Low temperature flex resistant tpo composition and tpo artificial leather containing the same

Abstract

The present application relates to a low-temperature folding-resistant TPO composition, comprising: 15-30 parts by weight of PP, 5-15 parts by weight of a propylene-based elastomer, and 55-80 parts by weight of another elastomer, wherein the total weight of the PP, the propylene-based elastomer and the other elastomer is 100 parts by weight. The present application also relates to a TPO artificial leather comprising a TPO skin layer formed from the TPO composition. The TPO composition and the corresponding artificial leather obtained according to the present application have both excellent room-temperature folding resistance and good low-temperature folding resistance.

Description

Technical Field

[0001] This invention relates to a low-temperature flexural strength thermoplastic polyolefin elastomer (also known as TPO) composition, and TPO artificial leather made from the TPO composition. Background Technology

[0002] Various types of artificial leather, such as polyvinyl chloride (PVC), polyurethane (PU), and TPO, are widely used in automotive interiors for materials like seats and gear shift levers. Cars may experience extremely low temperatures during use; for example, in winter, temperatures in countries like Russia, Canada, and Finland can drop to -50°C, and in northern China, temperatures can drop to -30°C. While tires, engine oil, and antifreeze can be switched to winter-specific versions to cope with these extreme winter temperatures, it's not convenient to switch the leather used in areas like seats and gear shift levers.

[0003] During use, the leather used in parts such as seats and gear shifters is constantly undergoing a dynamic flexing process, making it prone to surface cracking. The leather is more susceptible to cracking at low temperatures, and this cracking becomes more pronounced at lower temperatures. Currently, the PVC, PU, ​​and TPO materials used in seats and gear shifters on the market struggle to meet increasingly stringent requirements for flexural crack resistance. They often only pass the Bally Flex test at room temperature (without cracking), but their crack resistance at extremely low temperatures is very poor (cracking occurs).

[0004] Therefore, it is urgent to develop an interior artificial leather material that can maintain good wrinkle resistance even at ultra-low temperatures. Summary of the Invention

[0005] Based on the aforementioned prior art, the object of the present invention is to provide a TPO composition with low-temperature flexural strength, and a TPO artificial leather made from the TPO composition. The TPO composition and the corresponding artificial leather obtained according to the present invention possess both excellent room-temperature flexural strength and good low-temperature flexural strength.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a TPO composition comprising:

[0007] 15 to 30 parts by weight, such as 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, 30 parts by weight, or any range between these values, of polypropylene (PP).

[0008] 5 to 15 parts by weight, such as 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, or any range between these values, of a propylene-based elastomer, and

[0009] 55 to 80 parts by weight, such as 55 parts by weight, 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, 80 parts by weight, or other elastomers within any two of these values.

[0010] The total weight of PP, acrylic elastomer and other elastomers is 100 parts by weight.

[0011] The propylene-based elastomer used in this invention is a semi-crystalline propylene-ethylene copolymer generated under the action of a metallocene catalyst. The proportion of propylene in the ethylene molecular chain is adjusted by the action of the metallocene, reducing the crystallinity of the molecules. In the propylene-based elastomer used in this invention, propylene is the main component, with only a small amount of ethylene, unlike ethylene-propylene copolymers where ethylene is the main component. According to this invention, adding such a propylene-based elastomer to the TPO composition serves two purposes: firstly, it improves flexibility; secondly, the amount of propylene-based elastomer added is crucial for simultaneously satisfying flexural strength at both room temperature and low temperature. Less propylene-based elastomer results in poorer flexural strength (Bally Flex measured according to ISO 5402) at both room temperature and low temperature; however, excessive addition leads to excessive material flowability, resulting in poor processability and even difficulty in processing. Particularly good material properties are obtained when the content of propylene-based elastomer is around 10 parts by weight; therefore, the content of propylene-based elastomer is more preferably 6 to 14 parts by weight.

[0012] Additionally, choosing PP as the polyolefin resin for addition to TPO compositions helps improve strength. Adding other elastomers helps improve processability, and can enhance the material's toughness, tensile properties, softness, and / or hand feel, depending on requirements. If only propylene-based elastomers are used without adding other elastomers, the processing flow may be too high, leading to poor film stability or even difficulty in film formation.

[0013] To achieve better material compatibility and thus improve material and processing performance, according to a preferred embodiment of the invention, the other elastomer is nonpolar and has a Shore A hardness of 40 to 80 (measured according to ASTM D2240). More preferably, the other elastomer is an olefin-based thermoplastic elastomer.

