A novel acetaldehyde scavenger, a preparation method and application thereof

Abstract

The application belongs to the technical field of automobile aldehyde removal, and particularly relates to a novel acetaldehyde aldehyde removal agent, a preparation method and application thereof. The aldehyde removal agent is prepared by loading a salt of diphenylmethylamine on a molecular sieve, and the aldehyde removal agent is granulated with a polypropylene double screw to obtain an aldehyde removal polypropylene material. The salt of diphenylmethylamine is pre-loaded on the molecular sieve, and in the polypropylene processing process, the molecular sieve can enrich aldehydes and react irreversibly with the released active amine to form imines, so as to lock the aldehydes in the pores. The aldehyde removal agent can efficiently and durably reduce the residues of acetaldehyde and propyl aldehyde in the polypropylene material, and at the same time, the problem of the increase of total VOC caused by free amine salt is avoided. Efficient aldehyde removal can be realized under conventional processing conditions, the indoor air quality is significantly improved, the preparation process is simple, the cost is controllable, and the application is suitable for the production of low-VOC polypropylene materials for automobile interiors.

Description

Technical Field

[0001] This invention belongs to the field of automotive formaldehyde removal technology, specifically relating to a novel acetaldehyde removal agent, its preparation method, and its application. Background Technology

[0002] Polypropylene (PP) has become one of the main matrix materials for automotive interior parts due to its lightweight, ease of processing, and cost advantages. However, during melt processing and subsequent use, polypropylene is prone to producing volatile carbonyl compounds such as acetaldehyde and acrolein under high-temperature shearing and oxidation. Acetaldehyde is a known Group 1 carcinogen, while acrolein is highly irritating and classified as a Group 2B possible carcinogen. The emission of these compounds directly affects the air quality inside the vehicle and the health of drivers and passengers.

[0003] To reduce aldehyde residues in polypropylene materials, existing technologies typically employ two methods: physical adsorption or chemical capture. Chinese patent CN107057185A points out that while using adsorbents such as molecular sieves can reduce VOCs to some extent, there is a significant limitation on adsorption equilibrium. At higher temperatures, the equilibrium shifts towards desorption, leading to the re-release of volatile organic compounds, thus failing to fundamentally eliminate the hazard of aldehydes. Chinese patent CN111054178B discloses a formaldehyde-removing purification material using a porous adsorbent material as a carrier and incorporating polyethyleneimine. This material loads reactive amine compounds onto a porous carrier, achieving aldehyde fixation through chemical adsorption or reaction. While this material exhibits a fast reaction rate and strong adsorption capacity, such technologies are primarily geared towards gas-phase air purification or liquid-phase raw material refining. Direct application to high-temperature melt processing systems for polypropylene presents problems such as uneven dispersion of active amines, insufficient thermal stability, or polymer degradation leading to an increase in total VOCs. Furthermore, while physical devolatilization can effectively remove most aldehydes, it relies on expensive high-vacuum, high-temperature equipment, resulting in huge energy consumption and the risk of over-processing leading to substrate degradation.

[0004] Therefore, there is an urgent need to develop a formaldehyde removal technology or agent that can economically and efficiently remove acetaldehyde and acrolein during polypropylene processing. Summary of the Invention

[0005] The purpose of this invention is to provide a novel acetaldehyde removal agent, its preparation method, and its application, overcoming the shortcomings of the prior art. This removal agent can effectively reduce the residual amount of acetaldehyde and acrolein during polypropylene processing, and its preparation process is simple and easy to scale up.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a novel acetaldehyde removal agent, comprising a molecular sieve and a salt of diphenylmethylamine loaded inside the molecular sieve.

[0007] Preferably, the salt of diphenylmethane is a salt formed by the reaction of diphenylmethane with an acid.

[0008] Preferably, the acid is acetic acid.

[0009] Preferably, the salt of the diphenylmethylamine is diphenylmethylamine acetate.

