An environmentally friendly rubber plasticizer and its preparation method and application

Abstract

The present invention discloses an environmentally friendly rubber plasticizer and a preparation method and application thereof, and belongs to the field of polymer material processing. The preparation method of the rubber plasticizer provided by the present invention comprises mixing plant asphalt and sulfur, heating them for reaction, and then dehydrating them. The preparation method provided by the present invention can obtain an environmentally friendly rubber plasticizer product with relatively cheap raw materials, and the processing technology of the product is relatively simple, the equipment investment is relatively small, and it has a very broad application prospect. The present invention also provides a rubber plasticizer obtained by the above preparation method, and a reclaimed rubber whose preparation raw materials include the above rubber plasticizer.

Description

Technical Field

[0001] The invention relates to the field of polymer material processing, and in particular to an environmentally friendly rubber plasticizer and a preparation method and application thereof. Background Art

[0002] Some two-ring to five-ring polycyclic aromatic hydrocarbons are highly carcinogenic to humans. In the past, the rubber and tire industries used aromatic oils as synthetic and processing oils (plasticizers). Although they had excellent performance, they brought the two-ring to five-ring polycyclic aromatic hydrocarbons contained into rubber products such as tires. These aromatic hydrocarbons are released into the environment during the use of rubber products, or come into close contact with the human body, causing serious environmental and human health hazards. In view of this, relevant foreign industries have stipulated that the content of benzopyrene (BaP) in rubber plasticizers directly put on the market or used to manufacture tires should be less than 1 mg / kg, and the total content of 8 PAHs (polycyclic aromatic hydrocarbons) (BaP, BeP, BaA, CHR, BbFA, BjFA, BkFA and DBAhA) should be less than 10 mg / kg. Domestic regulations state that aromatic oils with a benzopyrene (BaP) content greater than 1 mg / kg and a total content of eight PAHs greater than 10 mg / kg should not be added to tires; Bay The content should not exceed 0.35%. Oils that meet the above technical requirements can be used as environmentally friendly rubber plasticizers. The above regulations have had a significant impact on the upstream and downstream of the tire industry. Among them, the recycled rubber industry, as an important source of raw materials for the tire industry, has also ushered in environmentally friendly technical requirements.

[0003] Recycled rubber is a raw material widely used in the rubber industry. By 2020, the scale of domestic waste tire recycling and environmental protection will reach 8.5 million tons, and the tire retreading rate will reach 8% to 10%, that is, the scale of recycled rubber used through recycling technology will reach about 7.7 million tons. According to the current proportion of 10% to 15% of recycled rubber oil, the special oil for recycled rubber will reach 770,000 to 1.15 million tons. According to relevant regulations, green and environmentally friendly granular recycled rubber will replace the traditional non-environmentally friendly recycled rubber.

[0004] At present, petroleum-based environmentally friendly rubber plasticizers directly used in rubber synthesis and tire manufacturing are already very mature. For example, a related patent discloses a method for producing an aromatic rubber plasticizer, specifically a method for preparing a rubber plasticizer with low condensed aromatic content based on a solvent secondary extraction process; for another example, a patent discloses a method for producing environmentally friendly tire rubber oil by first mixing and then solvent refining; for another example, a related patent discloses a method for producing environmentally friendly tire rubber oil by first mixing and then hydrocracking and hydrorefining. The common feature of the above methods is that distillate oil is used as the main raw material, which has the disadvantages of high raw material prices and long processing flow, resulting in high production costs, and cannot meet the technical requirements of low-cost plasticizers for the recycled rubber industry; at the same time, petroleum-based plasticizers have limited resources and are non-renewable. The industry needs to find a renewable and environmentally friendly recycled rubber plasticizer.

[0005] Therefore, it is very necessary to develop low-cost, renewable and environmentally friendly rubber plasticizers specifically for recycled rubber.

