Preparation method of water-soluble film

Abstract

The invention provides a preparation method of a water-soluble film, which comprises the following steps: S1, blending polyvinyl alcohol and isobutyric acid, adding into a solvent, and heating to react under the catalysis of concentrated sulfuric acid to generate an ester system; s2, adding polyethylene glycol and a surfactant into the ester system, and uniformly stirring to obtain a blend; s3, adding an auxiliary agent into the saturated sodium sulfate solution to obtain a coagulating bath solution, and spraying the blend into the coagulating bath solution in a high-pressure nitrogen spinning manner by adopting a wet spinning technology; and S4, after the filaments are separated out, drawing with external force, washing and drying to obtain the water-soluble film. Wherein the mass ratio of the polyvinyl alcohol to the isobutyric acid is 1: (0.01-0.05). The water-soluble film disclosed by the invention can be dissolved in water at a stable speed, so that the problems of large fluctuation and mutation of the dissolution speed are avoided, meanwhile, the coated content is endowed with a slow release function, the problems in the prior art are solved, and the water-soluble film has a good application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of packaging materials, and mainly to a method for preparing a water-soluble film. Background Art

[0002] Polyvinyl alcohol is non-toxic, highly hydrophilic, and has good mechanical strength and physical and chemical properties. It is an ideal fiber material. Polyethylene glycol has good compatibility with many organic components, good water solubility, excellent dispersibility and adhesion, and is widely used in the cosmetics, chemical fiber and other industries. Polyvinyl alcohol and polyethylene glycol both have good water solubility and are often used in the preparation of water-soluble films. This water-soluble film is a degradable green packaging material used for the packaging of various products. The water-soluble film dissolves in water, and the wrapped substances are released without polluting the environment.

[0003] At present, water-soluble films have been widely used, but there are still some problems. For example, the dissolution rate of water-soluble films in water is unstable, and sometimes it dissolves quickly, causing the following three problems. First, it is inconvenient to use. The dissolution rate is too fast, and the user needs to complete the operation in a short time, which may pose a challenge in some cases. Second, safety risks. In certain specific cases, such as the packaging of pesticides or chemical reagents, the dissolution rate of water-soluble films is too fast, which may increase the safety risks of users, especially in the absence of adequate preparation. The risk is greater; third, cost control. For some applications that need to control the dissolution rate of water-soluble films to optimize the use process, such as the packaging of pesticides, the dissolution rate is too fast, which may mean that the packaging materials need to be replaced more frequently, thereby increasing costs. In addition, some water-soluble films also have poor mechanical properties that cause the film to be damaged, resulting in the exposure of the film-wrapped substances. The exposed substances come into contact with the air and may affect their use effect.

[0004] In summary, it is necessary to develop a new technical solution to solve the defects and shortcomings in the existing technology. Summary of the invention

[0005] The present invention provides a method for preparing a water-soluble film. The water-soluble film has a stable dissolution rate and can be slowly dissolved in water, which is beneficial to the slow release of the encapsulated substance and has good application prospects.

[0006] An object of the present invention is to provide a method for preparing a water-soluble film, the method comprising the following steps:

[0007] S1, mixing polyvinyl alcohol and isobutyric acid, adding them into a solvent, heating and reacting them under the catalysis of concentrated sulfuric acid to generate an esterification system;

[0008] S2, adding polyethylene glycol, a surfactant, and a water-soluble starch to the esterification system, stirring evenly to obtain a blend;

[0009] S3, adding an auxiliary agent to a saturated sodium sulfate solution to obtain a coagulation bath solution, and using a wet spinning technique to spray the blend into the coagulation bath solution with high-pressure nitrogen;

[0010] S4. After the filaments are precipitated, they are pulled by external force, washed and dried to obtain the water-soluble film.

[0011] Furthermore, the mass ratio of the polyvinyl alcohol to isobutyric acid is 1:(0.01-0.05).

