CN112852402B

CN112852402B - Durable thermochromic material, preparation method thereof and application thereof in textiles

Info

Publication number: CN112852402B
Application number: CN202011524720.XA
Authority: CN
Inventors: 钟欣; 曾国坪; 胡凯
Original assignee: Xiamen Anta Sports Goods Co Ltd
Current assignee: Xiamen Anta Sports Goods Co Ltd
Priority date: 2020-12-22
Filing date: 2020-12-22
Publication date: 2023-06-23
Anticipated expiration: 2040-12-22
Also published as: CN112852402A

Abstract

The invention provides a lasting thermochromic material, a preparation method thereof and application thereof in textiles, wherein the thermochromic material has a microcapsule structure, a thermosensitive color-changing organic dye is used as a core material of a microcapsule, and the core material is sequentially coated with a first capsule wall and a second capsule wall; the first capsule wall is formed by polymerization of polyvinyl alcohol and n-butyraldehyde, and the second capsule wall is formed by reaction of an ultraviolet resistant agent, polyvinyl alcohol and n-butyraldehyde. Compared with the existing products on the market, the durability of the thermochromic material is greatly improved. In addition, as the double-layer coating form of the invention can coat various color-changing system components and keep stable, the color development is not influenced, the protection of the core material is better, the material is not easy to leak out, and the washing fastness and the durability are good. The thermochromic material provided by the invention has higher reversible color-changing durability, and is beneficial to long-term use of the color-changing textile.

Description

Durable thermochromic material, preparation method thereof and application thereof in textiles

Technical Field

The invention relates to the technical field of textile fabrics, in particular to a durable thermochromic material, a preparation method thereof and application thereof in textiles.

Background

In modern life, consumers have increasingly strong demands for interesting clothing, and color-changeable clothing fabrics are one type. The color-changeable textile fabric is mainly realized by compounding color-changeable functional materials. As a large class of color-changing materials, thermochromic materials are also called as thermochromic materials (or thermochromic materials for short), which are a class of materials that can change color with changes in external temperature, and the temperature at which the color changes is called as the color-changing temperature. The organic reversible thermochromic material used in spinning has the characteristics of sensitive and quick color change, large color change temperature selectable range, bright color and the like. The color change mechanism of the color change material is that protons in thermochromic compound molecules are transferred due to the increase of temperature, so that the molecular structure is changed, and a reversible thermochromic phenomenon is generated.

The thermochromatic organic dye consists of leuco dye, color developing agent, temperature regulator, sensitizer, etc. the leuco dye is one matter capable of developing color in combination with proton, such as lactone compound, and the color change is determined as the electron supplying part in the color changing system and the developed color changes with the substituent. However, the conjugated system in the molecule is interrupted, and the reaction with the color-developing agent is required to develop color under certain conditions. The color developing agent is an acid releasing compound capable of reversibly releasing protons, namely an electron withdrawing compound, and determines the color depth. The temperature regulator mainly influences the thermochromic temperature, and when the temperature regulator is melted, the color developing agent is separated from the leuco dye, so that the formation of a conjugated system is hindered, and the system is in a colorless state. For example, the leuco dye is crystal violet lactone and is a color-changing system of bisphenol A as a color-developing agent, and after the leuco dye is cooled to a certain temperature, the bisphenol A emits protons in a certain medium to obtain electrons, the crystal violet lactone is subjected to ring opening, molecular rearrangement, conjugated double bond penetration and bisphenol A ion combination, so that the color is presented.

At present, the thermochromic printing on textiles adopts thermochromic paint, namely, after the thermochromic organic dye is processed into microcapsules, the thermochromic organic dye is printed on the textiles by adopting a paint printing process mode. Most of the thermosensitive color-changing coating products are reversible single-layer temperature-changing microcapsules in the market. Wherein the chemical property of the temperature change material used as the core material is relatively active and is easy to be influenced by light. The existing temperature-change microcapsule products on the market all have the problem that the temperature change is easy to lose efficacy, and particularly cannot be used for a long time under illumination, for example, the textile fabric with color-change printing under strong sunlight is used outdoors for several times, namely, the textile fabric loses efficacy.

Disclosure of Invention

In view of the above, the invention provides a durable thermochromic material, a preparation method thereof and application thereof in textiles.

