CN109895520B - Reusable thermosensitive color developing material, preparation method thereof and thermosensitive color developing paper - Google Patents
Reusable thermosensitive color developing material, preparation method thereof and thermosensitive color developing paper Download PDFInfo
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Abstract
The invention discloses a reusable thermosensitive chromogenic material, a preparation method thereof and thermosensitive chromogenic paper, and belongs to the field of thermosensitive chromogenic materials. The invention utilizes a donor-acceptor Steinhaos adduct (DASAs) sensitive to water as a main body, adopts organic matters as a protective layer and is based on a coating process to obtain reusable heat sensitive color developing paper. The color developing paper can be quickly changed into purple when heated to 160 ℃, and can be slowly changed into white under the action of water vapor, thereby realizing the aim of recycling.
Description
Technical Field
The invention relates to the technical field of thermosensitive coloring materials, in particular to a reusable thermosensitive coloring material, a preparation method thereof and thermosensitive coloring paper.
Background
Nowadays, human beings consume a large amount of resources in life and work, and particularly in the aspect of paper, a large amount of trees are felled every year to prepare paper pulp. It is reported that China only consumes 1000 million cubic meters of wood annually for paper production, while about 13 million trees are cut annually worldwide for paper production, which has a great impact on the ecology and environment of the earth. Therefore, the problems of saving resources and seeking a sustainable development scheme are very urgent to solve. The main solution to this problem, as far as present, is to recover and recycle the pulp. However, in the process of recycling pulp to make paper, a large amount of waste water is also generated and poses environmental hazards. Thus, it is very important to invent a paper that can be repeatedly written or printed.
The heat-sensitive color developing paper is widely applied at present, and can be used for cashier tickets, faxes and automatic teller machines in restaurants or supermarkets by being combined with a thermal printer. However, the existing heat-sensitive color developing paper has lower color developing temperature and unstable color developing effect. In addition, the color development process of the prior heat-sensitive color development paper is unidirectional, and the reuse is difficult to realize.
Disclosure of Invention
The invention aims to provide a reusable thermosensitive coloring material, a preparation method thereof and thermosensitive coloring paper, and aims to solve the problems that the existing thermosensitive coloring paper is low in coloring temperature, poor in developing stability and difficult to recycle.
The technical scheme for solving the technical problems is as follows:
a reusable thermochromic material comprising: the organic protective layer is coated on the surface of the thermosensitive color development layer in a laminated manner; wherein the heat-sensitive color-developing layer comprises a cyclic donor-acceptor Steinhaos adduct hydrate.
The invention utilizes a donor-acceptor Steinhaos adduct (DASAs) sensitive to water as a main body, adopts organic matters as a protective layer and is based on a coating process to obtain reusable heat sensitive color developing paper. The color developing paper can be quickly changed into purple when heated to 160 ℃, and can be slowly changed into white under the action of water vapor, thereby realizing the aim of recycling.
The heat-sensitive color developing material of the invention relates to a color developing mechanism as follows:
DASAs can be largely classified into two states, linear (linear) and cyclic (cyclic), which can be switched with each other. DASAs can bind with water molecules and convert to colorless and structurally stable cyclic donor-acceptor Steinhause adduct hydrate (DASAs. xH)2O). Whereas the cyclic donor-acceptor stanhaus adduct hydrate loses bound water molecules after heating and rapidly converts to violet linear DASAs. In an environment with high humidity, the paper absorbs water and turns white, so that the prepared paper can realize heat sensitive development and can be reused. And the transition temperature of the hydrate of the cyclic donor-acceptor Steinhaos adduct is 160 ℃, so that the color development temperature is high, and the color development is more stable. Under the action of the organic protective layer, the thermosensitive color developing layer can be protected, and meanwhile, the stable color development of the thermosensitive color developing layer can be facilitated, and the color developing effect is ensured.
The molecular structure of the cyclic donor-acceptor stanhaus adduct is as follows:
wherein R is1And R2Are all fatty chains.
Further, in a preferred embodiment of the present invention, the heat-sensitive color developing layer further includes a stabilizer, and the mass ratio of the cyclic donor-acceptor stewart adduct hydrate to the stabilizer is 1: (1.5-15); wherein the stabilizer comprises one or more of polyethylene glycol, polypropylene glycol and polyvinyl alcohol. When the stabilizer is in a plurality of combinations, the mixing mass ratio thereof may be arbitrary, but is preferably an equal mass ratio.