[0012] Furthermore, the mass ratio of the polyvinyl alcohol, polyethylene glycol, surfactant and water-soluble starch is 1:(1-3):(0.04-0.06):(0.05-0.08).

[0013] Furthermore, the temperature of the heating reaction is 60-75°C.

[0014] Furthermore, the amount of concentrated sulfuric acid used is 3-4wt% of the polyvinyl alcohol.

[0015] Furthermore, the mass ratio of the polyvinyl alcohol to the solvent is 1:(17-23).

[0016] Furthermore, the surfactant is selected from one or more of long-chain fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene alkylamine, and polyoxyethylene alkylolamide.

[0017] Furthermore, the auxiliary agent is selected from one or more of organic acids, inorganic acids and inorganic salts.

[0018] Furthermore, the auxiliary agent includes sulfuric acid, acetic acid and zinc sulfate.

[0019] Furthermore, the solvent is selected from DMF.

[0020] Furthermore, the injection flow rate of the high-pressure nitrogen spinneret is 2-10 ml / min.

[0021] Furthermore, the spinning speed of the wet spinning is 40-50 m / min.

[0022] Furthermore, the temperature of the coagulation bath solution is 10-50°C.

[0023] Furthermore, the residence time of the precursor precipitated from the blend in the coagulation bath solution is 15-35s.

[0024] Furthermore, the stretching multiple of the external force traction is 1-3 times.

[0025] The present invention has the following beneficial effects:

[0026] The preparation method of the water-soluble film provided by the present invention reduces the number of hydroxyl groups on the polyvinyl alcohol by grafting isobutyric acid onto polyvinyl alcohol, and introduces a hydrophobic isobutyl group to reduce the hydrophilicity of the polyvinyl alcohol, thereby reducing the dissolution rate of the polyvinyl alcohol in water and making it more stable. In addition, the polyvinyl alcohol has good mechanical properties and is not easily damaged, thereby preventing the wrapped material from being exposed. Polyethylene glycol has good water solubility, dispersibility and adhesion. After being blended with the polyvinyl alcohol grafted with isobutyric acid, the polyvinyl alcohol grafted with isobutyric acid is uniformly dispersed in the polyethylene glycol. The two have a synergistic effect, so that the water-soluble film can be dissolved in water at a stable speed, thereby avoiding the problem of large fluctuation and sudden change in the dissolution speed, and at the same time giving the wrapped content a function of sustained release, thereby overcoming the problems existing in the prior art. DETAILED DESCRIPTION

[0027] In order to more clearly illustrate the technical solution of the present invention, the following examples are listed. Unless otherwise stated, the raw materials, reactions and post-treatment methods shown in the examples are common raw materials on the market and technical methods well known to those skilled in the art.

[0028] The words "preferred", "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0029] It should be understood that, except in any operating examples, or where otherwise indicated, all numbers indicating, for example, the amounts of ingredients used in the specification and claims should be understood to be modified in all cases by the term "about". Therefore, unless indicated to the contrary, the numerical parameters set forth in the following specification and the appended claims are approximate values ​​that vary depending on the desired properties to be obtained by the present invention.

[0030] The following raw materials are used in the embodiments of the present invention:

[0031] Polyvinyl alcohol, molecular weight 72600-77000;

[0032] Polyethylene glycol, average molecular weight is about 4000.

[0033] Example 1

[0034] A method for preparing a water-soluble film comprises the following steps:

[0035] S1, adding 10 g of polyvinyl alcohol and 0.3 g of isobutyric acid to 200 g of DMF, adding 0.4 g of concentrated sulfuric acid (concentration of 98 wt%) and heating to 70° C. to react and obtain an esterification system;

[0036] S2, adding 20 g of polyethylene glycol, 0.5 g of Tween-80, and 0.6 g of water-soluble starch to the esterification system, stirring evenly to obtain a blend;

[0037] S3, adding 0.4 g / L concentrated sulfuric acid, 0.6 g / L glacial acetic acid, and 1.5 g / L zinc sulfate to a saturated sodium sulfate solution at room temperature and stirring to obtain a coagulation bath solution, and using wet spinning technology and high-pressure nitrogen spinning to spray the blend into the coagulation bath solution at a spray flow rate of 6 ml / min;

[0038] S4. After filaments are precipitated from the coagulation bath solution, the filaments are allowed to stay for 25 seconds and pulled by external force with a stretching multiple of 2. The filaments are spun at a speed of 45 m / min, washed with anhydrous ethanol and deionized water 2-3 times in sequence, and naturally air-dried at room temperature and pressure to obtain a water-soluble film.

