Thermosensitive microcapsule dispersion liquid, and preparation method and application thereof

Abstract

The application discloses a kind of thermosensitive microcapsule dispersions and its preparation method and application, it is related to microcapsule technical field.The application provides a kind of thermosensitive microcapsule dispersion, the thermosensitive microcapsule dispersion D90≤0.75 μm, thermosensitive microcapsule dispersion D100≤1.35 μm;The thermosensitive microcapsule dispersion includes thermosensitive microcapsule, the thermosensitive microcapsule includes capsule wall and capsule core, the weight percentage of the capsule wall and capsule core is (45-66) :(34-55);The capsule wall is polyurethane-polyurea compound, and the capsule core is chromogenic dye precursor and solvent.The application innovatively generates polyurethane-polyurea compound capsule wall by twice polymerization reaction, by capsule wall material polyisocyanate and polyether polyhydric alcohol primary polymerization reaction, polyisocyanate and polyamine secondary polymerization reaction, by the effective regulation of product species and generation amount, effectively control the temperature sensitivity of thermosensitive microcapsule, color range.

Description

Technical Field

[0001] This invention relates to the field of microcapsule technology, and in particular to a thermosensitive microcapsule dispersion, its preparation method, and its application. Background Technology

[0002] Thermal recording materials primarily utilize the chemical reaction between electron-donating colorless dyes and electron-accepting compound chromogenic agents in a high-temperature molten state to form recorded images. This type of thermal recording material has significant advantages over traditional information recording materials, including simple processing, easy attainment of high color density, simple processing equipment, and low cost. It has been widely used in various industries, including the medical field, where many thermal products are currently in use. As a recording medium for medical imaging outputs such as X-rays, CT scans, and MRIs, thermal recording materials serve as a diagnostic reference medium, requiring images with high quality, clear details and distinct layers, high color density, high sensitivity, and a wide color gamut. Therefore, the requirements for such thermal recording materials are extremely high. Conventional thermal recording materials, due to their low image resolution, cannot meet these requirements.

[0003] Existing thermal microcapsules are mostly used in ordinary thermal recording materials, such as paper. They only require color density and sensitivity, not a wide color range, and can be used for text and simple image output, but cannot meet the requirements for complex and detailed medical transparent imaging. Current technologies employ multi-layer coating structures to achieve the color development requirements and image detail requirements of medical images across low, medium, and high temperature ranges. These coating structures are complex, leading to complicated production processes and low efficiency. Existing microcapsules are produced through a single interfacial polymerization reaction, and the thermal sensitivity characteristics of the capsule, such as glass transition temperature, initial color development temperature, and color range width, have not been fully optimized. When applied to thermal medical films, they result in a narrow color range and energy range, leading to insufficient image detail and poor image quality. Traditional silver halide photographic films require exposure and processing, resulting in long image output cycles and poor image quality. As a high-end thermal recording medium, ordinary thermal paper technology is limited in its use due to its narrow color development temperature range and cannot be used for image output.

[0004] Therefore, there is a wide range of applications for a thermosensitive microcapsule dispersion that can effectively control temperature sensitivity and color development temperature range. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to overcome the shortcomings of the prior art and provide a thermosensitive microcapsule dispersion that can effectively control temperature sensitivity and color development range, as well as its preparation method and application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a thermosensitive microcapsule dispersion, wherein the thermosensitive microcapsule dispersion has a D90 ≤ 0.75 μm and a D100 ≤ 1.35 μm; the thermosensitive microcapsule dispersion contains thermosensitive microcapsules, wherein the thermosensitive microcapsule comprises a capsule wall and a capsule core, and the weight percentage of the capsule wall and the capsule core is (45-66):(34-55); the capsule wall is a polyurethane-polyurea composite, and the capsule core is a chromogenic dye precursor and a solvent.

[0007] The present invention also provides a method for preparing the aforementioned thermosensitive microcapsule dispersion, comprising the following steps:

[0008] (1) Mix the color-developing dye precursor, organic solvent and polyisocyanate, and heat until dissolved to obtain oil phase mixture A;

[0009] (2) After cooking polyvinyl alcohol, a basic protective liquid is obtained. Surfactant and polyether polyol are added and mixed evenly to obtain aqueous phase mixture B.

[0010] (3) Add oil phase mixture A to aqueous phase mixture B, homogenize and emulsify to obtain oil-in-water mixture C; wherein, the polyisocyanate and polyether polyol undergo a single polymerization reaction to obtain a polyurethane capsule wall skeleton;

[0011] (4) The diluted polyamine is added to the oil-in-water mixture C, and the reaction yields the thermosensitive microcapsule dispersion; wherein, the polyisocyanate and the polyamine undergo a secondary polymerization reaction, and on the basis of the polyurethane capsule wall skeleton, a polyurea capsule wall is generated to nest and fill the polyurethane capsule wall skeleton, forming a polyurethane-polyurea composite capsule wall.

[0012] This invention innovatively employs a two-stage polymerization reaction to generate the polyurethane-polyurea composite capsule wall. Through a primary polymerization reaction of the capsule wall materials—polyisocyanate and polyether polyol—and a secondary polymerization reaction of the polyisocyanate and polyamine, the temperature sensitivity and colorimetric range of the thermosensitive microcapsules are effectively controlled by precisely regulating the types and amounts of the byproducts. This allows the thermosensitive colorimetric layer, when applied to thermosensitive medical films, to achieve a low initial colorimetric temperature, a widened colorimetric range, high colorimetric sensitivity, and a stable printing energy curve through a single colorimetric coating. Consequently, the output image exhibits clear details, distinct layers, high resolution, strong contrast, and excellent image quality.

[0013] Preferably, the molar ratio of polyether polyol in step (2) to polyisocyanate in step (1) is (0.1-1.0):1, and the molar ratio of polyamine in step (4) to polyisocyanate in step (1) is (0.1-2):1; more preferably, the molar ratio of polyether polyol in step (2) to polyisocyanate in step (1) is (0.3-0.8):1, and the molar ratio of polyamine in step (4) to polyisocyanate in step (1) is (0.3-1):1.

