NANO fluorescent latex pigment having high fluorescence intensity and high stability and preparation method therefor

Abstract

A nano fluorescent latex pigment having high fluorescence intensity and high stability and a preparation method therefor, belonging to the technical field of fluorescent pigments. The nano fluorescent latex pigment comprises an oil phase and an aqueous phase, wherein the oil phase comprises: 0.8-0.9 wt% of a fluorescent dye, 40-45 wt% of a polymer monomer, 0.2-0.22 wt% of a co-emulsifier and 0.2-0.22 wt% of an initiator; and the aqueous phase comprises: 5-7 wt% of a mixed emulsifier and 0-0.3 wt% of sodium bicarbonate, with the balance being water. The preparation method for the nano fluorescent latex pigment comprises four steps of preparing the oil phase, preparing the aqueous phase, preparing a miniemulsion and polymerizing the miniemulsion. By means of setting the ingredients and dosage ranges of the oil phase and the aqueous phase and by means of the miniemulsion polymerization process, the present invention successfully prepares the nano fluorescent latex pigment having high fluorescence intensity, small dispersion particle size, uniform distribution and good dispersion stability, thereby expanding the application range of nano fluorescent latex pigments.

Description

A nano fluorescent latex pigment with high fluorescence intensity and high stability and its preparation method Technical Field

[0001] The invention belongs to the technical field of fluorescent pigments, and in particular relates to a nano fluorescent latex pigment with high fluorescence intensity and high stability and a preparation method thereof. Background Art

[0002] Fluorescent dyes are functional dyes that can absorb short-wavelength electromagnetic waves in the ultraviolet or visible light bands and convert them into long-wavelength electromagnetic waves. The converted long-wavelength electromagnetic waves usually fall within the visible light range and can produce a dazzling fluorescent effect when superimposed with general reflected light. Therefore, the application scope of fluorescent dyes covers many fields such as display, identification, detection, and probes. However, fluorescent dyes have the characteristic of being easily quenched by fluorescence, that is, the irreversible destruction of fluorescent molecules due to internal and external factors, resulting in inactivation or decline of fluorescence performance, shortening of fluorescence lifetime, and poor controllability of fluorescence performance. This brings problems such as poor convenience and repeatability to the application of fluorescent dyes.

[0003] Fluorescent latex pigment is a fluorescent material with a monodisperse spherical structure, which has the characteristics of high fluorescence intensity, high fluorescence stability, and simple use. Fluorescent latex pigment mainly combines fluorescent dyes with high molecular organic compounds, which solves the problem of difficult to control the fluorescence stability of fluorescent dyes during application and reduces the technical barriers to the application of fluorescent materials. At present, there are many methods for the preparation of fluorescent latex pigments. According to the different ways of combining fluorescent dyes with latex microspheres, they can be divided into adsorption method, embedding method, grafting method, copolymerization method, etc. Among them, the embedding method is a preparation method in which the fluorescent dye is added before or during the polymerization reaction, and the fluorescent dye molecules are finally entangled by the polymer chain and wrapped inside the microspheres to form fluorescent microspheres. It has the advantages of uniform fluorescence distribution and high fluorescence intensity.

[0004] Currently, the preparation technology for fluorescent latex pigments with high fluorescence intensity and high stability is blocked by countries such as the United States, Japan, and South Korea. Domestic fluorescent latex pigments have performance gaps, primarily manifested in low fluorescence intensity, poor dispersion stability during storage, transportation, and application, and further decline in fluorescence intensity as the latex pigment aggregates, failing to meet the requirements of high-intensity fluorescent applications. Summary of the Invention

[0005] The purpose of the present invention is to provide a nano fluorescent latex pigment with high fluorescence intensity and high stability and a preparation method thereof, so as to solve the technical problems of low fluorescence intensity and poor dispersion stability of existing fluorescent latex pigments.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A nano fluorescent latex pigment with high fluorescence intensity and high stability comprises an oil phase and an aqueous phase. Calculated by weight, the oil phase comprises: 0.8-0.9wt% of a fluorescent dye, 40-45wt% of a polymer monomer, 0.2-0.22wt% of an emulsifier, and 0.2-0.22wt% of an initiator; the aqueous phase comprises: 5-7wt% of a mixed emulsifier, 0-0.3wt% of sodium bicarbonate, and the balance water (i.e., water is used to make up the weight percentage to 100wt%).

