A reactive controlled-release chlorine dioxide composite film and its preparation method

Abstract

The present invention discloses a preparation method of a reactive controlled-release chlorine dioxide composite film, the preparation method comprising the following steps: under an inert atmosphere, a soft segment compound and 2,2-dimethylol propionic acid are added in a non-polar solvent, heated and stirred at 50-65 DEG C, a hard segment compound and a catalyst are added, and the reaction is stirred at 70-85 DEG C for 3-4h; the polyurethane emulsion is obtained; sodium chlorite particles are added to the polyurethane emulsion, fully stirred, cast into a mold, put into a 26-35 DEG C baking oven to constant weight film formation, and the reactive controlled-release chlorine dioxide composite film is obtained. The present invention uses sodium chlorite particles, and it is not necessary to prepare chlorine dioxide gas in advance, and complicated preparation technology can be simplified. By controlling the mesh number and ambient humidity of the sodium chlorite particles, the chlorine dioxide release rate can be effectively controlled, and controlled release is convenient and effective.

Description

Technical Field

[0001] The present invention relates to the field of antibacterial materials, and in particular to a reactive controlled-release chlorine dioxide composite film and a preparation method thereof. Background Art

[0002] my country has a large production of fruits and vegetables, but its preservation is still lagging behind. The annual rot rate for fruits and vegetables is 25-30%, compared to less than 5% in developed countries. In developed countries like the Netherlands and the United States, over 90% of fruits and vegetables are stored in controlled atmosphere storage. With the increasing importance of disinfection and sterilization in public places, both fruit and vegetable preservation and disinfection require continuous, long-term maintenance. Therefore, a long-lasting, controlled-release disinfectant product is needed to address this issue.

[0003] Sustained-release and controlled-release technologies are widely used in the medical field. The Chinese Pharmacopoeia clearly defines sustained-release and controlled-release as follows: sustained-release preparations refer to oral medications that are released slowly, at a non-constant rate, in a specified solvent; controlled-release preparations refer to oral medications that are released slowly, at a constant or near-constant rate, in a specified solvent. Sustained-release and controlled-release technologies can reduce dosing frequency and address the issue of burst release, thereby prolonging the duration of action. This technology can be well combined with sterilization and preservation technologies to develop sustained-release and controlled-release disinfection and preservation products, thereby extending the effectiveness of disinfection and preservation.

[0004] Among all disinfection and sterilization technologies, chlorine dioxide is widely used in fields such as fruit and vegetable preservation, formaldehyde removal, and the papermaking industry due to its strong bactericidal effect, strong ability to oxidize organic matter, and wide applicable pH range. It is particularly widely used in food preservation. However, chlorine dioxide also has certain drawbacks during use. For example, gaseous chlorine dioxide is easily decomposed by light or heat, making it difficult to store and transport, and often requires on-site preparation. Liquid chlorine dioxide, on the other hand, is less stable, easily decomposes by light, and has low concentrations. Solid chlorine dioxide products, on the other hand, are easy to store and transport, have stable properties, and often have slow-release and controlled-release effects. However, solid chlorine dioxide products currently still have some unresolved issues, such as complex preparation, prone to burst release in the early stages of slow-release, small total slow-release amount, and large fluctuations in release rate. Other researchers have mostly used aqueous chlorine dioxide or sodium chlorite solutions to prepare slow-release chlorine dioxide materials, coupled with complex preparation processes, resulting in low material release per unit mass and uncontrollable release rate, which to some extent limits the yield and duration of chlorine dioxide.

[0005] There are also public applications for preparing slow-release chlorine dioxide films by mixing waterborne polyurethane with a chlorine dioxide aqueous solution. For example, patent application number CN202010532685.X, entitled "A Slow-Release Chlorine Dioxide-Waterborne Polyurethane Antibacterial Film and Its Preparation Method," discloses a slow-release chlorine dioxide-waterborne polyurethane antibacterial film and its preparation method. The process involves two major steps: the first step is the synthesis of an aqueous polyurethane dispersion containing a hard segment, a soft segment, 2,2-dimethylolpropionic acid, triethylamine, acetone, and the catalyst dibutyltin dilaurate; the second step is the preparation of the chlorine dioxide-waterborne polyurethane antibacterial film. A stable chlorine dioxide aqueous solution is added to the dispersion, and the slow-release chlorine dioxide-waterborne polyurethane antibacterial film is prepared by casting. This patent uses carboxylic acid as an acidic activator that reacts with chlorine dioxide, producing chlorine dioxide gas, which imparts antibacterial properties to the film. The release of chlorine dioxide gas is also controlled by the release of carboxylic acid from the film, achieving a certain slow-release effect. The patent adds triethylamine to protect the carboxyl groups in 2,2-dimethylolpropionic acid. After adding triethylamine, the film produced will generate ammonia gas due to the removal of amino groups when generating chlorine dioxide, causing air pollution and increasing production costs. The chlorine dioxide gas in this patent is entirely derived from the added chlorine dioxide aqueous solution. The preparation of the chlorine dioxide aqueous solution undoubtedly further increases the process complexity of preparing the material. Furthermore, the chlorine dioxide concentration in the chlorine dioxide aqueous solution is low and unstable, resulting in a low concentration of chlorine dioxide released. Summary of the Invention