[0014] After extensive experimental research, the inventors of this application discovered that the amounts of polyisocyanate and polyether polyol, and polyisocyanate and polyamine used in the primary polymerization reaction of polyisocyanate and polyether polyol, and the secondary polymerization reaction of polyisocyanate and polyamine in the capsule wall material affect the compactness of the final polyurethane-polyurea composite capsule wall, thereby further affecting the temperature sensitivity and color development range performance of the thermosensitive microcapsules. When the molar ratio of polyisocyanate and polyether polyol, and polyisocyanate and polyamine is within the above range, the temperature sensitivity and color development temperature range performance of the thermosensitive microcapsules are better.

[0015] Preferably, in step (1), the mass ratio of the chromogenic dye precursor, organic solvent, and polyisocyanate is chromogenic dye precursor: organic solvent: polyisocyanate = (3.5-5.7): (14-25): (3.5-6.6), and in step (2), the mass ratio of polyvinyl alcohol, surfactant, and polyether polyol is vinyl alcohol: surfactant: polyether polyol = (7.5-11): (2.5-4.5): (2.5-25).

[0016] Preferably, in step (1), the temperature is heated to 60-85°C; in step (2), the temperature is boiled to 60-95°C; in step (3), the homogenization temperature is 50-80°C; and in step (4), the reaction temperature is 50-70°C. More preferably, in step (1), the temperature is heated to 70-80°C; in step (2), the temperature is boiled to 70-80°C; in step (3), the homogenization temperature is 60-75°C; and in step (4), the reaction temperature is 50-60°C.

[0017] Preferably, the polyisocyanate is hexamethylene diisocyanate, hexamethylene diisocyanate dimer, hexamethylene diisocyanate trimer, isophorone diisocyanate, isophorone diisocyanate dimer, isophorone diisocyanate trimer, toluene diisocyanate, hydrogenated toluene diisocyanate, toluene diisocyanate dimer, toluene diisocyanate trimer, phenyl dimethyl diisocyanate, phenyl dimethyl diisocyanate-trimethylolpropane, phenyl dimethyl diisocyanate bisphenol A; preferably, the polyisocyanate is a mixture of phenyl dimethyl diisocyanate-trimethylolpropane and isophorone diisocyanate.

[0018] Preferably, the method for preparing the thermosensitive microcapsule dispersion includes at least one of the following (a)-(f):

[0019] (a) The polyether polyol has a functionality of 2-3 and a molecular weight of 400-1000;

[0020] (b) The polyamine is at least one of diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine;

[0021] (c) The degree of polymerization of the polyvinyl alcohol is 1000-3000 and the degree of alcoholysis is ≤90;

[0022] (d) The surfactant is at least one of Tween 60, Tween 80, sodium dodecyl sulfate, calcium dodecyl sulfate, and dodecylphenol polyoxyethylene ether;

[0023] (e) The organic solvent is at least one of ethyl acetate and dimethylbiphenyl;

[0024] (f) The chromogenic dye precursor is at least one of 2-phenylamino-3-methyl-6-dibutylaminofluorane, 3-(N-ethyl-isopentanamino)-6-methyl-7-anilinofluorane, 2-(2-4-dimethylamino)-3-methyl-6-diethylaminofluorane, 3,3-bis(4-diethylamino-2-ethoxyphenyl)-4-azaphthalide, 3-diethylamino-6,8-dimethylfluorane, 9(9H)oxanthracene-2-carboxylic acid-6-(diethylamino)-3-oxo-ethyl ester, and N,N-dimethyl-4-(2-(2-(octyloxy)phenyl)-6-phenylpyridin-4-yl)aniline.

[0025] After extensive experimental research, the inventors of this application discovered that the selection of components such as polyether polyol, polyamine, and polyvinyl alcohol all affect the temperature sensitivity and color temperature range of the final thermosensitive microcapsules. The inventors found that polyether polyols with a functionality between 2 and 3 and a molecular weight between 400 and 1000 exhibit better aqueous compatibility, are easily soluble in water, have moderate viscosity, and better control the reaction rate and mixture viscosity during the primary polymerization reaction, avoiding instability or rapid coagulation and slag formation problems in the polyurethane capsule wall skeleton. Polyether polyols with excessively high molecular weights are insoluble in water, which is detrimental to the stability of the aqueous dispersion in the oil-in-water system, and excessively high viscosity is also detrimental to dispersion and system uniformity. Adding the polyether end of the polyether polyol increases the soft segment of the polyurethane, thereby effectively lowering the glass transition temperature of the capsule shell. For the secondary polymerization reaction, using a small molecule polyamine, and the polyurea obtained from the secondary polymerization of isocyanate and amine groups, can increase the glass transition temperature of the wall material. By adjusting the ratio of polyurethane and polyurea wall materials, microcapsules with different color ranges can be obtained. The polyvinyl alcohol with a degree of polymerization of 1000-3000 selected in this invention is more advantageous for controlling the mixing viscosity. Therefore, by using the polyether polyol, polyamine, and polyvinyl alcohol specifically selected in this invention, thermosensitive microcapsules with better temperature sensitivity and color development temperature range can be obtained.

[0026] Furthermore, this invention provides the application of the thermosensitive microcapsule dispersion prepared by the aforementioned method in a thermosensitive colorimetric layer.

[0027] Furthermore, the present invention provides a thermosensitive colorimetric layer comprising the following components in parts by weight: 30-50 parts of colorimetric agent, 20-40 parts of thermosensitive microcapsule dispersion prepared by the method described above, 10-30 parts of adhesive, and 0.5-3 parts of wetting agent.

[0028] Preferably, the thermal color-developing layer provided by the present invention has an initial color-developing temperature as low as 80°C, a wide color-developing range of up to 50°C, and a color-developing range of 80°C-130°C. This wide color-developing temperature range is beneficial for the representation of image details in different temperature and density ranges during thermal film printing, thereby improving image resolution and ensuring high image quality.