[0010] By preparing diphenylmethylamine in salt form, the residual acetaldehyde and acrolein in PP can be significantly reduced, improving the formaldehyde removal effect. This is because the salt of diphenylmethylamine can react with aldehydes generated during PP processing to form stable imines, achieving chemical removal of aldehydes. The acetate form of xyleneamine exhibits higher reaction efficiency and better formaldehyde removal effect. This may be because it is more easily decomposed or undergoes ion exchange at the polypropylene processing temperature, releasing nucleophilic free diphenylmethylamine in situ. Simultaneously, the introduction of acetate may provide a more favorable local microenvironment for the aldehyde-amine condensation reaction, thereby accelerating the formation of imines.

[0011] Preferably, the molecular sieve includes, but is not limited to, 5A and 13X type molecular sieves; more preferably, it is a 5A type molecular sieve.

[0012] Preferably, the particle size of the molecular sieve is 1~10μm.

[0013] By selecting type 5A molecular sieves as the support for diphenylmethylamine acetate and optimizing the particle size to 1-10 μm, the formaldehyde removal efficiency of the formaldehyde removal agent for acetaldehyde and acrolein can be improved. This is likely because the pore structure of type 5A molecular sieves is more suitable for the adsorption and reaction of acetaldehyde and acrolein molecules, enabling better loading of active components and promoting imidization reactions. Simultaneously, the smaller particle size of the molecular sieve provides a larger external surface area and shorter pore diffusion paths, offering more loading sites for active components, improving their dispersibility, and enhancing the reaction efficiency with aldehydes.

[0014] Preferably, the adsorption capacity of the diphenylmethylamine salt on the molecular sieve is 10% to 40%.

[0015] Formaldehyde removal agents prepared by loading diphenylmethylamine salt onto molecular sieves can further reduce acetaldehyde and acrolein residues and improve formaldehyde removal stability compared to directly adding diphenylmethylamine salt. This is because the molecular sieve can act as a carrier to disperse the active component of the diphenylmethylamine salt while simultaneously capturing aldehyde molecules, increasing the contact area between the active component and aldehydes, and synergistically improving formaldehyde removal efficiency. Furthermore, by controlling the adsorption amount of diphenylmethylamine acetate on the molecular sieve, a better balance can be achieved between the acetaldehyde and acrolein removal efficiency and total VOC control, avoiding the problem of increased total VOCs caused by excessive loading.

[0016] A second aspect of this invention provides a method for preparing the novel acetaldehyde removal agent, comprising the following steps: S1. Add diphenylmethylamine to water and stir to disperse. Slowly add an equivalent amount of acid to adjust the pH of the system to 6-8 to generate a salt solution of diphenylmethylamine. S2. Add molecular sieves to the diphenylmethylamine salt solution and reflux and stir overnight; S3. After cooling, filter the filter cake, wash it with water, and then vacuum dry it to obtain the final product.

[0017] Preferably, in step S1, the solid-liquid ratio of diphenylmethylamine to water is 1g:(15-25)mL.

[0018] Preferably, in step S2, the specific conditions for reflux stirring overnight are: temperature of 90~100℃, stirring speed of 100-150rpm, and overnight time of 15-20h.

[0019] Preferably, in step S3, the number of water washing cycles is 2-3, and the specific conditions for vacuum drying are: vacuum degree of 0.08-0.1MPa, temperature of 75-85℃, and time of 1.5-2.5h.

[0020] The synthesis reaction equation for the novel acetaldehyde removal agent described in this invention is as follows: Figure 1 .

[0021] A third aspect of the present invention provides the application of the novel acetaldehyde remover in the automotive field; more preferably, the novel acetaldehyde remover is used in the preparation of formaldehyde-removing polypropylene materials.

[0022] Preferably, the raw materials for preparing the formaldehyde-removing polypropylene material include a novel acetaldehyde removal agent and a polypropylene matrix.

[0023] Preferably, the amount of the novel acetaldehyde removal agent added is 0.1%-1% of the mass of the polypropylene matrix.

