A polyurethane foam aldehyde removal additive, its preparation method and application

Abstract

The application discloses a kind of polyurethane foam aldehyde removal additives and its preparation method and application, the additive includes the following components according to weight percentage content: amino acid 3-6%, hydrazine class substance 6-25%, water 25-50%, auxiliary agent 20-45%, metal inorganic salt 0.5-2%, urea class substance 5-15% and organic acid 0.3-1%.The aldehyde removal additive of the application is applied in the preparation of polyurethane foam, the effect is remarkable, long duration, high safety and environment friendly.

Description

Technical Field

[0001] This invention belongs to the field of odor purification, specifically relating to a polyurethane foam formaldehyde removal additive, its preparation method, and its application. Background Technology

[0002] Polyurethane foam is widely used in furniture, automotive interiors, building insulation, and packaging materials due to its excellent mechanical properties, good cushioning, sound and heat insulation, and processability. However, polyurethane foam releases various volatile organic compounds (VOCs) during production and long-term use, among which the adverse effects of aldehydes, represented by formaldehyde, are particularly prominent. Developing low-formaldehyde or even formaldehyde-free polyurethane foam products has become a core direction for technological development in the industry.

[0003] Currently, the technical approaches to reducing formaldehyde release from polyurethane foam can be mainly divided into three categories: source control, physical adsorption, and chemical additives.

[0004] In terms of source control, aldehyde residues can be reduced from the raw material stage by optimizing the production process of polyether polyols and using low-volatility polyether monomers and low-odor catalysts. However, this approach is highly dependent on raw material suppliers, resulting in a significant increase in costs, and it cannot eliminate aldehydes generated during later use due to the oxidation and breakage of polyether chains or the action of residual catalysts.

[0005] In terms of physical adsorption, porous materials such as activated carbon, bamboo charcoal, and diatomaceous earth are introduced into the polyurethane system to capture formaldehyde molecules through physical adsorption. However, physical adsorption has an upper limit on adsorption capacity, and there is a risk of secondary formaldehyde release under high temperature and high humidity conditions. Furthermore, the addition of a large amount of powder filler can significantly affect the mechanical properties of the foam and the stability of the foaming process.

[0006] In terms of chemical additives, introducing formaldehyde-removing agents that can chemically react with formaldehyde into polyurethane raw materials is a currently popular technological approach. Existing chemical formaldehyde-removing agents can be divided into two categories according to their addition location: one type is applied after foaming through spraying, impregnation, or other methods. This method requires a large amount of formaldehyde-removing agent, has uneven distribution, and easily clogs the cell structure; the other type is added directly to the polyether polyol component before foaming. This method is simple to operate and produces a uniform distribution of the formaldehyde-removing agent, and is currently the mainstream direction of technological development.

[0007] For the latter type of technology, relevant patents and literature have been explored. US20170129988A1 and WO2014 / 026802A1 disclose a compound system of cyclic urea derivatives and amine compounds, claiming to significantly reduce formaldehyde emissions. However, polyamines (such as triethylenetetramine, tetraethylenepentamine, etc.) have a strong ammonia odor and are irritating. While reducing formaldehyde, they may introduce new odor problems. Furthermore, since amines exist in a physically blended form, there is a risk of migration and precipitation.

[0008] Recently disclosed patented technologies use barbituric acid or thiobarbituric acid in combination with primary amine compounds, claiming to simultaneously reduce formaldehyde and acetaldehyde emissions. However, barbituric acid compounds have limited solubility in conventional polyether polyols, and usually require special solvents or heating conditions to achieve uniform dispersion.

[0009] Amino acids have attracted attention in the field of formaldehyde purification due to their natural origin, biodegradability, and the presence of primary amino groups in their molecular structure that can undergo nucleophilic addition reactions with aldehydes. Literature reports that glycine, L-lysine, and L-arginine have been used for formaldehyde capture in systems such as water-based coatings and adhesives for engineered wood products. However, directly applying amino acids to polyurethane foam systems still faces three major obstacles: First, amino acids are polar crystalline solids with extremely poor solubility in non-polar polyether polyols; second, the carboxyl groups in amino acid molecules have a certain degree of acidity, which, if not properly controlled, can interfere with the isocyanate-hydroxyl reaction, leading to deviations in foaming parameters or even foam collapse; third, the reaction rate constant between amino acids and formaldehyde is finite, making it difficult to fully capture free aldehydes within the short process window of polyurethane foaming, which lasts only a few minutes.

