Multilayer composite

Abstract

The invention relates to a multilayer composite comprising at least one single- or multi-layer carrier layer and at least one single- or multi-layer functional layer, wherein the carrier layer comprises at least one thermoplastic polyolefin and wherein the functional layer comprises more than 50 wt.% of a styrene block copolymer based on the total weight of the functional layer. Furthermore, the invention relates to seating furniture comprising a cover made of such a multilayer composite. The invention relates to a multilayer composite comprising at least one single- or multi-layer carrier layer and at least one single- or multi-layer functional layer, wherein the carrier layer comprises at least one thermoplastic polyolefin and wherein the functional layer comprises more than 50 wt.% of a styrene block copolymer based on the total weight of the functional layer. Furthermore, the invention relates to seating furniture comprising a cover made of such a multilayer composite.

Description

[0001] The invention relates to a multi-layer composite, in particular synthetic leather, comprising at least one single- or multi-layer carrier layer and at least one single- or multi-layer functional layer. Furthermore, the invention relates to seating furniture comprising a cover made of such a multi-layer composite.

[0002] Particularly in the automotive, furniture, and contract sectors, today's artificial leathers are largely based on PVC, polyurethane, and polyolefins. In addition to leather, PVC and PUR artificial leathers have proven themselves for seating areas because they meet the high demands placed on them in terms of abrasion and scratch resistance. Artificial leathers based on polyolefins, however, cannot withstand these high levels of stress and are instead used for components such as instrument panels, door sides, and other add-on parts that require less mechanical stress but, for example, high UV exposure. PVC artificial leathers are also used in the furniture sector due to their excellent flame-retardant properties. Typical artificial leathers use textiles based on cotton, polyester, polyamide, and polypropylene.

[0003] PVC has a high density (approx. 1.4 g / cm 3) and therefore also a high weight. Plasticizers are needed to make PVC constructions soft and flexible. These plasticizers, in turn, lead to embrittlement of the material due to the migration of short-chain molecules. PUR also has a high density (approx. 1.1 - 1.2 g / cm 3 ) and requires chemicals (e.g., isocyanates) that are hazardous to health during production. Synthetic leather made of polyurethane is usually cross-linked and then no longer freely embossable. In addition to the unpleasant odor of PVC and polyurethane synthetic leather, the high emissions and halogen content are also detrimental from an environmental perspective.

[0004] Polyolefin synthetic leather, on the other hand, has very low abrasion resistance and is too hard to the touch compared to PVC or PUR. Furthermore, constructions made of thermoplastic polyolefins (TPO) are very prone to creasing, resulting in visible, permanent creases and creases during processing.

[0005] Recycling is very complex or sometimes impossible for all synthetic leather constructions. The functional coating and textile backing are typically made of different materials, such as PVC synthetic leather and polyester textile. Furthermore, the functional coating can only be separated from the backing with great effort or even impossible. The laborious separation of coating and backing generates additional unnecessary costs. Therefore, these constructions are often not recycled but incinerated, thus contributing to the already high CO2 emissions.

[0006] In the furniture sector, there are sometimes very strict flame-retardant requirements. These are typically met today with specially treated cotton backings. These, in turn, are usually combined with a PVC or PUR-based coating.

[0007] EP 3233483 B1 discloses a composite film, particularly for vehicle interior trim, comprising a decorative film containing a thermoplastic styrene block copolymer and a thermoplastic homopolymer or copolymer of propylene. This composite film is characterized by high scratch and abrasion resistance.

[0008] Based on the findings from EP 3233483 B1, the object of the present invention was to develop a multilayer composite that meets the specific requirements for use as a covering for seating furniture while simultaneously offering advantages in terms of product sustainability. In particular, the aim is to develop a multilayer composite that offers improved abrasion resistance while simultaneously providing a pleasant and soft surface feel.

[0009] This object is achieved by a multi-layer composite which has at least one single- or multi-layer carrier layer and at least one single- or multi-layer functional layer, wherein the carrier layer comprises at least one thermoplastic polyolefin and wherein the functional layer comprises more than 50 wt.%, in particular more than 60 wt.%, of a styrene block copolymer (SBC) based on the total weight of the functional layer. In order to achieve sufficient abrasion resistance and thus create suitability for seating applications, the SBC content of the functional layer must be above 50 wt.%, based on the total weight of the functional layer. Such a multi-layer composite is particularly well suited for use as artificial leather covering in seating applications, e.g. seating furniture, due solely to its softness, feel and flexibility combined with high abrasion resistance.Another advantage is the polyolefinic base, which is characterized by its low density (approx. 0.9 -1.0 g / cm. 3 ) enables abrasion-resistant lightweight constructions.

