Recoverable flame-retardant commercial coiled material floor and preparation method thereof

Abstract

The invention discloses a recyclable flame-retardant commercial coiled material floor and a preparation method thereof, the coiled material floor comprises 30-50 parts of a thermoplastic elastomer, and the thermoplastic elastomer is composed of a styrene thermoplastic elastomer SEBS, a polyolefin thermoplastic elastomer POE and a polyurethane thermoplastic elastomer TPU according to a weight ratio of (30-50): (10-20): (30-50); 10 to 30 parts of polypropylene; 2 to 10 parts of compatibilizing resin; 10-40 parts of a modified flame retardant; 20-60 parts of an inorganic powder filler; 0.1 to 2 parts of an antioxidant; and 0.5-5 parts of color master batch. A full-thermoplastic formula system is adopted, efficient dispersion of the inorganic filler is achieved through the interface modification effect of the compatibilizing resin, the obtained coiled material has the 100% recoverable characteristic while achieving the mechanical properties (the tensile strength is larger than or equal to 8 MPa, and the tearing strength is larger than or equal to 35 kN / m) of a traditional rubber material, the flame retardance reaches the B1 level, and no VOCs are discharged in the production process.

Description

Technical Field

[0001] This invention belongs to the field of thermoplastic elastomers, specifically relating to a recyclable flame-retardant commercial roll flooring and its preparation method. Background Technology

[0002] Commercial roll flooring is widely used in public places such as shopping malls, hospitals, and schools, as well as industrial plants, due to its convenient installation and wear and impact resistance. Market demand continues to grow. With the increasing global awareness of environmental protection, the recyclability and environmental friendliness of various materials have become core concerns for industry development, and commercial roll flooring is no exception.

[0003] Currently, most commercial roll flooring on the market uses traditional rubber (such as natural rubber and styrene-butadiene rubber) or thermosetting elastomers as the main base material. To meet the requirements for mechanical properties and flame retardancy during use, a large amount of crosslinking agents, small molecule plasticizers, inorganic fillers, and composite flame retardants are usually added. However, this type of traditional roll flooring has significant technical defects: on the one hand, traditional rubber and thermosetting elastomers form a three-dimensional network structure after crosslinking, which cannot be reprocessed and reused by heating and melting. Moreover, the small molecule additives added to the system have poor compatibility with the base material and are difficult to separate. As a result, the discarded roll flooring can only be disposed of by incineration or landfill, which not only wastes resources but also releases harmful gases or pollutes soil and groundwater, resulting in a huge environmental burden. On the other hand, traditional flame retardants added to improve flame retardant performance (such as halogenated flame retardants, simple inorganic flame retardants, etc.) either produce toxic and harmful fumes when burning, endangering human health and the environment, or require high addition amounts to meet flame retardant standards. High addition amounts will seriously damage the mechanical properties of the substrate, causing the tensile strength of roll flooring to drop below 5MPa and the tear strength to be less than 25kN / m, which cannot meet the usage requirements of long-term trampling and handling impacts in commercial scenarios.

[0004] Several related technologies exist concerning methods for preparing roll flooring. For example, patent 202110649172.1 discloses a novel industrial polymer roll flooring and its preparation method. This flooring comprises a UV coating layer, a PVC layer, and a fiber mesh layer. The PVC layer raw materials include polyvinyl chloride resin, calcium carbonate, diisononyl phthalate, etc., and the UV coating contains epoxy acrylate and other components. Its preparation requires multiple steps such as material preparation, mixing, extrusion granulation, etc. Not only are there potential compatibility issues affecting performance due to the large number of raw material components, but the use of diisononyl phthalate plasticizers makes it difficult to separate during recycling, failing to meet environmental protection and recyclability requirements. Furthermore, the UV coating curing process may also generate VOCs. The sound-insulating elastic roll flooring for rail transit and its preparation method proposed in patent 202010910930.6, although it has sound insulation and wear resistance properties, relies on 60 to 150 parts of heavy filler for the sound insulation layer. A large amount of filler will seriously affect the mechanical properties of the material, and the additives may migrate during long-term use, which will affect the stability of performance and is not conducive to the recycling and reuse of materials, and cannot meet the comprehensive needs of commercial scenarios.

