Photochromic dye nanoparticles and preparation method thereof

Abstract

The invention discloses a photochromic dye nano-microsphere and a preparation method thereof, and belongs to the technical field of fine chemicals and functional materials. In the preparation process of the photochromic nano-dye microsphere, the photochromic dye molecules are directly copolymerized with monomers, and the formed photochromic polymer particles can prevent the leakage of the dye. At the same time, the flexibility of the polyether provides a good color change microenvironment for the dye molecules, accelerates the color change and fading speed, and can also improve the weather resistance of the photochromic dye. In addition, the preparation process is simple and suitable for mass production.

Description

Technical Field

[0001] The invention relates to a photochromic dye nano-microsphere and a preparation method thereof, belonging to the technical field of fine chemicals and functional materials. Background Art

[0002] Photochromism refers to the reversible transformation of certain substances between two states with different colors after being excited by light. Organic photochromic materials, such as spiropyrans, naphthopyrans, spirooxazines, azobenzenes, fulgides and other photochromic materials have been widely used in the fields of lenses, plastic products, coatings, textiles, inks, etc. Among them, naphthopyran compounds have strong structural designability and rich colors after being excited by ultraviolet light, so they are favored by researchers and users. However, naphthopyran compounds usually need to be excited by ultraviolet light in solution or in a flexible polymer system to achieve reversible changes in structure and color, and it is difficult to exert their photochromic properties in the solid state.

[0003] In order to improve the utilization scope of photochromic dyes, in-situ polymerization or emulsion polymerization is usually used to encapsulate photochromic dye molecules in polymer particles to form microcapsules, which can not only maintain the excellent color-changing properties of photochromic dyes, but also avoid the influence of the external environment (acid, alkali, air, metal ions, etc.) on photochromic dyes, and improve their weather resistance. At present, the more common method of encapsulating photochromic dyes is the microencapsulation method, which usually dissolves the color-changing dye in an organic solvent, and then wraps polyurethane, polyurea, melamine ester, polyaniline, and natural polymers such as chitosan and sodium alginate on the surface of the droplet through emulsion polymerization. However, the microcapsules obtained by this conventional method usually have unsatisfactory mechanical strength, and the core material may also leak. More importantly, the size of the microcapsules formed by this method is usually 5-10μm, and larger particles added to the coating or printing and dyeing coating will cause poor dispersibility, resulting in problems such as poor surface flatness of the coating or printing and dyeing coating.

[0004] If the color-changing dye is cross-linked and polymerized with a polymer monomer through chemical bonds to form a nano-scale color-changing microsphere, the above-mentioned shortcomings of the color-changing microcapsule can be avoided. However, the nano-sized photochromic dye microsphere has strict requirements on the selection of polymer monomers and the polymerization process, and needs to have good transparency, stable chemical properties, and sufficient mechanical strength. Therefore, it is necessary to screen suitable polymer monomers and develop suitable polymerization processes to prepare a nano-sized photochromic dye microsphere.

[0005] At present, in the prior art, there are patents CN 117511250 A (a photochromic dye microsphere and its preparation method) and patent CN 114262423 A (a photochromic microsphere with adjustable hardness and its preparation method), each of which discloses a similar scheme of using photochromic dyes to generate microspheres through chemical reactions. However, on the one hand, these schemes still use emulsion polymerization, and the size is still at the μm level. On the other hand, there is a lack of specific research on the fading effect. Summary of the invention

[0006] In view of the defects and shortcomings of the existing microcapsule technology, in order to improve the application field and weather resistance of photochromic dyes, the present invention provides a nano-sized photochromic dye microsphere and a preparation method thereof; the method comprises the following steps: copolymerizing photochromic dye molecules with a special structure with isocyanate and polyether polyol, and then cross-linking and polymerizing the photochromic dye nano-microspheres through small molecule polyols; and the size of the photochromic microspheres can be effectively controlled by adjusting the polymer monomer ratio and the polymerization process conditions.

[0007] The first object of the present invention is to provide a method for preparing photochromic dye nanospheres, the method comprising the following steps:

[0008] Dissolve isocyanate, color-changing dye and polyether polyol in an organic solvent, add a catalyst and perform prepolymerization at 40-80°C for 0.5-5h to form a prepolymer; then add a small molecule polyol as a cross-linking agent, continue to react at 40-100°C for 1-10h, and add a fatty alcohol to block the reaction after the reaction is completed; cool the reaction solution and centrifuge to retain the solid, wash and dry the solid to obtain photochromic dye nanospheres.

