Preparation method and application of sodium alginate film

Abstract

The invention provides a preparation method and application of a sodium alginate film, and the method comprises the following steps: dissolving sodium alginate in deionized water, adding catalysts EDC and DMAP, dropwise adding a glutaric anhydride solution at 40-50 DEG C, reacting for 1 hour, and carrying out alcohol precipitation, washing and drying to obtain glutaric anhydride esterified sodium alginate; and preparing the glutaric anhydride esterified sodium alginate into a 2% w / v solution, adding 0.4% w / v glycerol as a plasticizer, stirring at 50 DEG C for 30 minutes, carrying out ultrasonic degassing, casting to form a film, drying at 35 DEG C, and balancing to obtain the sodium alginate film. According to the method, the sodium alginate film is directly endowed with an anti-ultraviolet function through esterification modification of glutaric anhydride, and meanwhile, the hydrophobicity and the water vapor barrier property of the film are improved, so that the film can be used for manufacturing a UVB protective film and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural polymer materials, in particular to a preparation method of a sodium alginate film and application thereof. BACKGROUND

[0002] Sodium alginate is a natural anionic polysaccharide mainly extracted from brown algae, which can also be called sodium alginate or kelp gum. It is an unbranched linear polymer composed of two structural units of beta-D-mannuronic acid (M) and alpha-L-guluronic acid (G). Sodium alginate is a green and environmentally friendly biodegradable polymer with good film-forming properties. It is currently mainly used for preparing functional packaging films. However, the functionalization of sodium alginate is mainly achieved by adding active substances to the film based on sodium alginate. Single sodium alginate cannot achieve functionalization, and the mechanical strength and barrier properties of the film prepared from single sodium alginate are low, which restricts its application in active packaging.

[0003] Ultraviolet (UV) is a part of the electromagnetic spectrum with a wavelength between visible light and X-rays. According to the wavelength, it can be divided into several wave bands: 1. UVA (long-wave ultraviolet): wavelength range: 320-400 nm, which can be used for ultraviolet curing (such as paint, ink drying), banknote detection (fluorescent substance excitation), ultraviolet lamp disinfection (part of the scene); 2. UVB (medium-wave ultraviolet): wavelength range: 280-320 nm, which is used in medicine to treat skin diseases such as psoriasis and vitiligo, and to promote vitamin D synthesis; 3. UVC (short-wave ultraviolet): wavelength range: 100-280 nm, which is used in water treatment, air purification, medical device disinfection (such as UV-C germicidal lamp), and cannot be directly contacted with the human body; 4. VUV (vacuum ultraviolet): wavelength range: 10-200 nm, which is used in scientific research fields (such as spectral analysis, plasma research), semiconductor manufacturing (photolithography technology); 5. EUV (extreme ultraviolet): wavelength range: 1-10 nm, which is mainly used in EUV lithography technology in high-end semiconductor manufacturing.

[0004] The anti-ultraviolet function of sodium alginate film in related technology mainly depends on the composite nanoparticles or organic ultraviolet absorbers, which has the problems of high cost and complex process. Therefore, it is of great significance to develop a sodium alginate film with anti-ultraviolet function without the need to composite other substances. SUMMARY

[0005] The present application aims to at least solve one of the above technical problems in the technical field, that is, to provide a preparation method of a sodium alginate film and application thereof. The anti-ultraviolet function of the sodium alginate film is directly given by glutaric anhydride esterification modification, which also improves the hydrophobicity and water vapor barrier property of the film, so that it can be used to make UVB protective film, etc.

[0006] To this end, in a first aspect of the present application, the present application provides a preparation method of sodium alginate film, comprising the following steps:

[0007] Sodium alginate is dissolved in deionized water, catalyst EDC and DMAP are added, and glutaric anhydride solution is added dropwise at 40-50°C, and after 1h of reaction, glutaric anhydride esterified sodium alginate is obtained by alcohol precipitation, washing and drying.

[0008] The glutaric anhydride esterified sodium alginate is prepared into a 2% w / v solution, 0.4% w / v glycerol is added as a plasticizer, and after ultrasonic degassing at 50°C for 30min, it is cast into a film and dried at 35°C, and after equilibration, a sodium alginate film is obtained.