The invention provides a lasting thermochromic material which has a microcapsule structure, wherein a thermosensitive color-changing organic dye is used as a core material of a microcapsule, and the core material is sequentially coated with a first capsule wall and a second capsule wall; the first capsule wall is formed by polymerization of polyvinyl alcohol and n-butyraldehyde, and the second capsule wall is formed by reaction of an ultraviolet resistant agent, polyvinyl alcohol and n-butyraldehyde.

Preferably, the thermochromic organic dye includes crystal violet lactone and a color developer, the color developer being any one of phenol, bisphenol a, calcium chloride, stearic acid, lunar silicic acid, and boric acid.

Preferably, the ultraviolet resistance agent is titanium dioxide and/or an ultraviolet absorber.

The invention provides a preparation method of a durable thermochromic material, which comprises the following steps:

s1, providing single-layer microcapsule powder; the single-layer microcapsule powder consists of thermochromic organic dye and a coated capsule wall; the capsule wall is formed by polymerization of polyvinyl alcohol and n-butyraldehyde;

s2, mixing the single-layer microcapsule powder, the ultraviolet resistant agent, the polyvinyl alcohol and the n-butyraldehyde in an aqueous solvent, stirring to enable water to permeate into the single-layer microcapsule, and heating to react to obtain the durable thermochromic material with the double-layer capsule wall.

Preferably, the thermochromic organic dye comprises crystal violet lactone and a color developer; the single-layer microcapsule powder is obtained according to the following steps:

mixing the crystal violet lactone and the color developing agent in a solvent in a molten state, heating, preserving heat for reaction, and cooling to obtain a dark blue solid; the solvent is preferably one or more of dodecanol, tetradecanol, hexadecanol, octadecanol, paraffin, lauric acid, glycerol laurate, n-butyl stearate, glycerol monostearate, phenyl salicylate, and azoxyanisole;

preparing the deep blue solid, an emulsifying agent and water into core material emulsion;

and adding a prepolymer solution formed by polyvinyl alcohol and n-butyraldehyde into the core material emulsion under the stirring condition, reacting at constant temperature, and separating to obtain single-layer microcapsule powder.

Preferably, the mass ratio of the crystal violet lactone to the color developer is 2-3:4-6; the mass ratio of polyvinyl alcohol to n-butyraldehyde forming the prepolymer solution is 20-30:15-20.

Preferably, in the step S2, 20 to 30 parts of the single-layer microcapsule powder, 5 to 10 parts of the ultraviolet resistance agent, 10 to 20 parts of polyvinyl alcohol and 10 to 15 parts of n-butyraldehyde are mixed in an aqueous solvent according to parts by mass.

Preferably, in the step S2, the reaction temperature is 70-80 ℃, the pH value is 4-6, and the reaction time is 3-4h.

The invention provides a printing paste comprising the durable thermochromic material.

The invention provides a printed fabric, which is prepared by printing fabrics with the printing paste.

Compared with the prior art, the invention provides a microcapsule color-changing material with double-layer capsule walls, wherein the first capsule wall and the second capsule wall are coated with core material thermosensitive color-changing organic dye in a double-layer manner, the first capsule wall is formed by polymerizing polyvinyl alcohol and n-butyraldehyde, and the second capsule wall is formed by reacting ultraviolet resistant agent, polyvinyl alcohol and n-butyraldehyde. Compared with the existing products on the market, the durability of the thermochromic material is greatly improved. In addition, as the double-layer coating form of the invention can coat various color-changing system components and keep stable, the color development is not influenced, the protection of the core material is better, the material is not easy to leak out, and the washing fastness and the durability are good. Therefore, the thermochromic material provided by the invention has higher reversible color-changing durability, and is beneficial to long-term use of the color-changing textile.

Drawings

FIG. 1 is a sample photograph of a printed facing of size 2 of example 1 of the present invention;

FIG. 2 is a photograph of a sample of the printed facing of size 2 of example 1 of the present invention after color change;

FIG. 3 is a photograph of a sample of the printed facing of size 2 of example 1 of the present invention after a longer warm-up time has been color-shifted.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. 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.

The thermochromic material provided by the invention has higher reversible color-changing durability, can be used for obtaining the color-changing textile through printing and other processes, can be reversibly colored at a specific temperature, has improved light fastness, and can be used for a long time.

