CN115322544B

CN115322544B - Preparation method of colored microspheres and method for preparing color-changing film by using colored microspheres

Info

Publication number: CN115322544B
Application number: CN202210999270.2A
Authority: CN
Inventors: 赵娜; 马志刚; 崔文广; 胡江浦; 王昆
Original assignee: Shijiazhuang University
Current assignee: Shijiazhuang University
Priority date: 2022-08-19
Filing date: 2022-08-19
Publication date: 2023-06-09
Anticipated expiration: 2042-08-19
Also published as: CN115322544A

Abstract

The invention discloses a preparation method of a color-changing film, which comprises the steps of firstly synthesizing a copolymer of acrylic acid and p-vinylbenzyl trimethyl ammonium chloride by a solution polymerization method, then combining the copolymer with dye through ionic bond, and adding a cross-linking agent mannitol to form a colored water phase; uniformly stirring oil and span 60 to form an oil phase, dripping the aqueous phase solution into the oil phase, heating to crosslink the copolymer to form colored hydrogel microspheres, and filtering, washing, drying and grinding to obtain colored microsphere powder; the colored microsphere powder absorbs a certain amount of water to become hydrogel microspheres; dissolving polycaprolactone PCL in dichloromethane, and adding calcium carbonate to play a role in shading color to form a polymer solution; mixing the colored hydrogel microspheres with a polymer solution, casting to form a film, removing dichloromethane, and forming CaCO ₃ PCL composite membrane. Over time, the film will gradually develop the color of the colored microspheres, which in turn will change color.

Description

Preparation method of colored microspheres and method for preparing color-changing film by using colored microspheres

Technical Field

The invention relates to the technical field of color-changing materials, in particular to a preparation method of colored microspheres and a method for preparing a color-changing film by using the colored microspheres.

Background

The manufacturer pre-packages food, medicine and the like in a container for delivery to a consumer, the labeling content of the food label printed on the outer package usually contains basic information of products such as product names, storage modes, production addresses, shelf life and the like, and besides the commodity for labeling the shelf life can be avoided according to the regulations, and other label shelf life is required on the outer package. The food and the medicine which are eaten for a long time can cause great harm to the health.

At present, a producer usually sprays a production date on an outer package of a product, fonts are small and are easy to be confused with a background pattern of the package, when a consumer purchases the product, the quality guarantee period and the production date are often required to be found on the package and cannot be visually seen, the purchase time is additionally increased, the goodness of the purchaser to a target commodity is reduced, and the purchase decision of the consumer is influenced. Therefore, if the method for conveniently and intuitively displaying the quality guarantee period of the commodity is provided, the consumer's good sensitivity to the target commodity can be improved, and the shopping experience can be improved.

The patent with the application number of 201711081731.3 and the name of intelligent egg shelf life indication label adopts physicochemical properties of starch, amylase and iodine, and the freshness of eggs is displayed through color change generated by interaction between the starch, amylase and iodine. The use process and equipment are complex, the concentration and the dosage of starch, amylase and iodine need to be frequently regulated, and the method is not suitable for common commodity packaging.

The application number is 201911242652.5, and the patent with the name of 'an intelligent color-changing packaging device and a color-changing method' discloses an intelligent color-changing packaging device capable of changing color along with time, wherein a plurality of photochromic units, controllers and timers are arranged on product packages, the timers record the time length of products after leaving factories, and the controllers control light sources in the corresponding photochromic units to be lightened so that the color of the product packages can be changed according to the time length of leaving the factories, thereby more intuitively reminding consumers of the production date and the quality guarantee period of the products and enabling the consumers to quickly acquire information about whether the products expire soon. The technology has higher cost, a set of device is required to be arranged on the package of each product, the device is not suitable for low-price commodities, and more waste and pollution are generated after the package is abandoned.

Therefore, the invention aims to prepare the film with the color changing along with the time, which is attached to the package before the commodity leaves the factory, and the longer the production date is, the darker the color is, so as to play a role in reminding consumers of paying attention to the shelf life.

However, the color-changing film in the prior art mostly changes in color according to the temperature, pH value, illumination condition, electric field condition, radiation condition, pressure and the like in the environment, and cannot meet the requirement that the color of the commodity packaging film needs to change according to different time.

Disclosure of Invention

The invention aims to provide a preparation method of colored microspheres and a method for preparing a color-changing film by using the colored microspheres. The color-changing film may undergo a color change over time.