[0009] According to the embodiments of the present application, after the sodium alginate is modified by glutaric anhydride, glutaric anhydride esterified sodium alginate is obtained, and the sodium alginate can have functional characteristics without being compounded with other substances; the film prepared from the glutaric anhydride esterified sodium alginate has enhanced ability to resist ultraviolet light in the partial short-wave ultraviolet range and the full mid-wave ultraviolet range, i.e. 200-320nm, and maintains good transmittance in the visible light range. In addition, after modification, the esterified sodium alginate becomes more hydrophobic, and the water vapor transmission rate of the film is lower than that of the original sodium alginate film. The glutaric anhydride esterified sodium alginate film is a degradable, non-toxic and harmless film, which can be used to make UVB protective film and potentially applied in the anti-ultraviolet function of, for example, glasses, to prevent damage to the skin surface around the eyes caused by long-term exposure to strong sunlight.

[0010] Optionally, the mass ratio of the catalyst EDC to DMAP is 2:1.

[0011] Optionally, the glutaric anhydride solution is obtained by dissolving anhydrous ethanol and glutaric anhydride at a ratio of 1:10 w:v.

[0012] Optionally, the glutaric anhydride solution is added dropwise at 40°C within 1h.

[0013] Optionally, the equilibration is carried out by placing the film in an environment with a relative humidity of 50±5% and a temperature of 25±5°C for 2 days.

[0014] In a second aspect of the present application, the application of the sodium alginate film prepared by the above preparation method in the preparation of UVB protective products is provided.

[0015] Optionally, the UVB protective products include anti-ultraviolet coatings for glasses, skin protective patches or protective layers for outdoor equipment.

[0016] In a third aspect of the present application, the application of the sodium alginate film prepared by the above preparation method in the preparation of food or pharmaceutical packaging materials is provided.

[0017] Optionally, the packaging material is used to protect oxidizable food or ultraviolet sensitive medicine.

[0018] In a fourth aspect of the present application, there is provided a use of the sodium alginate film prepared by the above-mentioned preparation method in the preparation of a medical protective material, wherein the medical protective material comprises a surgical instrument protective film or a phototherapy auxiliary isolation layer.

[0019] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Measurement results of the contact angle of the original sodium alginate and esterified sodium alginate powder according to the embodiment of the present application;

[0021] Figure 2 Measurement results of the water vapor transmission rate of the original sodium alginate and esterified sodium alginate film according to the embodiment of the present application;

[0022] Figure 3 Measurement results of the light transmittance curve of the original sodium alginate and esterified sodium alginate solution according to the embodiment of the present application, wherein B is the transmittance of the sodium alginate solution, and A is the transmittance of the sodium alginate film. DETAILED DESCRIPTION

[0023] The technical solutions of the present application are described below by means of specific examples. It should be understood that the one or more method steps mentioned in the present application do not exclude the presence of other method steps before and after the mentioned combination steps or the insertion of other method steps between the explicitly mentioned steps; it should also be understood that these examples are only used to illustrate the present application and do not limit the scope of the present application. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool to identify each method step, and is not a limitation on the arrangement order of each method step or a limitation on the scope of the present application. Changes or adjustments of the relative relationship, without substantial changes in the technical content, are also considered as the scope of the present application.

[0024] In order to better understand the above technical solutions, the exemplary embodiments of the present application are described in more detail below. Although exemplary embodiments of the present application are shown, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0025] The test materials used in the present application are all ordinary commercially available products and can be purchased in the market.

[0026] The application will be described with reference to specific examples, which are illustrative in nature and are not intended to limit the application in any way.

[0027] Example 1

[0028] Accurately weigh 200 mL of deionized water into a beaker, and then accurately weigh 8 g of sodium alginate with a weighing paper for standby. Place the beaker on a magnetic stirrer, and slowly pour the sodium alginate in multiple times at a speed of 300 rpm to prevent the sodium alginate from forming a lump, and stir until completely dissolved.

[0029] Glutaric anhydride is dissolved in anhydrous ethanol at a ratio of 1:10 (w:v) to obtain a glutaric anhydride solution. When the temperature of the sodium alginate solution rises to 40°C, 60 mL of 3% concentration glutaric anhydride solution is added (dropped within 1 h), and the reaction is continued for 1 h after the addition is completed.

[0030] After the reaction is completed, the modified sodium alginate solution is first alcohol precipitated with 95% industrial alcohol for 3 min, then washed with industrial alcohol for 4 times, and then placed in a 55°C oven for drying for 16-18 h; to obtain a modified sodium alginate sample.

