CN117487223A - A kind of preparation method of shellac resin and PVA composite film - Google Patents

Abstract

The invention relates to a preparation method of a shellac resin and PVA composite film, which comprises the following steps of (1) preparing shellac resin emulsion; (2) preparing an aqueous PVA solution; (3) blending to form a film; according to the invention, the ultraviolet resin and the PVA are adopted to prepare the composite film through the aqueous phase physical blending method, the compactness of the ultraviolet resin film is improved by adding the PVA, and the compactness, the tensile strength and the elongation at break of the composite film are also improved along with the increase of the PVA content, so that the degree of chemical reaction of the ultraviolet resin and the PVA is low, and the ultraviolet resin and the PVA have certain physical compatibility. And along with the increase of PVA content, the contact angle of the composite film is continuously reduced, the hygroscopicity of the composite film is continuously enhanced, and further, the composite film has better hydrophilicity, the composite film and the composite film have larger degree of physical blending, and the shellac resin is more stable in the solution.

Description

A kind of preparation method of shellac resin and PVA composite film

Technical field

The invention belongs to the technical field of wind power equipment operation and maintenance, and specifically relates to a preparation method of a shellac resin and PVA composite film.

Background technique

Shellac is a natural, non-toxic, degradable and special-property natural resin mixture secreted by lac insects after sucking plant sap. It has a long history of application in the pharmaceutical field. However, the mechanical properties of shellac resin itself are poor, and aging reactions such as polymerization are prone to occur during long-term storage. Therefore, in most cases, another substance will be used to modify it before use. While improving its physical and mechanical properties, it also focuses on improving its hydrophilic properties and further expanding the use of shellac as a medicinal natural polymer material. scope of application.

PVA has good hydrophilic properties and film-forming flexibility, and pharmaceutical-grade PVA is an extremely safe polymer organic substance that is non-toxic to the body, has no side effects, and has good biocompatibility. It can be seen from this that PVA and shellac resin are complementary in nature. It can be used as an alternative material to improve the shellac resin. PVA is mixed into the shellac resin to prepare a composite membrane, and the hydrophilicity of the composite membrane is studied to expand the applicability of the two.

Contents of the invention

In view of the above problems, the present invention provides a preparation method of a shellac resin and PVA composite film.

The specific technical solution is: a preparation method of a shellac resin and PVA composite film, including the following steps:

(1) Preparation of shellac resin emulsion: Dissolve shellac resin in absolute ethanol, filter, and remove alcohol-insoluble matter. The filtrate is added to high-speed sheared deionized water at a speed of 5 mL/min to prepare shellac resin emulsion. spare;

(2) Prepare PVA aqueous solution: Dissolve PVA in deionized water at 90°C, and then cool to room temperature to prepare a PVA aqueous solution for later use;

(3) Blending film formation: Mix the shellac resin emulsion and PVA aqueous solution prepared above in a water bath at 50°C and stir for 2 hours, and then transfer to a rotary evaporator to rotary evaporate for 1 hour to recover part of the solvent ethanol. After rotary evaporation Transfer the mixture to room temperature and continue stirring for 24 hours, and remove bubbles on the surface of the mixture. Finally, pour the liquid into a petri dish and dry it in an electric constant-temperature incubator at 30°C for 24 hours until the solvents of the mixture, ethanol and water, are fully evaporated. The mixed liquid is dried into a shellac resin and PVA composite film and then lifted up to obtain a shellac resin and PVA composite film.

Further, the mass ratio of shellac resin and absolute ethanol in step (1) is 5:194.1.

Furthermore, the shear rate of high-speed shearing in step (1) is >1000r/min.

Further, the volume ratio of the shellac resin filtrate and deionized water in step (1) is 2:1.

Further, the mass ratio of PVA and deionized water in step (2) is 1:30.

Further, in step (3), the mass fraction of PVA in the composite film is controlled to 50%.