The technical scheme of the invention is as follows:

a method for preparing a color-changeable film, comprising the steps of:

(1) Preparing a copolymer aqueous solution of acrylic acid and p-vinylbenzyl trimethyl ammonium chloride by a solution polymerization method;

(2) Dropwise adding the copolymer aqueous solution obtained in the step (1) into the reactive dye aqueous solution under stirring, and dyeing at room temperature to obtain a reactive dye/copolymer aqueous solution;

(3) Adding cross-linking agent mannitol into the reactive dye/copolymer aqueous solution, wherein the addition amount of mannitol is 18-22% of the mass of the copolymer of acrylic acid and p-vinylbenzyl trimethyl ammonium chloride prepared in the step (1), and stirring and dissolving to obtain aqueous phase solution;

(4) Uniformly stirring peanut oil and a dispersant span 60 to form an oil phase, dripping the aqueous phase solution prepared in the step (3) into the oil phase at a dripping speed of 6mL per minute to form a water-in-oil type suspension system, heating to 68-72 ℃, reacting for 4-4.5 hours, crosslinking the acrylic acid and the p-vinylbenzyl trimethyl ammonium chloride copolymer prepared in the step (1), filtering out solid matters, washing, drying and grinding to form colored microspheres;

(5) Allowing the dried colored microspheres to absorb a certain amount of water to form colored hydrogel microspheres, wherein the water absorption is 10% of the mass of the dried colored microspheres;

(6) Dissolving polycaprolactone in dichloromethane, adding calcium carbonate powder, and stirring and mixing uniformly to obtain a polymer solution;

(7) Mixing the colored hydrogel microspheres prepared in the step (5) with the polymer solution prepared in the step (6), casting to form a film, removing dichloromethane, and forming CaCO (CaCO) coating the colored hydrogel microspheres ₃ PCL composite membrane.

Preferably, the preparation method of the copolymer aqueous solution of acrylic acid and p-vinylbenzyl trimethyl ammonium chloride comprises the following steps:

adding distilled water, initiator ammonium persulfate and cationic monomer p-vinylbenzyl trimethyl ammonium chloride into a reaction vessel, stirring at the speed of 500r/min, and continuously introducing nitrogen to dissolve the ammonium persulfate and the p-vinylbenzyl trimethyl ammonium chloride;

adding monomer acrylic acid and isopropyl alcohol as a molecular weight regulator, and heating to 70 ℃ to obtain a reaction solution;

dissolving acrylic acid and ammonium persulfate in distilled water to form a dripping solution;

and (3) dripping the dripping solution into the reaction solution within 30-40 minutes, and continuously refluxing at 94 ℃ for 1.5 hours to obtain the copolymer aqueous solution of the acrylic acid and the p-vinylbenzyl trimethyl ammonium chloride.

Preferably, the reaction liquid comprises distilled water, ammonium persulfate, p-vinylbenzyl trimethyl ammonium chloride, acrylic acid and isopropanol in the mass ratio of: 100:1:1.2:5:4;

the mass ratio of the acrylic acid, the ammonium persulfate and the distilled water in the dropping liquid is as follows: 40:2:40.

Preferably, the volume ratio of the reactive dye aqueous solution to the copolymer aqueous solution in the step (2) is 1-10:25; the stirring speed was 500r/min, the dropping speed was 15 mL/min, and the dyeing time was 1 hour.

Preferably, the reactive dye is one or more of amaranth, reactive black 5, reactive yellow 95, reactive red 24, reactive brilliant blue X-BR, reactive blue 49 and reactive blue 19; in the reactive dye aqueous solution, the mass volume ratio of the reactive dye is 100g/L.

Preferably, the volume ratio of the water phase to the oil phase in the step (4) is 1:3; the addition amount of span 60 is 6% of the mass of the aqueous phase solution; the stirring speed is 500r/min; after the reaction is finished, stirring and cooling to room temperature, filtering out solid matters, cleaning with detergent, and putting the filtered product into a vacuum drying oven for drying, wherein the vacuum degree is 100Pa, the drying temperature is 60 ℃, and the drying time is 2 days. The dried product was ground and filtered through a 200 mesh sieve to give a powdery product.

Preferably, the mass-volume ratio of polycaprolactone to dichloromethane in the step (6) is 1:5; the mass ratio of the calcium carbonate powder to the polycaprolactone is 1-2.5:1; the particle size of the calcium carbonate powder is 0.1-10 microns.

Preferably, the mass ratio of the colored hydrogel microspheres to the polycaprolactone in the step (7) is 0.05-0.6:1.