[0009] In one embodiment of the present invention, the isocyanate is one or more of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI).

[0010] In one embodiment of the present invention, the color-changing dye is as shown in the following formula I, formula II or formula III:

[0011]

[0012] Among them, the substituents R1 to R 11 are independently selected from hydrogen, methyl, ethyl, methoxy, ethoxy, isopropoxy, hydroxyl, alkyl alcohol (—(CH2) n OH), alkoxy alcohol (—O(CH2) nOH), trifluoromethyl, halogen, -N(CH3)2, -N(CH2CH3)2, methyl carboxylate (-COOMe), ethyl carboxylate (-COOEt), piperidinyl or polyether, 1≤n≤5.

[0013] In one embodiment of the present invention, halogen is fluorine, chlorine or bromine.

[0014] In one embodiment of the present invention, the substituents R1 to R 11 At least two R groups are hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5.

[0015] In one embodiment of the present invention, the substituents R1 to R 11 There are 2 to 4 R groups that are hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5.

[0016] Specific optional, R 1～2 and R 3～4 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0017] Specific optional, R 1～2 and R5 each have an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0018] Specific optional, R 1～2 and R 6～7 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0019] Specific optional, R 1～2 and R 8～9 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0020] Specific optional, R 1～2 and R10～11 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0021] Specific optional, R 3～4 and R5 each have an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0022] Specific optional, R 3～4 and R 6～7 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0023] Specific optional, R 3～4 and R 8～9 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0024] Specific optional, R 3～4 and R 10～11 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0025] Specific optional, R5 and R 6～7 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0026] Specific optional, R5 and R 8～9 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0027] Specific optional, R5 and R 10～11 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2)n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0028] Specific optional, R 6～7 and R 8～9 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0029] Specific optional, R 6～7 and R 10～11 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0030] Specific optional, R 8～9 and R 10～11 Each of them has an R group of hydroxyl, alkyl alcohol (—(CH2) n OH) or alkoxy alcohol (—O(CH2) n OH), 1≤n≤5; other groups do not contain hydroxyl groups.

[0031] In one embodiment of the present invention, the polyether polyol is preferably polyethylene glycol.

[0032] In one embodiment of the present invention, the molecular weight of the polyether polyol is 200 to 600 g / mol.

[0033] In one embodiment of the present invention, the organic solvent is one or more of N-methylpyrrolidone, acetone, DMSO, toluene, tetrahydrofuran, DMF, acetonitrile, cyclohexanone, cyclohexane, and ethyl acetate.

[0034] In one embodiment of the present invention, the catalyst is dibutyltin dilaurate or dioctyltin dilaurate.

[0035] In one embodiment of the present invention, the small molecule polyol is one or more of trimethylolpropane, pentaerythritol, triethanolamine, glycerol, and 2,2-dihydroxypropionic acid.

[0036] In one embodiment of the present invention, the fatty alcohol is a fatty alcohol with a carbon chain length of 3 to 18.

[0037] In one embodiment of the present invention, the molar ratio of isocyanate to polyether polyol is 5:1 to 1.5:1.

[0038] In one embodiment of the present invention, the amount of the color-changing dye added is 1% to 5% of the molar amount of the isocyanate.

[0039] In one embodiment of the present invention, the amount of the organic solvent used is 2 to 8 times the total mass of the isocyanate and the polyether polyol.

[0040] In one embodiment of the present invention, the amount of the catalyst used is 0.5% to 3% of the total mass of the isocyanate and the polyether polyol.

[0041] In one embodiment of the present invention, the molar ratio of the small molecule polyol to the isocyanate is 1:8 to 1:2.

[0042] In one embodiment of the present invention, the amount of fatty alcohol used is 10% to 20% of the molar amount of isocyanate.

[0043] In one embodiment of the present invention, the drying is preferably vacuum drying, and the drying temperature is 40-50°C.

[0044] The photochromic dye nano-microspheres prepared by the invention are applied in the fields of daily chemicals, textiles, anti-counterfeiting materials or coatings.