[0008] Furthermore, the fluorescent dye includes but is not limited to any one of rhodamine, fluorescent yellow, fluorescent rose red, fluorescent orange, fluorescent green, and fluorescent violet.

[0009] Furthermore, the particle size of the dispersion in the nano fluorescent latex pigment is 80-105 nm.

[0010] Furthermore, the polymer monomers are composed of styrene, methacrylic acid and acrylonitrile mixed in a mass ratio of 48-48.5:1:17-17.2.

[0011] The polymer monomer composed of the above components has good compatibility with fluorescent dyes, which can ensure the color development performance and fluorescence intensity of the nano fluorescent latex pigment; at the same time, it has an appropriate glass transition temperature, which can regulate the steric hindrance effect and electrostatic repulsion between particles, promote the uniform dispersion of nanoparticles in the nano fluorescent pigment, and avoid large-scale precipitation of fluorescent dyes.

[0012] Furthermore, the co-emulsifier includes any one of hexadecane, hexadecanol, and glycerol.

[0013] Furthermore, the initiator is an oil-soluble initiator, and the oil-soluble initiator includes one of azobisisobutyronitrile (AIBN) and azobisisobutylamidine dihydrochloride (AIBA).

[0014] Furthermore, the mixed emulsifier is composed of a polymerizable anionic emulsifier and a nonionic emulsifier mixed in a mass ratio of 5:1; the polymerizable anionic emulsifier includes but is not limited to one or more of SR-10, R-4001, and R-4006 mixed in any ratio; the nonionic emulsifier includes but is not limited to one or more of Y-8093, Y-8094, PVA1788, and OP-10 mixed in any ratio. By compounding the polymerizable anionic emulsifier and the nonionic emulsifier and controlling the overall amount of the mixed emulsifier, the particle size of the dispersion in the nano fluorescent latex pigment can be made small and uniform, thereby improving the dispersion uniformity and dispersion stability of the nano fluorescent latex pigment.

[0015] A method for preparing a nano fluorescent latex pigment with high fluorescence intensity and high stability comprises the following steps:

[0016] (1) Preparation of oil phase: Dissolve the fluorescent dye in the polymer monomer, then add the co-emulsifier and initiator to mix and obtain a clear and transparent oil phase;

[0017] (2) Preparation of aqueous phase: Add the mixed emulsifier to water and stir to dissolve, then add sodium bicarbonate and stir to dissolve to prepare the aqueous phase;

[0018] (3) Preparation of miniemulsion: The oil phase prepared in step (1) is added dropwise to the water phase prepared in step (2), and simultaneously emulsified and dispersed using a homogenizer to prepare an oil-in-water miniemulsion;

[0019] (4) Miniemulsion polymerization: The miniemulsion prepared in step (3) was transferred to a three-necked flask equipped with a stirrer, a thermometer, and a feed port. The polymerization reaction was carried out at a speed of 400-600 rpm for 7 hours. After cooling and discharging, the nano-fluorescent latex pigment was obtained after filtering and centrifugal washing to remove impurities.

[0020] Furthermore, the rotation speed of the homogenizer used for emulsification in step (3) is 7-9 krpm; and the emulsification time is 35-45 min.

[0021] Furthermore, the temperature of the polymerization reaction in step (4) is 55-65° C. By precisely controlling the temperature during the miniemulsion polymerization reaction, the color development performance, fluorescence performance and fluorescence life of the nano fluorescent latex pigment are guaranteed.