[0010] Furthermore, US20120184639A1 discloses a technical solution using aminourea compounds as formaldehyde removal agents in polyurethane foam; Dow Chemical proposed a 3-oxopropionamide reactive formaldehyde removal agent in US12344723B2. Although these compounds can participate in polyurethane crosslinking, their formaldehyde removal mechanism relies on a single functional group, and they still have shortcomings in terms of rapid capture of the foaming window and long-term thermodynamic stability; CN112661646A describes an active methylene formaldehyde removal agent, but its formaldehyde removal reaction requires alkaline conditions to achieve optimal activity, posing a challenge to its process compatibility with polyurethane foaming systems. None of the above-mentioned prior art discloses or suggests a technical solution for the synergistic compounding of multiple components such as amino acids, hydrazides, ureas, metal inorganic salts, and organic acids.

[0011] Current chemical formaldehyde removal agents generally only focus on formaldehyde removal efficiency, while neglecting the impact on the foaming process and the introduced odor problem. Some formaldehyde removal agents (such as low molecular weight amines) can accelerate or inhibit the polyurethane foaming reaction, causing deviations in the milky white time, rise time, and gel time, severely affecting the foam's cell structure and mechanical properties; some formaldehyde removal agents themselves have an irritating odor, so although the formaldehyde level is reduced, the overall odor of the foam does not improve or may even worsen.

[0012] Therefore, developing a liquid formaldehyde removal additive that can be directly added to polyether polyols, which has high formaldehyde removal capabilities without affecting the polyurethane foaming reaction process, and does not introduce or improve the overall odor of the foam, has significant technical value and industrialization implications. Summary of the Invention

[0013] In view of the problems existing in the prior art, the purpose of the present invention is to provide a formaldehyde removal additive for polyurethane foam and its preparation method. The formaldehyde removal additive of the present invention is effective, long-lasting, safe and environmentally friendly when applied to the preparation of polyurethane foam.

[0014] To achieve the above objectives, the technical solution of the present invention is as follows: A polyurethane foam formaldehyde removal additive, comprising the following components by weight percentage: 3-6% amino acids, 6-25% acylhydrazine substances, 25-50% water, 20-45% additives, 0.5-2% inorganic metal salts, 5-15% urea substances, and 0.3-1% organic acids.

[0015] Further, by weight percentage, it includes the following components: 3-4% amino acids, 9-24% acylhydrazides, 32-40% water, 25-41% auxiliaries, 0.6-0.7% inorganic metal salts, 8-14% urea compounds, and 0.3-0.4% organic acids.

[0016] Furthermore, the amino acid is one or more of D-aspartic acid, D-alanine, DL-leucine, DL-serine, L-lysine, L-arginine, L-histidine, L(+)-cysteine, and glycine.

[0017] Furthermore, the additive is one or more of dimethyl sulfoxide, dipropylene glycol, polyethylene glycol, ethylene glycol, and high EO polyether.

[0018] Furthermore, the inorganic metal salt is one or more of zinc chloride, zirconium chloride, sodium sulfite, and sodium thiosulfate.

[0019] Further, the urea compound is one or more of 2-imidazolone, 4,5-dihydroxy-2-imidazolone, 4,5-dimethoxy-2-imidazolone, 1,3-dimethyl-2-imidazolone, and N-hydroxyethyl-2-imidazolone.

[0020] Furthermore, the organic acid is one or more of acetic acid, citric acid, tartaric acid, lactic acid, adipic acid, and gluconic acid.

[0021] Furthermore, the acylhydrazines are one or more of the following: acetylhydrazine, benzoylhydrazine, isophthalylhydrazine, octanoylhydrazine, sebacic acid diacylhydrazine, succinic acid diacylhydrazine, adipic acid diacylhydrazine, and isoniazid.

[0022] The preparation method of the polyurethane foam formaldehyde removal additive is as follows: weigh the raw materials according to the raw material formula, first dissolve the organic acid in water, then add amino acids and stir until completely dissolved; then add the additives and urea substances in sequence, heat to 40-45℃ and stir for 10-60 minutes; after cooling to 30±5℃, finally slowly add acylhydrazine substances and metal inorganic salts, and stir until uniform and transparent.

[0023] This invention also discloses the application of the aforementioned polyurethane foam formaldehyde removal additive in the preparation of polyurethane foam, wherein the raw material components include polyether polyol, isocyanate and the additive.

