A preparation method of intramolecular hydrophilic hindered amine

Abstract

The present invention provides a method for preparing an intramolecular hydrophilic hindered amine. This method introduces a hydrophilic chain segment polyether into the molecular structure through the reaction of -OH with NCO, making the molecule have excellent hydrophilicity. The advantage of the present invention is that the prepared hindered amine is hydrophilic within the molecule, without introducing other components such as emulsifiers and carrier resins, has good compatibility with water, and can be used in waterborne coatings to improve their light stability.

Description

Technical Field

[0001] The present invention belongs to the field of functional additives for waterborne coatings, and particularly relates to a preparation method of intramolecular hydrophilic hindered amines. Background Art

[0002] With the continuous increase of the concept of low-carbon environmental protection for mankind, relevant policies and regulations have been introduced at home and abroad to limit VOC emissions. Therefore, industries such as coatings, adhesives, and inks are undergoing a comprehensive transformation towards low-VOC waterborne, high-solid content, and photocuring. For waterborne coatings, adhesives, and inks, traditional hindered amine light stabilizers such as HALS-292, HALS-123, HALS-770, and HALS-622 have poor compatibility or incompatibility problems in waterborne systems.

[0003] Currently, there are products on the market that are suitable for waterborne systems, but most of them use resin coating / nano-loading technology and emulsification technology to achieve the compatibility of light stabilizers with waterborne systems. Although these technologies solve the compatibility problem, they introduce a large amount of emulsifiers, resin carriers, etc. For example, the invention patent with the publication number CN 113527936 A in China discloses a water-dispersible light stabilizer, and its composition in parts by mass is: 75-95 parts of light stabilizer and 5-25 parts of emulsifier; the invention patent with the publication number CN 100415777C discloses a light stabilizer water-based concentrated product form prepared by a multiphase polymerization technique. In this patent, an olefinically unsaturated monomer and a light stabilizer form a water emulsion under the action of an emulsifier, and then microemulsion polymerization is carried out under the action of an initiator. This method coats or loads the light stabilizer through the polymerization of olefin monomers to form an aqueous dispersion. The emulsifiers and polymers introduced by the above methods are not conducive to the performance of the coating such as water resistance, gloss, workability (foam stability, wettability, coarsening), and storage stability. Therefore, improving the compatibility of light stabilizers in waterborne systems from the molecular structure is the fundamental method to solve the problem. Therefore, it is urgent to develop intramolecular hydrophilic light stabilizers to meet the growing anti-aging market of waterborne coatings. Summary of the Invention

[0004] To solve the above problems, the present invention discloses a preparation method of intramolecular hydrophilic hindered amines.

[0005] An intramolecular hydrophilic hindered amine oligomer has the following general structural formula:

[0006] ,

[0007] Among them, R1 is any one of tolyl, diphenylmethane group, isophorone group, dicyclohexylmethane group, hexamethylene, phenyl, and m-xylylene; R2 is any one of hydrogen or methyl; R3 is any one of C1-C8 alkyl or alkoxy groups, and R3 is preferably any one of methyl, methoxy, octyloxy, and cyclohexyloxy.

[0008] Furthermore, the preparation method of the intramolecular hydrophilic hindered amine includes the following steps:

[0009] Step (1): Add 30-60 parts of polyether diol to the reaction kettle. The vacuum dehydration temperature is 100-120 °C. After 30 minutes, cool down to 50 °C.

[0010] Step (2): Slowly add 15-35 parts of diisocyanate, 2-10 parts of solvent, and 0.01-0.1 part of organic catalyst to the reaction kettle according to n diisocyanate: n polyether diol = 2-3:1. After stirring evenly, under nitrogen protection, heat up to 50-100 °C and react for 0.5-1 h, then detect the NCO content. When the residual NCO content reaches the theoretical value, the intermediate shown in formula (Ⅰ) is prepared. The intermediate shown in (Ⅰ) is a polyether-modified diisocyanate, and the reaction process is as follows:

[0011] ;

[0012] Step (3): According to the residual NCO content in step (2), add 15-35 parts of piperidinol to the intermediate shown in formula (Ⅰ) according to n residual NCO: n piperidinol = 1.05:1. React at 50-100 °C under nitrogen protection for 2-4 h to obtain the intramolecular hydrophilic hindered amine shown in formula (Ⅱ). The structural formula of the piperidinol is , and its reaction process is as follows:

[0013] .