[0039] Example 2

[0040] A method for preparing a water-soluble film comprises the following steps:

[0041] S1, adding 10 g of polyvinyl alcohol and 0.5 g of isobutyric acid to 200 g of DMF, adding 0.4 g of concentrated sulfuric acid (concentration of 98 wt%) and heating to 70° C. to react and obtain an esterification system;

[0042] S2, adding 20 g of polyethylene glycol, 0.5 g of Tween-80, and 0.6 g of water-soluble starch to the esterification system, stirring evenly to obtain a blend;

[0043] S3, adding 0.4 g / L concentrated sulfuric acid, 0.6 g / L glacial acetic acid, and 1.5 g / L zinc sulfate to a saturated sodium sulfate solution at room temperature and stirring to obtain a coagulation bath solution, and using wet spinning technology and high-pressure nitrogen spinning to spray the blend into the coagulation bath solution at a spray flow rate of 6 ml / min;

[0044] S4. After filaments are precipitated from the coagulation bath solution, the filaments are allowed to stay for 25 seconds and pulled by external force with a stretching multiple of 2. The filaments are spun at a speed of 45 m / min, washed with anhydrous ethanol and deionized water 2-3 times in sequence, and naturally air-dried at room temperature and pressure to obtain a water-soluble film.

[0045] Example 3

[0046] S1, adding 10 g of polyvinyl alcohol and 0.3 g of isobutyric acid to 200 g of DMF, adding 0.4 g of concentrated sulfuric acid (concentration of 98 wt%) and heating to 70° C. to react and obtain an esterification system;

[0047] S2, adding 30 g of polyethylene glycol, 0.5 g of Tween-80, and 0.6 g of water-soluble starch to the esterification system, stirring evenly to obtain a blend;

[0048] S3, adding 0.4 g / L concentrated sulfuric acid, 0.6 g / L glacial acetic acid, and 1.5 g / L zinc sulfate to a saturated sodium sulfate solution at room temperature and stirring to obtain a coagulation bath solution, and using wet spinning technology and high-pressure nitrogen spinning to spray the blend into the coagulation bath solution at a spray flow rate of 6 ml / min;

[0049] S4. After filaments are precipitated from the coagulation bath solution, the filaments are allowed to stay for 25 seconds and pulled by external force with a stretching multiple of 2. The filaments are spun at a speed of 45 m / min, washed with anhydrous ethanol and deionized water 2-3 times in sequence, and naturally air-dried at room temperature and pressure to obtain a water-soluble film.

[0050] Comparative Example

[0051] The difference between this comparative example and Example 1 is that isobutyric acid and concentrated sulfuric acid are not added in step S1.

[0052] Test Example 1

[0053] The dissolution rate and dissolution stability of the water-soluble films of Examples 1-3 and the comparative example were tested.

[0054] Test method:

[0055] Add 500mL of tap water to a beaker and control the water temperature to 25°C. Place 5g of sample on the water surface. The water surface remains still and the sample does not clump and stick to the inner wall of the beaker. Start timing when the sample is placed on the water surface. When the sample disappears completely, it is the dissolution time of the sample in seconds (s). Repeat the experiment 5 times and take (mean ± standard deviation) as the final result. The average value of the sample dissolution time is used to evaluate its dissolution rate, and the standard deviation of the sample dissolution time is used to evaluate its dissolution stability.

[0056] The test results are shown in Table 1.

