Preparation method of starch-based polyurethane sprayable foam mulching film

Abstract

The invention belongs to the technical field of high polymer materials and green chemistry, and particularly discloses a preparation method of a starch-based polyurethane sprayable foam mulching film, which comprises the following steps: firstly, synthesizing carbamate starch by using starch, urea and a catalyst, blending the carbamate starch with aldehyde under the action of a surfactant and the catalyst to generate a polycondensation cross-linking reaction to obtain a starch-based polyurethane sprayable foam mulching film; the starch-based polyurethane foam with a carbamic acid ester structural unit is synthesized, the use of isocyanate is avoided, the potential toxicity caused by the use of an isocyanate raw material is avoided, the foam is green and environment-friendly and better meets the environment-friendly requirement, and by introducing the starch, the foam has good thermal insulation performance, controllable degradation performance and lower cost and is suitable for industrial production. The starch-based polyurethane sprayable foam mulching film has the advantages that the starch-based polyurethane sprayable foam mulching film is prepared by the aid of the method, the cost is reduced to a certain extent, the degradation performance is improved, in addition, the method is free of high temperature and additional foaming agents and simple to operate, and the mulching film prepared by the aid of the method is mainly applied to agricultural mulching films and is applicable to various terrains.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials and green chemistry, and specifically discloses a method for preparing a starch-based polyurethane sprayable foam ground film. Background Art

[0002] As a key element of the modern agricultural production system, mulching technology has become an important guarantee for my country's food security. This technology can greatly increase food production capacity by precisely controlling the soil water and heat environment. Therefore, the development of environmentally friendly and biodegradable mulch materials has become a strategic focus of my country's green agricultural transformation.

[0003] At present, biodegradable mulch materials mainly include synthetic polymers and natural polymer materials. Synthetic polymer materials, such as polylactic acid (PLA), polybutylene succinate (PBS), polybutylene terephthalate-adipate (PBAT), etc., have basic mechanical properties, but there are application bottlenecks such as uncontrollable degradation rate and high cost; natural polymer materials are represented by starch and cellulose. Although they have significant environmental advantages and low cost, they are water-sensitive due to hydroxyl groups and are difficult to meet the mechanical strength requirements of mulch. Technological breakthroughs require collaborative innovation in dimensions such as material modification, processing technology and degradation mechanism. The new sprayable liquid mulch technology achieves functional integration breakthroughs through nozzle atomization and low-temperature film-forming technology: ① Using biodegradable polymers as raw materials, it can form a uniform film layer after curing with atomization 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 landforms such as hills and slopes.

[0004] In recent years, the concept of sprayable foam mulch has been proposed. Compared with the above-mentioned types of mulch, polyurethane (PU) foam mulch has achieved a leap in thermodynamic properties on its basis. In addition, it can be given multifunctional properties such as flexibility, rigidity, lightness, wear resistance and biodegradability through structural unit design. However, most of the raw materials of traditional polyurethane foams come from petrochemical resources or are formed by the reaction of polyisocyanates with compounds containing active hydrogen. Landfill and incineration after disposal will cause ecological pollution. Moreover, polyisocyanates and their preparation raw material phosgene are highly toxic substances, which are harmful to the environment and human health. Both production and use may cause harm to the human body. At present, most studies use bio-based polyols to construct PU to increase the bio-based content. Although the PU industry continues to work hard to improve the quality of PU raw materials, for example, using bio-based diisocyanates from natural resources, more environmentally friendly processes are urgently needed to address the renewability of starting materials and the sustainability of synthesis. Summary of the invention

[0005] In order to solve the problems in the background technology, the present invention discloses a method for preparing a starch-based polyurethane sprayable foam mulch, aiming to solve the isocyanate toxicity problem in the traditional polyurethane foam preparation process and develop a low-cost, degradable and thermally insulating polyurethane foam mulch that does not contain isocyanate.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical solutions: A method for preparing a starch-based polyurethane sprayable foam ground film, characterized in that it comprises the following steps: (1) Preparation of carbamate starch Starch, urea and catalyst are added into a flask in a certain mass ratio, stirred, heated to 150 degrees, urea is melted and starch is dissolved, and the reaction is carried out at a constant temperature for 4 hours. After the reaction is completed, the product is washed several times with a mixed solution of alcohol and water, and the washed product is dried to obtain carbamate starch; (2) Preparation of starch-based polyurethane foam mulch The carbamate starch obtained in step (1) is mixed with a surfactant, a catalyst and an aldehyde in a certain mass ratio, heated to melt, and after the melt is evenly mixed, the temperature is raised to a certain temperature to carry out a cross-linking reaction and in-situ foaming to obtain a solid foam.

