Method for chemically purifying aldehyde VOCs (Volatile Organic Chemicals) in leather

Abstract

The invention discloses a method for chemically purifying aldehyde VOCs (volatile organic compounds) in leather, an aldehyde catching agent is added in a spraying manner in a pre-prime coating stage in a leather coating procedure, and the method specifically comprises the following steps: 1) adding semicarbazide hydrochloride, glycoluril, sodium lauroyl glutamate and polyacrylamide into deionized water, and uniformly stirring to obtain the aldehyde catching agent; 2) uniformly adding the aldehyde trapping agent prepared in the step 1) to the meat surface of the leather in a spraying manner in a pre-prime coating stage in a leather coating procedure, standing until the aldehyde trapping agent is absorbed, drying, and entering a subsequent procedure after drying; the chemical purification method breaks through the limitation of traditional physical adsorption, effectively inhibits environmental release of aldehyde VOCs in leather products through an in-situ chemical immobilization strategy, has the characteristics of high reaction efficiency (gt, 90%), strong environmental durability, excellent eco-friendliness and the like, and provides an innovative solution for control of volatile aldehyde pollutants in the leather industry.

Description

Technical Field

[0001] The invention belongs to the technical field of volatile organic compound removal, and particularly relates to a method for chemical purification of leather aldehyde VOCs. Background Art

[0002] Volatile organic compounds (VOCs) in leather materials primarily include aldehydes, ketones, aromatic hydrocarbons, halogenated hydrocarbons, and alkanes. According to the technical requirements of GB / T 27630-2011, "Guidelines for Passenger Car Interior Air Quality Assessment," leather products must strictly control the release concentrations of benzene derivatives such as benzene, toluene, xylene, ethylbenzene, and styrene, as well as aldehydes such as formaldehyde, acetaldehyde, and acrolein. In a closed vehicle cabin, these pollutants primarily originate from interior materials such as seat leather, carpet assemblies, and headliners. Exposure pathways include respiratory inhalation and skin contact. Long-term, low-dose exposure can cause eye, nose, and throat irritation, neurological damage, and exhibits a significant dose-dependent association with malignancies such as leukemia and nasopharyngeal carcinoma.

[0003] Aldehyde compounds pose a particular risk among VOCs due to their low odor thresholds: the odor threshold of formaldehyde (HCHO) is 0.06-0.07 mg / m³, and that of acetaldehyde (CH3CHO) reaches 0.009 mg / m³. It is worth noting that acetaldehyde is not a component of the chemical additives in the traditional leather tanning process. Existing studies have confirmed that part of its source is related to the degradation reaction of threonine in leather collagen. Follow-up experiments have shown that the acetaldehyde concentration in finished leather shows an abnormal upward trend after 10 months of storage. Compared with low-boiling point aldehydes such as formaldehyde, the phase change characteristics of acetaldehyde make it more difficult to be effectively removed in conventional treatment processes. Based on the toxicological properties, persistent release characteristics and existing treatment technology bottlenecks of acetaldehyde, this study selected this substance as a typical representative of aldehyde VOCs to develop a new treatment system with targeted removal efficiency.

[0004] Existing treatment technologies for aldehyde-containing VOCs in leather include washing, photocatalysis, and chemical adsorption. Washing involves removing residual chemicals (such as formaldehyde, dyes, tanning agents, and other impurities) from the surface or interior of leather through washing or cleaning at the final stage of the leather manufacturing process. Patent publication number CN118086601A discloses a method for removing aldehyde-containing VOCs from leather by eluting with anhydrous ethanol containing urea. This method adds additional steps to the leather manufacturing process and requires subsequent solvent recovery, making the process cumbersome and costly. Photocatalysis utilizes photocatalytic activity to decompose harmful gases such as formaldehyde. Chinese patent publication number CN114797455A discloses spraying titanium dioxide phosphate on the leather surface to decompose volatile harmful substances such as aldehyde-containing VOCs in the air. This method requires sufficient light to activate the photocatalyst, is less effective in low-light or dark environments, and requires regular cleaning or replacement.

