A sulfur-containing polymer based on a polyethylene backbone, its preparation method and application
By using dihalogenated hydrocarbons and alkali metal sulfides in toluene solvents for nucleophilic substitution reactions, sulfur-containing polymers based on polyethylene frameworks were prepared, which solved the degradation instability and complex preparation of existing plastic film materials, and achieved efficient and low-cost biodegradation effect.
Patent Information
- Application Number
- CN202510168915.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-17
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2045-02-17
AI Technical Summary
The existing degradable plastic film materials have problems in unstable degradation speed, poor mechanical properties, high costs or degradation products are harmful to the environment, and the preparation process of sulfur-containing polymers is complex and the yield is low.
A continuous nucleophilic substitution reaction was carried out in a toluene solvent by dihalogenated hydrocarbons and alkali metal sulfides to prepare sulfur-containing polymers based on polyethylene frameworks, and the products were obtained by a one-pot method, simplifying the process and improving yield.
Sulfur-containing polymers with excellent mechanical properties and thermal stability were prepared, which achieved good biodegradation performance in the soil, with controllable degradation rate, environmentally friendly degradation products, high degradation rate, and yields up to more than 85%.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of polymer materials, in particular to a sulfur-containing polymer based on a polyethylene backbone, a preparation method thereof and an application thereof. Background Art
[0002] The ground covering film agricultural technology has become a new cultivation technology developed in China in the 1970s. The ground covering film agricultural technology is to cover the ground surface closely with a transparent or colored plastic film with a thickness of 0.01 - 0.02 mm for cultivation. It is the simplest and most feasible form of protected ground. Its functions are to increase the soil temperature, promote the development of roots, thereby increasing the yield and output value of crops. In addition, the plastic film covering also has effective functions such as moisture preservation, water conservation, weed control, promoting the decomposition of organic fertilizers, and keeping the soil loose (preventing soil compaction).
[0003] Traditional plastic films used have the characteristics of high strength, light weight, corrosion resistance, easy processing, low price, etc. They are widely used in people's production and life. However, while bringing great convenience to people, they also bring serious negative impacts. Since the waste plastic films after use are adhered with clay and cannot be recycled, putting them in farmland will affect the soil quality and crop cultivation, and it takes about a hundred years to degrade. Long-term residues in the natural environment can cause serious environmental pollution, not only affecting the ecological balance, but also threatening human health. If the used plastic films cannot be degraded and remain in the soil, they will cause white pollution to the soil.
[0004] Although a number of emerging degradable films have emerged, such as: 1) starch-based biodegradable films, but their dissolution rate is relatively fast in a humid environment, and the degradation rate is unstable; the mechanical properties are poor and the heat resistance is low; 2) polylactic acid (PLA) films, not only the production cost is high, but also the degradation rate is greatly affected by environmental conditions, and the degradation products will have a certain impact on the soil and the environment; 3) the degradation rate of cellulose-based biodegradable films is also slow; 4) polyhydroxyalkanoates (PHA) films cannot be produced on a large scale at present, the cost is high, and the degradation rate is also greatly affected by the environment; 5) plant residues or straw can also be used for covering, but it is easy to cause weed growth or pests, affecting crop growth.
[0005] Introducing sulfur elements into the main chain of carbon chain polymers can obtain sulfur-containing polymers based on polyethylene backbones, which can have both high mechanical strength and excellent biodegradation performance, especially having good degradation performance in soil and organisms. However, at present, the preparation process of this sulfur-containing polymer is complex and the yield is low, increasing the production cost.
[0006] Therefore, there is an urgent need to provide a biodegradable material with a simple production process, low cost and good degradation performance. Summary of the Invention
[0007] The object of the present invention is to overcome the above deficiencies in the prior art and provide a sulfur-containing polymer based on a polyethylene backbone.
[0008] Another object of the present invention is to provide a method for preparing the sulfur-containing polymer based on a polyethylene backbone.
[0009] Another object of the present invention is to provide the application of the sulfur-containing polymer based on a polyethylene backbone in the preparation of plastic films.
[0010] To achieve the above objects, the present invention adopts the following technical solutions:
[0011] In the first aspect of the present invention, a method for preparing a sulfur-containing polymer based on a polyethylene backbone is provided, including the following steps:
[0012] Dissolve a dihalohydrocarbon and an alkali metal sulfide in toluene to obtain a reaction solution, and then carry out a continuous nucleophilic substitution reaction at 120-140 °C in an inert atmosphere for 48-96 h. After purification, the sulfur-containing polymer based on a polyethylene backbone can be obtained.