[0014] Furthermore, the polyether diol described in step (1) includes polyethylene glycol, polypropylene glycol, or a block copolymer of the two, with an average molecular weight of 400-3000, and preferably an average molecular weight of 400-1000.

[0015] Furthermore, the vacuum dehydration temperature in step (1) is preferably 120 °C.

[0016] Furthermore, the calculation formula for the theoretical value in step (2) is: theoretical value = {[2(m1 / M 1－ m2 / M2)×42] / (m1 + m2)} × 100%, where m1 is the mass of diisocyanate; m2 is the mass of polyether diol; M1 is the molecular weight of diisocyanate; M2 is the average molecular weight of polyether diol.

[0017] Further, the diisocyanate described in step (2) includes any one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI), p-phenylene diisocyanate (PPDI), and m-xylylene diisocyanate (XDI).

[0018] Further, the diisocyanate described in step (2) is preferably any one or more of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and dicyclohexylmethane diisocyanate (HMDI).

[0019] Further, the solvent described in step (2) includes any one of ethyl acetate, acetone, and methyl ethyl ketone, and is preferably acetone.

[0020] Further, in step (2), the molar ratio of the diisocyanate to the polyether diol is 2 to 3:1, preferably 2 to 2.2:1.

[0021] Further, the organometallic catalyst in step (2) is any one or more of organotin, organozinc, or organobismuth.

[0022] Further, the organotin in step (2) includes any one or more of dioctyltin diacetate, dimethyltin dilaurate, dibutyltin dilaurate, dioctyltin dilaurate, dimethyltin dioleate, dibutyltin dioleate, dioctyltin dioleate, dimethyltin bis(isooctyl thioglycolate), dibutyltin bis(isooctyl thioglycolate), dioctyltin bis(isooctyl thioglycolate), dimethyltin dioctanoate, dibutyltin dioctanoate, dioctyltin dioctanoate, dimethyltin diacetate, dibutyltin diacetate, dioctyltin diacetate, dimethyltin bis(dodecylthiol), dibutyltin bis(dodecylthiol), dioctyltin bis(dodecylthiol), dimethyltin oxide, dioctyltin oxide, dimethyltin maleate, dibutyltin maleate, dioctyltin maleate, stannous octoate, stannous oxalate, and dibutyltin bis(acetylacetonate); the organozinc includes any one or more of zinc neodecanoate and zinc naphthenate; and the organobismuth is bismuth isooctanoate.

[0023] Further, the dosage of the catalyst is 0.01 to 0.1% of the total mass of the reactants, preferably 0.02 to 0.05%, and the organometallic catalyst added in step (2) also plays a catalytic role in the reaction of step (3).

[0024] Further, the reaction temperature in step (2) is 50 to 100°C, preferably 60 to 80°C.

[0025] Further, the method for detecting the NCO content in step (2) is the di-n-butylamine method. In the di-n-butylamine method, 12.5 g of di-n-butylamine is dissolved in 800 mL of xylene to prepare a di-n-butylamine solution. Then, 25 mL of the di-n-butylamine solution is transferred into a conical flask, an acid-base indicator is added, and after magnetic stirring evenly, it is titrated with a standard hydrochloric acid solution, and the volume V1 of the consumed standard hydrochloric acid solution is recorded. Weigh 1 g of the intermediate shown in (I) into a conical flask, add another 25 mL of the di-n-butylamine solution, fully dissolve it, add an acid-base indicator, stir evenly, and then titrate it with a standard hydrochloric acid solution. Record the volume V2 of the consumed standard hydrochloric acid solution at this time. Then, calculate the residual NCO content according to the formula 'NCO% = [(V1 - V2) × concentration of the standard hydrochloric acid solution × 4.2] / m'.

[0026] Further, after the piperidinol is dissolved in a solvent, it is added to the reaction system, and the reaction temperature is 50 - 100 °C, preferably 60 - 80 °C.

[0027] Further, the solvent in step (3) is any one of ethyl acetate, acetone, and methyl ethyl ketone, preferably acetone.

[0028] Further, the intramolecular hydrophilic hindered amine prepared by the preparation method is an oligomer with a certain molecular weight distribution, not a single compound.