[0024] The components of this invention work synergistically to achieve highly efficient formaldehyde removal, process stability, and low odor. The mechanism of action is as follows: (1) Amino acids are the core functional components. Their primary amino groups (-NH2) undergo irreversible chemical capture with formaldehyde. At the same time, their active hydrogen groups such as carboxyl groups can react with isocyanates to graft the formaldehyde removal active sites into the polyurethane polymer skeleton in the form of covalent bonds, thereby achieving long-term fixation.

[0025] (2) Acylhydrazide compounds have higher nucleophilic reactivity and rapidly consume most of the free aldehydes in the initial stage of foaming. They form a "fast-slow complementary" kinetic match with amino acids, which effectively controls formaldehyde in both the initial stage of foaming and the long-term use stage.

[0026] (3) Urea compounds, as the third line of defense, form condensates with formaldehyde with high thermodynamic stability. Even in high temperature or humid environments, they are not easily reversibly decomposed, and the residual aldehydes are further converted into stable condensation products. The triple mechanism complements each other in terms of kinetics and thermodynamics.

[0027] (4) Metal inorganic salts reduce the activation energy of the formaldehyde removal reaction by coordinating with amino acids and hydrazides, thus accelerating the reaction process and ensuring a high conversion rate within the short process window of polyurethane foaming.

[0028] (5) Organic acids adjust the pH of the system to a weakly acidic range, effectively inhibiting side reactions such as hydrazide auto-oxidation and amino acid deamination, and prolonging the storage stability of the additive.

[0029] (6) The additives disperse polar components such as amino acids in non-polar polyether polyols through hydrogen bonding, achieving molecular-level dispersion, avoiding solid particles as nucleation sites that interfere with the cell structure, and have no irritating odor, thus not affecting the mechanical properties of the foam.

[0030] The above six components are functionally interconnected, working synergistically to achieve a comprehensive formaldehyde removal effect that is highly efficient, long-lasting, process-compatible, and low in odor.

[0031] In summary, compared with the prior art, the present invention has the following substantial differences and technical contributions: (1) In the field of formaldehyde removal from polyurethane foam, this invention is the first to integrate six types of components—amino acids, acylhydrazides, ureas, inorganic metal salts, organic acids, and additives—into a single additive system, constructing a complete six-in-one technical solution of "rapid capture (acylhydrazides) - chemical anchoring and continuous capture (amino acids) - thermodynamic stability (ureas) - catalytic acceleration (inorganic metal salts) - stable storage (organic acids) - molecular-level dispersion (additives)." The functions of each component are clearly defined and they support each other. No literature in the prior art has disclosed or implied this six-component synergistic combination.

[0032] (2) The catalytic acceleration effect of metal inorganic salts in polyurethane formaldehyde removal system was discovered. In the prior art, metal inorganic salts are only used as catalysts in the polyurethane synthesis reaction itself. However, this invention creatively introduces them into the formaldehyde removal reaction system. By reducing the reaction activation energy through coordination activation, the bottleneck of insufficient reaction kinetics of amino acids in the short foaming window is effectively solved. This application and transfer of use is outstandingly creative.

[0033] (3) The chemical grafting and fixation of amino acids in polyurethane foam has been achieved. Unlike the existing technology where amino acids are only used as physical blending additives, this invention utilizes the reaction between the carboxyl group of amino acid and the isocyanate group to covalently bond the formaldehyde removal active site to the polymer backbone, thereby achieving long-lasting and non-migrating formaldehyde removal function and overcoming the technical problem of formaldehyde removal agent migration and precipitation that has long existed in this field.

[0034] (4) It effectively solves the contradiction between "formaldehyde removal efficiency and process compatibility" in existing formaldehyde removal technologies. Through the catalytic acceleration of metal inorganic salts and the thermodynamic supplementation of urea, this invention can achieve a formaldehyde removal rate far higher than that of existing technologies (96.73% in Example 5) with a lower amino acid dosage (3-5%), while maintaining the normal foaming process. This is a synergistic effect that is difficult for those skilled in the art to foresee.