[0005] Chemical adsorption involves a chemical reaction between an aldehyde scavenger and aldehyde VOCs, converting them into harmless or stable substances, thereby achieving the removal of aldehyde VOCs. This invention simultaneously constructs a chemical conversion system for aldehyde VOCs during the pre-priming stage of the coating process. This bifunctional composite scavenger (containing semicarbazide hydrochloride and glycoluril as active components) achieves molecular-level removal through the following synergistic mechanism: ① The hydrazine group (-NH-NH2) of the semicarbazide undergoes a specific condensation reaction with the aldehyde group to form a hydrazone compound with a stable C=N-NHR structure; ② The cyclic tetraamino group (C4H6N4O2) of the glycoluril undergoes a Mannich condensation reaction with the aldehyde to form a Mannich base copolymer with a three-dimensional network structure. This synergistic conversion process covalently binds the aldehyde molecules, completely eliminating the possibility of room-temperature volatilization, providing the leather industry with a highly efficient and cost-effective aldehyde pollution control solution. Summary of the Invention

[0006] In light of the challenges of the existing technologies, the present invention aims to provide a method for chemically purifying aldehyde VOCs. During the pre-priming stage of the leather finishing process, a composite aldehyde scavenger is applied to the surface of the leather substrate using a directional spraying technique. This method overcomes the limitations of traditional physical adsorption and effectively suppresses the environmental release of aldehyde VOCs from leather products through an in-situ chemical immobilization strategy. The method boasts high reaction efficiency, strong environmental durability, and excellent eco-friendliness.

[0007] To achieve the above object, the technical solution of the present invention is as follows: A method for chemically purifying aldehyde VOCs in leather comprises adding an aldehyde scavenger by spraying during the pre-priming stage of the leather finishing process, and specifically comprising the following steps: 1) Add semicarbazide hydrochloride, glycoluril, sodium lauroyl glutamate and polyacrylamide into deionized water and stir evenly to obtain an aldehyde scavenger; 2) During the pre-priming stage of the leather finishing process, evenly add the aldehyde scavenger prepared in step 1) to the leather surface by spraying, let it stand for absorption, and then dry it. After drying, the next process can be carried out.

[0008] Furthermore, the method includes 3) periodically verifying the acetaldehyde content of the leather finished product treated in step 2) by a 2000L bag method on the day of production, 15 days after production, 30 days after production, and 60 days after production, respectively.

[0009] Furthermore, in step 1), the concentration of semicarbazide hydrochloride is 2-9wt%, the concentration of the glycoluril is 5-20wt%; the concentration of the sodium lauroyl glutamate is 0.1-0.3wt%; the concentration of the polyacrylamide is 0.1-0.3wt%; and the mass ratio of the polyacrylamide to sodium lauroyl glutamate, glycoluril and semicarbazide hydrochloride is 1:1:43.2-48.4:15.3-20.4.

[0010] Furthermore, in step 1), the concentration of semicarbazide hydrochloride is 5-7wt%, the concentration of glycoluril is 8-10wt%, the concentration of sodium lauroyl glutamate is 0.1wt%, and the concentration of polyacrylamide is 0.1wt%.

[0011] Furthermore, the mass ratio of the aldehyde scavenger used in step 2) to the area of the leather is 40-45 g / m 2 .

[0012] Furthermore, after the aldehyde scavenger is added in step 2), the absorption time of the leather at room temperature is 3-10 minutes; after the aldehyde scavenger is added, the leather enters the drying process at a drying temperature of 100-130°C.

[0013] Furthermore, in step 2), the absorption time is 5 minutes and the drying temperature is 110°C.

[0014] Furthermore, in step 3), the detection limit of acetaldehyde by the 2000L bag method was 2.4μg / m 3 .