[0007] Furthermore, in the method for preparing the starch-based polyurethane sprayable foam mulch, the starch in step (1) is at least one of corn starch, potato starch and potato starch.

[0008] Furthermore, in the method for preparing the starch-based polyurethane sprayable foam mulch, the catalyst in step (1) is at least one of ammonium chloride, cupric chloride and stannous chloride.

[0009] Furthermore, in the method for preparing the starch-based polyurethane sprayable foam mulch, the mass ratio of starch, urea and catalyst in step (1) is 1: (1-5): (0.01-0.05).

[0010] Furthermore, in the method for preparing the starch-based polyurethane sprayable foam mulch, the surfactant in step (2) is dimethyl silicone oil, methylphenyl silicone oil, methyltrifluoropropyl silicone oil or methylvinyl silicone oil.

[0011] Furthermore, in the method for preparing the starch-based polyurethane sprayable foam mulch, the catalyst in step (2) is formic acid, phosphoric acid or ethyl phosphate.

[0012] Furthermore, in the method for preparing the starch-based polyurethane sprayable foam mulch, the aldehyde in step (2) is a mixture of one or more of glutaraldehyde, benzaldehyde, vanillin, cyclohexane-1,4-dicarboxaldehyde and furanaldehyde.

[0013] Furthermore, in the method for preparing the starch-based polyurethane sprayable foam mulch, the mass ratio of carbamate starch, surfactant, catalyst and aldehyde in step (2) is 1: (0.02-0.05): (0.01-0.07): (0.01-0.08).

[0014] Furthermore, in the method for preparing the starch-based polyurethane sprayable foam mulch, the mass ratio of carbamate starch, surfactant, catalyst and aldehyde in step (2) is 1: (0.02-0.05): (0.02-0.05): (0.03-0.05).

[0015] Furthermore, the starch-based polyurethane sprayable foam ground film is prepared in a method, wherein the starch-based polyurethane foam is a closed-cell foam and / or an open-cell foam.

[0016] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: The invention discloses a method for preparing a starch-based polyurethane sprayable foam mulch film. The method comprises the following steps: firstly, carbamate starch is synthesized by using starch, urea and a catalyst. The carbamate starch is mixed with aldehyde under the action of a surfactant and a catalyst to undergo a polycondensation cross-linking reaction. The cross-linking reaction is synchronized with in-situ foaming. Water generated during the polycondensation volatilizes at a specific temperature to act as a foaming agent, thereby forming foam. No additional foaming agent is required. The starch-based polyurethane foam having a carbamate structural unit is synthesized, the use of isocyanate is avoided, and the potential toxicity caused by the use of isocyanate raw materials is avoided. The method is green and environmentally friendly and better meets environmental protection requirements. By introducing starch, the foam has good thermal insulation performance, controllable degradation performance and low cost, which reduces the cost to a certain extent and increases the degradation performance. In addition, the preparation method does not require high temperature and does not require additional foaming agent, and is simple to operate. The mulch film prepared according to the preparation method of the starch-based polyurethane sprayable foam mulch film disclosed by the invention is mainly used for agricultural mulch film and is suitable for various terrains. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a picture of the starch-based polyurethane sprayable foam mulch prepared in Example 5 of the present invention; Figure 2 This is a picture of the polyurethane sprayable foam ground film prepared in Comparative Example 1 of the present invention; Figure 3 is an infrared image of starch, urea and carbamate starch in Example 5 of the present invention; Figure 4 It is the XRD diagram of starch and carbamate starch in Example 5 of the present invention. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0019] The raw materials, reagents, etc. used in the examples and comparative examples without indicating the manufacturer are all conventional products that can be purchased commercially. The chemical raw materials used in the following examples are all commercially available, chemically pure reagents. Example 1