The stabilizer is added in the thermosensitive color developing layer, and the stabilizer has the functions of improving the stability and uniformity of the thermosensitive color developing layer, achieving the purpose of color development and improving the color development effect.
Further, in a preferred embodiment of the present invention, the method for synthesizing the above cyclic donor-acceptor stanhaus adduct hydrate comprises: mixing and reacting an electron acceptor and furfural in water to obtain a pre-product; mixing the pre-product and a secondary amine electron donor in an organic solvent for reaction to obtain a linear donor-acceptor Steinhaos adduct; the linear donor-acceptor stevens adduct is dispersed in water and heated, and the solvent is spun dry to give the cyclic donor-acceptor stevens adduct hydrate.
Further, in a preferred embodiment of the present invention, the reaction temperature of the electron acceptor and furfural is 20 ℃ to 30 ℃, and the reaction time is 1.5h to 2.5 h; the reaction temperature of the pre-product and the secondary amine electron donor is 25-35 ℃, and the reaction time is 1.5-2.5 h; the concentration of the linear donor-acceptor Steinhaos adduct in water is 2mg/mL-5mg/mL, the heating temperature is 65-75 ℃, and the heat preservation time is 5-7 h.
The invention ensures that the reusable thermosensitive chromogenic material with excellent chromogenic effect and stable chromogenic by controlling the reaction parameters of the synthesized cyclic donor-acceptor Steinhaos adduct hydrate, and can also improve the reaction efficiency. Specifically, the whole reaction temperature is lower and is within 100 ℃, so that the method is safe, low in energy consumption, simple to operate and beneficial to large-scale production; the linear donor-acceptor Stanhaus adduct is dispersed in water in order to effect conversion of linear DASAs to cyclic DASAs. xH2The conversion of O hydrate is controlled, and the concentration of the linear donor-acceptor Steinhaos adduct in water is controlled to be 2mg/mL-5Within the range of mg/mL, the poor color development effect caused by too low concentration can be avoided, and the influence on use caused by the formation of a layer of light brown color on the final color development product caused by too high concentration can be avoided.
Further, in a preferred embodiment of the present invention, the electron acceptor includes one or both of 1, 3-dimethyl barbituric acid and derivatives thereof and mellitic acid and derivatives thereof; the secondary amine electron donor comprises one or more of dimethylamine, diethylamine and derivatives thereof, and methylaniline and derivatives thereof; the organic solvent is an aprotic solvent.
Preferably, the aprotic solvent comprises one or more of dichloromethane, tetrahydrofuran, ethyl acetate and dimethylformamide.
Further, in a preferred embodiment of the present invention, the organic protective layer is one or more of polyethylene glycol, polypropylene glycol and polyvinyl alcohol. When the organic protective layer is in various combinations, the mixing mass ratio thereof may be arbitrary, but is preferably equal to the mass ratio.
Preferably, the polyethylene glycol has a molecular weight of 10000g/mol to 50000g/mol, more preferably 20000 g/mol. Polyethylene glycol having a molecular weight within this range allows better coating stability and solubility.
The preparation method of the reusable thermosensitive color developing material comprises the steps of sequentially coating the thermosensitive color developing material on the surface of a substrate according to the sequence of the organic protective layer, the thermosensitive color developing layer and the organic protective layer.
Further, in a preferred embodiment of the present invention, the method for preparing the reusable heat-sensitive color developing material comprises the following steps:
(1) synthesizing a cyclic donor-acceptor stewart adduct hydrate;
(2) coating a layer of organic protective solution on the surface of a substrate, and drying to obtain an organic protective layer; then coating a layer of mixed solution of a stabilizer and a cyclic donor-acceptor Steinhaos adduct hydrate on the organic protective layer, and drying to obtain a thermosensitive color developing layer; coating a layer of organic protective solution on the thermosensitive color development layer to obtain a thermosensitive color development material;
wherein the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the polyethylene glycol in the mixed solution is 1: (2-15), the stabilizer is one or more of polyethylene glycol, polypropylene glycol and polyvinyl alcohol; the solvent of the organic protective solution and the mixed solution is one or more of methanol, ethanol, tetrahydrofuran and dichloromethane, and the concentration of the organic protective solution and the mixed solution is 5 wt% -15 wt% respectively.
