A method for preparing a starch-based polyurethane sprayable foam mulch
By using a method for preparing starch-based polyurethane foam, which utilizes the cross-linking reaction between starch and aldehydes to form isocyanate-free foam, the toxicity and environmental pollution problems of traditional polyurethane foam are solved, achieving low cost and controllable degradation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HENAN ACADEMY OF SCI CHEM RES INST CO LTD
- Filing Date
- 2025-03-11
- Publication Date
- 2026-06-26
AI Technical Summary
The isocyanates used in the preparation of traditional polyurethane foam mulch films have toxicity issues and are difficult to biodegrade in a low-cost and controllable manner. In addition, traditional mulch film materials cause serious environmental pollution.
A urethane starch is synthesized using starch, urea, and a catalyst. Through the condensation and cross-linking reaction of urethane starch with aldehydes and in-situ foaming, an isocyanate-free starch-based polyurethane foam is formed. Water generated during the condensation process is used as a foaming agent, avoiding the need for high temperatures and additional foaming agents.
A low-cost, biodegradable, and environmentally friendly polyurethane foam mulch film was prepared, which has good thermal insulation properties, avoids the use of isocyanate, simplifies the operation process, and is suitable for various terrains.
Smart Images
Figure CN120005262B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer materials and green chemistry technology, and specifically discloses a method for preparing a starch-based polyurethane sprayable foam mulch film. Background Technology
[0002] Mulching technology, as a key element of modern agricultural production systems, has become an important guarantee for my country's food security. This technology significantly improves grain production capacity by precisely controlling the soil's water and heat environment. However, traditional polyethylene (PE) mulch film is difficult to degrade and recycle, leading to serious "white pollution." Therefore, developing environmentally friendly, biodegradable mulch film materials has become a strategic priority for my country's green agricultural transformation.
[0003] Currently, biodegradable mulch film materials mainly include synthetic polymers and natural polymers. Synthetic polymer materials, such as polylactic acid (PLA), polybutylene succinate (PBS), and polybutylene terephthalate-adipate (PBAT), possess basic mechanical properties, but face application bottlenecks such as uncontrollable degradation rates and high costs. Natural polymers, represented by starch and cellulose, offer significant environmental advantages and low cost, but their hydroxyl groups cause significant water sensitivity, making it difficult to meet the mechanical strength requirements of mulch films. Technological breakthroughs require collaborative innovation in material modification, processing technology, and degradation mechanisms. A novel sprayable liquid mulch film technology achieves functional integration breakthroughs through nozzle atomization and low-temperature film formation processes: ① Using biodegradable polymers as raw materials, a uniform film layer can be formed after curing using atomized spraying technology; ② It can carry agricultural auxiliary materials such as slow-release fertilizers and herbicides; ③ It has strong terrain adaptability and is suitable for complex terrains such as hills and slopes.
[0004] In recent years, the concept of sprayable foam mulch has been proposed. Compared to the aforementioned types of mulch, polyurethane (PU) foam mulch achieves a leap in thermodynamic properties. Furthermore, through structural unit design, it can be endowed with multifunctional properties such as flexibility, rigidity, lightweight, wear resistance, and biodegradability. However, the raw materials for traditional polyurethane foam are mostly derived from petrochemical resources or produced by reacting polyisocyanates with compounds containing active hydrogen. Landfilling and incineration after disposal can cause ecological pollution, and polyisocyanates and their raw material phosgene are highly toxic substances, posing significant harm to the environment and human health. Both production and use can potentially cause harm to human health. Currently, most research uses bio-based polyols to construct PU to increase the bio-based content. Although the PU industry is constantly striving to improve the quality of PU raw materials, for example, by using bio-based diisocyanates from natural resources, there is an urgent need for more environmentally friendly processes to address the renewability of starting materials and the sustainability of synthesis. Summary of the Invention
[0005] To address the problems in the background art, this invention discloses a method for preparing a starch-based polyurethane sprayable foam mulch film, aiming to solve the isocyanate toxicity problem in the traditional polyurethane foam preparation process and develop a low-cost, biodegradable, and heat-insulating polyurethane foam mulch film that is free of isocyanates.