[0029] Preferably, the adhesive of the thermosensitive color developing layer is at least one of polyvinyl alcohol, modified polyvinyl alcohol, acrylic latex, styrene-butadiene latex, aliphatic polyurethane emulsion, and polyester resin, and the wetting agent of the thermosensitive color developing layer is at least one of polyether modified organosilicon, ethylene oxide modified organosilicon, sulfonate, and alkynyl alcohol.

[0030] In addition, the present invention provides the application of the aforementioned thermal color developing layer in thermal medical films.

[0031] This invention provides a thermosensitive medical film, comprising a supporting substrate, a thermosensitive color developing layer, and a surface protective layer. The supporting substrate is a transparent polyester film material with good stiffness and thermal stability, which will not deform or stretch when heated. It can be various polyester film materials such as PET / BOPET / PVC / PP, preferably 100-200μm transparent polyethylene terephthalate (PET). The surface protective layer comprises the following components in parts by weight: 50-65 parts polyvinyl alcohol, 10-20 parts silica sol, 0.5-5 parts silicone emulsion, 1-2 parts paraffin emulsion, 3-6 parts oxidized polyethylene wax emulsion, 2-5 parts zinc stearate emulsion, 3-7 parts boric acid, and 1-2 parts wetting and leveling agent.

[0032] The surface protective layer described in this invention can provide the thermal color developing layer with protection against dirt, moisture, and dampness, and provide the printer with a good and smooth printing effect when printing images.

[0033] Compared to existing technologies, the advantages of this invention are as follows: This invention innovatively employs a two-stage polymerization reaction to generate the polyurethane-polyurea composite capsule wall. Through a primary polymerization reaction of the capsule wall materials—polyisocyanate and polyether polyol—and a secondary polymerization reaction of the polyisocyanate and polyamine, and by effectively controlling the types and amounts of the products, the temperature sensitivity and colorimetric range performance of the thermosensitive microcapsules can be effectively controlled. This allows the thermosensitive colorimetric layer, when applied in thermosensitive medical films, to achieve a low initial colorimetric temperature, a widened colorimetric range, good colorimetric sensitivity, and a stable printing energy curve through a single colorimetric coating. Consequently, the output image exhibits clear details, distinct layers, high resolution, strong contrast, and excellent image quality. Attached Figure Description

[0034] Figure 1 The image shows an electron microscope image of the thermosensitive microcapsules prepared in Example 1. Detailed Implementation

[0035] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0036] Particle size was measured using a MASTERSIZER 2000 laser particle size analyzer. The density of the recorded material was measured using an X-RITE 341C analyzer. Image resolution was evaluated using an HQ-760DY or HQ-460DY medical thermal imaging printer. Thermal sensing temperature was measured using a Guanhao A-1 static colorimeter.

[0037] Examples and Comparative Examples

[0038] This invention provides a method for preparing a thermosensitive microcapsule dispersion, comprising the following steps:

[0039] (1) Mix the color-developing dye precursor, organic solvent and polyisocyanate, and heat until dissolved to obtain oil phase mixture A;

[0040] (2) After cooking polyvinyl alcohol, a basic protective liquid is obtained. Surfactant and polyether polyol are added and mixed evenly to obtain aqueous phase mixture B.

[0041] (3) Add oil phase mixture A to aqueous phase mixture B, homogenize and emulsify to obtain oil-in-water mixture C; wherein, the polyisocyanate and polyether polyol undergo a single polymerization reaction to obtain a polyurethane capsule wall skeleton;

[0042] (4) The diluted polyamine is added to the oil-in-water mixture C, and the reaction yields the thermosensitive microcapsule dispersion; wherein, the polyisocyanate and the polyamine undergo a secondary polymerization reaction, and on the basis of the polyurethane capsule wall skeleton, a polyurea capsule wall is generated to nest and fill the polyurethane capsule wall skeleton, forming a polyurethane-polyurea composite capsule wall.

[0043] The molar ratio of polyether polyol in step (2) to polyisocyanate in step (1) is (0.1-1):1, and the molar ratio of polyamine in step (4) to polyisocyanate in step (1) is (0.1-2):1.

[0044] In step (1), the mass ratio of chromogenic dye precursor, organic solvent, and polyisocyanate is chromogenic dye precursor: organic solvent: polyisocyanate = (3.5-5.7): (14-25): (3.5-6.6). In step (2), the mass ratio of polyvinyl alcohol, surfactant, and polyether polyol is vinyl alcohol: surfactant: polyether polyol = (7.5-11): (2.5-4.5): (2.5-25).

[0045] In step (1), the temperature is heated to 60-85℃; in step (2), the temperature is cooked to 60-95℃; in step (3), the homogenization temperature is 50-80℃; and in step (4), the reaction temperature is 50-70℃.

[0046] Preferably, the polyisocyanate is hexamethylene diisocyanate, hexamethylene diisocyanate dimer, hexamethylene diisocyanate trimer, isophorone diisocyanate, isophorone diisocyanate dimer, isophorone diisocyanate trimer, toluene diisocyanate, hydrogenated toluene diisocyanate, toluene diisocyanate dimer, toluene diisocyanate trimer, phenyl dimethyl diisocyanate, phenyl dimethyl diisocyanate-trimethylolpropane, phenyl dimethyl diisocyanate bisphenol A; preferably, the polyisocyanate is a mixture of phenyl dimethyl diisocyanate-trimethylolpropane and isophorone diisocyanate.

[0047] Preferably, the method for preparing the thermosensitive microcapsule dispersion comprises at least one of the following (a)-(f):

[0048] (a) The polyether polyol has a functionality of 2-3 and a molecular weight of 400-1000;

[0049] (b) The polyamine is at least one of diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine;

[0050] (c) The degree of polymerization of the polyvinyl alcohol is 1000-3000 and the degree of alcoholysis is ≤90;

[0051] (d) The surfactant is at least one of Tween 60, Tween 80, sodium dodecyl sulfate, calcium dodecyl sulfate, and dodecylphenol polyoxyethylene ether;

[0052] (e) The organic solvent is at least one of ethyl acetate and dimethylbiphenyl;

[0053] (f) The chromogenic dye precursor is at least one of 2-phenylamino-3-methyl-6-dibutylaminofluorane, 3-(N-ethyl-isopentanamino)-6-methyl-7-anilinofluorane, 2-(2-4-dimethylamino)-3-methyl-6-diethylaminofluorane, 3,3-bis(4-diethylamino-2-ethoxyphenyl)-4-azaphthalide, 3-diethylamino-6,8-dimethylfluorane, 9(9H)oxanthracene-2-carboxylic acid-6-(diethylamino)-3-oxo-ethyl ester, and N,N-dimethyl-4-(2-(2-(octyloxy)phenyl)-6-phenylpyridin-4-yl)aniline.