[0045] The beneficial effects of the present invention are:

[0046] (1) In the preparation process of the photochromic nano dye microspheres of the present invention, the photochromic dye molecules are directly copolymerized with the monomers to form photochromic polymer particles (in a solid state) that can prevent the dye from leaking. At the same time, the flexibility of the polyether provides a good color change microenvironment for the dye molecules, accelerates their color change and fading speed, and can also improve the weather resistance of the photochromic dye. In addition, the preparation process is simple and suitable for mass production.

[0047] (2) The photochromic microspheres of the present invention have a particle size of less than 1 μm and are uniform in size, have a smooth surface, and have good dispersibility, which can avoid the problem of poor surface flatness of coatings or printing and dyeing coatings, and can be widely used in the fields of daily chemicals, textiles, anti-counterfeiting, and coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the reaction process of the photochromic dye nanospheres prepared in Example 1 of the present invention.

[0049] Figure 2 This is a scanning electron microscope image of the photochromic dye nanospheres prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0050] The present invention is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0051] Source of raw materials

[0052] Unless otherwise specified, the raw materials used in the examples and comparative examples are all common commercially available products.

[0053] Example 1

[0054] A method for preparing photochromic dye nanoparticles comprises the following steps:

[0055] Among them, the molecular structure of the dye used is as follows:

[0056]

[0057] 20 mL of N-methylpyrrolidone was added to a 50 mL reaction bottle, followed by 20 mmol of IPDI, 12 mmol of polyethylene glycol (PEG400, molecular weight of about 400 g / mol), and 0.2 mmol of a photochromic dye. After the substances were completely dissolved, 0.5 mol of dibutyltin dilaurate was added, and the mixture was stirred and reacted at 60° C. for 1 h. After the prepolymer was formed, 3 mmol of trimethylolpropane was added thereto, and the mixture was heated to 80° C. and stirred and reacted for 4 h. After a large amount of white solid was formed, 2 mmol of dodecanol was added to block the reaction. The reaction solution was cooled to room temperature and then centrifuged to retain the solid product. The solid product was then washed with water and acetone, respectively, and finally dried at 40° C. in a vacuum to obtain photochromic dye nanospheres.

[0058] The reaction process of preparing nanospheres in this embodiment is as follows Figure 1 The scanning electron microscope image of the formed photochromic dye nanospheres is shown in Figure 2 As shown, the particle size of the nanospheres is about 500 nm.

[0059] Example 2

[0060] In this example, the size of the nanospheres is changed by adjusting the content of the small molecule polyol crosslinking agent. The only difference from Example 1 is that the amount of trimethylolpropane is changed to 5 mmol, and the other parameters and conditions are the same as those in Example 1. The particle size of the nanospheres finally obtained is about 800 nm.

[0061] Example 3

[0062] The only difference from Example 1 is that the amount of trimethylolpropane is changed to 7 mmol, and the other parameters and conditions are the same as those in Example 1. The particle size of the nano-microspheres finally obtained is about 1100 nm.

[0063] Example 4

[0064] The only difference from Example 1 is that polyethylene glycol (PEG400) is replaced with an equal molar amount of PEG200, and the other parameters and conditions are the same as those in Example 1. The particle size of the nano-microspheres finally prepared is about 400 nm.

[0065] Example 5

[0066] The only difference from Example 1 is that IPDI is replaced with an equal molar amount of HDI, and the other parameters and conditions are the same as those in Example 1. The particle size of the nano-microspheres finally prepared is about 1200 nm.

[0067] Comparative Example 1

[0068] The only difference from Example 1 is that polyethylene glycol (PEG400) is replaced with PEG2000 in an equal molar amount, and the other parameters and conditions are the same as those in Example 1. The particle size of the nano-microspheres finally prepared is about 3500 nm, and the cross-linking is serious.

[0069] Comparative Example 2

[0070] The only difference from Example 1 is that no small molecule polyol cross-linking agent is added, and finally no solid microspheres are formed.