[0024] Preferably, the preparation method of the formaldehyde-removing polypropylene material includes the following steps: mixing a novel acetaldehyde removal agent with a polypropylene matrix, and then performing melt granulation using a twin-screw extruder to obtain the material.

[0025] Preferably, the process conditions of the twin-screw extruder are as follows: screw diameter (D) is 100 mm, length-to-diameter ratio (L / D) is 40:1, screw-barrel clearance (δ) is 2 mm, main machine speed (N) is 30 Hz, feeding zone temperature is 190°C, terminal temperature is 220°C, and die head temperature is 240°C.

[0026] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention proposes a novel acetaldehyde removal agent that can efficiently and persistently reduce the residue of acetaldehyde and acrolein in polypropylene materials, while avoiding the problem of increased total VOC caused by free amine salts. It can achieve efficient formaldehyde removal under conventional processing conditions, significantly improve the air quality inside vehicles, and has a simple preparation process and controllable cost, making it suitable for the production of low-VOC polypropylene materials such as automotive interiors.

[0027] 2. This invention, by preparing diphenylmethylamine into a salt form, can significantly reduce the residual acetaldehyde and acrolein in PP and improve the formaldehyde removal effect.

[0028] 3. This invention prepares an aldehyde removal agent by loading diphenylmethane salt onto a molecular sieve and controlling the adsorption amount, thereby achieving a better balance between the removal efficiency of acetaldehyde and acrolein and the control of total VOC, avoiding the problem of increased total VOC caused by excessive loading.

[0029] 4. By further selecting 5A type molecular sieve as the support for diphenylmethylamine acetate and optimizing the particle size to 1~10μm, the present invention can further improve the formaldehyde removal effect of the formaldehyde removal agent on acetaldehyde and acrolein. Attached Figure Description

[0030] Figure 1 The reaction equation for the synthesis of the novel acetaldehyde removal agent described in this invention is shown below.

[0031] Figure 2 This is a photograph of the novel formaldehyde remover prepared in Example 1 of the present invention.

[0032] Figure 3 This is a particle size analysis diagram of the novel formaldehyde removal agent prepared in Example 1 of the present invention.

[0033] Figure 4 Thermogravimetric analysis diagram of the novel formaldehyde removal agent prepared in Example 1 of this invention. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] All raw materials used in this invention are commercially available, as detailed below: All molecular sieves are from Sigma-Aldrich.

[0036] Polypropylene matrix, sourced from Sinopec Zhenhai Refining & Chemical PP045.

[0037] Example 1

[0038] This embodiment provides a novel acetaldehyde removal agent, comprising a molecular sieve and a salt of diphenylmethylamine loaded inside the molecular sieve.

[0039] The molecular sieve is a type 5A molecular sieve.

[0040] The molecular sieve has a particle size of 1~10μm.

[0041] The adsorption capacity of the diphenylmethylamine salt on the molecular sieve is 30%.

[0042] The salts of diphenylmethane are salts formed by the reaction of diphenylmethane with acid.

[0043] The acid is acetic acid.

[0044] The salt of the diphenylmethylamine is diphenylmethylamine acetate.

[0045] The preparation method of the novel acetaldehyde removal agent includes the following steps: S1. Add diphenylmethylamine to water and stir to disperse. Slowly add an equivalent amount of acetic acid until the pH of the system reaches 7, thus generating a salt solution of diphenylmethylamine. S2. Add molecular sieves to the diphenylmethylamine salt solution and reflux and stir overnight; S3. After cooling, filter the filter cake, wash it with water, and then vacuum dry it to obtain the final product.

[0046] In step S1, the solid-liquid ratio of diphenylmethylamine to water is 1g:20mL.

[0047] In step S2, the specific conditions for reflux stirring overnight are: temperature of 95℃, stirring speed of 120rpm, and overnight time of 18h.

[0048] In step S3, the water washing is performed 3 times, and the specific conditions for vacuum drying are: vacuum degree of 0.09MPa, temperature of 80℃, and time of 2h.