[0029] Further, the oligomer may contain compounds with urea bonds and hydroxyl groups and trace amounts of unreacted piperidinol monomers.

[0030] Furthermore, the prepared intramolecular hydrophilic hindered amine needs to be vacuumed to remove the solvent at 40 - 60 °C and 0.8 Mpa to obtain the final product.

[0031] The beneficial effects of the present invention are as follows:

[0032] The present invention provides a preparation method of an intramolecular hydrophilic hindered amine. The hindered amine prepared by this method has a high effective content, can achieve good compatibility with water without the need to additionally introduce external emulsifiers, resin carriers, solvents, etc., has no adverse effects on the coating performance, and at the same time has good anti-aging performance, and is particularly suitable for waterborne coatings. The preparation method provided in the present invention completes two-step reactions in one pot, the reaction is simple and easy to control, the post-treatment is easy, the loss is small, the solvent can be recycled, it is economical and environmentally friendly, and it is convenient for industrial production, and is particularly suitable for waterborne coatings. Description of the Drawings

[0033] Figure 1 It is the infrared spectrum of the self-made intramolecular hydrophilic hindered amine (II) in Example 1 of the present invention;

[0034] Figure 2This is a comparison chart of the particle size distribution of the self-made intramolecular hydrophilic hindered amine after being dispersed in water and a competing product's externally emulsified hindered amine in Example 1 of the present invention. Embodiment

[0035] The present invention will be further illustrated below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Example

[0036] Add 60 parts of polyethylene glycol (Mn = 1000) to a 1L reaction kettle, heat up to 120 °C, evacuate for 30 minutes, cool down to 50 °C, add 17 parts of hexamethylene diisocyanate, 0.02 parts of dibutyltin dilaurate, and 5.64 parts of acetone to the system. After stirring evenly, introduce nitrogen into the reaction kettle and slowly heat up to 70 - 75 °C. After reacting for 0.5 - 1 hour, start to detect the NCO content. When the residual NCO content reaches about 6.4% of the theoretical value, dissolve 17.34 parts of pentamethylpiperidinol in acetone and add it dropwise to the system. Control the system temperature at about 70 - 75 °C and continue to react for 2 - 4 hours. When the NCO content reaches about 0.05 - 0.1%, cool down to terminate the reaction. When the system temperature drops to 50 °C, stop nitrogen and evacuate to remove acetone in the system. The acetone is recovered through a condensing device and used as the reaction solvent for the next time. From Figure 1 As can be seen from the infrared spectrum of the intramolecular hydrophilic hindered amine prepared in this example, at 2863 cm -1 , 1457 cm -1 , 1377 cm -1 are the stretching and bending vibration absorption peaks of -CH3 and -CH2-. There is a strong absorption peak of C=O at 1715 cm -1 , and there are ester bond C-O stretching vibration absorption peaks at 1303 cm -1 and 1239 cm -1 . The C-N stretching vibration absorption peaks are at 1348 cm -1 and 1363 cm -1 . The characteristic absorption peaks of N-H are at 3334 cm -1 and 1184 cm -1 . The C-O stretching vibration absorption peak of the ether bond is at 1097 cm -1 . Therefore, it can be proved that the product molecule of this example has the structure shown in formula (Ⅱ) (R2 is H, R3 is methyl). The emulsion formed after the intramolecular hydrophilic hindered amine prepared in this example is dispersed in water and the competing product emulsion are respectively analyzed for particle size. The comparison results are as Figure 2As shown, the intramolecular hydrophilic hindered amine prepared in this example has small and narrow particle size after being dispersed in water, with the particle size all below 0.2 μm. For the competing emulsion, the particle size distribution is in the range of 0.5 - 10 μm, with large and wide particle size distribution, indicating that the emulsion formed by the intramolecular hydrophilic hindered amine prepared in this example is more stable during storage.

