Preparation method of a water-soluble film

Abstract

The present invention provides a method for preparing a water-soluble film, which comprises the following steps: S1. Blend polyvinyl alcohol with isobutyric acid, add them into a solvent, and under the catalysis of concentrated sulfuric acid, heat and react to generate an esterified product system; S2. Add polyethylene glycol and a surfactant to the esterified product system, and stir evenly to obtain a blend; S3. Add an auxiliary agent to a saturated sodium sulfate solution to obtain a coagulation bath solution, and adopt a wet spinning technique to spray the blend into the coagulation bath solution by means of high-pressure nitrogen spinning; S4. After filaments are precipitated, use an external force to draw, wash and dry 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 of the present invention can dissolve in water at a stable speed, avoiding the problems of large fluctuations and mutations in the dissolution speed, and at the same time endowing the encapsulated content with a sustained-release function, overcoming the problems existing in the prior art and having good application prospects.

Description

Technical Field

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

[0002] Polyvinyl alcohol has the characteristics of non-toxicity, strong hydrophilicity, good mechanical strength and physicochemical properties, and is an ideal fiber material. Polyethylene glycol has good compatibility with many organic components, has good water solubility, excellent dispersibility and adhesiveness, etc., and has extremely wide applications in industries such as cosmetics and chemical fibers. Both polyvinyl alcohol and polyethylene glycol have good water solubility and are often used in the preparation of water-soluble films. This kind of 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 causing pollution to 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. Sometimes they dissolve 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, there are safety risks. In certain specific situations, such as the packaging of pesticides or chemical reagents, if the water-soluble film dissolves too quickly, it may increase the safety risks of the user, especially when not fully prepared, the risk is greater. Third, cost control. For some applications that require controlling the dissolution rate of the water-soluble film to optimize the use process, such as the sub-packaging of pesticides, too fast dissolution rate may mean more frequent replacement of packaging materials, thus increasing costs. In addition, some water-soluble films also have the problem that their mechanical properties are not good, causing the film to be damaged, resulting in the exposure of the substances wrapped by the film. The exposed substances may contact the air and affect their use effects.

[0004] In summary, it is necessary to develop a new technical solution to solve the defects and deficiencies existing in the prior art. Summary of the Invention

[0005] The present invention provides a preparation method of a water-soluble film. The dissolution rate of the water-soluble film is stable and it can dissolve slowly in water, which is beneficial to the slow release of the wrapped substances and has good application prospects.

[0006] An object of the present invention is to provide a preparation method of a water-soluble film. The preparation method of the water-soluble film includes the following steps:

[0007] S1. Blend polyvinyl alcohol and isobutyric acid, add them into a solvent, and under the catalysis of concentrated sulfuric acid, heat and react to generate an esterified product system;

[0008] S2. Add polyethylene glycol, surfactant, and water-soluble starch to the esterified product system, and stir evenly to obtain a blend.

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

[0010] S4. After the filaments precipitate, use external force to draw, wash, and dry to obtain the water-soluble film.

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

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

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

[0014] Further, the dosage of concentrated sulfuric acid is 3 - 4 wt% of polyvinyl alcohol.

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

[0016] Further, 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 alkyl alcohol amide.

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

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

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

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

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

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

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

[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 grafts isobutyric acid onto polyvinyl alcohol, reducing the number of hydroxyl groups on polyvinyl alcohol and introducing hydrophobic isobutyl groups at the same time, reducing the hydrophilicity of polyvinyl alcohol, thereby reducing the dissolution rate of polyvinyl alcohol in water and making it more stable. Moreover, polyvinyl alcohol has good mechanical properties and is not easily damaged, avoiding the exposure of the wrapped substances; polyethylene glycol has good water solubility, dispersibility and adhesiveness. After being blended with isobutyric acid-grafted polyvinyl alcohol, the isobutyric acid-grafted polyvinyl alcohol is uniformly dispersed in polyethylene glycol, and the two play a synergistic effect, enabling the water-soluble film to dissolve in water at a stable rate, avoiding the problems of large fluctuations and sudden changes in the dissolution rate, and at the same time endowing the wrapped contents with a sustained-release function, overcoming the problems existing in the prior art. Specific embodiments

[0027] In order to more clearly illustrate the technical solutions of the present invention, the following examples are listed. The raw materials, reactions and post-treatment means appearing in the examples are all common raw materials on the market and technical means well-known to those skilled in the art, unless otherwise specified.