[0010] In advantageous embodiments, the styrene block copolymer (SBC) is selected from the list consisting of styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-ethylene-propylene-styrene block copolymer (SEPS) and mixtures thereof. These SBCs are particularly suitable because they are compatible with each other and have very good resilience (hysteresis). With the high proportion of SBCs according to the invention, a softer and therefore more pleasant feel can be achieved. This is also reflected in the reduced or even absent "cracking" during mechanical processing of the multi-layer composite, e.g., when milling artificial leather formed from the multi-layer composite.

[0011] In principle, the material hardness of a multilayer composite according to the invention is not limited. In advantageous embodiments, particularly for use of the multilayer composite as synthetic leather, material hardnesses of the polymers used in the range of 20 to 80 Shore A (according to DIN ISO 7619-1) are suitable. A pleasant feel, i.e., softness or sufficiently low hardness, can be achieved at values ​​below 60 Shore A (according to DIN ISO 7619-1).

[0012] The functional layer comprises more than 50 wt.% of at least one styrene block copolymer (SBC), based on the total weight of the functional layer. The higher the proportion of SBCs, the better the material's resilience (hysteresis). For optimized crease resistance, the SBC content should be more than 60 wt.%, in particular between 65 and 90 wt.%, based on the total weight of the functional layer. In this context, it has surprisingly been discovered that the amorphous polymer content in the formulation must be maximized to also improve crease resistance.

[0013] In advantageous embodiments, the functional layer comprises at least two styrene block copolymers (SBCs) that differ at least in molecular weight. For example, the SBCs have a molecular weight of at least 50,000 Da. The difference in molecular weight between two SBCs is at least 10,000 Da, preferably at least 20,000 Da, more preferably at least 30,000 Da. The values ​​stated are mass-average molecular weights (Mw), which can be determined using high-temperature gel permeation chromatography (HT-GPC). Preferably, one SBC has a hardness of 20 to 80 Shore A, and another SBC has a hardness of more than 80 Shore A, each measured according to DIN ISO 7619-1. Such blends form morphologies that have a positive effect on the abrasion properties, i.e., reduce the abrasion of the material. In contrast to synthetic leather based on TPO, abrasion can be significantly improved and optimized for seating applications.

[0014] In particularly advantageous embodiments, the functional layer comprises 60 to 90 wt.% SBC, in particular 60 to 80 wt.%, based on the total weight of the functional layer. In addition, the functional layer in this embodiment may comprise at least two styrene block copolymers (SBCs) that differ at least in the glass transition temperature (T G ). Preferably, the at least two SBCs have a T G s in the range of T G-60°C to 30°C. Preferably, the Tg of at least one of the two SBCs is between 0 and 20°C, and the other between -50 and -10°C (determined by DMA). This allows the functional layer to be improved in terms of flexibility and kink resistance. In addition, such constructions are particularly resistant to embrittlement.

[0015] The functional layer preferably does not contain any low-molecular-weight components used as plasticizers, such as mineral oils. This prevents migration from the layer and further counteracts embrittlement of the material.

[0016] In advantageous embodiments, the functional layer of a multilayer composite according to the invention is formed as a compact layer. The compact layer is preferably distinguished from a foamed layer in that it possesses the required temperature stability both for the manufacturing process and for the use of the composite film of the component with the desired softness. The composite film according to the invention can also be expediently laminated to a textile fabric, e.g., a textile carrier. In this case, it is particularly suitable, particularly in a grained form, for use as artificial leather for the automotive or fashion sectors. Furthermore, the functional compact layer can be laminated to part of another compact or foamed layer prior to lamination. Finally, the two-layer compact composite film can be extruded to form a complete composite structure.The basic manufacturing processes for composite structures are familiar to the expert and require no further explanation. Such compact films offer the advantage of producing geometrically more complex components, for example, using the thermoforming process with stretch ratios of > 80%.

[0017] In principle, there are many possibilities for the formation of the carrier layer.

[0018] In advantageous embodiments, the thermoplastic polyolefin of the carrier layer comprises a polypropylene (homo or random copolymer), a polyethylene, or a mixture of a polypropylene matrix and ethylene-propylene rubber. Mixtures of the aforementioned polymers can also be used. Polypropylene is inexpensive and easy to process. Therefore, in particularly preferred embodiments, the carrier layer is based on a homo or random copolymer of polypropylene.