[0037] 。 Example

[0038] Preparation method of an intramolecular hydrophilic hindered amine

[0039] Add 57.5 parts of polyethylene glycol (Mn = 600) to a 1L reaction kettle, heat up to 120 °C, evacuate for 30 min, cool down to 50 °C, add 19.32 parts of hexamethylene diisocyanate, 0.02 parts of dibutyltin dilaurate, and 3.61 parts of acetone to the system. After stirring evenly, introduce nitrogen into the reaction kettle, slowly heat up to 70 - 75 °C, and after reacting for 0.5 - 1 h, start to detect the NCO content. When the residual NCO content reaches about 8.9% of the theoretical value, 19.55 parts of pentamethylpiperidinol dissolved in acetone are added dropwise to the system, and the system temperature is controlled at about 70 - 75 °C and continue to react for 2 - 4 h. When the residual NCO content reaches about 0.05 - 0.1%, cool down to terminate the reaction. When the system temperature drops to 50 °C, stop nitrogen and distill under reduced pressure to recover acetone, which is used as the reaction solvent for the next time. The obtained product is as shown in formula (Ⅱ) (R3 is methyl). Example

[0040] Preparation method of an intramolecular hydrophilic hindered amine

[0041] Add 36.36 parts of polyethylene glycol (Mn = 400) and 30.91 parts of pentamethylpiperidinol to a 1L reaction kettle, heat up to 120 °C, evacuate for 30 min, cool down to 50 °C, add 30.55 parts of hexamethylene diisocyanate, 0.02 parts of dibutyltin dilaurate, and 2.16 parts of acetone to the system. After stirring evenly, introduce nitrogen into the reaction kettle, slowly heat up to 70 - 75 °C, and after reacting for 2 h, start to detect the NCO content. When the NCO content reaches about 0.05 - 0.1%, cool down to terminate the reaction. When the system temperature drops to 50 °C, stop nitrogen and evacuate to remove acetone in the system. The acetone is recovered through a condensing device and used as the reaction solvent for the next time. The obtained product is as shown in formula (Ⅱ) (R2 is H, R3 is methyl).

[0042] Hydrophilicity test: Take 100 g of the hindered amines obtained in Examples 1, 2, and 3 respectively, and under stirring conditions, add 100 g of deionized water respectively. After high-speed stirring for 10 min, let it stand for 2 h, observe the state and conduct a centrifugation test (3000 r / min, 30 min). The results are shown in Table 1 below:

[0043] Table 1

[0044] Name Appearance Centrifugation test results Example 1 Translucent emulsion No delamination Example 2 Translucent emulsion No delamination Example 3 White blue-emitting emulsion No delamination

[0045] The hindered amine light stabilizer is added to a water-based two-component polyurethane varnish in an amount of 0.8wt% by weight, mixed evenly, and then coated on a surface-treated tinplate (according to the national standard GB / T 9721 "Standard Plate Preparation for Paints and Varnishes"), and cured at room temperature until completely dry. The thickness of the dry film is measured to be about 25 to 35μm. According to the American standard ASTM 154, the prepared samples A (blank), B (adding HALS-292) and C (adding the hindered amine of the present invention) are respectively placed in a UV aging test box to perform an accelerated aging experiment.

[0046] Accelerated aging device and conditions: using the American ATLAS UV light box, UVA-340, irradiation intensity 0.89W / (m2•nm), blackboard temperature (light) 60±3℃, blackboard temperature (darkness) 50±3℃, light 8h + condensation 4h, test 168h, the test results are shown in Table 2 below:

[0047] Table 2

[0048] Name ΔL Δa Δb ΔE A -0.71 -0.29 0.53 0.93 B -0.47 -0.24 0.44 0.69 C -0.58 -0.21 0.22 0.65

[0049] The intramolecular hydrophilic hindered amine prepared by the method of the above embodiment has good anti-aging performance and is suitable for water-based systems such as water-based coatings. By changing the isocyanate and piperidinol, hydrophilic hindered amines with different molecular structures can be obtained. The isocyanate can be IPDI, HMDI, MDI, etc., R2 can be H, methyl, and R3 can be methyl, methoxy, ethoxy, octyloxy, cyclohexyloxy, etc.

[0050] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A preparation method of an intramolecular hydrophilic hindered amine for waterborne coatings, characterized in that, Introduce a hydrophilic segment into the molecule to make the synthesized hindered amine hydrophilic. Its general structural formula is as follows: ， Among them, R1 is any one of tolyl, diphenylmethane group, isophorone group, dicyclohexylmethane group, hexamethylene, phenyl, and m-xylene; R2 is hydrogen; R3 is any one of C1-C8 alkyl or alkoxy groups.

