Low voc waterborne pu foam cushion and method of making same

Abstract

The present application relates to the technical field of waterborne polyurethane materials, and particularly relates to a low VOC waterborne PU foam pad and a preparation method thereof. The foam pad is formed by foaming and curing of a waterborne polyurethane dispersion, and two types of aldehyde-trapping sites are simultaneously introduced into the same porous framework, i.e. an amidoxime group formed by post-conversion of a nitrile group precursor by hydroxylamine, and an aminooxy group obtained by coupling and deprotection of T-BOC-aminooxy-diglycol-amino through a carboxyl anchoring site under an EDC and NHS activation system; and a water-dispersible blocked polyisocyanate crosslinking agent is used to form a crosslinking network by pyrolytic deblocking, so as to achieve rapid capture and durable retention of aldehydes such as formaldehyde and acetaldehyde under water washing and humid heat conditions, and simultaneously help to reduce VOC emission of the material.

Description

Technical Field

[0001] This invention belongs to the field of waterborne polyurethane materials technology, specifically relating to a low-VOC waterborne PU foam pad and its preparation method. Background Technology

[0002] Polyurethane foam is widely used in home furnishings, automobiles, and construction due to its advantages such as lightweight, resilience, cushioning, and ease of processing. With increasing demands for indoor air quality and odor control, the release of formaldehyde, acetaldehyde, and other aldehydes, as well as other volatile organic compounds (VOCs), from foam materials and their supporting systems during manufacturing or use has attracted attention. Current approaches to reducing aldehydes or VOCs mainly include: (1) Physical adsorption: such as adsorption by fillers like activated carbon and molecular sieves, but the adsorption capacity is limited and is significantly affected by humidity; (2) Added aldehyde scavengers: such as amines, hydrazines, hydroxylamines, aminooxygenated compounds, etc., which undergo addition or condensation with aldehydes. However, the added small molecules are at risk of migration, volatilization or water washing loss, resulting in insufficient persistence. (3) Reactive, covalent fixation: Introducing aldehyde-scavenging groups into the main chain or side chain to reduce migration, but single aldehyde scavenging mechanisms often have different reaction rates and capacities for different aldehydes, and the feasibility of aqueous system processes must also be taken into account; in addition, when using isocyanate crosslinking systems, nitrogen-containing active groups may be consumed by -NCO, resulting in a decrease in the effectiveness of aldehyde scavenging sites.

[0003] Therefore, there is an urgent need for an aqueous polyurethane foam pad that can achieve rapid and persistent capture of aldehydes without significantly introducing migratable small molecules or highly volatile solvents, and minimize the consumption of aldehyde-capturing sites during the cross-linking and curing stage. Summary of the Invention

[0004] The purpose of this invention is to provide a low-VOC waterborne PU foam pad and its preparation method, which solves the technical problems in the prior art such as easy migration of added aldehyde scavengers, water washing loss, easy consumption of aldehyde scavenging sites during the isocyanate crosslinking stage, and insufficient comprehensive removal effect of different aldehydes due to a single aldehyde scavenging mechanism.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a low-VOC waterborne PU foam pad, wherein the foam pad is a porous polyurethane material formed by foaming and curing a waterborne polyurethane dispersion, and the polyurethane material simultaneously possesses: a) Amide oxime group; b) An aminooxy (-ONH2) group is covalently fixed to the carboxyl anchoring point contained in the polyurethane material via amide bonds; and the foam pad further comprises a crosslinked network formed by the thermal desealing reaction of a water-dispersible blocking polyisocyanate crosslinking agent.

[0006] In the above process, two types of aldehyde-trapping channels are constructed within the same foam skeleton: an amamidoxime group obtained by the conversion of nitrile groups; and an aminooxy group obtained by covalent grafting and deprotection of carboxyl anchoring sites. Combined with the crosslinking network formed by blocking polyisocyanate crosslinking, the migration resistance and durability of aldehyde-trapping sites are improved. At the same time, the process sequence of protective crosslinking is adopted to reduce the risk of -NCO consuming nitrogen-containing aldehyde-trapping sites.

[0007] Preferably, the aminooxy group is obtained by grafting T-BOC-aminooxy-diethylene glycol-amino and removing the Boc protecting group.

