A nylon anti-phenolic yellowing agent and a preparation method thereof

Abstract

The application discloses a nylon anti-phenol yellowing agent and a preparation method thereof. The molecular structure of the nylon anti-phenol yellowing agent is a maleic anhydride derivative main chain as a core skeleton, a hydrophobic end formed by connecting a full-saturated long-chain alkyl group to one end through an ester bond, and a taurine structural unit connected to the other end through a hydrolysis-resistant amide bond. A secondary sulfonic acid group derived from a sodium metabisulfite addition reaction is embedded on the maleic anhydride derivative main chain, and an end group sulfonic acid group is arranged at the end of the taurine unit. The main advantages of the application are as follows: 1. high anti-phenol yellowing efficiency, a three-dimensional barrier is constructed by using the steric hindrance of the secondary sulfonic acid group, and the end amino group is closed by a double anion group, so that good anti-phenol yellowing effect is achieved; 2. good hand feeling, the full-saturated skeleton prevents self-yellowing at high temperatures, and the long-chain alkyl group gives the fabric a fluffy and soft touch; and 3. strong process compatibility, the product has low foam and high penetration, is suitable for high-speed cleaning production, and meets ecological standards.

Description

Technical Field

[0001] This invention relates to the field of textile chemicals technology, specifically to a finishing agent for preventing phenolic yellowing of nylon fabrics and its preparation method, and more particularly to a composite structure anti-phenolic yellowing agent based on secondary sulfonic acid groups and terminal sulfonic acid groups. Background Technology

[0002] Nylon (Nylon 6 / Nylon 66) fibers are widely used in high-end sportswear, underwear, hosiery, and light-colored or fluorescent whitening fabrics due to their excellent abrasion resistance, resilience, and soft touch. However, white or light-colored nylon fabrics are highly susceptible to phenolic yellowing during storage and transportation: hindered phenolic antioxidants such as di-tert-butyl-p-cresol (BHT) added to packaging materials (e.g., polyethylene film, cartons) migrate to the fabric surface in the storage environment and react with nitrogen oxides (NOx) in the atmosphere. x The reaction produces a yellow nitrophenol derivative (DTNP, 2,6-di-tert-butyl-4-nitrophenol); DTNP dissociates under alkaline conditions into a yellow phenoxy anion, which readily binds to the protonated amino groups (–NH3) at the ends of nylon fibers via ion-pair interactions and hydrogen bonds. + The yellowing of the fabric is caused by the combination and enrichment of exposed amide groups (-CONH-) with some exposed amide groups on the fiber surface.

[0003] To alleviate the aforementioned problems, the industry commonly employs a process of applying anti-phenolic yellowing agents (phenolic yellowing inhibitors) to nylon fabrics during the finishing stage. Currently, mainstream anti-phenolic yellowing finishing technologies primarily utilize linear or short-branched primary alkyl sulfate / sulfonic acid derivatives such as sodium dodecylbenzenesulfonate, sodium dodecylbenzene ether sulfate, or sodium isooctyl sulfate as core active ingredients. These agents ionize under weakly acidic conditions (pH 4–6) to release anions (-SO32-). - -OSO3 - ) and the protonated amino groups (–NH3) at the ends of nylon fibers + Ion adsorption occurs, attempting to block the terminal amino active sites to inhibit the adsorption and color development of DTNP. Examples include the anti-phenolic yellowing finishing agent based on sodium dodecylbenzene ether sulfate disclosed in Chinese patent document CN 111733599 A, the weakly acidic anti-phenolic yellowing agent based on sodium isooctanol sulfate disclosed in Chinese patent document CN 111663331 A, and the anti-yellowing agent prepared by combining alkylbenzene sulfonic acid with ethanolamine disclosed in Chinese patent document CN 103194892 B, etc.

[0004] However, such existing technical solutions often have one or more inherent technical and application defects, including: In some technical solutions, the sulfonate or sulfate groups in the primary alkyl sulfate / sulfonic acid derivatives are usually attached to the primary carbon atom (-CH2-SO3H) or the terminal oxygen atom (-O-SO3H), resulting in extremely small steric hindrance. They can only form a planar and loose ion adsorption layer on the fiber surface, which cannot form an effective steric barrier for DTNP molecules. DTNP can still penetrate through the intermolecular gaps and adsorb onto the terminal amino and amide group regions. The terminal amino sealing efficiency is limited, and it is difficult to stably achieve the specified high-level anti-phenolic yellowing standard. The accuracy is questionable; some technical solutions often contain easily oxidized groups or ester bonds with poor thermal stability in the molecular skeleton of the auxiliary agents. Under the high-temperature setting process (180-210℃) that nylon fabrics must go through, they are prone to oxidation or thermal decomposition. This not only causes them to lose their anti-yellowing function, but the auxiliary agents themselves will also produce chromophores, leading to "auxiliary self-yellowing", which seriously restricts the quality of high whiteness and whitening products. In addition, traditional anionic anti-phenolic yellowing agents have a high critical micelle concentration (CMC), insufficient dynamic wettability and rich foam. On modern continuous printing and dyeing equipment with high speed and low liquor ratio, they are prone to foam-carrying defects, affecting processing stability and clean production requirements.