[0019] The carrier layer can be formed as a foam layer or as a compact textile layer. In embodiments in which the carrier layer is formed as a compact textile layer, the low-density compact film is bonded thermally and / or by adhesive bonding to the described functional layer. Such compact films can have a density of more than 800 kg / m³ and less than 1100 kg / m³, preferably from 800 to 1000 g / m³. The density can be determined according to DIN EN ISO 1183-1. The adhesive is also advantageously polyolefin-based. This contributes to the thermal and mechanical recycling of the entire multilayer composite. The carrier layer formed as a foam layer has the advantage that no adhesive (or adhesive) is required. Foamed polyolefin-based sheet materials with densities of 40 to 800 kg / m³ 3 are preferred in this context.

[0020] The multi-layer composite according to the invention has a carrier layer and at least one functional layer. All layers can be single-layer or multi-layer. In advantageous embodiments, the functional layer is formed entirely on a carrier layer. On the side not covered by the carrier layer, the functional layer preferably has a lacquer layer. When the multi-layer composite is used as artificial leather (e.g. for seating furniture or fashion items), the side of the functional layer covered by the lacquer layer forms the visible side of the multi-layer composite. Preferably, the functional layer is completely covered on the visible side with a single-layer or multi-layer lacquer layer. This makes it possible to adjust the degree of gloss and the feel of the material and to provide additional mechanical and / or chemical protection for the functional layer.

[0021] The coating materials of the coating layer can comprise a polymer selected from the group consisting of polyurethane, polyacrylate, polysiloxane, polyester, polyether, or copolymers thereof. The single- or multi-layer coating layer can be solvent-based or water-based. A solvent in the context of the invention is a short-chain organic molecule in the liquid state. Water is preferred over solvents with regard to health and environmental hazards. In alternative embodiments, the coating composition can be based on coating materials that are essentially free of solvents and / or water. Such a system consists essentially of suitable polymers.

[0022] In some embodiments, the multilayer composite is a halogen-free and flame-resistant construction, particularly for use in seating furniture (e.g., car seats). Materials / constructions that meet the requirements of the fire standards BS IS-1 (20 seconds), DIN EN 53438, and BS 5852 IS-5 are referred to as flame-resistant.

[0023] To improve flame protection, a flame retardant can be added to each layer. The flame retardant is preferably selected from the list consisting of ammonium polyphosphate (APP), piperazine pyrophosphate, aluminum phosphinates, products from the reaction of methylphosphonic acid with diamine, melamine phosphate, melamine cyanurate, melamine, aluminum trihydrate, and mixtures thereof. Piperazine pyrophosphate, ammonium polyphosphate, and mixtures of phosphorus compounds with nitrogen compounds (synergists) are particularly suitable. The proportion of flame retardant can range from 5% to 70% by weight, based on the total mass of the layer, depending on fire protection requirements.

[0024] According to the invention, the multilayer composite is fully mechanically recyclable and suitable for use as artificial leather (e.g. for seating furniture or fashion items). This is possible because all polymer types used are the same or chemically similar. This can be made possible if the entire multilayer composite is based on polyolefins, i.e. contains less than 50 wt. %, preferably less than 30 wt. %, more preferably less than 10 wt. %, most preferably less than 5 wt. %, in each case based on the total weight of the multilayer composite, of other polymer types. It is important that all components of the construction, i.e. the multilayer composite, have thermoplastic properties in order to form a construction that is up to 100% recyclable. This means that the layers of the multilayer composite do not first have to be separated from one another in order to be reused (recycled).In this way, the multi-layer composite can be mechanically recycled, enabling cost-effective, fast and easy recycling of the material.

[0025] In embodiments in which the carrier layer is formed as a compact textile layer, an adhesive / bonding agent is required to bond the compact textile layer to the functional layer. This adhesive layer can be based on a polyolefin, particularly for recycling reasons.

[0026] In preferred embodiments, the entire multilayer composite is halogen-free, i.e., free of halogen-containing compounds. This further contributes to the product's sustainability by avoiding environmentally harmful substances. This contributes to a product with exceptionally low emissions (according to VDA 278).