[0035] The aforementioned distinguishing technical features are not simply the sum of the functions of each component, but rather achieve a synergistic effect of "1+1>2" through scientific mechanism matching, which constitutes the substantial features and significant progress of this invention that distinguish it from the prior art. Detailed Implementation

[0036] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0037] The high-EO polyether used in the following embodiments of the present invention has a number-average molecular weight of 4800-5000, a hydroxyl value of 34-36 mg KOH / g, a mass percentage content of EO structural units of 16%, a primary hydroxyl content of ≥75% of all hydroxyl groups, and a viscosity of 900-1200 mPa·s at 25°C. Furthermore, the polyethylene glycol used in the following embodiments of the present invention has a molecular weight of 200.

[0038] The formaldehyde-removing additive of the present invention was added to the polyether polyol at a ratio of 1% by mass. After stirring at 20-30°C for 5 min, the appearance of the system was observed. The results showed that the samples of each embodiment formed a uniform, transparent or microemulsified stable dispersion system in the polyether polyol, and no layering, precipitation, or sedimentation occurred after standing for 24 h. This indicates that the present invention, through a compound additive system of water, glycols, and high-EO polyether, effectively improves the compatibility of amino acids in the polyether system, laying the foundation for the application of amino acids in polyurethane foam foaming systems.

[0039] Example 1: A polyurethane foam formaldehyde removal additive, comprising the following components by weight: 45% water, 10% high EO polyether, 18% dipropylene glycol, 5% L-arginine, 8% acetylhydrazine, 3% benzoylhydrazine, 3% isophthalylhydrazine, 7% 1,3-dimethyl-2-imidazolidineone, 0.7% zinc chloride, and 0.3% tartaric acid.

[0040] The preparation method of the additive is as follows: weigh the raw materials according to the raw material formula, dissolve the organic acid in water first, then add the amino acid and stir until completely dissolved; then add the auxiliary agent and urea substance in sequence, heat to 40-45℃ and stir for 30 minutes; after cooling to 30℃, finally slowly add the acylhydrazine substance and metal inorganic salt, and stir until uniform and transparent.

[0041] Example 2: A polyurethane foam formaldehyde removal additive, comprising the following components by weight: 24% water, 48% dipropylene glycol, 5% DL-serine, 4% maleic dihydrazide, 4% isophthalic acid dihydrazide, 7% isoniazid, 7% 1,3-dimethyl-2-imidazolium ketone, 0.7% zirconium chloride, and 0.3% tartaric acid.

[0042] Example 3: A polyurethane foam formaldehyde removal additive, comprising the following components by weight: 32% water, 18% dipropylene glycol, 23% polyethylene glycol, 3% glycine, 4% benzoyl hydrazine, 5% acetyl hydrazine, 7% 2-imidazolidineone, 7% 1,3-dimethyl-2-imidazolidineone, 0.7% sodium thiosulfate, and 0.3% tartaric acid.

[0043] Example 4: A polyurethane foam formaldehyde removal additive, comprising the following components by weight: 33% water, 20% dipropylene glycol, 10% polyethylene glycol, 2% high EO polyether, 3% D-alanine, 3% octanoyl hydrazine, 4% benzoyl hydrazine, 5% sebacic acid dihydrazine, 7% succinic acid dihydrazine, 2% adipic acid dihydrazine, 10% N-hydroxyethyl-2-imidazolium ketone, 0.7% zinc chloride, and 0.3% adipic acid.

[0044] Example 5: A polyurethane foam formaldehyde removal additive, comprising the following components by weight: 38% water, 23% dipropylene glycol, 2% high EO polyether, 4% L(+)-cysteine, 3% benzoyl hydrazine, 7% isoniazid, 5% sebacic acid dihydrazine, 7% succinic acid dihydrazine, 2% adipic acid dihydrazine, 8% 4,5-dihydroxy-2-imidazolium ketone, 0.7% sodium sulfite, and 0.3% citric acid.

[0045] Comparative Example 1: The composition of the additive in Comparative Example 1 is the same as that in Example 5, except that "no acyl hydrazide substances are added, and the amount of water is increased to make up the total amount".

[0046] The polyurethane foam formaldehyde removal additive of Comparative Example 1 comprises the following components by weight: 62% water, 23% dipropylene glycol, 2% high EO polyether, 4% L(+)-cysteine, 8% 4,5-dihydroxy-2-imidazolidineone, 0.7% sodium sulfite, and 0.3% citric acid.

[0047] Comparative Example 2: The composition of the additive in Comparative Example 2 is the same as that in Example 5, except that "L(+)-cysteine ​​is not added and the amount of water is increased to make up the total amount".