Further, in a preferred embodiment of the present invention, the synthesis of the cyclic donor-acceptor stewart adduct hydrate in step (1) comprises: mixing an electron acceptor and furfural in water, and reacting at the reaction temperature of 20-30 ℃ for 1.5-2.5 h to obtain a pre-product; mixing the pre-product and a secondary amine electron donor in an organic solvent, and reacting at the temperature of 25-35 ℃ for 1.5-2.5 h to obtain a linear donor-acceptor Steinhaos adduct; dispersing the linear donor-acceptor Steinhaos adduct in water, heating to 65-75 ℃, preserving the temperature for 5-7 h, and spin-drying the solvent to obtain the cyclic donor-acceptor Steinhaos adduct hydrate.
A reusable heat sensitive color developing paper comprising: plain paper and the above-mentioned heat-sensitive color developing material.
When the thermosensitive color developing paper is prepared, the thermosensitive color developing material is coated on the surface of the common paper in sequence according to the sequence of the organic protective layer, the thermosensitive color developing layer and the organic protective layer, and the thermosensitive color developing paper is obtained after the paper is dried and leveled.
The invention has the following beneficial effects:
the heat-sensitive color development material has a rapid development process, can display purple color after being kept for 5s at 160 ℃, has relatively high development temperature, and ensures that the color development paper is stable and does not develop color at normal temperature. The content after development was stable and could be stored in the dry state for 7 days without fading, while the writing was clearly visible within one month. The heat-sensitive chromogenic material can be repeatedly used, is convenient to use, is simple to operate and does not pollute the environment.
Drawings
FIG. 1 is a thermal sensitive color developing paper prepared according to example 4. For comparison, only the middle portion was coated with a heat-sensitive coloring material. The state at this time in the figure is an unheated state.
FIG. 2 is a graph showing a heat-sensitive color developing paper prepared according to example 4, heated to 160 ℃ for 5 seconds.
FIG. 3 is a thermal sensitive color developing paper prepared according to example 4, heated to 160 ℃ and maintained for 5s, and then maintained in the dark for 7 days.
FIG. 4 is a thermal sensitive color developing paper prepared according to example 4, heated to 160 ℃ and maintained for 5s, and then maintained in the dark for 15 days.
Detailed Description
The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Example 1:
the reusable thermochromic material of this embodiment includes: the heat-sensitive color development layer and the organic protective layer are laminated and coated on the surface of the heat-sensitive color development layer; wherein the heat-sensitive color-developing layer comprises a cyclic donor-acceptor Steinhaos adduct hydrate.
The preparation method of the reusable heat-sensitive color development material comprises the following steps: and sequentially coating the thermosensitive color developing material on the surface of the substrate according to the sequence of the organic protective layer, the thermosensitive color developing layer and the organic protective layer.
Example 2
The reusable thermochromic material of this embodiment includes: the organic protective layer is coated on the surface of the thermosensitive color development layer in a laminated manner; the thermosensitive color-developing layer comprises a cyclic donor-acceptor Steinhaos adduct hydrate and polyethylene glycol, wherein the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the polyethylene glycol is 1: 2.
the preparation method of the reusable heat-sensitive color development material comprises the following steps:
(1) synthesizing a cyclic donor-acceptor stewart adduct hydrate;
mixing an electron acceptor and furfural in water, and reacting at the reaction temperature of 20 ℃ for 2.5 hours to obtain a pre-product; mixing the pre-product and a secondary amine electron donor in an organic solvent, and reacting for 2.5 hours at the reaction temperature of 25 ℃ to obtain a linear donor-acceptor Steinhaos adduct; and (3) dispersing the linear donor-acceptor Steinhaos adduct in water, heating to 65 ℃, preserving the temperature for 7h, and spin-drying the solvent to obtain the cyclic donor-acceptor Steinhaos adduct hydrate.
Wherein the linear donor-acceptor Steinhaos adduct is present in water at a concentration of 2 mg/mL. The electron acceptor is 1, 3-dimethyl barbituric acid; the secondary amine electron donor is dimethylamine; the organic solvent is dichloromethane.
(2) Coating a layer of organic protective solution with the concentration of 5 wt% on the surface of a substrate, and drying to obtain an organic protective layer; then coating a layer of mixed solution of 5 wt% of polyethylene glycol and cyclic donor-acceptor Steinhaos adduct hydrate on the organic protective layer, and drying to obtain a thermosensitive color developing layer; and coating a layer of organic protective solution with the concentration of 5 wt% on the thermosensitive color developing layer to obtain the thermosensitive color developing material.