[0006] In order to address the deficiencies in the prior art, the present invention aims to provide a reactive controlled-release chlorine dioxide composite film and its preparation method that has a simple preparation process, avoids the explosive release of chlorine dioxide, is environmentally friendly, generates no by-products during the reaction process, and achieves long-lasting antibacterial and fresh-keeping effects.

[0007] The technical solution of the present invention is: a method for preparing a reactive controlled-release chlorine dioxide composite film, the preparation method comprising the following steps:

[0008] Step 1) preparing a polyurethane emulsion: under an inert atmosphere, adding a soft segment compound and 2,2-dimethylolpropionic acid to a non-polar solvent, heating and stirring at 50-65° C. to obtain a mixed solution; then adding a hard segment compound and a catalyst to the mixed solution, continuing to heat until the temperature in the container rises to 80° C., and starting condensation and reflux; then stirring and reacting at 70-85° C. for 3-4 hours; after the reaction is completed, stopping heating and cooling to room temperature to obtain the polyurethane emulsion; the mass of the 2,2-dimethylolpropionic acid accounts for 6%-10% of the total mass of the solute, and the mass of the non-polar solvent is 150%-200% of the total mass of the solute; the ratio of the sum of the amount of the soft segment compound and the 2,2-dimethylolpropionic acid to the amount of the hard segment compound is 1:1.4; the mass of the catalyst accounts for 1%-2% of the total mass of the solute; the solute includes a soft segment compound, 2,2-dimethylolpropionic acid and a hard segment unit;

[0009] Step 2) adding 250-300 mesh sodium chlorite particles to the polyurethane emulsion obtained in step 1), wherein the mass of the added sodium chlorite particles is 5%-20% of the mass of the polyurethane emulsion, stirring thoroughly, casting into a mold, and placing in an oven at 26-35° C. until constant weight is formed into a film, thereby obtaining the reactive controlled-release chlorine dioxide composite film.

[0010] Preferably, the non-polar solvent is one of cyclohexane, n-hexane, dichloromethane, acetone, toluene, chloroform, and methanol, or a mixture of two or more thereof.

[0011] Preferably, the soft segment compound comprises one or more of the following: polytetramethylene ether glycol, polypropylene glycol, vinyl polymer grafted polyether polyol, polyethylene glycol. Among them, polytetramethylene ether glycol with a molecular weight of 2000 or polytetramethylene ether glycol with a molecular weight of 1000 can be selected.

[0012] Preferably, the hard segment compound includes one or more of the following: isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

[0013] Preferably, the catalyst is one of the following: dibutyltin dilaurate, stannous octoate, lead octoate, etc.

[0014] The invention also discloses a reactive controlled-release chlorine dioxide composite film, which is prepared by the above preparation method.

[0015] In the present invention, the 2,2-dimethylolpropionic acid in the polyurethane contains a carboxyl group. The carboxyl group can ionize hydrogen ions when there is water, and is provided as a weak acid required for chlorine dioxide generation. The polyurethane can provide a polymer carrier for the sodium chlorite particles simultaneously. When the film prepared by the present invention absorbs moisture in the air, water vapor begins to penetrate from the top of the film, and first contacts the carboxylic acid group in the 2,2-dimethylolpropionic acid at the top of the film. The water vapor reacts with the carboxylic acid in the composite film, and the carboxyl group ionizes hydrogen ions, so that the sporadic sodium chlorite particles at the top of the film are decomposed into chlorine dioxide under weak acid conditions. The water vapor then gradually penetrates downwards and contacts the sodium chlorite particle group inside the film, causing sodium chlorite and the carboxyl group to react and generate chlorine dioxide. The composite film gradually begins to release chlorine dioxide, and until the sodium chlorite particles are fully reacted, the chlorine dioxide release stops. As water vapor slowly penetrates downward, carboxylic acid reacts with sodium chlorite particles to release chlorine dioxide. By controlling the water vapor content in the environment, that is, controlling the air humidity, the speed of chlorine dioxide release can be controlled. This not only effectively controls the release rate of chlorine dioxide, but also avoids the explosive release of chlorine dioxide.