[0054] The raw materials selected for the embodiments and comparative examples of this invention are as follows. Unless otherwise specified, all raw materials are commercially available conventional raw materials in the art and can be purchased through conventional channels:

[0055] The precursors for the chromophore dyes are: ODB-2 (2-phenylamino-3-methyl-6-dibutylaminofluorane), RED7 (9(9H)oxanthracene-2-carboxylic acid-6-(diethylamino)-3-oxo-ethyl ester), D5 (3-diethylamino-6,8-dimethylfluorane), GN1 (3,3-di(4-diethylamino-2-ethoxyphenyl)-4-azaphthalide), and CK37 (N,N-dimethyl-4-(2-(2-(octyloxy)phenyl)-6-phenylpyridin-4-yl)aniline), all of which are conventional commercially available products.

[0056] Organic solvents: ethyl acetate and dimethylbiphenyl, both of which are commercially available products.

[0057] Surfactant: Dodecylphenol polyoxyethylene ether, brand name OP-10, is a commercially available product.

[0058] Polyisocyanate A: a mixture of isophorone diisocyanate IPDI and phenyl diisocyanate-trimethylolpropane D-110N, wherein the ratio of isophorone diisocyanate to phenyl diisocyanate-trimethylolpropane is 7:4; wherein isophorone diisocyanate IPDI was purchased from Wanhua Chemical and phenyl diisocyanate-trimethylolpropane D-110N was purchased from Mitsui Chemicals, Japan.

[0059] Polyisocyanate B: a mixture of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate trimer (HT-600). The ratio of isophorone diisocyanate to hexamethylene diisocyanate trimer is 7:2; both isophorone diisocyanate (IPDI) and hexamethylene diisocyanate trimer (HT-600) were purchased from Wanhua Chemical.

[0060] Polyisocyanate C: Isophorone diisocyanate (IPDI).

[0061] Polyamines: Diethylenetriamine and Triethylenetetramine are both commercially available products.

[0062] Polyvinyl alcohol A: Degree of polymerization 1700, degree of alcoholysis ≤90, manufacturer: Sichuan Weihua Chemical, PVA1788.

[0063] Polyvinyl alcohol B: Degree of polymerization 2500, degree of alcoholysis 88, manufacturer: Sichuan Weihua Chemical, grade 2588.

[0064] Polyether polyol A: Functionality 3, molecular weight 500, manufacturer: Wanhua Chemical, grade: R2305.

[0065] Polyether polyol B: Functionality 4, molecular weight 1500, manufactured by Tianjin Petrochemical, grade 480H.

[0066] Example 1: Preparation of thermosensitive microcapsule dispersion A.

[0067] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0068] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0069] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 14.7g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.3:1), stir evenly to obtain an aqueous phase mixture.

[0070] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:7.35.

[0071] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0072] Step 4: Add 40g of deionized water and 8.1g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain thermosensitive microcapsule dispersion A.

[0073] in, Figure 1 The image shows an electron microscope (EM) image of the thermosensitive microcapsules prepared in Example 1. The dispersion of the thermosensitive microcapsules prepared in Example 1 was taken and allowed to air dry naturally. The dried microcapsules were then slightly crushed into fine particles or powder using a mortar and pestle for scanning electron microscopy (SEM) observation. The EEM image shows that the thermosensitive microcapsules prepared in Example 1 are spherical particles with intact capsule walls, regular shapes, and a relatively concentrated and uniform particle size distribution.

[0074] Example 2: Preparation of thermosensitive microcapsule dispersion B

[0075] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0076] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0077] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 24.5g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.5:1), stir evenly to obtain an aqueous phase mixture.

[0078] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:12.25.

[0079] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0080] Step 4: Add 40g of deionized water and 5.1g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.5:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain thermosensitive microcapsule dispersion B.

[0081] Note: In the preparation of the aqueous phase mixture in step 2, the amount of polyether polyol R2305 added is 24.5g (the molar ratio of polyether polyol R2305 to isocyanate is 0.5:1), and in step 4, the amount of diethylenetriamine added is 5.1g (the molar ratio of diethylenetriamine to isocyanate is 0.5:1). The other implementation steps are the same as the preparation steps of the thermosensitive microcapsule dispersion A, to obtain thermosensitive microcapsule dispersion B.

[0082] Example 3: Preparation of thermosensitive microcapsule dispersion C

[0083] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0084] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0085] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 39.2g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.8:1), stir evenly to obtain an aqueous phase mixture.

[0086] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:19.6.

[0087] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0088] Step 4: Add 40g of deionized water and 3.0g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.3:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain thermosensitive microcapsule dispersion C.

[0089] Note: In the preparation of the aqueous phase mixture in step 2, the amount of polyether polyol R2305 added is 39.2g (the molar ratio of polyether polyol R2305 to isocyanate is 0.8:1), and in step 4, the amount of diethylenetriamine added is 3.0g (the molar ratio of diethylenetriamine to isocyanate is 0.3:1). The other implementation steps are the same as the preparation steps of the thermosensitive microcapsule dispersion A, to obtain thermosensitive microcapsule dispersion C.

[0090] Example 4: Preparation of thermosensitive microcapsule dispersion D

[0091] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0092] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0093] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 39.2g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.8:1), stir evenly to obtain an aqueous phase mixture.

[0094] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:19.6.

[0095] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0096] Step 4: Add 40g of deionized water and 5.1g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.5:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain thermosensitive microcapsule dispersion D.