[0006] There are also a small number of related technologies that disclose methods for preparing renewable rubber plasticizers. For example, there is a technology that discloses a method for preparing an environmentally friendly recycled rubber softener made by blending natural olefin / phenolic compounds and animal and plant oils and fats. However, softeners made from natural animal and plant oils and fats contain a large number of unsaturated double bonds, which have poor compatibility with rubber materials and will significantly reduce the mechanical properties and other application properties of recycled rubber. Therefore, there are deficiencies in their use. An ideal recycled rubber plasticizer should not significantly reduce the physical application properties of recycled rubber.

[0007] In summary, the technology for preparing rubber plasticizers using renewable raw materials is still immature, and the obtained plasticizers cannot effectively guarantee the physical application properties of recycled rubber. Summary of the invention

[0008] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides an environmentally friendly rubber plasticizer and a preparation method and application thereof. The preparation method provided by the present invention can obtain an environmentally friendly rubber plasticizer product with relatively cheap raw materials, and the processing technology of the product is relatively simple, the equipment investment is relatively small, and it has a very broad application prospect.

[0009] The invention also provides a rubber plasticizer prepared by the preparation method.

[0010] The invention also provides application of the rubber plasticizer.

[0011] According to an embodiment of the first aspect of the present invention, there is provided a method for preparing an environmentally friendly rubber plasticizer, the method comprising mixing plant asphalt and sulfur, heating them for reaction, and then dehydrating them.

[0012] The reaction mechanism of the preparation method is as follows:

[0013] The main reaction is that sulfur produces free radicals at high temperature, and the sulfur reacts with the unsaturated bonds in the plant asphalt to form carbon-sulfur bonds, which are further cross-linked to form a network structure; the secondary reaction is that the oleic acid molecules in the plant asphalt undergo a dehydration reaction at high temperature to produce acid anhydride.

[0014] The preparation method according to the embodiment of the present invention has at least the following beneficial effects:

[0015] Plant asphalt is the waste after plant oil extraction. After the solid residue is removed again, it is a kind of asphalt-like substance. It is a by-product of oil processing and has a very low selling price. Plant asphalt is mainly composed of ester and oleic acid. The solubility parameter of this component is close to that of rubber. Therefore, it can be used as a raw material for the preparation of rubber plasticizers and has a good plasticizing effect.

[0016] However, the present invention finds that when plant asphalt is directly used as a plasticizer, due to the large amount of unsaturated bonds contained therein, the sulfur used for rubber vulcanization will be converted into free radicals at high temperatures, and will combine with these unsaturated bonds (the plasticizer will compete with the rubber molecules for the vulcanizer) to generate CS bonds, which will reduce the vulcanization effect of the rubber molecules and lead to sulfur deficiency. At the same time, the CS bonds at different positions will be connected to further form a network structure, increase the viscosity of the rubber intermediate, and even produce a highly viscous substance similar to asphalt; and during the high-temperature vulcanization process, the oleic acid in the plant asphalt will undergo a dehydration reaction at high temperatures.

[0017] In the preparation method provided by the present invention, the plant asphalt is vulcanized before being used as a plasticizer to consume the unsaturated bonds, and then vacuum dehydration is performed. Therefore, when the obtained rubber plasticizer is used, the influence of the unsaturated bonds on the rubber vulcanization process can be avoided, and the influence of moisture on the rubber quality can also be avoided.

[0018] In summary, the preparation method provided by the present invention uses plant-based raw materials, which are environmentally friendly and renewable. The obtained rubber plasticizer can be used in the production of environmentally friendly recycled rubber or virgin rubber, which can reduce production costs while ensuring environmental protection, and improve the application performance of the obtained virgin or recycled rubber.

[0019] According to some embodiments of the present invention, the vegetable asphalt is the waste generated during the processing of vegetable oils and fats, also known as vegetable oil feet or oil feet.

[0020] According to some embodiments of the present invention, the sulfur is elemental sulfur produced by the sulfur industry.

[0021] According to some embodiments of the present invention, the mass ratio of the plant asphalt to sulfur is 100:(1-10), for example, it may be about 10:2, 10:3, 10:4, 10:5, 10:6, 10:7, 10:8 or about 10:9.