[0014] According to a preferred embodiment of the invention, based on a total weight of 100 parts by weight of PP, a propylene-based elastomer, and other elastomers, the other elastomers comprise 15 to 45 parts by weight, for example, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight, or any range between these values, of a polyolefin elastomer (POE). POE is a copolymer of ethylene and an α-olefin, wherein the polymerized linear polyethylene (PE) acts as the hard segment, and the α-olefin forms the branched soft segment. The α-olefin chain length is generally C4, C6, or C8. An important improvement of the invention is the co-addition of the propylene-based elastomer and POE to the TPO composition. On the one hand, POE improves the flexibility of the product and enhances the processability of the blended material compared to adding only propylene-based elastomers. On the other hand, compared to adding only POE, propylene-based elastomers lower the glass transition temperature of the material, allowing it to maintain a certain degree of elasticity even at extremely low temperatures, thereby ensuring flexural strength at extremely low temperatures (Bally Flex as measured according to ISO 5402). In other words, by combining propylene-based elastomers and POE, the product can simultaneously meet the desired flexibility and flexural strength at both room temperature and low temperatures.

[0015] According to a preferred embodiment of the invention, the total weight of PP, propylene-based elastomer, and other elastomers is 100 parts by weight, wherein the other elastomers comprise 25 to 45 parts by weight, for example, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight, or any range between these values, of thermoplastic dynamically vulcanized rubber (TPV). TPV is obtained by vulcanizing conventional EPDM and adding PP, which can further effectively improve the toughness of the material and facilitate film formation. TPV is classified into oil-extended TPV and non-oil-extended TPV. The present invention prefers oil-extended TPV because EPDM and PP have better compatibility in oil-extended TPV, where the PP, as a marine phase, forms a good blend with the EPDM island phase, dynamically vulcanizing during extrusion to form a particulate microstructure.

[0016] According to a preferred embodiment of the present invention, based on a total weight of 100 parts by weight of PP, propylene-based elastomer, and other elastomers, the TPO composition further contains 1 to 5 parts by weight of additives. Conventional materials well known to those skilled in the art can be selected as additives as needed, such as light stabilizers, color masterbatches, antioxidants, flame retardants, etc.

[0017] According to a preferred embodiment of the present invention, in the molecular chain of the propylene-based elastomer, the propylene monomer accounts for 70%-90% and the ethylene monomer accounts for 10-30%. Preferably, the propylene monomer accounts for 80%-90% and the ethylene monomer accounts for 10-20%. Preferably, the polymers of propylene and ethylene are block-integrated into the isotactic polypropylene chain. This allows for better utilization of the beneficial effect of the propylene-based elastomer on the low-temperature flexural strength of the TPO composition.

[0018] To achieve the technical objective described at the beginning, the present invention also proposes a TPO artificial leather comprising a TPO epidermal layer formed from the TPO composition according to the present invention.

[0019] In this invention, all the features and corresponding effects of the aforementioned TPO composition apply to the TPO epidermal layer formed by the TPO composition, and will not be described again here.

[0020] According to a preferred embodiment of the invention, a base fabric is provided beneath the TPO outer layer. Here, "below" refers to the side of the artificial leather that faces away from the user during use.

[0021] In principle, the TPO skin layer and the base fabric can be bonded together either by hot pressing or by adhesive. Preferably, the TPO skin layer and the base fabric are bonded together by hot pressing. Because a acrylic elastomer is added to the TPO skin layer, its viscosity at high temperatures is increased, which facilitates high-temperature heat bonding. This significantly enhances the adhesion between the TPO skin layer and the base fabric, requiring less pressure and ensuring the regularity of the skin.

[0022] According to a preferred embodiment of the present invention, a paint layer is provided above the TPO outer layer. "Above" here refers to the side of the artificial leather facing the user during use. Conventional paints known in the art can be used for surface coating. In this invention, waterborne polyurethane paint is preferred. The waterborne polyurethane paint, with a total weight of 100 parts by weight, comprises 70-80 parts by weight of waterborne polyurethane modified resin and 8-20 parts by weight of additives. Surface treatment by printing paint onto the TPO material surface can advantageously improve the gloss, feel, and light resistance, heat resistance, dirt resistance, abrasion resistance, scratch resistance, and other functional properties of the TPO artificial leather surface.

