THERMOPLASTIC ELASTOMERIC COMPOSITIONS COMPRISING POLYOLEFINS AND STYRENE-B-ETHYLENE- ETHYLENE-PROPYLENE-B-STYRENE BLOCK COPOLYMERS

Abstract

The present invention relates to thermoplastic elastomeric compositions comprising polyolefins, styrene-b-ethylene-ethylene-propylene-b-styrene block copolymers and optionally, a plasticizers, laminates comprising the same as well as their use in disposable hygiene and medical products.

Claims

1: A thermoplastic elastomer composition comprising a. a styrene-b-ethylene-ethylene-propylene-b-styrene block copolymer (SEEPS), b. a polyolefin elastomer, c. optionally, a plasticizer, and d. a polystyrene polymer.

2: The thermoplastic elastomer composition according to claim 1 wherein the polyolefin elastomer comprises propylene and ethylene units.

3: The thermoplastic elastomer composition according to claim 2 wherein the ethylene content in the polyolefin elastomer is higher than 15 wt %.

4: The thermoplastic elastomer composition according to claim 1 wherein the polyolefin elastomer has a melt index (190 C./2.16 kg) as measured according to ASTM D1238 of less than 9 g/10 min.

5: The thermoplastic elastomer composition according to claim 4 wherein the polyolefin elastomer has a melt index (190 C./2.16 kg) as measured according to ASTM D1238 of less than 5 g/10 min.

6: The thermoplastic elastomer composition according to claim 5 wherein the polyolefin elastomer has a melt index (190 C./2.16 kg) as measured according to ASTM D1238 of less than 2 g/10 min.

7: The thermoplastic elastomer composition according to claim 1 comprising 50 to 85 wt % of the polyolefin elastomer.

8: The thermoplastic elastomer composition according to claim 1 wherein the styrene-b-ethylene-ethylene-propylene-b-styrene block copolymer (SEEPS) is a tri block copolymer with from 28 to 32 wt % bound styrene hard block segments and a soft mid-block composed of hydrogenated butadiene and isoprene.

9: The thermoplastic elastomer composition according to claim 1 wherein the thermoplastic elastomer composition comprises less than 10 wt % of a hydrogenated block copolymer that is formed by hydrogenating a block copolymer having a polymer block (x) containing more than about 70% by mass of structural units derived from an aromatic vinyl compound (based on the total mass of polymer block (x)), and a polymer block (y) containing about 30% by mass or more of structural units derived from at least one kind selected from the group consisting of a conjugated diene compound and isobutylene (based on the total mass of polymer block (y)), and in the hydrogenated block copolymer, the total content of 3,4-bond units and 1,2-bond units in the polymer block (y) is 50 mol % or more.

10: The thermoplastic elastomer composition according to claim 1 comprising less than 7 wt % of one or more thermoplastic polymers selected from the list consisting of polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), polyamides (PA), polycarbonates (PC), polyethylene terephthalate (PET), polyethylene terephthalate copolymers (PETG), polyhydroxyalkanoates (PHA), thermoplastic elastomers (TPE), thermoplastic polyurethanes (TPU), (homo)polyethylenes (PE), (homo)polypropylenes (PP), ethylene vinyl alcohols (EVOH), acrylonitrile styrene acrylate (ASA), polyacrylates, polyterpenes, polyphenols and polymethacrylates wherein the 7 wt % is the combined amount of said thermoplastic polymers.

11: The thermoplastic elastomer composition according to claim 1 wherein the thermoplastic elastomer composition comprises no polypropylene homopolymers.

12: The thermoplastic elastomer composition according to claim 1 wherein the thermoplastic elastomer composition comprises 5 wt % or more and less than 7 wt % of one or more polypropylene homopolymers.

13: A film comprising the thermoplastic elastomer composition according to claim 1.

14: A laminate comprising the film according to claim 12 and a non-woven textile-like fabric based on polyamide (PA), polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), cotton or a mixture thereof.

15: A disposable hygiene or medical product comprising the film according to claim 13.