[0022] Beneficial effects of the present invention:

[0023] The present invention first sets the composition and dosage range of the polymer monomer, improves the compatibility with the fluorescent dye, enables the fluorescent dye to achieve optimal color development performance, optimizes the glass transition temperature of the polymer monomer, regulates the steric hindrance effect and electrostatic repulsion between particles, promotes the dispersion of the dispersion in the nano fluorescent latex pigment, and avoids the problem of reduced fluorescence performance caused by large-scale agglomeration of the fluorescent dye; secondly, by compounding a polymerizable anionic emulsifier and a nonionic emulsifier and controlling the overall dosage of the mixed emulsifier, the particle size of the dispersion in the nano fluorescent latex pigment can be made small and uniform, further enhancing the dispersion uniformity and dispersion stability of the nano fluorescent latex pigment; finally, the temperature, emulsification speed and emulsification time in the preparation process of the nano fluorescent latex pigment have a significant influence on the photophysical properties of the fluorescent dye, such as color development performance, fluorescence performance, fluorescence lifetime, etc., and the preparation process parameters are finely regulated to avoid the influence on the fluorescent dye, thereby further enhancing the fluorescence performance of the fluorescent dye;

[0024] The present invention successfully prepares a nano fluorescent latex pigment with high fluorescence intensity, small particle size, uniform distribution and good stability by first emulsifying and dispersing an oil phase and an aqueous phase to obtain a miniemulsion, and then polymerizing the miniemulsion. The invention solves the problem of fluorescence performance degradation or even disappearance of fluorescent dyes due to quenching and inactivation, overcomes the difficulties of existing nano fluorescent latex pigments such as poor stability, uneven pigment particle size distribution, and difficulty in long-term storage and transportation; without affecting the solid content and fluorescence performance, the fluorescence performance is made more stable and controllable, the stability is significantly improved, and the application range of the nano fluorescent latex pigment is further expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] FIG1 is a SEM image of the nano fluorescent latex pigment prepared in Example 2 of the present invention;

[0027] FIG2 is a TEM image of the nano fluorescent latex pigment prepared in Example 2 of the present invention. Implementation Method

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention. Example

[0029] This embodiment provides a nano fluorescent latex pigment with high fluorescence intensity and high stability, which is prepared by the following steps:

[0030] (1) Preparation of oil phase: 0.95 g of rhodamine was dissolved in a polymer monomer consisting of 34.55 g of styrene, 0.75 g of methacrylic acid, and 12.5 g of acrylonitrile, and then 0.24 g of hexadecanol and 0.24 g of AIBN were added and mixed to obtain a clear and transparent oil phase;

[0031] (2) Preparation of aqueous phase: Add a mixed emulsifier consisting of 4.1248 g SR-10, 0.8752 g R-4001, 0.6798 g Y-8093, and 0.3202 g PVA1788 to 60 g water and stir to dissolve to prepare an aqueous phase;

[0032] (3) Preparation of miniemulsion: The oil phase was added dropwise to the water phase within 30 min, and the mixture was emulsified and dispersed at 7 krpm using a homogenizer for 45 min to prepare an oil-in-water miniemulsion.

[0033] (4) Miniemulsion polymerization: The miniemulsion was transferred to a three-necked flask equipped with a stirrer, a thermometer, and a feed port. The temperature was raised to 55°C at a speed of 400 rpm and the reaction was carried out for 7 hours. After cooling and discharging, the material was filtered and centrifuged to remove impurities to obtain a nano fluorescent latex pigment with high fluorescence intensity and high dispersion stability. Example

[0034] This embodiment provides a nano fluorescent latex pigment with high fluorescence intensity and high stability, which is prepared by the following steps:

[0035] (1) Preparation of oil phase: 1.05 g of fluorescent yellow was dissolved in a polymer monomer consisting of 36.35 g of styrene, 0.75 g of methacrylic acid, and 12.9 g of acrylonitrile, and then 0.25 g of hexadecane and 0.25 g of AIBN were added and mixed to obtain a clear and transparent oil phase;

[0036] (2) Preparation of aqueous phase: Add a mixed emulsifier consisting of 5.3995 g SR-10, 0.9817 g R-4001, 0.8508 g Y-8093, and 0.4254 g Y-8094 to 60 g water and stir to dissolve. Then add 0.36 g sodium bicarbonate and stir to dissolve to prepare an aqueous phase.

[0037] (3) Preparation of miniemulsion: The oil phase was added dropwise to the water phase within 30 min, and the mixture was emulsified and dispersed at 8 krpm using a homogenizer for 40 min to prepare an oil-in-water miniemulsion.