[0005] Therefore, there is an urgent need in the market to develop a specially designed molecular structure to overcome the shortcomings of the existing technologies and meet the comprehensive requirements of high-end light-colored and whitening nylon products for storage resistance to yellowing, heat stability and processing adaptability. Summary of the Invention

[0006] To address the problems of insufficient anti-phenolic yellowing ability, poor heat resistance, weak auxiliary agent penetration, and high CMC affecting processing stability in existing nylon anti-phenolic yellowing agent technologies, this invention proposes a novel nylon anti-phenolic yellowing agent and its preparation method. The nylon anti-phenolic yellowing agent of this invention uses conventional environmentally friendly raw materials such as maleic anhydride, taurine, and alkyl alcohols. It requires no high-temperature and high-pressure processing and can be produced using conventional production equipment, yielding a product with strong anti-phenolic yellowing ability, excellent heat resistance, superior auxiliary agent penetration, and a good hand feel after finishing.

[0007] The first aspect of this invention provides a nylon anti-phenol yellowing agent, wherein the molecular structure of the nylon anti-phenol yellowing agent is based on a maleic anhydride-derived backbone, with one end connected to a fully saturated long-chain alkyl group via an ester bond (-COO-) to form a hydrophobic end, and the other end connected to a taurine structural unit via a hydrolysis-resistant amide bond (-NR1-CO-); the maleic anhydride-derived backbone is embedded with a secondary sulfonic acid group (-CH(SO3H)-) derived from the addition reaction of sodium metabisulfite, and the taurine unit has a terminal sulfonic acid group (-SO3H) at its end. The molecular structural formula of the nylon anti-phenol yellowing agent is as follows: , R1 is selected from either H or CH3, and R2 is selected from C6-C. 30 At least one of straight-chain alkyl, branched alkyl, and cycloalkyl.

[0008] In some implementations, R2 is selected from C6-C. 30 Two or more of the following: straight-chain alkyl groups and branched-chain alkyl groups. In this case, the nylon anti-phenol yellowing agent is a mixture comprising two or more components with the above-described molecular structures, and the different components have different types of R2 in their molecular structures.

[0009] A second aspect of the present invention provides a method for preparing the above-mentioned nylon anti-phenol yellowing agent, comprising the following steps: Step 1 Maleic anhydride-taurine amidation: Under a dry, non-reactive protective gas atmosphere, maleic anhydride is added to the reaction apparatus and heated to 55-65°C to melt and dissolve the maleic anhydride. Taurine is added, stirred evenly, and kept at 55-65°C for 1-2 hours to carry out a ring-opening amidation reaction, yielding maleic anhydride-taurine amidate. The non-reactive protective gas is typically nitrogen. The reaction apparatus is typically a reaction vessel. The reaction time is to ensure a complete reaction and minimize side reactions that cause the system to darken in color. Step 2: Alcohol Esterification and Dehydration Condensation: In the maleic anhydride-taurine amide compound from Step 1 above, a catalyst is added, and an alkyl alcohol is added dropwise. The mixture is heated to 135–145°C under a non-reactive protective gas atmosphere, continuously separating the water generated during the reaction. The reaction is carried out for 5–8 hours to obtain the alcohol esterification and dehydration condensate. The non-reactive protective gas is typically nitrogen. The reaction time is to ensure a complete reaction and minimize side reactions that cause the system to darken in color. Step 3: Addition of sodium metabisulfite: The alcohol esterification and dehydration condensate from Step 2 is cooled to 50–60°C. Then, a sodium metabisulfite solution with a concentration of 19.5–20.5 wt% is added to the obtained alcohol esterification and dehydration condensate. The reaction is carried out for 3–6 hours to obtain the nylon anti-phenol yellowing agent. The reaction time is to ensure a complete reaction and minimize side reactions that cause the system to darken in color. The concentration of the sodium metabisulfite solution is also to ensure the reaction rate and suppress side reactions; a concentration below this range results in a slow reaction rate, while a concentration above this range can easily lead to localized overconcentration and increased side reactions.

[0010] In a preferred embodiment, during the preparation of the nylon anti-phenol yellowing agent, the reactants, maleic anhydride, taurine, catalyst, alkyl alcohol, and sodium metabisulfite are used in a molar equivalent ratio of 1:1:0.03-0.07:0.9-1:1-1.2.

[0011] The alkyl alcohol is selected from at least one of C6-C30 alkyl alcohols, wherein the C6-C30 alkyl alcohol contains a long-chain alkyl group, and the long-chain alkyl group is structurally a straight-chain alkyl group or a branched-chain alkyl group, preferably at least one of C8-C14 alkyl alcohols, and more preferably one of C12 lauryl alcohol, C8 / C10 mixed alcohol, and C12 / C14 mixed alcohol.

