A low odor, low cytotoxicity, high performance polyurethane sponge and a method for making the same

Abstract

The application discloses a low-odor low-cytotoxicity high-performance polyurethane sponge and a preparation method thereof, and relates to the field of foamed materials.The method comprises the following steps: first, synthesizing isocyanate group terminated prepolymer and special polyester polyol; and then, mixing and foaming the synthesized isocyanate group terminated prepolymer and the special polyester polyol to prepare the low-odor low-cytotoxicity high-performance polyurethane sponge.The low-odor low-cytotoxicity high-performance polyurethane sponge prepared by the method has lower odor and cytotoxicity than existing traditional polyurethane sponges, and has more excellent mechanical properties, more delicate cells, higher fire peel force than polyether type polyurethane sponges, and is closer to polyester type polyurethane sponges in mechanical properties, cell diameters and fire peel force, and is closer to polyether type polyurethane sponges in resilience and hydrolysis resistance, and is very suitable for being used as the development direction of the next generation of polyurethane sponges.

Description

Technical Field

[0001] This invention relates to the field of foaming materials technology, and more specifically, to a low-odor, low-cytotoxic high-performance polyurethane foam and its preparation method. Background Technology

[0002] Several industry challenges have long existed in the polyurethane foaming field, namely, the yellowing problem of aromatic polyurethane foam, the odor problem of polyurethane foam, the emission of aldehydes (especially formaldehyde) from polyurethane foam, the poor hydrolysis resistance of polyester polyurethane foam, the poor resilience of polyester polyurethane foam, and the cytotoxicity problem of polyurethane foam.

[0003] During the application of polyurethane foam, especially in enclosed environments such as automobiles and rooms, the odor emitted by polyurethane foam can be very unpleasant and, over time, may even affect the health of consumers. The odor of polyurethane foam mainly originates from three sources: first, the emission of amine catalysts from the polyurethane foam foaming formula; second, the emission of unreacted residual toluene diisocyanate from the foaming formula (toluene diisocyanate is generally in excess during polyurethane foaming, and because of its low vapor pressure, it evaporates quickly); and third, the production of small molecule aldehydes and other small molecules due to side reactions caused by the inability of heat to dissipate quickly from the foam core during the foaming process (during foaming, a dense skin layer forms on the top, bottom, and sides of the foam). Among these, the emission of amine catalysts is the most significant cause, resulting in an amine-like odor characteristic of polyurethane foam.

[0004] The biggest problem facing polyurethane foam in the application of cosmetics, personal care, sports protection and medical devices is that it fails the cytotoxicity test, which seriously affects the application and promotion of polyurethane foam. There are two main reasons for this: one is the irritation caused by the catalyst in the foaming formula, and the other is the irritation caused by the unreacted residual toluene diisocyanate in the foaming formula.

[0005] Based on the root causes of the odor problem and the failure to pass the cytotoxicity test in polyurethane foam, it seems that solving these problems could be achieved by removing the catalyst from the foaming formula and reducing the residue of toluene diisocyanate. However, removing the catalyst from the foaming formula would severely affect the foaming process, preventing the production of a normal polyurethane foam. This is mainly because the reaction rate constants of the isocyanate groups with the alcohol hydroxyl groups and the isocyanate groups with water are both relatively small, resulting in a slow reaction rate. The catalytic effect of the catalyst can accelerate the reaction rate; the absence of the catalyst will slow down the reaction rate, making it impossible to obtain a normal polyurethane foam. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing low-odor, low-cytotoxic, high-performance polyurethane foam. Compared with the traditional polyurethane foam (including polyester-type polyurethane foam and polyether-type polyurethane foam) preparation methods, this method eliminates the catalysts (mainly amine catalysts and metal tin catalysts) that are essential in the traditional polyurethane foam foaming formulation, thereby reducing the residual toluene diisocyanate (TDI) in the resulting polyurethane foam.

[0007] Another objective of this invention is to provide a low-odor, low-cytotoxicity, high-performance polyurethane foam prepared by the aforementioned method. The low-odor, low-cytotoxicity, high-performance polyurethane foam prepared by this invention has lower odor and cytotoxicity compared to existing traditional polyurethane foams on the market, including polyester-type polyurethane foams and polyether-type polyurethane foams. Compared to polyether-type polyurethane foams, it has superior mechanical properties, finer pores, and higher fire-resistant peel strength. Its mechanical properties, pore size, and fire-resistant peel strength are closer to those of polyester-type polyurethane foams, and its resilience and hydrolysis resistance are close to those of polyether-type polyurethane foams. It is very suitable as a development direction for the next generation of polyurethane foams.