[0023] To prepare the TPO artificial leather according to the present invention, a preparation method comprising the following steps can be used:

[0024] A) PP, acrylic elastomer, other elastomers (such as POE and TPV) and other additives are heated, melted, mixed evenly, and extruded to obtain TPO skin layer;

[0025] B) Apply a paint layer, preferably based on a waterborne polyurethane system, to one side of the TPO skin layer;

[0026] C) The TPO skin layer is hot-pressed and laminated with the base fabric.

[0027] The various raw materials for the TPO skin layer can be mixed and coated in a conventional manner. Preferably, the various raw materials are mixed and extruded into a film in an extruder, preferably a twin-screw extruder.

[0028] In this invention, all the characteristics and corresponding effects of the aforementioned TPO composition and the corresponding TPO artificial leather are applicable to the method of manufacturing the TPO artificial leather, and will not be described again here.

[0029] The low-temperature flexural strength TPO artificial leather described in this invention can be used in automotive interiors, especially in areas such as seats and gear shift levers.

[0030] The advantages of this invention are:

[0031] The TPO formulation of the present invention improves the performance of TPO materials both at room temperature and at low and even ultra-low temperatures. The TPO material obtained according to the present invention maintains good flexibility and flexural strength even at ultra-low temperatures (according to ISO standards).

[0032] (Bally Flex as measured by ISO 5402). According to ISO 5402, conventional synthetic leather materials on the market can achieve 100,000 flexural cycles at a normal temperature of 23°C, but only 30,000 cycles at a low temperature of -20°C. In contrast, the TPO synthetic leather obtained according to this invention can maintain at least 100,000 flexural cycles, and even up to 150,000 cycles, at a temperature of 22°C ± 3°C. At the same time, it can achieve at least 100,000 flexural cycles at a temperature of -30°C ± 3°C, and even at a lower temperature of -50°C ± 3°C, it can achieve at least 40,000 flexural cycles.

[0033] Meanwhile, compared with traditional TPO surface formulations, the TPO material obtained according to the present invention has improved softness and toughness, as well as better processability and feel.

[0034] The adhesion between the TPO skin and the base fabric is also improved in a more optimized way. Conventionally, this is achieved by increasing temperature and pressure, or by adding adhesives / films, which not only increases costs but also leads to performance degradation of the skin under high temperature and pressure. This invention optimizes this problem by incorporating a acrylic elastomer. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments and comparative examples. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Examples 1-3:

[0037] TPO artificial leather is prepared according to the following method:

[0038] The first step involves adding polyolefin resins PP, POE, TPV, propylene-based elastomer, and other additives to a twin-screw extruder according to the TPO skin layer formulation in Table 1. The components are then heated and melted at 200°C until homogeneous. The resulting mixture is then extruded to prepare a 0.5 mm thick TPO skin layer.

[0039] The second step is to uniformly coat one side of the TPO skin layer with a water-based polyurethane system paint with a thickness of about 0.2μm using gravure printing to improve the surface feel and wear and scratch resistance.

[0040] The third step involves directly hot-pressing the obtained TPO outer layer with the base fabric at 180°C on an embossing machine to create a finished TPO artificial leather product in one step. This gives the final TPO outer layer the same appearance, texture, and feel as genuine leather. No external adhesives are added during the hot-pressing process.

[0041] Step 4: Cut the finished product according to the customer's requirements.

[0042] The properties of the TPO synthetic leather obtained were tested. The flexural strength was measured according to ISO 5402 at 23°C, -30°C, and -50°C. The flexibility was measured according to GMW 3390, and the tensile strength was measured according to GMW 3010. The test results are shown in Table 2.

[0043] Table 1: Formulation of TPO epidermal layer (unit: parts by weight)

[0044] PP a propylene-based elastomer ​ b TPV ​ c POE ​ Additives Example 1 20 10 30 40 2 Example 2 16 6 38 40 2 Example 3 30 14 30 26 2 Comparative Example 1 20 - 30 50 2 Comparative Example 2 20 20 30 30 2 Comparative Example 3 30 10 - 60 2 Comparative Example 4 30 10 60 - 2

[0045] a Propylene-based elastomer: purchased from ExxonMobil, of which propylene monomers account for 85% and ethylene monomers account for 15%;

[0046] bTPV: Shore A hardness is 73 as measured by ASTM D2240;

[0047] c POE: Shore A hardness is 51 as measured according to ASTM D2240.