[0016] At the same time, by controlling the order of the sodium chlorite granules to 250-300 orders, the chlorine dioxide release rate can be well controlled. Because when the order of the sodium chlorite granules exceeds 300, the chlorine dioxide release rate is not significantly different from that of the 250-300 orders, but this increases the preparation cost and process difficulty. Conversely, when the order of the sodium chlorite granules is less than 250, the particle size of the sodium chlorite is uneven and the particles are larger, causing large fluctuations in the reaction rate. Therefore, the present invention has found through a large number of experiments that the controlled release effect is best when the sodium chlorite granules are 250-300 orders.

[0017] When sodium chlorite particles are dissolved in a polar solvent, they ionize to produce hydrogen ions, leading to premature release of chlorine dioxide during film preparation, significantly reducing the controlled-release effect of chlorine dioxide. Therefore, the polyurethane emulsion of the present invention uses a non-polar organic solvent as the reaction solvent. Dimethylolpropionic acid does not ionize to produce hydrogen ions, thus preventing premature reaction between dimethylolpropionic acid and sodium chlorite particles to release chlorine dioxide during film preparation, effectively improving the controlled-release effect and amount of chlorine dioxide released.

[0018] The raw materials for preparing the polyurethane emulsion of the present invention do not require the addition of a small molecule chain extender and triethylamine. By increasing the content of 2,2-dimethylolpropionic acid, the carboxyl groups are retained to the greatest extent. The addition of triethylamine will protect the carboxyl groups, making it inconvenient for the carboxyl groups to react with sodium chlorite. Without the addition of triethylamine, the carboxyl groups are fully exposed, making the reaction with sodium chlorite convenient, and the amount of chlorine dioxide generated is closest to the theoretical calculated value, which not only facilitates the subsequent release of chlorine dioxide but also greatly increases the total amount of chlorine dioxide released. Because chlorine dioxide is generated by the reaction of acid and sodium chlorite, simply increasing the amount of sodium chlorite cannot increase the total amount of chlorine dioxide generated. Therefore, when preparing a film, the content of the acid (2,2-dimethylolpropionic acid) in the film must also be correspondingly increased.

[0019] The present invention uses water to trigger the reaction between sodium chlorite particles and carboxylic acid to release chlorine dioxide. The reaction process requires water and has low requirements on the physical form of the material. It tends to expose more carboxyl groups. Therefore, the present invention does not need to add triethylamine to protect the carboxyl groups, avoids the production of ammonia during the chlorine dioxide release process, and is more environmentally friendly.

[0020] In the present invention, the mass of the 2,2-dimethylolpropionic acid accounts for 6%-10% of the total mass of the solute. By increasing the dosage of the 2,2-dimethylolpropionic acid, the carboxyl content in the film is increased, thereby achieving the purpose of increasing the total amount of chlorine dioxide released.

[0021] The beneficial technical effects of the present invention are:

[0022] 1. Sodium chlorite particles are used to prepare reactive controlled-release chlorine dioxide composite films. There is no need to prepare chlorine dioxide gas in advance, which can simplify the complex preparation process.

[0023] 2. The present invention can effectively control the release rate of chlorine dioxide by controlling the mesh size of sodium chlorite particles and the ambient humidity, and the controlled release is convenient and effective.

[0024] 3. No triethylamine or small molecule chain extenders are required when preparing the polyurethane emulsion, facilitating subsequent reactions and preventing the generation of byproducts such as ammonia, making it environmentally friendly. Furthermore, by increasing the amount of 2,2-dimethylolpropionic acid added, sufficient carboxyl groups are ensured to react with the sodium chlorite particles, increasing the release of chlorine dioxide.

[0025] 4. When preparing polyurethane emulsion, compared with other organic solvents, the use of non-polar solvents can effectively prevent the reaction between 2,2-dihydroxymethylpropionic acid and sodium chlorite particles to produce chlorine dioxide gas during the film preparation process, thereby retaining the slow-release amount of chlorine dioxide to the greatest extent.

[0026] 5. From the perspective of product performance: the reactive controlled-release chlorine dioxide composite film prepared by the present invention greatly improves the mechanical properties, chlorine dioxide release amount and stable release rate of the film, broadens the application range of the controlled-release chlorine dioxide composite film, completely solves the problem of burst release, and achieves a slow-release and controlled-release effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A plan view of the composite film prepared in Example 1;

[0028] Figure 2 This is a cross-sectional view of the composite film prepared in Example 1;

[0029] Figure 3 Total amount of chlorine dioxide released by polyurethane films with different sodium chlorite particle sizes in Examples 3 and 5-6

[0030] Figure 4 The total amount of chlorine dioxide released by the polyurethane films of Examples 1-4 with different amounts of sodium chlorite added. DETAILED DESCRIPTION

[0031] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation methods.