[0012] The taurine mentioned above can also be replaced by methyl taurine, or by a mixture of taurine and methyl taurine.

[0013] The catalyst is selected from at least one of p-toluenesulfonic acid, aminosulfonic acid, methanesulfonic acid, and camphorsulfonic acid.

[0014] Preferably, the basis for determining the end of the sodium metabisulfite addition process in Step 3 can be the result of iodine value monitoring to determine the reaction endpoint. Specifically, during the reaction, iodine value is measured at fixed intervals (e.g., every 20 minutes). When the iodine value is consistently reduced to below 0.5 g I2 / 100g in 2-3 consecutive measurements, and the difference between two adjacent measurements does not exceed 0.05 g I2 / 100g, it means that the value no longer decreases significantly, and the reaction endpoint is reached. The reaction is then terminated (i.e., the endpoint is when the iodine value approaches 0 and no longer decreases).

[0015] The nylon anti-phenolic yellowing agent provided by this invention has a molecular structure with a maleic anhydride-derived backbone as the core framework. One end is connected to a fully saturated long-chain alkyl group via an ester bond (-COO-) to form a hydrophobic end, and the other end is connected to a taurine structural unit via a hydrolysis-resistant amide bond (-NH-CO-). The backbone is embedded with secondary sulfonic acid groups (-CH(SO3H)-) derived from the addition reaction of sodium metabisulfite, and the taurine unit has a terminal sulfonic acid group (-SO3H). When used as a nylon anti-phenolic yellowing agent in the finishing of nylon fabrics, its mechanism of action can be summarized in three dimensions: regulation of the microenvironment on the fiber surface, three-dimensional sealing of active sites, and enhanced adsorption at the molecular interface.

[0016] Normally, the amino group (-NH2) at the end of nylon fibers protonates to –NH3 when the pH is below its pKa value (approximately 4.5–5.0). + This becomes a key factor in phenolic yellowing. During storage and transportation, sterically hindered phenolic antioxidants (such as BHT) in the packaging material migrate to the fiber surface and are then exposed to nitrogen oxides (NOx) in the atmosphere. x It is oxidized to produce 2,6-di-tert-butyl-4-nitrophenol (DTNP). DTNP, as a weakly acidic nitrophenol, readily binds to the –NH3 groups on the fiber surface via ion pairing and hydrogen bonding. + It binds to amide groups (-CONH-); especially under alkaline conditions, DTNP dissociates into yellow phenolic anions (DTNP-), causing severe yellowing of white and light-colored nylon fabrics.

[0017] The nylon anti-phenolic yellowing agent of the present invention can fully ionize the secondary sulfonic acid group and the terminal sulfonic acid group in a weakly acidic application system with pH=4-6, releasing a high density of anionic sulfonate ions (-SO3). - These anionic groups interact with the –NH3 on the fiber surface. + Stable ionic bonds are formed through electrostatic attraction, constructing a dense functional anion adsorption layer on the fiber surface. This achieves targeted blocking of the terminal amino active sites, significantly reducing the binding probability of DTNP. Crucially, the secondary sulfonic acid group configuration in the molecule of this invention generates a significant steric hindrance effect: the sulfonic acid group, attached to the secondary carbon atom, occupies a larger steric space compared to the traditional primary sulfonic acid group (-CH2-SO3H), effectively shielding the terminal amino region and hindering the approach of DTNP molecules. Simultaneously, the long, fully saturated carbon chain in the molecule generates strong van der Waals forces and hydrophobic interactions with the nylon macromolecular chain segments, promoting block spreading of the functional molecule along the fiber axis and amorphous regions. This forms a physical cover over adjacent amide groups and competes with hydrogen bonds for adsorption, indirectly weakening the anchoring ability of DTNP and achieving a synergistic effect of "terminal amino group primary blocking + amide group secondary shielding."

[0018] Furthermore, the unique T-structure of the secondary alkyl sulfate group in the nylon anti-phenolic yellowing agent of this invention combines low critical micelle concentration (CMC) with excellent dynamic wettability, enabling rapid penetration into the yarn core and amorphous region of the fiber. This ensures uniform distribution of the anionic sealing layer and prevents yellowing spots caused by localized leakage. The amide bond and fully saturated carbon chain in the molecule do not possess a conjugated π-electron system, maintaining chemical inertness at heat-setting temperatures of 180–210°C. This prevents the formation of chromophores due to self-oxidation or thermal decomposition, thus simultaneously inhibiting thermo-oxidative yellowing during processing. Moreover, the product's pH value is maintained in a weakly acidic range of 4.5–5.5, ensuring that trace amounts of DTNP generated in the environment exist primarily in molecular form (DTNPH), inhibiting its conversion to dark-colored phenolic anions, and weakening the intensity of yellowing from a chemical equilibrium perspective.