Beneficial effects of the present invention: The present invention uses shellac resin and PVA to prepare a composite film through an aqueous physical blending method. The addition of PVA improves the density of the shellac resin film, and as the PVA content increases, the density of the composite film increases. The properties, tensile strength, and elongation at break also increase. The degree of chemical reaction between the two is relatively low. Shellac resin and PVA have certain physical compatibility. Moreover, as the PVA content increases, the contact angle of the composite film continues to decrease, and the hygroscopicity of the composite film continues to increase, which further confirms that the composite film has better hydrophilicity, and the combination of the two has a greater degree of physical blending , Shellac resin is relatively stable in its solution.

Description of drawings

Figure 1 is a diagram of the appearance of the composite film under different PVA mass fractions of the present invention; wherein: (a) the PVA proportion is 0%; (b) the PVA proportion is 10%; (c) the PVA proportion is 20%; (d) PVA The proportion is 30%; (e) the PVA proportion is 40%; (f) the PVA proportion is 50%; (g) the PVA proportion is 100%; black is the background color in the picture;

Figure 2 is a morphological diagram of the water droplet contact angle of the composite film under different PVA mass fractions of the present invention; (a) PVA proportion is 10%; (b) PVA proportion is 20%; (c) PVA proportion is 30%; (d) ) PVA proportion is 40%; (e) PVA proportion is 50%;

Figure 3 is the moisture absorption isotherm of the composite film under different PVA mass fractions of the present invention;

Figure 4 is a blended solution diagram of the shellac resin emulsion and PVA aqueous solution of the present invention.

Detailed ways

In order to make the technical problems and technical solutions solved by the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

Example 1: The mass fraction of PVA in the composite film is 10%.

(1) Preparation of shellac resin emulsion: Add 18g of shellac resin to 900mL of absolute ethanol. After stirring and dissolving, filter to remove alcohol-insoluble matter. The filtrate is added to high-speed shear at a speed of 5ml/min through a peristaltic pump (the shear rate is 1000r/min) in deionized water, the volume ratio of the shellac resin filtrate to the deionized water is 2:1, prepare a shellac resin emulsion for later use;

(2) Prepare PVA aqueous solution: Dissolve 2g PVA in 60 mL deionized water at 90°C, and then cool to room temperature to prepare a PVA aqueous solution for later use;

(3) Blending film formation: Place the shellac resin emulsion and PVA aqueous solution prepared above in a water bath at 50°C and mix according to the volume ratio (about 30:2) when the mass ratio of shellac resin to PVA is 9:1. After stirring for 2 hours, transfer to a rotary evaporator for 1 hour to recover part of the solvent ethanol, and then transfer to room temperature to continue stirring for 24 hours and remove bubbles on the surface of the mixture. Finally, pour the liquid into a petri dish and heat it with electric heating at 30°C. Dry in a constant-temperature incubator for 24 hours. After the solvents ethanol and water of the mixed solution are fully evaporated, the mixed solution is dried into a shellac resin and PVA composite film and then peeled off to prepare a shellac resin and PVA composite film.

Example 2: The mass fraction of PVA in the composite film is 20%.

(1) Preparation of shellac resin emulsion: Add 12g of shellac resin to 600mL of absolute ethanol, stir and dissolve, filter to remove alcohol-insoluble matter, and add the filtrate to high-speed shear at a speed of 5ml/min through a peristaltic pump (the shear rate is 1000r/min) in deionized water, the volume ratio of the shellac resin filtrate to the deionized water is 2:1, and prepare a shellac resin emulsion for later use;

(2) Prepare PVA aqueous solution: Dissolve 3g PVA in 90 mL deionized water at 90°C, and then cool to room temperature to prepare a PVA aqueous solution for later use;

(3) Blending film formation: Place the shellac resin emulsion and PVA aqueous solution prepared above in a water bath at 50°C and mix according to the volume ratio (approximately 20:3) when the mass ratio of shellac resin to PVA is 8:2. After stirring for 2 hours, transfer to a rotary evaporator for 1 hour to recover part of the solvent ethanol. Then transfer to room temperature to continue stirring for 24 hours and remove air bubbles on the surface of the mixture. Finally, pour the liquid into a petri dish and heat it with electric heating at 30°C. Dry in a constant-temperature incubator for 24 hours. After the solvents ethanol and water of the mixed solution are fully evaporated, the mixed solution is dried into a shellac resin and PVA composite film and then peeled off to prepare a shellac resin and PVA composite film.