[0038] (4) Miniemulsion polymerization: The miniemulsion was transferred to a three-necked flask equipped with a stirrer, thermometer, and feed port. The reaction was heated to 60°C at a speed of 500 rpm for 7 hours. After cooling and discharging, the product was filtered and centrifuged to remove impurities, resulting in a nano-fluorescent latex pigment with high fluorescence intensity and high dispersion stability. The dispersion of the nano-fluorescent latex pigment is shown in Figures 1 and 2. Example

[0039] This embodiment provides a nano fluorescent latex pigment with high fluorescence intensity and high stability, which is prepared by the following steps:

[0040] (1) Preparation of oil phase: 1.07 g of fluorescent green was dissolved in a polymer monomer consisting of 39.12 g of styrene, 0.81 g of methacrylic acid, and 13.87 g of acrylonitrile, and then 0.26 g of glycerol and 0.26 g of AIBA were added and mixed to obtain a clear and transparent oil phase;

[0041] (2) Preparation of aqueous phase: Add a mixed emulsifier consisting of 3.6548 g of R-4006, 3.3452 g of R-4001, 0.6847 g of Y-8093, and 0.7153 g of OP-10 to 65 g of water and stir to dissolve, then add 0.2 g of sodium bicarbonate and stir to dissolve to prepare an aqueous phase;

[0042] (3) Preparation of miniemulsion: The oil phase was added dropwise to the water phase within 30 min, and the mixture was emulsified and dispersed at 9 krpm using a homogenizer for 35 min to prepare an oil-in-water miniemulsion.

[0043] (4) Miniemulsion polymerization: The miniemulsion was transferred to a three-necked flask equipped with a stirrer, a thermometer, and a feed port. The temperature was raised to 65°C at a speed of 600 rpm and the reaction was carried out for 7 hours. After cooling and discharging, the material was filtered and centrifuged to remove impurities to obtain a nano fluorescent latex pigment with high fluorescence intensity and high dispersion stability.

[0044] Comparative Example 1

[0045] Compared with Example 2, in this example, the "polymer monomer composed of 36.35 g of styrene, 0.75 g of methacrylic acid and 12.9 g of acrylonitrile" is replaced by "polymer monomer composed of 49.25 g of styrene and 0.75 g of methacrylic acid", and the other raw materials and preparation methods are the same.

[0046] Comparative Example 2

[0047] Compared with Example 2, in this example, "a polymer monomer consisting of 36.35 g of styrene, 0.75 g of methacrylic acid and 12.9 g of acrylonitrile" is replaced by "a polymer monomer consisting of 35.79 g of styrene, 1.5 g of methacrylic acid and 12.71 g of acrylonitrile", and the remaining raw materials and preparation methods are the same.

[0048] Comparative Example 3

[0049] Compared with Example 2, in this example, "a polymer monomer consisting of 36.35 g of styrene, 0.75 g of methacrylic acid and 12.9 g of acrylonitrile" is replaced by "a polymer monomer consisting of 36.87 g of styrene and 13.13 g of acrylonitrile", and the remaining raw materials and preparation methods are the same.

[0050] Comparative Example 4

[0051] Compared with Example 2, in this example, "a polymer monomer composed of 36.35 g of styrene, 0.75 g of methacrylic acid and 12.9 g of acrylonitrile" is replaced by "a polymer monomer composed of 36.35 g of styrene, 0.75 g of methacrylic acid and 12.9 g of isooctyl acrylate", and the remaining raw materials and preparation methods are the same.

[0052] Comparative Example 5

[0053] Compared with Example 2, in this example, the "polymer monomer composed of 36.35 g of styrene, 0.75 g of methacrylic acid and 12.9 g of acrylonitrile" is replaced by "polymer monomer composed of 36.35 g of methyl methacrylate, 0.75 g of methacrylic acid and 12.9 g of isooctyl acrylate", and the remaining raw materials and preparation methods are the same.