[0008] To achieve the above objectives, the present invention employs the following technical measures: The first aspect of this invention provides a method for preparing a low-odor, low-cytotoxic, high-performance polyurethane foam, comprising the following steps: (1) Preparation of isocyanate-terminated prepolymer: The isocyanate-terminated prepolymer is prepared by reacting polyethylene glycol and toluene diisocyanate TDI-65. The isocyanate group content (NCO value) of the prepared isocyanate-terminated prepolymer is 10% ~ 25%; (2) Preparation of special polyester polyols: Special polyester polyols are prepared by reacting diacids, catalysts, crosslinking agents with one or more small molecule diols or polyether polyols with ether bonds in their molecular structure. The hydroxyl value is 50 ~ 80 mg KOH / g and the functionality is 2.0 ~ 2.7. (3) Preparation of low-odor, low-cytotoxic high-performance polyurethane foam: The low-odor, low-cytotoxic high-performance polyurethane foam includes two components, A and B. Component A includes a special polyester polyol, amino-terminated polyether, foaming agent and surfactant; Component B includes isocyanate-terminated prepolymer; wherein, the amount of component B is as follows: the ratio of the total molar amount of isocyanate groups in component B to the sum of the total molar amounts of the hydroxyl groups of all special polyester polyols and foaming agents and the primary amino groups of amino-terminated polyethers in component A is 1.0 to 1.1.

[0009] In one embodiment, in step 1) the preparation of the isocyanate group-terminated prepolymer, the polyethylene glycol is one or more of PEG200, PEG400, PEG600, PEG1000, PEG1500, and PEG2000.

[0010] Preferably, the polyethylene glycol is PEG600 with a molecular weight of 600; the mass ratio of toluene diisocyanate to polyethylene glycol is (63 ~ 168):100.

[0011] In one embodiment, in step (1) the preparation of the isocyanate-terminated prepolymer, PEG600 is first dehydrated using a rotary evaporator at 120°C / -0.09MPa until the water content is below 300ppm; then, a certain amount of the dehydrated PEG600 is added to a four-necked flask, and the flask is placed in an oil bath to cool down; after the temperature of the PEG600 in the four-necked flask drops below 40°C, toluene diisocyanate is added in proportion, and under nitrogen protection, the speed of the cantilever stirrer is adjusted to 100~300rpm for stirring and mixing for 0.5 hours; then, the temperature of the heat transfer oil in the oil bath is heated to 85°C, so that the temperature of the mixture in the four-necked flask rises to 80~ The mixture was stirred at 83°C for 4 hours. Then the NCO value of the mixture was tested every hour until the error between two consecutive test values ​​was within 5%, at which point the prepolymerization reaction was considered complete. The average of the two consecutive NCO test values ​​was the NCO value of the isocyanate group-terminated prepolymer.

[0012] In one implementation, in step (2) the preparation of the special polyester polyol, the special polyester polyol is prepared by reacting a dicarboxylic acid, a catalyst, a crosslinking agent and a polyether polyol.

[0013] Preferably, the polyether polyol is polyethylene glycol PEG200.

[0014] Preferably, the special polyester polyol is prepared by reacting adipic acid, tetrabutyl titanate catalyst, trimethylolpropane crosslinking agent and polyethylene glycol PEG200; wherein the molar ratio of hydroxyl to carboxyl groups is (1.1 ~ 1.4):1.

[0015] In one embodiment, in step (2) of preparing the specific polyester polyol, adipic acid, trimethylolpropane, polyethylene glycol PEG200, and tetrabutyl titanate are added to a reaction vessel. Under nitrogen protection, the mixture is stirred and heated to 150°C, and stirred at 150°C for 2 hours. Subsequently, the mixture is stirred at 170°C, 190°C, 210°C, 230°C, and 250°C for 2 hours respectively. During this period, the condensation water generated by the esterification reaction is cooled and collected through a serpentine condenser. Finally, at 250°C, the condensation water generated in the reaction material and the entrained polyethylene glycol PEG200 are removed under vacuum while the reaction is underway. After 2 hours, samples are taken to test the acid value and hydroxyl value, and tests are performed every half hour until the acid value is less than 1.0 mg KOH / g and the hydroxyl value reaches the theoretical hydroxyl value, indicating that the polyester polyol used in this invention has been successfully synthesized.

[0016] In one implementation, in step (2) preparation of the specific polyester polyol, the ratio of tetrabutyl titanate to polyethylene glycol PEG200 is 0.01wt% ~ 0.1wt%.

[0017] In one embodiment, in step (3) preparation of low-odor, low-cytotoxic high-performance polyurethane foam, the foaming agent is deionized water, and its addition amount is determined by the density of the final foam; the surfactant is polyether-modified polysiloxane, and its addition amount is in the weight ratio of (0.8 ~ 1.2):100 with the special polyester polyol; the terminal amino polyether has a functionality of 2, a relative molecular mass of 2000 g / mol, an amine value of 56 mg KOH / g, and the mass ratio of the special polyester polyol to the terminal amino polyether is (85:15) ~ (95:5).