[0008] Preferably, the carboxyl anchoring point originates from the carboxyl structure introduced by the internal emulsifying hydrophilic chain extender in the aqueous polyurethane dispersion.

[0009] Preferably, the crosslinking network is formed when the amino group of T-BOC-aminooxy-diethylene glycol-amino is in the Boc protected state, and after the crosslinking network is formed, the nitrile group is converted into an amamidoxime group and deprotected to obtain the amino group site.

[0010] Preferably, the low-VOC waterborne PU foam pad is prepared from a waterborne polyurethane foam base pad containing carboxyl anchoring points and built-in nitrile precursor sites through subsequent grafting, crosslinking locking, nitrile post-conversion, and deprotection.

[0011] Preferably, the preparation method of the foam base pad is as follows: take the formaldehyde-scavenging polyurethane dispersion, add nonionic surfactant, foaming surfactant and thickener, adjust the pH to 8.0-9.0, disperse and foam at high speed and stabilize the cell at low speed, scrape the foam slurry and pre-cur it under heating conditions, and repeat the coating and stacking to the required thickness to obtain the foam base pad.

[0012] Preferably, the method for preparing the aldehyde-scavenging polyurethane dispersion is as follows: reacting polyether glycol, diisocyanate, internal emulsifying hydrophilic chain extender and catalyst under heating conditions to obtain a terminal NCO prepolymer; neutralizing the carboxyl group with an organic base and then dispersing in water; subsequently adding the nitrile glycol solution to carry out a chain extension reaction to obtain an aldehyde-scavenging polyurethane dispersion with a solid content of 40-50 wt%.

[0013] In the above process, the NCO content of the prepolymer was determined by the dibutylamine-hydrochloric acid back titration method; when the NCO content reached the theoretical value ±0.2wt%, the neutralization and dispersion step was initiated; after chain expansion, the residual NCO was confirmed to be ≤0.1wt% by the back titration method.

[0014] Preferably, the method for preparing the nitrile glycol solution is as follows: 10.0g of nitrile glycol is dissolved in a mixed solvent of 30.0g of acetone and 10.0g of water, and stirred at 35°C until clear to obtain the nitrile glycol solution.

[0015] Preferably, the preparation method of the nitrile glycol is as follows: under dry and nitrogen protection conditions, diethanolamine is dissolved in anhydrous dichloromethane, triethylamine is added at 0-5°C, and then a dichloromethane solution of 2-cyanoacetyl chloride is added dropwise. After the addition is completed, the mixture is raised to room temperature for reaction; the nitrile glycol is obtained by filtration to remove salt, concentration under reduced pressure, and recrystallization.

[0016] In the above process, 2-cyanoacetyl chloride undergoes acyl chloride amination with diethanolamine at low temperature to generate an amide structure, yielding a diol monomer containing amide, nitrile, and dihydroxyl groups, which provides a structural basis for the subsequent introduction of nitrile precursor sites as a polyurethane chain extender.

[0017] Through the above technical solutions, the carboxyl groups introduced by the internal emulsifying hydrophilic chain extender (DMPA) in the aldehyde-scavenging polyurethane dispersion form an internal emulsion structure after neutralization and retain the carboxyl anchoring sites after curing; the nitrile glycol, as a diol chain extender, reacts with the terminal NCO group to enter the main chain, realizing the covalent integration of the nitrile precursor sites from the source, thereby reducing the migration risk of the added small molecule aldehyde scavenger.

[0018] Preferably, the nonionic surfactant is selected from at least one of fatty alcohol polyoxyethylene ethers, alkyl glycosides (APG), or polysorbates.

[0019] Preferably, the foaming surfactant is selected from at least one of sodium dodecyl sulfate (SLS), sodium dodecyl ether sulfate (SLES), α-olefin sulfonate (AOS), or betaine-based amphoteric surfactants.

[0020] Preferably, the thickener is selected from at least one of polyurethane associative thickeners (HEUR), alkali-swellable thickeners (HASE), or cellulose ether thickeners (HEC).