[0057] Table 1 Dissolution rate and dissolution stability test results of water-soluble films

[0058] sample Dissolution time(s) Example 1 200±5 Example 2 208±4 Example 3 196±7 Comparative Example 93±13

[0059] It can be seen from Table 1 that the average value of the dissolution time of the water-soluble films of Examples 1-3 is between 196-208s, while that of the comparative example is 73s, indicating that the water-soluble films of Examples 1-3 dissolve more slowly and can achieve the effect of sustained release of the encapsulated contents; the standard deviation of the dissolution time of the water-soluble films of Examples 1-3 is between ±4-±7s, while that of the comparative example is ±13s, indicating that the dissolution stability of the water-soluble films of Examples 1-3 is better than that of the comparative example.

[0060] Test Example 2

[0061] The mechanical properties of the water-soluble films of Examples 1-3 and the comparative example were tested.

[0062] Test method:

[0063] The mechanical properties test was performed in accordance with GB / T 1040-92, wherein the ambient temperature was (25+2)°C, the ambient humidity was 50%, and the tensile speed was 50 mm / min.

[0064] The test results are shown in Table 2.

[0065] Table 2 Mechanical properties test results of water-soluble films

[0066] sample Tensile strength(Mpa) Elongation at break (%) Example 1 30.2 233 Example 2 31.4 239 Example 3 32.7 241 Comparative Example 29.6 228

[0067] It can be seen from Table 2 that the tensile strength of the water-soluble films of Examples 1-3 is between 30.2-32.7 MPa, while that of the comparative example is 29.6 MPa, indicating that the tensile strength of the water-soluble films of Examples 1-3 is slightly better than that of the comparative example; the elongation at break of the water-soluble films of Examples 1-3 is between 233-241%, while that of the comparative example is 228%, indicating that the elongation at break of the water-soluble films of Examples 1-3 is slightly better than that of the comparative example.

[0068] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0069] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a water-soluble film, characterized in that: The steps include: S1, mixing polyvinyl alcohol and isobutyric acid, adding them into a solvent, heating and reacting them under the catalysis of concentrated sulfuric acid to generate an esterification system; S2, adding polyethylene glycol, a surfactant, and a water-soluble starch to the esterification system, stirring evenly to obtain a blend; S3, adding an auxiliary agent to a saturated sodium sulfate solution to obtain a coagulation bath solution, and using a wet spinning technique to spray the blend into the coagulation bath solution with high-pressure nitrogen; S4, after the filaments are precipitated, they are pulled by external force, washed and dried to obtain the water-soluble film; Wherein, the mass ratio of the polyvinyl alcohol to isobutyric acid is 1:(0.01-0.05).

2. The method for preparing a water-soluble film according to claim 1, characterized in that: The mass ratio of the polyvinyl alcohol, polyethylene glycol, surfactant and water-soluble starch is 1:(1-3):(0.04-0.06):(0.05-0.08).

3. The method for preparing the water-soluble film according to claim 1, characterized in that: The temperature of the heating reaction is 60-75°C.

4. The method for preparing a water-soluble film according to claim 1, characterized in that: The surfactant is selected from one or more of long-chain fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene alkylamine, and polyoxyethylene alkylolamide.

5. The method for preparing a water-soluble film according to claim 1, characterized in that: The auxiliary agent is selected from one or more of organic acids, inorganic acids and inorganic salts.

6. The method for preparing a water-soluble film according to claim 5, characterized in that: The auxiliary agents include sulfuric acid, acetic acid and zinc sulfate.

7. The method for preparing a water-soluble film according to claim 1, characterized in that: The solvent is selected from DMF.

8. The method for preparing a water-soluble film according to claim 1, characterized in that: The injection flow rate of the high-pressure nitrogen spinneret is 2-10 ml / min.

9. The method for preparing a water-soluble film according to claim 1, characterized in that: The spinning speed of the wet spinning is 40-50 m / min.

10. The method for preparing a water-soluble film according to claim 1, characterized in that: The temperature of the coagulation bath solution is 10-50°C.