[0097] Note: In the preparation of the aqueous phase mixture in step 2, the amount of polyether polyol R2305 added is 39.2g (the molar ratio of polyether polyol R2305 to isocyanate is 0.8:1), and in step 4, the amount of diethylenetriamine added is 5.1g (the molar ratio of diethylenetriamine to isocyanate is 0.5:1). The other implementation steps are the same as the preparation steps of the thermosensitive microcapsule dispersion A, to obtain thermosensitive microcapsule dispersion D.

[0098] Example 5: Preparation of thermosensitive microcapsule dispersion E

[0099] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0100] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0101] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 39.2g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.8:1), stir evenly to obtain an aqueous phase mixture.

[0102] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:19.6.

[0103] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0104] Step 4: Add 40g of deionized water and 20.2g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 2.0:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain thermosensitive microcapsule dispersion E.

[0105] Note: In the preparation of the aqueous phase mixture in step 2, the amount of polyether polyol R2305 added is 39.2g (the molar ratio of polyether polyol R2305 to isocyanate is 0.8:1), and in step 4, the amount of diethylenetriamine added is 20.2g (the molar ratio of diethylenetriamine to isocyanate is 2.0:1). The other implementation steps are the same as the preparation steps of the thermosensitive microcapsule dispersion A, to obtain thermosensitive microcapsule dispersion E.

[0106] Example 6: Preparation of thermosensitive microcapsule dispersion F

[0107] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0108] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0109] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 49.0g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 1.0:1), stir evenly to obtain an aqueous phase mixture.

[0110] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:24.5.

[0111] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0112] Step 4: Add 40g of deionized water and 15.2g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 1.5:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain the thermosensitive microcapsule dispersion F.

[0113] Note: In the preparation of the aqueous phase mixture in step 2, the amount of polyether polyol R2305 added is 49.0g (the molar ratio of polyether polyol R2305 to isocyanate is 1.0:1), and in step 4, the amount of diethylenetriamine added is 15.2g (the molar ratio of diethylenetriamine to isocyanate is 1.5:1). The other implementation steps are the same as the preparation steps of the thermosensitive microcapsule dispersion A, to obtain thermosensitive microcapsule dispersion F.

[0114] Example 7: Preparation of thermosensitive microcapsule dispersion G

[0115] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0116] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0117] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA2588) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 14.7g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.3:1), stir evenly to obtain an aqueous phase mixture.

[0118] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:7.35.

[0119] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0120] Step 4: Add 40g of deionized water and 8.1g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain thermosensitive microcapsule dispersion G.

[0121] Note: The only difference between Example 7 and Example 1 is that the polyvinyl alcohol used is PVA2588. The other components, weight parts, molar ratios, etc. are exactly the same, and the preparation method is exactly the same, resulting in a thermosensitive microcapsule dispersion G.

[0122] Example 8: Preparation of thermosensitive microcapsule dispersion H

[0123] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 42g of isophorone diisocyanate and 24g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0124] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:6.6.

[0125] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 44.1g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.3:1), stir evenly to obtain an aqueous phase mixture.

[0126] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:22.05.

[0127] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0128] Step 4: Add 40g of deionized water and 12.1g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain the thermosensitive microcapsule dispersion H.

[0129] Note: The only difference between Example 8 and Example 1 is the mass ratio of the chromogenic dye precursor, organic solvent, and polyisocyanate, as well as the mass ratio of polyvinyl alcohol, surfactant, and polyether polyol. The other components, weight parts, molar ratios, etc. are exactly the same, and the preparation method is exactly the same, resulting in a thermosensitive microcapsule dispersion H.

[0130] Example 9: Preparation of Thermosensitive Microcapsule Dispersion I

[0131] Step 1: Add 32.4g of ODB-2, 5.6g of RED7, 4.3g of GN1, 4.5g of D5, 0.9g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 22.4g of isophorone diisocyanate and 12.8g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0132] Color-developing dye precursor: organic solvent: polyisocyanate = 4.77:17:3.52.

[0133] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 11.8g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.3:1), stir evenly to obtain an aqueous phase mixture.

[0134] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:5.9.

[0135] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0136] Step 4: Add 40g of deionized water and 6.5g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain thermosensitive microcapsule dispersion I.

[0137] Note: The only difference between Example 9 and Example 1 is the mass ratio of the chromogenic dye precursor, organic solvent, and polyisocyanate, as well as the mass ratio of polyvinyl alcohol, surfactant, and polyether polyol. The other components, weight parts, molar ratios, etc. are exactly the same, and the preparation method is exactly the same, resulting in thermosensitive microcapsule dispersion I.

[0138] Example 10: Preparation of thermosensitive microcapsule dispersion J.

[0139] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 8g of hexamethylene diisocyanate trimer, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0140] Color-developing dye precursor: organic solvent: polyisocyanate = 5.3:17:3.6.

[0141] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 14.7g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.3:1), stir evenly to obtain an aqueous phase mixture.

[0142] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:7.35.

[0143] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0144] Step 4: Add 40g of deionized water and 8.6g of triethylenetetramine to the oil-in-water dispersion (the molar ratio of triethylenetetramine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain the thermosensitive microcapsule dispersion J.

[0145] Note: Compared with Example 1, Example 10 differs in the choice of isocyanate in step 1. In this application, 28g of isophorone diisocyanate and 8g of dihexamethylene diisocyanate trimer are added; in step 4, 8.6g of triethylenetetramine is selected as the polyamine. The remaining components, weight parts, molar ratios, etc. are exactly the same, and the preparation method is exactly the same, resulting in thermosensitive microcapsule dispersion J.

[0146] Example 11: Preparation of thermosensitive microcapsule dispersion K

[0147] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 44g of isophorone diisocyanate, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0148] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0149] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 19.6g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.3:1), stir evenly to obtain an aqueous phase mixture.

[0150] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:9.8.

[0151] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0152] Step 4: Add 40g of deionized water and 10.8g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain the thermosensitive microcapsule dispersion K.

