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DE-102024210859-A1 - Cross-linked TPU foams with excellent feel, flexibility and resilience.

DE102024210859A1DE 102024210859 A1DE102024210859 A1DE 102024210859A1DE-102024210859-A1

Abstract

The invention relates to a foam made of a cross-linked and foamed thermoplastic polyurethane mixture, wherein the thermoplastic polyurethane mixture comprises at least one thermoplastic polyurethane, at least one blowing agent and at least one cross-linking agent having at least two functional groups.

Inventors

  • Matthias Knecht
  • Holger Schlottke
  • Gabriele Wittmann

Assignees

  • Benecke-Kaliko GmbH

Dates

Publication Date
20260513
Application Date
20241112

Claims (10)

  1. Foam made of a cross-linked and foamed thermoplastic polyurethane mixture, wherein the thermoplastic polyurethane mixture comprises at least one thermoplastic polyurethane, at least one blowing agent and at least one cross-linking agent having at least two functional groups.
  2. Foam according to Claim 1 , wherein the thermoplastic polyurethane mixture contains at least 60 wt.%, preferably at least 80 wt.%, of the at least one thermoplastic polyurethane.
  3. Foam according to one of the preceding claims, wherein the proportion of the at least one crosslinking agent having at least two functional groups in the thermoplastic polyurethane mixture is 0.5 to 10 wt.%, preferably 1 to 3 wt.%, based on the weight of the at least one thermoplastic polyurethane.
  4. Foam according to one of the preceding claims, wherein the at least one thermoplastic polyurethane comprises or is at least one aliphatic or aromatic thermoplastic polyurethane, preferably at least one aliphatic thermoplastic polyurethane.
  5. Foam according to one of the preceding claims, wherein the at least one thermoplastic polyurethane comprises one or more segments selected from polyester, polycarbonate, polycaprolactam, polyether segments or combinations thereof.
  6. Foam according to one of the preceding claims, wherein the at least one thermoplastic polyurethane has at least one, preferably all, of the following properties: - a melting range in the range of 80 to 200 °C, determined by differential scanning calorimetry according to DIN EN ISO 11357-1 (2023-03), - a hardness in the range of Shore A 40 to Shore D 80, determined according to DIN ISO 48-4 (2018-08), - an abrasion loss of less than 100 mm³ , determined according to ISO 4649A:2021-06, - a rebound elasticity of less than 25%, determined according to ISO 4662:2017, - a compression set in the range of 5 to 50%, determined according to ISO 8151-2019 (72 h at 23°C) and/or a compression set in the range of 10 to 60%, determined according to ISO 815-1:2019 (24 h at 70°C).
  7. Foam according to one of the preceding claims, wherein the at least one crosslinking agent comprising at least two functional groups comprises or is a multifunctional acrylate, a multifunctional methacrylate, a compound with at least two olefinic groups or a combination thereof, preferably a multifunctional acrylate, a multifunctional methacrylate or a combination thereof.
  8. Foam according to one of the preceding claims, wherein the thermoplastic polyurethane mixture contains one or more additives selected from a hardener, in particular a peroxide compound, a mineral filler, a processing aid, a pigment or a combination thereof.
  9. Method for producing a foam according to one of the Claims 1 until 8 , comprising the following steps: a) calendering or extruding the thermoplastic polyurethane mixture to form a molded body, b) crosslinking and foaming the molded body, wherein the molded body is first crosslinked and then foamed, or the molded body is first foamed and then crosslinked, or the molded body is simultaneously foamed and crosslinked, wherein the crosslinking is preferably carried out by radiation crosslinking, in particular electron beam crosslinking, or by means of a hardener, wherein radiation crosslinking is preferred.
  10. Using a foam according to one of the Claims 1 until 8 for components of vehicle interiors or industrial applications, for films, seats, add-on parts, floor coverings, yoga mats, upholstery or sound insulation, especially for components of automotive interiors, and/or for the production of a deep-drawn foam article.