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

[0029] It should be understood that, unless otherwise indicated in any operating example or otherwise, all numbers representing the amounts of ingredients or otherwise used in the specification and claims should be understood to be modified in all cases by the term "about". Therefore, unless otherwise indicated, the numerical parameters set forth in the following specification and appended claims are approximations that vary depending upon the desired properties sought to be obtained by the present invention.

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

[0031] Polyvinyl alcohol, with a molecular weight of 72,600-77,000;

[0032] Polyethylene glycol, with an average molecular weight of about 4000.

[0033] Example 1

[0034] A preparation method of a water-soluble film includes the following steps:

[0035] S1. Mix 10 g of polyvinyl alcohol and 0.3 g of isobutyric acid in 200 g of DMF, add 0.4 g of concentrated sulfuric acid (concentration 98 wt%) and heat to 70 °C to obtain an esterified product system;

[0036] S2. Add 20 g of polyethylene glycol, 0.5 g of Tween-80, and 0.6 g of water-soluble starch to the esterified product system, stir evenly to obtain a blend;

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

[0038] S4. After filaments precipitate in the coagulation bath solution, let the filaments stay for 25 s, apply external force for traction, the stretching ratio of traction is 2 times, spin the filaments at a speed of 45 m / min, wash with absolute ethanol and deionized water 2 - 3 times in sequence, and air dry naturally under normal 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. Mix 10 g of polyvinyl alcohol and 0.5 g of isobutyric acid in 200 g of DMF, add 0.4 g of concentrated sulfuric acid (concentration 98 wt%) and heat to 70 °C to obtain an esterified product system;

[0042] S2. Add 20 g of polyethylene glycol, 0.5 g of Tween-80, and 0.6 g of water-soluble starch to the esterified product system, stir evenly to obtain a blend;

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

[0044] S4. After filaments precipitate in the coagulation bath solution, let the filaments stay for 25 s, apply external force for traction, the stretching ratio of traction is 2 times, spin the filaments at a speed of 45 m / min, wash with absolute ethanol and deionized water 2 - 3 times in sequence, and air dry naturally under normal temperature and pressure to obtain a water-soluble film.

[0045] Example 3

[0046] S1. Mix 10 g of polyvinyl alcohol and 0.3 g of isobutyric acid in 200 g of DMF, add 0.4 g of concentrated sulfuric acid (concentration: 98 wt%) and heat to 70 °C to obtain an esterified product system;

[0047] S2. Add 30 g of polyethylene glycol, 0.5 g of Tween-80, and 0.6 g of water-soluble starch to the esterified product system and stir evenly to obtain a blend;

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

[0049] S4. After filaments precipitate in the coagulation bath solution, let the filaments stay for 25 s, apply an external force for traction, with a draw ratio of 2 times, spin the filaments at a speed of 45 m / min, wash them 2 - 3 times successively with absolute ethanol and deionized water, and air-dry them naturally under normal 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] Test the dissolution rate and dissolution stability of the water-soluble films of Examples 1 - 3 and the comparative example.

[0054] Test method:

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

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

[0057] Table 1 Test results of the dissolution rate and dissolution stability of the water-soluble film

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

[0059] As can be seen from Table 1, the average dissolution time of the water-soluble films in Examples 1-3 is between 196 - 208 s, while that of the comparative example is 73 s, indicating that the water-soluble films in Examples 1-3 have a slower dissolution rate and can achieve the effect of slow release of the encapsulated contents; the standard deviation of the dissolution time of the water-soluble films in Examples 1-3 is between ±4 - ±7 s, while that of the comparative example is ±13 s, indicating that the dissolution stability of the water-soluble films in 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 property test was carried out in accordance with GB / T 1040-92. Among them, 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 Test Results of Mechanical Properties 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] As can be seen from Table 2, the tensile strength of the water-soluble films in 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 in Examples 1-3 is slightly better than that of the comparative example; the elongation at break of the water-soluble films in 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 in Examples 1-3 is slightly better than that of the comparative example.

[0068] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0069] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments 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); The surfactant is Tween-80; The auxiliary agents are concentrated sulfuric acid, glacial acetic acid and zinc sulfate.

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 a 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 solvent is selected from DMF.

5. 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.

6. 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.

7. 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.