[0153] Note: Compared with Example 1, Example 11 differs in the choice of isocyanate in step 1. In this application, 44g of isophorone diisocyanate was added, while the remaining components, weight parts, molar ratios, etc., are exactly the same, and the preparation method is completely identical, resulting in thermosensitive microcapsule dispersion K.

[0154] Comparative Example 1: Preparation of thermosensitive microcapsule dispersion L.

[0155] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0156] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0157] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, stir evenly to obtain an aqueous mixture.

[0158] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:0.

[0159] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0160] Step 4: Add 40g of deionized water and 8.1g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain the thermosensitive microcapsule dispersion L.

[0161] Note: In the preparation of the aqueous phase mixture in step 2, polyether polyol R2305 is not added for a single polymerization reaction, and the polymerization reaction does not need to be carried out for 2 hours. The other implementation steps are the same as the preparation steps of the thermosensitive microcapsule dispersion A, and the thermosensitive microcapsule dispersion L is obtained.

[0162] Comparative Example 2: Preparation of thermosensitive microcapsule dispersion M.

[0163] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0164] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0165] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 14.7g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.3:1), stir evenly to obtain an aqueous phase mixture.

[0166] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:7.35.

[0167] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0168] Step 4: Add 40g of deionized water to the oil-in-water dispersion to obtain the thermosensitive microcapsule dispersion M.

[0169] Note: In step 4, diethylenetriamine is not added for secondary polymerization, and the polymerization reaction does not need to be carried out for 4 hours. The other implementation steps are the same as the preparation steps of thermosensitive microcapsule dispersion A, and thermosensitive microcapsule dispersion M is obtained.

[0170] Comparative Example 3: Preparation of thermosensitive microcapsule dispersion N.

[0171] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0172] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0173] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10 and stir evenly to obtain an aqueous mixture.

[0174] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:0.

[0175] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0176] Step 4: Add 40g of deionized water and 25.5g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 2.5:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain thermosensitive microcapsule dispersion N.

[0177] Note: In the preparation of the aqueous phase mixture in step 2, no polyether polyol R2305 is added for a single polymerization reaction, and the polymerization reaction does not need to be carried out for 2 hours. In step 4, the amount of diethylenetriamine added is 25.5g (the molar ratio of diethylenetriamine to isocyanate is 2.5:1). The other implementation steps are the same as the preparation steps of the thermosensitive microcapsule dispersion A, to obtain thermosensitive microcapsule dispersion N.

[0178] Comparative Example 4: Preparation of thermosensitive microcapsule dispersion O.

[0179] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0180] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0181] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 73.5g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 1.5:1), stir evenly to obtain an aqueous phase mixture.

[0182] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:36.75.

[0183] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0184] Step 4: Add 40g of deionized water to the oil-in-water dispersion to obtain thermosensitive microcapsule dispersion O.

[0185] Note: In the preparation of the aqueous phase mixture in step 2, the amount of polyether polyol R2305 added is 73.5g (the molar ratio of polyether polyol R2305 to isocyanate is 1.5:1). In step 4, diethylenetriamine is not added for secondary polymerization reaction, and the polymerization reaction does not need to be carried out for 4 hours. The other implementation steps are the same as the preparation steps of thermosensitive microcapsule dispersion A, and thermosensitive microcapsule dispersion O is obtained.

[0186] Comparative Example 5: Preparation of thermosensitive microcapsule dispersion P.

[0187] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0188] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0189] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 14.7g of polyether polyol 480H (the molar ratio of polyether polyol 480H to isocyanate is 0.3:1), stir evenly to obtain an aqueous phase mixture.

[0190] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:16.55.

[0191] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0192] Step 4: Add 40g of deionized water and 8.1g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain the thermosensitive microcapsule dispersion P.

[0193] Note: In the preparation of the aqueous phase mixture in step 2, the polyether polyol is 480H, and the amount added is 33.1g (the molar ratio of polyether polyol 480H to isocyanate is 0.3:1). The other implementation steps are the same as the preparation steps of the thermosensitive microcapsule dispersion A, and the thermosensitive microcapsule dispersion P is obtained.

[0194] Comparative Example 6: Preparation of thermosensitive microcapsule dispersion Q.

[0195] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 28g of isophorone diisocyanate and 16g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0196] Color dye precursor: organic solvent: polyisocyanate = 5.3:17:4.4.

[0197] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 73.5g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 1.5:1), stir evenly to obtain an aqueous phase mixture.

[0198] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:36.75.

[0199] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0200] Step 4: Add 40g of deionized water and 8.1g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain the thermosensitive microcapsule dispersion Q.

[0201] Note: In the preparation of the aqueous phase mixture in step 2, the amount of polyether polyol R2305 added is 73.5g (the molar ratio of polyether polyol R2305 to isocyanate is 1.5:1). The other implementation steps are the same as the preparation steps of the thermosensitive microcapsule dispersion A, to obtain thermosensitive microcapsule dispersion Q.

[0202] Comparative Example 7: Preparation of thermosensitive microcapsule dispersion R.

[0203] Step 1: Add 36g of ODB-2, 6.2g of RED7, 4.8g of GN1, 5.0g of D5, 1.0g of CK37, 10g of dimethylbiphenyl, and 160g of ethyl acetate to a 500ml round-bottom flask. Then add 19.6g of isophorone diisocyanate and 11.2g of phenyl dimethyl diisocyanate-trimethylolpropane, stir, and heat to above 70°C until the dye is completely dissolved to obtain an oil phase mixture.

[0204] Color-developing dye precursor: organic solvent: polyisocyanate = 5.3:17:3.08.

[0205] Step 2: Add 300g of water and 18g of polyvinyl alcohol (PVA1788) powder to the reactor, stir, heat and cook to 95℃ until all PVA is dissolved, quickly cool to 70℃, add 7g of surfactant OP-10, and add 10.3g of polyether polyol R2305 (the molar ratio of polyether polyol R2305 to isocyanate is 0.3:1), stir evenly to obtain an aqueous phase mixture.

