Process for the preparation of aliphatic sulfonate surfactants from polypropylene, polyethylene or mixed plastics

Abstract

The present application relates to the technical field of upgrading and recycling of waste plastics, and in particular to a method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene or mixed plastics thereof. The method mainly comprises: first, degrading the waste plastics into terminal alkenyl polymer wax by a chemical pyrolysis method, then performing a sulfonation reaction on the terminal alkenyl polymer wax, and synthesizing aliphatic sulfonate surfactants; the waste plastics are selected from polypropylene, polyethylene or a mixture of the two. The aliphatic sulfonate surfactants obtained by the method have similar surface tension, foaming capacity and washing capacity to commercial surfactants of the same type, and the washing effect is better than that of standard laundry detergent. The method of the present application involves pyrolysis-sulfonation, and the process is simple, suitable for large-scale production, realizes the secondary utilization of waste plastics, and turns waste into treasure.

Description

Technical Field

[0001] This invention relates to the field of waste plastic upgrading and recycling technology, specifically to a method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both. Background Technology

[0002] Polyethylene and polypropylene are the two most widely used types of plastics, contributing about 60% of the annual plastic demand. They are mainly used as single-use packaging materials, such as outer packaging for various daily, agricultural, and industrial products, including food, agricultural products, and chemical products. These packaging materials are discarded as plastic waste after reaching their service life or becoming contaminated to a certain extent. This type of waste plastic is difficult to recycle, has a low recycling rate, and the global annual recycling rate is only 10%.

[0003] Compared to traditional mechanical recycling, chemical upgrading recycling, also known as "converting waste plastics into high-value products," is considered one solution. For the upgrading recycling of polyethylene and polypropylene, existing recycling technologies mainly convert polyethylene and polypropylene waste into fuels such as diesel and polymer waxes. These products have lower purity and performance than commercial products, resulting in a limited market and low value, low recycling returns, and limited prospects for large-scale application. Developing higher-value derivatives from waste plastics is therefore crucial. Considering the structural characteristics of these two polymers—long aliphatic chain structures with aliphatic branches—aliphatic derivatives are more suitable for the upgrading recycling of polyethylene and polypropylene.

[0004] Surfactants are substances that can significantly alter the interfacial state of a solution system. Adding even a small amount can significantly reduce the surface tension of a solution. They have wide applications in washing, agriculture, environmental protection, medicine, petroleum processing, and mining, playing a vital role in improving production processes, reducing costs, and saving energy. They are often referred to as "industrial MSG" and "industrial catalysts." In 2022, the domestic surfactant market in my country reached 4.2 million tons per year, with anionic surfactants accounting for approximately 40%. Among the many anionic surfactants, aliphatic sulfonates are a very important class; however, methods for preparing aliphatic sulfonate anionic surfactants from polyethylene and polypropylene are still lacking. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both. This method mainly includes: firstly, degrading waste plastics into terminal alkenyl polymer waxes using chemical pyrolysis; then, subjecting the terminal alkenyl polymer waxes to sulfonation, during which the terminal olefins undergo sulfonation to obtain sulfonic acid groups; and finally, reacting the sulfonic acid groups to prepare the aliphatic sulfonate surfactant. The waste plastics are selected from polypropylene, polyethylene, or a mixture of both. The aliphatic sulfonate surfactant obtained by this method has surface tension, foaming ability, and detergency similar to other surfactants of the same type, and its detergency is superior to commercially available detergents.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both plastics includes the following steps:

[0008] Under inert atmosphere conditions, plastic is ground into powder and then pyrolyzed. During pyrolysis, the carbon-carbon bonds of the polymer chain break, yielding terminal alkenyl polymer wax.

[0009] The plastic is selected from polypropylene, polyethylene, or a mixture of the two in any proportion;

[0010] After cooling the terminal olefin polymer wax at 0-5℃ for 0.5-1h, it is reacted with a sulfonating agent for 0.5-2h. At this time, the terminal olefin is sulfonated to obtain sulfonic acid groups. Then, the temperature is raised to room temperature and aged at room temperature for 0.5-2h. The aging process achieves complete reaction and yields sulfonic acid products.