[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:
[0007] A method for preparing a starch-based polyurethane sprayable foam mulch film, characterized by comprising the following steps:
[0008] (1) Preparation of carbamate starch
[0009] Starch, urea and catalyst were added to a flask in a mass ratio of 1:(1-5):(0.01-0.05), stirred and heated to 150 degrees Celsius to melt the urea and dissolve the starch. The reaction was kept at a constant temperature for 4 hours. After the reaction was completed, the product was washed multiple times with an alcohol-water mixture. The washed product was then dried to obtain carbamate starch.
[0010] (2) Preparation of starch-based polyurethane foam mulch film
[0011] The carbamate starch obtained in step (1) is mixed with surfactant, catalyst and aldehyde in a mass ratio of 1:(0.02-0.05):(0.01-0.07):(0.01-0.08). The mixture is heated to melt, and after the melt is mixed evenly, it is heated to 50℃-85℃ to carry out cross-linking reaction and in-situ foaming to obtain solid foam. The aldehyde is one or a mixture of glutaraldehyde, vanillin and cyclohexane-1,4-dicarboxaldehyde.
[0012] Furthermore, in the preparation method of the starch-based polyurethane sprayable foam mulch film, the starch in step (1) is at least one of corn starch, potato starch and potato starch.
[0013] Furthermore, in the preparation method of the starch-based polyurethane sprayable foam film, the catalyst in step (1) is at least one of ammonium chloride, copper chloride, and stannous chloride.
[0014] Furthermore, in the preparation method of the starch-based polyurethane sprayable foam film, the surfactant in step (2) is dimethyl silicone oil, methyl phenyl silicone oil, methyl trifluoropropyl silicone oil or methyl vinyl silicone oil.
[0015] Furthermore, in the preparation method of the starch-based polyurethane sprayable foam mulch film, the catalyst in step (2) is formic acid, phosphoric acid, or ethyl phosphate.
[0016] Furthermore, in the preparation method of the starch-based polyurethane sprayable foam film, the mass ratio of urethane starch, surfactant, catalyst and aldehyde in step (2) is 1:(0.02-0.05):(0.02-0.05):(0.03-0.05).
[0017] Furthermore, in the method for preparing the starch-based polyurethane sprayable foam mulch film, the starch-based polyurethane foam is a closed-cell foam and / or an open-cell foam.
[0018] By adopting the above technical solution, the present invention has the following beneficial effects:
[0019] This invention discloses a method for preparing a starch-based polyurethane sprayable foam mulch film. First, urethane starch is synthesized using starch, urea, and a catalyst. The urethane starch is then blended with aldehydes under the action of surfactants and catalysts to undergo a condensation and crosslinking reaction. This crosslinking reaction is simultaneous with in-situ foaming. Water generated during the condensation process volatilizes at a specific temperature, acting as a foaming agent to form foam. No additional foaming agent is needed. This method synthesizes a starch-based polyurethane foam with urethane structural units, avoiding the use of isocyanates and the potential toxicity associated with isocyanate raw materials. It is environmentally friendly and meets environmental requirements. By introducing starch, the foam exhibits good thermal insulation properties, controllable degradation performance, and low cost, reducing costs and increasing degradation performance to a certain extent. Furthermore, this preparation method does not require high temperatures or additional foaming agents, making it simple to operate. The mulch film prepared according to the method disclosed in this invention is mainly used in agricultural mulch films and is suitable for various terrains. Attached Figure Description
[0020] Figure 1 This is an image of the starch-based polyurethane sprayable foam mulch film prepared in Example 5 of this invention;
[0021] Figure 2 This is an image of the sprayable polyurethane foam mulch film prepared in Comparative Example 1 of this invention.
[0022] Figure 3 These are infrared images of starch, urea, and carbamate starch in Example 5 of this invention;
[0023] Figure 4 This is the XRD pattern of starch and carbamate starch in Example 5 of the present invention. Detailed Implementation
[0024] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.