[0206] Polyvinyl alcohol: surfactant: polyether polyol = 9:3.5:5.15.

[0207] Step 3: Slowly add the oil phase mixture obtained above to the aqueous phase solution, and disperse it at a speed of 2500 r / min for 20 min using high-speed shear stirring to obtain an oil-in-water dispersion. Control the temperature of the oil-in-water dispersion to 65℃, maintain the temperature, and continue high-speed stirring to carry out a single polymerization reaction for 2 h.

[0208] Step 4: Add 40g of deionized water and 5.7g of diethylenetriamine to the oil-in-water dispersion (the molar ratio of diethylenetriamine to isocyanate is 0.8:1), control the temperature to 55℃, and carry out a secondary polymerization reaction at a stirring speed of 2000r / min for 4h to obtain the thermosensitive microcapsule dispersion R.

[0209] Note: The only difference between Comparative Example 7 and Example 1 is the mass ratio of the chromogenic dye precursor, organic solvent, and polyisocyanate, as well as the mass ratio of polyvinyl alcohol, surfactant, and polyether polyol. All other components, parts by weight, and molar ratios are exactly the same, and the preparation methods are identical.

[0210] In step 1, during the preparation of the oil phase mixture, 19.6 g of isophorone diisocyanate and 11.2 g of phenyl dimethyl diisocyanate-trimethylolpropane were added; in step 2, during the preparation of the aqueous phase mixture, 10.3 g of polyether polyol R2305 was added (the molar ratio of polyether polyol R2305 to isocyanate was 0.3:1); in step 4, 5.7 g of diethylenetriamine was added (the molar ratio of diethylenetriamine to isocyanate was 0.8:1), and the other implementation steps were the same as those for the preparation of thermosensitive microcapsule dispersion A, to obtain thermosensitive microcapsule dispersion R.

[0211] (II) Preparation of colorimetric reagent dispersion

[0212] Mix 120g of bisphenol A, 30g of ground PVA, and 430g of deionized water, stir well, and then grind and disperse the mixture on a grinder for 6 hours to obtain a colorimetric reagent dispersion with an average particle size of 0.35μm.

[0213] (III) Preparation of the thermal colorimetric layer

[0214] The obtained thermosensitive microcapsule dispersion and colorimetric agent dispersion were mixed at a ratio of 1:1.4. An adhesive and a wetting agent were then added in the following amounts: 35 parts microcapsule dispersion, 43 parts colorimetric agent dispersion, 20 parts adhesive, and 2 parts wetting agent. The mixture was diluted with deionized water and stirred until homogeneous, resulting in a single-layer thermosensitive colorimetric coating solution with a solid content of 20%. The adhesive used in this invention is styrene-butadiene latex adhesive, and the wetting agent is an alkyl sulfonate wetting agent, but it is not limited to these two.

[0215] The only difference between the examples and comparative examples is the microcapsule dispersion. Therefore, the only difference between the thermosensitive colorimetric layers is the microcapsule dispersion used. The microcapsule dispersions prepared in the examples and comparative examples were applied to the above formulations to obtain different thermosensitive colorimetric layers.

[0216] The distinguishing technical features in the embodiments are shown in Table 1, and some parameters of the microcapsule dispersions prepared in the embodiments and comparative examples are shown in Table 2.

[0217] Table 1

[0218]

[0219] Table 2

[0220]

[0221]

[0222] Table 2 shows that the microcapsule dispersion obtained in Comparative Example 3 exhibits a certain degree of aggregation and uneven particle size distribution. The microcapsule dispersions obtained in Comparative Examples 4-6 show severe aggregation and uneven particle size distribution. The microcapsule dispersion obtained in Comparative Example 7 has a relatively large particle size.

[0223] (iv) Preparation of surface protective layer

[0224] By weight fraction: 65 parts polyvinyl alcohol, 15 parts silica sol, 2 parts silicone emulsion, 2 parts paraffin emulsion, 5 parts oxidized polyethylene wax emulsion, 4 parts zinc stearate emulsion, 6 parts boric acid, and 1 part silicone wetting and leveling agent; mix and dilute with deionized water, and stir evenly to form a surface protective coating liquid with a solid content of 10%.

[0225] (V) Coating

[0226] The above-obtained heat-sensitive layer coating liquid and surface protective layer coating liquid were applied using a curtain coating method at a concentration of 90 g / m². 2 60g / m 2 The coating was applied to a specific amount, with PET as the supporting substrate, and the film was thoroughly dried to obtain the sample film.

[0227] (vi) Performance Testing

[0228] 1. Heat the film for 5 seconds using a static colorimeter to develop color, and measure the density value within a certain temperature range at 10°C intervals to confirm the color development range. The color development range is the response temperature range from the initial color development temperature to the saturation color development temperature.

[0229] 2. A 14-level grayscale image was printed using a medical thermal imaging printer. The density value of each grayscale patch was tested, and the density value was input into the printer's built-in calculation module to obtain the corresponding energy width data. Under the corresponding energy curve, a lung CT image was printed for image resolution and image quality evaluation. The higher the energy width data, the higher the image resolution. The printed lung CT image was compared with the original image on the monitor to evaluate image details and image quality.

[0230] 3. Use a haze / transmittance meter to test the haze value of the film. The lower the haze value, the better the film's transparency, the better its appearance, and the more beneficial it is for image observation during medical diagnosis.

[0231] Table 3

[0232]

[0233]

[0234] Analysis of the results in the table shows that, in Examples 1-11, the preferred method is to produce polyurethane-polyurea microcapsules through a two-step polymerization reaction. Furthermore, when the amounts of polyether polyol and polyamine are within the preferred range, the initial color development temperature of Examples 1-11 can be reduced to 80°C, and the color development range can reach 50°C.