[0011] An alkali is added to the sulfonic acid product and a reaction is carried out. The purpose of the reaction is to obtain sulfonates, which are then dried to obtain aliphatic sulfonate surfactants.

[0012] Preferably, the plastic is selected from waste or unused polypropylene or polyethylene. Reusing waste polypropylene or polyethylene not only helps to reduce the sorting process of polyethylene and polypropylene plastics, but also realizes waste utilization and turns waste into treasure.

[0013] Preferably, the pyrolysis conditions are: pyrolysis at 200-400℃ for 4-16 hours, under which the plastic is cracked and terminal alkenyl groups are obtained.

[0014] Preferably, the pyrolysis process can also be carried out under catalytic conditions, wherein the catalyst is selected from alkali metal oxides or transition metal oxides of Group I to Group III; furthermore, the catalyst is selected from non-ferrous metal oxides, and studies have found that non-ferrous metal oxides have better catalytic performance. The catalyst accelerates the pyrolysis of plastics and reduces the pyrolysis time.

[0015] During the pyrolysis process, the mass percentage of catalyst to plastic is 0.1-20 wt.%; further, the mass percentage of catalyst to plastic is 20 wt.%.

[0016] Preferably, the inert atmosphere of the pyrolysis process is a nitrogen, argon, helium, carbon dioxide or carbon monoxide atmosphere with an oxygen content of less than 10 vol.%; the presence of oxygen will reduce the yield and produce other oxygen-containing groups.

[0017] Preferably, the molecular weight of the terminal alkenyl polymer wax is 50-2000.

[0018] Preferably, the sulfonating agent is a liquid sulfonating agent or a gaseous sulfonating agent, and two sulfonating agents can be used to carry out the sulfonation reaction;

[0019] The liquid sulfonating agent is composed of chlorosulfonic acid and a slow-release agent. Comparative studies have shown that the sulfonating agent containing only chlorosulfonic acid without a slow-release agent has poor sulfonating performance. The slow-release agent is used to slow down the excessively fast local reaction rate. Adding a slow-release agent to ensure that the reaction proceeds slowly and evenly helps to improve the product properties.

[0020] The gaseous sulfonating agent is a mixed gas containing SO3;

[0021] The molar ratio of chlorosulfonic acid or SO3 to the olefinic polypropylene wax is 1-3:1.

[0022] Preferably, the sustained-release agent is selected from 1,4-dioxane, 1,3-dioxane, 1,2-dioxane, and substituted dioxane, wherein the substituent in the substituted dioxane is selected from pyridine, alkyl with 1-20 carbon atoms, aromatic with 5-30 carbon atoms, halogen, hydroxyl, carboxyl, sulfonic acid, or sulfate ester; and the molar ratio of chlorosulfonic acid to the sustained-release agent is 1:0.5-3.

[0023] Preferably, the SO3 mixture is a mixture of SO3 and dilution gas, with the SO3 volume percentage being 3-20 vol.%. Studies have shown that the SO3 volume percentage in the SO3 mixture should not be less than 3 vol.%.

[0024] The diluent gas is selected from air, nitrogen, argon, helium, carbon dioxide, or carbon monoxide.

[0025] Preferably, the base reacting with the sulfonic acid product is selected from one or more of potassium hydroxide, potassium bicarbonate, potassium carbonate, sodium hydroxide, sodium bicarbonate, and sodium carbonate; and the reaction proceeds to a pH of 7-9 after the addition of the base.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. In addition to being applicable to single polyethylene or polypropylene plastics, the method of the present invention can also process mixed plastics of polyethylene and polypropylene, and is applicable to mixed plastics of any proportion, which helps to reduce the sorting process of polyethylene and polypropylene plastics; at the same time, the method of the present invention can convert waste polyethylene and polypropylene plastics into highly active sulfonate surfactants, whose surface tension, foaming effect and washing effect are similar to those of commercial surfactants of the same type, and the products have the advantages of low cost, good performance and high value.

[0028] 2. The method of the present invention involves two steps: pyrolysis of polymer plastics into terminal alkenyl polymer wax and sulfonation of polymer wax. The process is simple, suitable for large-scale application, and realizes the transformation of waste into treasure.