Preferably, the method for removing dichloromethane in the step (7) comprises the following steps: after the film is molded in a fume hood at room temperature, the film is placed in a vacuum drying oven, and the film is vacuumized to 100Pa at room temperature and then taken out after 5 hours.

The invention has the beneficial effects that:

the film will change color with time, the further the film is from the date of production, the darker the color is, thus the film can play a role in reminding consumers of the shelf life of the commodity. The display effect is visual and simple, the time of consumers is saved, and the satisfaction degree of the consumers is improved. The specific aspects are as follows:

1. cationic monomer p-vinylbenzyl trimethyl ammonium chloride is introduced into polyacrylic acid, and the cation on the monomer can form ionic bond with the anion in amaranth aqueous solution, so that the binding force of the polymer and the reactive dye is enhanced, and the dyeing effect of the dye is more uniform and durable.

2. Firstly, introducing dye, and then enabling polyacrylic acid part and mannitol in the copolymer to be crosslinked through esterification reaction, wherein the dye is uniformly distributed in the crosslinked microsphere.

3. The addition of calcium carbonate can mask the color, making the film initially appear light. The copolymer is crosslinked and has unreacted carboxyl, and the polycaprolactone is slowly degraded with the action of water and carboxyl in the hydrogel, so that calcium carbonate is partially fallen off, the color of the microsphere is displayed, the longer the time is, the more serious the polycaprolactone is degraded, the more the color of the microsphere is displayed, and the darker the color of the film is.

4. Calcium carbonate was initially used to mask the color of the colored microspheres. In the acidic microenvironment of the colored hydrogel microspheres, the calcium carbonate is gradually dissolved in a small amount, so that the shielding effect is reduced, and the film gradually presents the color of the colored microspheres, so that the color is deepened.

5. The film prepared by the invention is cut into small pieces and is stuck on the surface of food or medicine package, thus playing the role of reminding consumers of paying attention to the quality guarantee period and having low cost. The raw materials for preparing the film are degradable polymers, and the environment is not polluted after the film is discarded.

6. The color-changing film provided by the invention is used for packaging, the color of the film gradually gets darker as time passes, the longer the time interval production date is, the darker the color is, the more visual the presentation effect is, and the satisfaction degree of consumers is improved.

Drawings

FIG. 1 is a schematic illustration of the copolymerization of acrylic acid and para-vinylbenzyl trimethylammonium chloride;

FIG. 2 is a schematic representation of the formation of ionic bonds between a copolymer of acrylic acid and para-vinylbenzyl trimethylammonium chloride and amaranth;

FIG. 3 is a schematic diagram of the structure of the cross-linked reaction product of the copolymer of acrylic acid and p-vinylbenzyl trimethylammonium chloride and mannitol after dyeing; wherein P is a copolymer skeleton, M is mannitol, and A is amaranth.

FIG. 4 dried colored microsphere powder prepared in example 2;

FIG. 5 dried colored microsphere powder prepared in example 3;

FIG. 6 dried colored microsphere powder prepared in example 4;

FIG. 7 colored films prepared in examples 5-8 and color change.

Detailed Description

In order to make the technical solution and advantages of the present invention more apparent, the present invention will be further described with reference to specific examples. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

1. Preparation of an aqueous copolymer solution of acrylic acid and p-vinylbenzyl trimethylammonium chloride by solution polymerization: distilled water, initiator ammonium persulfate and cationic monomer p-vinylbenzyl trimethyl ammonium chloride are added into a reaction vessel; stirring at the speed of 500r/min, continuously introducing nitrogen, dissolving ammonium persulfate and p-vinylbenzyl trimethyl ammonium chloride, adding monomer acrylic acid and molecular weight regulator isopropanol, and heating to 70 ℃ to obtain a reaction solution; the reaction liquid comprises distilled water, ammonium persulfate, p-vinylbenzyl trimethyl ammonium chloride, acrylic acid and isopropanol in the mass ratio of: 100:1:1.2:5:4; dissolving acrylic acid and ammonium persulfate in distilled water to form a dripping solution, wherein the mass ratio of the acrylic acid to the ammonium persulfate to the distilled water in the dripping solution is as follows: dripping the dripping liquid into the reaction liquid within 30-40 minutes in a ratio of 40:2:40; reflux is carried out for 1.5h at 94 ℃ to obtain the copolymer aqueous solution of acrylic acid and p-vinylbenzyl trimethyl ammonium chloride. The schematic of the copolymerization of acrylic acid and p-vinylbenzyl trimethylammonium chloride is shown in FIG. 1.