The thermochromic material is of a double-layer temperature-change microcapsule structure, namely, consists of a core material and two layers of capsule walls, wherein the core material is a thermosensitive color-change organic dye. The thermochromism organic dye is a thermochromism compound and mainly comprises a color former, a color developer and a solvent compound (also called a temperature regulator).

In a preferred embodiment of the present invention, a compounded compound of the color former crystal violet lactone and the color former is employed; the crystal violet lactone (colorless) is selected as a leuco body, and the crystal violet lactone with a lactone structure is used as an electron donor, so that electrons can be given out, and the structure is changed under the action of a color developing agent, namely an electron acceptor, so that the color is changed. The color-developing agent may be any of phenol, bisphenol a (2, 2-bis (4-hydroxyphenyl) propane), calcium chloride, stearic acid, lunar silicic acid, boric acid, and the like, and bisphenol a is preferable. And the mass ratio of the crystal violet lactone to the color developer is preferably 2-3:4-6.

In addition, the solvent compound can be one or more of dodecanol, tetradecanol, hexadecanol, octadecanol, paraffin, lauric acid glyceride, n-butyl stearate, glyceryl monostearate, glycerol monostearate, phenyl salicylate, azoxyanisole and the like.

In the invention, the core material is sequentially coated with a first capsule wall and a second capsule wall; the first capsule wall is formed by polymerization of polyvinyl alcohol and n-butyraldehyde, and the second capsule wall is formed by reaction of an ultraviolet resistant agent, polyvinyl alcohol and n-butyraldehyde. The double-layer capsule wall has good sealing performance and strength, can wrap various color-changing system components, and is easier to ensure that the content is not lost; the outer layer of the temperature-sensitive color-changing system is protected by an ultraviolet resistant agent, so that the stability of the color-changing material is improved to some extent under the illumination condition, the color-changing material is not easy to lose effectiveness, and meanwhile, the effect of generating reversible thermochromic according to temperature change is achieved.

Wherein the ultraviolet resistant agent can be one or more of titanium dioxide and ultraviolet absorbent, such as benzotriazole, triazine, salicylate and benzophenone ultraviolet absorbent.

Accordingly, the embodiment of the invention provides a preparation method of the durable thermochromic material, which comprises the following steps:

Preferably, the thermochromic organic dye in the monolayer microcapsule powder comprises: crystal violet lactone colourants and developers. The color-developing agent may be any of phenol, bisphenol a (2, 2-bis (4-hydroxyphenyl) propane), calcium chloride, stearic acid, lunar silicic acid, boric acid, and the like, and bisphenol a is preferable. And the mass ratio of the crystal violet lactone to the color developer is preferably 2-3:4-6.

The embodiment of the invention firstly prepares the single-layer microcapsule powder (abbreviated as single-layer temperature-changing microcapsule) containing the color-changing functional material, and mainly comprises the steps of preparing a thermochromic compound and single-layer microencapsulation.

According to the embodiment of the invention, 30-50 parts by mass of solvent can be heated and melted, after the solvent is completely changed into a molten state, 2-3 parts of color former crystal violet lactone and 4-6 parts of color former are sequentially added, the temperature of a reaction kettle is raised to 90 ℃, and the mixture is fully stirred and kept for 1-2 hours, and naturally cooled to room temperature, so that a dark blue solid is obtained.

The solvent for heating and melting is preferably one or more of dodecanol, tetradecanol, hexadecanol, octadecanol, paraffin, lauric acid glyceride, n-butyl stearate, glyceryl monostearate, glycerol monostearate, phenyl salicylate and azoxyanisole; the temperature of the reaction kettle can be regulated to be higher than the melting point of the corresponding solvent by 10 ℃ and the stirring speed is 400r/min. The reaction temperature for preparing the thermochromic compound can be 80-90 ℃, and the stirring speed is properly increased to 600r/min; and transferring the fully reacted color-changing compound solution after the reaction is finished, and naturally cooling to room temperature to obtain a deep blue solid for standby.

Then, preparing the deep blue solid, an emulsifier and water into core material emulsion; the emulsifier can be one or more of gum arabic, sodium dodecyl benzene sulfonate, styrene-maleic anhydride copolymer, OP-10, tween-80, span-60. Specifically, 2-3 parts by mass of emulsifier is selected, and 40-50 parts of water is added to prepare an emulsifier solution; heated and stirred until completely dissolved, cooled to room temperature. Preferably, the emulsifier solution is slowly warmed to 65 ℃ with stirring, 40-50 parts of deep blue solid is slowly added, and the mixture is emulsified to form a core emulsion. The emulsification process preferably comprises: emulsifying for 10min at 10000r/min with a high-speed shearing emulsifying machine under the water bath condition of 65 ℃ and then performing ultrasonic emulsification for 10min at 100HZ frequency to obtain core material emulsion.