[0048] The polyurethane foam formaldehyde removal additive of Comparative Example 2 comprises the following components by weight: 42% water, 23% dipropylene glycol, 2% high EO polyether, 3% benzoyl hydrazine, 7% isoniazid, 5% sebacic acid dihydrazine, 7% succinic acid dihydrazine, 2% adipic acid dihydrazine, 8% 4,5-dihydroxy-2-imidazolium ketone, 0.7% sodium sulfite, and 0.3% citric acid.

[0049] Comparative Example 3: The composition of the additive in Comparative Example 3 is the same as that in Example 5, except that "4,5-dihydroxy-2-imidazolone is not added, and the amount of water is increased to make up the total amount".

[0050] The polyurethane foam formaldehyde removal additive of Comparative Example 3 comprises the following components by weight: 46% water, 23% dipropylene glycol, 2% high EO polyether, 4% L(+)-cysteine, 3% benzoyl hydrazine, 7% isoniazid, 5% sebacic acid dihydrazine, 7% succinic acid dihydrazine, 2% adipic acid dihydrazine, 0.7% sodium sulfite, and 0.3% citric acid.

[0051] Comparative Example 4: The composition of the additives in Comparative Example 4 is the same as that in Example 5, except that "sodium sulfite is not added and the amount of water is increased to make up the total amount".

[0052] The polyurethane foam formaldehyde removal additive of Comparative Example 4 comprises the following components by weight: 38.7% water, 23% dipropylene glycol, 2% high EO polyether, 4% L(+)-cysteine, 3% benzoyl hydrazine, 7% isoniazid, 5% sebacic acid dihydrazine, 7% succinic acid dihydrazine, 2% adipic acid dihydrazine, 8% 4,5-dihydroxy-2-imidazolium ketone, and 0.3% citric acid.

[0053] Comparative Example 5: The composition of the additive in Comparative Example 5 is the same as that in Example 5, except that "citric acid is not added and the amount of water is increased to make up the total amount".

[0054] The polyurethane foam formaldehyde removal additive of Comparative Example 5 comprises the following components by weight: 38.3% water, 23% dipropylene glycol, 2% high EO polyether, 4% L(+)-cysteine, 3% benzoyl hydrazine, 7% isoniazid, 5% sebacic acid dihydrazine, 7% succinic acid dihydrazine, 2% adipic acid dihydrazine, 8% 4,5-dihydroxy-2-imidazolium ketone, and 0.7% sodium sulfite.

[0055] Comparative Example 6: The composition of the additives in Comparative Example 6 is the same as that in Example 5, except that "dipropylene glycol and high EO polyether are not added, and the amount of water is increased to make up the total amount".

[0056] The polyurethane foam formaldehyde removal additive of Comparative Example 6 comprises the following components by weight: 63% water, 4% L(+)-cysteine, 3% benzoyl hydrazine, 7% isoniazid, 5% sebacic acid dihydrazine, 7% succinic acid dihydrazine, 2% adipic acid dihydrazine, 8% 4,5-dihydroxy-2-imidazolium ketone, 0.7% sodium sulfite, and 0.3% citric acid.

[0057] The preparation methods of the additives in Examples 2-5 and Comparative Examples 1-6 of this invention are the same as those in Example 1.

[0058] Application Example 1: Performance testing was conducted on the formaldehyde removal additive products obtained in Comparative Examples 1-6 and Examples 1-5: 1. Establishment of an odor assessment model and formaldehyde removal efficacy verification method for polyurethane foam: (1) Sample preparation and aldehyde source collection: The dehydrated polyether polyol provided by Costar (Zhejiang) Biotechnology Co., Ltd. was dehydrated by vacuum distillation to a water content of 1-3%.

[0059] (2) The formaldehyde removal additive is applied to the preparation of polyurethane foam. The steps are as follows: Take 10g of dehydrated polyether polyol, add 1% of the formaldehyde removal additive (i.e., 0.10 g) and 2% of the water (i.e., 0.20 g) of the polyether polyol by mass, and vortex mix for 15 min to obtain a mixture of polyether polyol. Take 5.15 g of the mixed polyether polyol and add 2 g of isocyanate. After stirring and mixing for 20 s, transfer it to a constant temperature forced-air drying oven and foam at 60 ℃ for 3.5 min to form the foam. Then transfer it to room temperature and let it stand for 140 min to obtain a polyurethane foam sample, which is marked as a sample with formaldehyde removal additive.