Description

The invention relates to a foam made of a cross-linked and foamed thermoplastic polyurethane mixture, comprising at least one thermoplastic polyurethane, at least one blowing agent and at least one cross-linking agent, a method for producing the foam and its use. Foam materials made of plastic, such as polyurethane (PUR) foams, have a wide range of applications. They are used, for example, in the production of components for automotive interiors or for industrial applications such as seats or upholstery. A more recent development is foams based on thermoplastic elastomers, such as thermoplastic polyolefins (TPO), thermoplastic copolyester elastomers (TPC) or thermoplastic polyamides (TPE-A). TPO foams are generally quite firm. They tend to develop irreversible dents and have poor resilience. They are also prone to wrinkling when bent. The number of manufacturers and types of TPC foams and TPE-A foams is limited, which affects cost-effectiveness. Polyurethane foams, e.g., for pour-in-place applications, are generally highly cross-linked and therefore no longer suitable for deep drawing. Their recyclability is likely to be limited. Furthermore, polyurethane foams, which are mostly aromatic types, typically do not exhibit good aging resistance. Particle foams based on thermoplastic polyurethane (TPU) are also known, but these can only be processed as particles. Deep drawing is not possible. DE 102020212800 A1 concerns a foam based on thermoplastic copolyester elastomers (TPC) and a method for its production. EP 1650255 A1 describes a cross-linked foam made of a copolymer with polyamide blocks and polyether blocks with a density of 20 to 700 kg/m 3 . US 20210324196 A1 relates to a cross-linked foam made of a copolymer with polyamide blocks and polyether blocks, wherein the polyamide blocks and polyether blocks have a certain average molar mass and the weight ratio of the polyamide blocks to the polyether blocks is 0.1 to 0.9. US 8865052 B2 This applies to thermoplastic polyurethanes that exhibit an unsaturation in the polymer backbone that facilitates crosslinking. The unsaturation can be present in the soft segment, the hard segment, or both. The TPU can be molded like a thermoplastic and subsequently crosslinked into thermoset articles by electron beam irradiation. The object of the present invention was therefore to overcome the disadvantages of the prior art. In particular, a foam was to be provided that exhibits excellent flexibility and resilience. Furthermore, the foam should have a good feel. In addition, the foam should allow for good recyclability. The inventors discovered that the problem could be solved by using a mixture based on a thermoplastic polyurethane in combination with a crosslinking agent having at least two functional groups to produce the foam. Crosslinking agents with at least two functional groups are also frequently referred to as crosslinking aids or co-crosslinkers in the field of elastomers. The invention thus relates to a foam made of a cross-linked and foamed thermoplastic polyurethane mixture, wherein the thermoplastic polyurethane mixture comprises at least one thermoplastic polyurethane, at least one blowing agent and at least one cross-linking agent having at least two functional groups. The foam according to the invention exhibits very good resilience. Irreversible dent formation, as frequently observed in prior art foams, can be largely avoided. Furthermore, an improved feel of the foam is achieved, even in combination with a top film. The foam according to the invention is thermoformable, so that even complex components, e.g., instrument panels, do not need to be manufactured on site. Pour-in-place applications, as frequently used with PUR foams, are no longer necessary, which simplifies the technology. At the installation site, this results in process savings and a reduced hazard potential due to the raw materials with very low emissions. The foam according to the invention can be recycled. After use, it can be remelted or partially melted, or ground into fine PUR particles and reintroduced into the mixture without significant deterioration of its properties, so that it can be used as an additive for the production of new foams. The material is also easy to recycle when combined with TPU top films (monomaterial). A particular advantage of the foam according to the invention is its ease of processing. Due to its excellent flexibility and soft feel, the foam can be sewn and covered with leather or upholstery without leaving permanent creases or folds. Another advantage is improved acoustics compared to TPO foams. The invention is explained in detail below. The foam according to the invention is based on a thermoplastic polyurethane mixture which, after crosslinking and foam formation, forms the foam. The thermoplastic polyurethane mixture comprises at least one thermoplastic polyurethane, at least one blowing agent, and at least one crosslinking agent having at least two f