[0005] Therefore, developing a commercial roll flooring that combines excellent mechanical properties, high flame retardancy, full life-cycle recyclability, and zero VOC emissions during production has become a key requirement for addressing current industry technical pain points and promoting the green transformation of the commercial flooring industry. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a recyclable flame-retardant commercial roll flooring and its preparation method. This roll flooring exhibits high tensile strength, abrasion resistance, and flame retardancy, while also possessing excellent recyclability. Furthermore, the compatibilizing resin used enables efficient dispersion of inorganic fillers, enhancing component compatibility. The production process is VOCs-free, improving the material's environmental friendliness and processing stability.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A recyclable flame-retardant commercial roll flooring comprises the following components in parts by weight: 30-50 parts of thermoplastic elastomer, 10-30 parts of polypropylene 2-10 parts of compatibilizing resin, 10-40 parts of modified flame retardant, 20-60 parts of inorganic powder filler Antioxidant 0.1-2 parts, 0.5 to 5 parts of color masterbatch.

[0008] Preferably, the thermoplastic elastomer is composed of styrene-based thermoplastic elastomer SEBS, polyolefin-based thermoplastic elastomer POE, and polyurethane-based thermoplastic elastomer TPU in a weight ratio of (30~50):(10~20):(30~50).

[0009] Preferably, the polypropylene melt index is 5~20 g / 10 min (190°C, 2.16 kg).

[0010] Preferably, the compatibilizing resin is one of maleic anhydride-grafted PP, maleic anhydride-grafted POE, and maleic anhydride-grafted SEBS.

[0011] Preferably, the modified flame retardant is obtained by uniformly mixing a long-chain aminosilane modifier and a composite flame retardant in a weight ratio of (3~6):(94~97).

[0012] Preferably, the long-chain aminosilane modifier is prepared by reacting 3-isocyanate-propyltriethoxysilane with decanediamine in a molar ratio of 1:1, and the reaction is carried out under nitrogen protection. More preferably, the reaction is performed by reacting decanediamine with 3-isocyanate-propyltriethoxysilane in the molten state at 70-80°C for 2-3 hours.

[0013] Preferably, the composite flame retardant is prepared by compounding melamine polyphosphate, melamine polyurea, and 3000-mesh aluminum hydroxide in a weight ratio of (30~40):(30~40):(20~30).

[0014] Preferably, the inorganic powder filler is either calcium carbonate or talc.

[0015] Preferably, the antioxidant is a composition of antioxidants 1010, 1076 and antioxidant 168.

[0016] Preferably, the carrier resin of the color masterbatch is polypropylene.

[0017] This invention also provides a method for preparing the above-mentioned recyclable flame-retardant commercial roll flooring, comprising the following steps: (1) The thermoplastic elastomer, polypropylene, compatibilizing resin, modified flame retardant, inorganic powder filler, antioxidant, and color masterbatch are uniformly mixed to obtain a mixture; (2) The mixture is melt-blended, then extruded and shaped to obtain the product. The twin-screw extruder is controlled at 180-190℃. After extrusion through a flat die, it is cooled and shaped in a thermoplastic state by a sizing double roller (temperature 20-40℃, pressure 0.2-0.8MPa) to form a layered structure with both a smooth surface and a rough texture, thus obtaining the recyclable flame-retardant commercial roll flooring.

[0018] Preferably, the mixing in step (1) is performed in a mixer at a speed of 800 to 1000 rpm.

[0019] Preferably, the melt mixing in step (2) is carried out using a twin-screw extruder.

[0020] Preferably, the extrusion temperature in step (2) is 180~190℃.

[0021] Preferably, the shaping conditions described in step (2) are a temperature of 20~40℃ and a pressure of 0.2~0.8MPa.

[0022] Step (2) specifically includes: melting and mixing the mixture through a twin-screw extruder, with the temperature of the twin-screw extruder controlled at 180~190℃, and after extrusion through a flat die, passing it through a sizing double roller in a thermoplastic state, with a sizing temperature of 20~40℃ and a pressure of 0.2~0.8MPa, and cooling and sizing to form a layered structure with both a smooth surface and a rough texture, thus obtaining the recyclable flame-retardant commercial roll flooring.