[0025] The raw materials and reagents used in the examples and comparative examples, unless otherwise specified, are all commercially available products. The chemical raw materials used in the following examples are all commercially available, chemically pure reagents. Example 1
[0026] Corn starch, urea, and ammonium chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:1:0.01. The mixture was heated to 150°C. After the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3 and dried to obtain urethane starch. The urethane starch, dimethyl silicone oil, ethyl phosphate, and glutaraldehyde were mixed evenly at a mass ratio of 1:0.02:0.01:0.01 and foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanate. Example 2
[0027] Potato starch, urea, and copper chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:1:0.01. The mixture was heated to 150°C. After the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3 and dried to obtain urethane starch. The urethane starch, methyl vinyl silicone oil, phosphoric acid, and glutaraldehyde were mixed evenly at a mass ratio of 1:0.02:0.01:0.01 and foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanates. Example 3
[0028] Potato starch, urea, and stannous chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:1:0.01. The mixture was heated to 150°C. After the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3 and dried to obtain urethane starch. The urethane starch, methylphenyl silicone oil, formic acid, and glutaraldehyde were mixed evenly at a mass ratio of 1:0.02:0.01:0.01 and foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanates. Example 4
[0029] Corn starch, urea, and ammonium chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:3:0.03. The mixture was heated to 150°C. After the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3 and dried to obtain urethane starch. The urethane starch, dimethyl silicone oil, ethyl phosphate, and glutaraldehyde were mixed evenly at a mass ratio of 1:0.02:0.01:0.01 and foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanate. Example 5
[0030] Corn starch, urea, and ammonium chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:3:0.03. The mixture was heated to 150°C, and after the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3, and then dried to obtain carbamate starch. Infrared spectroscopy images of starch, urea, and carbamate starch are shown below. Figure 3 As shown, the XRD patterns of starch and carbamate starch are as follows. Figure 4 As shown; urethane starch, dimethyl silicone oil, ethyl phosphate, and glutaraldehyde are mixed evenly in a mass ratio of 1:0.04:0.04:0.04 and then foamed at 50℃-85℃ to obtain an isocyanate-free starch-based polyurethane sprayable foam mulch film, such as... Figure 1 As shown. Example 6
[0031] Corn starch, urea, and ammonium chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:5:0.05. The mixture was heated to 150°C. After the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3 and dried to obtain urethane starch. The urethane starch, dimethyl silicone oil, ethyl phosphate, and glutaraldehyde were mixed evenly at a mass ratio of 1:0.05:0.03:0.08 and foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanate. Example 7
[0032] Corn starch, urea, and ammonium chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:5:0.02. The mixture was heated to 150°C. After the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3 and dried to obtain urethane starch. The urethane starch, methyltrifluoropropyl silicone oil, ethyl phosphate, and cyclohexane-1,4-dicarboxaldehyde were mixed evenly at a mass ratio of 1:0.05:0.07:0.04 and foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanate. Example 8
[0033] Corn starch, urea, and ammonium chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:3:0.05. The mixture was heated to 150°C. After the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3 and dried to obtain urethane starch. The urethane starch, methyl vinyl silicone oil, ethyl phosphate, and vanillin were mixed evenly at a mass ratio of 1:0.03:0.04:0.05 and foamed at 85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanate. Example 9
[0034] Potato starch, urea, and stannous chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:3:0.04. The mixture was heated to 150°C. After the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3 and dried to obtain urethane starch. The urethane starch, methyl vinyl silicone oil, ethyl phosphate, and cyclohexane-1,4-dicarboxaldehyde were mixed evenly at a mass ratio of 1:0.03:0.04:0.05 and foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanate. Comparative Example 1
[0035] Corn starch, urea, and ammonium chloride were added to a three-necked flask equipped with a mechanical stirrer at a mass ratio of 1:3:0.04. The mixture was heated to 150°C. After the urea was completely melted, the reaction was continued for 4 hours. After the reaction was completed, the mixture was washed three times with an alcohol-water mixture at a mass ratio of 7:3 and dried to obtain urethane starch. Uramate starch, methyl vinyl silicone oil, ethyl phosphate, and diphenylmethane diisocyanate were mixed at a mass ratio of 1:0.05:0.03:0.04 and foamed at 50°C to obtain a polyurethane foam mulch film. Figure 2 As shown.
[0036] The foaming conditions of Examples 1-11 and the comparative examples are shown in Table 1 below.