[0013] The present invention uses a dihalohydrocarbon and an alkali metal sulfide as reaction raw materials, and carries out a continuous nucleophilic substitution reaction in a toluene solvent at a relatively high temperature. The alkali metal sulfide itself is a good nucleophile, which continuously carries out nucleophilic substitution on the halogen substituents to complete carbon chain growth, obtaining a sulfur-containing polymer with a polyethylene backbone, and introducing sulfur atoms into the main chain of the polyethylene long chain. The preparation method of the present invention has simple reaction raw materials (only containing reaction monomers and solvents), low cost during the synthesis process, and obtains the product through a one-pot method, reducing the loss caused by multi-step reactions and having a high yield.
[0014] In this polymer, the polyethylene backbone has excellent mechanical properties and thermal stability. The introduction of sulfur atoms onto the polyethylene backbone can form bio-attackable chemical bonds conducive to degradation, achieving a slow degradation effect; the introduction of sulfur atoms can also alleviate the problem of sulfur element deficiency in the soil and help plant growth when used in agriculture.
[0015] Toluene has low toxicity, a relatively high boiling point, and higher solubility for the reaction raw materials. Since the nucleophilic substitution reaction is a polar reaction, a non-protic polar organic solvent is selected. And because this reaction will compete for substitution with protic solvents such as water, water is not allowed to appear in the system.
[0016] In the present invention, the reaction equation of the dihalohydrocarbon and the alkali metal sulfide (taking sodium sulfide as an example) is as follows:
[0017]
[0018] Preferably, the purification comprises the following steps: after the nucleophilic substitution reaction is completed, liquid separation, rotary evaporation, suction filtration and drying are performed in sequence.
[0019] Preferably, the inert atmosphere is a gas atmosphere obtained by mixing at least one gas selected from the group consisting of helium, neon, argon and nitrogen.
[0020] In the present invention, the alkali metal sulfide needs to be added to the toluene solvent together with the dihalogenated hydrocarbon, and the above-mentioned gas capable of forming an inert atmosphere is introduced in advance to eliminate the influence of moisture on the reaction as much as possible.
[0021] Preferably, the molar ratio of the dihalogenated hydrocarbon to the alkali metal sulfide is 1:(2-3). Excessive alkali metal sulfide can ensure sufficient nucleophilic reaction; the dosage ratio within the above appropriate range can further ensure that the product has moderate viscosity, which is convenient for purification operation, especially for subsequent liquid separation operation.
[0022] Preferably, the dihalogenated hydrocarbon is selected from X-(CH2) n -CH2X, n=6-16, X represents a halogen, and the halogen is at least one of F, Cl, and Br elements, and X is preferably Br.
[0023] Preferably, the alkali metal sulfide includes at least one of sodium sulfide and potassium sulfide.
[0024] Preferably, in the reaction solution, the concentration of the dihalogenated hydrocarbon is 1.0-2.0 mol / L.
[0025] After the nucleophilic substitution reaction is completed, a capping agent is added for capping. Common capping agents in the art can be used for capping in the present invention, and the capping agent is preferably monosulfane, which will not introduce hetero elements and is conducive to improving the purity of the product.
[0026] In the present invention, the nucleophilic substitution reaction is carried out in a closed environment, and the closed environment is achieved by a closed device containing a reflux pipe.
[0027] The second aspect of the present invention further provides a sulfur-containing polymer based on a polyethylene skeleton, wherein the sulfur-containing polymer based on a polyethylene skeleton is prepared by the preparation method described in the first aspect of the present invention.
[0028] The third aspect of the present invention also provides the application of the sulfur-containing polymer based on the polyethylene skeleton described in the second aspect of the present invention for preparing biodegradable mulch films for use in the agricultural field; it can also be used as a drug carrier for preparing anti-tumor drugs.