[0048] Table 2: Properties of the obtained TPO artificial leather

[0049]

[0050] Comparative Examples 1-4:

[0051] TPO artificial leather was prepared according to the TPO epidermal layer formulation in Table 1, using the same methods as in Examples 1-3. The flexural strength, flexibility, and tensile strength of the obtained TPO artificial leather were tested using the same testing methods as in Examples 1-3, and the test results are shown in Table 2.

[0052] Compared with Example 1, Comparative Example 1 did not add propylene-based elastomer, but instead increased the POE content, which resulted in a decrease in the flexibility of the material and a significant decrease in its flexural strength at both room temperature and low temperature.

[0053] Compared with Example 1, the content of propylene-based elastomer in Comparative Example 2 was too high, which resulted in poor processing performance of the material mixture, poor film-forming properties, and inability to extrude TPO leather finished products, thus making it impossible to test the various properties of the corresponding artificial leather.

[0054] Compared to Example 1, the formulation of Comparative Example 3 does not contain TPV, while the amounts of POE and PP are increased accordingly, especially the POE content is too high. Due to the large difference in melting points between PP and POE, the system compatibility deteriorates, film-forming properties are poor, and TPO leather products cannot be extruded, thus making it impossible to test the various properties of the corresponding artificial leather.

[0055] Compared to Example 1, Comparative Example 4 did not contain POE; instead, it used only TPV and a propylene-based elastomer as elastomers, thus increasing the content of PP and TPV accordingly. Compared to the case of the present invention, which uses a combination of POE and a propylene-based elastomer, the material obtained from Comparative Example 4 exhibited decreased flexibility and significantly reduced flexural strength.

[0056] Comparative Example 5:

[0057] The following TPO epidermal layer formulation is used:

[0058] 20 parts by weight of PP;

[0059] 10 parts by weight of ethylene-propylene elastomer (85% ethylene monomer, 10.1% propylene monomer, and 4.9% third monomer);

[0060] 30 parts by weight of TPV (Shore A hardness of 73);

[0061] 40 parts by weight of POE (Shore A hardness of 51);

[0062] Two parts by weight of the additive,

[0063] TPO artificial leather was prepared using the same method as in Examples 1-3.

[0064] Compared to Example 1, Comparative Example 5 used an ethylene-propylene elastomer with a larger amount of ethylene monomers. The resulting artificial leather had a flexibility of 120 mm as measured by GMW 3390, which was significantly worse than the artificial leather obtained in Example 1 of this invention. Based on the significantly worsened flexibility and increased hardness, it can be concluded without further testing that the flexural strength of the artificial leather is correspondingly severely adversely affected.

[0065] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A low-temperature flexural strength TPO composition, said TPO composition comprising: 15 to 30 parts by weight of PP, 5 to 15 parts by weight of propylene-based elastomer, and 55 to 80 parts by weight of other elastomers, said other elastomers comprising 15 to 45 parts by weight of POE, The total weight of the PP, propylene-based elastomer and other elastomers is 100 parts by weight.

2. The TPO composition according to claim 1, characterized in that, The other elastomers are nonpolar and have a Shore A hardness of 40 to 80.

3. The TPO composition according to claim 1, characterized in that, The other elastomers are olefin-based thermoplastic elastomers.

4. The TPO composition according to any one of claims 1 to 3, characterized in that, The other elastomers comprise 25 to 45 parts by weight of TPV.

5. The TPO composition according to claim 4, characterized in that, The TPV is an oil-filled TPV.

6. The TPO composition according to any one of claims 1 to 3, characterized in that, The propylene-based elastomer is a semi-crystalline propylene-ethylene copolymer generated under the action of a metallocene catalyst.

7. The TPO composition according to claim 6, characterized in that, In the molecular chain of the propylene-based elastomer, propylene monomers account for 70%-90% and ethylene monomers account for 10-30%.

8. The TPO composition according to claim 7, characterized in that, In the molecular chain of the propylene-based elastomer, propylene monomers account for 80%-90% and ethylene monomers account for 10-20%.

9. A TPO artificial leather comprising a TPO epidermal layer formed from a TPO composition according to any one of claims 1 to 8.

10. The TPO artificial leather according to claim 9, characterized in that, A base fabric is provided beneath the TPO skin layer.

11. The TPO artificial leather according to claim 9 or 10, characterized in that, According to ISO 5402, the TPO artificial leather has a flexural strength of 100,000 cycles at 22℃±3℃ and 100,000 cycles at -30℃±3℃.

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