[0037] Table 1. Foaming results of the examples and comparative examples
[0038] project Can it foam? Isocyanate present or absent Cell morphology Example 1 able none Relatively uniform, with both large and small pores. Example 2 able none Relatively uniform, with both large and small pores. Example 3 able none Relatively uniform, with both large and small pores. Example 4 able none uniform Example 5 able none uniform Example 6 able none More large holes Example 7 able none More large holes Example 8 able none uniform Example 9 able none uniform Comparative Example 1 able have Uneven, with collapses
[0039] According to the experimental results in Table 1, Examples 4, 5, and 8-9 used different types of starch to prepare urethane starch. The urethane starch and aldehyde underwent a polycondensation crosslinking reaction, successfully preparing isocyanate-free starch-based polyurethane foam. According to Examples 1-3 and Examples 6 and 7, the amount of urea and catalyst has a significant impact on the cell morphology. Therefore, it is necessary to select appropriate amounts of urea and catalyst. Compared with Comparative Example 1, Examples 1-9 have more uniform cells, which may be due to the excessively fast reaction rate of diphenylmethane diisocyanate under the action of the catalyst.
[0040] In summary, this invention develops a low-cost, biodegradable, and thermally insulating isocyanate-free polyurethane foam mulch film preparation method. The embodiments utilize various urethane starches and different types of aldehydes in a polycondensation process. The cross-linking reaction of the urethane starch and aldehydes is simultaneous with in-situ foaming. Water generated during the polycondensation process volatilizes at a specific temperature, acting as a foaming agent to form foam. No additional foaming agent is required, thus preparing an isocyanate-free starch-based polyurethane foam. By introducing starch, the foam exhibits good thermal insulation properties, controllable degradation performance, and low cost, reducing costs to a certain extent while increasing degradation performance. Furthermore, this preparation method does not require high temperatures or additional foaming agents, making it simple to operate. The polyurethane foam of this invention avoids the potential toxicity caused by the use of isocyanate raw materials, making it environmentally friendly.
[0041] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a starch-based polyurethane sprayable foam mulch film, characterized in that, Includes the following steps: (1) Preparation of carbamate starch Starch, urea and catalyst were added to a flask in a mass ratio of 1:(1-5):(0.01-0.05), stirred and heated to 150 degrees Celsius to melt the urea and dissolve the starch. The reaction was kept at a constant temperature for 4 hours. After the reaction was completed, the product was washed multiple times with an alcohol-water mixture. The washed product was then dried to obtain carbamate starch. (2) Preparation of starch-based polyurethane foam mulch film The carbamate starch obtained in step (1) is mixed with surfactant, catalyst and aldehyde in a mass ratio of 1:(0.02-0.05):(0.01-0.07):(0.01-0.08). The mixture is heated to melt, and after the melt is mixed evenly, it is heated to 50-85℃ to carry out cross-linking reaction and in-situ foaming to obtain solid foam. The aldehyde is one or a mixture of glutaraldehyde, vanillin and cyclohexane-1,4-dicarboxaldehyde.
2. The method for preparing the starch-based polyurethane sprayable foam mulch film according to claim 1, characterized in that, In step (1), the starch is at least one of corn starch, potato starch and potato starch.
3. The method for preparing the starch-based polyurethane sprayable foam mulch film according to claim 1, characterized in that, In step (1), the catalyst is at least one of ammonium chloride, copper chloride, and stannous chloride.
4. The method for preparing the starch-based polyurethane sprayable foam mulch film according to claim 1, characterized in that, The surfactant mentioned in step (2) is dimethyl silicone oil, methyl phenyl silicone oil, methyl trifluoropropyl silicone oil or methyl vinyl silicone oil.
5. The method for preparing the starch-based polyurethane sprayable foam mulch film according to claim 1, characterized in that, The catalyst mentioned in step (2) is formic acid, phosphoric acid or ethyl phosphate.
6. The method for preparing the starch-based polyurethane sprayable foam mulch film according to claim 1, characterized in that, In step (2), the mass ratio of carbamate starch, surfactant, catalyst and aldehyde is 1:(0.02-0.05):(0.02-0.05):(0.03-0.05).
7. The method for preparing the starch-based polyurethane sprayable foam mulch film according to any one of claims 1-6, characterized in that, The starch-based polyurethane foam is a closed-cell foam and / or an open-cell foam.