol A and a diol B, wherein the diol A comprises ethoxy and propoxy groups and the diol B comprises butoxy groups, and a chain extender: wherein the thermoplastic polyurethane composition comprises a salt, an ionic liquid, or a salt and an ionic liquid, and wherein the stretchable film has an elongation at break of more than 50% measured according to DIN ISO 53504, 2017-03.

2. The stretchable film according to claim 1, wherein the stretchable film has an elongation at break of more than 100%, measured according to DIN ISO 53504, 2017-03.

3. The stretchable film according to claim 1, wherein a polymer of the polymer 1 composition is selected from the group consisting of polystyrene (PS), polyoxymethylene (POM), ethylene-vinyl acetate (EVA), acrylonitrile-butadiene-styrene (ABS), thermoplastic polyurethane (TPU), polyvinylchloride (PVC), polyethylene (PE), polypropylene (PP), and a mixture thereof.

4. The stretchable film according to claim 1, wherein a polymer of the polymer 1 composition is a low-density polyethylene (LDPE), a linear low-density polyethylene (LLDPE), or a mixture thereof.

5. The stretchable film according to claim 1, further comprising an adhesive on an outer surface of the stretchable film.

6. The stretchable film according to claim 5, wherein the adhesive comprises ultra-low-density polyethylene (ULDPE).

7. The stretchable film according to claim 1, wherein the stretchable film has an electric resistance of less than 10.sup.12 Ohm measured according to DIN EN 62631-3-2:2018-09.

8. The stretchable film according to claim 1, wherein the layer B comprises the polymer 2 Composition, which comprises the thermoplastic polyurethane composition.

9. The stretchable film, according to claim 1, wherein a polymer of the polymer 2 composition is low-density polypropylene (LDPE).

10. The stretchable film according to claim 1, wherein the diol A is a block copolymer having a block and two ends, wherein the block comprises ethoxy and propoxy groups and the two ends of the block copolymer comprise exclusively ethoxy groups.

11. The stretchable film according to claim 1, wherein the ionic liquid comprises an imidazole ring.

12. A method, comprising: preparing the stretchable film according to claim 1 with the thermoplastic polyurethane composition, wherein the polyurethane in the thermoplastic polyurethane composition is prepared from: the organic diisocyanate, the polyol comprising the diol A and the diol B, wherein the diol A comprises ethoxy and propoxy groups and the diol B comprises butoxy groups, and the chain extender; wherein the thermoplastic polyurethane composition comprises the salt, the ionic liquid, or the salt and the ionic liquid.

13. A process for producing the stretchable film according to claim 1, comprising at least: producing the layer A, producing the layer B, combining at least layer A and layer B to form the stretchable film, and optionally, adding on at least one outer side of layer A or layer B, a layer C comprising an adhesive.

14. The process according to claim 13, wherein layer C is added on the outer side of layer A.

15. The stretchable film according to claim 2, wherein the stretchable film has an elongation at break of more than 300%, measured according to DIN ISO 53504, 2017-03.

16. The stretchable film according to claim 4, wherein the polymer of the polymer 1 composition is a mixture of low-density polyethylene and linear low-density polyethylene.

17. The stretchable film according to claim 5, wherein the adhesive is on the outer surface of layer A.

Description

EXAMPLES (EEE)

Example 1

Materials Used

[0127] LLDPE: A linear low-density polyethylene of typical extrusion quality with a density (determined according to DIN EN ISO 1183-1:2019, A) of 0.92 gcm.sup.−3, an MFR (determined according to DIN EN ISO 1133-1:2011) at 190° C. and 2.16 kg of 1.0 g/(10 min), and a Vicat temperature (determined according to DIN EN ISO 306:2013, A) of 102° C.

[0128] ULDPE: A ultra-low-density polyethylene of typical extrusion quality with a density (determined according to DIN EN ISO 1183-1:2019, A) of 0.90 gcm.sup.−3, an MFR (determined according to DIN EN ISO 1133-1:2011) at 190° C. and 2.16 kg of 3.0 g/(10 min), and a Vicat temperature (determined according to DIN EN ISO 306:2103, A) of 90° C.

[0129] LDPE: A low-density polyethylene of typical extrusion quality with a density (determined according to DIN EN ISO 1183-1:2019, A) of 0.92 gcm.sup.−3, an MFR (determined according to DIN EN ISO 1133-1:2011) at 190° C. and 2.16 kg of 1.0 g/(10 min), and a Vicat temperature (determined according to DIN EN ISO 306:2013, A) of 96° C.

[0130] Additive: A thermoplastic polyurethane based on HDI, a polyol mixture of polytetramethylene glycol (PTMG) with molecular weight between 500 g/mol and 2000 g/mol and polyol with ethoxy and propoxy groups with molecular weight between 1500 g/mol and 3000 g/mol, and 1,6-hexandiol, comprising about 3 wt-% 1-ethyl-3-methylimidazolium ion (EMIM).

Example 2

Manufacturing of a Two-Layer Film with ULDPE and LLDPE (Comparative Example)

[0131] To manufacture a two-layer film the required polymers ULDPE (Layer C in Tab. 1) and LLDPE (Layer A in Tab. 1) were fed into separate single-screw extruders, and molten at temperatures between 180 and 210° C. The melts were separately dosed in two concentric nozzles through additionally air was blown, keeping the tubes in form an allow them to lay on each other to build the tubular film with ULDPE layer (Layer C) on the inner side of about 0.003 mm and LLDPE layer (Layer A) of about 0,017 mm on the outer side. This tubular film was cut along its axis to become the film, which after accommodation for 3 days was used in the following measurements.

Example 3

Three-Layer Film

[0132] To manufacture an anti-static three-layer film, in the first step 85 wt-% of LDPE and 15 wt-% of the Additive were compounded with a twin-screw extruder at a temperature between 180° C. and 200° C. resulting in a Blend that is further used.

[0133] In a second step ULDPE (Layer C in Tab. 1), LLDPE (Layer A in Tab. 1), and the Blend produced in the first step (Layer B in Tab. 1), were fed into separate melting devices, e.g. single-screw extruders, and molten at a temperature between 180° C. and 210° C. The melt for each of the three respective layers was separately dosed in concentric ring nozzles. Additionally air was blown through these concentric nozzles keeping the tubes in form and allow them to lay on each other to build the tubular film with ULDPE layer (layer C) on the inner side of about 0.003 mm, the LLDPE layer (layer A) of about 0.017 mm in the middle and the blend layer (Layer B) with about 0.003 mm on the outside of the tube, This tubular film was cut along its axis to become the film, which, after accommodation for 3 days, was used in the following measurements.

Example 4

Measurements

[0134] The surface resistivity of the anti-static stretch film according to Example 2 and 3 were measured according to DIN 62631-3-2:2018-09 in unstretched state (at 0% elongation) and stretched state (200% elongation).

TABLE-US-00001 TABLE 1 Overview on films and their respective surface resistivities. No. Film 1* Film 2** Composition Layer C 100% ULDPE 100% ULDPE Layer A 100% LLDPE 100% LLDPE Layer B — 100% Blend Stretched No No Yes Surface resistance 20% rel. hum. 2.0*10.sup.15 1.7*10.sup.10 1.6*10.sup.10 [Ω] 50% rel. hum. 2.0*10.sup.15 7.0*10.sup.9  6.2*10.sup.9  (at 23° C.) 70% rel. hum. 1.9*10.sup.15 2.8*10.sup.9  2.7*10.sup.9  *Film prepared according to Example 2. **Film prepared according to Example 3.