[0019] As can be seen from the above, the present invention achieves a highly efficient and long-lasting anti-phenolic yellowing effect on nylon fabrics throughout the entire process of storage, transportation and processing through a multi-synergistic mechanism of "weak acid color suppression + ionic bond targeted blocking + secondary sulfonic acid group steric hindrance + saturated carbon chain physical shielding + high penetration uniform distribution".

[0020] In the preparation method of the nylon anti-phenol yellowing agent of the present invention, the temperatures of each step are 55-65°C, 135-145°C, and 50-60°C, respectively. High-temperature and high-pressure operation is not required, and general production equipment can handle the task. This is a significant advantage in production.

[0021] Because this invention is based on a unique molecular structure and imparts multiple synergistic mechanisms to fabrics after nylon finishing, the anti-phenolic yellowing agent described herein exhibits the following significant advantages in practical industrial applications: (1) The product has excellent anti-yellowing performance. The unique secondary sulfonic acid group (-CH(SO3H)-) has a significant steric hindrance effect. Compared with traditional primary alkyl sulfuric acid / sulfonic acid derivatives, which can only form a planar adsorption layer, it can build a dense and thick three-dimensional barrier on the fiber surface, physically blocking the penetration and adsorption of DTNP molecules. Combined with the ionic bonding of the bi-anionic group and the terminal amino group, the anti-phenolic yellowing effect is stable and excellent, and the protective performance is far superior to commercially available products with similar conventional uses.

[0022] (2) Nylon fabrics have a good hand feel after finishing. The long-chain saturated alkyl groups introduced into the molecular structure are oriented on the fiber surface to form a flexible hydrophobic lubricating layer, which effectively reduces the coefficient of friction between fibers. While providing long-lasting anti-yellowing protection, it also plays a plasticizing role similar to a softener, giving nylon fabrics a fluffy, soft and delicate touch, overcoming the inherent defects of traditional anti-phenolic yellowing agents that easily lead to fabric hardening and rough hand feel.

[0023] (3) Eliminate the "self-yellowing" problem of the auxiliary agent from the source. The molecular structure of this auxiliary agent does not contain easily self-oxidized aliphatic unsaturated bonds and conjugated double bonds. The alkyl chain is a fully saturated carbon chain, the main skeleton is composed of hydrolysis-resistant amide bonds, and saturated alkyl ester chains are introduced as hydrophobic anchors. Within the high-temperature setting window of 180-210℃, the molecule lacks the structural source of oxidation and color development, and no obvious thermal oxidation or cracking occurs, ensuring a high degree of consistency in the whiteness of the fabric before and after treatment.

[0024] (4) High penetration and low foaming properties, suitable for high-speed and clean production. The unique molecular configuration gives the product excellent dynamic wettability and extremely low critical micelle concentration, which can quickly penetrate into the yarn core and ensure the uniformity of the anti-yellowing effect of the fabric surface; at the same time, the natural low foaming properties are perfectly compatible with modern dyeing and finishing equipment with high speed and low liquor ratio, eliminating fabric defects caused by foam entrainment, which is in line with the trend of clean production.

[0025] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0026] This invention discloses a novel nylon anti-phenolic yellowing agent and its preparation method, addressing the problems of insufficient anti-phenolic yellowing ability, poor heat resistance, weak additive penetration, and rough hand feel of existing products. The preparation method of this novel nylon anti-phenolic yellowing agent includes three steps: maleic anhydride-taurine amidation, alcohol esterification dehydration condensation, and sodium metabisulfite addition, using maleic anhydride, alkyl alcohols, and taurine as raw materials. The main advantages of this invention are: firstly, it has high anti-phenolic yellowing efficiency, utilizing the steric hindrance of the secondary sulfonic acid group to construct a three-dimensional barrier, combined with the blocking of the terminal amino groups by the dianion groups, resulting in excellent anti-phenolic yellowing effect; secondly, it has excellent heat resistance and hand feel, with a fully saturated skeleton preventing high-temperature self-yellowing, and long-chain alkyl groups giving the fabric a fluffy and soft touch; thirdly, it has strong process compatibility, with low foaming and high penetration, suitable for high-speed clean production, and meets ecological standards.

[0027] In a preferred example of the preparation method of the novel nylon anti-phenol yellowing agent provided by the present invention, the following steps are included: Step 1 Maleic anhydride-taurine amidation: Under a dry nitrogen atmosphere, maleic anhydride is added to a reaction vessel and heated to about 55-65°C to dissolve and maintain the temperature for 10-15 minutes. Taurine is slowly added, stirred evenly, and kept warm. The ring-opening amidation reaction is carried out for 1-2 hours to obtain maleic anhydride-taurine amidation product.

[0028] Step 2 Alcohol Esterification and Dehydration Condensation: Add a catalyst to the maleic anhydride-taurine amide compound from Step 1 above, slowly add an alkyl alcohol, heat to 135-145°C under nitrogen protection, continuously separate the water generated in the reaction, and react for 5-8 hours to obtain the alcohol esterification and dehydration condensate.