Description

EXAMPLES

Preparation of Pre-Mixes PM1 to PM4

[0038] Pre-mixtures for the film preparation were compounded on a co-rotating twin screw compounder available from Maris with a diameter of 58 mm, a Length-to-Diameter-ratio (LD) of 55, no screens. No melt pump was used. The materials were pre-blended on a highspeed batch type mixer, with app. 100 litter volume, in-line of the compounding feeder. The compounding temperature was controlled from 20 C. (inlet) to 190 C. (die), app. 500 rpm screw speed, underwater cutting, use of antiblocking agents.

[0039] Production of the Films

[0040] Films were produced on a cast film extrusion line with the following setup: 3-layer co-extrusion with the configuration A/B/A (see below in table 1), screw dimensions of extruder A: diameter 45 mm, length 1440 mm, B: diameter 28 mm, length 840 mm. Die with width of 600 mm, T-die type. Temperature settings: 205 C. (extruder), 225-235 C. (feedblock and die), 4 C. (chill roll) Pull-up: approximately 10 m/min (variable). The film thickness was set to 60 m and normalized to compare different recipes.

[0041] Evaluation

[0042] The elastic properties of the films were evaluated. The 2nd cycle load point at 100% strain determines the force necessary to stretch the diaper closing system. The 2nd cycle unload stress point at 50% determines the remaining stress after stretching. Both parameter are associated with the holding force of the diaper closing system and provides an indication of the stable wear and comfort during wear.

[0043] Table 1 shows the recipes and the elastic properties according to the description above. The tear resistance was evaluated according to Elmendorf tear resistance measurement and qualitatively summarized. The processibility on the cast extrusion line was qualitatively summarized, taking typical known process problems into account that is known to reduce the process stability (temperature window, gels, neck-in, melt fracture).

[0044] The results in table 1 show that replacing the known SEBS block co-polymers with the inventive SEEPS block co-polymers leads to a surprising improvement in elastic properties and/or processibility while keeping a good level of tear resistance.

TABLE-US-00001 TABLE 1 all % are wt % C1 E2 E3 E4 Layer A (both 100% PP.sup.1 100% PP.sup.1 100% PP.sup.1 100% PP.sup.1 outer layers, each 5 m) Layer B 60% POE.sup.2/ 60% POE.sup.2/ 60% POE.sup.2/ 60% POE.sup.2/ (middle 40% PM1 40% PM2 40% PM3 40% PM4 layer) 2nd Cycle 1.11 1.29 1.23 1.41 Load 2nd Cycle 0.26 0.32 0.41 0.32 Unload Tear Medium Medium Medium Medium Resistance Processibility Moderate Moderate Moderate Good .sup.1Polypropylene homopolymer, type 520P, manufacturer: Sabic .sup.2Polyolefin elastomer VISTAMAXX 6102, manufacturer: ExxonMobil

[0045] The pre-mixtures were produced on a twin-screw compounder according the above description. The composition is as follows: [0046] PM1: 74.5% SEBS (SEPTON 8004, manufacturer: Kuraray Co., Ltd.), 24.5% Processing Oil (Paraffinic, medical quality, type Oyster 261, manufacturer Petroyag), <1% Processing Aids (antioxidant, silica, talc) [0047] PM2: 74.5% SEEPS (SEPTON 4033, manufacturer: Kuraray Co., Ltd.), 24.5% Processing Oil (Paraffinic, medical quality, type Oyster 261, manufacturer Petroyag), <1% Processing Aids (antioxidant, silica, talc) [0048] PM3: 63.5% SEEPS (SEPTON 4033, manufacturer: Kuraray Co., Ltd.), 20.5% Processing Oil (Paraffinic, medical quality, type Oyster 261, manufacturer Petroyag), 15% polystyrene (GPPS, type PS3190, manufacturer: Styrolution), <1% Processing Aids (antioxidant, silica, talc) [0049] PM4: 63.5% SEEPS (SEPTON 4033, manufacturer: Kuraray Co., Ltd.), 20.5% Processing Oil (Paraffinic, medical quality, type Oyster 261, manufacturer Petroyag), 15% polypropylene (polypropylene homopolymer, type 520P, manufacturer: Sabic), <1% Processing Aids (antioxidant, silica, talc)