[0023] The beneficial effects of this invention are as follows: (1) The rubber commercial roll flooring of the present invention uses thermoplastic elastomer as the base material, which is fully recyclable. The three thermoplastic elastomers SEBS, POE and TPU can provide beneficial elasticity, good aging resistance, processing performance and wear resistance. SEBS, POE and TPU work together to make the tensile strength of the resulting roll ≥8MPa and the tear strength ≥35kN / m.

[0024] (2) In this invention, maleic anhydride-grafted PP, maleic anhydride-grafted POE, and maleic anhydride-grafted SEBS are used as compatibilizing resins. On the one hand, they have good compatibility with the non-polar substrates of SEBS and POE. On the other hand, their polar structure is compatible with TPU, which can improve the compatibility between matrix resins of different polarities.

[0025] (3) In order to achieve good flame retardant effect while maintaining beneficial mechanical properties, the modified flame retardant of the present invention is obtained by mixing and reacting a long-chain aminosilane modifier with a composite flame retardant. The long-chain aminosilane modifier is prepared by reacting 3-isocyanate-propyltriethoxysilane with decanediamine in equimolar amounts. The high reactivity of isocyanate groups with amino groups is utilized to generate urethane bonds. At the same time, the silane group at one end of the obtained long-chain aminosilane modifier can combine with the hydroxyl groups on the surface of the composite flame retardant, and the active amino group at the other end can react with the maleic anhydride groups in the compatibilizing resin to generate chemical bonds. In addition, its own long carbon chain structure has good compatibility with the thermoplastic elastomer matrix resin. Under these conditions, the interfacial interaction between the components is enhanced, ensuring good mechanical strength. At the same time, the urethane bonds generated between the bonds of the long-chain aminosilane modifier can form hydrogen bond interactions with each other, and can also form hydrogen bond interactions with the urethane bonds in TPU, further improving the overall mechanical properties. Detailed Implementation

[0026] The present invention will be further illustrated and explained below with reference to preferred embodiments and experimental data.

[0027] Example 1 (1) Under nitrogen protection, equimolar amounts of 3-isocyanate-propyltriethoxysilane and decanediamine were added to the reaction vessel. The decanediamine was first heated to 70°C to melt, and then the temperature was raised to 70°C to react for 2 hours. After cooling, a long-chain aminosilane modifier was obtained.

[0028] (2) Mix 30 parts of melamine polyphosphate, 30 parts of melamine polyurea, and 20 parts of 3000 mesh aluminum hydroxide evenly to obtain a composite flame retardant.

[0029] (3) Mix 3 parts of the long-chain aminosilane modifier obtained in step (1) with 94 parts of the composite flame retardant obtained in step (2) to obtain the modified flame retardant.

[0030] (4) Add 30 parts of thermoplastic elastomer (30 parts of SEBS, 10 parts of POE, 30 parts of TPU), 10 parts of polypropylene with a melt index of 5 g / 10 min, 2 parts of maleic anhydride-grafted PP, 10 parts of the modified flame retardant prepared in step (3), 20 parts of calcium carbonate, 0.1 parts of antioxidant (1010:1076:168=1:1:1), and 0.5 parts of polypropylene carrier masterbatch to a high-speed mixer and mix at 800 rpm for 5 minutes to obtain a mixture.

[0031] (5) The above mixture is melt-blended by a twin-screw extruder (twin-screw temperature 180°C), extruded through a flat die, and then cooled and shaped in a thermoplastic state by a sizing double roller (temperature 20°C, pressure 0.2MPa) to form a layered structure with both a smooth surface and a rough texture, thus obtaining recyclable flame-retardant commercial roll flooring.

[0032] Example 2 (1) Under nitrogen protection, equimolar amounts of 3-isocyanate-propyltriethoxysilane and decanediamine were added to the reaction vessel. The decanediamine was first heated to 70°C to melt, and then the temperature was raised to 75°C to react for 2.5 hours. After cooling, a long-chain aminosilane modifier was obtained.

[0033] (2) Mix 35 parts of melamine polyphosphate, 35 parts of melamine polyurea, and 25 parts of 3000 mesh aluminum hydroxide evenly to obtain a composite flame retardant.