[0029] 3. This invention provides a method for preparing aliphatic sulfonate surfactants from waste polyethylene and / or polypropylene plastics. The properties of the aliphatic sulfonate surfactants, such as surface tension, foaming ability, and washing effect, are comparable to those of commercial surfactants of the same type, such as dodecyl sulfate. In addition, the mass conversion rate of waste plastics to surfactants in this method is as high as 85%, which has extremely broad application prospects. Attached Figure Description

[0030] Figure 1 This is a reaction diagram for preparing aliphatic sulfonate surfactants from polypropylene plastic in Example 1.

[0031] Figure 2 This is the gas chromatogram of the terminal alkenyl polypropylene wax in Example 1.

[0032] Figure 3 The terminal alkenyl polypropylene wax in Example 1 1 H NMR spectrum.

[0033] Figure 4 The aliphatic sulfonate surfactant in Example 1 1 H NMR spectrum.

[0034] Figure 5 The infrared spectra of the aliphatic sulfonate surfactant (polypropylene plastic-derived sulfonate as shown in the figure) and the terminal alkenyl polypropylene wax (polypropylene plastic-derived wax as shown in the figure) in Example 1 are shown.

[0035] Figure 6 The image shows the 2p photoelectron spectra of sulfur in the aliphatic sulfonate surfactant (polypropylene plastic-derived sulfonate as shown in the figure), the terminal alkenyl polypropylene wax (polypropylene plastic-derived wax as shown in the figure), and sodium dodecyl sulfonate in Example 1.

[0036] Figure 7The surface tension diagram is shown for the aliphatic sulfonate surfactant (the polypropylene plastic-derived sulfonate shown in the figure) and sodium dodecyl sulfonate in Example 1.

[0037] Figure 8 The image shows the foaming effect of aliphatic sulfonate surfactant (polypropylene plastic-derived sulfonate) and sodium dodecyl sulfonate in Example 1.

[0038] Figure 9 The graph shows the detergency of aliphatic sulfonate surfactants (polypropylene plastic-derived sulfonates) and sodium dodecyl sulfonate compared to standard laundry detergent in Example 1.

[0039] Figure 10 The graph shows the detergency of aliphatic sulfonate surfactants (polyethylene plastic-derived sulfonates) and sodium dodecyl sulfonate compared to standard laundry detergent in Example 2.

[0040] Figure 11 The graph shows the detergency of aliphatic sulfonate surfactants (polypropylene-polyethylene mixed plastic derived sulfonates) and sodium dodecyl sulfonate compared to standard laundry detergent in Example 3.

[0041] Figure 12 The graph shows the detergency of aliphatic sulfonate surfactants (polypropylene plastic-derived sulfonates) and sodium dodecyl sulfonate compared to standard laundry detergent in Example 6.

[0042] Figure 13 The graph shows the detergency of aliphatic sulfonate surfactants (polypropylene plastic-derived sulfonates) and sodium dodecyl sulfonate compared to standard laundry detergent in Comparative Example 1.

[0043] Figure 14 The graph shows the detergency of aliphatic sulfonate surfactants (polypropylene plastic-derived sulfonates) and sodium dodecyl sulfonate compared to standard laundry detergent in Comparative Example 2. Detailed Implementation

[0044] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0045] Unless otherwise specified, the experimental and testing methods described below are conventional methods; unless otherwise specified, the reagents and raw materials described below are commercially available.

[0046] The waste polyethylene and polypropylene plastics that can be processed by the method of this invention refer to waste generated in daily life and production, including contaminated polyethylene and polypropylene raw materials or products. Contamination includes, but is not limited to, food scraps, kitchen waste, garden waste, dust, and detergents. Polyethylene plastics include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and ultra-high molecular weight polyethylene (UHDPE); polypropylene plastics include atactic polypropylene, syndiotactic polypropylene, isotactic polypropylene, and copolymer polypropylene. In other words, currently commonly used polyethylene and polypropylene plastics can be recycled and processed by this application.

[0047] This application uses polyethylene, polypropylene, or a mixture thereof as raw materials. First, chemical pyrolysis is performed to break the carbon-carbon bonds of the polymer chain and expose the terminal alkenyl groups to obtain a terminal alkenyl polymer wax. Then, the terminal alkenyl polymer wax is sulfonated to obtain sulfonic acid groups. Finally, an alkali is used to react and obtain an aliphatic sulfonate surfactant. This application provides for the first time a method for preparing aliphatic sulfonate anionic surfactants using polyethylene and polypropylene as raw materials.