[0054] Comparative Example 6

[0055] Compared with Example 2, this example is different from Example 2, except that the “mixed emulsifier consisting of 5.3995 g SR-10, 0.9817 g R-4001, 0.8508 g Y-8093, and 0.4254 g Y-8094” is replaced by a “mixed emulsifier consisting of 6.4794 g SR-10 and 1.1780 g R-4001”. The remaining raw materials and preparation methods are the same.

[0056] Comparative Example 7

[0057] Compared with Example 2, this example is different from Example 2, except that the “mixed emulsifier consisting of 5.3995 g SR-10, 0.9817 g R-4001, 0.8508 g Y-8093, and 0.4254 g Y-8094” is replaced by a “mixed emulsifier consisting of 5.1049 g Y-8093 and 2.5525 g Y-8094”. The remaining raw materials and preparation methods are the same.

[0058] Comparative Example 8

[0059] Compared with Example 2, this example is different from Example 2, except that the “mixed emulsifier consisting of 5.3995 g SR-10, 0.9817 g R-4001, 0.8508 g Y-8093, and 0.4254 g Y-8094” is replaced by a “mixed emulsifier consisting of 6.3812 g DM-1501, 0.8508 g Y-8093, and 0.4254 g Y-8094”. The remaining raw materials and preparation methods are the same.

[0060] Comparative Example 9

[0061] Compared with Example 2, this example is different from Example 2, except that the “mixed emulsifier consisting of 5.3995 g SR-10, 0.9817 g R-4001, 0.8508 g Y-8093, and 0.4254 g Y-8094” is replaced by a “mixed emulsifier consisting of 6.4793 g SR-10, 1.1781 g R-4001, 1.0210 g Y-8093, and 0.5105 g Y-8094”. The remaining raw materials and preparation methods are the same.

[0062] Comparative Example 10

[0063] Compared with Example 2, this example is different from Example 2, except that the “mixed emulsifier consisting of 5.3995 g SR-10, 0.9817 g R-4001, 0.8508 g Y-8093, and 0.4254 g Y-8094” is replaced by a “mixed emulsifier consisting of 4.3190 g SR-10, 0.7853 g R-4001, 0.6800 g Y-8093, and 0.3400 g Y-8094”. The remaining raw materials and preparation methods are the same.

[0064] Comparative Example 11

[0065] Compared with Example 2, in this example, the step (4) of "raising the temperature to 60°C and reacting for 7 hours" is changed to "raising the temperature to 80°C and reacting for 7 hours", and the rest of the preparation methods are the same.

[0066] Comparative Example 12

[0067] Compared with Example 2, in this example, the step (4) of "raising the temperature to 60°C and reacting for 7 hours" is changed to "raising the temperature to 50°C and reacting for 7 hours", and the rest of the preparation methods are the same.

[0068] Comparative Example 13

[0069] Compared with Example 2, in step (3), the step of "using a homogenizer to emulsify and disperse at 8 krpm for 40 min" was changed to "using a homogenizer to emulsify and disperse at 10 krpm for 40 min", and the rest of the preparation methods were the same.

[0070] Comparative Example 14

[0071] Compared with Example 2, in step (3), the step "using a homogenizer to emulsify and disperse at 8 krpm for 40 min" was changed to "using a homogenizer to emulsify and disperse at 3 krpm for 40 min", and the rest of the preparation methods were the same.

[0072] Comparative Example 15

[0073] Compared with Example 2, in this example, the step (3) of "using a homogenizer to emulsify and disperse at 8 krpm for 40 min" is changed to "using a homogenizer to emulsify and disperse at 10 krpm for 60 min", and the rest of the preparation methods are the same.

[0074] Comparative Example 16

[0075] Compared with Example 2, in this example, the step (3) of "using a homogenizer to emulsify and disperse at 8 krpm for 40 min" is changed to "using a homogenizer to emulsify and disperse at 10 krpm for 20 min", and the rest of the preparation methods are the same.

[0076] Comparative Example 17

[0077] This comparative example is a commercially available nano fluorescent latex pigment (LWF series water-emulsion nano fluorescent latex pigment produced by Huangshan Jiajia Fluorescent Material Co., Ltd.).

[0078] Comparative Example 18

[0079] This comparative example is a commercially available nano fluorescent latex pigment (produced by SINLOIHI).