[0032] Example 1

[0033] Example 1-1 A method for preparing a polyurethane emulsion

[0034] 1) In a 500 ml round-bottom four-necked flask equipped with a digital stirrer, a temperature control device, and a nitrogen protective gas, 34.7416 g (0.0174 mol) of polytetrahydrofuran ether glycol (Mn=2000) and 4.3723 g (0.0326 mol) of 2,2-dimethylolpropionic acid were added, the stirrer speed was adjusted to 300 r / min, and 109 g of cyclohexane was added while stirring; after connecting a serpentine condenser, the heating temperature was controlled between 50-60° C. by the temperature control device, and heated and stirred for 10 minutes; after the insulation reaction was completed, when the solution in the four-necked flask became white and viscous, the resulting solution was marked as T;

[0035] 2) To the mixture T obtained in a four-necked flask, 15.56 g (0.07 mol) of isophorone diisocyanate and 1.09 g of a catalyst (dibutyltin dilaurate) were added. When the temperature in the container rose to 80°C, condensation and reflux were initiated. A second heating and stirring process was performed at a heating temperature of 70-85°C. After condensation and reflux for 4 hours, the mixture was cooled to obtain a polyurethane emulsion.

[0036] Example 1-2

[0037] The polyurethane emulsion obtained in Example 1-1 is used to further prepare a reactive controlled-release chlorine dioxide composite film, comprising the following steps:

[0038] 1) Dry the sodium chlorite granules in an oven at 50°C for 24 hours to fully remove moisture. Grind the dried sodium chlorite granules in a mortar and pass through a 250-300 mesh sieve;

[0039] 2) Use a beaker to take 0.5g (0.0055mol) of ground and sieved sodium chlorite particles, and then take 10g

[0040] The polyurethane emulsion prepared in Example 1 was stirred thoroughly until milky white, and then poured into a horizontally placed circular polytetrafluoroethylene mold. The film was formed in an oven at 30°C until constant weight was obtained to obtain a reactive controlled-release chlorine dioxide composite film, the plan view of which is shown in FIG. Figure 1 As shown, its cross-section is as follows Figure 2 shown.

[0041] Example 2

[0042] Example 2-1 A method for preparing a polyurethane emulsion

[0043] 1) In a 500 ml round-bottom four-necked flask equipped with a digital stirrer, a temperature control device, and Ar protective gas, 34.7416 g (0.0174 mol) of polytetrahydrofuran ether glycol (Mn=2000) and 4.3723 g (0.0326 mol) of 2,2-dimethylolpropionic acid were added, the stirrer speed was adjusted to 300 r / min, and 109 g of cyclohexane was added while stirring; after connecting a serpentine condenser, the heating temperature was controlled between 55-65° C. by the temperature control device, and heated and stirred for 10 minutes; after the reaction was completed, when the solution in the four-necked flask became white and viscous, the resulting solution was marked as T;

[0044] 2) To the mixture T obtained in a four-necked flask, 15.56 g (0.07 mol) of isophorone diisocyanate and 0.55 g of a catalyst (dibutyltin dilaurate) were added. When the temperature in the container rose to 80°C, reflux was initiated. A second heating and stirring process was performed at a heating temperature of 70-85°C. After reflux for 4 hours, the mixture was cooled to obtain a polyurethane emulsion.

[0045] Example 2-2

[0046] The polyurethane emulsion obtained in Example 2-1 is used to further prepare a reactive controlled-release chlorine dioxide composite film, comprising the following steps:

[0047] 1) Dry the sodium chlorite granules in an oven at 50°C for 24 hours to fully remove moisture. Grind the dried sodium chlorite granules in a mortar and pass through a 250-300 mesh sieve;

[0048] 2) Using a beaker, 1 g of ground and sieved sodium chlorite particles was taken, and then 10 g of the polyurethane emulsion prepared in Example 1 was taken. The two were thoroughly stirred until milky white, and then poured into a horizontally placed circular polytetrafluoroethylene mold. The mixture was dried in a 30°C oven until constant weight was reached to form a film, thereby obtaining a reactive controlled-release chlorine dioxide composite film.

