Anti-yellowing agent as well as preparation method and application thereof

Abstract

The invention discloses an anti-yellowing agent as well as a preparation method and application thereof, the anti-yellowing agent is prepared by compounding the following raw materials: aryl sulfonic acid and alkanolamide in a molar ratio of 1: (0.9-1.0), the aryl sulfonic acid is cardanol sulfonic acid, the alkanolamide is alkanolamide in a molar ratio of 1: (0.9-1.0), and the alkanolamide is alkanolamide in a molar ratio of 1: (0.9-1.0). The anacardol sulfonic acid in the anti-yellowing agent and the hindered phenol antioxidant generate intermolecular association, so that the activity of a yellow nitro compound formed by the hindered phenol antioxidant and nitrogen oxide is reduced, the effect of preventing yellowing is achieved, and stable color and performance can be kept; the cardanol sulfonic acid not only provides water solubility of sulfonic acid groups, but also has resin compatibility of long-chain alkyl groups, and is completely suitable for a water-borne epoxy resin coating system.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and particularly relates to an anti-yellowing agent and its preparation method and application. Background Art

[0002] Due to its low VOC, non-toxic and environmentally friendly characteristics, the application of waterborne epoxy resin coatings has rapidly expanded in the fields of construction, automobiles, furniture, etc. However, its yellowing problem remains the core bottleneck restricting its high-end application. The waterborne system of waterborne epoxy resin coatings is relatively special, and some anti-yellowing auxiliary components are difficult to be well compatible with it. For example, some amine antioxidants in waterborne epoxy resin coatings are prone to react with moisture or other additives in the system, not only reducing the anti-yellowing effect, but also possibly affecting the storage stability of the coatings, resulting in phenomena such as stratification and precipitation during storage, seriously affecting the product quality and use performance.

[0003] At present, there is less attention and solutions to this problem. The research on waterborne epoxy resin coatings mainly focuses on the research of anti-corrosion performance. For example, the Chinese patent documents of CN119242129A and CN119161783A. There are also a few, such as CN119144206A, which focus on the technical problem of thermal oxidation resistance. By using high-temperature resistant inorganic rare earths and their compositions, and utilizing the characteristics of rare earth 4f orbitals, the quenching of free radicals generated during the epoxy thermal oxidation aging process is realized, so as to achieve the purpose of enhancing the thermal oxidation resistance of waterborne epoxy resin. However, it uses nano-scale rare earth oxides, which have a high cost, and when nano-ceria is added to waterborne epoxy resin, the nano-particles are prone to agglomeration and it is difficult to be uniformly dispersed in the matrix. Therefore, there is still a need for improvement.

[0004] Therefore, in order to promote the large-scale application of anti-yellowing agents, it is necessary to develop an anti-yellowing agent applied to waterborne epoxy resin coatings. Summary of the Invention

[0005] The main object of the present invention is to provide an anti-yellowing agent and its preparation method and application, aiming to solve the problem that the anti-yellowing agent added in the existing waterborne epoxy resin coatings is difficult to be compatible, resulting in the yellowing of the coatings.

[0006] To achieve the above object, in the first aspect of the present invention, an anti-yellowing agent is proposed, which is compounded from the following raw materials: aryl sulfonic acid and alkanolamide with a molar ratio of 1:0.9 - 1.0, wherein the aryl sulfonic acid is cardanol sulfonic acid.

[0007] Further, it is compounded from the following raw materials by weight: 383 parts of aryl sulfonic acid and 287 parts of alkanolamide.

[0008] Further, the alkanolamide is a straight-chain alkanolamide.

[0009] Further, the alkanolamide is model 6502 of Guangzhou Jieshun Chemical Co., Ltd.

[0010] On the other hand, the present invention provides a method for preparing an anti-yellowing agent, comprising the following steps:

[0011] S1: Sulfonate cardanol, acetic anhydride, and concentrated sulfuric acid to obtain cardanol sulfonic acid;

[0012] S2: Start the refrigeration system, add water, and control the temperature below 40°C;

[0013] S3: Cool down to 10°C, then add alkanolamide, and control the temperature below 40°C;

[0014] S4: Stop refrigeration, add methanol and stabilizer, dissolve and filter to obtain the anti-yellowing agent.