[0031] Prepare a 2% modified sodium alginate solution of 25 mL, stir until it is completely dissolved, then add 0.1 g (0.4% w / v) of glycerol, and use a heating magnetic stirrer to stir at 50°C for 30 min, and then perform ultrasonic degassing to remove bubbles. Using a casting method, pour the film-forming solution into a disposable flat dish, and then place it in an electric heating constant temperature drying oven, dry at 35°C for 24 h, and then cool to form a film. After the glutaric anhydride esterified sodium alginate film is dried, it is peeled off from the culture dish, and then placed in an environment with a relative humidity of 50±5% and a temperature of 25±5°C for 2 days of balance, to obtain a sodium alginate film.

[0032] Example 2

[0033] Accurately weigh 200 mL of deionized water into a beaker, and then accurately weigh 8 g of sodium alginate with a weighing paper for standby. Place the beaker on a magnetic stirrer, and slowly pour the sodium alginate in multiple times at a speed of 300 rpm to prevent the sodium alginate from forming a lump, and stir until completely dissolved.

[0034] Glutaric anhydride is dissolved in anhydrous ethanol at a ratio of 1:10 (w:v) to obtain a glutaric anhydride solution; and EDC and DMAP are weighed according to a mass ratio of 2:1. When the temperature of the sodium alginate solution rises to 40°C, 60 mL of 3% concentration glutaric anhydride solution is added (dropped within 1 h), and the reaction is continued for 1 h after the addition is completed.

[0035] After the reaction, the modified sodium alginate solution was first alcohol precipitated for 3 min using 95% industrial alcohol, then washed 4 times with industrial alcohol, and then placed in a 55°C oven to dry for 16-18 h to obtain the modified sodium alginate sample.

[0036] A 2% modified sodium alginate solution 25 mL was prepared, stirred until it was completely dissolved, then 0.1 g (0.4% w / v) of glycerol was added, and after stirring at 50°C for 30 min using a heating magnetic stirrer, ultrasonic degassing was performed to remove bubbles. Using the flow casting method, the film forming solution was poured into a disposable flat dish, then placed in an electric heating constant temperature drying oven, dried at 35°C for 24 h, and then cooled to form a film. After the dried glutaric anhydride esterified sodium alginate film was peeled off from the culture dish, it was placed in an environment with a relative humidity of 50±5% and a temperature of 25±5°C for 2 days to obtain a sodium alginate film.

[0037] Example 3

[0038] Accurately weigh 200 mL of deionized water into a beaker, then accurately weigh 8 g of sodium alginate with a weighing paper, and set aside. Place the beaker on a magnetic stirrer, rotate at 300 rpm, slowly pour in the sodium alginate in several times to prevent the sodium alginate from clumping, and stir until completely dissolved.

[0039] Glutaric anhydride was dissolved with anhydrous ethanol according to a ratio of 1:10 (w:v) to obtain a glutaric anhydride solution; EDC and DMAP were weighed according to a mass ratio of 2:1. When the temperature of the sodium alginate solution rose to 50°C, 1 g of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and 0.5 g of 4-dimethylaminopyridine (DMAP) (catalyst) and 60 mL of 3% concentration glutaric anhydride solution were added (dropped in 1 h), and the reaction was continued for 1 h after the addition was completed.

[0040] After the reaction, the modified sodium alginate solution was first alcohol precipitated for 3 min using 95% industrial alcohol, then washed 4 times with industrial alcohol, and then placed in a 55°C oven to dry for 16-18 h to obtain the modified sodium alginate sample.

[0041] A 2% modified sodium alginate solution 25 mL was prepared, stirred until it was completely dissolved, then 0.1 g (0.4% w / v) of glycerol was added, and after stirring at 50°C for 30 min using a heating magnetic stirrer, ultrasonic degassing was performed to remove bubbles. Using the flow casting method, the film forming solution was poured into a disposable flat dish, then placed in an electric heating constant temperature drying oven, dried at 35°C for 24 h, and then cooled to form a film. After the dried glutaric anhydride esterified sodium alginate film was peeled off from the culture dish, it was placed in an environment with a relative humidity of 50±5% and a temperature of 25±5°C for 2 days to obtain a sodium alginate film.

[0042] Comparative Example

[0043] A 2% solution of sodium alginate (unmodified) was prepared in 25 mL of distilled water, stirred until completely dissolved, and 0.1 g (0.4% w / v) of glycerol was added. The solution was degassed by ultrasonic degassing after being stirred at 50°C for 30 min using a heating magnetic stirrer. The film-forming solution was poured into a disposable petri dish using the casting method, and the petri dish was placed in an electrically heated constant temperature drying oven and dried at 35°C for a period of time, and then cooled to form a film. The dried sodium alginate film was peeled off from the petri dish and equilibrated in an environment of 25 ± 5°C and 50 ± 5% relative humidity and temperature for 2 days to obtain a sodium alginate film.