[0027] All of the layers mentioned can be single-layer or multi-layer. The total layer thickness of a multi-layer composite is preferably not less than 0.1 mm and not more than 5 mm. The functional layer preferably has a total layer thickness of up to 0.6 mm. In preferred embodiments, the functional layer is formed in two layers. The two layers differ in their hardness and the type of polyolefins. Preferably, the lower layer of the functional layer (e.g. the non-visible side of the functional layer) can be the softer layer with a hardness between 20 and 80 Shore A. The upper layer of the functional layer (the visible side of the functional layer) can be the harder layer with a hardness of more than 60 Shore A.

[0028] The compositions of the aforementioned layers may include additional additives. These serve to precisely adjust the material properties to the requirements of the respective application while improving the chemical, electrical, and mechanical properties. These can be stabilizers such as antioxidants, light stabilizers, heat stabilizers, and flame retardants, colorants, especially pigments, fillers, and / or reinforcing agents. UV light stabilizers, such as benzotriazole derivatives, are of particular importance. Among the antioxidants, sterically hindered phenol derivatives, lactones, phosphites, and / or sterically hindered amines are important. In particular, the functional layer comprises one or more additives selected from the list consisting of lubricants, fillers, stabilizers, phosphites, phenolic antioxidants, UV absorbers, hindered amine light stabilizers (HALS), and / or pigments.

[0029] In preferred embodiments, the multi-layer composite is a synthetic leather.

[0030] The multilayer composite is suitable for use in, for example, seating furniture, automotive interiors, headliners, ceiling panels, wall coverings, fashion items, or footwear. For example, the multilayer composite can be a handbag, wallet, garment, pillowcase, seat cushion cover, chair cushion, chair cover, armchair cover, sofa cover, car seat cover, or steering wheel cover.

[0031] The invention also relates to seating furniture comprising a cover made of a multi-layer composite as described above. Examples

[0032] The invention is explained below using examples. These are to be understood as exemplary embodiments and do not limit the invention in any way.

[0033] Multilayer composite structures (A, B, C) according to the invention were produced and compared with two conventional multilayer composite structures (V1, V2). All structures A, B, C, V1, and V2 have a carrier layer based on a homo-PP formulation. The functional layer of the structures is composed according to the formulations shown in Table 1. The SEBS1 to SEBS3 used differ in hardness and molecular weight. SEBS1 has a Shore A hardness of 61, SEBS2 has a Shore A hardness of 43, and SEBS3 has a Shore A hardness of 90. SEBS3 has a molecular weight (mass average molecular weight, Mw) of 275,000 Da, SEBS1 has 174,000 Da, and SEBS2 has 139,000 Da. The molecular weight was determined using high-temperature gel permeation chromatography (HT-GPC) in trichlorobenzene at 160°C and a conventional calibration with polystyrene standards.

[0034] The thermoplastic polyolefin (TPO) used here was a material consisting of polypropylene and ethylene-propylene rubber with a Shore D hardness of 30. For the comparative examples, a polyolefin elastomer (POE) with a Shore A hardness of 54 and an olefin coblock polymer (OBC) with a Shore A hardness of 71 were used.

[0035] An organophosphorus salt (FR1), aluminum hydroxide (FR2), and a mixture of phosphorus compounds and nitrogen compounds (FR3) were selected as flame retardants (FR). The amounts given are in wt.% and are based on the total weight of the functional layer used. Table 1: Recipes used A B C D E V1 V2 V3 V4 V5 SEBS1 90 80 60 90 90 90 SEBS2 60 50 SEBS3 50 POE1 60 OBC1 60 TPO (PP-EP-Rubber, Shore D 30) 10 20 40 40 40 40 10 10 10 FR1 - - - - - - - 35 FR2 35 FR3 35 Other additives 5 5 5 5 5 5 5 5 5 5