[0060] (3) Set up a blank control experiment to prepare polyurethane foam. The steps are as follows: Take 10g of dehydrated polyether polyol, add water (0.30g) accounting for 3% of the mass of polyether polyol, and vortex mix for 15 min to obtain a mixture of polyether polyol. Take 5.15g of the mixed polyether polyol and add 2g of isocyanate. After stirring and mixing for 20 s, transfer it to a constant temperature forced-air drying oven and foam at 60 ℃ for 3.5 min to form the foam. Then transfer it to room temperature and let it stand for 140 min. The obtained polyurethane foam sample is recorded as the blank control sample.

[0061] The evaluation methods for the performance testing of polyurethane foam samples prepared under different conditions are as follows: (1) Take a polyurethane foam sample that has been left to stand for 140 min, divide it into 16 small pieces and place them in a 5 L sampling bag. After washing the bag three times, fill it with 5 L of nitrogen and seal it.

[0062] (2) Place the sampling bag in an 80°C oven and heat for 2 hours. The aging conditions at 80°C are in accordance with VDA 276 standard to accelerate the release of aldehydes during the simulated foam use process.

[0063] (3) Put 5 mL of absorption liquid (phenol reagent solution) into the bubble absorption tube, and immediately after taking out the sampling bag, use the sampler to collect the gas in the sampling bag at a flow rate of 0.2 L / min. The gas collection volume is 5 L.

[0064] (4) The aldehyde content in 5 L of gas was determined by phenol reagent spectrophotometry, and the aldehyde removal rate of the polyurethane foam after adding the additive was calculated. The aldehyde content is expressed as the concentration of aldehydes in the gas in the sampling bag, in μg / m³. 3 The result was obtained quantitatively from the standard curve measured by the phenol reagent spectrophotometric method.

[0065] The formaldehyde removal rate is calculated using the following formula: Formaldehyde removal rate (%) = (Formaldehyde content in blank control sample test - Formaldehyde content in sample test with formaldehyde removal additive) / Formaldehyde content in blank control sample test × 100%.

[0066] The blank control sample was a polyurethane foam sample obtained by adding 3% water (by weight of polyether polyol) to polyether polyol without adding any formaldehyde removal additives.

[0067] The criteria for judging the foaming effect are as follows: visually observe the cell structure and appearance of the foam sample. A uniform cell structure without collapse or shrinkage is considered "normal". "Slightly soft" means that the foam indentation hardness is low, but still meets the lower limit requirement of the indentation hardness index of soft polyurethane foam in GB / T 10807-2006. "Basically normal" means that the cell structure is generally uniform, with a small number of coarse pores that do not affect the integrity of the foam structure. "Abnormal" or "collapsed" means that the foam shrinks or collapses significantly, and it is impossible to obtain a complete foam sample for aldehyde content testing.

[0068] The formaldehyde removal rate was the average of three experimental data, and the results are shown in Table 1. This test method refers to the VDA 276 standard. The foam sample was placed in a 5L FEP sampling bag and aged at 80 ℃ for 2 h before sampling and testing to ensure data comparability.

[0069] Table 1. Aldehyde content and aldehyde removal rate (average) of Comparative Examples 1-6 and Examples 1-5 .

[0070] Comparative Example 6 lacked auxiliary ingredients, resulting in solid precipitation in the additive system, which prevented the formation of a homogeneous liquid phase and did not meet the usage standards. Therefore, foaming tests and aldehyde content detection were not performed.

[0071] Although the foam obtained in Example 1 was slightly softer, it still met the lower limit requirement of the indentation hardness index for flexible polyurethane foam in GB / T 10807-2006. In Example 2, the formaldehyde removal rate could not be measured due to foam collapse. The cause of the collapse was insufficient foaming power due to a water content of only 24%, excessive use of aromatic hydrazide causing an overly rapid gelation reaction, and the catalytic effect of zirconium salt exacerbating the imbalance between the foaming and gelation reactions, ultimately leading to foam collapse.

[0072] The optimal embodiment 5 further enhances the formaldehyde removal rate to 96.73% through a balanced ratio of 4% L(+)-cysteine, 24% highly active acylhydrazine, 8% urea, and 38% water. In summary, this invention is not a simple combination of component dosages; its formaldehyde removal efficiency depends on a comprehensive balance of three factors: the type and activity of amino acids, the aliphatic / aromatic structure of the acylhydrazine, and the dosage of urea. Therefore, this invention achieves excellent synergistic formaldehyde removal effects by screening specific types of amino acids and highly active acylhydrazines and controlling the urea content to a specific level.