The embodiment of the invention mainly adopts a prepolymer solution formed by polyvinyl alcohol and n-butyraldehyde to realize single-layer microencapsulation of the core material. The polyvinyl alcohol is white powder and is easy to dissolve in water, and specifically linear polyvinyl alcohol is selected, and the average polymerization degree is 1500-2500; the mass ratio of polyvinyl alcohol to n-butyraldehyde forming the prepolymer solution according to the invention is preferably 20-30:15-20. According to the mass parts, the embodiment of the invention preferably weighs 20-30 parts of polyvinyl alcohol, adds 20-30 parts of water, heats to 40 ℃, stirs at the rotating speed of 400r/min, heats to 95 ℃ and completely dissolves the polyvinyl alcohol at the rotating speed of 1000 r/min; and (3) slowly dripping 15-20 parts by mass of n-butyraldehyde into the mixture under the stirring of 500r/min after the temperature is reduced to 40 ℃, mixing the mixture for 1 to 1.5 hours, preferably adjusting the pH value to 4 to 6 by hydrochloric acid or acetic acid, slowly heating the mixture to 40 ℃, and preserving the temperature for 3 to 4 hours to obtain a prepolymer solution formed by polyvinyl alcohol and n-butyraldehyde.

Under the condition of room temperature, 50 parts by mass of a prepolymer solution consisting of polyvinyl alcohol and n-butyraldehyde is preferably weighed, the core material emulsion can be slowly dripped under the stirring of 400r/min, the temperature is slowly increased to 70-80 ℃, the temperature is kept constant for 3-4 hours, the temperature is slowly reduced to the room temperature, the mixture is washed by water and filtered by suction, and the single-layer microcapsule powder is obtained through separation. The single-layer microcapsule prepared by the embodiment of the invention has simple auxiliary ingredients, does not influence stability due to phase separation, is easy to separate, and is convenient for the subsequent synthesis of the second-layer capsule wall.

According to the embodiment of the invention, the prepared single-layer microcapsule is taken as a core, and the capsule wall is coated again, so that the double-layer microcapsule is prepared. According to the mass parts, the preferred embodiment of the invention mixes 20-30 parts of the single-layer microcapsule powder, 5-10 parts of the ultraviolet resistance agent, 10-20 parts of polyvinyl alcohol and 10-15 parts of n-butyraldehyde in an aqueous solvent, and the mixture is stirred to enable water to permeate into the single-layer microcapsule, and the temperature is increased for reaction, so that the durable thermochromic material with double-layer capsule walls is obtained.

Wherein, 5-10 parts of ultraviolet resistant agent and 10-20 parts of polyvinyl alcohol are dissolved in 20-30 parts of water-glycol mixed solution, the temperature is preferably raised to 40 ℃, the stirring is carried out at the rotating speed of 400r/min, the temperature is raised to 95 ℃, and the rotating speed of 1000r/min is reached until the polyvinyl alcohol is completely dissolved. In the embodiment of the invention, the temperature is preferably reduced to 30 ℃, 10-15 parts of n-butyraldehyde is slowly dripped under the stirring of 500r/min, and the polyvinyl alcohol-n-butyraldehyde solution containing the ultraviolet resistance agent is obtained; the ultraviolet resistant agent can be titanium dioxide or ultraviolet absorbent, such as benzotriazole, triazine, salicylate and benzophenone ultraviolet absorbent.

Finally, weighing 20-30 parts of the single-layer microcapsule powder with reversible thermochromic property, adding the single-layer microcapsule powder into the polyvinyl alcohol-n-butyraldehyde solution, and stirring for 1-2 hours to enable the aqueous solution to fully permeate into the microcapsules; preferably, hydrochloric acid or acetic acid is used for regulating the pH value to 4-6, the temperature can be slowly raised to 70-80 ℃, the constant temperature reaction is carried out for 3-4 hours, and then the temperature is slowly lowered to the room temperature. The embodiment of the invention cleans and pumps the cooled microcapsule solution with a large amount of distilled water, and then places the solution in a vacuum oven for drying to obtain the reversible thermochromic double-layer microcapsule powder. The specific operation of the embodiment of the invention is uniformly and fully dispersed, which is beneficial to improving the uniformity of the particle size of microcapsule particles, otherwise, the uniformity and fastness of color development are easily affected.

