THERMOPLASTIC FOAM PREPARED FROM TWO SPECIAL POLYURETHANE DISPERSIONS

Abstract

The invention relates to a foamed, fissure-free skin-compatible article, produced by mixing a first polyurethane dispersion (A) with at least one second polyurethane dispersion (B) which differs from the first polyurethane dispersion (A), optionally with the addition of other additives, then by foaming and subsequently drying the mixture. The invention also relates to a process for preparing the foamed article and to the use thereof.

Claims

1. A foamed article produced by mixing a first polyurethane dispersion (A) with at least one second polyurethane dispersion (B), optionally with addition of further additives, foaming and subsequently drying the mixture, wherein the polyurethane dispersion (A) is obtained by preparing A) isocyanate-functional prepolymers from A1) organic polyisocyanates, A2) polymeric polyols having number-average molecular weights of 400 to 8000 g/mol and OH functionalities of 1.5 to 6, and A3) optionally hydroxyl-functional compounds having molecular weights of 62 to 399 g/mol, and A4) optionally isocyanate-reactive, anionic or potentially anionic and optionally nonionic hydrophilizing agents, and B) the free NCO groups thereof are then wholly or partly reacted B1) optionally with amino-functional compounds having molecular weights of 32 to 400 g/mol and B2) with amino-functional, anionic or potentially anionic hydrophilizing agents by chain extension and the prepolymers are dispersed in water before, during or after step B), and wherein the second polyurethane dispersion (B) is obtained by reactive conversion of at least the following components: A. an aliphatic polyisocyanate component having an average isocyanate functionality of ≥1.8 and ≤2.6, B. a polymeric polyether polyol component, C. an amino-functional chain extender component having at least 2 isocyanate-reactive amino groups, comprising at least one amino-functional compound C1. that does not have any ionic or ionogenic groups and/or an amino-functional compound C2. that has ionic or ionogenic groups, D. optionally further hydrophilizing components other than C2., E. optionally hydroxyl-functional compounds having a molecular weight of 62 to 399 mol/g, F. optionally further polymeric polyols other than B., G. a compound having exactly one isocyanate-reactive group or a compound having more than one isocyanate-reactive group where only one of the isocyanate-reactive groups reacts with the isocyanate groups present in the reaction mixture under the reaction conditions chosen, and H. optionally an aliphatic polyisocyanate component having an average isocyanate functionality of >2.6 and ≤4, where components B. and F. together contain ≤30% by weight of component F., based on the total mass of components B. and F.

2. The foamed article as claimed in claim 1, wherein the foamed article has at least one of the following properties i. to xiii.: i. the foamed article has no cracks having a width of 2 mm; ii. the foamed article has no surface cracks deeper than 0.4 mm; iii. the foamed article has a crack area of 6%, based on the total area of the foamed article; iv. the foamed article has a cell viability of 70% or a classification of 0 to 2 in a cytotoxicity test based on DIN ISO 10993-5:2009-10; v. the foamed article has a density within a range from 80 to 500 g/l; vi. the foamed article has a thickness (D) within a range from 0.1 to 100 mm; vii. the foamed article has a tensile stress at break within a range from 100 to 1100 kPa measured according to DIN EN ISO 527-2:2012-06; viii. the foamed article has an elongation at break within a range from 100% to 500%, measured according to DIN EN ISO 527-2:2012-06; ix. the polyurethaneurea formed from the polyurethane dispersion (B) is amorphous and has a Tg ≤−25° C., determined by differential scanning calorimetry in accordance with DIN EN 61006, Method A; x. the foamed article has a melting or softening range of 180° C., at a maximum pressure of 4 bar and has full thermoplastic processability within this range; xi. the foamed article has an average pore size within a range from 200 to 750 μm; xii. the foamed article has an outer layer at least on one surface of the foamed article; xiii. the foamed article is part of a composite material.

3. The foamed article as claimed in claim 1, wherein the weight ratio of the polyurethane dispersion (A) to the polyurethane dispersion (B) is within a range from 1:1 to 5:1, based on the total mass of the masses of dispersions (A) and (B).

4. The foamed article as claimed in claim 1, wherein a film formed from the dispersion (B) has a tensile strain at break of ≤5 MPa combined with an elongation at break of 1750%.

5. The foamed article as claimed in claim 1, wherein the hydrophilizing agents B2) used are hydrophilizing agents containing sulfone groups.

6. The foamed article as claimed in claim 1, wherein the dispersion (A) has a solids content of polyurethane of 52% to 65% by weight, based on the total mass of the dispersion (A).