[0048] The following embodiments are provided to further illustrate the technical solution of this application:

[0049] Example 1

[0050] A method for preparing aliphatic sulfonate surfactants from polypropylene plastic includes the following steps:

[0051] (1) Waste polypropylene was mechanically ground into powder with a particle size of less than 5 mm using a plastic machine. 10 g of powder was added to a flask in a glove box filled with N2. The flask was sealed with a vacuum stopper and flask clamps and then removed from the glove box. The flask containing polypropylene powder was then transferred to a high-temperature electric heating mantle and heated to 360°C at a heating rate of 10°C / min. After the reactor reached the set temperature, the polymer waste began to decompose. The reaction was maintained for 12 h and then gradually cooled to room temperature to obtain end-alkenyl polypropylene wax with a yield of 91 wt.%.

[0052] (2) In the sulfonation upgrade step, the sulfonation product is obtained by reacting terminal alkenyl polypropylene wax with SO3 gas; 2g of terminal alkenyl polypropylene wax from step (1) is added to a round-bottom flask and the flask is placed in an ice bath at 0°C to cool for 30min. Then, a mixture of SO3 and air is introduced into the round-bottom flask. After the reaction continues for 30min, the gas is stopped and the temperature is raised to room temperature. After aging at room temperature for 30min, the reaction is ended and the reactor is purged with dry air to remove residual SO3 and obtain sulfonic acid product.

[0053] The volume percentage of SO3 is 8 vol.%, and the molar ratio of SO3 to the olefinic polypropylene wax is 2:1.

[0054] (3) The sulfonic acid product from step (2) was reacted with a saturated sodium carbonate solution until the pH reached 8 to obtain a sulfonate product. The obtained sulfonate product was then dried in a vacuum oven to obtain an aliphatic sulfonate surfactant.

[0055] Example 2

[0056] A method for preparing aliphatic sulfonate surfactants from polyethylene plastic includes the following steps:

[0057] (1) Waste polyethylene was mechanically ground into powder with a particle size of less than 5 mm using a plastic machine. 10 g of powder was added to a flask in a glove box filled with N2. The flask was sealed with a vacuum stopper and flask clamps and then removed from the glove box. The flask containing polyethylene powder was then transferred to a high-temperature electric heating mantle and heated to 360°C at a heating rate of 10°C / min. After the reactor reached the set temperature, the polymer waste began to decompose. The reaction was maintained for 12 h and then gradually cooled to room temperature to obtain end-alkenyl polyethylene wax with a yield of 85 wt.%.

[0058] (2) In the sulfonation upgrade step, the sulfonation product is obtained by reacting terminal alkenyl polyethylene wax with SO3 gas; 2g of terminal alkenyl polyethylene wax from step (2) is added to a round-bottom flask and the flask is placed in an ice bath at 0°C to cool for 30min. Then, a mixture of SO3 and air is introduced into the round-bottom flask. After the reaction continues for 30min, the gas is stopped and the temperature is raised to room temperature. After aging at room temperature for 30min, the reaction is ended and the reactor is purged with dry air to remove residual SO3 and obtain sulfonic acid product.

[0059] The volume ratio of SO3 is 8 vol.%, and the molar ratio of SO3 to the olefinic polypropylene wax is 2:1.

[0060] (3) The sulfonic acid product from step (2) was reacted with a saturated sodium carbonate solution until the pH reached 8 to obtain a sulfonate product. The obtained sulfonate product was then dried in a vacuum oven to obtain an aliphatic sulfonate surfactant.

[0061] Example 3

[0062] A method for preparing aliphatic sulfonate surfactants from polypropylene and polyethylene mixed plastics includes the following steps:

[0063] (1) Waste polypropylene and waste polyethylene are mixed at a mass ratio of 1:1 and then mechanically ground into powder with a particle size of less than 5 mm using a plastic machine. 10 g of powder is added to a flask in a glove box filled with N2. The flask is sealed with a vacuum stopper and flask clamp and then removed from the glove box. The flask containing polypropylene powder and polyethylene powder is then transferred to a high-temperature electric heating mantle and heated to 360°C at a heating rate of 10°C / min. After the reactor reaches the set temperature, the polymer waste begins to decompose. The reaction is maintained for 12 h and then gradually cooled to room temperature to obtain end-alkenyl polyethylene / polypropylene wax with a yield of 85 wt.%.