[0021] Secondly, the present invention also provides a method for preparing a low-VOC waterborne PU foam pad, comprising the following steps: Step (1) The polyurethane foam base pad containing carboxyl anchoring points and nitrile precursor sites is activated with EDC and NHS system under acidic conditions, and then transferred into coupling solution containing T-BOC-aminooxy-diethylene glycol-amino. The coupling reaction is carried out under neutral to weakly alkaline conditions to form amide bonds with the carboxyl groups to obtain the aminooxy-coated pad. Step (2) The protective ammonia pad is immersed in a water-dispersible blocking polyisocyanate crosslinking agent solution, dried to remove water, and then heated to the unblocking temperature range to crosslink it, thus obtaining a crosslinked locking pad; Step (3) The cross-linked locking pad is immersed in hydroxylamine hydrochloride solution and the system is adjusted to weak alkalinity to convert the nitrile group into an amamidoxime group. After washing and drying, a dual-channel pad is obtained. Step (4) The dual-channel pad is treated under acidic conditions to remove the Boc protective group, washed until neutral and dried to obtain a low-VOC waterborne polyurethane foam pad.

[0022] Preferably, in step (1), the pH for carboxyl activation is 4.5-6.0, the temperature is 20-40℃, and the time is 20-60 min; the pH for coupling reaction is 7.0-8.0, the temperature is 20-40℃, and the time is 0.5-4 h.

[0023] Preferably, in step (2), the amount of crosslinking agent used is such that the NCO:OH equivalent ratio is 0.05-0.15 on a solid basis, the heat treatment temperature is 110-160℃, and the time is 5-40min.

[0024] Preferably, the water-dispersible blocking polyisocyanate crosslinking agent in step (2) is a water-based blocked aliphatic polyisocyanate, whose isocyanate skeleton is preferably derived from HDI trimer curing agent or adipisocyanate biuret, and is formed into a water dispersion through blocking and hydrophilic modification.

[0025] Preferably, in step (2), the water-dispersible blocking polyisocyanate crosslinking agent can be selected from products with a deblocking temperature of 110-160℃; the heat treatment temperature is within the range of the deblocking temperature to 30℃ higher than the deblocking temperature, and the heat treatment time is 5-40min; after heat treatment and deblocking, post-drying is carried out under ventilation conditions to promote the dissipation of the blocking agent and its volatile by-products, and reduce the residual odor and VOC risk of the material.

[0026] Preferably, in step (3), the concentration of hydroxylamine hydrochloride solution is 3-10 wt%, the solvent is a mixture of ethanol and water, the volume ratio of ethanol to water is 0:1-3:1, the pH is 8.0-9.0, the reaction temperature is 40-60℃, and the time is 1-4h.

[0027] Preferably, in step (4), the acid treatment uses anhydrous HCl alcohol solution or aqueous HCl alcohol solution, with an acid concentration of 0.05-1.0 mol / L, a temperature of 20-40℃, and a time of 5-60 min.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The waterborne PU foam pad of the present invention achieves a more balanced rate and capacity for aldehyde capture through dual-channel synergistic aldehyde capture: two types of aldehyde capture sites are simultaneously constructed within the same porous waterborne polyurethane skeleton: an amamidoxime group formed by the conversion of nitrile groups after hydroxylamine, and an aminooxy group (-ONH2) that is covalently grafted and released after deprotection in a carbodiimide (EDC) and active ester (NHS) activation system through a carboxyl anchoring site. The two mechanisms complement each other, improving the comprehensive removal capacity of aldehydes such as formaldehyde and acetaldehyde.

[0029] 2. The water-based PU foam pad of the present invention has better durability due to covalent fixation, which reduces migration and loss: the aminooxygen precursor is covalently fixed by forming amide bonds through the carboxyl anchoring point, which significantly reduces the risk of migration, volatilization or water washing loss of aldehyde-trapping components during use, which helps to maintain long-term effectiveness and reduce odor and VOC hazards.

[0030] 3. The water-based PU foam pad of the present invention introduces a water-dispersible blocking polyisocyanate crosslinking agent to form a crosslinking network through thermal desealing, which plays a structural locking role on the foam skeleton, improves the stability of water washing resistance, damp heat aging resistance and deformation recovery, and helps to stably retain functional sites in the skeleton.