[0071] Table 1 Particle size and dispersibility of photochromic dye nanospheres

[0072] sample Average size nm Dispersibility Example 1 500 excellent Example 2 800 excellent Example 3 1100 excellent Example 4 400 excellent Example 5 1200 excellent Comparative Example 1 3500 Severe cross-linking Comparative Example 2 — No microspheres formed

[0073] The photochromic dye nanospheres finally obtained in Examples 1 to 5 and the initial dye molecules were made into lenses respectively. The preparation process was as follows: 4 parts of ethoxybisphenol A dimethacrylate (EBPDMA, EO / phenol = 1.3), 1 part of poly (ethylene glycol) 400 dimethacrylate (PEGDMA), 0.4wt% of AIBN (free radical initiator) relative to the total mass, and 1.5% of dye molecules relative to the total mass (the amount of photochromic dye nanospheres added needs to be calculated after calculating the proportion of dye molecules in the microspheres) to prepare a mixture. Then, the obtained mixture was poured into a mold and thermally cured at 110°C for 2h. The thickness of the produced test lens was about 2 mm. The lens was irradiated with a 365nm ultraviolet light source, and the color change rate and fading half-life T of the lens sample were recorded. 1 / 2 , record the data as shown in Table 2:

[0074] Table 2 Photochromic dye nano-microspheres fade performance

[0075] sample Color change rate(s) <![CDATA[Fading half-life T 1 / 2 > Example 1 6 28 Example 2 6 33 Example 3 7 31 Example 4 6 22 Example 5 8 39 Photochromic dyes 10 45

[0076] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing photochromic dye nanospheres, characterized in that: The method comprises the following steps: Dissolve isocyanate, color-changing dye and polyether polyol in an organic solvent, add a catalyst and perform prepolymerization at 40-80°C for 0.5-5h to form a prepolymer; then add a small molecule polyol as a crosslinking agent, continue to react at 40-100°C for 1-10h, and after the reaction is completed, add a fatty alcohol to block the reaction; cool the reaction solution and centrifuge to retain the solid, wash and dry the solid, and obtain the photochromic dye nanospheres; The molecular weight of the polyether polyol is 200 to 600 g / mol; The color-changing dye is shown in the structure of the following formula I, formula II or formula III: Among them, the substituents R1 to R 11 Each independently selected from hydrogen, methyl, ethyl, methoxy, ethoxy, isopropoxy, hydroxyl, alkyl alcohol-(CH2) n OH, alkoxy alcohol—O(CH2) n OH, trifluoromethyl, halogen, -N(CH3)2, -N(CH2CH3)2, methyl carboxylate, ethyl carboxylate, piperidinyl or polyether, 1≤n≤5; Substituent R1~R 11 At least two R groups are hydroxyl, -(CH2) n OH or —O(CH2) n OH.

2. The preparation method according to claim 1, characterized in that: The isocyanate is one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

3. The preparation method according to claim 1, characterized in that: The organic solvent is one or more of N-methylpyrrolidone, acetone, DMSO, toluene, tetrahydrofuran, DMF, acetonitrile, cyclohexanone, cyclohexane, and ethyl acetate.

4. The preparation method according to claim 1, characterized in that: The catalyst is dibutyltin dilaurate or dioctyltin dilaurate.

5. The preparation method according to claim 1, characterized in that: The small molecule polyol is one or more of trimethylolpropane, pentaerythritol, triethanolamine, glycerol, and 2,2-dihydroxypropionic acid.

6. The preparation method according to claim 1, characterized in that: The fatty alcohol is a fatty alcohol with a carbon chain length of 3 to 18.

7. The preparation method according to claim 1, characterized in that: The molar ratio of isocyanate to polyether polyol is 5:1-1.5:1; and the added amount of the color-changing dye is 1%-5% of the molar amount of the isocyanate.

8. The preparation method according to claim 1, characterized in that: The dosage of the organic solvent is 2 to 8 times of the total mass of the isocyanate and the polyether polyol; the dosage of the catalyst is 0.5 to 3% of the total mass of the isocyanate and the polyether polyol.

9. The preparation method according to claim 1, characterized in that: The molar ratio of small molecule polyol to isocyanate is 1:8-1:2; the amount of fatty alcohol used is 10%-20% of the molar amount of isocyanate.

10. Use of the photochromic dye nanospheres according to any one of claims 1 to 9 in the fields of daily chemicals, textiles, anti-counterfeiting materials or coatings.

Images