[0022] The mass ratio of sulfur added will affect the vulcanization effect to a certain extent. If it is lower than the above range, the vulcanization effect is poor, the reaction depth is insufficient, and some unsaturated bonds will remain in the obtained product; if it is higher than the above range, more sulfur will remain and the reaction product will have a bad smell. Within the above range, the performance of the obtained rubber plasticizer can be guaranteed, and the impact of odor on the environment and operators can be avoided.

[0023] According to some embodiments of the present invention, the preparation method further comprises mixing the plant asphalt and sulfur before the heating reaction.

[0024] According to some embodiments of the present invention, the temperature of the heating reaction is 140-240° C. For example, it may be about 150° C., 160° C., 170° C., 180° C., 190° C., 200° C., 210° C., 220° C. or about 230° C.

[0025] The temperature of the heating reaction affects both the reaction rate and the degree of reaction. If the temperature is low, the reaction rate is slow, and if the temperature is too high, there will be more side reactions, which will cause excessive condensation of the plant asphalt itself and the production of hydrogen sulfide. Within the above temperature range, especially in the range of 160 to 170°C, no secondary pollution will be generated, and the overall performance of the resulting rubber plasticizer will be better.

[0026] According to some embodiments of the present invention, the duration of the heating reaction is 0.5 to 3 hours, for example, about 1 hour, 1.5 hours, 2 hours or about 2.5 hours.

[0027] The duration of the heating reaction will affect the depth of the reaction. If the time is short, the reaction will be incomplete, and if the time is long, it will lead to many uncontrollable side reactions and waste energy.

[0028] According to some embodiments of the present invention, the heating reaction is carried out in a stirring state. The purpose of the stirring state is to increase the mass transfer rate. In actual production, the rotation speed can be adjusted according to the production capacity and the performance of the production equipment.

[0029] According to some embodiments of the present invention, the dehydration method comprises vacuum dehydration.

[0030] According to some embodiments of the present invention, the vacuum degree of the vacuum dehydration is 50-100 kPa.

[0031] The vacuum degree of vacuum dehydration will affect the partial pressure of water vapor, that is, the efficiency and effect of dehydration. In principle, the higher the vacuum degree, the better the dehydration effect. However, it is unnecessary to have a high vacuum degree, because a certain amount of water is allowed in the oil product, such as less than 0.03%, which is acceptable to users. In addition, maintaining a high vacuum will waste energy. The above vacuum degree is selected for both dehydration effect and economy.

[0032] According to some embodiments of the present invention, the heating reaction further comprises adding a vulcanization accelerator, thereby promoting sulfur bond opening and increasing the vulcanization speed.

[0033] According to some embodiments of the present invention, the weight ratio of the sulfur to the vulcanization accelerator is 1 to 3:1.

[0034] According to some embodiments of the present invention, the percentage of the vulcanization accelerator in the total mass of the raw materials for preparing the rubber plasticizer is ≤2%, for example, specifically about 1%.

[0035] According to some embodiments of the present invention, the vulcanization accelerator includes at least one of NOBS (CAS: 102-77-2), TMTD (CAS: 137-26-8), DTDM (CAS: 103-34-4) and TBBS (CAS: 95-31-8).

[0036] According to an embodiment of the second aspect of the present invention, a rubber plasticizer prepared by the preparation method is provided.

[0037] Since the rubber plasticizer adopts all the technical solutions of the preparation method of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment.

[0038] According to some embodiments of the present invention, the density of the rubber plasticizer is 0.95-1.20 g / cm 3 For example, it can be about 0.98 g / cm 3 , 1.0g / cm 3 , 1.05g / cm 3 , 1.1g / cm 3 or about 1.15g / cm 3 .

[0039] According to some embodiments of the present invention, in the rubber plasticizer, the content of benzo(a)pyrene (CAS: 50-32-8) is ≤1 mg / kg, and the total content of 8 specific carcinogenic polycyclic aromatic hydrocarbons is ≤10 mg / kg.