[0049] Photograph of the novel formaldehyde remover prepared in Example 1, see Figure 2 .

[0050] Example 2

[0051] This embodiment provides a novel acetaldehyde removal agent. The specific implementation method is the same as in Embodiment 1, except that: The adsorption capacity of the diphenylmethylamine salt on the molecular sieve is 10%.

[0052] Example 3

[0053] This embodiment provides a novel acetaldehyde removal agent, and the specific implementation method is the same as in Embodiment 1, except that: The adsorption capacity of the diphenylmethylamine salt on the molecular sieve is 20%.

[0054] Example 4

[0055] This embodiment provides a novel acetaldehyde removal agent, and the specific implementation method is the same as in Embodiment 1, except that: The adsorption capacity of the diphenylmethylamine salt on the molecular sieve is 40%.

[0056] Comparative Example 1 This comparative example provides a novel acetaldehyde removal agent, and the specific implementation method is the same as in Example 1, except that: The molecular sieve is a type 3A molecular sieve.

[0057] The molecular sieve has a particle size of 1~10μm and is sourced from Sigma-Aldrich.

[0058] Comparative Example 2 This comparative example provides a novel acetaldehyde removal agent, and the specific implementation method is the same as in Example 1, except that: The molecular sieve is a type 4A molecular sieve.

[0059] The molecular sieve has a particle size of 1~10μm and is from Sigma-Aldrich.

[0060] Comparative Example 3 This comparative example provides a novel acetaldehyde removal agent, and the specific implementation method is the same as in Example 1, except that: The molecular sieve is a 13X type molecular sieve.

[0061] The molecular sieve has a particle size of 1~10μm and is from Sigma-Aldrich.

[0062] Comparative Example 4 This comparative example provides a novel acetaldehyde removal agent, and the specific implementation method is the same as in Example 1, except that: The molecular sieve has a particle size of 25~38μm.

[0063] Comparative Example 5 This comparative example provides a novel acetaldehyde removal agent, and the specific implementation method is the same as in Example 1, except that: The molecular sieve has a particle size of 47~74μm.

[0064] Comparative Example 6 The only difference between this comparative example and Example 1 is that the formaldehyde removal agent is only diphenylmethylamine.

[0065] Comparative Example 7 The only difference between this comparative example and Example 1 is that the formaldehyde removal agent is only diphenylmethylamine hydrochloride.

[0066] The acid is hydrochloric acid.

[0067] The salt of the diphenylmethylamine is a diphenylmethylamine salt.

[0068] Comparative Example 8 The only difference between this comparative example and Example 1 is that the formaldehyde removal agent is only the acetate of diphenylmethylamine.

[0069] The acid is acetic acid.

[0070] The salt of the diphenylmethylamine is diphenylmethylamine acetate.

[0071] Comparative Example 9 The only difference between this comparative example and Example 1 is that the formaldehyde remover is only a phosphate of diphenylmethylamine.

[0072] The acid is phosphoric acid.

[0073] The salt of the diphenylmethylamine is diphenylmethylamine phosphate.

[0074] Comparative Example 10 The only difference between this comparative example and Example 1 is: Use benzylamine instead of diphenylmethylamine.

[0075] Comparative Example 11 The only difference between this comparative example and Example 1 is: The acid is citric acid.

[0076] The salt of the diphenylmethylamine is diphenylmethylamine citrate.

[0077] Comparative Example 12 The only difference between this comparative example and Example 1 is: Fumed silica is used to replace molecular sieves, and the specific surface area of ​​fumed silica is 120-180 m². 2 / g, from Shanghai McLean Biochemical Technology Co., Ltd.

[0078] Comparative Example 13 The only difference between this comparative example and Example 1 is: The molecular sieve is ZSM-5 molecular sieve, sourced from Yueyang Huijing New Material Technology Co., Ltd.