[0031] 4. The waterborne PU foam pad of the present invention reduces the consumption of sites by protective crosslinking and improves the utilization rate of effective sites: crosslinking is completed when the amino group is in the Boc protected state, which can reduce the side reaction consumption of nitrogen-containing aldehyde-scavenging sites by the -NCO generated during unsealing. After crosslinking, the nitrile group is converted and deprotected, ensuring that the aldehyde-scavenging sites are generated last and more are retained, thereby improving the number and utilization rate of effective sites.

[0032] 5. The overall route of the waterborne PU foam pad of the present invention is based on the foaming of waterborne polyurethane dispersion, and functionalization is achieved by combining impregnation grafting, post-conversion, and deprotection steps, reducing the dependence on the introduction of migratable small molecule aldehyde scavengers, and taking into account both process feasibility and the demand for low VOC emissions. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a process flow diagram of the preparation process of the low-VOC waterborne PU foam pad of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0036] Terminology and Raw Material Description: Nitrile glycol: It is obtained by amination of 2-cyanoacetyl chloride and diethanolamine chloride. It contains amide, nitrile and dihydroxy structures and can be used as a chain extender to introduce nitrile precursor sites into the polyurethane backbone.

[0037] Carboxyl anchoring sites: derived from carboxyl groups introduced by internal emulsifying hydrophilic chain extenders, which form internal emulsification structures after neutralization and retain reactive carboxyl sites after curing, for use in EDC and NHS grafting.

[0038] T-BOC-aminooxy-diethylene glycol-amino: A compound containing Boc protecting the aminooxy group and the terminal primary amine. The primary amine is used to form an amide bond with the activated carboxyl group. After acid removal of Boc, the -ONH2 aldehyde-trapping site is released.

[0039] The amide oxime group is formed by the reaction of a nitrile precursor site introduced into the polyurethane chain with hydroxylamine; the nitrile precursor site can be covalently introduced into the main chain by participating in the chain extension reaction with a nitrile-containing diol chain extender.

[0040] The water-dispersible blocking polyisocyanate crosslinking agent is a water-based blocked aliphatic polyisocyanate. Its isocyanate backbone is preferably derived from HDI trimer curing agents or adipamide biuret, and is formed into an water dispersion through blocking and hydrophilic modification. The blocking isocyanate is deblocked by heating to form a crosslinked network; upon heating to the deblocking temperature, it releases -NCO and reacts with active hydrogen groups such as -OH in the material to form a crosslinked network.

[0041] The amount of crosslinking agent used is converted into NCO equivalent based on the blocked NCO content (mass fraction wNCO) given in the crosslinking agent product information: ; The reactive hydroxyl equivalent (EOH) in the foam base can be calculated based on the theoretical hydroxyl equivalent of the aldehyde-trapping polyurethane dispersion formulation; the ENCO / EOH ratio can be adjusted to 0.05-0.15 by adjusting the amount of solid crosslinking agent introduced. Example 1

[0042] This embodiment discloses a method for preparing nitrile diol, including the following steps: Under dry and nitrogen-protected conditions, 31.5 g of diethanolamine and 200 mL of anhydrous dichloromethane were mixed, cooled to 3 °C in an ice bath, and then 25 g of triethylamine was added dropwise while stirring for 10 min. Then, 25 g of 2-cyanoacetyl chloride was dissolved in 50 mL of dichloromethane and added dropwise at 3 °C for 30 min. After the addition was completed, the temperature was raised to 25 °C and stirring was continued for 3 h. The salt was removed by filtration, and the filtrate was concentrated under reduced pressure and recrystallized from ethyl acetate to obtain nitrile glycol. Example 2