[0018] In one implementation, when preparing the low-odor, low-cytotoxic high-performance polyurethane sponge in step (3), the special polyester polyol and the amino-terminated polyether are kept in an oven at 70°C for 24 hours in advance, and the isocyanate-terminated prepolymer is kept in an oven at 30°C for 24 hours. When preparing the polyurethane sponge, component A, which contains special polyester polyol, amino-terminated polyether, foaming agent deionized water, and surfactant polyether-modified polysiloxane, is prepared in proportion and stirred at 800 rpm for 60 s. The corresponding mass of isocyanate-terminated prepolymer is weighed as component B. Component B and component A are mixed in a mixer and stirred at 1500 rpm for 5 s to obtain a foaming liquid. The foaming liquid is then immediately poured into a mold with a built-in release film to foam and obtain a sponge body. The obtained foam body is left to stand and mature for 48 hours to obtain a fully matured low-odor, low-cytotoxic high-performance polyurethane sponge.

[0019] Based on the above, the design concept of this invention is as follows: (1) To address the issues of unreacted residual toluene diisocyanate in the foaming formulation and the small molecule aldehydes and other small molecule substances generated by side reactions due to the inability of heat to dissipate quickly in the core during foaming, this invention adopts a "two-step foaming" process that first synthesizes isocyanate-terminated prepolymer and then uses the isocyanate-terminated prepolymer to replace the traditional toluene diisocyanate for foaming. By synthesizing the isocyanate-terminated prepolymer, on the one hand, by reacting some of the reactants in advance, the heat release during foaming and the heat accumulation in the core of the sponge are reduced, thereby reducing the amount of aldehydes and other small molecule substances generated by side reactions. That is, when component A and component B are mixed for foaming, the special polyester polyol and amino-terminated polyether react with the isocyanate-terminated prepolymer to form a three-dimensional network skeleton structure of polyurethane sponge, and the foaming agent water reacts with the isocyanate-terminated prepolymer to generate carbon dioxide gas as a gas source for foaming. Among these processes, the reaction of polyethylene glycol PEG600 and toluene diisocyanate to form isocyanate-terminated prepolymer is an exothermic reaction; the reaction of special polyester polyol, amino-terminated polyether, and isocyanate-terminated prepolymer to form a three-dimensional network skeleton structure of polyurethane foam is also an exothermic reaction; the reaction of foaming agent water and isocyanate-terminated prepolymer to produce carbon dioxide gas is also an exothermic reaction; in this application, polyethylene glycol PEG600 and toluene diisocyanate are reacted in advance to prepare isocyanate-terminated prepolymer. In this process, the heat of reaction is released and discharged, thereby reducing the heat released during foaming and the heat accumulation in the core of the foam; on the other hand, by synthesizing isocyanate-terminated prepolymer from toluene diisocyanate, the amount of toluene diisocyanate monomer is reduced from the source, thereby reducing the residual toluene diisocyanate in the final polyurethane foam.

[0020] (2) The reaction activity of isocyanate-terminated prepolymers synthesized from toluene diisocyanate is reduced. To address this issue, this application uses small-molecule polyethylene glycol and toluene diisocyanate to synthesize the prepolymer. The short, straight chain and steric hindrance-free characteristics of small-molecule polyethylene glycol enhance the reaction activity of the resulting isocyanate-terminated prepolymer, ensuring that its reaction activity is not significantly reduced compared to toluene diisocyanate. Furthermore, compared to large-molecule polyethylene glycol, the prepolymer prepared by reacting small-molecule polyethylene glycol with toluene diisocyanate has more hard segments, providing sufficient cell strength during subsequent foaming. This prevents the formation of a sufficiently strong cell membrane due to the reduced reaction rate caused by catalyst removal. Simultaneously, the molecular weight of the selected polyethylene glycol should not be too small during the synthesis of the isocyanate-terminated prepolymer. Otherwise, excessive hard segments in the prepolymer molecular structure will lead to shrinkage of the final foamed sponge, excessive hardness, and brittleness.

[0021] (3) To address the issues that removing the catalyst would reduce the foaming reaction rate and that synthesizing toluene diisocyanate into isocyanate-terminated prepolymers would further reduce the reaction rate, this application addresses these issues by increasing the raw material temperature and introducing terminal amino polyethers into the foaming formulation. Increasing the raw material temperature can enhance the reactivity of the raw materials and accelerate the reaction rate. The reaction rate between the terminal primary amino group of the terminal amino polyether and isocyanate is approximately 1000 times that of the reaction between the primary hydroxyl group of conventional polymerized polyol and isocyanate, and between water and isocyanate (the reaction rates of primary hydroxyl group and isocyanate are similar to those of water and isocyanate), and approximately 3300 times that of the reaction between secondary hydroxyl group and isocyanate. Introducing terminal amino polyethers into the foaming formulation can increase the reaction rate. At the same time, the relative molecular mass of the terminal amino polyether should not be too small, and the amount added should not be excessive. Otherwise, the excessive formation of urea bonds between the terminal amino polyether and isocyanate groups (which have higher strength and hardness than the urethane bonds formed between alcohol hydroxyl groups and isocyanate groups, resulting in a faster increase in sponge hardness and more closed pores) will lead to shrinkage of the resulting sponge or make the sponge too hard and brittle.