[0040] According to some embodiments of the present invention, the eight specific carcinogenic polycyclic aromatic hydrocarbons are BaP (CAS: 50-32-8), BeP (CAS: 192-97-2), BaA (CAS: 56-55-3), CHR (CAS: 218-01-9), BbFA (CAS: 205-99-2), BjFA (CAS: 205-82-3), BkFA (CAS: 207-08-9) and DBA (CAS: 53-70-3).

[0041] According to an embodiment of the third aspect of the present invention, there is provided a reclaimed rubber, wherein the raw materials for preparing the reclaimed rubber include the rubber plasticizer.

[0042] Since the recycled rubber adopts all the technical solutions of the recycled rubber plasticizer of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment. Furthermore, the recycled rubber adopts the rubber plasticizer as the raw material for preparation, which significantly reduces the cost and improves the environmental protection.

[0043] According to some embodiments of the present invention, the properties of the reclaimed rubber meet at least one of the following parameters:

[0044] (1) Tensile strength ≥9 MPa;

[0045] (2) Elongation at break ≥ 300%.

[0046] According to some embodiments of the present invention, the hardness of the reclaimed rubber is ≥ 55 SHA, for example, about 56 SHA or about 58 SHA.

[0047] According to some embodiments of the present invention, the density of the regenerated rubber is 1.18-1.19 g / cm 3 For example, it can be about 1.185 g / cm 3 , 1.186g / cm 3 , 1.187g / cm 3 or about 1.188g / cm 3 .

[0048] According to some embodiments of the present invention, the raw materials for preparing the reclaimed rubber also include rubber powder, carbon black and resin.

[0049] According to some embodiments of the present invention, the mass ratio of the rubber plasticizer to the rubber powder is 1:9-10, for example, about 1:9.5 or about 1:9.6.

[0050] According to some embodiments of the present invention, the mass ratio of the rubber plasticizer to the carbon black is 100:1-3. For example, it may be about 100:1.5 or about 100:2.

[0051] According to some embodiments of the present invention, the mass ratio of the rubber plasticizer to the resin is 10:1 to 3. For example, it may be about 100:1.5 or about 100:2.

[0052] If there is no special explanation, the actual meaning of “about” in the present invention is that the error is allowed to be within the range of ±2%, for example, about 100 is actually 100±2%×100.

[0053] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values ​​2 and 3.

[0054] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0055] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0056] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0057] Specific implementation methods, unless otherwise specified, are all conventional experimental methods, and the materials and reagents used can all be obtained from commercial sources.

[0058] If there is no special description, the kinematic viscosity of the vegetable asphalt at 100°C is 515.7 mm 2 / s, density at 20℃ 0.968g / cm3, refractive index at 20℃ 1.5017; it is a high-viscosity substance with a dark brown to black appearance, obtained from Guangdong Jinkun Industrial Co., Ltd. Other commercially available raw materials with similar properties can also be used to prepare rubber plasticizers with equivalent properties, and the present invention does not make strict limitations.

[0059] Example 1

[0060] This example prepares an environmentally friendly rubber plasticizer, and the specific steps are as follows:

[0061] Put plant asphalt and sulfur into the reactor at the same time, with the weight ratio of the two being 100:1, and mix them;

[0062] The resulting mixture was heated to 240°C and stirred for 0.5 h;

[0063] Finally, the reactor is vacuumed to 50-100 kPa to remove moisture, and the product obtained at the bottom of the reactor is an environmentally friendly rubber plasticizer.

[0064] Among them, effective dehydration can be achieved within the above-mentioned vacuum degree range, and during the dehydration process, the vacuum degree will change with the escape of water. Therefore, in actual production, it is sufficient to maintain it within the above-mentioned range.

[0065] Example 2

[0066] This example prepares an environmentally friendly rubber plasticizer, which differs from Example 1 in that:

[0067] (1) The weight ratio of vegetable asphalt to sulfur is 100:3.

[0068] (2) The heating reaction condition is 200°C / 1h.

[0069] Example 3

[0070] This example prepares an environmentally friendly rubber plasticizer, which differs from Example 1 in that:

[0071] (1) The weight ratio of vegetable asphalt to sulfur is 100:8.