[0043] This embodiment discloses a method for preparing an aldehyde-scavenging polyurethane dispersion, including the following steps: Add 200g of polyether glycol (Mn≈1000), 113g of isophorone diisocyanate (IPDI), 20g of dimethylolpropionic acid (DMPA), and 0.05g of dibutyltin dilaurate (DBTDL) to a 1L reactor and react at 80℃. Monitor the NCO content of the prepolymer using the dibutylamine-hydrochloric acid back-tipping method. When the NCO content reaches the theoretical value of 3.8-4.2wt%, proceed to the neutralization and dispersion step. Then add 50mL of acetone to reduce viscosity and lower the temperature to 50℃. 14g of triethylamine was added to neutralize and obtain the prepolymer. The prepolymer was then slowly added to 600mL of deionized water under shear at 1000rpm for dispersion. Subsequently, 50g of nitrile glycol solution was added for chain extension for 45min. After chain extension, a sample was taken and immediately added to acetone containing excess dibutylamine for blocking. The residual NCO was then calculated by back-titration with hydrochloric acid standard solution, confirming that the residual NCO ≤ 0.1wt%. Finally, acetone was removed under reduced pressure to constant weight, yielding an aldehyde-scavenging polyurethane dispersion with a solid content of 46wt%.

[0044] The method for preparing the nitrile glycol solution is as follows: 10g of nitrile glycol is dissolved in a mixed solvent of 30g of acetone and 10g of water, and stirred at 35°C until clear to obtain the nitrile glycol solution. Example 3

[0045] This embodiment discloses a method for preparing a foam base pad, including the following steps: Mix 300g of aldehyde-scavenging polyurethane dispersion, 4.05g of fatty alcohol polyoxyethylene ether AEO-9, 5.4g of SLS, and 1.49g of HEUR. Then adjust the pH to 8.5 with ammonia. Disperse the mixture at high speed of 3000rpm to achieve the target foaming ratio of 3.5:1, and then stabilize the foam cells at low speed of 1000rpm. Coat the foaming slurry onto release paper to a wet film thickness of 500μm and pre-cur it at 130℃ for 10min. Repeat the coating and layering until the dry film thickness is 3mm to obtain the foam base.

[0046] The target expansion ratio is 3.5:1 (volume after foaming / volume before foaming). Example 4

[0047] This embodiment discloses a method for preparing a low-VOC waterborne PU foam pad, including the following steps: Step (1) The foam pad obtained in Example 3 was immersed in a mixed solution of ethanol and water in a volume ratio of 1:1. 0.15 mol / L 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and 0.1 mol / L NHS were added to adjust the pH of the solution to 5.5. The solution was reacted at 30°C for 40 min to activate the carboxyl groups. After the activated foam pad was removed and drained, it was immediately transferred to a coupling solution of ethanol and water in a volume ratio of 1:1. The coupling solution contained 0.05 mol / L LT-BOC-aminooxy-diethylene glycol-amino. Triethylamine was added to adjust the pH to 7.5. The solution was reacted at 30°C with slight shaking or slow stirring for 2 h. After the reaction, the pad was thoroughly washed with ethanol, water and deionized water in sequence and dried at 50°C to obtain the protective aminooxygen pad.

[0048] In the above process, EDC activates the carboxyl group and forms an amide bond with the primary amine, and NHS is used to stabilize the intermediate, thereby enabling the terminal primary amine of the compound molecule to form an amide bond with the carboxyl group of the cushion, achieving covalent fixation of the aminooxy group precursor; at the same time, the aminooxy group exists in the Boc protected state, which can reduce the risk of side reactions during coupling and subsequent crosslinking that consume aldehyde scavenging sites.

[0049] Step (2) Dilute the water-dispersible blocking polyisocyanate crosslinking agent Covestro Imprafix 2794 with deionized water to a crosslinking agent solid content of 10 wt%; add the crosslinking agent in solid form to make the NCO:OH equivalent ratio 0.1; immerse the protective ammonia pad in the solution for 2 min and then roll it to make the wet pick-up rate 80%; then dry it at 60°C to constant weight (the amount of crosslinking agent solids carried in is determined by the dry weight gain); heat treat it at 130°C for 20 min to deblock the crosslinking agent and form a crosslinking network; and then dry it at 80°C under ventilation for 50 min to obtain the crosslinked locking pad.

[0050] In the above process, cross-linking is completed while the amino group is still in the Boc protected state, which can reduce the risk of -NCO consuming nitrogen-containing aldehyde scavenging sites.

[0051] Step (3) Immerse the cross-linked locking pad in a 7wt% hydroxylamine hydrochloride solution, adjust the pH to 8.5 with sodium bicarbonate, and keep it at 50°C for 2 hours; after taking it out, wash it thoroughly with deionized water and dry it at 50°C to constant weight to obtain a dual-channel pad.