[0022] (4) In order to further solve the problem of slow reaction rate affecting foaming reaction caused by the removal of catalyst, this application also solves the problem by synthesizing special polyester polyol. Unlike the polyester polyol used in traditional polyester polyurethane foam (obtained by polycondensation reaction of adipic acid, diethylene glycol, and trimethylolpropane under catalyst catalysis), this application uses the more active small molecule polyethylene glycol PEG200 to replace diethylene glycol. The polyester polyol prepared has higher reactivity and reacts faster with isocyanate groups. Meanwhile, PEG200 has more ether bonds in its molecular structure compared to diethylene glycol, and its relative molecular mass is larger (PEG200 is 200 g / mol, while diethylene glycol is 106.12 g / mol). After reacting with adipic acid to synthesize polyester polyols, the polyester polyols with the same relative molecular mass have more ether bonds and fewer ester bonds. The resulting polyurethane foam exhibits better hydrolysis resistance and resilience (ether bonds do not hydrolyze and have lower rotation energy and larger rotation angle; the rotation energy barrier of ether bonds is 3-4 kcal / mol, and the rotation angle is approximately 110°, which can be approximated as free rotation; the rotation energy barrier of ester bonds is 11-15 kcal / mol, and the rotation angle is 0° or 180°. Due to the conjugation effect, the molecule is almost fixed in a planar configuration). Its resilience and hydrolysis resistance are close to those of polyether-type polyurethane foams, while its mechanical properties, pore size, and fire-applied peel strength are comparable to those of polyester-type polyurethane foams.

[0023] In a second aspect, the present invention provides a low-odor, low-cytotoxic high-performance polyurethane sponge prepared by the aforementioned method, which has the following characteristics: (1) It has a lower odor and cytotoxicity than existing traditional polyurethane foams on the market.

[0024] (2) It has superior resilience and hydrolysis resistance compared to existing polyester polyurethane foams on the market.

[0025] (3) It has superior mechanical properties, finer pores, and higher fire-resistant peeling force compared to existing polyether polyurethane foams on the market.

[0026] Compared with existing technologies, the present invention has the following beneficial effects: The present invention eliminates the catalysts (mainly amine catalysts and tin catalysts) that are essential in traditional polyurethane foam formulations, reducing the residual toluene diisocyanate in the resulting polyurethane foam. It has lower odor and cytotoxicity than existing traditional polyurethane foams on the market, including polyester-type polyurethane foams and polyether-type polyurethane foams. Compared with polyether-type polyurethane foams, it has superior mechanical properties, finer pores, and higher flame-retardant peel strength. Its mechanical properties, pore size, and flame-retardant peel strength are closer to those of polyester-type polyurethane foams, and its resilience and hydrolysis resistance are closer to those of polyether-type polyurethane foams. It is very suitable as the development direction of the next generation of polyurethane foams. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] All the basic raw materials used in the following examples are commercially available products.

[0029] Example 1

[0030] A method for preparing a low-odor, low-cytotoxic, high-performance polyurethane foam includes the following steps: (1) Preparation of isocyanate group-terminated prepolymer PEG600 was dehydrated using a rotary evaporator at 120℃ / -0.09MPa until the water content was below 300ppm. A certain amount of the dehydrated PEG600 was then added to a four-necked flask, which was placed in an oil bath to cool. Once the temperature of the PEG600 in the flask had dropped below 40℃, toluene diisocyanate TDI-65 was added at a mass ratio of 63:100 (TDI-65:PEG600). Under nitrogen protection, the mixture was stirred at 200rpm for 0.5 hours. The heat transfer oil in the oil bath was then heated to 85℃, raising the temperature of the mixture in the four-necked flask to 80℃. The mixture was stirred at 83°C for 4 hours. Finally, the NCO value of the mixture was tested once per hour until the error between two consecutive test values ​​was within 5%, at which point the prepolymerization reaction was considered complete. The isocyanate group content of the obtained isocyanate group-terminated prepolymer was 10.02%.