Wherein the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the polyethylene glycol in the mixed solution is 1: and 2, the organic protective solution and the mixed solution respectively have methanol as a solvent and polyethylene glycol as a solute.
Example 2:
the reusable thermochromic material of this embodiment includes: the organic protective layer is coated on the surface of the thermosensitive color development layer in a laminated manner; the thermosensitive color-developing layer comprises a cyclic donor-acceptor Steinhaos adduct hydrate and polyethylene glycol, wherein the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the polyethylene glycol is 1: 15.
the preparation method of the reusable heat-sensitive color development material comprises the following steps:
(1) synthesizing a cyclic donor-acceptor stewart adduct hydrate;
mixing an electron acceptor and furfural in water, and reacting at the reaction temperature of 30 ℃ for 1.5h to obtain a pre-product; mixing the pre-product and a secondary amine electron donor in an organic solvent, and reacting for 1.5 hours at the reaction temperature of 35 ℃ to obtain a linear donor-acceptor Steinhaos adduct; and (3) dispersing the linear donor-acceptor Steinhaos adduct in water, heating to 75 ℃, preserving the temperature for 5h, and spin-drying the solvent to obtain the cyclic donor-acceptor Steinhaos adduct hydrate.
Wherein the linear donor-acceptor Steinhaos adduct is present in water at a concentration of 5 mg/mL. The electron acceptor is Meldrum's acid; the secondary amine electron donor is diethylamine; the organic solvent is tetrahydrofuran.
(2) Coating a layer of organic protective solution with the concentration of 15 wt% on the surface of a substrate, and drying to obtain an organic protective layer; then coating a layer of mixed solution of polyethylene glycol with the concentration of 15 wt% and a cyclic donor-acceptor Steinhaos adduct hydrate on the organic protective layer, and drying to obtain a thermosensitive color development layer; and coating a layer of organic protective solution with the concentration of 15 wt% on the thermosensitive color development layer to obtain the thermosensitive color development material.
Wherein the mass ratio of the donor-acceptor Steinhaos adduct to the polyethylene glycol in the mixed solution is 1: 15, the organic protective solution and the solvent of the mixed solution are respectively ethanol.
Example 3:
the reusable thermochromic material of this embodiment includes: the organic protective layer is coated on the surface of the thermosensitive color development layer in a laminated manner; the thermosensitive color development layer comprises a cyclic donor-acceptor Steinhaos adduct hydrate and polypropylene glycol, wherein the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the polypropylene glycol is 1: 8.
the preparation method of the reusable heat-sensitive color development material comprises the following steps:
(1) synthesizing a cyclic donor-acceptor stewart adduct hydrate;
mixing an electron acceptor and furfural in water, and reacting at the reaction temperature of 25 ℃ for 2 hours to obtain a pre-product; mixing the pre-product and a secondary amine electron donor in an organic solvent, and reacting for 2 hours at the reaction temperature of 30 ℃ to obtain a linear donor-acceptor Steinhaos adduct; and (3) dispersing the linear donor-acceptor Steinhaos adduct in water, heating to 70 ℃, preserving the temperature for 6h, and spin-drying the solvent to obtain the cyclic donor-acceptor Steinhaos adduct hydrate.
Wherein the linear donor-acceptor Steinhaos adduct concentration in water is 3.5 mg/mL. The electron acceptor is a mixture of 1, 3-dimethyl barbituric acid and meldrum's acid (which can be mixed in any ratio, in this example, in a mass ratio of 1: 1); the secondary amine electron donor is a mixture of dimethylamine, diethylamine and methylaniline (which can be mixed in any ratio, and the mass ratio of the secondary amine electron donor to the methylaniline is 1: 1:1 in the embodiment); the organic solvent is a mixed solvent of ethyl acetate and dimethylformamide (which can be mixed at any ratio, in this example, the mass ratio is 1: 1).
(2) Coating a layer of organic protective solution with the concentration of 10 wt% on the surface of a substrate, and drying to obtain an organic protective layer; then coating a layer of mixed solution of polypropylene glycol and cyclic donor-acceptor Steinhaos adduct hydrate with the concentration of 10 wt% on the organic protective layer, and drying to obtain a heat-sensitive color development layer; and coating a layer of organic protective solution with the concentration of 10 wt% on the thermosensitive color development layer to obtain the thermosensitive color development material.