[0015] Further, the steps of S1 include adding cardanol and acetic anhydride into the reaction kettle, starting stirring, introducing nitrogen, starting the refrigeration system, cooling down to 0 - 5°C, dropwise adding concentrated sulfuric acid, controlling the temperature below 5°C, and keeping warm to obtain cardanol sulfonic acid.

[0016] Further, the mass ratio of the added cardanol, acetic anhydride, concentrated sulfuric acid, water, and alkanolamide is 270 - 330:20 - 40:90 - 110:630 - 770:258 - 315.

[0017] Further, the stabilizer is adipic dihydrazide.

[0018] The present invention also provides an application of the anti-yellowing agent in waterborne epoxy resin, and the anti-yellowing agent accounts for 1.5 - 3.5 wt% of the waterborne epoxy resin.

[0019] Beneficial effects:

[0020] An anti-yellowing agent, its preparation method and application of the present invention. The anti-yellowing agent is compounded by aryl sulfonic acid and alkanolamide, and belongs to the hindered phenol type anti-phenol yellowing agent. It can scavenge the residual phenolic free radicals in epoxy resin, so as to achieve the effect of blocking phenol antioxidant and preventing yellowing; and the aryl sulfonic acid is selected as cardanol sulfonic acid. Cardanol sulfonic acid forms intermolecular association with the external hindered phenol type antioxidant, reducing the activity of the hindered phenol type antioxidant to form yellow nitro compounds with nitrogen oxides, achieving the effect of preventing yellowing, and cardanol sulfonic acid not only provides the water solubility of sulfonic acid group, but also has the resin compatibility of long-chain alkyl, and is completely applicable to the waterborne epoxy resin coating system.

[0021] The alkanolamide of the present invention is a basic amide surfactant, which is used to neutralize the strong acidity of cardanol sulfonic acid to make its pH value within a suitable range, having anti-corrosion and good emulsifying and wetting properties. When added to the waterborne epoxy resin coating, it improves the storage stability, film leveling property and adhesion to the substrate of the coating. Description of the Drawings

[0022] Figure 1 The anti-yellowing agent prepared in Example 1 of the present invention (left) and the sample prepared in Comparative Example 1 (right);

[0023] Figure 2 The test result diagram of the phenolic yellowing resistance performance of the anti-yellowing agent prepared in Example 1 of the present invention;

[0024] Figure 3 The test result diagram of the phenolic yellowing resistance performance of the anti-yellowing agent prepared in Example 2 of the present invention;

[0025] Figure 4 The test result diagram of the phenolic yellowing resistance performance of the anti-yellowing agent prepared in Example 3 of the present invention;

[0026] Figure 5 The test result diagram of the phenolic yellowing resistance performance of the sample prepared in Comparative Example 1 of the present invention;

[0027] Figure 6 The test result diagram of the phenolic yellowing resistance performance of the sample prepared in Comparative Example 2 of the present invention;

[0028] Figure 7 The test result diagram of the phenolic yellowing resistance performance of the sample prepared in Comparative Example 3 of the present invention.

[0029] The realization, functional characteristics and advantages of the object of the present invention will be further described in conjunction with the embodiments and with reference to the drawings. Detailed Embodiments

[0030] In the following examples of the present invention, the experimental methods without specific conditions are usually carried out according to conventional conditions or according to the conditions recommended by the manufacturers. All kinds of common chemical reagents used in the examples are commercially available products.

[0031] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0032] As used in this invention, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product or device that includes a series of steps is not limited to the listed steps or modules, but may optionally further include steps not listed, or may optionally further include other steps inherent to these processes, methods, products or devices.

[0033] To make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0034] The following examples further describe the present invention, but these examples are not intended to limit the protection scope of the present invention.

[0035] An embodiment of the present invention provides an anti-yellowing agent, which is composed of the following raw materials by weight: arylsulfonic acid and alkanolamide with a molar ratio of 1:0.9 to 1.0, wherein the arylsulfonic acid is cardanol sulfonic acid.