[0031] (2) Preparation of special polyester polyols According to the molar ratio of adipic acid: polyethylene glycol PEG200: trimethylolpropane 1: 1.1:0.2 Weigh adipic acid, PEG200, and trimethylolpropane. Weigh tetrabutyl titanate catalyst according to a mass ratio of tetrabutyl titanate to polyethylene glycol PEG200 of 0.05:100. Add adipic acid, trimethylolpropane, polyethylene glycol PEG200, and tetrabutyl titanate catalyst to a reaction vessel. Under nitrogen protection, stir and mix while heating to 150°C, and react at 150°C for 2 hours. Subsequently, react at 170°C, 190°C, 210°C, 230°C, and 250°C for 2 hours respectively. During this period, the condensation water produced by the esterification reaction is cooled and collected through a serpentine condenser. Finally, the reaction was carried out at 250℃ while a vacuum was applied to remove the condensation water and entrained polyethylene glycol (PEG200) generated in the reactants. After 2 hours, samples were taken to test the acid value and hydroxyl value, with tests conducted every half hour until the acid value was less than 1.0 mg KOH / g and the hydroxyl value reached the theoretical hydroxyl value, indicating that the polyester polyol used in this invention had been successfully synthesized. The obtained special polyester polyol was found to have a functionality of 2.67 and a hydroxyl value of 60.2 mg KOH / g.

[0032] (3) Preparation of low-odor, low-cytotoxic high-performance polyurethane foam The special polyester polyol synthesized in step (2) and the amino-terminated polyether LHD-1200 from Shandong Longhua New Material Co., Ltd. were kept in an oven at 70°C for 24 hours in advance. The isocyanate-terminated prepolymer prepared in step (1) was kept in an oven at 30°C for 24 hours. 180g of the special polyester polyol prepared in step (2) that was kept in the oven, 20g of amino-terminated polyether LHD-1200 that was kept in the oven, 6.2g of deionized water, and 2g of Evonik Chemical's B 8325 silicone oil (surfactant, the composition of which is polyether modified polysiloxane, the same below) were weighed and stirred at 800rpm for 60s. After mixing evenly, component A was obtained. 397.70g of the isocyanate-terminated prepolymer prepared in step (1) that was kept in the oven was weighed as component B. Components B and A were mixed at 1500 rpm for 5 seconds to obtain a mixture. The mixture was then immediately poured into a mold with a built-in release film to foam and obtain a sponge foam. The resulting foam was then allowed to stand and mature for 48 hours to obtain a fully matured, low-odor, low-cytotoxic, high-performance polyurethane foam.

[0033] Example 2

[0034] The difference between Example 2 and Example 1 is that in step (1) the preparation of isocyanate group-terminated prepolymer, the mass ratio of isocyanate TDI-65 to PEG600 is 168:100, and the isocyanate group content of the prepared isocyanate group-terminated prepolymer is 24.99%; in step (3) the preparation of low-odor, low-cytotoxic high-performance polyurethane foam, 159.46g of the isocyanate group-terminated prepolymer prepared in step (1) is weighed as component B, and the rest is the same as in Example 1.

[0035] Example 3

[0036] The difference between Example 3 and Example 1 is that in step (2) preparation of the special polyester polyol, the molar ratio of adipic acid: polyethylene glycol PEG200: trimethylolpropane is 1:1.1:0, the functionality of the obtained special polyester polyol is 2.0, the hydroxyl value is 56mgKOH / g, the viscosity is 17200MPa*S, and the test temperature is 25℃; in step (3) preparation of low odor and low cytotoxic high performance polyurethane foam, 391.76g of the isocyanate group-terminated prepolymer prepared in step (1) is weighed as component B, and the rest is the same as in Example 1.

[0037] Example 4

[0038] The difference between Example 4 and Example 1 is that in step (1) the preparation of isocyanate group-terminated prepolymer, the mass ratio of isocyanate TDI-65:PEG600 is 168:100, and the isocyanate group content of the prepared isocyanate group-terminated prepolymer is 24.99%; in step (2) the preparation of special polyester polyol, the molar ratio of adipic acid: polyethylene glycol PEG200:trimethylolpropane is 1:1.1:0, the functionality of the obtained special polyester polyol is 2.0, the hydroxyl value is 56mgKOH / g, the viscosity is 17200MPa*S, and the test temperature is 25℃; in step (3) the preparation of low-odor, low-cytotoxic high-performance polyurethane foam, 157.08g of the isocyanate group-terminated prepolymer prepared in step (1) is weighed as component B, and the rest is the same as in Example 1.

[0039] Example 5

[0040] The difference between Example 5 and Example 1 is that in step (3) of preparing the low-odor, low-cytotoxic high-performance polyurethane foam, the special polyester polyol synthesized in step (2) is kept in an oven at 25°C for 24 hours, and the isocyanate-terminated prepolymer prepared in step (1) is kept in an oven at 25°C for 24 hours; 200g of the special polyester polyol prepared in step (2) after heat preservation, 6.2g of deionized water, and 2g of Evonik Chemical's B 8325 silicone oil are weighed and stirred at 800rpm for 60s, and after being mixed evenly, component A is obtained; 398.36g of the isocyanate-terminated prepolymer prepared in step (1) after heat preservation is weighed as component B. The rest is the same as in Example 1.