Wherein the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the polypropylene glycol in the mixed solution is 1: the solvent of the organic protective solution and the solvent of the mixed solution are respectively a mixture of tetrahydrofuran and dichloromethane (which can be mixed in any ratio, in this example, the mass ratio is 1: 1), and the solute is polyethylene glycol.
Example 4:
the reusable thermochromic material of this embodiment includes: the organic protective layer is coated on the surface of the thermosensitive color development layer in a laminated manner; the thermosensitive color-developing layer comprises a cyclic donor-acceptor Steinhaos adduct hydrate and polyethylene glycol, wherein the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the polyethylene glycol is 1: 5.
the preparation method of the reusable heat-sensitive color development material comprises the following steps:
(1) synthesizing a cyclic donor-acceptor stewart adduct hydrate;
mixing an electron acceptor and furfural in water, and reacting at the reaction temperature of 25 ℃ for 2 hours to obtain a pre-product; mixing the pre-product and a secondary amine electron donor in an organic solvent, and reacting for 2 hours at the reaction temperature of 30 ℃ to obtain a linear donor-acceptor Steinhaos adduct; and (3) dispersing the linear donor-acceptor Steinhaos adduct in water, heating to 70 ℃, preserving the temperature for 6h, and spin-drying the solvent to obtain the cyclic donor-acceptor Steinhaos adduct hydrate.
Wherein the linear donor-acceptor Steinhaos adduct concentration in water is 3.5 mg/mL. The electron acceptor is 1, 3-dimethyl barbituric acid; the secondary amine electron donor is dimethylamine; the organic solvent is dichloromethane.
(2) Coating a layer of organic protective solution with the concentration of 10 wt% on the surface of a substrate, and drying to obtain an organic protective layer; then coating a layer of mixed solution of 10 wt% of polyethylene glycol and a cyclic donor-acceptor Steinhaos adduct hydrate on the organic protective layer, and drying to obtain a thermosensitive color developing layer; and coating a layer of organic protective solution with the concentration of 10 wt% on the thermosensitive color development layer to obtain the thermosensitive color development material.
Wherein the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the polyethylene glycol in the mixed solution is 1: and 5, the organic protective solution and the mixed solution respectively have methanol as a solvent and polyethylene glycol as a solute.
Example 5:
this example differs from example 4 in that the following parameters were adjusted:
the mass ratio of the hydrate of the cyclic donor-acceptor Steinhaos adduct to the polyethylene glycol is 1: 10.
example 6:
this example differs from example 4 in that the following parameters were adjusted:
the mass ratio of the hydrate of the cyclic donor-acceptor Steinhaos adduct to the polyethylene glycol is 1: 2.5.
example 7:
this example differs from example 4 in that the following parameters were adjusted:
in the step (1), the reaction temperature of the electron acceptor and the furfural is 15 ℃, and the reaction time is 2 h; the reaction temperature of the pre-product and the secondary amine electron donor is 20 ℃, and the reaction time is 2 h; the linear donor-acceptor Steinhaos adduct was heated in water at 60 ℃ and held for 6 h.
The reaction temperature for each of the above-mentioned processes was reduced by 10 ℃ compared to that of example 4.
Example 8:
this example differs from example 4 in that the following parameters were adjusted:
in the step (1), the reaction temperature of the electron acceptor and the furfural is 35 ℃, and the reaction time is 2 h; the reaction temperature of the pre-product and the secondary amine electron donor is 40 ℃, and the reaction time is 2 h; the linear donor-acceptor Steinhaos adduct was heated in water at 80 ℃ and held for 6 h.
The reaction temperature in each of the above-mentioned reaction processes was increased by 10 ℃ relative to that in example 4.
Example 9:
this example differs from example 4 in that the following parameters were adjusted:
in step (1), the concentration of the linear donor-acceptor Steinhaos adduct in water was 1.75 mg/mL.
Example 10:
this example differs from example 4 in that the following parameters were adjusted:
in step (1), the concentration of the linear donor-acceptor Steinhaos adduct in water was 7 mg/mL.
Example 11:
this example differs from example 4 in that the following parameters were adjusted:
in the step (2), the concentrations of the organic protective solution and the mixed solution are respectively 2 wt%.
Example 12:
this example differs from example 4 in that the following parameters were adjusted:
in the step (2), the concentrations of the organic protective solution and the mixed solution are respectively 18 wt%.