[0036] In the above embodiment, by introducing an anti-yellowing agent prepared by compounding arylsulfonic acid and alkanolamide, this anti-yellowing agent belongs to the hindered phenol type anti-phenol yellowing agent, which can scavenge the residual phenolic free radicals in epoxy resin, thereby achieving the effect of blocking phenolic antioxidant and preventing yellowing, and maintaining stable color and performance.

[0037] The general structural formula of arylsulfonic acid is Ar-SO3H, where Ar represents an aryl group; the aryl group can be a monocyclic aromatic hydrocarbon group or a polycyclic aromatic hydrocarbon group. Arylsulfonic acid has acidity and can adjust the acidity and alkalinity of the environment in the system. Maintaining a suitable acidic environment helps to inhibit chemical reactions that may cause yellowing; moreover, the sulfonic acid group (-SO3H) in arylsulfonic acid has certain reaction activity and can chemically combine or react with the chromophore, thereby delaying the generation of yellowing structures.

[0038] Cardanol sulfonic acid is selected as the arylsulfonic acid. Cardanol sulfonic acid forms intermolecular association with the hindered phenol type antioxidant, reducing the activity of the hindered phenol type antioxidant to form yellow nitro compounds with nitrogen oxides, achieving the effect of preventing yellowing. Moreover, cardanol sulfonic acid not only provides the water solubility of the sulfonic acid group but also has the resin compatibility of the long-chain alkyl group, and is completely applicable to the waterborne epoxy resin coating system.

[0039] It can be understood that linear alkylbenzene sulfonic acid can also have an anti-yellowing effect in the waterborne epoxy resin system, but this raw material is difficult to biodegrade and belongs to water pollution substances, and its use is restricted.

[0040] Alkanolamide is a kind of basic amide surfactant, which is used to neutralize the strong acidity of cardanol sulfonic acid, make its pH value within a suitable range, and has anti-corrosion and good emulsifying and wetting properties. When added to waterborne epoxy resin coatings, it improves the storage stability, film leveling property and adhesion to the substrate of the coatings.

[0041] Experiments have proved that the molar ratio of aryl sulfonic acid to alkanolamide is more suitable in the range close to 1:0.90 - 1.00. Too much or too little alkanolamide will lead to a decrease in the anti-yellowing effect.

[0042] Preferably, it is compounded from the following raw materials by weight: 383 parts of aryl sulfonic acid and 287 parts of alkanolamide.

[0043] Preferably, the alkanolamide is a straight-chain alkanolamide. The straight-chain alkanolamide is a product formed by the reaction of a straight-chain alkanol with a compound related to the amide group. The straight-chain alkanolamide can capture free radicals, inhibit the progress of the oxidation chain reaction, and convert free radicals into relatively stable products. The straight-chain structure makes the molecule have better linearity and extensibility, and is more likely to interpenetrate and entangle with polymer segments, thus showing better synergistic performance. Preferably, the anti-yellowing agent is compounded from aryl sulfonic acid and straight-chain alkanolamide. When compounded with aryl sulfonic acid, it can interact to form a physical barrier, reduce the damage of external factors to the internal structure, and further maintain the stability of the color. For example, the alkanolamide 6502 used in the examples is a straight-chain alkanolamide.

[0044] On the other hand, the present invention provides a preparation method of an anti-yellowing agent for the anti-yellowing agent described in any of the above embodiments, including the following steps:

[0045] S1: Carry out a sulfonation reaction on cardanol, acetic anhydride and concentrated sulfuric acid to obtain cardanol sulfonic acid;

[0046] S2: Turn on the refrigeration system, add water, and control the temperature below 40 °C;

[0047] S3: Cool down to 10 °C, then add alkanolamide, and control the temperature below 40 °C;

[0048] S4: Stop refrigeration, add methanol and a stabilizer, dissolve and filter to obtain the anti-yellowing agent.

[0049] In the above embodiment, the reaction equation of the sulfonation reaction is as follows:

[0050]

[0051] In one embodiment, the stabilizer is adipic dihydrazide. Adipic dihydrazide can form a colorless compound with nitrogen oxides under high temperature conditions, and has a good anti-yellowing effect at high temperature.

[0052] The present invention also provides an application of the anti-yellowing agent described in any of the above embodiments in a waterborne epoxy resin coating, wherein the anti-yellowing agent accounts for 1.5 to 3.5 wt% of the waterborne epoxy resin.