Example 3: The mass fraction of PVA in the composite film is 30%.

(1) Preparation of shellac resin emulsion: Add 9.3g of shellac resin to 465mL of absolute ethanol. After stirring and dissolving, filter to remove alcohol-insoluble matter. The filtrate is added to high-speed shear (shear rate) through a peristaltic pump at a speed of 5ml/min. (1000r/min) in deionized water, the volume ratio of the shellac resin filtrate to the deionized water is 2:1, prepare a shellac resin emulsion for later use;

(2) Prepare PVA aqueous solution: Dissolve 4g PVA in 120mL deionized water at 90°C, and then cool to room temperature to prepare a PVA aqueous solution for later use;

(3) Blending film formation: Place the shellac resin emulsion and PVA aqueous solution prepared above in a water bath at 50°C and mix according to the volume ratio (approximately 31:8) when the mass ratio of shellac resin to PVA is 7:3. After stirring for 2 hours, transfer to a rotary evaporator for 1 hour to recover part of the solvent ethanol. Then transfer to room temperature to continue stirring for 24 hours and remove air bubbles on the surface of the mixture. Finally, pour the liquid into a petri dish and heat it with electric heating at 30°C. Dry in a constant-temperature incubator for 24 hours. After the solvents ethanol and water of the mixed solution are fully evaporated, the mixed solution is dried into a shellac resin and PVA composite film and then peeled off to prepare a shellac resin and PVA composite film.

Example 4: The mass fraction of PVA in the composite film is 40%.

(1) Preparation of shellac resin emulsion: Add 7.5g of shellac resin to 375mL of absolute ethanol. After stirring and dissolving, filter to remove alcohol-insoluble matter. The filtrate is added to high-speed shear (shear rate) through a peristaltic pump at a speed of 5ml/min. (1000r/min) in deionized water, the volume ratio of the shellac resin filtrate to the deionized water is 2:1, prepare a shellac resin emulsion for later use;

(2) Prepare PVA aqueous solution: Dissolve 5g PVA in 150 mL deionized water at 90°C, and then cool to room temperature to prepare a PVA aqueous solution for later use;

(3) Blending film formation: Place the shellac resin emulsion and PVA aqueous solution prepared above in a water bath at 50°C and mix according to the volume ratio (approximately 5:2) when the mass ratio of shellac resin to PVA is 3:2. Stir for 2 hours, then transfer to room temperature and continue stirring for 24 hours, then transfer to a rotary evaporator to rotate and evaporate for 1 hour to recover part of the solvent ethanol and remove bubbles on the surface of the mixed solution. Finally, pour the liquid into a petri dish and heat it with electric heating at 30°C. Dry in a constant-temperature incubator for 24 hours. After the solvents ethanol and water of the mixed solution are fully evaporated, the mixed solution is dried into a shellac resin and PVA composite film and then peeled off to prepare a shellac resin and PVA composite film.

Example 5: The mass fraction of PVA in the composite film is 50%.

(1) Preparation of shellac resin emulsion: Add 6g of shellac resin to 300mL of absolute ethanol. After stirring and dissolving, filter to remove alcohol-insoluble matter. The filtrate is added to high-speed shear at a speed of 5ml/min through a peristaltic pump (the shear rate is 1000r/min) in deionized water, the volume ratio of the shellac resin filtrate to the deionized water is 2:1, and prepare a shellac resin emulsion for later use;

(2) Prepare PVA aqueous solution: Dissolve 6g PVA in 180 mL deionized water at 90°C, and then cool to room temperature to prepare a PVA aqueous solution for later use;