[0029] Compared with the prior art, the present invention has the following beneficial effects:
[0030] The preparation method of the present invention has simple reactants and low cost during the synthesis process. By adjusting the reaction conditions, the product can be obtained by a one-pot method under the conditions of only containing the precursor of the reaction monomer and the solvent, without small molecule additives such as capping agents and acid-base regulators. This not only reduces the losses caused by multi-step reactions and has a high yield, but also avoids the influence of other reaction raw materials on the structure and properties of the product. Description of the Drawings
[0031] Figure 1 It is the thermogravimetric analysis diagram of the product prepared in Example 1;
[0032] Figure 2 It is the differential scanning calorimetry diagram of the product prepared in Example 1;
[0033] Figure 3 It is the nuclear magnetic resonance hydrogen spectrum of the product prepared in Example 1 (Figure a) and the product prepared in Comparative Example 8 (Figure b);
[0034] Figure 4 It is the nuclear magnetic resonance hydrogen spectrum of the product prepared in Example 2 (Figure a) and the product prepared in Example 3 (Figure b);
[0035] Figure 5 It is the thermogravimetric analysis diagram of the product prepared in Comparative Example 8;
[0036] Figure 6 It is the differential scanning calorimetry diagram of the product prepared in Comparative Example 8;
[0037] Figure 7 It is the Fourier transform infrared spectrum of the product prepared in Example 1;
[0038] Figure 8 It is the degradation performance test diagram of the product prepared in Example 1;
[0039] Figure 9 It is the nuclear magnetic resonance hydrogen spectrum diagram of the product prepared in Comparative Example 1;
[0040] Figure 10 It is the thermogravimetric analysis diagram of the product prepared in Comparative Example 6. Detailed Embodiments
[0041] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific examples and drawings. However, the examples do not impose any form of limitation on the present invention. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field. Unless otherwise specified, the reagents and materials used in the present invention are all commercially available.
[0042] Example 1
[0043] This embodiment provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by a method comprising the following steps:
[0044] In a closed device equipped with a reflux tube, after mixing 10 mmol of 1,10-dibromodecane, 25 mmol of sodium sulfide and 10 mL of toluene solvent uniformly, nitrogen is blown for 15 min to exhaust air, obtaining a reaction solution. Then, a continuous nucleophilic substitution reaction is carried out at 120 °C for 3 days. After standing for liquid separation, rotary evaporation and suction filtration, it is dried to constant weight in an oven at 60 °C, and the sulfur-containing polymer based on the polyethylene backbone can be obtained.
[0045] The nuclear magnetic resonance hydrogen spectrum of the product is shown in Figure 3 , and the characteristic peak at 2.5 ppm can confirm that sulfur atoms are introduced into the polyethylene main chain structure. Secondly, thermogravimetric analysis ( Figure 1 ) shows that the thermal decomposition temperature of the product is 329.79 °C.
[0046] Example 2
[0047] This embodiment provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that 1,10-dibromodecane is replaced with an equimolar amount of 1,6-dibromohexane.
[0048] Example 3
[0049] This embodiment provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that 1,10-dibromodecane is replaced with an equimolar amount of 1,16-dibromohexadecane.
[0050] Example 4
[0051] This embodiment provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that the reaction temperature of nucleophilic substitution is 140 °C and the reaction time of nucleophilic substitution is 2 days.
[0052] Example 5
[0053] This embodiment provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that the amount of toluene solvent used is 50 mL.
[0054] Example 6
[0055] This embodiment provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that the amount of sodium sulfide used is replaced with 30 mmol.
[0056] Comparative Example 1
[0057] This comparative example provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that the reaction temperature of the nucleophilic substitution is 150 °C.
[0058] Comparative Example 2
[0059] This comparative example provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that the solvent is replaced with xylene.
[0060] Comparative Example 3
[0061] This comparative example provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that the solvent toluene is replaced with an equal volume of diethyl ether.
[0062] Comparative Example 4
[0063] This comparative example provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that the solvent toluene is replaced with an equal volume of N,N-dimethylformamide.
[0064] Comparative Example 5
[0065] This comparative example provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that the solvent toluene is replaced with an equal volume of ethanol.
[0066] Comparative Example 6
[0067] This comparative example provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that no solvent is added.
[0068] Comparative Example 7
[0069] This comparative example provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by referring to the method of Example 1. The difference from Example 1 is that the reaction temperature of the nucleophilic substitution is 80 °C.