In the embodiment of the invention, the reversible thermochromic double-layer microcapsule powder is a temperature-sensitive color-changing material or a thermochromic material, has the particle size of micron or nanometer level, has higher reversible color-changing durability and good color rendering property, and can be applied to fabrics by a printing process mode.

The embodiment of the invention provides printing paste which comprises the durable thermochromic material. Specifically, the printing paste comprises the following components in parts by mass: 10-20 parts of durable thermochromic material, 10-20 parts of printing adhesive, 1-3 parts of penetrating agent, 0.5-1 part of thickening agent and 30-40 parts of water. Wherein the binder and thickener are independently preferably aqueous auxiliaries; the penetrating agent can be JFC, and can further comprise 2-3 parts of hydrophilic agent and other additives.

In a specific embodiment of the present invention, the printing paste is: 10 parts of the double-layer microcapsule powder, 10 parts of a water-based polyacrylate adhesive, 2.5 parts of a penetrating agent JFC, 0.5 part of a water-based thickener, 30 parts of water, and adding acetic acid to adjust the pH to 4-6; the printing paste has a viscosity of 2050 mpa.s (20 ℃).

The embodiment of the invention provides a printed fabric, which is prepared by printing fabrics with the printing paste. The embodiment of the invention is not particularly limited to the fabric, and any type of fabric can be adopted for conventional printing technology. Specifically, after printing, drying at 80-100 ℃ for 3-5min, and baking at 140-160 ℃ for 3-5 min; preferably, the printing is followed by drying at 80 ℃ for 3min and baking at 140 ℃ for 5min.

The printed fabric obtained by the embodiment of the invention has the color change phenomenon after temperature change, can recover after color change, has improved light fastness and washing fastness, and can be used for a long time.

For a further understanding of the present application, the durable thermochromic materials provided herein, methods of making the same, and applications in textiles are specifically described below in connection with examples. It is to be understood that these examples are provided for the purpose of illustrating the details of the invention and the particular process and are not intended to limit the scope of the invention, which is defined solely by the claims, but not by the way of limitation.

The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

In the following examples, linear polyvinyl alcohol was used, and the average polymerization degree was 1500 to 2500.

Example 1

1) Preparation of monolayer temperature-variable microcapsules

Preparing a color-changing compound: the temperature of the reaction kettle is regulated to be constant at 50 ℃ which is 10 ℃ higher than the melting point of the corresponding solvent tetradecanol, the stirring speed is 400r/min, and 40 parts of tetradecanol is heated and melted. After the solvent is completely changed into a molten state, sequentially adding 3 parts of color former crystal violet lactone and 6 parts of color former bisphenol A, simultaneously raising the temperature of a reaction kettle to 90 ℃, properly raising the stirring speed to 600r/min, fully stirring and preserving heat for 2 hours, transferring a color-changing compound solution obtained by fully reacting after the reaction is finished, and naturally cooling to room temperature to obtain a dark blue solid for standby.

2 parts of emulsifier Tween-80 is selected, and 40 parts of water is added to prepare an emulsifier solution; heating and stirring to dissolve completely, and cooling to room temperature. Slowly heating the emulsifier solution to 65 ℃ under stirring, slowly adding 40 parts of the color-changing compound, emulsifying with a high-speed shearing emulsifying machine at 10000r/min under the water bath condition of 65 ℃ for 10min, and then emulsifying with 100HZ frequency for 10min to form core material emulsion (chemical) liquid.

Weighing 20 parts of polyvinyl alcohol, adding 30 parts of water, heating to 40 ℃, stirring at the rotating speed of 400r/min, heating to 95 ℃ and completely dissolving the polyvinyl alcohol at the rotating speed of 1000 r/min; cooling to 40 ℃, slowly dripping 20 parts of n-butyraldehyde under 500r/min stirring, and mixing for 1.5h; adjusting the pH value to 4-6 by hydrochloric acid or acetic acid, slowly heating to 40 ℃, and preserving heat for 4 hours to obtain a prepolymer solution.