2. Dropwise adding the copolymer aqueous solution in the step 1 into the reactive dye aqueous solution under stirring, and dyeing at room temperature to obtain a reactive dye/copolymer aqueous solution; the reactive dye is one or more of amaranth, reactive black 5, reactive yellow 95, reactive red 24, reactive brilliant blue X-BR, reactive blue 49 and reactive blue 19; in the reactive dye aqueous solution, the mass volume ratio of the reactive dye is 100g/L.

The volume ratio of the reactive dye aqueous solution to the copolymer aqueous solution is: 1-10:25; the stirring speed was 500r/min, the dropping speed was 15 mL/min, and the dyeing time was 1 hour. The preferred reactive dyes are amaranth and reactive red 24, and the preferred volume ratio of the aqueous reactive dye solution to the aqueous copolymer solution is as follows: 10:25. The schematic of the formation of ionic bonds between the copolymer of acrylic acid and p-vinylbenzyl trimethylammonium chloride and amaranth is shown in FIG. 2.

3. Adding mannitol serving as a cross-linking agent into the reactive dye/copolymer aqueous solution, wherein the addition amount of mannitol is 20% of the mass of the copolymer, and stirring and dissolving to obtain aqueous phase solution;

4. adding peanut oil and dispersant span 60 into a four-neck flask, stirring uniformly to form an oil phase, dripping the aqueous phase solution prepared in the step 3 into the oil phase at a dripping speed of 6mL per minute to form a water-in-oil suspension system, heating to 68-72 ℃, and reacting for 4-4.5 hours to crosslink the copolymer, wherein the structural schematic diagram of the dyed copolymer and mannitol crosslinked reaction product is shown in figure 3. Filtering out solid, washing with a commercially available detergent, filtering, vacuum drying, and grinding to obtain colored microsphere powder; the volume ratio of the water phase to the oil phase is 1:3, the adding amount of span 60 is 6% of the mass of the water phase solution, and the stirring speed is 500r/min.

5. The dried colored microspheres were allowed to absorb a certain amount of water to form hydrogel microspheres with a water absorption of 10% of the mass of the dried microspheres.

6. Dissolving polycaprolactone PCL in dichloromethane, adding calcium carbonate powder, and stirring and mixing uniformly to obtain a polymer solution; the mass volume ratio of the polycaprolactone to the dichloromethane is 1:5, the mass ratio of the calcium carbonate powder to the polycaprolactone is 1-2.5:1, and the particle size of the calcium carbonate powder is 0.1-10 microns. The preferred mass ratio of calcium carbonate powder to polycaprolactone is 2:1.

7. Mixing the colored hydrogel microspheres prepared in the step 5 with the polymer solution prepared in the step 6, casting to form a film, and vacuum drying at room temperature to remove dichloromethane to form light pink CaCO coated with the colored hydrogel microspheres ₃ PCL composite membrane. The mass ratio of the colored hydrogel microspheres to the polycaprolactone is 0.3-0.6:1. The preferred mass ratio of colored hydrogel microspheres to polycaprolactone is 0.3:1.

Example 1

Preparation of an aqueous copolymer solution of acrylic acid and p-vinylbenzyl trimethylammonium chloride by solution polymerization: 100mL of distilled water, 1g of initiator ammonium persulfate and 1.2g of cationic monomer p-vinylbenzyl trimethyl ammonium chloride are added into a reaction vessel; stirring at the speed of 500r/min, continuously introducing nitrogen, dissolving ammonium persulfate and p-vinylbenzyl trimethyl ammonium chloride, adding 5g of monomer acrylic acid and 4g of molecular weight regulator isopropanol, and heating to 70 ℃ to obtain a reaction solution; dissolving 40g of acrylic acid and 2g of ammonium persulfate in 40mL of distilled water to form a dropwise liquid, and dropwise adding the dropwise liquid into the reaction liquid within 30-40 minutes; reflux is carried out for 1.5h at 94 ℃ to obtain the copolymer aqueous solution of acrylic acid and p-vinylbenzyl trimethyl ammonium chloride.

Example 2

Preparing amaranth water solution with the mass-volume ratio of 100g/L, dropwise adding 25mL of the copolymer water solution prepared in the example 1 into 1mL of the amaranth water solution at the stirring speed of 500r/min, and dyeing at room temperature to obtain the reactive dye/copolymer water solution. The dropping speed is 5 drops per second, and the dyeing time is 1 hour.