(3) Blending film formation: Place the shellac resin emulsion and PVA aqueous solution prepared above in a water bath at 50°C and mix according to the volume ratio (about 5:3) when the mass ratio of shellac resin to PVA is 1:1. After stirring for 2 hours, transfer to a rotary evaporator for 1 hour to recover part of the solvent ethanol. Then transfer to room temperature to continue stirring for 24 hours and remove air bubbles on the surface of the mixture. Finally, pour the liquid into a petri dish and heat it with electric heating at 30°C. Dry in a constant-temperature incubator for 24 hours. After the solvents ethanol and water of the mixed solution are fully evaporated, the mixed solution is dried into a shellac resin and PVA composite film and then peeled off to prepare a shellac resin and PVA composite film.

Test Example 1: Appearance of composite membranes under different PVA mass fractions

During the preparation process of the composite membrane, in order to reduce the thickness difference between the shellac resin and the PVA composite membrane, when the blends of the shellac resin emulsion and the PVA aqueous solution have the same concentration, the liquid level height put into the petri dish is controlled at 10± 1mm. After the mixture is finally dried and formed into a film according to the above preparation steps, the appearance of the film under different PVA mass fractions is shown in Figure 1. In Figure 1 (a), (b), (c), (d), (e) The PVA mass fractions of (f) and (g) are 0%, 10%, 20%, 30%, 40%, 50%, and 100% respectively. Black is the background color in the figure. It can be seen from Figure 1 that as the PVA content increases, the color of the composite film gradually becomes lighter, which is due to the colorless transparency of PVA after film formation; at the same time, as the PVA content increases, the color of the shellac resin The uniformity after film formation is improved, but a small amount of shellac resin will precipitate and cause local aggregation, which appears as spots, indicating that when water is used as the medium to blend the shellac resin film and PVA to form a film, the two will not be completely Mix evenly, which is also due to the difference in hydrophilicity between the two.

In addition, after stretching the finished composite film, it was found that the toughness of the composite film also increased with the increase in PVA content, and accordingly its tensile strength and elongation at break also increased.

Test Example 2: Measurement of water droplet contact angle of composite films under different PVA mass fractions

The composite membranes with different PVA mass fractions were placed on the glass slide of the contact angle meter, and the sessile contact angle between each membrane and deionized water was measured. The test results are shown in Figure 2, (a), (b), ( The PVA mass fractions of c), (d), and (e) are 10%, 20%, 30%, 40%, and 50% respectively. It can be seen from Figure 2 that as the PVA content increases, the contact angle continues to decrease. When the PVA content is 50%, the contact angle is the smallest at 16.87°. At this time, the composite membrane has the best hydrophilicity and the best wettability. good. It shows that the addition of PVA increases the hydrophilicity of the shellac resin membrane, and as the amount of PVA added increases, the hydrophilicity of the composite membrane increases in proportion.

Test Example 3: Determination of moisture absorption isotherms of composite films under different PVA mass fractions

The composite film samples prepared with different PVA mass fractions are placed in an environment with constant temperature and controlled humidity for a certain period of time, allowing the samples to absorb enough water vapor until equilibrium is reached, and then the samples are placed in a drying box and set in the box. The temperature is 70°C and dried for about 3 hours until the dry weight of the measured sample is constant, and the dry weight w ₀ of the sample is obtained.

The above dried samples were placed into desiccators respectively. Each desiccator was filled with different types of saturated solutions. Each saturated solution can provide a specific relative humidity; each sample was placed in the desiccator for 10 days until the obtained Until the mass is constant, it is recorded as wet weight w ₁ .

The types of saturated solutions in the dryer are: ① Magnesium chloride saturated solution, its relative humidity is 32.8%, that is, a _w = 0.328; ② Sodium dichromate saturated solution, its relative humidity is 54.4%, that is, a _w = 0.544; ③ The relative humidity of a saturated solution of sodium chloride is 75.3%, that is, a _w = 0.753; ④ The relative humidity of a saturated solution of potassium chloride is 84.3%, that is, a _w = 0.843; ⑤ The relative humidity of a saturated solution of potassium nitrate is 93.7 %, that is, a _w = 0.937; ⑥ Distilled water, its relative humidity is 100.0%, that is, a _w = 1.00.