[0036] The multilayer composite structures were tested for their suitability as seating furniture using various mechanical tests. Table 2 shows a summary of these tests. The abrasion test was conducted in accordance with DIN EN ISO 5470-2:2021, using STFI-MD-100 (corresponding to DIN EN ISO 12947-1) as the abrasive fabric. A rotation speed of 51,200 was set for the abrasion tests, and the weight loss of the samples was determined. Hardness tests were carried out according to EN ISO 868:2003. Crease resistance was measured according to DIN EN ISO 32100:2019-02, with the samples measured at room temperature and a rotation speed of 100,000. Flame retardancy was tested according to DIN EN 4102-B2. Crease resistance was evaluated according to an internal procedure. A sample of foil or artificial leather is crumpled into a ball by hand and then laid out flat. The multi-layer composite orThe artificial leather is then visually assessed after 15 minutes, 60 minutes, and 24 hours for the recovery of creases from "--" to "++". At the lower end of the scale, "--" means that all originally inserted creases are retained, and at the upper end of the scale, "++" means that no visible creases are visible. Table 2: Results from the mechanical tests. A B C D E V1 V2 V3 V4 V5 Abrasion / mg 1 1 88 81 0 182 237 291 1 1 Hardness / Shore A 63 65 72 63 70 66 74 - - - Wrinkle resistance ++ ++ - - + - - Surface flame treatment F3 - - - - - - F1 F2 F1 Edge flaming K3 - - - - - - K3 K3 K1 Kink resistance RT / 100k OK OK OK OK OK OK OK nIO OK OK

[0037] The table shows that with increasing SBC content, abrasion and hardness decrease. Furthermore, the olefin-based formulations V1 and V2 exhibit significantly higher abrasion and crease susceptibility compared to B and C, despite similar Shore A hardness. C feels very hard and is prone to crease. Therefore, sample B represents the best compromise between softness and mechanical strength. Regarding flame resistance, FR3 was found to be the most suitable for the application, as the addition of FR3 does not negatively affect the mechanical properties and also ensures flame resistance.

[0038] In addition, recyclability tests were conducted. A multilayer composite according to the invention was mechanically shredded and melted on a rolling mill at 180°C, and processed into a film (e.g., for use as a functional layer in a multilayer composite according to the invention). The produced film differs slightly in its mechanical values, e.g., tensile strength and Shore A hardness, from a film that would be obtainable from newly acquired raw materials. Among other things, the hardness increases and the tensile strength decreases. This effect is due to the fact that the PP from the multilayer composite is also melted during melting and incorporated into the film mixture in the appropriate proportion. Nevertheless, the film made from the recycled material can also be used for other purposes. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3233483 B1 [0007, 0008]

Claims

[1] Multilayer composite comprising at least one single- or multi-layer carrier layer and at least one single- or multi-layer functional layer, wherein the carrier layer comprises at least one thermoplastic polyolefin and wherein the functional layer comprises more than 50 wt.% of a styrene block copolymer based on the total weight of the functional layer. [2] Multilayer composite according to claim 1, wherein the styrene block copolymer is selected from the list consisting of styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-ethylene-propylene-styrene block copolymer (SEPS) and mixtures thereof. [3] Multilayer composite according to one of claims 1 or 2, wherein the carrier layer is a foam layer or a compact textile layer and the thermoplastic polyolefin is a polypropylene. [4] Multilayer composite according to one of claims 1 to 3, wherein the carrier layer and the functional layer are connected by an adhesive layer. [5] Multilayer composite according to claim 4, wherein the adhesive layer is based on a polyolefin. [6] Multilayer composite according to one of claims 1 to 5, wherein the entire multilayer composite is halogen-free. [7] Multilayer composite according to one of claims 1 to 6, wherein the functional layer is a compact layer. [8] Multi-layer composite according to one of claims 1 to 7, wherein the functional layer has a visible side and the visible side is completely covered with a single- or multi-layer lacquer layer. [9] Multi-layer composite according to claim 8, wherein the single- or multi-layer lacquer layer is based on a polymer selected from the list consisting of polyurethane, polyacrylate, polysiloxane, polyester, polyether or copolymers thereof. [10] Multilayer composite according to one of claims 1 to 9, wherein at least one of the layers comprises a flame retardant and the flame retardant is selected from the list consisting of piperazine pyrophosphate, ammonium polyphosphate and mixtures of phosphorus compounds with nitrogen compounds and mixtures thereof. [11] Multilayer composite according to one of claims 1 to 10, wherein the functional layer comprises more than 60 wt.% and less than 95 wt.% of a styrene block copolymer based on the total weight of the functional layer. [12] Multilayer composite according to one of claims 1 to 11, wherein the functional layer comprises at least two different styrene block copolymers which differ at least in molecular weight. [13] Multilayer composite according to claim 12, wherein one of the styrene block copolymers has a hardness of 20 to 80 Shore A and a second styrene block copolymer has a hardness of more than 80 Shore A. [14] Multi-layer composite according to one of claims 1 to 13, wherein the multi-layer composite is an artificial leather. [15] Seating furniture comprising a cover made of a multi-layer composite according to one of claims 1 to 14.