Adding 1.2g of cross-linking agent mannitol into the reactive dye/copolymer aqueous solution, stirring and dissolving to obtain aqueous phase solution; 60mL of peanut oil and 1.35g of dispersant span 60 are added into a four-necked flask and stirred uniformly at the stirring speed of 500r/min to form an oil phase; and (3) dropwise adding 20mL of aqueous phase solution into the oil phase at a dropwise speed of 2 drops per second to form a water-in-oil suspension system, heating to 70 ℃, reacting for 4 hours to crosslink the copolymer, stirring and cooling to room temperature after the reaction is finished, filtering out solid matters, cleaning with detergent, and placing the filtered products into a vacuum drying oven for drying at a vacuum degree of 100Pa and a drying temperature of 60 ℃ for 2 days. The dried product was ground and filtered through a 200 mesh sieve to give a powdery product.

Example 3

Preparing amaranth water solution with the mass-volume ratio of 100g/L, dropwise adding 25mL of the copolymer water solution prepared in the example 1 into 3mL of the amaranth water solution at the stirring speed of 500r/min, and dyeing at room temperature to obtain the reactive dye/copolymer water solution. The dropping speed is 5 drops per second, and the dyeing time is 1 hour.

Adding 1.2g of cross-linking agent mannitol into the reactive dye/copolymer aqueous solution, stirring and dissolving to obtain aqueous phase solution;

60mL of peanut oil and 1.35g of dispersant span 60 are added into a four-necked flask and stirred uniformly at the stirring speed of 500r/min to form an oil phase; 20mL of the aqueous solution was dropped into the oil phase at a drop rate of 2 drops per second to form a water-in-oil suspension, the temperature was raised to 70℃and the reaction was carried out for 4 hours to crosslink the copolymer, the solid was filtered off, and the washing and drying were carried out in the same manner as in example 2.

Example 4

Preparing amaranth water solution with the mass-volume ratio of 100g/L, dropwise adding 25mL of the copolymer water solution prepared in the example 1 into 10mL of the amaranth water solution at the stirring speed of 500r/min, and dyeing at room temperature to obtain the reactive dye/copolymer water solution. The dropping speed is 5 drops per second, and the dyeing time is 1 hour.

As can be seen from fig. 4-6, the prepared microsphere powder is darker as the amaranth content increases.

Example 5

0.5g of the dried colored microsphere powder prepared in example 2 was weighed and 0.05g of water was absorbed to form hydrogel microspheres.

Weighing 2g of polycaprolactone, dissolving in 10mL of dichloromethane, adding 2.5g of calcium carbonate powder and the hydrogel microsphere, stirring and mixing uniformly, casting to form a film, placing the film into a vacuum drying oven, vacuumizing to 100Pa at room temperature, taking out a sample after 5 hours, so that the dichloromethane is completely removed, and forming light pink CaCO wrapping the colored hydrogel microsphere ₃ PCL composite membrane. The colored film is placed in the room for different time, and the color change of the film is recorded by photographing. The indoor humidity is 20-80%, the temperature is 15-35 ℃, and the indoor humidity is matched with the environment where common commodity packages are located.

Example 6

1g of the dried colored microsphere powder prepared in example 3 was weighed and 0.1g of water was absorbed to form hydrogel microspheres.

Weighing 2g of polycaprolactone, dissolving in 10mL of dichloromethane, adding 5g of calcium carbonate powder and addingThe hydrogel microspheres are stirred and mixed uniformly and then cast into a film, methylene dichloride is removed by the method of the example 5, and CaCO coated with the colored hydrogel microspheres in a light pink color is formed ₃ PCL composite membrane. The colored film is placed in the room for different time, and the color change of the film is recorded by photographing. The film was in the same environment as in example 5.

Example 7

0.5g of the dried colored microsphere powder prepared in example 3 was weighed and 0.05g of water was absorbed to form hydrogel microspheres.

Weighing 2g of polycaprolactone, dissolving in 10mL of dichloromethane, adding 4g of calcium carbonate powder and the hydrogel microspheres, stirring and mixing uniformly, casting to form a film, removing dichloromethane by the method of example 5 to form light pink CaCO coated with the colored hydrogel microspheres ₃ PCL composite membrane. The colored film is placed in the room for different time, and the color change of the film is recorded by photographing. The film was in the same environment as in example 5.