Each composite film sample was measured three times under each relative humidity condition and the average value was taken. Record the constant weight of the composite film under each relative humidity condition, and use formula (1) to calculate the moisture content ω.

The moisture absorption isotherm of the film is drawn according to the ω value under different humidity conditions, and the moisture absorption isotherm of the composite film under different PVA mass fractions is obtained, as shown in Figure 3. As can be seen from Figure 3, the pure shellac resin film without PVA has the worst hygroscopicity, and its hygroscopicity shows a downward trend as the humidity increases; while the composite film with a PVA content of 10%-50% decreases as the humidity increases. The absorption rate shows an upward trend with the increase of humidity, and shows the strongest water absorption when the humidity is 100%, and the composite film with a PVA content of 50% has the best water absorption. This characteristic makes the composite film useful in the field of artificial skin materials. Possibilities are provided.

In summary, shellac resin and PVA can be blended to form a film through aqueous physical blending. The addition of PVA improves the density of the shellac resin film, and as the PVA content increases, the density and density of the composite film decrease. The tensile strength and elongation at break also increase, and the degree of chemical reaction between the two is relatively low. Shellac resin and PVA have certain physical compatibility.

Moreover, as the PVA content increases, the contact angle of the composite film continues to decrease, and the hygroscopicity of the composite film continues to increase, which further confirms that the composite film has better hydrophilicity, and the combination of the two has a greater degree of physical commonality. Mixed, shellac resin is relatively stable in its solution.

The present invention has been described in detail through specific and preferred embodiments. However, those skilled in the art should understand that the present invention is not limited to the above-described embodiments. Anything within the spirit and principles of the present invention can be made. Any modifications, equivalent substitutions, etc. shall be included in the protection scope of the present invention.

Claims (6)

1. A method for preparing a shellac resin and PVA composite film, which is characterized in that it includes the following steps: (1) Preparation of shellac resin emulsion: Dissolve shellac resin in absolute ethanol, filter, and remove alcohol-insoluble matter. The filtrate is added to high-speed sheared deionized water at a speed of 5 mL/min to prepare shellac resin emulsion. spare; (2) Prepare PVA aqueous solution: Dissolve PVA in deionized water at 90°C, and then cool to room temperature to prepare a PVA aqueous solution for later use; (3) Blending film formation: Mix the shellac resin emulsion and PVA aqueous solution prepared above in a water bath at 50°C and stir for 2 hours, and then transfer to a rotary evaporator to rotary evaporate for 1 hour to recover part of the solvent ethanol. After rotary evaporation Transfer the mixture to room temperature and continue stirring for 24 hours, and remove bubbles on the surface of the mixture. Finally, pour the liquid into a petri dish and dry it in an electric constant-temperature incubator at 30°C for 24 hours until the solvents of the mixture, ethanol and water, are fully evaporated. The mixed liquid is dried into a shellac resin and PVA composite film and then lifted up to obtain a shellac resin and PVA composite film. 2. A method for preparing a shellac resin and PVA composite film according to claim 1, characterized in that the mass ratio of shellac resin and absolute ethanol in step (1) is 5:194.1. 3. A method for preparing a shellac resin and PVA composite film according to claim 1, characterized in that the shear rate of high-speed shearing in step (1) is >1000 r/min. 4. A method for preparing a shellac resin and PVA composite membrane according to claim 1, wherein the volume ratio of the shellac resin filtrate and deionized water in step (1) is 2:1. 5. A method for preparing a shellac resin and PVA composite membrane according to claim 1, characterized in that the mass ratio of PVA to deionized water in step (2) is 1:30. 6. A method for preparing a shellac resin and PVA composite film according to claim 1, characterized in that in step (3), the mass fraction of PVA in the composite film is controlled to 50%.