[0070] Comparative Example 8
[0071] This comparative example provides a sulfur-containing polymer based on a polyethylene backbone, which is prepared by the following method:
[0072] In a closed device equipped with a reflux pipe, 155 mmol of 1,10-dibromodecane, 310 mmol of sodium sulfide, and 140 mmol of the acid-base regulator sodium carbonate were dissolved in 90 mL of toluene solvent. After that, the temperature was raised to 80 °C, and nitrogen was bubbled for 15 min to exhaust the air, obtaining a reaction solution. Then, a continuous nucleophilic substitution reaction was carried out at 125 °C for 2 days. A capping agent was added for capping (the capping reaction took about 1 day). After standing for liquid separation, rotary evaporation, and suction filtration, it was dried in an oven at 60 °C to a constant weight, and the sulfur-containing polymer based on the polyethylene backbone could be obtained.
[0073] The proton nuclear magnetic resonance spectrum of the product is shown in Figure 3 (Figure b). The characteristic peak at 2.5 ppm can confirm that sulfur atoms are introduced into the polyethylene main chain structure. Secondly, from the thermogravimetric analysis ( Figure 5 ), it can be obtained that the thermal decomposition temperature of the product is 297.19 °C, further confirming the formation of the polyethylene main chain.
[0074] Performance testing
[0075] The products obtained in the above examples and comparative examples and their performances were characterized. The specific test items, test methods, and results are as follows:
[0076] 1. Structure characterization:
[0077] (1) Through thermogravimetric analysis, as shown in Figure 1 , taking Example 1 as an example, it shows that: the product is almost completely decomposed within the characterization temperature range, the inorganic phase and the organic phase are completely separated, and the product purity is high. The product has a high degree of polymerization, so the thermal decomposition temperature is also high, and the thermal decomposition temperature is about 329.79 °C.
[0078] The test results of the products of other examples are similar to those of Example 1. For details, see Table 1.
[0079] (2) The results of differential scanning calorimetry ( Figure 2 ) show that: the melting point of the product of Example 1 is about 81.95 °C, and the crystallization temperature is 68.00 °C. The test results of the products of other examples are shown in Table 1. It can be seen that: the melting points of the products prepared by the method of the present invention are all above 67.59 °C, and the crystallization temperatures are above 55.2 °C, which is convenient for subsequent film processing.
[0080] (3) Fourier transform infrared spectroscopy ( Figure 7 ) observed that the product in Example 1 has functional group signals similar to those of polyethylene, indicating that a polyethylene long-chain structure has been successfully synthesized in the product. The test results of other examples are similar.
[0081] (4) Proton nuclear magnetic resonance spectrum:
[0082] The product dissolved in toluene solvent (i.e., the sulfur-containing polymer based on the polyethylene backbone described above in the present invention) can be obtained by means of liquid separation, rotary evaporation, suction filtration and drying; since the product has a similar structure to polyethylene and a relatively high degree of polymerization, it cannot be well dissolved in the test solvent deuterated chloroform. Therefore, it is somewhat difficult to perform a nuclear magnetic resonance hydrogen spectrum test on the product, and the peak signal (at 2.5 ppm) measured is a bit weak (see Figure 3 (a)), and no peak signal of the bromine end group (at 3.4 ppm) is observed in the product, indicating that the raw material dibromodecane has fully reacted.
[0083] To further confirm the structure of the product, the products obtained from Comparative Example 8 (see Figure 3 (b)) and Example 2 (see Figure 4 (a)), the products obtained from Example 3 (see Figure 4 (b)) were used as references to verify the hydrogen spectrum results of similar structures.
[0084] 2. Application performance test
[0085] The products prepared in the above examples and comparative examples were tested by the closed-circuit respiration measurement method (ISO 17556:2019) to analyze the amount of carbon dioxide generated and the amount of oxygen consumed. Under ideal conditions, the biodegradation of plastic materials should achieve complete conversion, and its final products should be carbon dioxide, water and biomass. Specifically, the organic components in the plastic are decomposed by microbial metabolism, and the carbon element is mainly released in the form of carbon dioxide through respiration. Therefore, by measuring the oxygen demand and the amount of carbon dioxide generated in the closed system, the final aerobic biodegradability of the plastic in the soil is determined, and the degradation rate is expressed by the amount of carbon dioxide generated. The test results are shown in Table 1 and Figure 8 (Example 1). It can be seen from Figure 8 that within the first 5 days, the sulfur-containing polymer degrades the fastest, which may be due to the loss of impurity salts and small molecules by hydrolysis. Starting from the 5th day, the degradation of the product begins to slow down. This stage of degradation belongs to the slow degradation of the sulfur-containing polymer product. In the present invention, the degradation rate on the 7th day (when the degradation rate is about to tend to a stable state) is selected for testing. The test results of other examples and comparative examples are shown in detail in Table 1.