[0029] Step 3 Sodium metabisulfite addition: The alcohol esterification dehydration condensate from Step 2 above is cooled to 50-60°C, and then a 20wt% sodium metabisulfite solution is slowly added to the alcohol esterification dehydration condensate. The reaction is carried out for 3-6 hours to obtain a novel nylon anti-phenol yellowing agent.

[0030] In the preparation process of the novel nylon anti-phenol yellowing agent, the reactants, maleic anhydride, taurine, catalyst, alkyl alcohol, and sodium metabisulfite are used in a molar equivalent ratio of 1:1:0.03-0.07:0.9-1:1-1.2.

[0031] In this document, the range expressed as "from one value to another" is a concise way of representing a range to avoid listing all the values ​​in that range in the specification. Therefore, the description of a particular range of values ​​covers any value within that range as well as the smaller range of values ​​defined by that value, just as if the arbitrary value and the smaller range of values ​​were explicitly stated in the specification.

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Improvements and adjustments made by those skilled in the art based on the present invention in practical applications still fall within the scope of protection of the present invention.

[0033] The present invention will be further described in detail below with reference to specific embodiments. In the following embodiments, "molar equivalent" is calculated based on maleic anhydride (1 part).

[0034] Example 1

[0035] Under a dry nitrogen atmosphere, 1 molar equivalent of maleic anhydride was added to the reaction vessel, heated to about 60°C to dissolve and kept at that temperature for 15 minutes, then 1 molar equivalent of taurine was slowly added, stirred until homogeneous, and kept at 60°C for 1 hour for ring-opening amidation reaction to obtain maleic anhydride-taurine amidate.

[0036] In the above-mentioned maleic anhydride-taurine amide, 0.05 molar equivalents of p-toluenesulfonic acid were added as a catalyst, and 0.95 molar equivalents of C12 lauryl alcohol were slowly added dropwise. The mixture was heated to 140°C under nitrogen protection, and the water generated in the reaction was continuously separated out. After 6 hours of reaction, an alcohol esterification dehydration condensate was obtained.

[0037] The above-mentioned alcohol esterification dehydration condensate was cooled to 50°C, and then a 20wt% sodium metabisulfite solution (molar equivalent ratio of sodium metabisulfite to intermediate was 1.10:1) was slowly added to the above-mentioned alcohol esterification dehydration condensate. The reaction was carried out at 55°C for 3.5 hours. The reaction endpoint was monitored by iodine value (the endpoint was when the iodine value tended to 0 and no longer decreased). The pH value of the product was adjusted to the range of 4.5-5.5 with citric acid to obtain the nylon anti-phenol yellowing agent of Example 1.

[0038] Example 2

[0039] Under a dry nitrogen atmosphere, 1 molar equivalent of maleic anhydride was added to the reaction vessel, heated to about 55°C to dissolve and kept at that temperature for 12 minutes, then 1 molar equivalent of taurine was slowly added, stirred until homogeneous, and kept at 55°C for 2 hours for ring-opening amidation reaction to obtain maleic anhydride-taurine amidate.

[0040] In the above-mentioned maleic anhydride-taurine amide, 0.07 molar equivalents of aminosulfonic acid were added as a catalyst, and 0.95 molar equivalents of C8 / C10 mixed alcohol were slowly added dropwise. The mixture was heated to 135°C under nitrogen protection, and the water generated in the reaction was continuously separated out. The reaction was carried out for 7 hours to obtain the alcohol esterification dehydration condensate.

[0041] The alcohol esterification dehydration condensate was cooled to 50°C, and then a 20wt% sodium metabisulfite solution (molar equivalent ratio of sodium metabisulfite to intermediate was 1.02:1) was slowly added to the alcohol esterification dehydration condensate. The reaction was carried out at 55°C for 4 hours. The reaction endpoint was monitored by iodine value (the endpoint was when the iodine value approached 0 and no longer decreased). The pH value of the product was adjusted to 4.5-5.5 with citric acid to obtain the nylon anti-phenol yellowing agent of Example 2.

[0042] Example 3

[0043] Under a dry nitrogen atmosphere, 1 molar equivalent of maleic anhydride was added to the reactor and heated to about 62°C to dissolve and maintain the temperature for 13 minutes. Then, 0.5 molar equivalents of taurine and 0.5 molar equivalents of methyl taurine were slowly added and stirred until homogeneous. The temperature was then maintained at 60°C for 1 hour to obtain the maleic anhydride-taurine amidate.

[0044] In the above-mentioned maleic anhydride-taurine amide, 0.03 molar equivalents of methanesulfonic acid were added as a catalyst, and 0.90 molar equivalents of C12 lauryl alcohol were slowly added dropwise. The mixture was heated to 145°C under nitrogen protection, and the water generated in the reaction was continuously separated out. After 8 hours of reaction, an alcohol esterification dehydration condensate was obtained.