[0079] Performance testing The formaldehyde removal agent prepared by the above examples and comparative examples and the polypropylene matrix are used to prepare the formaldehyde removal agent propylene material. The preparation method of the formaldehyde removal polypropylene material is as follows: the novel acetaldehyde removal agent is mixed with the polypropylene matrix and melt-granulated by a twin-screw extruder to obtain the formaldehyde removal agent propylene material.

[0080] The process conditions for the twin-screw extruder are as follows: screw diameter (D) 100 mm, length-to-diameter ratio (L / D) 40:1, screw-barrel clearance (δ) 2 mm, main machine speed (N) 30 Hz, feeding zone temperature 190 ℃, terminal temperature 220 ℃, and die head temperature 240 ℃.

[0081] The amount of formaldehyde remover added to PP was adjusted. The VOC, acetaldehyde residue, and acrolein residue of the propylene materials prepared with formaldehyde removers in each example were tested. The detection method referred to GB / T 39107-2020 "Determination of Volatile Organic Compounds in Consumer Products - Static Headspace Sampling Method". The results are shown in Table 1.

[0082] Table 1

[0083] As shown in Table 1, Example 1, using 1-10 μm small-particle-size 5A molecular sieve loaded with diphenylmethylamine acetate, with an adsorption capacity of 30% and an addition of 0.5% to PP, achieved acetaldehyde and acrolein residues as low as 50 ppm and 130 ppm, respectively, while VOCs were 30,000 ppm. This not only achieved significant simultaneous removal of acetaldehyde and acrolein but also demonstrated significantly better performance than other adsorption capacities and comparative examples. Examples 2-4 adjusted the adsorption capacity of diphenylmethylamine salt on the molecular sieve to 10%, 20%, and 40%, respectively. It can be seen that as the adsorption capacity increased from 10% to 30%, the aldehyde removal effect continuously improved; however, when the adsorption capacity reached 40%, the acetaldehyde residue rebounded to 60 ppm, and the acrolein residue rebounded to 160 ppm, resulting in a slightly inferior effect compared to Example 1. This may be because when the adsorption capacity exceeds 30%, the molecular sieve pores may be overfilled or even blocked, hindering aldehydes from entering the pores. Simultaneously, the generated imine occupies reaction sites, reducing the effective reaction capacity.

[0084] Comparative Examples 1-4 investigated different types of molecular sieves. Comparative Example 1 used 3A molecular sieve, Comparative Example 2 used 4A molecular sieve, and Comparative Example 3 used 13X molecular sieve. Compared with the examples, the acrolein residues in Comparative Examples 1-3 were significantly higher, especially the 3A and 4A molecular sieves, which caused acrolein to rise abnormally to 880 ppm and 750 ppm, respectively. This may be because the pore size of 3A and 4A molecular sieves is too small, making it difficult for acrolein to enter the pores and react with the active amines. It is even possible that the acidic sites on the surface of the molecular sieves catalyze the degradation of PP to generate more acrolein. The 13X molecular sieve has a large pore size, which weakens its ability to enrich and lock aldehydes, resulting in higher acetaldehyde residues.

[0085] Comparative Examples 4 and 5 used 5A molecular sieves with larger particle sizes. In Comparative Example 4, the 5A molecular sieve particle size was 25–38 μm, and in Comparative Example 5, the particle size was 47–74 μm. Compared to the examples, with increasing particle size, both acrolein and acetaldehyde residues slightly increased. This may be because larger particle size molecular sieves have a smaller specific surface area, poorer dispersion uniformity in PP, and longer diffusion paths, leading to a decrease in formaldehyde removal efficiency.