[0072] (2) The heating reaction conditions are 180°C / 2h.

[0073] Example 4

[0074] This example prepares an environmentally friendly rubber plasticizer, which differs from Example 1 in that:

[0075] (1) The weight ratio of vegetable asphalt to sulfur is 100:10.

[0076] (2) The heating reaction conditions are 140°C / 3h.

[0077] Example 5

[0078] This example prepares an environmentally friendly rubber plasticizer, which differs from Example 2 in that:

[0079] (1) The heating reaction conditions are 170°C / 1.5h.

[0080] Example 6

[0081] This example prepares an environmentally friendly rubber plasticizer, which differs from Example 2 in that:

[0082] The weight ratio of vegetable asphalt to sulfur is 100:0.5.

[0083] Example 7

[0084] This example prepares an environmentally friendly rubber plasticizer, which differs from Example 2 in that:

[0085] The weight ratio of vegetable asphalt to sulfur is 100:11.

[0086] Example 8

[0087] This example prepares an environmentally friendly rubber plasticizer, which differs from Example 2 in that:

[0088] The heating reaction condition was 130°C / 1h.

[0089] Example 9

[0090] This example prepares an environmentally friendly rubber plasticizer, which differs from Example 2 in that:

[0091] The heating reaction conditions were 200°C / 0.4h.

[0092] Example 10

[0093] This example prepares an environmentally friendly rubber plasticizer, which differs from Example 2 in that:

[0094] A vulcanization accelerator is added during the heating reaction.

[0095] In this example, the vulcanization accelerator is environmentally friendly and low-toxic TBBS, and the amount used is 1% of the total mass of the heating reaction, which is from Guangzhou Ruiba Chemical Co., Ltd.

[0096] Application Examples

[0097] In this example, a reclaimed rubber is prepared. The specific raw material ratio is shown in Table 1. The specific steps are: pour the rubber plasticizer obtained in the example (the reclaimed rubber is named after the source of the rubber plasticizer) or the plant asphalt used in the example (as a plasticizer, referred to as a control example) into a carburizing tank to become a high-flowing liquid at about 120°C, and then pump it into a seasoning tank. While maintaining a temperature of about 120°C, carbon black, resin and other auxiliary raw materials are added according to the formula provided in Table 1. The mixed material after stirring is pumped into a metering tank, and then into a high-speed mixing tank (high mixing tank) according to a certain proportion. At the same time, the rubber powder prepared in advance is added to the high mixing tank. After high-speed mixing at a temperature of about 120°C for about 5 minutes, it is pressed into a reclaimed rubber dynamic regeneration machine by a high-pressure pump to achieve regeneration of the reclaimed rubber under high temperature and high pressure. The regenerated reclaimed rubber is granulated by a granulator, and after drying, it can be packaged for shipment or further processed.

[0098] Table 1 Recycled rubber formula

[0099] Rubber powder Carbon Black Resin Dosage total 100 0.18 1.9 10.5 112.58

[0100] In Table 1, the model of carbon black is N560; the resin is carbon nine resin, which is Nantong Yangzi (24 mesh full tire) rubber powder.

[0101] Test Case

[0102] In the first aspect of this example, the performance of the rubber plasticizer obtained in the example and the plant asphalt used were tested. The specific test method was: SN / T1877.3-2007. The test results are shown in Table 2.

[0103] Table 2 Physicochemical parameters of rubber plasticizers obtained in some examples

[0104] <![CDATA[Density g / cm 3 > Benzo(a)pyrene content mg / kg 8 carcinogenic polycyclic aromatic hydrocarbons PAHs content mg / kg Vegetable Asphalt 0.968 0.68 9.2 Example 1 0.97 0.48 5.78 Example 2 0.98 0.42 3.61 Example 3 1.05 0.41 4.12 Example 4 1.1 0.52 6.53 Example 5 1.20 0.38 4.52

[0105] Comparison of Examples 1 to 4 shows that with the increase in the amount of sulfur used and the increase in the heating reaction time, the density of the obtained rubber plasticizer is increased to a certain extent, which is due to the increase in the degree of crosslinking caused by sulfur. Comparison of Example 2 and Example 5 further verifies the positive correlation between the duration of the heating reaction and the density. However, no matter how the reaction conditions are changed, the content of benzopyrene and carcinogenic polycyclic aromatic hydrocarbons in the obtained rubber plasticizer will not be affected, ensuring the low cost, environmental protection and renewability of the obtained rubber plasticizer.