[0049] Example 3

[0050] Example 3-1 A method for preparing a polyurethane emulsion

[0051] 1) In a 500 ml round-bottom four-necked flask equipped with a digital stirrer, a temperature control device, and Ar protective gas, 34.7416 g (0.0174 mol) of polytetrahydrofuran ether glycol (Mn=2000) and 4.3723 g (0.0326 mol) of 2,2-dimethylolpropionic acid were added, the stirrer speed was adjusted to 300 r / min, and 97 g of cyclohexane was added while stirring; after connecting a serpentine condenser, the heating temperature was controlled between 50-60° C. by the temperature control device, and heated and stirred for 10 minutes; after the reaction was completed, when the solution in the four-necked flask became white and viscous, the resulting solution was marked as T;

[0052] 2) To the mixture T obtained in a four-necked flask, 15.56 g (0.07 mol) of isophorone diisocyanate and 0.55 ml of a catalyst (dibutyltin dilaurate) were added. When the temperature in the container rose to 80°C, reflux was initiated. A second heating and stirring process was performed at a heating temperature of 70-85°C. After reflux for 4 hours, the mixture was cooled to obtain a polyurethane emulsion.

[0053] Example 3-2

[0054] The polyurethane emulsion obtained in Example 3-1 was used to further prepare a reactive controlled-release chlorine dioxide composite film, comprising the following steps:

[0055] 1) Dry the sodium chlorite granules in an oven at 50°C for 24 hours to fully remove moisture. Grind the dried sodium chlorite granules in a mortar and pass through a 250-300 mesh sieve;

[0056] 2) Using a beaker, 1.5 g of ground and sieved sodium chlorite particles was taken, and then 10 g of the polyurethane emulsion prepared in Example 1 was taken. The two were thoroughly stirred until milky white, and then poured into a horizontally placed circular polytetrafluoroethylene mold. The mixture was dried in a 30°C oven until constant weight was reached to form a film, thereby obtaining a reactive controlled-release chlorine dioxide composite film.

[0057] Example 4

[0058] The operation and experimental conditions of Example 4-1 are the same as those of Example 3-1. The difference between Example 4-2 and Example 3-2 is that the amount of sodium chlorite particles added is changed from 1.5 g to 2 g.

[0059] Example 5

[0060] The operation and experimental conditions of Example 5-1 are the same as those of Example 3-1. The difference between Example 5-2 and Example 3-2 is that the particle size of the added sodium chlorite particles is limited to 200-250 mesh.

[0061] Example 6

[0062] The operation and experimental conditions of Example 6-1 are the same as those of Example 3-1. The difference between Example 6-2 and Example 3-2 is that the particle size of the added sodium chlorite particles is limited to 300-350 mesh.

[0063] Example 7

[0064] Example 7-1 Preparation method of polyurethane emulsion

[0065] 1) In a 500 ml round-bottom four-necked flask equipped with a digital stirrer, a temperature control device, and a nitrogen protective gas, 43.6299 g (0.0218 mol) of polytetrahydrofuran ether glycol (Mn=2000) and 3.7768 g (0.0282 mol) of 2,2-dimethylolpropionic acid were added, the stirrer speed was adjusted to 300 r / min, and 126 g of cyclohexane was added while stirring; after connecting a serpentine condenser, the heating temperature was controlled between 50-60° C. by the temperature control device, and heated and stirred for 10 minutes; after the insulation reaction was completed, when the solution in the four-necked flask became white and viscous, the resulting solution was marked as T;

[0066] 2) To the mixture T obtained in a four-necked flask, 15.56 g (0.07 mol) of isophorone diisocyanate and 1.09 g of a catalyst (dibutyltin dilaurate) were added. When the temperature in the container rose to 80°C, condensation and reflux were initiated. A second heating and stirring process was performed at a heating temperature of 70-85°C. After condensation and reflux for 4 hours, the mixture was cooled to obtain a polyurethane emulsion.

[0067] The experimental conditions of Example 7-2 are consistent with those of Example 3-2, except that the polyurethane emulsion obtained in 7-1 is used to obtain a reactive controlled-release chlorine dioxide composite film.

[0068] Example 8

[0069] Example 8-1 A method for preparing a polyurethane emulsion

[0070] 1) In a 500 ml round-bottom four-necked flask equipped with a digital stirrer, a temperature control device, and a nitrogen protective gas, 27.9226 g (0.0139 mol) of polytetrahydrofuran ether glycol (Mn=2000) and 4.8292 g (0.0361 mol) of 2,2-dimethylolpropionic acid were added, the stirrer speed was adjusted to 300 r / min, and 97 g of cyclohexane was added while stirring; after connecting a serpentine condenser, the heating temperature was controlled between 50-60° C. by the temperature control device, and heated and stirred for 10 minutes; after the insulation reaction was completed, when the solution in the four-necked flask became white and viscous, the resulting solution was marked as T;

[0071] 2) To the mixture T obtained in a four-necked flask, 15.56 g (0.07 mol) of isophorone diisocyanate and 1.09 g of a catalyst (dibutyltin dilaurate) were added. When the temperature in the container rose to 80°C, condensation and reflux were initiated. A second heating and stirring process was performed at a heating temperature of 70-85°C. After condensation and reflux for 4 hours, the mixture was cooled to obtain a polyurethane emulsion.