[0034] (3) Mix 4 parts of the long-chain aminosilane modifier obtained in step (1) with 95 parts of the composite flame retardant obtained in step (2) to obtain the modified flame retardant.

[0035] (4) Add 40 parts of thermoplastic elastomer (40 parts of SEBS, 15 parts of POE, 40 parts of TPU), 20 parts of polypropylene with a melt index of 12 g / 10 min, 6 parts of maleic anhydride-grafted POE, 25 parts of the modified flame retardant prepared in step (3), 40 parts of talc, 1 part of antioxidant (1010:1076:168=1:1:1), and 2 parts of polypropylene carrier masterbatch into a high-speed mixer and mix at 900 rpm for 6 minutes to obtain a mixture.

[0036] (5) The above mixture is melt-blended by a twin-screw extruder (twin-screw temperature 185°C), extruded through a flat die, and then cooled and shaped in a thermoplastic state by a sizing double roller (temperature 30°C, pressure 0.5MPa) to form a layered structure with both a smooth surface and a rough texture, thus obtaining recyclable flame-retardant commercial roll flooring.

[0037] Example 3 (1) Under nitrogen protection, equimolar amounts of 3-isocyanate-propyltriethoxysilane and decanediamine were added to the reaction vessel. The decanediamine was first heated to 70°C to melt, and then the temperature was raised to 75°C to react for 2.5 hours. After cooling, a long-chain aminosilane modifier was obtained.

[0038] (2) Mix 38 parts of melamine polyphosphate, 38 parts of melamine polyurea, and 24 parts of 3000 mesh aluminum hydroxide evenly to obtain a composite flame retardant.

[0039] (3) Mix 5 parts of the long-chain aminosilane modifier obtained in step (1) with 96 parts of the composite flame retardant obtained in step (2) to obtain the modified flame retardant.

[0040] (4) Add 45 parts of thermoplastic elastomer (45 parts of SEBS, 18 parts of POE, 45 parts of TPU), 25 parts of polypropylene with a melt index of 18 g / 10 min, 8 parts of maleic anhydride-grafted SEBS, 35 parts of the modified flame retardant prepared in step (3), 50 parts of calcium carbonate, 1.5 parts of antioxidant (1010:1076:168=1:1:1), and 4 parts of polypropylene carrier masterbatch to a high-speed mixer and mix at 950 rpm for 7 minutes to obtain a mixture.

[0041] (5) The above mixture is melt-blended by a twin-screw extruder (twin-screw temperature 188°C), and after being extruded through a flat die, it is cooled and shaped in a thermoplastic state by a sizing double roller (temperature 35°C, pressure 0.7MPa) to form a layered structure with both a smooth surface and a rough texture, thus obtaining recyclable flame-retardant commercial roll flooring.

[0042] Example 4 (1) Under nitrogen protection, equimolar amounts of 3-isocyanate-propyltriethoxysilane and decanediamine were added to the reaction vessel. The decanediamine was first heated to 70°C to melt, and then heated to 80°C to react for 3 hours. After cooling, a long-chain aminosilane modifier was obtained.

[0043] (2) Mix 40 parts of melamine polyphosphate, 40 parts of melamine polyurea, and 30 parts of 3000 mesh aluminum hydroxide evenly to obtain a composite flame retardant.

[0044] (3) Mix 6 parts of the long-chain aminosilane modifier obtained in step (1) with 97 parts of the composite flame retardant obtained in step (2) to obtain the modified flame retardant.

[0045] (4) Add 50 parts of thermoplastic elastomer (50 parts of SEBS, 20 parts of POE, 50 parts of TPU), 30 parts of polypropylene with a melt index of 20 g / 10 min, 10 parts of maleic anhydride-grafted SEBS, 40 parts of the modified flame retardant prepared in step (3), 60 parts of talc, 2 parts of antioxidant (1010:1076:168=1:1:1), and 5 parts of polypropylene carrier masterbatch to a high-speed mixer and mix at 1000 rpm for 8 minutes to obtain a mixture.