[0045] The alcohol esterification dehydration condensate was cooled to 50°C, and then a 20wt% sodium metabisulfite solution (molar equivalent ratio of sodium metabisulfite to intermediate was 1.15:1) was slowly added to the alcohol esterification dehydration condensate. The reaction was carried out at 60°C for 4.5 hours. The reaction endpoint was monitored by iodine value (the endpoint was when the iodine value approached 0 and no longer decreased). The pH value of the product was adjusted to the range of 4.5-5.5 with citric acid to obtain the nylon anti-phenol yellowing agent of Example 3.

[0046] Example 4

[0047] Under a dry nitrogen atmosphere, 1 molar equivalent of maleic anhydride was added to the reaction vessel, heated to about 60°C to dissolve and kept at that temperature for 15 minutes, then 1 molar equivalent of taurine was slowly added, stirred until homogeneous, and kept at 60°C for 1 hour for ring-opening amidation reaction to obtain maleic anhydride-taurine amidate.

[0048] In the above-mentioned maleic anhydride-taurine amide, 0.05 molar equivalents of p-toluenesulfonic acid were added as a catalyst, and 0.95 molar equivalents of C12 / C14 mixed alcohol were slowly added dropwise. The mixture was heated to 145°C under nitrogen protection, and the water generated in the reaction was continuously separated out. After 5 hours of reaction, an alcohol esterification dehydration condensate was obtained.

[0049] The alcohol esterification dehydration condensate was cooled to 50°C, and then a 20wt% sodium metabisulfite solution (molar equivalent ratio of sodium metabisulfite to intermediate was 1.01:1) was slowly added to the alcohol esterification dehydration condensate. The reaction was carried out at 55°C for 3.5 hours. The reaction endpoint was monitored by iodine value (the endpoint was when the iodine value approached 0 and no longer decreased). The pH value of the product was adjusted to 4.5-5.5 with citric acid to obtain the nylon anti-phenol yellowing agent of Example 4.

[0050] Example 5

[0051] Under a dry nitrogen atmosphere, 1 molar equivalent of maleic anhydride was added to the reaction vessel and heated to about 65°C to dissolve and maintain the temperature for 15 minutes. Then, 1 molar equivalent of methyl taurine was slowly added and stirred until homogeneous. The temperature was then maintained at 65°C for 1 hour to obtain the maleic anhydride-taurine amidate.

[0052] In the above-mentioned maleic anhydride-taurine amide, 0.06 molar equivalents of p-toluenesulfonic acid were added as a catalyst, and 0.98 molar equivalents of C12 lauryl alcohol were slowly added dropwise. The mixture was heated to 140°C under nitrogen protection, and the water generated in the reaction was continuously separated out. The reaction was carried out for 7 hours to obtain the alcohol esterification dehydration condensate.

[0053] The alcohol esterification dehydration condensate was cooled to 50°C, and then a 20wt% sodium metabisulfite solution (molar equivalent ratio of sodium metabisulfite to intermediate was 1.2:1) was slowly added to the alcohol esterification dehydration condensate. The reaction was carried out at 50°C for 5 hours. The reaction endpoint was monitored by iodine value (the endpoint was when the iodine value approached 0 and no longer decreased). The pH value of the product was adjusted to the range of 4.5-5.5 with citric acid to obtain the nylon anti-phenol yellowing agent of Example 5.

[0054] Example 6

[0055] Under a dry nitrogen atmosphere, 1 molar equivalent of maleic anhydride was added to the reaction vessel and heated to about 60°C to dissolve and maintain the temperature for 12 minutes. Then, 0.2 molar equivalents of taurine and 0.8 molar equivalents of methyl taurine were slowly added and stirred until homogeneous. The temperature was then maintained at 60°C for 1 hour to obtain the maleic anhydride-taurine amidate.

[0056] In the above-mentioned maleic anhydride-taurine amide, 0.06 molar equivalents of camphor sulfonic acid were added as a catalyst, and 0.96 molar equivalents of C12 / C14 mixed alcohol were slowly added dropwise. The mixture was heated to 140°C under nitrogen protection, and the water generated in the reaction was continuously separated out. After 6 hours of reaction, an alcohol esterification dehydration condensate was obtained.

[0057] The alcohol esterification dehydration condensate was cooled to 50°C, and then a 20wt% sodium metabisulfite solution (molar equivalent ratio of sodium metabisulfite to intermediate was 1.1:1) was slowly added to the alcohol esterification dehydration condensate. The reaction was carried out at 50°C for 5 hours. The reaction endpoint was monitored by iodine value (the endpoint was when the iodine value approached 0 and no longer decreased). The pH value of the product was adjusted to 4.5-5.5 with citric acid to obtain the nylon anti-phenol yellowing agent of Example 6.