[0106] Comparing Example 2 with Examples 6 to 10, it can be seen that the amount of sulfur added in Example 6 is too little, the heating reaction temperature in Example 8 is too low, and the heating reaction time in Example 9 is too short, which directly causes inadequate reaction. More unsaturated double bonds remain in the obtained product. These unsaturated bonds will obviously affect the performance of the later rubber products. However, due to the addition of more sulfur in Example 7, the product has an unpleasant smell, which users do not like. The results obtained in Example 10 are equivalent to those in Example 2, but due to the addition of vulcanization accelerators, the duration of the heating reaction can be shortened to a certain extent in actual production. In the second aspect of this example, the performance of the recycled rubber obtained in the application example was tested. The specific test method is: the hardness is tested according to GB / T 531.1, the tensile strength and elongation at break are tested according to GB / T 528, and the Mooney viscosity is tested according to GB / T 1232.1. The specific results are shown in Table 3.

[0107] Table 3 Test results of some recycled rubber

[0108]

[0109] The results show that, compared with directly using plant asphalt as a plasticizer, the rubber plasticizer prepared by the present invention can significantly improve the tensile strength and elongation at break of the regenerated rubber, that is, improve the application performance of the regenerated rubber.

[0110] Furthermore, the performance of the reclaimed rubber in Examples 1 to 4 is similar to that in Example 5, but in Examples 6 to 10, since the performance of the obtained rubber plasticizer is slightly reduced, the performance of the reclaimed rubber prepared therefrom is also inferior to that of Examples 1 to 5.

[0111] In general, the raw materials for preparing the rubber plasticizer provided by the present invention are widely available and inexpensive, and the obtained recycled rubber has excellent performance and is expected to be widely promoted and used.

[0112] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for preparing an environmentally friendly rubber plasticizer, characterized in that: The preparation method comprises mixing plant asphalt and sulfur, heating and reacting, and then dehydrating; The mass ratio of the plant asphalt to sulfur is 100:(1-10); The temperature of the heating reaction is 140-240°C; Duration: 0.5~3h; The dehydration method includes vacuum dehydration; the vacuum degree of the vacuum dehydration is 50-100 kPa.

2. The preparation method according to claim 1, characterized in that: The heating reaction further comprises adding a vulcanization accelerator; the vulcanization accelerator comprises at least one of NOBS, TMTD and DTDM.

3. A rubber plasticizer prepared by the preparation method according to claim 1 or 2.

4. The rubber plasticizer according to claim 3, characterized in that The density of the rubber plasticizer is 0.95-1.20 g / cm 3 .

5. The rubber plasticizer according to claim 3, characterized in that In the rubber plasticizer, the content of benzo(a)pyrene is ≤1 mg / kg; the total content of 8 specific carcinogenic polycyclic aromatic hydrocarbons is ≤10 mg / kg; the 8 specific carcinogenic polycyclic aromatic hydrocarbons are BaP (CAS: 50-32-8), BeP (CAS: 192-97-2), BaA (CAS: 56-55-3), CHR (CAS: 218-01-9), BbFA (CAS: 205-99-2), BjFA (CAS: 205-82-3), BkFA (CAS: 207-08-9) and DBA (CAS: 53-70-3).

6. A reclaimed rubber, characterized in that: The raw material for preparing the reclaimed rubber includes the rubber plasticizer as described in any one of claims 3 to 5.

7. The reclaimed rubber according to claim 6, characterized in that The properties of the reclaimed rubber meet at least one of the following parameters: (1) Tensile strength ≥ 9 MPa; (2) Elongation at break ≥ 300%.

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