[0080] Comparative Example 19

[0081] This comparative example adopts conventional emulsion polymerization method to prepare a nano fluorescent latex pigment, which includes the following steps:

[0082] (1) Preparation of oil phase: Weigh 0.94 g of fluorescent yellow and dissolve it in a polymer monomer consisting of 32.94 g of styrene, 0.67 g of methacrylic acid, and 11.09 g of acrylonitrile, and mix well to obtain an oil phase;

[0083] (2) Preparation of aqueous phase: Add a mixed emulsifier consisting of 5.3995 g SR-10, 0.9817 g R-4001, 0.8508 g Y-8093, and 0.4254 g Y-8094 to 60 g water and stir to dissolve. Then add 0.36 g sodium bicarbonate and stir to dissolve to prepare an aqueous phase.

[0084] (3) Emulsion polymerization: under the stirring condition of 2krpm, half of the aqueous phase was slowly dripped into the oil phase within 30min, and the mixture was evenly mixed to obtain a pre-emulsion; 0.18g of APS was weighed and dissolved in 10mL of water to obtain an initiator solution, 1 / 3 of the initiator solution was first dripped into the other half of the aqueous phase, and then the pre-emulsion was slowly dripped under stirring at 400rpm, and the temperature was raised to 75℃. 1 / 3 of the initiator solution was dripped into the reaction system at 1h and 2h respectively, and the mixture was reacted for another 3h. The material was cooled and discharged, and the impurities were removed by filtration and centrifugal washing to obtain a nano fluorescent latex pigment.

[0085] The performance tests were performed on the nano fluorescent latex pigments of Examples 1 to 3 and Comparative Examples 1 to 19:

[0086] 1) Solid content

[0087] The solid content of the sample was determined by weighing: a small amount of pigment sample was taken and dried in an oven to a constant weight. The solid content of the sample was calculated according to the following formula:

[0088] Solid content = ;

[0089] Wherein, M0 is the mass of the sample taken, and M1 is the mass of the sample after drying;

[0090] 2) Particle size and particle size distribution

[0091] Take a small amount of sample and dilute it 1000 times with deionized water. Take an appropriate amount of the diluted sample into a particle size dish, and then put it into the Nano-Zs90 Zeta potential and particle size analyzer to measure the particle size and particle size distribution of the sample at 25°C. The average value of the three measurements is taken.

[0092] 3) Stability

[0093] Take an appropriate amount of sample, seal it tightly, and place it in a 60°C oven for storage. Observe the state of the sample regularly and record the time when precipitation appears at the bottom of the sample to indicate the thermal stability of the sample.

[0094] Take an appropriate amount of sample, seal it tightly, and store it at room temperature. Observe the state of the sample regularly and record the time when precipitation appears at the bottom of the sample to indicate the room temperature storage stability of the sample.

[0095] The test results are shown in Table 1:

[0096] Table 1

[0097]

[0098] According to weight percentage, 10 wt% of the nano fluorescent latex pigments prepared in Examples 1-3 and Comparative Examples 1-19, 5 wt% of the thickener DM5128, and the balance deionized water were stirred and mixed to obtain a printing paste. Cotton fabric was screen-printed, pre-baked at 60°C for 30 minutes, and then transferred to a drying machine and baked at 130°C for 3 minutes to obtain a printed fluorescent fabric. The printed fluorescent fabric was then tested:

[0099] 1) Fluorescence intensity

[0100] The fluorescence intensity of the printed fluorescent fabric is expressed as the intensity difference value, and the magnitude of the intensity difference is the fluorescence intensity. Measurements were performed on a Datacolor 650 desktop spectrophotometer using a D65 light source and a 10° viewing angle. The printed fluorescent fabric obtained in Comparative Example 17 was used as the standard (fluorescence intensity value was 100), and the remaining samples were used as comparison samples. Each piece of printed fluorescent fabric was measured three times at different locations, and the average value was obtained.