[0058] Example 7

[0059] Under a dry nitrogen atmosphere, 1 molar equivalent of maleic anhydride was added to the reaction vessel and heated to about 65°C to dissolve and maintain the temperature for 15 minutes. Then, 1 molar equivalent of methyl taurine was slowly added and stirred until homogeneous. The temperature was then maintained at 65°C for 1 hour to obtain the maleic anhydride-taurine amidate.

[0060] In the above-mentioned maleic anhydride-taurine amide, 0.06 molar equivalents of p-toluenesulfonic acid were added as a catalyst, and 0.98 molar equivalents of 2-ethylhexanol were slowly added dropwise. The mixture was heated to 140°C under nitrogen protection, and the water generated in the reaction was continuously separated out. After 7 hours of reaction, an alcohol esterification dehydration condensate was obtained.

[0061] The alcohol esterification dehydration condensate was cooled to 50°C, and then a 20wt% sodium metabisulfite solution (molar equivalent ratio of sodium metabisulfite to intermediate was 1.2:1) was slowly added to the alcohol esterification dehydration condensate. The reaction was carried out at 50°C for 5 hours. The reaction endpoint was monitored by iodine value (the endpoint was when the iodine value approached 0 and no longer decreased). The pH value of the product was adjusted to the range of 4.5-5.5 with citric acid to obtain the nylon anti-phenol yellowing agent of Example 5.

[0062] Results test: The nylon anti-phenol yellowing agents prepared in Examples 1-7 were each formulated into 10 g / L working solutions. These solutions were then added to standard nylon fabrics and immersed in an 80°C constant-temperature shaking dyeing vat for 40 min. After centrifugation and dehydration, and hot air drying at 80°C, phenol yellowing tests were performed according to ISO 105-X18:2007. The whiteness value of the samples was measured using a Color i5 benchtop spectrophotometer to evaluate the anti-phenol yellowing efficacy. Simultaneously, the pH value of each sample's original solution was directly measured, and the original solution was diluted to 5 g / L. The foam height was then measured using the Ross-Miles method. All performance tests were performed in triplicate, and the results were taken as the arithmetic mean. The fabric hand feel was assessed according to the subjective evaluation principles of AATCC 202-2014 and FZ / T 01166-2022. A review panel of five trained evaluators conducted blind touch tests on the treated nylon fabric under standard atmospheric conditions (temperature 20±2℃, relative humidity 65±4%) (according to GB / T 6529). The fabric was comprehensively scored based on four dimensions: softness, smoothness, bulkiness, and resilience, using a 1-5 scale: level 5 represents the best hand feel (soft, smooth, and without roughness), and level 1 represents the worst hand feel (stiff and rough). The average score was taken as the final hand feel grade. The measured values ​​are shown in Table 1 below.

[0063] Table 1 Whiteness 34.125 65.354 80.445 79.356 81.832 79.158 82.354 80.521 78.632 pH value 6.5 2.3 5.3 5.5 5.3 5.5 5.0 5.1 5.2 Foam height 0 21 12.1 10.5 12.1 13.2 8.5 12.9 13.0 feel 2.7 3.7 4.2 4.0 4.1 4.5 4.3 4.4 4.1 Notes: 1. The above data are average values; 2. The blank sample is without added anti-phenol yellowing agent and replaced with an equal amount of deionized water; 3. The nylon anti-phenol yellowing agent used in the external sample is a commercially available industrial application product (mainly composed of citric acid + AES anionic surfactant) collected by the marketing department and sourced from the dyeing and finishing production site.

[0064] Table 1 above systematically presents a comparison of the comprehensive performance of the novel nylon anti-phenol yellowing agent obtained in Examples 1-7 of this invention with the blank sample and commercially available foreign samples. The tests strictly followed the aforementioned standardized procedures (including taking the average of three parallel tests).

[0065] As can be seen from the test results in Table 1 above, in terms of anti-phenolic yellowing efficacy, the whiteness values ​​of Examples 1-7 all reached 79.158-82.354, which were significantly higher than those of the blank sample (34.125) and the foreign sample (65.354), confirming the high efficiency of the "steric hindrance of secondary sulfonic acid group + ionic bond targeted blocking" mechanism of the present invention. In terms of feel, the feel scores of Examples 1-7 were concentrated in the range of 4.0-4.5, which were all better than the foreign sample (3.7) and the blank sample (2.7). Among them, Example 4 reached 4.5, which is close to the optimal feel, reflecting the fluffy and soft touch brought by "long chain saturated carbon chain plasticization". In terms of process compatibility, the pH value of the example was stable at 5.0-5.5, which meets the ecological standards, and the foam height was controlled at 8.5-13.2 mm, which is significantly lower than that of the external sample (21 mm), verifying its "high penetration and low foam" characteristics, making it suitable for high-speed clean production.

[0066] In summary, this invention, through multiple synergistic mechanisms, comprehensively surpasses commercially available products in terms of superior anti-phenolic yellowing effect, hand feel, weak acid compatibility, and low foaming and high permeability. It achieves efficient and long-lasting anti-yellowing and high-quality finishing of nylon fabrics throughout the entire process of storage, transportation, and processing, and has significant industrial application value.