[0044] Test Example

[0045] (1) Substitution degree determination method:

[0046] A 0.5 g sample of dried modified sodium alginate was dispersed in 50 mL of distilled water, and 3 drops of 1% (w / v) phenolphthalein were added as an indicator. A 0.2 mol / L NaOH solution was added to the suspension until it changed from colorless to pink to completely remove free carboxylic acid, and 5.0 mL of 0.1 mol / L NaOH solution was added to the mixture and saponified at 50°C for 1 h. A 0.1 mol / L HCl solution was placed in an acid burette, and the HCl solution was slowly added to the conical flask by manually controlling the burette valve, and the bottle was shaken during the addition. The titration was stopped when the pink color in the bottle disappeared and remained unchanged, and the volume V1 of HCl solution consumed was recorded. The same procedure was performed on the original sodium alginate sample (unmodified) to obtain the volume V0 of HCl solution consumed.

[0047] The calculation formula is as follows:

[0048]

[0049] In the formula: A is the content of the substituent group; V0 is the volume of HCl consumed by the blank sample, mL; V1 is the volume of HCl consumed by the esterified sample, mL; μ is the concentration of HCl, mol / L; W is the mass of the sample, g; C is the relative molecular mass of the substituent group; and 198 is the relative molecular mass of sodium alginate.

[0050] (2) Determination of hydrophobic interactions of sample powder

[0051] A 0.2 g sample of dried powder (sodium alginate sample) was sieved through a 100 mesh sieve and pressed into a thin sheet using a tablet press (pressure 20-25 Mpa). The contact angle of the sample surface was measured using a contact angle measuring instrument (CA-100C, Shanghai Yingnuo Precision Instrument Co., Ltd.) using the static drop method. A 4 μL water droplet was placed on the solid surface, and the liquid-solid-gas three-phase intersection tangent angle with the solid surface was measured by optical system image acquisition, and each sample was measured 3 times.

[0052] (3) Measurement of water vapor transmittance of film

[0053] The water vapor transmittance (WVTR) of the film was tested by weighing method. 5.0 g of anhydrous CaCl2 was weighed and placed in a reagent bottle, and the film sample was cut and fixed tightly on the bottle opening with a rubber band. The weighing bottle was placed in a sealed desiccator containing 30 mL of saturated NaCl solution at room temperature, and the weight of the reagent bottle was measured every 24 h, a total of 5 times, and each sample was measured 3 times. The WVTR of the film was calculated according to the following formula:

[0054]

[0055] Wherein, Δw / Δt is the mass increase rate (g / h), A is the exposed area of the film (m 2 ).

[0056] (4) Measurement of light transmittance of film and its solution

[0057] The prepared film solution and the prepared film (cut into a rectangular strip of 4 cm x 1 cm) were placed on the inner wall of a quartz cuvette, and an empty quartz cuvette was used as a blank to zero. The light transmittance of the film and its solution was scanned in the wavelength range of 200-800 nm using a UV spectrophotometer (U-T6A, Yishu Instruments). The UV-visible transmittance curve of the original sodium alginate and glutaric anhydride esterified sodium alginate film and its solution was drawn using Origin software.

[0058] The degree of substitution of sodium alginate and the film properties of Examples 1-3 and Comparative Examples are shown in Table 1. As can be seen from Table 1, after modification with glutaric anhydride, modified sodium alginate with different degrees of substitution can be obtained under different sample preparation conditions. The properties of the modified sodium alginate change with the degree of substitution. The increase in the degree of substitution can improve the hydrophobicity of the modified sodium alginate, and the increase in the hydrophobicity can reduce the water vapor transmittance of the film prepared from the modified sodium alginate, which is more conducive to maintaining the stability of the structure and properties of the film and the objects packaged or isolated by it.

[0059] Table 1 Measurement of degree of substitution of glutaric anhydride esterified sodium alginate and film properties under different conditions

[0060]

[0061] Table 2 shows the sodium alginate solutions of Examples 1-3 and the comparative examples and their transmittance in the 200-340 nm range. As can be seen from Table 2, after modification with glutaric anhydride, the modified sodium alginate solution and the prepared film have gradually enhanced UV resistance in the 200-320 nm UV light range with increasing degree of substitution. The unmodified original sodium alginate and the modified sodium alginate with a lower degree of substitution of 0.20 do not have this effect. Beyond 320 nm (330, 340 nm), the solutions and films of each sample maintain high transmittance.

[0062] Table 2. Transmittance of sodium alginate solution and film under different conditions in the 200-340 nm range.