[0052] The solvent for the hydroxylamine hydrochloride solution is a mixture of ethanol and water in a 1:1 volume ratio.

[0053] In the above process, hydroxylamine undergoes nucleophilic addition to the nitrile group and forms an amoxime functional group via proton transfer; after the cross-linked network is formed, the nitrile group can still be converted by impregnation-diffusion. If necessary, the conversion degree can be increased by extending the holding time or increasing the concentration of hydroxylamine.

[0054] Step (4) Immerse the dual-channel pad in an ethanol solution of 0.3 mol / L HCl and treat it at 30°C for 30 min to remove the protection; then wash it with water until neutral and dry it at 50°C to obtain a low-VOC waterborne PU foam pad.

[0055] In the above process, acidic conditions remove the Boc protecting group and release the -ONH2 site, thereby restoring its ability to undergo addition-dehydration with aldehydes to form oxime bonds. Example 5

[0056] The difference between this embodiment and embodiment 4 is that the coupling system in step (1) uses an aqueous buffer system: The foam pad was immersed in 2-(N-morpholine) ethanesulfonic acid buffer solution with pH 5.5, and 0.15 mol / L LEDC·HCl and 0.10 mol / L N-hydroxysulfosuccinimide sodium salt were added. After activation for 35 min, it was transferred to a solution containing 0.05 mol / L LT-BOC-aminooxy-diethylene glycol-amino and a water and ethanol mixture of triethylamine was added to adjust the pH to 7.5. The reaction was carried out for 2 h, and the pad was washed and dried to obtain the ammonia-oxygenated pad. Then, the steps (2)-(4) of Example 4 were followed to obtain the low VOC waterborne PU foam pad. Example 6

[0057] The difference between this embodiment and embodiment 4 lies in the heat treatment conditions in step (2). In step (2), after the protective ammonia pad is immersed in the water-dispersible blocking polyisocyanate crosslinking agent solution described in embodiment 4, it is dried at 60°C to remove water, and then heat-treated at 140°C for 30 minutes to complete the unblocking and crosslinking, thus obtaining the crosslinked locking pad; the remaining steps are the same as in embodiment 4.

[0058] Comparative Example 1 Compared with Example 4, Comparative Example 1 did not introduce nitrile glycol and did not perform aminooxygen precursor grafting, and ordinary PUD foam pads were prepared, with all other conditions being the same.

[0059] Comparative Example 2 Compared with Example 4, Comparative Example 2 did not perform step (1) aminooxy precursor grafting and step (4) deprotection, but only nitrile group conversion and crosslinking lock, with the other conditions being the same.

[0060] Comparative Example 3 Compared with Example 4, Comparative Example 3 did not perform the nitrile group conversion in step (3), but only performed aminooxyl precursor grafting, crosslinking locking and deprotection, with the other conditions being the same.

[0061] Comparative Example 4 Compared with Example 4, Comparative Example 4 did not perform step (2) crosslinking lock, but only performed aminooxyl precursor grafting, nitrile group conversion and deprotection, with the other conditions being the same.

[0062] Comparative Example 5 Compared with Example 4, Comparative Example 5 advances the deprotection step (4) to before step (2), that is, acid deprotection Boc release-ONH2 is performed before crosslinking and locking, and then the blocking polyisocyanate crosslinking and locking is performed; the other conditions are the same.

[0063] Comparative Example 6 Compared with Example 4, Comparative Example 6 did not use the EDC / NHS activation system. Instead, the foam pad was immersed in an ethanol / water solution containing T-BOC-aminooxy-diethylene glycol-amino for the same amount of time, washed and dried, and then treated according to steps (2)-(4) of Example 4. All other conditions were the same.

[0064] Test method: Under conditions of 23°C and 50%RH, the aqueous PU foam pads prepared in Examples 4-6 and Comparative Examples 1-6 were placed in a sealed chamber, and formaldehyde gas or a mixture of formaldehyde and acetaldehyde gas at a predetermined initial concentration was introduced. Gas samples were taken at predetermined time points, and the changes in aldehyde concentration were determined using the DNPH derivatization-HPLC method. For ease of comparison of unit mass, the following calculation method was used: Let the volume of the cabin be V (m). 3 The sample mass is m (g), and the initial concentration is C0 (mg / m). 3 The concentration at time t is Ct (mg / m³). 3 Then, the aldehyde capture capacity per unit mass is:

[0065] Given the chamber volume and initial challenge concentration, the theoretical upper limit of Qm is C0×V / m (reached when Ct approaches 0). Therefore, this method characterizes the sample's unit mass capture capability under a given challenge amount.