[0046] (5) The above mixture is melt-mixed by a twin-screw extruder (twin-screw temperature 190°C), and after being extruded through a flat die, it is cooled and shaped in a thermoplastic state by a sizing double roller (temperature 40°C, pressure 0.8MPa) to form a layered structure with both smooth surface and rough texture, thus obtaining recyclable flame-retardant commercial roll flooring.

[0047] Comparative Example 1 (1) 30 parts of natural rubber (traditional rubber base material), 10 parts of polypropylene, 10 parts of unmodified composite flame retardant (30 parts of melamine polyphosphate + 30 parts of melamine polyurea + 20 parts of aluminum hydroxide), 20 parts of calcium carbonate, 0.1 parts of antioxidant (1010:1076:168=1:1:1) and 0.5 parts of polypropylene carrier masterbatch are poured into a high-speed mixer and mixed at 800 rpm for 5 minutes to obtain a mixture.

[0048] (2) The above mixture is melt-mixed by a twin-screw extruder (twin-screw temperature 180°C), extruded through a flat die, and then cooled and shaped by a sizing twin roller (temperature 20°C, pressure 0.2MPa) to obtain traditional commercial roll flooring.

[0049] Comparative Example 2 (1) Mix 30 parts of melamine polyphosphate, 30 parts of melamine polyurea, and 20 parts of 3000 mesh aluminum hydroxide evenly to prepare a composite flame retardant.

[0050] (2) Take 30 parts of thermoplastic elastomer (30 parts of SEBS, 10 parts of POE, 30 parts of TPU), 10 parts of polypropylene with a melt index of 5 g / 10 min, 2 parts of maleic anhydride-grafted PP, 10 parts of the above composite flame retardant, 20 parts of calcium carbonate, 0.1 parts of antioxidant (1010:1076:168=1:1:1), and 0.5 parts of polypropylene carrier masterbatch, pour them into a high-speed mixer and mix at 800 rpm for 5 minutes to obtain a mixture.

[0051] (3) The mixture is melt-mixed through a twin-screw extruder (twin-screw temperature 180℃), extruded through a flat die, and then cooled and shaped in a thermoplastic state by a sizing double roller (temperature 20℃, pressure 0.2MPa) to obtain roll flooring.

[0052] Note: This comparative example is based on Example 1, except that the long-chain aminosilane modifier is removed and the modified flame retardant is replaced with an equal weight of composite flame retardant. All other formulation components, proportions and preparation processes remain the same.

[0053] Comparative Example 3 (1) Take 25 parts SEBS, 15 parts polypropylene, 30 parts calcium carbonate, 6 parts naphthenic oil, 3 parts maleic anhydride grafted PP, 0.1 parts antioxidant (1010:168=1:1), 1 part silane coupling agent KH550, and 0.5 parts polypropylene carrier masterbatch.

[0054] (2) Put the above raw materials into a high-speed mixer and mix at 800 rpm for 5 minutes to obtain a mixture.

[0055] (3) The mixture is melted and mixed by a twin-screw extruder (temperature 180℃), extruded through a flat die, and then cooled and shaped by a sizing double roller (temperature 20℃, pressure 0.2MPa) to obtain the plastic track sheet for comparison.

[0056] The recyclable flame-retardant commercial roll flooring obtained in Examples 1-4 and Comparative Examples 1-3 were tested for tensile strength, abrasion resistance, flame retardancy, and recyclability. The test results are shown in Table 1. Abrasion resistance was tested according to GB / T17657 standard, using a CS-10 grinding wheel at 1000 revolutions, with a mass loss (g). The smaller the value, the better the abrasion resistance. Recyclability was based on the retention rate of tensile strength after three recycling cycles.