[0072] The experimental conditions of Example 8-2 are consistent with those of Example 3-2, except that the polyurethane emulsion obtained in 8-1 is used to obtain a reactive controlled-release chlorine dioxide composite film.

[0073] Example 9

[0074] Example 9-1 A method for preparing a polyurethane emulsion

[0075] 1) In a 500 ml round-bottom four-necked flask equipped with a digital stirrer, a temperature control device, and a nitrogen protective gas, 34.7416 g (0.0174 mol) of polypropylene glycol (Mn=2000) and 4.3723 g (0.0326 mol) of 2,2-dimethylolpropionic acid were added. The stirrer speed was adjusted to 300 r / min, and 102 g of dichloromethane was added while stirring. After connecting a serpentine condenser, the heating temperature was controlled between 50-60° C. by the temperature control device, and heated and stirred for 10 minutes. After the reaction was completed, when the solution in the four-necked flask became white and viscous, the resulting solution was marked as T.

[0076] 2) To the obtained T in a four-necked flask, 12.19 g (0.07 mol) of toluene diisocyanate (TDI) and 1.09 g of a catalyst (stannous octoate) were added. When the temperature in the container rose to 80° C., condensation and reflux were started. A second heating and stirring was performed at a heating temperature of 70-85° C. After condensation and reflux for 4 hours, the mixture was cooled to obtain a polyurethane emulsion.

[0077] The experimental conditions of Example 9-2 are consistent with those of Example 3-2, except that the polyurethane emulsion obtained in Example 9-1 is used to obtain a reactive controlled-release chlorine dioxide composite film.

[0078] Example 10

[0079] Example 10-1 A method for preparing a polyurethane emulsion

[0080] 1) In a 500 ml round-bottom four-necked flask equipped with a digital stirrer, a temperature control device, and a nitrogen protective gas, 34.7416 g (0.0174 mol) of polyethylene glycol (PEG) (Mn=2000) and 4.3723 g (0.0326 mol) of 2,2-dimethylolpropionic acid were added, the stirrer speed was adjusted to 300 r / min, and 109 g of methanol was added while stirring; after connecting a serpentine condenser, the heating temperature was controlled between 50-60° C. by the temperature control device, and heated and stirred for 10 minutes; after the reaction was completed, when the solution in the four-necked flask became white and viscous, the resulting solution was marked as T;

[0081] 2) To the solution T obtained in a four-necked flask, 17.52 g (0.07 mol) of diphenylmethane diisocyanate (MDI) and 1.09 g of a catalyst (lead octoate) were added. When the temperature in the container rose to 80° C., condensation and reflux were initiated. A second heating and stirring process was performed at a heating temperature of 70-85° C. After condensation and reflux for 4 hours, the solution was cooled to obtain a polyurethane emulsion.

[0082] The experimental conditions of Example 10-2 are consistent with those of Example 3-2, except that the polyurethane emulsion obtained in Example 10-1 is used to obtain a reactive controlled-release chlorine dioxide composite film.

[0083] The reactive controlled-release chlorine dioxide composite films prepared in Examples 1-10 above were subjected to various performance tests. The conditions for the various performance tests were as follows:

[0084] 1. Mechanical properties test

[0085] The tensile strength and elongation at break of the film were tested using a universal tensile testing machine. Before testing, the film was cut into 5 cm × 1 cm rectangles, the tensile rate was set to 100 mm / min, and each sample was tested 3 times.

[0086] 2. Determination of chlorine dioxide release

[0087] Add 10 mL of 5% KI solution and 6 mL of 1 mol / L dilute sulfuric acid solution to a glass drying dish and place it at the bottom of the glass drying dish. Place composite films with NaClO2 added in amounts of 0.5, 1, 1.5, and 2 mg in the glass drying dish, respectively. Replace the glass dish every 24 hours and titrate the solution with sodium thiosulfate solution. Calculate the total amount of chlorine dioxide released by the film using Formula 2.

[0088]

[0089] Where: M—represents the mass of ClO2 (mg)

[0090] V1—indicates the volume of sodium thiosulfate consumed by the sample (mL)

[0091] V0—indicates the volume of sodium thiosulfate consumed by the blank sample (mL)

[0092] C—represents the mass fraction of sodium thiosulfate (mol / L)

[0093] The daily chlorine dioxide release of the controlled-release chlorine dioxide composite films prepared in Examples 1-10 was measured according to the above method.

[0094] According to the above experimental methods, the above tests were performed on the reactive controlled-release chlorine dioxide composite films prepared in Examples 1-10. The specific test data are shown in Table 1.