[0020] Corn starch, urea and ammonium chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:1:0.01, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, dimethyl silicone oil, ethyl phosphate and glutaraldehyde are mixed in a mass ratio of 1:0.02:0.01:0.01, and then foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch without isocyanate. Example 2

[0021] Potato starch, urea and copper chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:1:0.01, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, methyl vinyl silicone oil, phosphoric acid and glutaraldehyde are mixed evenly in a mass ratio of 1:0.02:0.01:0.01, and then foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch without isocyanate. Example 3

[0022] Potato starch, urea and stannous chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:1:0.01, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, methylphenyl silicone oil, formic acid and glutaraldehyde are mixed evenly in a mass ratio of 1:0.02:0.01:0.01, and then foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanate. Example 4

[0023] Corn starch, urea and ammonium chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:3:0.03, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, dimethyl silicone oil, ethyl phosphate and glutaraldehyde are mixed evenly in a mass ratio of 1:0.02:0.01:0.01, and then foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanate. Example 5

[0024] Corn starch, urea and ammonium chloride were added into a three-necked flask with mechanical stirring in a mass ratio of 1:3:0.03, heated to 150°C, and the reaction was continued for 4 hours after the urea was completely melted. After the reaction was completed, it was washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch. The infrared images of starch, urea and carbamate starch are shown in Figure 3 As shown, the XRD patterns of starch and carbamate starch are as follows Figure 4 As shown; carbamate 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°C-85°C to obtain a starch-based polyurethane sprayable foam film without isocyanate, such as Figure 1 shown. Example 6

[0025] Corn starch, urea and ammonium chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:5:0.05, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, dimethyl silicone oil, ethyl phosphate and glutaraldehyde are mixed evenly in a mass ratio of 1:0.05:0.03:0.08, and then foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch film that does not contain isocyanate. Example 7

[0026] Corn starch, urea and ammonium chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:3:0.02, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, methyl trifluoropropyl silicone oil, ethyl phosphate and benzaldehyde are mixed evenly in a mass ratio of 1:0.05:0.03:0.04, and then foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch without isocyanate. Example 8

[0027] Corn starch, urea and ammonium chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:5:0.02, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, methyl trifluoropropyl silicone oil, ethyl phosphate and cyclohexane-1,4-dicarboxaldehyde are mixed in a mass ratio of 1:0.05:0.07:0.04, and then foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch without isocyanate. Example 9

[0028] Corn starch, urea and ammonium chloride were added into a three-necked flask with mechanical stirring in a mass ratio of 1:3:0.05, heated to 150°C, and the reaction was continued for 4 hours after the urea was completely melted. After the reaction was completed, it was washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, methyl vinyl silicone oil, ethyl phosphate and vanillin were mixed evenly in a mass ratio of 1:0.03:0.04:0.05, and then foamed at 85°C to obtain a starch-based polyurethane sprayable foam mulch without isocyanate. Example 10

[0029] Potato starch, urea and copper chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:3:0.05, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, methylphenyl silicone oil, phosphoric acid and furfural are mixed evenly in a mass ratio of 1:0.03:0.04:0.05, and then foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch without isocyanate. Embodiment 11

[0030] Potato starch, urea and stannous chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:3:0.04, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, methyl vinyl silicone oil, ethyl phosphate and cyclohexane-1,4-dicarboxaldehyde are mixed evenly in a mass ratio of 1:0.03:0.04:0.05, and then foamed at 50°C-85°C to obtain a starch-based polyurethane sprayable foam mulch without isocyanate. Comparative Example 1

[0031] Corn starch, urea and ammonium chloride are added into a three-necked flask with mechanical stirring in a mass ratio of 1:3:0.04, heated to 150°C, and after the urea is completely melted, the reaction is continued for 4 hours. After the reaction is completed, it is washed three times with a mixed solution of alcohol and water in a mass ratio of 7:3, and dried to obtain carbamate starch; carbamate starch, methyl vinyl silicone oil, ethyl phosphate, and diphenylmethane diisocyanate are mixed in a mass ratio of 1:0.05:0.03:0.04 and foamed at 50°C to obtain a polyurethane foam film, such as Figure 2 shown.

[0032] The foaming conditions of the above Examples 1-11 and the comparative example are shown in Table 1 below.