[0053] The specific embodiments are as follows:

[0054] In the following examples and comparative examples, all raw materials used in the experiments are commercially available. For the specific purchasing manufacturers, please refer to Table 1.

[0055] Table 1. Raw material purchasing manufacturers

[0056]

[0057]

[0058] Example 1

[0059] S1: Add 302 parts of cardanol, 30 parts of acetic anhydride into a clean reaction kettle, start stirring, introduce nitrogen, displace oxygen for 15 minutes, start the refrigeration system, cool down to 0 - 5 °C, start dropping 100 parts of concentrated sulfuric acid, control the dropping rate, keep the temperature below 5 °C, after dropping, keep warm for about 5 hours to obtain cardanol sulfonic acid.

[0060] S2: Continue to start the refrigeration system, slowly add 700 parts of deionized water, and keep the temperature below 40 °C during this period.

[0061] S3: Cool down to 10 °C, slowly add 287 parts of alkanolamide 6502, and keep the temperature below 40 °C during this period.

[0062] S4: Stop refrigeration, add 100 parts of methanol and 35 parts of stabilizer adipic dihydrazide, stir until completely dissolved, and filter and discharge.

[0063] Example 2

[0064] S1: Add 302 parts of cardanol, 40 parts of acetic anhydride into a clean reaction kettle, start stirring, introduce nitrogen, displace oxygen for 15 minutes, start the refrigeration system, cool down to 0 - 5 °C, start dropping 100 parts of concentrated sulfuric acid, control the dropping rate, keep the temperature below 5 °C, after dropping, keep warm for about 5 hours to obtain cardanol sulfonic acid.

[0065] S2: Continue to start the refrigeration system, slowly add 700 parts of deionized water, and keep the temperature below 40 °C during this period.

[0066] S3: Cool down to 10 °C, slowly add 315 parts of alkanolamide 6502, and keep the temperature below 40 °C during this period.

[0067] S4: Stop refrigeration, add 100 parts of methanol and 35 parts of stabilizer adipic dihydrazide, stir until completely dissolved, and filter and discharge.

[0068] Example 3

[0069] S1: Add 302 parts of cardanol, 30 parts of acetic anhydride into a clean reactor. Start stirring, introduce nitrogen to displace oxygen for 15 minutes. Then start the refrigeration system and cool down to 0 - 5°C. Begin to dropwise add 110 parts of concentrated sulfuric acid, control the dropping rate to keep the temperature below 5°C. After the dropping is completed, keep the temperature for about 5 hours to obtain cardanol sulfonic acid.

[0070] S2: Continue to start the refrigeration system and slowly add 700 parts of deionized water, keeping the temperature below 40°C during this period.

[0071] S3: Cool down to 10°C and slowly add 287 parts of alkanolamide 6502, keeping the temperature below 40°C during this period.

[0072] S4: Stop refrigeration, add 100 parts of methanol and 35 parts of stabilizer adipic dihydrazide, stir until completely dissolved, and then filter and discharge.

[0073] Comparative Example 1

[0074] The difference between this comparative example and Example 1 is only that: the alkanolamide in the formula is adjusted to fatty amine polyoxyethylene ether, and other components and preparation methods are the same as those in Example 1.

[0075] Comparative Example 2

[0076] The difference between this comparative example and Example 1 is only that: the cardanol sulfonic acid in the formula is adjusted to commercially available p-toluenesulfonic acid, and other components and preparation methods are the same as those in Example 1.

[0077] Comparative Example 3

[0078] The difference between this comparative example and Example 1 is only that: the alkanolamide in the formula is changed to stearamide, and other components and preparation methods are the same as those in Example 1.

[0079] I. Appearance Test

[0080] Refer to the appendix Figure 1 , which are respectively the appearances of the anti-yellowing agent prepared in Example 1 of the present invention and the sample prepared in Comparative Example 1. It can be seen that the appearance of the anti-yellowing agent of the present invention is clear and transparent, close to colorless, and does not affect the color when placed in waterborne epoxy resin; while replacing the alkanolamide with other surfactants results in the obtained anti-yellowing agent sample being orange-yellow. It is speculated that fatty amine polyoxyethylene ether cannot replace alkanolamide to react with aryl sulfonic acid and is easily affected by color.