Under the condition of room temperature, 50 parts of a prepolymer solution formed by polyvinyl alcohol and n-butyraldehyde is weighed, the core material emulsion is slowly dripped under the stirring of 400r/min, the temperature is slowly increased to 80 ℃, the constant temperature reaction is carried out for 4h, the temperature is slowly reduced to the room temperature, the water is used for cleaning and the suction filtration is carried out, and the single-layer microcapsule powder is recorded as microcapsule 1.

2) Preparation of double-layered microcapsules

10 parts of benzotriazole ultraviolet absorbent Tinuvin 1130 (Basf company) and 15 parts of polyvinyl alcohol are dissolved in 25 parts of water-glycol mixed solution (solvent volume ratio is 3:2), the temperature is raised to 40 ℃, the stirring is carried out at the rotating speed of 400r/min, the temperature is raised to 95 ℃, and the rotating speed of 1000r/min is raised until the polyvinyl alcohol and the like are completely dissolved; and cooling to 30 ℃, and slowly dripping 15 parts of n-butyraldehyde under stirring at 500r/min to obtain a polyvinyl alcohol-n-butyraldehyde solution.

Weighing 30 parts of the single-layer microcapsule powder prepared in the step 1), adding the single-layer microcapsule powder into the polyvinyl alcohol-n-butyraldehyde solution, and stirring for 2 hours to enable the aqueous solution to permeate into the microcapsules; adjusting the pH value to 4-6 by hydrochloric acid or acetic acid, slowly heating to 80 ℃, reacting at constant temperature for 3.5h, and slowly cooling to room temperature.

Washing the obtained microcapsule solution with a large amount of distilled water, performing suction filtration, and then drying in a vacuum oven to obtain reversible thermochromic double-layer microcapsule powder (called as double-layer temperature-changing capsule powder for short) which is marked as microcapsule 2; the particle size was uniform and the particle size parameters were as shown in the following table.

TABLE 1 particle size of double-layered microcapsules prepared in the examples of the present invention

The testing method comprises the following steps: after the microcapsule is diluted by 1000 times by distilled water, the Nano-particle size and potential analyzer of Nano-ZS is used for testing the particle size and distribution of emulsion.

3) Printing process

And selecting 180g/gsm bleached all-cotton plain cloth as a fabric body, and then printing a printing functional layer on the outer layer of the fabric body to obtain the printed fabric.

Printing paste 1: 10 parts of the single-layer temperature-changing microcapsule powder, 10 parts of an aqueous polyacrylate adhesive, namely, marine vertical firewood UDT LIQ (high company), 2.5 parts of a penetrating agent JFC (Henschel company), 0.5 part of an aqueous thickener PTF (Henschel company) and 30 parts of water; adding acetic acid to adjust pH to about 6. The printing paste is used as a comparison group, and other processes are the same except that the color-changing functional materials are different.

Printing paste 2: 10 parts of the double-layer temperature-changing capsule powder, 10 parts of a water-based polyacrylate adhesive, 2.5 parts of a penetrating agent JFC, 0.5 part of a water-based thickener PTF and 30 parts of water; the pH was adjusted to about 6 with acetic acid, and the printing paste viscosity was 2050 mpa.s (20 ℃ C.).

The printing process comprises the following steps: 20 parts of the printing paste are used for flat screen printing and then dried for 3min at 80 ℃ and baked for 5min at 140 ℃.

Example 2

1) Preparation of monolayer temperature-variable microcapsules

Preparing a color-changing compound: the temperature of the reaction kettle is regulated to be constant at 40 ℃ which is 10 ℃ higher than the melting point of the corresponding solvent n-butyl stearate, and 50 parts of n-butyl stearate is heated and melted at the stirring speed of 400r/min. After the solvent is completely changed into a molten state, sequentially adding 2.5 parts of color former crystal violet lactone and 5.5 parts of color former phenol, simultaneously raising the temperature of a reaction kettle to 90 ℃, properly raising the stirring speed to 600r/min, fully stirring and preserving heat for 2 hours, transferring a color-changing compound solution obtained by fully reacting after the reaction is finished, and naturally cooling to room temperature to obtain a dark blue solid for standby.