The thermosensitive color developing material prepared in the embodiment is coated on the surface of common paper in sequence according to the sequence of the organic protective layer, the thermosensitive color developing layer and the organic protective layer by adopting a layer-by-layer assembly method, and then the paper is dried and leveled.
The heat-sensitive color development paper prepared by the embodiment is tested, and the test result shows that the heat-sensitive development process of the color development paper corresponding to the embodiment is rapid, the color development paper can basically display purple within 5s at 160 ℃, and the development temperature is relatively high, so that the color development paper is stable and does not develop color at normal temperature. The content after development was stable and could be stored in the dry state for 7 days without fading, while the writing was clearly visible within one month.
To further illustrate the effect of the various parameters of the preparation process on the final color results, the test results of examples 4-12 are shown in Table 1.
TABLE 1
Note: the developing temperature refers to the temperature of the developing paper when the color is changed; the color development time refers to the time required for color development; the fastness period refers to the time for which the color can be kept from fading after the color is developed; the clear handwriting retention time refers to the time for which the handwriting can be kept clear.
As can be seen from the test results in Table 1, each example exhibited a color development at a transition temperature of 160 ℃ for 5 seconds, and it can be understood that the color development time was not affected by the adjustment of individual parameters under the same conditions of the raw material components and the preparation process, which was determined by the properties of the cyclic donor-acceptor Stanhaus adduct hydrate itself.
In examples 4, 5 and 6, the ratio of the cyclic donor-acceptor stewart adduct hydrate to the stabilizer was changed, and it can be seen from the test results that the fastness period and the clear writing retention time are prolonged with the increase of the specific gravity of the stabilizer, indicating that the addition of the stabilizer can indeed improve the color development stability of the color-developed paper. Examples 4, 7 and 8 change the reaction temperature for the synthesis of the cyclic donor-acceptor stewart adduct hydrate, and from the test results it can be seen that the temperature change has no significant effect on the final effect. This is because changes in reaction temperature do not have much effect on the formation of the final cyclic donor-acceptor stanhaus adduct hydrate.
Examples 4, 9 and 10 change the concentration of the linear donor-acceptor stewart adduct in water, and from the results of the tests it can be seen that the high level of the linear donor-acceptor stewart adduct directly affects the high yield of the final synthesized cyclic donor-acceptor stewart adduct hydrate, ultimately affecting the fast fading period and the clear writing retention time, the higher the concentration, the longer the fast fading period and the clear writing retention time, with example 10 having the highest concentration, the fast fading period and the clear writing retention time reaching 10 days and 35 days respectively, the fast fading period of example 9 being shortened to 4 days, and the color development effect being reduced.
Examples 4, 11 and 12 change the concentration of the organic protective solution and the mixed solution, and it can be seen from the test results that when the concentration of both the organic protective solution and the mixed solution is reduced to 2 wt%, the fast fading period and the clear writing retention time are directly reduced to 3 days and 18 days, which greatly affects the color development effect, and the higher the concentration of the organic protective solution or the mixed solution is, the better the color development effect is, which is attributed to the stabilizing effect of the stabilizer and the high content of the cyclic donor-acceptor Stanhauss adduct hydrate of the final product.
In conclusion, for the above-mentioned changes of the parameters, the contents of stabilizer and cyclic donor-acceptor stewart adduct hydrate have a significant effect on the coloration results and the reaction temperature has a weaker effect.
FIGS. 1 to 4 are graphs showing the effect of color development on a color-developing paper produced by using the color-developing coating layer of example 4 after it is heated and then it is left for different days. The color of the circle in fig. 2-4 is actually purple.