[0067] The above description discloses only preferred embodiments of the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to make good use of the invention. The present invention is limited only by the claims and their full scope and equivalents.

[0068] Under the guidance of the present invention and the above embodiments, those skilled in the art will readily foresee that all the raw materials or their equivalents, processing methods or their equivalents listed or exemplified in the present invention can achieve the present invention, and that the upper and lower limits and range values ​​of the parameters of each raw material and processing method can also achieve the present invention. Examples are not listed one by one here.

Claims

1. A nylon anti-phenol yellowing agent, characterized in that, The molecular structure of the nylon anti-phenolic yellowing agent is based on a maleic anhydride-derived backbone, with a hydrophobic end formed by a fully saturated long-chain alkyl group attached to one end via an ester bond, and a taurine structural unit connected to the other end via a hydrolysis-resistant amide bond. The maleic anhydride-derived backbone contains secondary sulfonic acid groups derived from the addition reaction of sodium metabisulfite, and the taurine units have terminal sulfonic acid groups. The molecular structural formula of the nylon anti-phenolic yellowing agent is as follows: ， R1 is selected from either H or CH3, and R2 is selected from C6-C. 30 At least one of straight-chain alkyl and branched-chain alkyl.

2. The nylon anti-phenol yellowing agent as described in claim 1, characterized in that, R2 is selected from C6-C 30 Two or more of straight-chain alkyl groups and branched-chain alkyl groups are present, in which case the nylon anti-phenol yellowing agent is a mixture.

3. A method for preparing a nylon anti-phenol yellowing agent according to any one of claims 1-2, characterized in that, Includes the following steps: Step 1 Maleic anhydride-taurine amidation: Under a dry, non-reactive protective gas atmosphere, maleic anhydride is added to the reaction equipment and heated to 55-65°C to melt and dissolve the maleic anhydride. Taurine is added, stirred evenly, and kept warm. The ring-opening amidation reaction is carried out at 55-65°C for 1-2 hours to obtain maleic anhydride-taurine amidation product. Step 2 Alcohol Esterification Dehydration Condensation: Add a catalyst to the maleic anhydride-taurine amide compound from Step 1 above, add an alkyl alcohol dropwise, heat to 135-145°C under a non-reactive protective gas, continuously separate the water generated in the reaction, and react for 5-8 hours to obtain the alcohol esterification dehydration condensate. Step 3 Sodium metabisulfite addition: The alcohol esterification dehydration condensate from Step 2 above is cooled to 50-60°C, and then a sodium metabisulfite solution with a concentration of 19.5-20.5 wt% is added to the obtained alcohol esterification dehydration condensate. The reaction is carried out for 3-6 hours to obtain the nylon anti-phenol yellowing agent.

4. The preparation method of the nylon anti-phenol yellowing agent as described in claim 3, characterized in that, In the preparation process of the nylon anti-phenol yellowing agent, the reactants, maleic anhydride, taurine, catalyst, alkyl alcohol, and sodium metabisulfite are used in a molar equivalent ratio of 1:1:0.03-0.07:0.9-1:1-1.

2.

5. The preparation method of the nylon anti-phenol yellowing agent as described in claim 3, characterized in that, The alkyl alcohol is selected from at least one of C6-C30 alkyl alcohols, wherein the C6-C30 alkyl alcohol contains a long-chain alkyl group, and the long-chain alkyl group is structurally a straight-chain alkyl group or a branched-chain alkyl group.

6. The method for preparing the nylon anti-phenol yellowing agent as described in claim 3 or 5, characterized in that, The alkyl alcohol is selected from at least one of C8-C14 alkyl alcohols.

7. The method for preparing the nylon anti-phenol yellowing agent as described in claim 3 or 5, characterized in that, The alkyl alcohol is selected from one of C12 lauryl alcohol, C8 / C10 mixed alcohol, and C12 / C14 mixed alcohol.

8. The preparation method of the nylon anti-phenol yellowing agent as described in claim 3, characterized in that, The taurine mentioned above can be replaced with methyl taurine or a mixture of taurine and methyl taurine.

9. The preparation method of the nylon anti-phenol yellowing agent according to claim 3, characterized in that, The catalyst is selected from at least one of p-toluenesulfonic acid, aminosulfonic acid, methanesulfonic acid, and camphorsulfonic acid.

10. The preparation method of the nylon anti-phenol yellowing agent according to claim 3, characterized in that, The basis for determining the end of the sodium metabisulfite addition process in Step 3 is to determine the reaction endpoint by the following iodine value monitoring results: During the reaction, the iodine value is measured at fixed intervals. When the data of 2 to 3 consecutive measurements are consistently lower than 0.5 g I2 / 100g, and the difference between two adjacent measurements does not exceed 0.05 g I2 / 100g, the reaction endpoint is determined to have been reached.

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