[0041] Example 6

[0042] The difference between Example 6 and Example 1 is that in step (3) preparation of low-odor, low-cytotoxic high-performance polyurethane foam, 150g of the special polyester polyol prepared in step (2) with good insulation, 50g of the amino-terminated polyether LHD-1200 with good insulation, and 396.72g of the isocyanate group-terminated prepolymer prepared in step (1) with good insulation are weighed as component B. The rest are the same as in Example 1.

[0043] Example 7

[0044] The difference between Example 7 and Example 1 is that in step (3) preparation of low-odor, low-cytotoxic high-performance polyurethane foam, the amino-terminated polyether is LHD123 from Shandong Longhua New Material Co., Ltd. (relative molecular mass of 230 g / mol, amine value of 471 mg KOH / g). 462.94 g of the isocyanate-terminated prepolymer prepared in step (1) with good insulation is weighed as component B, and the rest is the same as in Example 1.

[0045] Comparative Example 1 ZD364DW polyester sponge from Hubei Shifeng New Materials Co., Ltd. was found to have not undergone a high-temperature drying process for deodorization.

[0046] Comparative Example 2 FHV-3535 polyether sponge from Jiangsu Shifeng New Materials Co., Ltd. was found to have not undergone a high-temperature drying process for deodorization.

[0047] Comparative Example 3 200g of COIM's polyester polyol DG 173R, 6.2g of deionized water, 2g of Evonik's E5 amine catalyst, and 2g of Evonik's TEGOSTAB B8325 silicone oil / surfactant were weighed out and kept in an oven at 25℃ for 24 hours. The mixture was stirred at 800 rpm for 60 seconds until homogeneous to obtain component A. 90.29g of Wanhua Chemical's toluene diisocyanate TDI-80, which had been kept in an oven at 25℃ for 24 hours, was weighed out as component B. Components B and A were stirred and mixed at 1500 rpm for 5 seconds to obtain a mixture. The mixture was then immediately poured into a mold with a built-in release film to foam and obtain a sponge foam. The obtained foam was allowed to stand and mature for 48 hours to obtain a fully matured polyester sponge.

[0048] Odor rating test method: VDA 270-2018 (Test method for odor characteristics of automotive interior materials); In vitro cytotoxicity test method: GB / T 16886.5-2017, ISO 10993.5-2009; Tensile strength and elongation at break test method: Universal electronic tensile testing machine, test standard is DIN EN ISO 1798.

[0049] The physical property test results of the polyurethane foams prepared in Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1.

[0050] Table 1 shows the physical property test results of the polyurethane foams prepared in Examples 1-5 and Comparative Examples 1-3. Note: (1) Comparative Examples 1 and 2 are mass-produced products manufactured through the production line, and both contain catalysts and toluene diisocyanate in their foaming formulations. (2) In Table 1, "PASS" in the cytotoxicity results indicates no potential cytotoxicity, and "NG" indicates potential cytotoxicity. (3) In Table 1, "-" indicates no relevant data. For example, in Examples 6 and 7, normal sponges were not obtained, so there was no relevant physical property data.

[0051] Table 2. Cytotoxicity test results of Example 1 and Comparative Example 1 As can be seen from the test data in Table 1, as shown in Comparative Examples 1, 2, and 3, existing traditional polyurethane foams, including polyester-type polyurethane foams (Comparative Examples 1 and 3) and polyether-type polyurethane foams (Comparative Example 2), contain amine catalysts and other metal catalysts, toluene diisocyanate (TDI) monomers (TDI-80, TDI-65, or a mixture of both), and small molecule aldehydes and other small molecules produced by side reactions caused by heat accumulation during the foaming reaction. Due to the emission of amine catalysts, unreacted toluene diisocyanate monomers, small molecule aldehydes, and other small molecules produced by side reactions, the foams have a very strong odor, with an odor level exceeding 4.0. In particular, the odor caused by the emission of amine catalysts is more obvious, and the foams exhibit a distinct amine odor. Meanwhile, due to the irritant properties of the catalyst and unreacted toluene diisocyanate, the cell survival rate was very low during the in vitro cytotoxicity test. As shown in Table 2, the cell survival rate of the 100% sample extract of the sponge in Comparative Example 1 was only 38.5%, which is far below the 70% cell survival rate standard, and the cytotoxicity test could not be passed.

[0052] Conversely, as can be seen from Examples 1 to 4, the polyurethane sponge prepared by the preparation method provided by the present invention, which adopts a "two-step foaming" process that eliminates the catalyst in the sponge foaming formula and prepares toluene diisocyanate into an isocyanate group-terminated prepolymer before foaming, has extremely low odor and cytotoxicity. The odor level is below 2.0, and the cytotoxicity test can be passed. As shown in Table 2, the cell survival rate of the 100% sample extract of the sponge in Example 1 is 75.3%.

