An aging-resistant and breathable latex polyurethane foam and its preparation method

Abstract

This invention relates to an aging-resistant and breathable latex polyurethane foam and its preparation method. The raw materials for the aging-resistant and breathable latex polyurethane foam include castor oil-modified polyol, highly active polyether polyol with a primary hydroxyl content ≥60%, polyoxypropylene polyol, a composite catalyst, polyether-modified organosilicon surfactant, a foaming agent, an antioxidant, and polyether-modified diphenylmethane diisocyanate. The castor oil-modified polyol in the raw materials enhances the sponge's hydrolysis resistance and toughness; the highly active polyether polyol accelerates the reaction rate and achieves cold curing, reducing high-temperature damage to the sponge structure; the polyoxypropylene polyol optimizes the sponge's softness and moldability; and the polyether-modified diphenylmethane diisocyanate improves the compatibility of the raw materials. Ultimately, this results in a sponge with both excellent aging resistance and breathability, solving the technical problems of poor breathability, easy aging, and short service life of existing sponges, making it suitable for long-term use scenarios such as mattress comfort layers.

Description

Technical Field

[0001] This invention relates to the field of isocyanate polymerization products, and particularly to an aging-resistant and breathable latex polyurethane sponge and its preparation method. Background Technology

[0002] Currently, in the modern foam bedding industry, mattress comfort layers commonly use polyurethane slow rebound foam or natural / synthetic latex materials. Polyurethane slow rebound foam, with its soft texture and low resistance, conforms well to the body's curves, providing a good sleep experience. However, its relatively dense molecular structure results in mostly closed-cell pores, leading to high airflow resistance and significantly reduced breathability. In actual use, the heat and moisture generated by the body cannot dissipate quickly, easily causing heat and moisture buildup. This not only makes the user feel stuffy and significantly reduces comfort, but the long-term damp environment can also easily breed bacteria, triggering skin problems such as eczema or allergies, affecting the user's health.

[0003] Latex, whether natural or synthetic, possesses a unique honeycomb-like porous structure that gives it excellent breathability and resilience. It quickly dissipates heat and moisture during sleep and rebounds rapidly after turning over, offering strong resistance to disturbance. However, the presence of numerous unsaturated double bonds in its molecular structure inherently limits its resistance to aging. In daily use, the combined effects of UV radiation, oxygen oxidation, and environmental heat easily cause latex molecular chains to oxidize and break, leading to a continuous decline in material performance. Typically, after 2-3 years of use, latex will exhibit noticeable powdering, brittleness, and even cracking, severely shortening the mattress's lifespan and significantly reducing its support performance, making it unable to consistently meet the user's needs.

[0004] Various solutions have been proposed in the industry to improve the aging resistance of materials. For example, adding anti-aging additives, UV absorbers, and anti-yellowing agents can enhance the durability of polyurethane coatings. However, these methods are highly dependent on added additives, which are prone to migration, decomposition, or loss due to environmental influences during long-term use. Over time, the aging resistance effect will be significantly weakened, making it difficult to achieve long-term stable protection. Some studies have also improved the aging resistance of materials by adding antioxidants, titanium dioxide, and other substances. However, these technical solutions are mostly aimed at rigid materials or specific industrial applications. For soft polyurethane foam, especially soft polyurethane foam used as a mattress comfort layer, it is impossible to solve the core technical problem of aging resistance at the intrinsic molecular structure level while ensuring high breathability. This has become a key technical bottleneck restricting the improvement of mattress comfort layer material performance. Summary of the Invention