[0095] Table 1 Test data of controlled-release chlorine dioxide composite films prepared in various embodiments

[0096]

[0097]

[0098] As shown in Table 1, the tensile strength of the polyurethane composite films prepared in Examples 1-10 of the present invention is significantly improved compared to conventional polyurethane composite films. This is primarily due to the omission of triethylamine and small molecule chain extenders, as well as the increased 2,2-dimethylolpropionic acid content, which increases the proportion of hard segments in the polyurethane, thereby improving the tensile strength of the polyurethane composite films.

[0099] As can be seen from the test data of Examples 1 to 4, as the amount of sodium chlorite particles added increases from 0.5g to 1.5g, the chlorine dioxide release shows an upward trend, rising from 32mg to 105mg. When the amount of sodium chlorite particles added is 2g, the chlorine dioxide release decreases to some extent, dropping to 91mg. This shows that when the amount of sodium chlorite particles added is 1.5g (i.e., the mass of sodium chlorite particles added is 15% of the mass of the polyurethane emulsion), the chlorine dioxide release is the highest. At the same time, using the preparation method of the present invention, the chlorine dioxide release far exceeds other existing preparation methods. The total amount of chlorine dioxide released by the chlorine dioxide release film obtained by other preparation methods is generally 1-10mg. The release of chlorine dioxide is mainly caused by the reaction of sodium chlorite and acid. When the acid content is fixed and does not fully participate in the reaction, the increase of sodium chlorite can increase the release of chlorine dioxide.

[0100] From the test data of Example 3 (the particle size of the sodium chlorite particles is 250-300 mesh), Example 5 (the particle size of the sodium chlorite particles is 200-250 mesh), and Example 6 (the particle size of the sodium chlorite particles is 300-350 mesh), it can be seen that when the particle size of the sodium chlorite particles is 250-300 mesh, the chlorine dioxide release is the highest, reaching 105 mg. When the sodium chlorite particles use other particle sizes, the chlorine dioxide release is reduced. Because when the sodium chlorite particles have an order of more than 300, the chlorine dioxide release rate is not much different from that of 250-300 mesh, but it increases the preparation cost and process difficulty. Conversely, when the sodium chlorite particles have an order of less than 250, the particle size of the sodium chlorite is uneven and the particles are larger, resulting in large fluctuations in the reaction rate.

[0101] Therefore, the present invention has found through a large number of experiments that when the sodium chlorite particles are 250-300 mesh, the controlled release effect is best. The data of the daily chlorine dioxide release amount of Example 3, Example 5 and Example 6 are plotted. Figure 3 .from Figure 3 It can be seen that when the particle size of sodium chlorite is below 200 mesh, the daily release is not particularly stable. When the particle size of sodium chlorite is 250-300 mesh, the data dispersion decreases by 52%. This shows that when the particle size of sodium chlorite is above 250 mesh, the dispersion of the daily release can be significantly reduced. Therefore, when the particle size of sodium chlorite is increased to 250-300 mesh, the controlled release effect of the film on chlorine dioxide can be effectively achieved. Figure 3 It can be seen that the composite films prepared in Examples 3, 5 and 6 can basically achieve a steady and sustained release effect of chlorine dioxide, but the composite film prepared in Example 3 has the best steady and sustained release effect of chlorine dioxide.

[0102] From the test data of Example 3 (the mass of 2,2-dimethylol propionic acid is 8% of the total solute mass), Example 7 (the mass of 2,2-dimethylol propionic acid is 6% of the total solute mass), and Example 8 (the mass of 2,2-dimethylol propionic acid is 10% of the total solute mass), it can be seen that when the mass of 2,2-dimethylol propionic acid is 8% of the total solute mass, the chlorine dioxide release is the highest, reaching 105 mg. If the amount of 2,2-dimethylol propionic acid added is too low, the chlorine dioxide release decreases. After the mass of 2,2-dimethylol propionic acid is 8% of the total solute mass, the chlorine dioxide release does not continue to rise even if the amount of 2,2-dimethylol propionic acid added is increased. The main reason is that the solubility of 2,2-dimethylol propionic acid in non-polar solvents is poor, but its solubility in soft segment compounds is better. 2,2-dimethylol propionic acid mainly relies on the soft segment unit to dissolve in the reaction solution and participate in the reaction. During the polyurethane emulsion preparation process, the hydroxyl groups in 2,2-dimethylolpropionic acid react with the hydroxyl groups in the soft segment compound together with the isocyanate groups in the hard segment compound. To maintain an appropriate reaction ratio between the hydroxyl groups and the isocyanate groups in the reaction, increasing the content of 2,2-dimethylolpropionic acid inevitably reduces the content of the soft segment compound. However, a reduction in the amount of the soft segment compound affects the solubility of 2,2-dimethylolpropionic acid. Therefore, when the amount of 2,2-dimethylolpropionic acid added reaches a certain level, further increasing the amount of 2,2-dimethylolpropionic acid further reduces the soft segment compound, preventing 2,2-dimethylolpropionic acid from fully dissolving and further participating in the subsequent reaction with sodium chlorite. In the present invention, the amount of 2,2-dimethylolpropionic acid added can be higher than in conventional polyurethane emulsion reactions. However, after the weight of the added 2,2-dimethylolpropionic acid exceeds 8% of the total solute mass, increasing the amount of 2,2-dimethylolpropionic acid further has no significant effect on increasing the chlorine dioxide release rate. Therefore, the optimal addition mass of 2,2-dihydroxymethylpropionic acid is 8% of the total solute mass.