7. The foamed article as claimed in claim 1, wherein component A. or A1) is isophorone diisocyanate and/or hexamethylene diisocyanate.

8. The foamed article as claimed in claim 1, wherein component B. comprises or consists of poly(tetramethylene glycol) polyether polyols.

9. The foamed article as claimed in claim 1, wherein component B. comprises or consists of a mixture of at least two poly(tetramethylene glycol) polyether polyols, wherein the at least two poly(tetramethylene glycol) polyether polyols are of different number-average molecular weight.

10. The foamed article as claimed in claim 1, wherein component D. comprises nonionically hydrophilizing components.

11. The foamed article as claimed in claim 1, wherein component H. is used and the molar ratio of component G. to component H. is 5:1 to 1:5.

12. The foamed article as claimed in claim 1, wherein the polyurethane dispersion (B) is obtained by preparing isocyanate-functional polyurethane prepolymers a) from components A., B. and optionally D. and/or C2., and optionally compounds E. and/or H., and the free NCO groups thereof are then wholly or partly reacted with the amino-functional chain-extender component C., and also component G. and optionally components D. and H.

13. A process for producing a foamed article as claimed in claim 1, wherein the process comprises: (V1) mixing the polyurethane dispersion (A) and the polyurethane dispersion (B) to obtain a mixture (M1), (V2) optionally adding to (M1) at least one interface-active substance, (V3) optionally adding to (M1) at least one surfactant, (V4) optionally adding to (M1) a thickener, (V5) foaming the mixture (M1) to give a foam, (V6) optionally maturing the foam from step (V2), (V7) optionally applying the foam formed in step (V2) or (V3) to a substrate, (V8) drying the foam to form the foamed article.

14. A wound dressing, a hygiene article, or a wearable patch, comprising the foamed article as claimed in claim 1.

15. A kit of parts at least including a polyurethane dispersion (A) and a polyurethane dispersion (B), wherein the polyurethane dispersion (A) or the polyurethane dispersion (B) includes an added material (C), wherein the dispersion (A) or (B) including the added material (C) has a cell viability of 70% in a cytotoxicity test or a classification of 0 to 2 according to DIN ISO 10993-5:2009-10.

Description

EXAMPLE 1: PRODUCTION OF THE POLYURETHANE DISPERSION (A)

[0298] 1077.2 g of PolyTHF® 2000, 409.7 g of PolyTHF® 1000, 830.9 g of Desmophen® C2200 and 48.3 g of polyether LB 25 were heated to 70° C. in a standard stirring apparatus. Subsequently, at 70° C., a mixture of 258.7 g of hexamethylene diisocyanate and 341.9 g of isophorone diisocyanate was added over 5 min and the mixture was stirred at 120° C. until the NCO value had attained or fallen slightly below the theoretical NCO value. The finished prepolymer was dissolved with 4840 g of acetone and cooled to 50° C., before a solution of 27.4 g of ethylenediamine, 127.1 g of isophoronediamine, 67.3 g of diaminosulfonate and 1200 g of water was added over 10 min. The mixture was stirred for a further 10 min. This was followed by dispersion by addition of 654 g of water. This was followed by removal of the solvent by distillation under vacuum.

[0299] The resultant polyurethane dispersion had the following properties:

Solids content: 61.6%
Particle size (LCS): 528 nm

pH (23° C.): 7.5

EXAMPLE 2: PRODUCTION OF THE POLYURETHANE DISPERSION (B)

[0300] 75 g of PolyTHF® 1000 and 350 g of PolyTHF® 2000 were heated to 70° C. Subsequently, a mixture of 33.9 g of hexamethylene diisocyanate, 49.7 g of isophorone diisocyanate and 8.7 g of Desmodur N 3300 (HDI trimer having an NCO content of about 21.8% to DIN EN ISO 11 909) was added, and the mixture was stirred at 100-115° C. until the NCO value had gone below the theoretical value. The finished prepolymer was dissolved with 920 g of acetone at 50° C. and then a solution of 3.2 g of ethylenediamine, 12.9 g of diaminosulfonate, 11.7 g of diethanolamine and 145 g of water was metered in. The mixture was stirred for a further 15 min. This was followed by dispersion by addition of 1080 g of water. Subsequently, the solvent was removed by distillation under reduced pressure, and a storage-stable dispersion was obtained; the solids content was adjusted by addition of water.

Solids content: 52%
Particle size (LCS): 307 nm

Viscosity: 105 mPa s

[0301] Tg of polyurethaneurea: −78.0° C.