[0005] The purpose of this invention is to disclose an aging-resistant and breathable latex polyurethane foam and its preparation method, so as to solve one or more technical problems existing in the existing methods and provide at least one beneficial option or create conditions.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention is to provide an aging-resistant and breathable latex polyurethane foam. The raw materials of the aging-resistant and breathable latex polyurethane foam include castor oil-modified polyol, highly active polyether polyol with a primary hydroxyl content ≥60%, polyoxypropylene polyol, a composite catalyst, a polyether-modified organosilicon surfactant, a foaming agent, an antioxidant, and a polyether-modified diphenylmethane diisocyanate; the composite catalyst includes at least two of the following: a gel catalyst, an organometallic catalyst, and a bis(tertiary) amine ether catalyst; the antioxidant is primarily a hindered phenolic antioxidant, supplemented with a compounded phosphite antioxidant. The castor oil-modified polyol in the raw materials enhances the sponge's hydrolysis resistance and toughness; the highly active polyether polyol accelerates the reaction rate and achieves cold curing, reducing the damage to the sponge structure caused by high temperatures; and the polyoxypropylene polyol optimizes the sponge's softness and moldability. The combination of composite catalysts can precisely control the foaming and gelation reaction rates, avoiding problems such as uneven sponge pores and cracking caused by reaction imbalance. The antioxidants, composed of hindered phenols and phosphites, form a synergistic anti-aging system, effectively inhibiting thermo-oxidative aging and yellowing. The polyether-modified diphenylmethane diisocyanate improves the compatibility of the raw materials, ultimately enabling the sponge to possess both excellent aging resistance and breathability, solving the technical problems of poor breathability, easy aging, and short service life of existing sponges, and making it suitable for long-term use scenarios such as mattress comfort layers.

[0007] In a further embodiment of the first aspect of the present invention, the antioxidant is selected from KH-228, KH-550, or IRGASTAB PUR 68. The antioxidants provided above are all liquid compound types, exhibiting excellent compatibility with polyols, isocyanates, and other raw materials in the system, and can be uniformly dispersed without the need for additional solvents. KH-228 and KH-550 offer high cost-effectiveness, with significant anti-burning and anti-yellowing effects, effectively preventing degradation and internal charring during the foaming process. IRGASTAB PUR 68, on the other hand, boasts low VOCs and high-end anti-yellowing advantages, making it suitable for demanding applications such as mattresses and automotive interiors, further enhancing the aging resistance and safety of the sponge, while ensuring long-term stability of the sponge's appearance and color.

[0008] In a further embodiment of the first aspect of the present invention, the ricinoleic acid modified polyol is selected from EL10, SY750 / SY751, AC-005 / AC-006 / AC-009, or D265 / D280. The selected ricinoleic acid modified polyols are all ester-ether mixtures, possessing hydrophobic and hydrolysis-resistant properties, high toughness, and bio-based characteristics. Synergistically, they work with highly active polyether polyols and polyoxypropylene polyols to significantly improve the wet strength and hydrolysis resistance of the sponge, preventing aging and damage due to moisture during long-term use. Simultaneously, these polyols have moderate viscosity, making them easy to mix evenly with other raw materials, ensuring consistent sponge molding. Different models can be adapted to different softness and hardness requirements, broadening the application range of the sponge and balancing comfort and durability.

[0009] In a further embodiment of the first aspect of the present invention, the highly active polyether polyol is selected from F1623, 330N, or 10LD76EK. The selected highly active polyether polyols are all ethylene oxide-terminated polypropylene triols with a primary hydroxyl content ≥60%, exhibiting high activity and fast reaction rates. This allows for cold curing and molding of the sponge without the need for high-temperature heating, reducing production energy consumption while avoiding structural damage to the sponge caused by high temperatures. Its high primary hydroxyl content allows for complete reaction with isocyanate, forming a regular three-dimensional network structure, improving the sponge's resilience and structural stability, while also improving the sponge's open porosity and further optimizing its air permeability, thus solving the problems of slow reaction, long curing time, and poor air permeability associated with ordinary polyether polyols.

[0010] In a further embodiment of the first aspect of the present invention, the polyoxypropylene polyol is selected from 3156A, PPG-6000, or Pluracol 3800. The selected polyoxypropylene polyols are all general-purpose flexible foam polyethers, exhibiting good compatibility with highly active polyether polyols and castor oil-modified polyols. They can synergistically adjust the softness and support of the foam, avoiding the problems of excessively soft foam that collapses easily or excessively hard foam that is uncomfortable. 3156A is suitable for general mattress applications, PPG-6000 has a high molecular weight, which can improve the toughness and durability of the foam, and Pluracol 3800 has good stability, ensuring consistency in mass production of the foam. Simultaneously, these polyethers can optimize the pore structure of the foam, helping to improve breathability and balancing comfort and molding stability.