[0103] It can also be seen from Table 1 that the chlorine dioxide release time of the controlled-release chlorine dioxide composite films prepared in Examples 1-10 of the present invention is more than 23 days, and can be as long as 25 days. The release time is long, far exceeding that of existing chlorine dioxide films (the release time of existing films is generally 7-10 days). At the same time, the amount of chlorine dioxide released per day is tested, as shown in FIG. Figure 4(In order to clearly see the trend of the picture, the chlorine dioxide release data of the films prepared in Examples 1-4 were selected for plotting.) According to the daily chlorine dioxide release data, it can be seen that the composite films prepared in Examples 1-4 can achieve a steady sustained release of chlorine dioxide, with minimal fluctuation within the sustained release days, completely solving the problem of sudden release, and are expected to be applied in the fields of fruit and vegetable preservation, deodorization and sterilization. Among them, under the conditions of Example 3 (the particle size of the sodium chlorite particles is 250-300 mesh, the mass of the sodium chlorite particles added is 15% of the polyurethane emulsion, and the mass of 2,2-dimethylolpropionic acid is 8% of the total solute mass), the chlorine dioxide is steadily released, and the controlled release effect is the best.

[0104] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, based on the innovative concept of the present invention, changes and modifications to the embodiments described herein, or equivalent structural or equivalent process transformations made using the contents of the present invention specification, and direct or indirect application of the above technical solutions to other related technical fields are all included in the scope of patent protection of the present invention.

Claims

1. A method for preparing a reactive controlled-release chlorine dioxide composite film, characterized in that: The preparation method comprises the following steps: Step 1) preparing a polyurethane emulsion: under an inert atmosphere, adding a soft segment compound and 2,2-dimethylolpropionic acid to a non-polar solvent, heating and stirring at 50-65° C. to obtain a mixed solution; then adding a hard segment compound and a catalyst to the mixed solution, continuing to heat until the temperature in the container rises to 80° C., and starting condensation and reflux; then stirring and reacting at 70-85° C. for 3-4 hours; after the reaction is completed, stopping heating and cooling to room temperature to obtain the polyurethane emulsion; the mass of the 2,2-dimethylolpropionic acid accounts for 6%-10% of the total mass of the solute, and the mass of the non-polar solvent is 150%-200% of the total mass of the solute; the ratio of the sum of the amount of the soft segment compound and the 2,2-dimethylolpropionic acid to the amount of the hard segment compound is 1:1.4; the mass of the catalyst accounts for 1%-2% of the total mass of the solute; the solute includes a soft segment compound, 2,2-dimethylolpropionic acid and a hard segment unit; Step 2) adding 250-300 mesh sodium chlorite particles to the polyurethane emulsion obtained in step 1), wherein the mass of the added sodium chlorite particles is 5%-20% of the mass of the polyurethane emulsion, stirring thoroughly, casting into a mold, and placing in an oven at 26-35° C. until constant weight is formed into a film, thereby obtaining the reactive controlled-release chlorine dioxide composite film.

2. The method for preparing a reactive controlled-release chlorine dioxide composite film according to claim 1, wherein: The non-polar solvent is one of cyclohexane, n-hexane, dichloromethane, acetone, toluene, chloroform, and methanol, or a mixture of two or more thereof.

3. The method for preparing a reactive controlled-release chlorine dioxide composite film according to claim 1, wherein: The soft segment compound includes one or more of the following: polytetramethylene ether glycol, polypropylene glycol, vinyl polymer grafted polyether polyol, and polyethylene glycol.

4. The method for preparing a reactive controlled-release chlorine dioxide composite film according to claim 1, wherein: The hard segment compound includes one or more of the following: isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

5. The method for preparing a reactive controlled-release chlorine dioxide composite film according to claim 1, wherein: The catalyst is one of the following: dibutyltin dilaurate, stannous octoate, and lead octoate.

6. A reactive controlled-release chlorine dioxide composite film, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 5.

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