[0064] (2) In the sulfonation upgrade step, the sulfonation product is obtained by reacting terminal alkenyl polyethylene / polypropylene wax with SO3 gas; 2g of terminal alkenyl polyethylene / polypropylene wax from step (2) is added to a round-bottom flask and the flask is placed in an ice bath at 0°C to cool for 30min. Then, a mixture of SO3 and air is introduced into the round-bottom flask. After the reaction continues for 30min, the gas is stopped and the temperature is raised to room temperature. After aging at room temperature for 30min, the reaction is ended and the reactor is purged with dry air to remove residual SO3 and obtain sulfonic acid product.

[0065] The volume ratio of SO3 is 8 vol.%, and the molar ratio of SO3 to the olefinic polypropylene wax is 2:1.

[0066] (3) The sulfonic acid product from step (2) was reacted with a saturated sodium carbonate solution until the pH reached 8 to obtain a sulfonate product. The obtained sulfonate product was then dried in a vacuum oven to obtain an aliphatic sulfonate surfactant.

[0067] Example 4

[0068] A method for preparing aliphatic sulfonate surfactants from polypropylene plastic includes the following steps:

[0069] (1) Waste polypropylene is mechanically ground into powder with a particle size of less than 5 mm using a plastic machine. 10 g of powder is added to a flask in a glove box filled with N2. The flask is sealed with a vacuum stopper and flask clamp and then removed from the glove box. The flask containing polypropylene powder is then transferred to a high-temperature electric heating mantle and heated to 200°C at a heating rate of 10°C / min. After the reactor reaches the set temperature, the polymer waste begins to decompose. The reaction is maintained for 16 h and then gradually cooled to room temperature to obtain end-alkenyl polypropylene wax.

[0070] (2) In the sulfonation upgrade step, the sulfonation product is obtained by reacting terminal alkenyl polypropylene wax with SO3 gas; 2g of terminal alkenyl polypropylene wax from step (1) is added to a round-bottom flask and the flask is placed in an ice bath at 0°C to cool for 1h. Then, a mixture of SO3 and air is introduced into the round-bottom flask. After the reaction continues for 2h, the gas is stopped and the temperature is raised to room temperature. After aging at room temperature for 1h, the reaction is ended and the reactor is purged with dry air to remove residual SO3 and obtain sulfonic acid product.

[0071] The volume percentage of SO3 is 3 vol.%, and the molar ratio of SO3 to the olefinic polypropylene wax is 3:1.

[0072] (3) The sulfonic acid product from step (2) was reacted with a saturated sodium carbonate solution until the pH was 7 to obtain a sulfonate product. The obtained sulfonate product was then dried in a vacuum oven to obtain an aliphatic sulfonate surfactant.

[0073] Example 5

[0074] A method for preparing aliphatic sulfonate surfactants from polypropylene plastic includes the following steps:

[0075] (1) Waste polypropylene is mechanically ground into powder with a particle size of less than 5 mm using a plastic machine. 10 g of powder is added to a flask in a glove box filled with N2. The flask is sealed with a vacuum stopper and flask clamp and then removed from the glove box. The flask containing polypropylene powder is then transferred to a high-temperature electric heating mantle and heated to 400°C at a heating rate of 10°C / min. After the reactor reaches the set temperature, the polymer waste begins to decompose. The reaction is maintained for 4 hours and then gradually cooled to room temperature to obtain end-alkenyl polypropylene wax.

[0076] (2) In the sulfonation upgrade step, the sulfonation product is obtained by reacting terminal alkenyl polypropylene wax with SO3 gas; 2g of terminal alkenyl polypropylene wax from step (1) is added to a round-bottom flask and the flask is placed in an ice bath at 5°C to cool for 2h. Then, a mixture of SO3 and air is introduced into the round-bottom flask. After the reaction continues for 1h, the gas is stopped and the temperature is raised to room temperature. After aging at room temperature for 2h, the reaction is ended and the reactor is purged with dry air to remove residual SO3 and obtain sulfonic acid product.