[0015] Working mechanism of the present invention: Semicarbazide derivatives react with aldehyde molecules through nucleophilic addition reactions to form stable hydrazone derivatives (characteristic C=N-NHR structure). Simultaneously, the cyclic amino groups in the glycoluril molecules undergo Mannich condensation with the aldehyde groups, forming a Mannich base copolymer with a three-dimensional network structure. This dual chemical bonding mechanism not only modifies the molecular structure of aldehyde VOCs but also significantly improves the thermodynamic stability of the product by generating a high-boiling-point, low-volatility covalently bonded compound, ultimately removing aldehyde VOCs from leather.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) In the pre-priming stage of the leather finishing process, the present invention uses a directional spraying technology to load the composite aldehyde scavenger on the surface of the leather substrate. The acetaldehyde content of the leather is detected by the 2000L bag method, and the upper limit value is 2.4μg / m 3 ; 2) The semicarbazide derivative in the composite aldehyde scavenger of this invention reacts with aldehyde molecules through a nucleophilic addition reaction to form a stable hydrazone derivative (characteristic C=N-NHR structure). Simultaneously, the cyclic amino groups in the glycoluril molecules undergo a Mannich condensation reaction with the aldehyde groups to form a Mannich base copolymer with a three-dimensional network structure. This reaction is mild, has no side effects on leather, and does not cause secondary pollution. 3) The purification method of the present invention can capture more than 90% of free acetaldehyde within 10 minutes, and the reaction is highly efficient; 4) The present invention is simple to operate, can be sprayed at room temperature, and reacts immediately upon contact. The product is stable and reacts continuously, and can achieve a highly efficient formaldehyde removal effect that can last for more than two months. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the removal rate of quantitative acetaldehyde by different mass fractions of hydrochloric acid semicarbazide in Example 1; Figure 2 The removal rates of quantitative acetaldehyde by glycoluril with different mass fractions in Experimental Example 2 are shown in FIG. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0019] It should be noted that based on the toxicological properties, persistent release characteristics and existing treatment technology bottlenecks of acetaldehyde, this study selected acetaldehyde as a typical representative of aldehyde VOCs to develop a new treatment system with targeted removal efficiency. Example 1

[0020] First, a 1% CH3CHO aqueous solution was prepared, and at the same time, 2%, 3%, 4%, 6%, and 9% hydrochloric acid semicarbazide solutions were prepared respectively; Then measure the peak area of the blank sample of 10g 1% CH3CHO gas chromatograph; Then, 5 portions of 10g of 1% CH3CHO aqueous solution were taken and subjected to bubbling absorption reaction with 2g of hydrochloric acid semicarbazide solution with mass fractions of 2%, 3%, 4%, 6%, and 9% respectively for 10 minutes. The acetaldehyde peak area was detected in a gas chromatograph, and the acetaldehyde removal rate was calculated.

[0021] Depend on Figure 1 It can be seen that the higher the concentration of hydrochloric acid semicarbazide, the better the removal effect of aldehyde VOCs. When the mass fraction of hydrochloric acid semicarbazide solution is 9%, the acetaldehyde removal rate reaches 99.47%. Example 2

[0022] First, a 1% CH3CHO aqueous solution was prepared, and at the same time, glycoluril solutions with mass fractions of 5%, 10%, 15%, and 20% were prepared respectively; Then, measure the peak area of the blank sample of 10g 1% CH3CHO gas chromatograph; Then, 5 portions of 10g of 1% CH3CHO aqueous solution were taken and subjected to bubbling absorption reaction with 2g of 5%, 10%, 15%, and 20% glycoluril solutions respectively for 10 minutes. The acetaldehyde peak area was detected in a gas chromatograph, and the acetaldehyde removal rate was calculated.

[0023] Depend on Figure 2 It can be seen that the higher the concentration of glycoluril, the better the removal effect of aldehyde VOCs. When the concentration of glycoluril is 20%, the acetaldehyde removal rate reaches 87.33%. The longer the purification duration.