[0086] Comparative Example 6 did not use molecular sieves; only diphenylmethylamine was added to PP. With increasing diphenylmethylamine addition, both acetaldehyde and acrolein residues decreased. The difference in acetaldehyde and acrolein residues was minimal at addition levels of 0.5% and 1%, and the total VOC level reached 35,000 ppm when diphenylmethylamine addition was 1%. This indicates that while diphenylmethylamine free alkali has a certain formaldehyde removal effect, it exhibits a "threshold effect," and excessive addition can itself become a new source of VOCs. Comparative Examples 7 and 9 did not use molecular sieves, containing only diphenylmethylamine hydrochloride and diphenylmethylamine phosphate, respectively. Both acetaldehyde and acrolein residues were high. This may be because hydrochloride and phosphate are difficult to release active amines, and the HCl released by phosphate may catalyze PP degradation to produce more aldehydes. Comparative Example 8 did not use molecular sieves, containing only diphenylmethylamine acetate. Acetaldehyde and acrolein residues were 160 ppm and 250 ppm, respectively, showing better results than free alkali, hydrochloride, and phosphate, indicating that acetate is more likely to release active amines.

[0087] Comparative Example 10 used benzylamine instead of diphenylmethylamine and monophenyl instead of diphenyl, resulting in easy decomposition of the product. Comparative Example 11 used citric acid instead of acetic acid, but the decomposition temperature was too low. Comparative Examples 12 and 13 used fumed silica and ZSM-5 molecular sieves respectively to replace 1~10μm 5A molecular sieves, and both showed poor aldehyde removal effects.

[0088] The particle size analysis diagram of the novel formaldehyde removal agent prepared in Example 1 of this invention is shown in the figure. Figure 3 .from Figure 3 It can be seen that the average surface particle size is 4.49 μm, the average volume particle size is 20.9 μm, Dv(10) is 1.53 μm, Dv(50) is 13.5 μm, and Dv(90) is 42.1 μm.

[0089] Thermogravimetric analysis (TGA) curve of the novel formaldehyde removal agent prepared in Example 1 of this invention is shown below. Figure 4 .from Figure 4 It can be seen that the temperature of 1% thermal weight loss is 212℃.

[0090] Therefore, this invention prepares a novel acetaldehyde removal agent by loading diphenylmethylamine acetate onto 5A molecular sieves with a particle size of 1~10μm, and adds it to PP to achieve the best removal effect of acetaldehyde and acrolein in a synergistic manner, while avoiding the problem of increased total VOC caused by free amine salts, thus significantly improving the air quality inside the vehicle.

[0091] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A novel acetaldehyde removal agent, characterized in that, It comprises a molecular sieve and a salt of diphenylmethylamine loaded inside the molecular sieve.

2. The novel acetaldehyde removal agent according to claim 1, characterized in that, The molecular sieves include, but are not limited to, 5A and 13X type molecular sieves.

3. The novel acetaldehyde removal agent according to claim 2, characterized in that, The molecular sieve has a particle size of 1~10μm.

4. The novel acetaldehyde removal agent according to claim 1, characterized in that, The adsorption capacity of the diphenylmethylamine salt on the molecular sieve is 10% to 40%.

5. The novel acetaldehyde removal agent according to claim 4, characterized in that, The salts of diphenylmethane are salts formed by the reaction of diphenylmethane with acid.

6. The novel acetaldehyde removal agent according to claim 5, characterized in that, The acid is acetic acid.

7. The novel acetaldehyde removal agent according to claim 6, characterized in that, The salt of the diphenylmethylamine is diphenylmethylamine acetate.

8. A method for preparing a novel acetaldehyde removal agent according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Add diphenylmethylamine to water and stir to disperse. Slowly add acid to adjust the pH of the system to 6-8 to generate a salt solution of diphenylmethylamine. S2. Add molecular sieves to the diphenylmethylamine salt solution and reflux and stir overnight; S3. After cooling, filter the filter cake, wash it with water, and then vacuum dry it to obtain the final product.

9. The application of a novel acetaldehyde removal agent according to any one of claims 1 to 7 in the automotive field, characterized in that, The novel acetaldehyde removal agent is used in the preparation of acetaldehyde-removing polypropylene materials.

10. The application of the novel acetaldehyde removal agent according to claim 9, characterized in that, The raw materials for preparing the formaldehyde-removing polypropylene material include a novel acetaldehyde removal agent and a polypropylene matrix; the amount of the novel acetaldehyde removal agent added is 0.1%-1% of the mass of the polypropylene matrix.

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