[0077] The volume percentage of SO3 is 20 vol.%, and the molar ratio of SO3 to the olefinic polypropylene wax is 1:1.

[0078] (3) The sulfonic acid product from step (2) was reacted with a saturated sodium carbonate solution until the pH reached 9 to obtain a sulfonate product. The obtained sulfonate product was then dried in a vacuum oven to obtain an aliphatic sulfonate surfactant.

[0079] Example 6

[0080] The preparation steps in this example are the same as in Example 1, except that a liquid sulfonating agent is used to prepare the aliphatic sulfonate surfactant. The liquid sulfonating agent consists of 1,4-dioxane and chlorosulfonic acid. The specific method is as follows:

[0081] (1) Waste polypropylene was mechanically ground into powder with a particle size of less than 5 mm using a plastic machine. 10 g of powder was added to a flask in a glove box filled with N2. The flask was sealed with a vacuum stopper and flask clamps and then removed from the glove box. The flask containing polypropylene powder was then transferred to a high-temperature electric heating mantle and heated to 360°C at a heating rate of 10°C / min. After the reactor reached the set temperature, the polymer waste began to decompose. The reaction was maintained for 10 h and then gradually cooled to room temperature to obtain terminal alkenyl polypropylene wax with a yield of 91 wt.%.

[0082] (2) Take 2g of the terminal alkenyl polypropylene wax from step (1) and add it to a round-bottom flask. Place the flask in an ice bath at 0°C and cool it for 30 minutes. Then slowly add the mixture of chlorosulfonic acid and 1,4-dioxane to the round-bottom flask. The molar ratio of the alkenyl bond of chlorosulfonic acid to the terminal alkenyl polypropylene wax and the 1,4-dioxane is 1:1:1. After the reaction continues for 30 minutes, raise the temperature to room temperature. After aging at room temperature for 30 minutes, stop the reaction and purge the reactor with dry air to obtain the sulfonic acid product.

[0083] (3) The sulfonic acid product from step (1) was reacted with a saturated sodium carbonate solution until the pH reached 8 to obtain a sulfonate product. The synthesized sulfonate product was then dried in a vacuum oven to obtain an aliphatic sulfonate surfactant.

[0084] Comparative Example 1

[0085] The preparation steps for this comparative example are the same as those for Example 1, except that 1 vol.% SO3 is used as the sulfonating agent to prepare the polypropylene-derived sulfonate surfactant. The specific method is as follows:

[0086] (1) Waste polypropylene was mechanically ground into powder with a particle size of less than 5 mm using a plastic machine. 10 g of powder was added to a flask in a glove box filled with N2. The flask was sealed with a vacuum stopper and flask clamps and then removed from the glove box. The flask containing polypropylene powder was then transferred to a high-temperature electric heating mantle and heated to 360°C at a heating rate of 10°C / min. After the reactor reached the set temperature, the polymer waste began to decompose. The reaction was maintained for 10 h and then gradually cooled to room temperature to obtain end-alkenyl polypropylene wax with a yield of 91 wt.%.

[0087] (2) In the sulfonation upgrade step, the sulfonation product is obtained by reacting terminal alkenyl polypropylene wax with SO3 gas; 2g of terminal alkenyl polypropylene wax from step (1) is added to a round-bottom flask and the flask is placed in an ice bath at 0°C to cool for 30min. Then, a mixture of SO3 and air is introduced into the round-bottom flask. After the reaction continues for 30min, the gas is stopped and the temperature is raised to room temperature. After aging at room temperature for 30min, the reaction is ended and the reactor is purged with dry air to remove residual SO3 and obtain sulfonic acid product.

[0088] The volume percentage of SO3 is 1 vol.%, and the molar ratio of SO3 to the olefinic polypropylene wax is 2:1.

[0089] (3) The sulfonic acid product from step (2) was reacted with a saturated sodium carbonate solution until the pH reached 8 to obtain a sulfonate product. The obtained sulfonate product was then dried in a vacuum oven to obtain an aliphatic sulfonate surfactant.