FIG. 1 is a thermal sensitive color developing paper prepared according to example 4. For comparison, the intermediate portion is coated with a heat-sensitive coloring material only, and the state is an unheated state in the drawing. FIG. 2 is a graph showing a heat-sensitive color developing paper prepared according to example 4, heated to 160 ℃ for 5 seconds. FIG. 3 is a thermal sensitive color developing paper prepared according to example 4, heated to 160 ℃ and maintained for 5s, and then maintained in the dark for 7 days. FIG. 4 is a thermal sensitive color developing paper prepared according to example 4, heated to 160 ℃ and maintained for 5s, and then maintained in the dark for 15 days. As shown in fig. 2 to 4, the color became lighter over time and a clear print was still visible when kept for 15 days after heating.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (6)
1. A reusable thermochromic material, comprising: the heat-sensitive color development layer and the organic protective layer are laminated and coated on the surface of the heat-sensitive color development layer; wherein the heat-sensitive color-developing layer comprises a cyclic donor-acceptor Steinhaos adduct hydrate;
the thermosensitive color-developing layer further comprises a stabilizer, and the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the stabilizer is 1: (2-15); wherein the stabilizer comprises one or more of polyethylene glycol, polypropylene glycol and polyvinyl alcohol;
the molecular structure of the cyclic donor-acceptor stanhaus adduct is as follows:
wherein R is1And R2Are all aliphatic chains;
the synthesis method of the cyclic donor-acceptor Steinhaos adduct hydrate comprises the following steps:
mixing and reacting an electron acceptor and furfural in water to obtain a pre-product; mixing the pre-product and a secondary amine electron donor in an organic solvent for reaction to obtain a linear donor-acceptor Steinhaos adduct; dispersing the linear donor-acceptor Steinhaos adduct in water, heating, and spin-drying the solvent to obtain a cyclic donor-acceptor Steinhaos adduct hydrate; the reaction temperature of the electron acceptor and the furfural is 20-30 ℃, and the reaction time is 1.5-2.5 h; the reaction temperature of the pre-product and the secondary amine electron donor is 25-35 ℃, and the reaction time is 1.5-2.5 h; the concentration of the linear donor-acceptor Steinhaos adduct in water is 2mg/mL-5mg/mL, the heating temperature is 65-75 ℃, and the heat preservation time is 5-7 h;
the electron acceptor comprises one or two of 1, 3-dimethyl barbituric acid and derivatives thereof and michelia acid and derivatives thereof; the secondary amine electron donor comprises one or more of dimethylamine, diethylamine and derivatives thereof, and methylaniline and derivatives thereof; the organic solvent is an aprotic solvent.
2. The reusable thermochromic material of claim 1, wherein the organic protective layer is one or more of polyethylene glycol, polypropylene glycol, and polyvinyl alcohol.
3. The method of producing a reusable heat-sensitive color developing material according to claim 1 or 2, wherein the heat-sensitive color developing material is coated on the surface of the substrate in the order of the organic protective layer, the heat-sensitive color developing layer and the organic protective layer.
4. The method for preparing the reusable heat-sensitive chromogenic material according to claim 3, characterized in that it comprises the following steps:
(1) synthesizing a cyclic donor-acceptor stewart adduct hydrate;
(2) coating a layer of organic protective solution on the surface of a substrate, and drying to obtain an organic protective layer; then coating a layer of mixed solution of a stabilizer and a cyclic donor-acceptor Steinhaos adduct hydrate on the organic protective layer, and drying to obtain a thermosensitive color developing layer; coating a layer of organic protective solution on the thermosensitive color development layer to obtain a thermosensitive color development material;
wherein the mass ratio of the cyclic donor-acceptor Steinhaos adduct hydrate to the stabilizer in the mixed solution is 1: (2-15), the stabilizer is one or more of polyethylene glycol, polypropylene glycol and polyvinyl alcohol; the solvent of the organic protective solution and the solvent of the mixed solution are respectively one or more of methanol, ethanol, tetrahydrofuran and dichloromethane, and the concentration of the organic protective solution and the concentration of the mixed solution are respectively 5 wt% -15 wt%.
5. The method for preparing a reusable heat-sensitive chromogenic material according to claim 4, wherein in step (1), the synthesis of the cyclic donor-acceptor stewart adduct hydrate comprises:
mixing an electron acceptor and furfural in water, and reacting at the reaction temperature of 20-30 ℃ for 1.5-2.5 h to obtain a pre-product; mixing the pre-product and a secondary amine electron donor in an organic solvent, and reacting at the temperature of 25-35 ℃ for 1.5-2.5 h to obtain a linear donor-acceptor Steinhaos adduct; and (3) dispersing the linear donor-acceptor Steinhaos adduct in water, heating to 65-75 ℃, preserving the temperature for 5-7 h, and spin-drying the solvent to obtain the cyclic donor-acceptor Steinhaos adduct hydrate.
6. Reusable heat sensitive color developing paper, comprising: plain paper and the heat-sensitive color developing material according to any one of claims 1 or 2.
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| CN112227109B (en) * | 2020-09-16 | 2021-06-22 | 电子科技大学 | Novel multi-layer DASAs rewritable printing paper and preparation method thereof |
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