[0057] sample Tensile strength (MPa) Abrasion resistance (g) Flame retardancy Recyclability (%) Example 1 8.2 0.8 B1 92 Example 2 9.5 0.6 B1 95 Example 3 10.1 0.5 B1 94 Example 4 11.3 0.4 B1 96 Comparative Example 1 4.8 2.3 B2 70 Comparative Example 2 6.3 1.5 B2 90 Comparative Example 3 5.7 1.8 \ 88 As shown in Table 1, the samples in Examples 1-4 exhibit superior tensile strength, abrasion resistance, flame retardancy, and recyclability. This demonstrates that the synergistic blending of SEBS, POE, and TPU thermoplastic elastomers, combined with the interfacial modification effect of maleic anhydride-grafted compatibilizers, achieves efficient dispersion of different polarity matrices and inorganic fillers, contributing to improved tensile strength and abrasion resistance. Furthermore, the long-chain aminosilane modifier in the modified flame retardant combines with the hydroxyl groups on the surface of the composite flame retardant via silane groups and reacts with the anhydride groups of the compatibilizer resin. Simultaneously, the long carbon chain structure is well-compatible with the matrix resin, solving the flame retardant agglomeration problem and enhancing molecular chain interactions through hydrogen bonding between urethane bonds. This allows the material to meet the B1 flame retardancy standard while maintaining excellent mechanical properties. The improved recyclability indicates that the all-thermoplastic formulation system used in this invention avoids the limitations of traditional cross-linked structures, allowing for remelting and processing after heating without the addition of difficult-to-separate components such as small-molecule plasticizers, further ensuring performance stability during recycling. The preparation process parameters of Examples 1-4 are similar to those of Comparative Examples 1-3, indicating that the formulation design of the present invention does not increase the processing difficulty, while achieving the environmentally friendly production requirements of zero VOC emissions.

[0058] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A recyclable flame-retardant commercial roll flooring, characterized in that, The components include the following parts by weight: The thermoplastic elastomer comprises 30-50 parts of styrene-based thermoplastic elastomer SEBS, polyolefin-based thermoplastic elastomer POE, and polyurethane-based thermoplastic elastomer TPU in a weight ratio of (30-50):(10-20):(30-50). 10-30 parts of polypropylene 2-10 parts of compatibilizing resin, 10-40 parts of modified flame retardant, 20-60 parts of inorganic powder filler Antioxidant 0.1-2 parts, 0.5 to 5 parts of color masterbatch.

2. The recyclable flame-retardant commercial roll flooring according to claim 1, characterized in that, The compatibilizing resin is one of maleic anhydride-grafted PP, maleic anhydride-grafted POE, or maleic anhydride-grafted SEBS.

3. The recyclable flame-retardant commercial roll flooring according to claim 1, characterized in that, The modified flame retardant is obtained by uniformly mixing a long-chain aminosilane modifier and a composite flame retardant in a weight ratio of (3~6):(94~97).

4. The recyclable flame-retardant commercial roll flooring according to claim 3, characterized in that, The long-chain aminosilane modifier is prepared by reacting 3-isocyanate-propyltriethoxysilane with decanediamine in a molar ratio of 1:

1.

5. The recyclable flame-retardant commercial roll flooring according to claim 3, characterized in that, The composite flame retardant is prepared by compounding melamine polyphosphate, melamine polyurea, and 3000-mesh aluminum hydroxide in a weight ratio of (30~40):(30~40):(20~30).

6. The recyclable flame-retardant commercial roll flooring according to claim 1, characterized in that, The inorganic powder filler is either calcium carbonate or talc.

7. The recyclable flame-retardant commercial roll flooring according to claim 1, characterized in that, The antioxidant is a combination of antioxidants 1010, 1076 and antioxidant 168.

8. The recyclable flame-retardant commercial roll flooring according to claim 1, characterized in that, The carrier resin of the masterbatch is polypropylene.

9. The method for preparing recyclable flame-retardant commercial roll flooring according to any one of claims 1-8, characterized in that, Includes the following steps: (1) The thermoplastic elastomer, polypropylene, compatibilizing resin, modified flame retardant, inorganic powder filler, antioxidant, and color masterbatch are uniformly mixed to obtain a mixture; (2) The mixture is melt-blended, then extruded and shaped to obtain the product. The twin-screw extruder is controlled at 180-190℃. After extrusion through a flat die, it is cooled and shaped in a thermoplastic state by a sizing double roller (temperature 20-40℃, pressure 0.2-0.8MPa) to form a layered structure with both a smooth surface and a rough texture, thus obtaining the recyclable flame-retardant commercial roll flooring.

10. The preparation method according to claim 9, characterized in that, The extrusion temperature mentioned in step (2) is 180~190℃.