[0235] Comparative Examples 2 and 4 showed no secondary polymerization of polyamines, resulting in low initial color development temperatures (as low as 70℃) and a color development range of only 40℃. This limited energy range led to low image resolution and poor image quality. Comparative Examples 1 and 3, on the other hand, showed no primary polymerization of polyether polyols, with initial color development temperatures reaching 100℃. Even with a color development range exceeding 50℃, Comparative Example 3 produced a washed-out image with insufficient detail. Comparative Examples 3, 4, 5, and 6, where microcapsules exhibited aggregation, showed a significant increase in film haze, negatively impacting the final image quality. In Comparative Example 7, the capsule wall failed to completely encapsulate the core, resulting in free core material. The developing layer coating solution turned black, and the film appeared black, failing to reproduce the image. Analysis of the results in the table shows that, compared to Comparative Examples 1-7, the thermal film printed images in Examples 1-10 have the characteristics of a wide dynamic printing range, high image resolution, and clear printing details, which can well meet the imaging requirements of medical thermal images. Comparative Examples 4 and 6 have saturated optical densities below 2.70, and Comparative Example 7 has a low density above 0.20 because the developing layer coating solution has turned black, which does not meet the basic requirements of the imaging printer's calculation module for color density and image, thus the corresponding energy width data cannot be obtained.

[0236] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A thermosensitive microcapsule dispersion, characterized in that, The thermosensitive microcapsule dispersion has a D90 ≤ 0.75 μm and a D100 ≤ 1.35 μm; the thermosensitive microcapsule dispersion contains thermosensitive microcapsules, each thermosensitive microcapsule comprising a capsule wall and a capsule core, wherein the weight percentage of the capsule wall and the capsule core is (45-66):(34-55); the capsule wall is a polyurethane-polyurea composite, and the capsule core is a chromogenic dye precursor and a solvent; The preparation method of the thermosensitive microcapsule dispersion includes the following steps: (1) Mix the color-developing dye precursor, organic solvent and polyisocyanate, heat until dissolved, and prepare oil phase mixture A; (2) After cooking polyvinyl alcohol, a basic protective liquid is obtained. A surfactant and polyether polyol are added and mixed evenly to obtain an aqueous phase mixture B. The polyether polyol has a functionality of 2-3 and a molecular weight of 400-1000. (3) Add oil phase mixture A to aqueous phase mixture B, homogenize and emulsify to obtain oil-in-water mixture C; wherein, the polyisocyanate and polyether polyol undergo a single polymerization reaction to obtain a polyurethane capsule wall skeleton; (4) The diluted polyamine is added to the oil-in-water mixture C, and the reaction is carried out to obtain the thermosensitive microcapsule dispersion; wherein, the polyisocyanate and the polyamine undergo a secondary polymerization reaction, and on the basis of the polyurethane capsule wall skeleton, a polyurea capsule wall is generated to nest and fill the polyurethane capsule wall skeleton, forming a polyurethane-polyurea composite capsule wall. The molar ratio of the polyether polyol to the polyisocyanate is (0.1-1.0):1, and the molar ratio of the polyamine to the polyisocyanate is (0.1-2):

1.

2. The thermosensitive microcapsule dispersion as described in claim 1, characterized in that, In step (1), the mass ratio of chromogenic dye precursor, organic solvent, and polyisocyanate is chromogenic dye precursor: organic solvent: polyisocyanate = (3.5-5.7): (14-25): (3.5-6.6). In step (2), the mass ratio of polyvinyl alcohol, surfactant, and polyether polyol is vinyl alcohol: surfactant: polyether polyol = (7.5-11): (2.5-4.5): (2.5-25).

3. The thermosensitive microcapsule dispersion as described in claim 1, characterized in that, In step (1), the temperature is heated to 60-85℃; in step (2), the temperature is cooked to 60-95℃; in step (3), the homogenization temperature is 50-80℃; and in step (4), the reaction temperature is 50-70℃.

4. The thermosensitive microcapsule dispersion as described in claim 1, characterized in that, The polyisocyanates are hexamethylene diisocyanate, hexamethylene diisocyanate dimer, hexamethylene diisocyanate trimer, isophorone diisocyanate, isophorone diisocyanate dimer, isophorone diisocyanate trimer, toluene diisocyanate, hydrogenated toluene diisocyanate, toluene diisocyanate dimer, toluene diisocyanate trimer, phenyl diisocyanate, phenyl diisocyanate-trimethylolpropane, and phenyl diisocyanate bisphenol A.

5. The thermosensitive microcapsule dispersion as described in claim 4, characterized in that, The polyisocyanate is a mixture of phenyl dimethyl diisocyanate-trimethylolpropane and isophorone diisocyanate.

6. The thermosensitive microcapsule dispersion as described in claim 1, characterized in that, Includes at least one of the following (a)-(e): (a) The polyamine is at least one of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; (b) The degree of polymerization of the polyvinyl alcohol is 1000-3000, and the degree of hydrolysis is ≤90; (c) The surfactant is at least one of Tween 60, Tween 80, sodium dodecyl sulfate, calcium dodecyl sulfate, and dodecylphenol polyoxyethylene ether; (d) The organic solvent is at least one of ethyl acetate and dimethylbiphenyl; (e) The chromogenic dye precursor is at least one of 2-phenylamino-3-methyl-6-dibutylaminofluorane, 3-(N-ethyl-isopentanamino)-6-methyl-7-anilinofluorane, 2-(2-4-dimethylamino)-3-methyl-6-diethylaminofluorane, 3,3-bis(4-diethylamino-2-ethoxyphenyl)-4-azaphthalide, 3-diethylamino-6,8-dimethylfluorane, 9 (9H)oxanthracene-2-carboxylic acid-6-(diethylamino)-3-oxo-ethyl ester, and N,N-dimethyl-4-(2-(2-(octyloxy)phenyl)-6-phenylpyridin-4-yl)aniline.

7. The application of the thermosensitive microcapsule dispersion as described in any one of claims 1-5 in a thermosensitive colorimetric layer.

8. A thermosensitive colorimetric layer, characterized in that, It comprises the following components in parts by weight: 30-50 parts of color developer, 20-40 parts of the thermosensitive microcapsule dispersion according to any one of claims 1-5, 10-30 parts of adhesive, and 0.5-3 parts of wetting agent.

9. The application of the thermal color developing layer as described in claim 7 in thermal medical films.

Images