2 parts of emulsifier styrene-maleic anhydride copolymer is selected and added into 40 parts of water to prepare an emulsifier solution; heating and stirring to dissolve completely, and cooling to room temperature. Slowly heating the emulsifier solution to 65 ℃ under stirring, slowly adding 40 parts of the color-changing compound, emulsifying with a high-speed shearing emulsifying machine at 10000r/min under the water bath condition of 65 ℃ for 10min, and then emulsifying with 100HZ frequency for 10min to form core material emulsion.

Weighing 20 parts of polyvinyl alcohol, adding 25 parts of water, heating to 40 ℃, stirring at the rotating speed of 400r/min, heating to 95 ℃ and completely dissolving the polyvinyl alcohol at the rotating speed of 1000 r/min; cooling to 40 ℃, slowly dripping 20 parts of n-butyraldehyde under stirring at 500r/min, and mixing for 1h; adjusting the pH value to 4-6 by hydrochloric acid or acetic acid, slowly heating to 40 ℃, and preserving heat for 4 hours to obtain a prepolymer solution.

And under the condition of room temperature, weighing 50 parts of prepolymer solution formed by polyvinyl alcohol and n-butyraldehyde, slowly dripping the core emulsion under the stirring of 400r/min, slowly heating to 80 ℃, reacting at constant temperature for 4 hours, slowly cooling to room temperature, washing with water, and carrying out suction filtration to obtain the single-layer microcapsule powder.

2) Preparation of double-layered microcapsules

4 parts of titanium dioxide, 4 parts of benzophenone ultraviolet absorbent Chimassorb 81 (Basoff company) and 15 parts of polyvinyl alcohol are dissolved in 20 parts of water-glycol mixed solution (solvent volume ratio is 3:2), the temperature is raised to 40 ℃, the stirring is carried out at the rotating speed of 400r/min, the temperature is raised to 95 ℃, and the rotating speed of 1000r/min is raised until the polyvinyl alcohol and the like are completely dissolved; and cooling to 30 ℃, and slowly dripping 15 parts of n-butyraldehyde under stirring at 500r/min to obtain a polyvinyl alcohol-n-butyraldehyde solution.

Washing the obtained microcapsule solution with a large amount of distilled water, performing suction filtration, and then drying in a vacuum oven to obtain reversible thermochromic double-layer microcapsule powder, which is marked as microcapsule 3; the particle size was uniform and the particle size parameters are shown in Table 1.

3) Printing process

Printing paste 3: 10 parts of the double-layer temperature-changing capsule powder, 10 parts of a water-based polyacrylate adhesive, 2.5 parts of a penetrating agent JFC, 0.5 part of a water-based thickener PTF and 30 parts of water; adding acetic acid to adjust pH to about 6.

The printing process comprises the following steps: after printing (the process is the same as in example 1), it is baked at 80℃for 3min and 140℃for 5min.

The performances of the printed fabric obtained by the embodiment of the invention are shown below; the situation before and after the color change of the printed fabric sample of the sizing agent 2 is seen in fig. 1-3, the blue on the fabric gradually disappears to be colorless after the temperature is raised, the temperature rise time of fig. 2 is different from that of fig. 3, and the temperature rise time of fig. 3 is longer and the color change is more obvious.

According to tables 2 and 3, the paste 1 printed fabric and the paste 2 printed fabric in the embodiment of the application are compared, and the printing K/S value of the double-layer microcapsule is slightly reduced, but the printing color uniformity is improved, and the light fastness is greatly improved. The size 3 printed fabric is compared with the size 2 printed fabric, the amount of the used color-changing dye is reduced, the grain size of the microcapsules is reduced, the depth of the printed color is reduced, but the uniformity is further improved, the fastness is approximately equivalent, and the double-layer microcapsule protection is the main reason for improving the fastness.

TABLE 2 color Change Property of printed fabrics obtained in the examples of the present invention

TABLE 3 light fastness of the printed fabrics obtained in the examples of the present invention

The fabric performance detection method comprises the following steps:

1. apparent color yield: the apparent color yield of the printed fabric was tested on a Datacolor650 color measurement colorimeter. Expressed in terms of the K/S value, the larger the K/S value, the higher the apparent color yield.