[0073] According to the single-factor comparison results of Example 5 and Comparative Examples 1-6 of the present invention (Table 1), each comparative example was based on the formulation of Example 5, with only the corresponding tested components missing and all other conditions being completely consistent: when acylhydrazides were missing, the formaldehyde removal rate decreased from 96.73% to 24.71% (a decrease of 72.02 percentage points); when amino acids were missing, it decreased to 50.13% (a decrease of 46.60 percentage points); when ureas were missing, it decreased to 56.65% (a decrease of 40.08 percentage points); when metal inorganic salts were missing, it decreased to 67.77% (a decrease of 28.96 percentage points); when organic acids were missing, it decreased to 80.64% (a decrease of 16.09 percentage points); when additives were missing, the additive system showed solid precipitation and could not be foamed; when all six components coexisted, the formaldehyde removal rate reached 96.73%.

[0074] The above results show that the absence of any functional component leads to a significant decrease in the formaldehyde removal rate or the failure of the additive system, proving that the present invention is not a simple superposition of the functions of each component, but achieves synergistic effect through a synergistic mechanism of "rapid capture-chemical anchoring-thermodynamic stabilization-catalytic acceleration-stable storage-molecular dispersion", and no single component can be replaced.

Claims

1. A formaldehyde removal additive for polyurethane foam, characterized in that, Based on weight percentage, it includes the following components: 3-6% amino acids, 6-25% acylhydrazides, 25-50% water, 20-45% auxiliaries, 0.5-2% inorganic metal salts, 5-15% urea compounds, and 0.3-1% organic acids.

2. The polyurethane foam formaldehyde removal additive as described in claim 1, characterized in that, Based on weight percentage, it includes the following components: amino acids 3-4%, acylhydrazides 9-24%, water 32-40%, auxiliaries 25-41%, inorganic metal salts 0.6-0.7%, urea compounds 8-14%, and organic acids 0.3-0.4%.

3. The polyurethane foam formaldehyde removal additive as described in claim 1, characterized in that, The amino acid is one or more of the following: D-aspartic acid, D-alanine, DL-leucine, DL-serine, L-lysine, L-arginine, L-histidine, L(+)-cysteine, and glycine.

4. The polyurethane foam formaldehyde removal additive as described in claim 1, characterized in that, The additive is one or more of dimethyl sulfoxide, dipropylene glycol, polyethylene glycol, ethylene glycol, and high EO polyether.

5. The polyurethane foam formaldehyde removal additive as described in claim 1, characterized in that, The inorganic metal salt is one or more of zinc chloride, zirconium chloride, sodium sulfite, and sodium thiosulfate.

6. The polyurethane foam formaldehyde removal additive as described in claim 1, characterized in that, The urea compound is one or more of 2-imidazolone, 4,5-dihydroxy-2-imidazolone, 4,5-dimethoxy-2-imidazolone, 1,3-dimethyl-2-imidazolone, and N-hydroxyethyl-2-imidazolone.

7. The polyurethane foam formaldehyde removal additive as described in claim 1, characterized in that, The organic acid is one or more of acetic acid, citric acid, tartaric acid, lactic acid, adipic acid, and gluconic acid.

8. The polyurethane foam formaldehyde removal additive as described in claim 1, characterized in that, Acylhydrazides are one or more of the following: acetylhydrazine, benzoylhydrazine, isophthalic acid hydrazine, caprylyl hydrazine, sebacic acid dihydrazine, succinic acid dihydrazine, adipic acid dihydrazine, and isoniazid.

9. The method for preparing a polyurethane foam formaldehyde removal additive as described in claim 1, characterized in that, Weigh the raw materials according to the formula, first dissolve the organic acid in water, then add the amino acid and stir until completely dissolved; then add the auxiliary agent and urea in sequence, heat to 40-45℃ and stir for 10-60 minutes; after cooling to 30±5℃, finally slowly add the acylhydrazine and metal inorganic salt, and stir until uniform and transparent.

10. The application of the polyurethane foam formaldehyde removal additive as described in claim 1 in the preparation of polyurethane foam, characterized in that, The raw material components include polyether polyol, isocyanate, and the additives mentioned above.