[0033] Table 1 Foaming conditions of the examples and comparative examples project Can foaming Is there any isocyanate? Cell morphology Example 1 able none More uniform, with large and small pores Example 2 able none More uniform, with large and small pores Example 3 able none More uniform, with 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 Uniform Example 8 able none More large holes Example 9 able none Uniform Example 10 able none Uniform Embodiment 11 able none Uniform Comparative Example 1 able have Uneven, with collapse According to the experimental results in Table 1, Examples 4, 5 and 9-11 use different types of starch to prepare carbamate starch, and the carbamate starch and aldehyde undergo condensation cross-linking reaction to successfully prepare starch-based polyurethane foam that does not contain isocyanate; According to Examples 1-3 and Examples 6 and 8, it can be seen that the amount of urea and catalyst has a great influence on the pore morphology, therefore, it is necessary to select appropriate amounts of urea and catalyst; Compared with Comparative Example 1, Examples 1-11 have more uniform pores, which may be due to the excessively fast reaction rate of diphenylmethane diisocyanate under the action of the catalyst.

[0034] In summary, the present invention develops a method for preparing a low-cost, degradable and heat-insulating isocyanate-free polyurethane foam mulch film. The embodiment adopts a variety of carbamate starches and different types of aldehydes for polycondensation. The carbamate starch and aldehyde polycondensation cross-linking reaction is synchronized with in-situ foaming. The water generated during the polycondensation volatilizes at a specific temperature to act as a foaming agent, thereby forming foam. No additional foaming agent is required. A starch-based polyurethane foam without isocyanate is prepared. By introducing starch, the foam has good heat-insulating properties, controllable degradation performance and low cost, which reduces the cost to a certain extent and increases the degradation performance. In addition, the preparation method does not require high temperature, and does not require additional foaming agent, and is simple to operate. The polyurethane foam of the present invention avoids the potential toxicity caused by the use of isocyanate raw materials, and is green and environmentally friendly.

[0035] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A method for preparing a starch-based polyurethane sprayable foam film, characterized in that: The steps include: (1) Preparation of carbamate starch Starch, urea and catalyst are added into a flask in a certain mass ratio, stirred, heated to 150 degrees, urea is melted and starch is dissolved, and the reaction is carried out at a constant temperature for 4 hours. After the reaction is completed, the product is washed several times with a mixed solution of alcohol and water, and the washed product is dried to obtain carbamate starch; (2) Preparation of starch-based polyurethane foam mulch The carbamate starch obtained in step (1) is mixed with a surfactant, a catalyst and an aldehyde in a certain mass ratio, heated to melt, and after the melt is evenly mixed, the temperature is raised to a certain temperature to carry out a cross-linking reaction and in-situ foaming to obtain a solid foam.

2. The method for preparing the starch-based polyurethane sprayable foam mulch 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 according to claim 1, characterized in that: The catalyst in step (1) is at least one of ammonium chloride, cupric chloride and stannous chloride.

4. The method for preparing the starch-based polyurethane sprayable foam mulch according to claim 1, characterized in that: The mass ratio of starch, urea and catalyst in step (1) is 1:(1-5):(0.01-0.05).

5. The method for preparing the starch-based polyurethane sprayable foam mulch according to claim 1, characterized in that: The surfactant in step (2) is dimethyl silicone oil, methylphenyl silicone oil, methyltrifluoropropyl silicone oil or methylvinyl silicone oil.

6. The method for preparing the starch-based polyurethane sprayable foam mulch according to claim 1, characterized in that: The catalyst in step (2) is formic acid, phosphoric acid or ethyl phosphate.

7. The method for preparing the starch-based polyurethane sprayable foam mulch according to claim 1, characterized in that: In step (2), the aldehyde is a mixture of one or more of glutaraldehyde, benzaldehyde, vanillin, cyclohexane-1,4-dicarboxaldehyde and furanaldehyde.

8. The method for preparing the starch-based polyurethane sprayable foam ground 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): (0.01-0.07): (0.01-0.08).

9. The method for preparing the starch-based polyurethane sprayable foam mulch 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).

10. The method for preparing the starch-based polyurethane sprayable foam ground film according to any one of claims 1 to 9, characterized in that: The starch-based polyurethane foam is a closed-cell foam and / or an open-cell foam.

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