Example 8

0.5g of the dried colored microsphere powder prepared in example 4 was weighed and 0.05g of water was absorbed to form hydrogel microspheres.

The photographs of all samples are summarized in fig. 7, and it can be seen from fig. 7 that the sample of example 5 has a poor effect of masking the color due to less calcium carbonate being added, and the initial color is slightly darker than the other samples. The color of the selected colored microsphere is lighter, and the addition amount is small, so that the color change is less obvious than other samples in the subsequent degradation process. The calcium carbonate added in example 6 was the most, up to 5g, so that the effect of masking the color was good and the initial color was light. The color of the selected colored microspheres is darker and the addition amount is the greatest, so that more colored microspheres are exposed along with the partial dissolution of calcium carbonate and the falling of the calcium carbonate caused by the degradation of polycaprolactone in the subsequent degradation process, and the color change is obvious. However, because of the large amount of calcium carbonate added, the film was less flexible and the brittleness was greatest in all samples. Example 7 the amount of coloured microspheres and the amount of calcium carbonate added is between examples 5 and 6, so the colour change is also between the two, and the flexibility of the film is also between the two. The colored microspheres selected in example 8 were the darkest in color and therefore the most visible in film color change, and the film color after degradation was darker than the other samples, with a calcium carbonate loading of 4g, and therefore the film flexibility was better than the sample of example 6.

Claims

1. A method for preparing a color-changeable film, comprising the steps of:

(4) Uniformly stirring peanut oil and a dispersant span 60 to form an oil phase, dripping the aqueous phase solution prepared in the step (3) into the oil phase at a dripping speed of 6mL per minute to form a water-in-oil suspension system, heating to 68-72 ℃, reacting for 4-4.5 hours to crosslink the acrylic acid and the p-vinylbenzyl trimethyl ammonium chloride copolymer prepared in the step (1), filtering out solid matters, washing, drying and grinding to form colored microsphere powder;

(5) Allowing the dried colored microsphere powder to absorb a certain amount of water to form colored hydrogel microspheres, wherein the water absorption is 10% of the mass of the dried colored microsphere powder;

2. The method for producing a color-changeable film according to claim 1, wherein the method for producing an aqueous copolymer solution of acrylic acid and p-vinylbenzyl trimethyl ammonium chloride comprises the steps of:

3. The preparation method of the color-changeable film according to claim 2, wherein the mass ratio of distilled water, ammonium persulfate, p-vinylbenzyl trimethyl ammonium chloride, acrylic acid and isopropanol in the reaction liquid is: 100:1:1.2:5:4;

4. The method for producing a color-changeable film according to claim 1, wherein the volume ratio of the aqueous reactive dye solution to the aqueous copolymer solution in the step (2) is 1-10:25; the stirring speed was 500r/min, the dropping speed was 15 mL/min, and the dyeing time was 1 hour.

5. The method for preparing a color-changeable film according to claim 4, wherein the reactive dye is one or more of amaranth, reactive black 5, reactive yellow 95, reactive red 24, reactive brilliant blue X-BR, reactive blue 49, reactive blue 19; in the reactive dye aqueous solution, the mass volume ratio of the reactive dye is 100g/L.

6. The method for producing a color-changeable film according to claim 1, wherein the volume ratio of the aqueous phase to the oil phase in the step (4) is 1:3; the addition amount of span 60 is 6% of the mass of the aqueous phase solution; the stirring speed is 500r/min; after the reaction is finished, stirring and cooling to room temperature, filtering out solid matters, cleaning with detergent, and putting the filtered product into a vacuum drying oven for drying, wherein the vacuum degree is 100Pa, the drying temperature is 60 ℃, and the drying time is 2 days;

the dried product was ground and filtered through a 200 mesh sieve to give a powdery product.

7. The method for producing a color-changeable film according to claim 1, wherein the mass-to-volume ratio of polycaprolactone to dichloromethane in the step (6) is 1:5; the mass ratio of the calcium carbonate powder to the polycaprolactone is 1-2.5:1; the particle size of the calcium carbonate powder is 0.1-10 microns.

8. The method for producing a color-changeable film according to claim 1, wherein the mass ratio of the colored hydrogel microspheres to polycaprolactone in the step (7) is 0.05-0.6:1.

9. The method for producing a color-changeable film according to claim 1, wherein the method for removing methylene chloride in the step (7) comprises: after the film is molded in a fume hood at room temperature, the film is placed in a vacuum drying oven, and the film is vacuumized to 100Pa at room temperature and then taken out after 5 hours.