[0053] As can be seen from the comparison between Comparative Example 3 and Examples 1 to 4, even with a significant increase in raw material temperature and the introduction of highly reactive terminal amino polyethers, the foaming speed of the sponge is significantly reduced when a catalyst is lacking and toluene diisocyanate is prepared into an isocyanate-terminated prepolymer before foaming. The foaming time to the top and the surface drying time are extended from 72s and 264s in Comparative Example 3 to more than 120s and more than 400s, respectively. Although this is still suitable for the production process of existing polyurethane sponge foaming production lines, the production efficiency and capacity are reduced to a certain extent.

[0054] A comparison of Examples 5 and 1-4 reveals that, in the absence of a catalyst and without preparing toluene diisocyanate into an isocyanate-terminated prepolymer before foaming, the preparation method provided by this invention was not used. Specifically, increasing the raw material temperature and introducing highly reactive terminal amino polyethers into the foaming formulation resulted in a sponge with lower odor and cytotoxicity compared to conventional polyurethane sponges. However, the foaming speed was extremely slow, making it unsuitable for existing polyurethane sponge foaming production lines and preventing mass production. Furthermore, the polyurethane sponge obtained in Example 5 exhibited inferior physical properties compared to those obtained in Examples 1-4.

[0055] As shown in Examples 6 and 7, Examples 1-4, and Comparative Example 3, increasing the amount of terminal amino polyether added (Example 6) or decreasing the relative molecular mass of the terminal amino polyether can significantly shorten the foaming time to the top. In Example 7, the foaming time to the top was even shorter than that of conventional polyester sponge (Comparative Example 3). This is because the smaller the relative molecular mass of the terminal amino polyether and the larger the amount added, the higher its reactivity (the reactivity of the terminal primary amine group with isocyanate is much higher than that of the primary hydroxyl group and water with isocyanate; and the smaller the relative molecular mass of the terminal amino polyether, the higher its reactivity). However, the urea bond formed by the reaction of the terminal primary amine with isocyanate is stronger and harder than the urethane bond formed by the reaction of the primary hydroxyl group with isocyanate. This causes the carbon dioxide gas generated by the reaction of the foaming agent water and isocyanate during foaming to be unable to break through the cell membrane (due to excessive strength and hardness), resulting in the final polyurethane sponge shrinking due to excessively high closed-cell ratio.

[0056] As can be seen from Examples 1-4 and Comparative Examples 1 and 3, by preparing a special polyester polyol and introducing a more active low molecular weight polyethylene glycol PEG200 into the molecular structure of the special polyester polyol to replace the diethylene glycol in the molecular structure of the conventional polyester polyol, the final foamed polyurethane sponge has better resilience than the existing traditional polyester polyurethane sponge. The drop ball rebound rate is 4%-7% higher than that of the existing traditional polyester polyurethane sponge, increasing from 28%-29% in Comparative Examples 1 and 3 to 33%-35% in Examples 1-4. This is because the introduction of PEG200 makes the special polyester polyol have more ether bonds and fewer ester bonds in its molecular structure compared to the conventional polyester polyol, and the resilience of the resulting sponge is closer to that of the polyether polyurethane sponge (the sponge obtained in Comparative Example 2 is a polyether sponge with a drop ball rebound rate of 38%).

[0057] As can be seen from Examples 1-4 and Comparative Examples 1-3, the pore size of the sponges obtained in Examples 1-4 is similar to that of Comparative Example 3, but 21-26 μm larger than that of Comparative Example 1. This is due to air bubbles introduced during manual foaming in the laboratory. The pore size of the sponges obtained in Examples 1-4 is 32-37 μm smaller than that of Comparative Example 2. This is because the special polyester polyol has a large number of ester bonds and the resulting large number of intermolecular hydrogen bonds in its molecular structure compared with the polyether polyol used in the foaming of Comparative Example 2 (polyether sponge). It has a higher viscosity, resulting in smaller and finer pore size of the sponge. Because of the presence of numerous ester bonds and intermolecular hydrogen bonds in the molecular structure of the special polyester polyol, the resulting sponge exhibits higher mechanical properties and fire-applied peel strength than traditional polyether sponges. The tensile strength and elongation at break of the sponges obtained in Examples 1-4 are 127.75-156.42 kPa and 107.80%-122.42% higher than those in Comparative Example 2, respectively, and the tear strength is 0.36-0.41 N / mm higher. Compared to traditional polyether-type polyurethane sponges (Comparative Example 2), the sponges obtained in Examples 1-4 possess superior mechanical properties, finer pores, and higher fire-applied peel strength, and are closer to polyester sponges (Comparative Examples 1 and 3).