THERMOPLASTIC FOAM PRODUCED FROM TWO SPECIFIC POLYURETHANE DISPERSIONS (EXAMPLES)

[0302] All the foams described here are white and do not include any dyes or pigments.

PRODUCTION OF THE POLYURETHANE FOAM (COMPARATIVE EXAMPLE 1)

[0303] 2 kg of the above-described aqueous polyurethane dispersion (A) were mixed with 0.155 kg of a 40% by weight aqueous Pluronic PE6800 solution (from BASF SE, Germany) including 3.45% by weight of citric acid (from Bernd Kraft, Germany) by means of a Dispermat from VMA-Getzmann GmbH. The mixture was then beaten in a Pico-Mix from Hansa-Mixer to give a foam having a density of 200 g/l. The beaten foam was cast onto a polyolefin-coated release paper (Felix Schoeller Y05200) of width 30 cm at a coater setting of 3000 μm. This foam was dried at 120° C. for 30 minutes.

TABLE-US-00001 TABLE 1 Foam properties of comparative example 1 Parameter: Unit Result: Thickness mm 1.1 Foam density (dry) g/l 222 Crack area % 5.3 Crack width Average mm 2.46 SD mm 1.44 Smallest value mm 0.54 Greatest value mm 7.97 Crack depth Average mm 0.39 SD mm 0.12 Viability % 75 Tensile stress at break kPa 1095 Elongation at break % 239 Average pore size μm 427

PRODUCTION OF THE POLYURETHANE FOAM (COMPARATIVE EXAMPLE 2)

[0304] 4.5 kg of the above-described aqueous polyurethane dispersion (A) were mixed with 0.349 kg of a 40% by weight aqueous Pluronic PE6800 solution (from BASF SE, Germany) including 3.45% by weight of citric acid (from Bernd Kraft, Germany) and 0.225 kg of Niax L6889 (from Momentive Performance Materials Inc., USA) by means of a Dispermat from VMA-Getzmann GmbH. The mixture was then beaten in a Pico-Mix from Hansa-Mixer to give a foam having a density of 200 g/l. The beaten foam was cast onto a polyolefin-coated release paper (Felix Schoeller Y05200) of width 30 cm at a coater setting of 3000 μm. The foam was dried at 130 to 140° C. for 7 minutes.

TABLE-US-00002 TABLE 2 Foam properties of comparative example 2 Parameter: Unit Result: Thickness mm 2.4 Foam density (dry) g/l 128 Crack area % — Crack width Average mm — SD mm — Smallest value mm — Greatest value mm — Crack depth Average mm — SD mm — Viability % 18 Tensile stress at break kPa 334 Elongation at break % 208 Average pore size μm 431

PRODUCTION OF THE POLYURETHANE FOAM (INVENTIVE EXAMPLE 1)

[0305] 3.19 kg of the above-described aqueous polyurethane dispersion (A) were mixed with 1.367 kg of polyurethane dispersion (B), 0.91 kg of a 10% by weight aqueous Rheolate 208 dispersion (from Elementis Specialties, Germany) and 0.353 kg of a 40% by weight aqueous Pluronic PE6800 solution (from BASF SE, Germany) including 3.45% by weight of citric acid (from Bernd Kraft, Germany) by means of a Dispermat from VMA-Getzmann GmbH. The mixture was then beaten in a Pico-Mix from Hansa-Mixer to give a foam having a density of 200 g/l. The beaten foam was cast onto a polyolefin-coated release paper (Felix Schoeller Y05200) of width 30 cm at a coater setting of 3000 μm. The foam was then dried at 130 to 140° C. for 7 minutes.

TABLE-US-00003 TABLE 3 Foam properties of inventive example 1 Parameter: Unit Result: Thickness mm 1.8 Foam density (dry) g/l 159 Crack area % 0.0 Crack width Average mm — SD mm — Smallest value mm — Greatest value mm — Crack depth Average mm — SD mm — Viability % 85 Tensile stress at break kPa 377 Elongation at break % 248 Average pore size μm 467

[0306] No detectable cracks were detected in the foam produced according to inventive example 1, which is the reason why there are no figures for crack width and crack depth in table 3. Moreover, on comparison of the results from tables 1 to 3, it is apparent that the inventive mixture of dispersions (A) and (B) gives an article that has been foamed in accordance with the invention and has no cracks and nevertheless has high viability. The foamed articles according to the comparative examples have either a low viability or cracks.