[0066] Example 4 and some comparative examples were selected as representative samples for comparison in the mixed aldehyde challenge and durability evaluation.

[0067] Durability evaluation: The above tests were repeated after the samples were washed with water and subjected to damp heat aging. Calculate the retention rate = (Qm after treatment / initial Qm) × 100%.

[0068] Standardized testing conditions: Volume of the sealed chamber: V=0.5m 3 Foam pad sheet weight m=5g (thickness approximately 3mm); Formaldehyde single-component challenge: CO=50mg / m 3 Formaldehyde and acetaldehyde mixed challenge: Formaldehyde CO = 30 mg / m³ 3 Acetaldehyde CO = 30 mg / m³ 3Sampling time: 1h, 4h, 24h; n=3 for each data point, and the table shows the mean.

[0069] Low VOC / FOG refers to samples exhibiting low emission levels when tested using the thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS, e.g., VDA278) method. The VDA278 method distinguishes and quantifies VOCs and FOGs, with VOCs typically corresponding to nC. 25 For volatile components at and below, FOG typically corresponds to nC. 14 -nC 32 The range of condensable components. Low VOC / FOG further refers to VOC and FOG values ​​measured by the VDA278 thermal desorption method falling within the low emission target range commonly used in automotive interior materials.

[0070] Table 1 Formaldehyde capture performance

[0071] Qm24h press calculate.

[0072] Table 2. Formaldehyde and acetaldehyde combined capture (C0=30 / 30mg / m³) 3 (n=3)

[0073] The total Qm24h is calculated by summing the concentration decreases of the two aldehydes over 24 hours and then substituting the sums into the same formula:

[0074] Table 3 Durability (Formaldehyde single component, Qm24h, n=3)

[0075] Recommended washing conditions: Immerse in 40℃ deionized water for 30 minutes each time, changing the water each time; test after drying to constant weight. Recommended humidity and heat conditions: Place at 60℃ and 90%RH for 72 hours, then test after restoring to 23℃ and 50%RH.

[0076] Table 4. Stability of Crosslinked Structures

[0077] Table 5 VOC / FOG (VDA278, unit: mg / kg)

[0078] As shown in Tables 2 and 3, Example 4 exhibits superior overall removal capabilities under both single-component formaldehyde and mixed formaldehyde and acetaldehyde challenges, demonstrating a significant advantage over Comparative Examples 2 and 3, which only utilize a single channel, showcasing the synergistic effect of dual channels. Table 4 shows that Comparative Example 6, with an initial formaldehyde capture rate close to that of Example 4, exhibits a significant decrease in retention rate after water washing and wet heat treatment, indicating that physical adsorption alone is insufficient to achieve a durable effect. Example 4, through covalent fixation of carboxyl anchoring sites combined with crosslinking locking, significantly improves durability retention. A comparison between Comparative Example 4 and Example 4 demonstrates that the crosslinking network significantly contributes to durability retention and structural stability. A comparison between Comparative Example 5 and Example 4 shows that deprotection and release of -ONH2 before crosslinking reduces effective formaldehyde capture sites, thereby decreasing the initial formaldehyde capture capacity, verifying the significance of the protected crosslinking sequence for site protection. Table 5 shows that Examples 4-6 achieve both high-efficiency formaldehyde capture and durability retention while maintaining low VOC / FOG emission levels, demonstrating the comprehensive advantages of this material system in terms of performance and low emissions.

[0079] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. 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 better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A water-based PU foam mat, characterized in that, The foam pad is a porous polyurethane material formed by foaming and curing an aqueous polyurethane dispersion. The polyurethane material simultaneously possesses: a) Amide oxime group; b) An aminooxy (-ONH2) group is covalently fixed to the carboxyl anchoring point contained in the polyurethane material via amide bonds; and the foam pad further comprises a crosslinked network formed by the thermal desealing reaction of a water-dispersible blocking polyisocyanate crosslinking agent.