[0090] Comparative Example 2

[0091] The preparation steps of this comparative example are the same as those of Example 4, except that 1,4-dioxane is not used as a sustained-release agent, and pure chlorosulfonic acid is used as the sulfonating agent to prepare the aliphatic sulfonate surfactant. The specific method is as follows:

[0092] (1) Waste polypropylene was mechanically ground into powder with a particle size of less than 5 mm using a plastic machine. 10 g of powder was added to a flask in a glove box filled with N2. The flask was sealed with a vacuum stopper and flask clamps and then removed from the glove box. The flask containing polypropylene powder was then transferred to a high-temperature electric heating mantle and heated to 360°C at a heating rate of 10°C / min. After the reactor reached the set temperature, the polymer waste began to decompose. The reaction was maintained for 10 h and then gradually cooled to room temperature to obtain terminal alkenyl polypropylene wax with a yield of 91 wt.%.

[0093] (2) Take 2g of the terminal alkenyl polypropylene wax from step (1) and add it to a round-bottom flask. Place the flask in an ice bath at 0°C and cool it for 30 minutes. Then slowly add chlorosulfonic acid to the round-bottom flask. The molar ratio of the alkenyl bond of chlorosulfonic acid to the terminal alkenyl polypropylene wax is 1:1. After the reaction lasts for 30 minutes, raise the temperature to room temperature. After aging at room temperature for 30 minutes, stop the reaction and purge the reactor with dry air to obtain the sulfonic acid product.

[0094] (3) The sulfonate product from step (2) was reacted with saturated potassium carbonate solution until the pH was 8 to obtain the sulfonate product. The obtained sulfonate product was then dried in a vacuum oven to obtain an aliphatic sulfonate surfactant.

[0095] In Examples 1-6 of this invention, aliphatic sulfonate surfactants with excellent surface tension, foaming ability, and detergency were prepared. The following studies use samples from Examples 1-3, Example 6, Comparative Example 1, and Comparative Example 2 as examples, and the specific research methods and results are shown below:

[0096] Figure 1 A schematic diagram of the reaction for preparing aliphatic sulfonate surfactants for polypropylene plastics is shown. The conversion is divided into two steps: the polypropylene is decomposed into terminal alkenyl polypropylene wax, and the terminal alkenyl polypropylene wax is sulfonated into aliphatic sulfonate surfactants.

[0097] Figure 2 Gas chromatography showed that terminal alkenyl polypropylene wax is an aliphatic hydrocarbon containing 6-36 carbon atoms.

[0098] Figure 3 In the middle, terminal alkenyl polypropylene wax 1 The H NMR spectrum indicates the presence of terminal alkenyl groups.

[0099] Figure 4 In the preparation of aliphatic sulfonate surfactants from polypropylene 1 1H NMR spectroscopy indicates that the surfactant is mainly an alkenyl-containing aliphatic sulfonate surfactant.

[0100] Figure 5 Infrared spectroscopy indicates that the sulfonation step introduces sulfonic acid groups into the aliphatic wax, successfully synthesizing aliphatic sulfonate surfactants.

[0101] Figure 6 The photoelectron spectroscopy of sulfur element indicates that the aliphatic sulfonate surfactant prepared from polypropylene plastic has the same sulfonic acid functional group as sodium dodecyl sulfonate.

[0102] Figure 7 Surface tension tests showed that, at low concentrations, the aliphatic sulfonate surfactant prepared from polypropylene plastic had a similar surface tension to the commercial sodium dodecyl sulfonate standard; at high concentrations, the aliphatic sulfonate surfactant prepared from polypropylene plastic exhibited a lower surface tension.

[0103] Figure 8 Foaming experiments showed that, at the same concentration, the aliphatic sulfonate surfactant prepared from polypropylene plastic has a foaming ability close to that of sodium dodecyl sulfonate.

[0104] Figure 9 The stain removal ability test showed that the aliphatic sulfonate surfactant prepared from polypropylene plastic has a stronger stain removal ability than standard laundry detergent for standard protein-stained and sebum-stained cloths, and is close to that of sodium dodecyl sulfonate.