2. Uniformity: and selecting a certain point as a reference point, measuring the chromatic aberration delta E of the fabric at n different positions on the fabric by using a color measuring and matching instrument, and then carrying out average chromatic aberration calculation according to the following formula to obtain average chromatic aberration as a measurement standard of uniformity. The smaller the number, the smaller the color difference between the fabric points, the better the color uniformity;

3. thermochromic condition: using an ironing sublimation fastness meter to enable the temperature of a heating plate to be 3 ℃ higher than the color changing temperature of a sample; after the sample is heated on the heating plate for five minutes, comparing the sample with the original sample, and observing whether the surface printing of the sample changes.

4. Washing and drying procedure: washing was continued 5 times according to GB/T8629-2017: procedure 4N (type a), ECE detergent 98 (20 g, a: b: c=77:20:3), hung to air dry.

5. Light fastness test: light and sweat fastness accords with color fastness according to GB/T14576-2009 textile color fastness test.

6. Light-resistant-spot light emission method: the color change degree of the material is changed after the track type spot light LED spot light source irradiates for 72 hours at room temperature.

7. Sunlight yellowing resistance: according to the phenomenon that the fabric is easy to turn yellow under long-time irradiation of sunlight, under the condition that a solar bulb and a heating temperature control device simulate the sunlight irradiation environment, the color change level of a sample is evaluated after the sample is placed for a period of time, and particularly under a D65 light source, the color change level of the sample is evaluated by using a gray sample card for evaluation.

From the above examples, it is apparent that the durability of the thermochromic material according to the present invention is greatly improved over the conventional commercial products. In addition, the invention can coat various color-changing system components and keep stable, does not influence color development, and has good washing fastness and durability. The thermochromic material provided by the invention has higher reversible color-changing durability, and is beneficial to long-term use of the color-changing textile.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications to these embodiments can be made by those skilled in the art without departing from the technical principles of the present invention, and these modifications should also be considered as the scope of the present invention.

Claims

1. The lasting thermochromic material is provided with a microcapsule structure and is characterized in that a thermochromic organic dye is used as a core material of the microcapsule, and the core material is sequentially coated with a first capsule wall and a second capsule wall; the first capsule wall is formed by polymerization of polyvinyl alcohol and n-butyraldehyde, and the second capsule wall is formed by reaction of an ultraviolet resistance agent, polyvinyl alcohol and n-butyraldehyde; the thermochromic organic dye comprises crystal violet lactone and a color developing agent, wherein the color developing agent is any one of phenol, bisphenol A, calcium chloride, stearic acid, lunar silicic acid and boric acid.

2. The durable thermochromic material of claim 1, wherein the ultraviolet resistance agent is titanium dioxide and/or an ultraviolet absorber.

3. A method of preparing a durable thermochromic material according to any of claims 1-2, comprising the steps of:

s2, mixing the single-layer microcapsule powder, an ultraviolet resistant agent, polyvinyl alcohol and n-butyraldehyde in an aqueous solvent, stirring to enable water to permeate into the single-layer microcapsule, and heating to react to obtain a durable thermochromic material with double-layer capsule walls;

the thermosensitive color-changing organic dye comprises crystal violet lactone and a color-developing agent; the single-layer microcapsule powder is obtained according to the following steps:

mixing the crystal violet lactone and the color developing agent in a solvent in a molten state, heating, preserving heat for reaction, and cooling to obtain a dark blue solid;

4. The method according to claim 3, wherein the solvent in the preparation of the single-layer microcapsule powder is one or more of dodecanol, tetradecanol, hexadecanol, octadecanol, paraffin, lauric acid glyceride, n-butyl stearate, glycerol monostearate, phenyl salicylate, and azoxyanisole.

5. The method according to claim 3, wherein the mass ratio of the crystal violet lactone to the color developer is 2-3:4-6; the mass ratio of polyvinyl alcohol to n-butyraldehyde forming the prepolymer solution is 20-30:15-20.

6. The method according to claim 5, wherein in the step S2, 20 to 30 parts by mass of the single-layer microcapsule powder, 5 to 10 parts by mass of the ultraviolet inhibitor, 10 to 20 parts by mass of the polyvinyl alcohol and 10 to 15 parts by mass of the n-butyraldehyde are mixed in an aqueous solvent.

7. The method according to claim 6, wherein in the step S2, the reaction is performed at a temperature of 70-80 ℃ and a pH of 4-6, and the reaction time is 3-4 hours.

8. A printing paste comprising the permanent thermochromic material according to any one of claims 1 to 2.

9. A printed fabric, characterized in that the printed fabric is produced by printing a fabric with the printing paste according to claim 8.