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EP-4735499-A1 - STORAGE-STABLE COATED PARTICLES AND THEIR PREPARATION

EP4735499A1EP 4735499 A1EP4735499 A1EP 4735499A1EP-4735499-A1

Abstract

The present invention relates to a process for the preparation of storage-stable coated particles of a moldable thermoplastic particle foam comprising the steps of a1) bringing the particles into contact with an aqueous polyurethane dispersion, the polyurethane having at least a first glass transition T g1 and a second glass transition temperature T g2 , wherein T g1 is below 0°C and T g2 is higher than 25 °C, resulting in at least partly coated particles; and a2) drying the coated particles. The invention further relates to a process for the preparation of a shaped body, storage-stable, at least partly coated particles and shaped bodies thereof.

Inventors

  • LICHT, ULRIKE
  • CRISTADORO, Anna Maria
  • POESELT, ELMAR
  • DIERSSEN, JENS PETER
  • VOGELSANG, Volker
  • VALLO, MARTIN
  • GEHRINGER, LIONEL

Assignees

  • BASF SE

Dates

Publication Date
20260506
Application Date
20240619

Claims (20)

  1. 1 . A process for the preparation of storage-stable coated particles of a moldable thermoplastic particle foam comprising the steps of ai) bringing the particles into contact with an aqueous polyurethane dispersion, the polyurethane having at least a first glass transition temperature T gi and a second glass transition temperature T g 2, wherein T gi is below 0°C and T g 2 is higher than 25 °C, the glass transition temperature being measured according to DIN EN ISO 11357-2 (2014), resulting in at least partly coated particles; a 2 ) drying the coated particles.
  2. 2. The process of claim 1 , wherein T gi is below -10 °C.
  3. 3. The process of claim 1 or 2, wherein T g 2 is higher than 40 °C.
  4. 4. The process of any of claims 1 to 3, wherein T g 2 is higher than 50 °C.
  5. 5. The process of any of claims 1 to 4, wherein T g 2 is higher than 60 °C.
  6. 6. The process of any of claims 1 to 5, wherein the moldable thermoplastic particle foam is an expanded thermoplastic elastomer.
  7. 7. The process of any of claims 1 to 6, wherein the moldable thermoplastic particle foam is an expanded thermoplastic polyurethane.
  8. 8. The process of any of claims 1 to 7, wherein the aqueous polyurethane dispersion has a solid content of at least 30 wt.-% based on the total weight of the dispersion.
  9. 9. The process of any of claims 1 to 8, wherein the aqueous polyurethane dispersion has a solid content in the range of 35 wt.-% to 60 wt.-% based on the total weight of the dispersion.
  10. 10. The process of any of claims 1 to 9, wherein the aqueous polyurethane dispersion has a viscosity of less than 300 mPas at 23 °C, measured according to DIN EN ISO 3219- 2:2021 at 23°C and a shear rate of 250 S’ 1 .
  11. 11 . The process of any of claims 1 to 10, wherein the aqueous polyurethane dispersion has a viscosity of less than 200 mPas at 23 °C, measured according to DIN EN ISO 3219- 2:2021 at 23°C and a shear rate of 250 S’ 1 .
  12. 12. The process of any claims 1 to 11 , wherein the polyurethane of the aqueous polyurethane dispersion has a T gi from -10 °C to -60 °C and a T g 2 from 60 °C to 90 °C.
  13. 13. The process of any of claims 1 to 12, wherein the polyurethane of the aqueous polyurethane dispersion is prepared from a) at least one organic diisocyanate, selected from diisocyanates of the formula X(NCO)2, where X is a noncyclic aliphatic hydrocarbon radical having 4 to 15 carbon atoms, a cycloaliphatic hydrocarbon radical having 6 to 15 carbon atoms, an aromatic hydrocarbon radical having 6 to 15 carbon atoms, or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms, wherein the amount of aromatic diisocyanates is less than 60 mol-%, based on the sum of all organic diisocyanates a); b1 ) at least one dihydroxy compound having a molecular weight of 500 g/mol to 5000 g/mol and selected from the group consisting of polyesterdiols, polyetherols and polytetrahydrofuran; b2) at least one dihydroxy compound selected from the group consisting of branched or unbranched acyclic diols having 2 to 8 C atoms, or cyclic diols having 3 to 8 C atoms; c) at least one compound having at least one group reactive toward isocyanate groups, and additionally carrying at least one ionic group or one group which can be converted into an ionic group, d) optionally further compounds different from a) to c).
  14. 14. The process of claim 13, wherein the compounds c) contain a group selected from carboxylate groups and sulfonate groups as ionic group.
  15. 15. The process of claim 13 or 14, wherein the aqueous polyurethane dispersion comprises in addition at least one additive selected from the group consisting of pigments, dyes, odor, filling agents, bio-based and/or biodegradable additives, UV-, heat-stabilizer, flame retardants such as expandable graphite, additives which generate antistatic properties, electrical conductivity, additives, which reduce dirt-uptake, anti-slip additives, antimicrobial additives, wax, crosslinking agents, surface functionalized fillers, foamable additives such as Expancell, additives which can be irradiated by an electromagnetical field, and/or radiofrequency, and/or microwave, ionic surfactants, nonionic surfactants, rheology modifiers, fillers, anti-blocking additives, other aqueous dispersions, crosslinkers, plasticizers, stabilizers against hydrolytic degradation, antifoam agents and biocides.
  16. 16. The process of any of claims 1 to 15, wherein in step ai) the bringing into contact is realized by mixing or spraying.
  17. 17. The process of any of claims 1 to 16, wherein in step ai) the bringing into contact is realized by mixing from 0.5 minutes to 6 hours.
  18. 18. The process of any of claims 1 to 17, wherein in step ai) the bringing into contact is realized by mixing until a residual water content of 3 % or lower, based on the total weight of the at least partly coated particle.
  19. 19. The process of any of claims 1 to 18, wherein the at least partly coated particles are coated in an amount of from 0.1 wt.-% to 40 wt.-% based on the total weight of particle and coating.
  20. 20. The process of any of claims 1 to 19, wherein during step 82) the at least partly coated particles are kept moving until the particles are tacky-free.