[0063]

[0064]

[0065] The contact angle measurements of sodium alginate powder in Examples 1-3 and the comparative examples are as follows: Figure 1 As shown, by Figure 1 It can be seen that after modification with glutaric anhydride, the contact angle of the modified sodium alginate powder gradually increases with the increase of the degree of substitution. This indicates that sodium alginate becomes more hydrophobic, which is beneficial to reducing the water vapor permeability of the sodium alginate film in subsequent film preparation and is more conducive to maintaining the stability of the film.

[0066] The results of the water vapor transmission rate determination of sodium alginate membranes in Examples 1-3 and the comparative examples are as follows: Figure 2 As shown, by Figure 2 It can be seen that after modification with glutaric anhydride, as the degree of substitution increases, the water vapor permeability of the film prepared by modified sodium alginate decreases, which is more conducive to controlling the migration of moisture, protecting the packaged or isolated objects from the influence of humidity, and thus maintaining the stability of the packaged or isolated objects.

[0067] The results of the transmittance curves of sodium alginate membranes in Examples 1-3 and the comparative examples are as follows: Figure 3 As shown, by Figure 3 It is evident that, after modification with glutaric anhydride, the modified sodium alginate solution and its prepared film exhibit gradually enhanced UV resistance in the 200-320 nm ultraviolet range with increasing degree of substitution, while the control group (BS-SA) which underwent the same treatment but not modification did not show this effect. Furthermore, the modified sodium alginate film maintains good transmittance in the visible light range, suggesting its potential application in the preparation of UVB protective films.

[0068] In summary, according to the embodiments of the present application, the sodium alginate is modified by glutaric anhydride to obtain glutaric anhydride esterified sodium alginate, and the sodium alginate can have the functional characteristics without being compounded with other substances; the film prepared from the glutaric anhydride esterified sodium alginate has enhanced ability to resist ultraviolet light in the partial short-wave ultraviolet range and the full mid-wave ultraviolet range, i.e., 200-320 nm, and maintains good transmittance in the visible light range. In addition, after modification, the esterified sodium alginate becomes more hydrophobic, and the water vapor permeability of the film is lower than that of the original sodium alginate film. The glutaric anhydride esterified sodium alginate film is a degradable, non-toxic and harmless film, which can be used to make a UVB protective film and potentially applied in the anti-ultraviolet function of, for example, glasses to prevent damage to the skin surface around the eyes caused by long-term exposure to strong sunlight.

[0069] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and integrate different embodiments or examples described in the present specification.

[0070] Although the embodiments of the present application have been shown and described above, it should be understood that the above-described embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for preparing a sodium alginate film, characterized by, The method comprises the following steps: Sodium alginate is dissolved in deionized water, catalyst EDC and DMAP are added, and glutaric anhydride solution is added dropwise at 40-50℃, and after 1h of reaction, alcohol precipitation, washing and drying, esterified sodium alginate is obtained; The esterified sodium alginate is prepared into a 2% w / v solution, 0.4% w / v glycerol is added as a plasticizer, and after ultrasonic degassing at 50℃ for 30min, film casting is performed and drying is performed at 35℃, and after equilibration, sodium alginate film is obtained.

2. The production method according to claim 1, wherein The mass ratio of the catalyst EDC to DMAP is 2:

1.

3. The production method according to claim 1, wherein The glutaric anhydride solution is obtained by dissolving anhydrous ethanol and glutaric anhydride at 1:10 w:v.

4. The production method according to claim 1, wherein The glutaric anhydride solution is added dropwise at 40℃ within 1h.

5. The production method according to claim 1, wherein Equilibration is performed by placing in a temperature and humidity environment of 25±5℃ and 50±5% relative humidity for 2 days.

6. Application of the sodium alginate film prepared by the preparation method of any one of claims 1-5 in the preparation of a UVB protection product.

7. Use according to claim 6, wherein The UVB protection product includes an anti-ultraviolet coating for glasses, a skin protection patch or a protective layer for outdoor equipment.

8. Application of the sodium alginate film prepared by the preparation method of any one of claims 1-5 in the preparation of food or pharmaceutical packaging materials.

9. Use according to claim 8, wherein the compound is ###0002### The packaging materials are used for protecting oxidizable food or ultraviolet-sensitive drugs.

10. Use of the sodium alginate film prepared by the process according to any one of claims 1-5 for the preparation of a medical protective material, characterized in that, The medical protective materials include a protective film for surgical instruments or a light therapy auxiliary isolation layer.

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