[0081] II. Phenol Yellowing Resistance Performance Test

[0082] The anti-yellowing agents prepared in the above Examples 1 to 3 and the samples prepared in Comparative Examples 1 to 3 were respectively added to the self-made waterborne epoxy resin coating for anti-yellowing testing. Among them, the formula of the self-made waterborne epoxy resin coating is epoxy resin (E-44 35wt%, E-51 10wt%), diluent (propylene glycol monobutyl ether) 5wt%, reactive emulsifier (phosphate surfactant 6wt%, sulfate surfactant 2wt%), wetting agent (polysiloxane) 1wt%, antioxidant (benzotriazole) 0.5wt%, defoamer (mineral oil) 0.5wt%, pH regulator (dimethyl ethanolamine) 0.5wt%, antibacterial agent (isothiazolinone) 0.3wt%, thickener (nonionic polyurethane) 0.5wt%, deionized water 36.2wt% and the anti-yellowing agent in the present invention.

[0083] The test was carried out according to the following steps:

[0084] S1: Take the desized and scoured polyester shuttle fabric and dip-roll the above waterborne epoxy resin coating respectively;

[0085] S2: Dry in a hot air dryer at 130°C for 2 minutes;

[0086] S3: The treated fabric was tested for anti-yellowing performance according to the evaluation method of potential phenolic yellowing in the national recommended standard GB / T 29778-2013.

[0087] III. Storage stability test

[0088] The storage stability was tested according to 6.4.5 in GB / T 23999 Waterborne wood coatings for interior decoration and fitment.

[0089] IV. Compatibility test

[0090] Add 2.5% of the anti-yellowing agent to the waterborne epoxy coating, and then investigate according to the storage stability test method in 6.4.5 of GB / T 23999.

[0091] The test results of the above Tests II to IV are shown in Table 2 and Appendix Figures 2 to 7 。

[0092] Table 2. Test data

[0093]

[0094]

[0095] It should be noted that the anti-yellowing agent of the present invention has universality and also has the anti-yellowing function in other waterborne epoxy resin coatings.

[0096] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A yellowing inhibitor, characterized in that, It is compounded from the following raw materials: aryl sulfonic acid and alkanolamide with a molar ratio of 1:0.9 - 1.0, wherein the aryl sulfonic acid is cardanol sulfonic acid.

2. The anti-yellowing agent according to claim 1, characterized in that, It is compounded from the following raw materials by weight: 383 parts of aryl sulfonic acid and 287 parts of alkanolamide.

3. The anti-yellowing agent according to claim 1 or 2, characterized in that, The alkanolamide is a straight-chain alkanolamide, and / or the model of the alkanolamide is 6502 of Guangzhou Jieshun Chemical Co., Ltd.

4. A method for preparing the anti-yellowing agent according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1: Sulfonate cardanol, acetic anhydride, and concentrated sulfuric acid to obtain cardanol sulfonic acid. S2: Start the refrigeration system, add water, and control the temperature below 40°C. S3: Cool down to 10°C, then add alkanolamide, and control the temperature below 40°C. S4: Stop refrigeration, add methanol and stabilizer, dissolve and filter to obtain the anti-yellowing agent.

5. The preparation method of the anti-yellowing agent according to claim 4, wherein The steps of S1 include adding cardanol and acetic anhydride into the reaction kettle, starting stirring, introducing nitrogen, starting the refrigeration system, cooling down to 0 - 5°C, dropping concentrated sulfuric acid, controlling the temperature below 5°C, and holding the temperature to obtain cardanol sulfonic acid.

6. The preparation method of the anti-yellowing agent according to claim 4, characterized in that, The mass ratio of the added cardanol, acetic anhydride, concentrated sulfuric acid, water, and alkanolamide is 270 - 330:20 - 40:90 - 110:630 - 770:258 - 315.

7. The preparation method of the anti-yellowing agent according to claim 4, characterized in that, The stabilizer is adipic dihydrazide.

8. Application of an anti-yellowing agent as described in any one of claims 1 - 3 in waterborne epoxy resin, wherein the anti-yellowing agent accounts for 1.5 - 3.5 wt% of the waterborne epoxy resin.

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