2. The preparation method of the intramolecular hydrophilic hindered amine for waterborne coatings according to claim 1, characterized in that, The preparation method includes the following steps: Step (1): Add 30-60 parts of polyether diol to the reaction kettle. The vacuum dehydration temperature is 100-120 °C. After 30 minutes, cool down to 50 °C. Step (2): Slowly add 15-35 parts of diisocyanate, 2-10 parts of solvent, and 0.01-0.1 part of organometallic catalyst to the reaction kettle according to n(isocyanate):n(polyether diol)=2-3:

1. After stirring evenly, under nitrogen protection, heat up to 50-100 °C and react for 0.5-1 h. Then detect the NCO content. When the residual NCO content reaches the theoretical value, the intermediate shown in formula (Ⅰ) is prepared. The intermediate shown in (Ⅰ) is a polyether-modified diisocyanate. The reaction process is as follows: ； Step (3): Add 15 - 35 parts of the intermediate shown in formula (I) and piperidinol according to n residual NCO: n piperidinol = 1.05:1, react at a temperature of 50 - 100 °C for 2 - 4 h under nitrogen protection to obtain the intramolecular hydrophilic hindered amine shown in formula (II). The structural formula of piperidinol is , and the reaction process is as follows: 。 3. The preparation method of the intramolecular hydrophilic hindered amine for waterborne coatings according to claim 2, characterized in that: The polyether diol is polyethylene glycol with an average molecular weight of 400-3000.

4. The preparation method of the intramolecular hydrophilic hindered amine for waterborne coatings according to claim 2, wherein: The diisocyanate described in step (2) includes any one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and m-xylene diisocyanate (XDI).

5. The preparation method of the intramolecular hydrophilic hindered amine for waterborne coatings according to claim 2, characterized in that: The organometallic catalyst described in step (2) includes any one or more of organotin, organozinc, and organobismuth; the organotin includes any one or more of dimethyltin dilaurate, dibutyltin dilaurate, dioctyltin dilaurate, dimethyltin dioleate, dibutyltin dioleate, dioctyltin dioleate, dimethyltin bis(2-ethylhexylthioacetate), dibutyltin bis(2-ethylhexylthioacetate), dioctyltin bis(2-ethylhexylthioacetate), dimethyltin dioctanoate, dibutyltin dioctanoate, dioctyltin dioctanoate, dimethyltin diacetate, dibutyltin diacetate, dioctyltin diacetate, dimethyltin bis(dodecylthio), dibutyltin bis(dodecylthio), dioctyltin bis(dodecylthio), dimethyltin oxide, dioctyltin oxide, dimethyltin maleate, dibutyltin maleate, dioctyltin maleate, stannous octoate, stannous oxalate, and dibutyltin bis(acetylacetonate); the organozinc includes any one or more of zinc neodecanoate and zinc naphthenate; the organobismuth is bismuth isooctanoate.

6. The preparation method of the intramolecular hydrophilic hindered amine for waterborne coatings according to claim 2, characterized in that, The dosage of the catalyst described in step (2) is 0.01-0.1% of the total mass of the reactants, and the organometallic catalyst added in step (2) also plays a catalytic role in the reaction of step (3).

7. The preparation method of the intramolecular hydrophilic hindered amine for waterborne coatings according to claim 2, characterized in that, In step (2), the molar ratio of the isocyanate to the polyether diol is 2-3:1, and the solvent includes any one of ethyl acetate, acetone, and methyl ethyl ketone.

8. The preparation method of the intramolecular hydrophilic hindered amine for waterborne coatings according to claim 2, characterized in that: The method for detecting the NCO content described in step (2) is the dibutylamine method.

9. The preparation method of the intramolecular hydrophilic hindered amine for waterborne coatings according to claim 2, characterized in that: The piperidinol described in step (3) is any one of N-alkyl-2,2,6,6-tetramethylpiperidinol or N-alkoxy-2,2,6,6-tetramethylpiperidinol.

10. The preparation method of the intramolecular hydrophilic hindered amine for waterborne coatings according to claim 2, characterized in that: The intramolecular hydrophilic hindered amine prepared by the preparation method is an oligomer with a certain molecular weight distribution, not a single compound. The oligomer contains urea bonds, hydroxyl groups and trace amounts of unreacted piperidinol monomers.

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