2. The water-based PU foam pad according to claim 1, characterized in that, The aminooxy group is obtained by grafting T-BOC-aminooxy-diethylene glycol-amino and removing the Boc protecting group.

3. The water-based PU foam pad according to claim 1 or 2, characterized in that, The carboxyl anchoring point originates from the carboxyl structure introduced by the internal emulsifying hydrophilic chain extender in the waterborne polyurethane dispersion.

4. The water-based PU foam pad according to claim 2, characterized in that, The aminooxy group is covalently fixed in the following manner: the carboxyl group at the carboxyl anchoring site reacts with the terminal primary amine of T-BOC-aminooxy-diethylene glycol-amino group in an activation system of carbodiimide (EDC) and N-hydroxysuccinimide (NHS) or its water-soluble salt to form an amide bond.

5. The water-based PU foam pad according to claim 1, characterized in that, The deblocking temperature of the water-dispersible blocking polyisocyanate crosslinking agent is 110-160℃, the heat treatment temperature is within the range of the deblocking temperature to 30℃ higher than the deblocking temperature, and the heat treatment time is 5-40min.

6. The water-based PU foam pad according to claim 1, characterized in that, When a cross-linked network is formed, the NCO:OH equivalent ratio is 0.05-0.

15.

7. A method for preparing the water-based PU foam pad according to claim 1, characterized in that, Includes the following steps: Step (1) The polyurethane foam base pad containing carboxyl anchoring points and nitrile precursor sites is activated with EDC and NHS system under acidic conditions, and then transferred into coupling solution containing T-BOC-aminooxy-diethylene glycol-amino. The coupling reaction is carried out under neutral to weakly alkaline conditions to form amide bonds with the carboxyl groups to obtain the aminooxy-coated pad. Step (2) The protective ammonia pad is immersed in a water-dispersible blocking polyisocyanate crosslinking agent solution, dried to remove water, and then heated to the unblocking temperature range to crosslink it, thus obtaining a crosslinked locking pad; Step (3) The cross-linked locking pad is immersed in hydroxylamine hydrochloride solution and the system is adjusted to weak alkalinity to convert the nitrile group into an amamidoxime group. After washing and drying, a dual-channel pad is obtained. Step (4) The dual-channel pad is treated under acidic conditions to remove the Boc protective group, washed until neutral and dried to obtain an aqueous PU foam pad.

8. The method according to claim 7, characterized in that, In step (1), the pH for activating the carboxyl group is 4.5-6.0, the temperature is 20-40℃, and the time is 20-60 min; the pH for the coupling reaction is 7.0-8.0, the temperature is 20-40℃, and the time is 0.5-4 h.

9. The method according to claim 7 or 8, characterized in that: In step (2), the amount of crosslinking agent used is based on solids, so that the NCO:OH equivalent ratio is 0.05-0.15, the heat treatment temperature is 110-160℃, and the time is 5-40min; in step (3), the concentration of hydroxylamine hydrochloride solution is 3-10wt%, the solvent is a mixture of ethanol and water, the volume ratio of ethanol to water is 0:1-3:1, the pH is 8.0-9.0, the reaction temperature is 40-60℃, and the time is 1-4h; in step (4), the acid treatment is carried out using anhydrous HCl alcohol solution or aqueous HCl alcohol solution, the acid concentration is 0.05-1.0mol / L, the temperature is 20-40℃, and the time is 5-60min.

10. The method according to any one of claims 7-9, characterized in that, The polyurethane foam base pad is obtained by foaming and curing an aqueous polyurethane dispersion containing carboxyl anchoring points and nitrile precursor sites. The carboxyl anchoring points are derived from the carboxyl structure introduced by the internal emulsifying hydrophilic chain extender dimethylolpropionic acid (DMPA), and the nitrile precursor sites are derived from nitrile glycol participating in the chain extension reaction as a diol chain extender and being covalently introduced into the polyurethane backbone. The aqueous polyurethane dispersion is foamed and cured to form a porous foam to obtain the polyurethane foam base pad.

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