[0011] In a further embodiment of the first aspect of the present invention, the composite catalyst comprises a gel-type liquid catalyst A33, stannous octoate T-9, stannous caprylate, and bis(dimethylaminoethyl) ether A1. The gel-type liquid catalyst A33, prepared from 33% triethylenediamine and 67% dipropylene glycol, can efficiently regulate the gelation reaction. Stannous octoate T-9 and stannous caprylate, as organometallic catalysts, accelerate the foaming reaction. Bis(dimethylaminoethyl) ether A1 can assist in regulating the reaction rate. The four components together form a synergistic catalytic system, which can precisely match the reaction rhythm of sponge foaming and gelation, avoiding problems such as excessively large pores due to excessively rapid foaming and decreased air permeability due to excessively rapid gelation. Simultaneously, this type of catalyst requires a small amount, has no obvious odor, can reduce the VOC content of the sponge, improve safety in use, and the catalyst is not easily migrated, ensuring the structural stability of the sponge during long-term use.

[0012] In a further embodiment of the first aspect of the present invention, the raw materials of the aging-resistant and breathable latex polyurethane foam include the following components by weight: 20-80 parts EL10, 20-80 parts F1623, 20-30 parts 3156A, 0.05-3 parts composite catalyst, 0.05-5 parts 5800, 1-4 parts water, 0.3-4.5 parts KH-1023, and 40-70 parts Wanna 8223. EL10 is a ricinoleic acid-modified polyol. Ricinoleic acid is a fatty acid, and the presence of unsaturated fatty acid double bonds is beneficial to improving the high-temperature resistance of the end-capped polyether polyol. The hydroxyl groups in the molecular chain undergo dehydration and form a conjugated structure with the double bonds, further improving the high-temperature resistance of the end-capped polyether polyol. F1623 is a highly active polyether polyol with a molecular weight of 3000-5000, a functionality of 3, and a hydroxyl value of 30-60 mg KOH / g. The 3156A is polypropylene triol, with a molecular weight of 3000-3700, functionality 3, and hydroxyl value of 45-56 mgKOH / g. The 5800 is a polyether-modified organosilicon surfactant, mainly composed of polysiloxane-olefin block or graft copolymers, where the polysiloxane is a non-polar segment and the olefin is a polar segment. The water is a chemical foaming agent and also a chain extender. The KH-1023 is a compound antioxidant produced by Shenzhen Weihongxin Technology Co., Ltd. The Wanna 8223 is a polyether-modified diphenylmethane diisocyanate, which helps polyurethane sponge form an open-cell structure, thereby significantly improving air permeability. The resulting aging-resistant and breathable latex polyurethane sponge has a tensile strength ≥60 kPa, an elongation ≥170%, and an air permeability of 0.70 m³ / g. 3 / min.

[0013] A second aspect of this invention is to provide a method for preparing the aging-resistant and breathable latex polyurethane foam described in the first aspect of this invention. The preparation method includes the following steps: S1. The castor oil modified polyol, the highly active polyether polyol, the polyoxypropylene polyol, the composite catalyst, the polyether modified organosilicon surfactant, the foaming agent and the antioxidant are added into a reaction vessel and stirred evenly to obtain a polyol mixture; S2. Add the polyether-modified diphenylmethane diisocyanate to the polyol mixture, stir and mix at 1800~3000 rpm for 3~5 seconds to obtain the intermediate product; S3. Inject the intermediate product into a mold for maturation.

[0014] The method for preparing aging-resistant and breathable latex polyurethane foam provided by this invention is simple and convenient, suitable for industrial mass production. The entire preparation process does not require high temperature and high pressure, has low energy consumption and low production cost, and reduces pollutant emissions, meeting the requirements of green production.

[0015] In a further embodiment of the second aspect of the present invention, the stirring rate in step S1 is 300-400 rpm. Further limiting the stirring rate in step S1 to 300-400 rpm ensures that the raw materials such as castor oil-modified polyol and highly active polyether polyol are thoroughly and uniformly mixed with the composite catalyst, antioxidants, and other additives, avoiding problems such as excessively high or low local additive concentrations and uneven raw material dispersion. It also avoids excessively fast stirring, which could lead to excessive bubble formation and affect subsequent foaming and molding. Simultaneously, this stirring rate reduces the breakage of raw material molecular chains, ensuring the activity of the raw materials and guaranteeing the smooth progress of the subsequent reaction with isocyanate, thereby improving the quality and performance stability of the sponge molding.