[0101] 2) Color fastness

[0102] Test the color fastness grade of printed fluorescent fabrics according to GB / T 5713-2013 standard;

[0103] The results are shown in Table 2 below;

[0104] Table 2

[0105]

[0106] The following conclusions can be drawn from the test data in Table 1 and Table 2:

[0107] The test results of Example 2 and Comparative Examples 1, 4, and 5 show that fluorescent dyes have different fluorescent properties in different dissolution systems. When the polymer monomer and the fluorescent dye are incompatible, the emulsion polymerization reaction will fail. For example, in Comparative Examples 4 and 5, nano fluorescent latex pigments cannot be prepared. The polymer monomer of Example 2 has better compatibility with the fluorescent dye, and the fluorescent latex pigment prepared therefrom has higher fluorescence intensity and dispersion stability.

[0108] The test results of Example 2, Comparative Example 2, and Comparative Example 3 show that when the amount of methacrylic acid is increased, the stability of the nano fluorescent latex pigment is improved, but the fluorescence intensity decreases due to the small particle size and the reduced solid content; when methacrylic acid is not included in the system, although the fluorescence intensity is less affected, the fluorescent latex pigment particle size is larger, the electrostatic repulsion between the particles is lost, resulting in poor stability;

[0109] The test results of Example 2 and Comparative Examples 6, 7, and 8 show that a single type of emulsifier can deteriorate the stability of the nano fluorescent latex pigment, resulting in low solid content and fluorescence intensity. A single type of emulsifier is not sufficient to uniformly disperse the fluorescent dye. At the same time, the use of a non-polymerizable anionic emulsifier cannot meet the dispersion requirements of the fluorescent dye.

[0110] From the test results of Example 2 and Comparative Examples 9 and 10, it can be seen that when the amount of the mixed emulsifier is lower than the amount range set by the present invention, the content of the mixed emulsifier adsorbed on the surface of the polymerized monomer droplets is small, and the oil-water interface stability of the formed emulsion droplets is weak; however, when the amount of the mixed emulsifier exceeds the amount range set by the present invention, the excess mixed emulsifier in the emulsion will be free in the water to form micelles, and after polymerization, tiny empty shell latex particles will be formed and dispersed in the pigment system. The presence of such empty shell latex particles will lead to poor stability of the nano fluorescent latex pigment, and the fluorescence intensity will also be correspondingly reduced due to the presence of the empty shell latex particles.

[0111] The test results of Example 2 and Comparative Examples 11 and 12 show that when the reaction temperature is too high, the fluorescence intensity of the fluorescent latex pigment drops sharply, which is due to fluorescence quenching and inactivation. At the same time, when the temperature is high, the miniemulsion polymerization process is difficult to control and is very prone to implosion. When the temperature is too low, the solid content and fluorescence intensity also decrease significantly. This may be because at lower temperatures, the monomer conversion rate of the miniemulsion polymerization is low and the reaction cannot be fully completed.

[0112] From the test results of Example 2 and Comparative Examples 13 and 14, it can be seen that with the increase of the emulsification speed, the average particle size of the dispersion in the prepared nano fluorescent latex pigment does not change significantly, but the PDI shows a decreasing trend, and the particle size distribution is more uniform; this is because the more intense the shear force of the homogenizer on the emulsion, the more uniform the particle size of the formed emulsion droplets; however, when the emulsification rate is too high, the excessively strong shear force of the homogenizer may cause the emulsifier adsorbed on the surface of the emulsion droplets to desorb and become free in the aqueous phase, where it aggregates to form small-sized empty shell latex particles, thereby affecting the stability of the dispersion system;

[0113] From the test results of Example 2 and Comparative Examples 15 and 16, it can be seen that with the increase of the emulsification time, the particle size of the dispersion in the prepared nano fluorescent latex pigment is not much different, and the PDI is slightly reduced, indicating that the length of the emulsification time has little effect on the average particle size and PDI of the nano fluorescent latex pigment dispersion; but the stability gradually improves. This is because when the emulsification time is short, the prepared nano fluorescent latex pigment dispersion may contain small-size latex particles and large-size latex particles with a large difference in particle size. Although the presence of large latex particles will increase the fluorescence intensity, these large latex particles are prone to aggregation to form precipitation, thereby affecting the stability of the dispersion. With the increase of the emulsification time, the content of large-size latex particles in the nano fluorescent latex pigment dispersion gradually decreases, and the stability of the dispersion is improved. However, the reduction in the content of large-size latex particles will also cause a relative reduction in the content of fluorescent dye carried, resulting in a decrease in fluorescence intensity.