[0024] The concentration of the semicarbazide hydrochloride and glycoluril can be determined according to the content of aldehyde VOCs in the leather. Generally speaking, the higher the concentration, the better the removal effect of aldehyde VOCs and the longer the purification duration. However, due to the solubility of the substance and the impact on the surface properties of the leather, the color of the finished product, etc., the concentration of semicarbazide hydrochloride and glycoluril should be properly controlled. When spraying the aldehyde scavenger, in order to improve the removal effect of aldehyde VOCs, generally speaking, it is necessary to ensure that the spraying amount of the aldehyde scavenger is not less than 45g / m 2 . Example 3

[0025] From Example 1-2, 3.6 g of 5% semicarbazide hydrochloride, 9 g of 10% glycoluril, 0.18 g of 0.2% sodium lauroyl glutamate, and 0.18 g of 0.2% polyacrylamide were prepared with 77.04 g of deionized water to prepare an aldehyde scavenger aqueous solution. At room temperature, the aldehyde scavenger was sprayed during the pre-priming stage of the leather finishing process, with a dosage of 45 g per square meter of leather. After allowing the solution to penetrate for 5 minutes, the solution was dried at 110°C. After the treated leather finished product came off the production line, the acetaldehyde content of the leather was periodically verified using the NIO-TP.GS.001-2023 Determination of Volatile Organic Compounds Version 1.5 (2000 L bag method) on the day of, 15 days after, 30 days after, and 60 days after. The results are shown in Table 1.

[0026] Table 1

[0027] The acetaldehyde content of the treated leather product was 38.30μg / m on the day it came off the production line. 3, the acetaldehyde removal rate was 89.99%. 60 days after the finished leather was finished, the acetaldehyde removal rate could still reach 87.62%. This shows that the chemical purification of leather aldehyde VOCs by the present invention produces a stable product and continues to react, with a high-efficiency aldehyde removal effect that can last for more than two months.

Claims

1. A method for chemical purification of leather aldehyde VOCs, characterized in that In the pre-priming stage of the leather finishing process, an aldehyde scavenger is added by spraying, which specifically includes the following steps: 1) Add semicarbazide hydrochloride, glycoluril, sodium lauroyl glutamate and polyacrylamide into deionized water and stir evenly to obtain an aldehyde scavenger; 2) During the pre-priming stage of the leather finishing process, evenly add the aldehyde scavenger prepared in step 1) to the leather surface by spraying, let it stand for absorption, and then dry it. After drying, the next process can be carried out.

2. A method for chemical purification of leather aldehyde VOCs according to claim 1, characterized in that Including 3) after the leather finished product treated in step 2) comes off the production line, periodically verifying the acetaldehyde content of the leather finished product by using the 2000L bag method on the day of coming off the production line, 15 days after coming off the production line, 30 days after coming off the production line, and 60 days after coming off the production line.

3. The method for chemical purification of leather aldehyde VOCs according to claim 1, characterized in that In step 1), the concentration of semicarbazide hydrochloride is 2-9wt%, the concentration of the glycoluril is 5-20wt%; the concentration of sodium lauroyl glutamate is 0.1-0.3wt%; the concentration of the polyacrylamide is 0.1-0.3wt%; and the mass ratio of the polyacrylamide to sodium lauroyl glutamate, glycoluril and semicarbazide hydrochloride is 1:1:43.2-48.4:15.3-20.

4.

4. A method for chemical purification of leather aldehyde VOCs according to claim 3, characterized in that In step 1), the concentration of semicarbazide hydrochloride is 5-7wt%, the concentration of glycoluril is 8-10wt%, the concentration of sodium lauroyl glutamate is 0.1wt%, and the concentration of polyacrylamide is 0.1wt%.

5. The method for chemical purification of leather aldehyde VOCs according to claim 1, characterized in that The ratio of the mass of the aldehyde scavenger used in step 2) to the area of the leather is 40-45 g / m 2 .

6. The method for chemical purification of leather aldehyde VOCs according to claim 1, characterized in that After the aldehyde scavenger is added in step 2), the leather absorbs the aldehydes for 3-10 minutes at room temperature. After the aldehyde scavenger is added, the leather enters the drying process at a drying temperature of 100-130°C.

7. The method for chemical purification of leather aldehyde VOCs according to claim 6, characterized in that In step 2), the absorption time is 5 minutes and the drying temperature is 110°C.

8. The method for chemical purification of leather aldehyde VOCs according to claim 2, characterized in that In step 3), the detection limit of acetaldehyde by 2000L bag method was 2.4μg / m 3 .

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