[0086] 3. The yield is calculated according to the following formula: Yield .
[0087] The test results are shown in detail in Table 1.
[0088] Table 1
[0089]
[0090] It can be seen from the above results that:
[0091] The present invention successfully prepared a sulfur-containing polymer material based on a polyethylene backbone with excellent degradation performance and mechanical properties by a simple method. Moreover, the yield is high, all above 85%.
[0092] For the sulfur-containing polymer material based on a polyethylene backbone of the present invention, the crystallization temperature is all above 55 °C, which is convenient for processing; the thermal decomposition temperature is all above 200 °C, having excellent thermal stability; the degradation rate is all above 30 mg CO2 / g polymer / day.
[0093] The reaction temperature of Comparative Example 1 was too high and the reaction was violent, resulting in a change in the product structure (see Figure 9 ). As can be seen from the figure, the signal at 2.5 ppm in the spectrum is very low and the peak positions and peak intensities of the characteristic peaks in the range of 0.6 ppm - 1.8 ppm are different from those of the product of Example 1 ( Figure 3 (a)), so it is considered that Comparative Example 1 is not the expected product of ours.
[0094] The results of Example 1 and Comparative Examples 2 - 5 show that after the solvent was changed, water and ethanol solvents themselves have nucleophilic ability, so they will compete with thiol in the long-term heating reaction process, resulting in the failure of the reaction; for ether and N,N-dimethylformamide, it is because the solubility and boiling point are quite different from those of the reaction raw materials used in this application, resulting in no reaction.
[0095] In Comparative Example 6, no solvent was added and the reaction was only carried out at high temperature. Although the yield can reach more than 50%, the obtained product is in a sticky paste state rather than powder. And from the thermogravimetric analysis graph ( Figure 10 ), it can be seen that the product has multiple decomposition temperatures, proving that the polymerization in the product is uneven, resulting in the product being unable to form a film for use.
[0096] In Comparative Example 7, the reaction temperature was low and the yield was low.
[0097] In Comparative Example 8, sodium carbonate, an acid-base environment regulator, was added, and the reaction was carried out in two stages of temperature increase. Through thermogravimetric analysis ( Figure 5 ), differential scanning calorimetry ( Figure 6 ), and nuclear magnetic resonance hydrogen spectrum ( Figure 3 the b graph in), it was shown that a sulfur-containing polymer based on a polyethylene backbone could be prepared. However, from the comparison of Figure 3 (nuclear magnetic resonance hydrogen spectrum), it can be seen that the peak of the bromine end group at 3.4 ppm in the product of Comparative Example 8 is stronger, indicating that more bromine end groups are generated and the molecular weight of the product is reduced, indicating low reaction efficiency and ineffective growth of the polymer chain.
[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for preparing a sulfur-containing polymer based on a polyethylene backbone, characterized in that, It includes the following steps: Dissolve the dihalohydrocarbon and alkali metal sulfide in toluene to obtain a reaction solution, and then carry out a continuous nucleophilic substitution reaction at 120-140 °C in an inert atmosphere for 48-96 h. After the nucleophilic substitution reaction is completed, liquid separation, rotary evaporation, suction filtration and drying are carried out in sequence to obtain the sulfur-containing polymer based on the polyethylene backbone; Among them, the dihalohydrocarbon is 1,10-dibromodecane, 1,6-dibromohexane or 1,16-dibromohexadecane.
2. The preparation method of the sulfur-containing polymer based on a polyethylene backbone according to claim 1, characterized in that, The molar ratio of the dihalohydrocarbon to the alkali metal sulfide is 1:(2-3).
3. The preparation method of the sulfur-containing polymer based on a polyethylene backbone according to claim 1, wherein, In the reaction solution, the concentration of the dihalohydrocarbon is 1.0-2.0 mol / L.
4. The preparation method of the sulfur-containing polymer based on a polyethylene backbone according to claim 1, wherein, The alkali metal sulfide includes at least one of sodium sulfide and potassium sulfide.
5. The preparation method of the sulfur-containing polymer based on a polyethylene backbone according to claim 1, wherein, The nucleophilic substitution reaction is carried out in a closed environment.
6. The preparation method of the sulfur-containing polymer based on a polyethylene backbone according to claim 1, characterized in that, After the nucleophilic substitution reaction is completed, a capping agent is also added for capping.