[0105] Figure 10The stain removal ability test showed that the aliphatic sulfonate surfactant prepared from polyethylene plastic had a stronger stain removal ability on standard protein-stained cloth than standard laundry detergent, and a stronger stain removal ability on sebum-stained cloth than standard laundry detergent and sodium dodecyl sulfonate.

[0106] Figure 11 The stain removal ability test showed that the aliphatic sulfonate surfactant prepared from polypropylene and polyethylene blended plastics had a stronger stain removal ability on standard protein-stained cloth than standard laundry detergent, and a stronger stain removal ability on sebum-stained cloth than standard laundry detergent and sodium dodecyl sulfonate.

[0107] Figure 12 The stain removal ability test showed that the aliphatic sulfonate surfactant obtained by using 1,4-dioxane and chlorosulfonic acid as sulfonating agents had a stronger stain removal ability than standard laundry detergent for standard protein-stained and sebum-stained cloths, and was close to that of commercial sodium dodecyl sulfonate.

[0108] Figure 13 Decontamination capacity tests showed that the aliphatic sulfonate surfactant prepared using 1 vol.% SO3 as the sulfonating agent had a lower decontamination capacity than standard protein-soaked cloth. Figure 9 Aliphatic sulfonate surfactants prepared using 8 vol.% SO3 as the sulfonating agent.

[0109] Figure 14 The stain removal ability test showed that, without using 1,4-dioxane as a slow-release agent, the aliphatic sulfonate surfactant obtained by using pure chlorosulfonic acid as the sulfonating agent had a lower stain removal ability than that of standard protein-stained cloth and sebum-stained cloth. Figure 12 The aliphatic sulfonate surfactant was obtained using 1,4-dioxane.

[0110] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both plastics, characterized in that, Includes the following steps: Under inert atmosphere conditions, plastic powder is pyrolyzed, and the pyrolysis conditions are: pyrolysis at 200-400℃ for 4-16h to obtain terminal alkenyl polymer wax; The plastic is selected from polypropylene, polyethylene, or a mixture of the two in any proportion; After cooling the terminal alkenyl polymer wax at 0-5℃ for 0.5-1h, it was reacted with a sulfonating agent for 0.5-2h, and then heated to room temperature and aged at room temperature for 0.5-2h to obtain the sulfonic acid product. The sulfonating agent is a liquid sulfonating agent or a gaseous sulfonating agent; the liquid sulfonating agent is composed of chlorosulfonic acid and a slow-release agent, wherein the slow-release agent is 1,4-dioxane. The gaseous sulfonating agent is a mixed gas containing SO3; The molar ratio of chlorosulfonic acid or SO3 to the olefinic polypropylene wax is 1-3:1; After adding alkali to the sulfonic acid product and reacting it, the product is dried to obtain an aliphatic sulfonate surfactant.

2. The method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both according to claim 1, characterized in that, The plastic is selected from waste or unused polypropylene or polyethylene.

3. The method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both according to claim 1, characterized in that, The pyrolysis process can also be carried out under catalytic conditions, wherein the catalyst for the catalytic conditions is selected from group I alkali metal oxides or transition metal oxides. The catalyst has a mass percentage of 0.1-20 wt.%.

4. The method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both according to claim 1, characterized in that, The inert atmosphere for the pyrolysis process is a nitrogen, argon, helium, carbon dioxide, or carbon monoxide atmosphere with an oxygen content of less than 10 vol.%.

5. The method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both according to claim 1, characterized in that, The molar ratio of chlorosulfonic acid to the sustained-release agent is 1:0.5-3.

6. The method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both according to claim 1, characterized in that, The SO3 mixture is a mixture of SO3 and diluent gases, with SO3 having a volume percentage of 3-20 vol.%. The diluent gas is selected from air, nitrogen, argon, helium, carbon dioxide, or carbon monoxide.

7. The method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both according to claim 1, characterized in that, The base that reacts with the sulfonic acid product is selected from one or more of potassium hydroxide, potassium bicarbonate, potassium carbonate, sodium hydroxide, sodium bicarbonate, and sodium carbonate.

8. The method for preparing aliphatic sulfonate surfactants from polypropylene, polyethylene, or a mixture of both according to claim 1, characterized in that, After adding alkali, the reaction proceeds until the pH reaches 7-9.

Images