[0114] Finally, considering the comprehensive performance of fluorescence intensity and dispersion stability, the nano fluorescent latex pigments prepared by the present invention are superior to the existing commercially available nano fluorescent latex pigments. Compared with the conventional emulsion polymerization method, the comprehensive performance of the nano fluorescent latex pigments is significantly improved in terms of preparation method.

[0115] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0116] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A nano-fluorescent latex pigment with high fluorescence intensity and high stability, comprising an oil phase and an aqueous phase, characterized in that, calculated by weight percentage, the oil phase includes: 0.8 - 0.9 wt% of fluorescent dye, 40 - 45 wt% of polymer monomer, 0.2 - 0.22 wt% of co-emulsifier, 0.2 - 0.22 wt% of initiator, and the aqueous phase includes: 5 - 7 wt% of mixed emulsifier, 0 - 0.3 wt% of sodium bicarbonate and the balance of water; The polymer monomer is composed of styrene, methacrylic acid and acrylonitrile mixed in a mass ratio of 48 - 48.5:1:17 - 17.

2.

2. A nano-fluorescent latex pigment with high fluorescence intensity and high stability according to claim 1, characterized in that, The fluorescent dye includes any one of rhodamine, fluorescein, fluorescent magenta, fluorescent orange, fluorescent green, fluorescent purple.

3. A nano-fluorescent latex pigment with high fluorescence intensity and high stability according to claim 1, characterized in that, The particle size of the dispersion in the nano-fluorescent latex pigment is 80 - 105 nm.

4. A nano-fluorescent latex pigment with high fluorescence intensity and high stability according to claim 1, characterized in that, The co-emulsifier includes any one of hexadecane, cetyl alcohol, glycerol.

5. A nano-fluorescent latex pigment with high fluorescence intensity and high stability according to claim 1, characterized in that, The initiator is an oil-soluble initiator, and the oil-soluble initiator includes any one of azobisisobutyronitrile, azobisisobutylamidine dihydrochloride.

6. A nano-fluorescent latex pigment with high fluorescence intensity and high stability according to claim 1, characterized in that, The mixed emulsifier is composed of a polymerizable anionic emulsifier and a non-ionic emulsifier mixed in a mass ratio of 5:1; the polymerizable anionic emulsifier includes one or more of SR-10, R-4001 and R-4006 mixed in any ratio; the non-ionic emulsifier includes one or more of Y-8093, Y-8094, PVA1788 and OP-10 mixed in any ratio.

7. A preparation method of a nano-fluorescent latex pigment with high fluorescence intensity and high stability according to claim 1, characterized in that, comprises the following steps: (1) Preparation of the oil phase: Dissolve the fluorescent dye in the polymer monomer, then add the co-emulsifier and the initiator and mix to obtain the oil phase; (2) Preparation of the aqueous phase: Add the mixed emulsifier to water and stir to dissolve, then add sodium bicarbonate and stir to dissolve to obtain the aqueous phase; (3) Preparation of the miniemulsion: Drop the oil phase into the aqueous phase, and at the same time use a homogenizer for emulsification and dispersion to prepare an oil-in-water type miniemulsion; (4) Miniemulsion polymerization: Transfer the miniemulsion to a three-necked flask, under the condition of a rotation speed of 400 - 600 rpm, heat up for polymerization reaction for 7 h, after cooling and discharging, remove impurities by filtration and centrifugal washing to obtain the nano-fluorescent latex pigment.

8. A preparation method of a nano-fluorescent latex pigment with high fluorescence intensity and high stability according to claim 7, characterized in that, The rotation speed for emulsification using a homogenizer is 7 - 9 krpm; the emulsification time is 35 - 45 min.

9. A method for preparing a nano - fluorescent latex pigment with high fluorescence intensity and high stability according to claim 7, characterized in that, the temperature of the polymerization reaction is 55 - 65 °C.

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