[0058] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a low-odor, low-cytotoxic, high-performance polyurethane foam, characterized in that, Includes the following steps: (1) An isocyanate-terminated prepolymer was prepared by reacting polyethylene glycol 600 and toluene diisocyanate. The isocyanate group content of the prepared isocyanate-terminated prepolymer was 10% to 25%. (2) A special polyester polyol was prepared by reacting adipic acid, tetrabutyl titanate, trimethylolpropane and polyethylene glycol PEG200. The hydroxyl value was 50~80mgKOH / g and the functionality was 2.0~2.

7. The molar ratio of hydroxyl to carboxyl groups in the reactants was (1.1~1.4):

1. The preparation of the special polyester polyol includes: adding adipic acid, trimethylolpropane, polyethylene glycol PEG200 and tetrabutyl titanate into a reaction vessel, stirring and mixing under nitrogen protection while heating to 150°C, and reacting at 150°C for 2 hours; subsequently, stirring and reacting at 170°C, 190°C, 210°C, 230°C and 250°C for 2 hours respectively; finally, reacting at 250°C while vacuuming to remove the condensation water generated in the reaction material and the entrained polyethylene glycol PEG200, and after 2 hours, sampling to test the acid value and hydroxyl value, testing once every half hour, until the acid value is less than 1.0 mg KOH / g and the hydroxyl value reaches the theoretical hydroxyl value; (3) A low-odor, low-cytotoxic high-performance polyurethane foam is prepared from components A and B. Component A includes a special polyester polyol, an amino-terminated polyether, a foaming agent, and a surfactant. Component B includes an isocyanate-terminated prepolymer. The amount of component B is as follows: it is taken according to the ratio of the total molar amount of isocyanate groups in component B to the sum of the molar amounts of the hydroxyl groups of all special polyester polyols and foaming agents in component A and the primary amino groups of the amino-terminated polyether, which is 1.0 to 1.

1. The amino-terminated polyether has a functionality of 2, a relative molecular mass of 2000 g / mol, and an amine value of 56 mg KOH / g. The mass ratio of the special polyester polyol to the amino-terminated polyether is (85:15) to (95:5).

2. The method for preparing low-odor, low-cytotoxic, high-performance polyurethane foam according to claim 1, characterized in that, In step (1), the mass ratio of toluene diisocyanate to polyethylene glycol is (63 ~ 168):

100.

3. The method for preparing a low-odor, low-cytotoxic, high-performance polyurethane foam according to claim 1, characterized in that, In step (1), the preparation of the isocyanate-terminated prepolymer includes: dehydrating polyethylene glycol at 120℃ / -0.09MPa until the water content is less than 300ppm; taking a certain amount of the dehydrated polyethylene glycol into a flask, allowing the flask to stand and cool down to below 40℃, adding toluene diisocyanate in proportion, and stirring and mixing under nitrogen protection; heating the mixture in the flask to 80~83℃ and continuing to stir and react for 4 hours; starting to test the NCO value of the mixture, testing once per hour, until the error between two consecutive test values ​​is within 5%, at which point the prepolymerization reaction is considered complete.

4. The method for preparing low-odor, low-cytotoxic, high-performance polyurethane foam according to claim 1, characterized in that, In step (2), the ratio of tetrabutyl titanate to polyethylene glycol PEG200 is 0.01wt% ~ 0.1wt%.

5. The method for preparing low-odor, low-cytotoxic, high-performance polyurethane foam according to claim 1, characterized in that, In step (3), the foaming agent is deionized water; the surfactant is polyether modified polysiloxane, and the weight ratio of its addition amount to the special polyester polyol is (0.8 ~ 1.2):

100.

6. The method for preparing low-odor, low-cytotoxic, high-performance polyurethane foam according to claim 1, characterized in that, In step (3), component A is prepared in proportion and stirred at 800 rpm for 60 s; the corresponding mass of isocyanate group-terminated prepolymer is weighed as component B; component B and component A are mixed in a mixer and stirred at 1500 rpm for 5 s to obtain foaming liquid, and then the foaming liquid is immediately poured into a mold to foam to obtain sponge foam; after the obtained foam is left to stand and mature for 48 h, a fully matured low-odor, low-cytotoxic high-performance polyurethane sponge is obtained.

7. The method for preparing low-odor, low-cytotoxic, high-performance polyurethane foam according to claim 1 or 6, characterized in that, In step (3), the special polyester polyol and amino-terminated polyether are kept in an oven at 70°C for 24 hours in advance, and the isocyanate group-terminated prepolymer is kept in an oven at 30°C for 24 hours.

8. A low-odor, low-cytotoxicity, high-performance polyurethane foam prepared by the preparation method according to any one of claims 1 to 7.

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