Description

Storage-stable coated particles and their preparation Description The present invention relates to a process for the preparation of storage-stable coated particles of a moldable thermoplastic particle foam comprising the steps of ai) bringing the particles into contact with an aqueous polyurethane dispersion, the polyurethane having at least a first glass transition Tgi and a second glass transition temperature Tg2, wherein Tgi is below 0°C and Tg2 is higher than 25 °C, resulting in at least partly coated particles; and a2) drying the coated particles. The invention further relates to a process for the preparation of a shaped body, storagestable, at least partly coated particles and shaped bodies thereof. Moldable thermoplastic particle foams including thermoplastic elastomer particle foams are used, for example, for the production of any solid foam bodies, for example for exercise mats, body protectors, lining elements in automobile construction, sound and vibration dampers, packaging or shoe soles. Conventionally, a mold with foam particles is filled followed by melting the individual foam particles on their surface by the action of heat and in this way to connect them to one another to form a particle foam. Thus, in addition to simple products, complex semi-finished products or molded parts with undercuts can be produced. Moldable thermoplastic particle foams are known in the art and described, e.g., in Robin Britton (Author), Update on Moldable Particle Foam Technology, Rapra technology Ltd, 2009. Expanded thermoplastic elastomers, especially expanded thermoplastic polyesters (E-TPC), expanded thermoplastic copolyamides (E-TPA), expanded thermoplastic polyurethanes (E-TPU), represent specific moldable thermoplastic particle foams. Expanded thermoplastic elastomers are known in the art. For example, WO 2018/082984 A1 describes particle foams based on expanded thermoplastic elastomers. WO 2008/087078 A1 describes hybrid systems consisting of foamed thermoplastic elastomers and polyurethanes. An exemplary thermoplastic polymer is expanded thermoplastic polyurethane (E-TPU), which is commercially available, e.g. marketed by BASF under the name Infinergy®. E-TPU particles represent mainly to fully closed-cell particle foam. Thermoplastic polyurethane (e.g. Elastollan®) is expanded resulting in a particle foam and can be processed on standard molding machines. Thanks to its closed particle surface and the chemical nature of the used TPU, standard E-TPU grades also absorbs only low amounts of water. Like the TPU on which it is based, it can also be characterized by high breaking elongation, tensile strength and abrasion resistance, combined with good chemical resistance. Fast prototyping of 3D objects made out of expanded thermoplastic elastomers is nowadays not easy to realize. Typically, isocyanate-containing binders are used for bonding the particles or water vapor and appropriate machines, like a steam chest molder. Both approaches are not easily accessible due to health safety reasons, energy costs or due to lack of accessibility of appropriate machinery (steam-chest molder). Moreover, the use of water vapor allows only molding particles of the same kind, whereas a coating on an E-TPU particle or the usage of a water-based binder may allow bonding E-TPU particles of different kind (Glass transition temperature, Melting point) and size, but also bonding of different TPUs or even different particle foams, e.g. different mixtures of E-TPS, E-PS, E-PP, E-TPA, E-TPC, E-TPO and the like. The application of a coating allows as well the adjustment of the mechanical performance and applicability by incorporation of additivities, like for example pigments or dyes, flame retardants or antistatic agents, directly to the particle surface. Filling agents for example allow the increase of the stiffness of the final part, while the use of additives which are for example excitable by an electro-magnetic field allow the moldability of the coating and thereby reducing the required energy for molding. As additives can be used pigments, dyes, odor, filling agents, bio-based and/or biodegradable additives, UV-, heat-stabilizer, flame retardants such as expandable graphite, additives which generate antistatic properties, electrical conductivity, additives, which reduce dirt-uptake, antislip additives, antimicrobial additives, wax, crosslinking agents, surface functionalized fillers, foamable additives such as Expancell, additives which can be irradiated by an electromagnetical field, and/or radiofrequency, and/or microwave. WO2022/223438 A1 describes different water-based binders for coating particles that can be brought into the shape of said 3D parts. US 6 616 797 B1 describes the formation of adhesive bonds by a process that includes applying a dispersion containing a polyurethane which has structural units of formula (I) to a surface. The dispersion is first coated onto the surface to form a coating. The coating is dried