[0016] In a further embodiment of the second aspect of the present invention, the curing time required in step S3 is 24 to 72 hours. Limiting the curing time ensures that the sponge is fully cured, allowing the reaction between raw materials to be complete and forming a stable three-dimensional network structure. This avoids insufficient internal reaction, poor mechanical properties, and easy cracking due to too short a time, or low production efficiency and increased production costs due to too long a curing time. The 24-72 hour duration is suitable for cold curing processes, allowing curing to be completed at room temperature without additional heating, further reducing energy consumption. Simultaneously, it ensures that the sponge's aging resistance, air permeability, and mechanical properties reach optimal levels, improving product qualification rates. Attached Figure Description

[0017] Figure 1 This is the infrared spectrum of the polyurethane sponge pyrolysis control experiment in Example 1. Detailed Implementation

[0018] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Any modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the present invention are within the scope of the present invention.

[0019] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0020] Example 1: Preparation of aging-resistant and breathable latex polyurethane foam The preparation steps include: S1. Take EL10, F1623, 3156A, bis(dimethylaminoethyl) ether A1, gel-type liquid catalyst A33, tin caprylate, water, 5800 and KH-1023 into a mixing tank, stir evenly at 300~400 rpm to obtain a polyol mixture; S2. The polyol mixture is rapidly mixed with the Wanna 8223 isocyanate component in a high-speed stirrer at 1800~3000 rpm for 3~5 seconds to obtain an intermediate product; S3. Pour the intermediate product into a foaming mold, or produce it using a polyurethane foaming machine, and cure it at room temperature for 24-72 hours before cutting it to obtain the finished product.

[0021] Among them, EL10 has a functionality of 3 and a hydroxyl value of 110 mg KOH / g; F1623 has a functionality of 3, a hydroxyl value of 33 mg KOH / g, a molecular weight of 5000, 70% ethylene oxide, and 70% primary hydroxyl; 3156A has a functionality of 3, a hydroxyl value of 56 mg KOH / g, and a molecular weight of 3000.

[0022] Adjust the dosage of each component according to Table 1 to prepare samples 1#, 2# and 3# respectively.

[0023] Table 1. Component ratios of the three test samples

[0024] The three samples were first tested for air permeability, then subjected to hot air aging treatment, and tensile strength and elongation tests were performed before and after the treatment according to GB / T 6344-2008.

[0025] The air permeability of sample #1 was measured to be 30 m. 3 / min, the air permeability of samples 2 and 3 is 70 m. 3 / min.

[0026] The hot air aging treatment was carried out for 72 hours according to the American Society for Testing and Materials (ASTM) Rubber-Air Oven Aging Test Method (D573-04(2019)). The performance test comparison results are shown in Table 2.

[0027] Table 2. Performance indicators of the three test samples before and after aging treatment

[0028] Table 2 shows that the mechanical properties (tensile and tear strength) and air permeability of the polyurethane foam are significantly improved after introducing ricinoleic acid-modified polyol EL10. The high-temperature stability of the polyol is improved by ricinoleic acid esterification and end-capping. The hydroxyl groups in the ricinoleic acid-terminated fatty acids readily undergo intramolecular dehydration and form conjugated structures with double bonds. With increasing molecular weight, the initial decomposition temperature and oxidative decomposition temperature of the ricinoleic acid polyol increase, while the isothermal mass loss rate decreases, ultimately resulting in a significant improvement in the aging resistance of the final polyurethane product.

[0029] Further analysis of the data from samples #2 and #3 revealed that the addition of antioxidant KH-1023 further improved the tensile strength of the material and demonstrated superior retention of physical properties in aging tests, proving the synergistic effect of the formulation of this invention.

[0030] Infrared spectra of sample #3 before and after heat aging treatment are shown below. Figure 1 As shown in the figure, 3508 cm -1 The peak at 2860 cm⁻¹ is a characteristic peak of the stretching vibration of the hydroxyl group (-OH). -1 The double peak at 1634 cm⁻¹ represents the vibrational absorption peak of the methylene group (-CH₂-). -1 This is the stretching vibration peak of an aliphatic unsaturated double bond (C=C), at 1731 cm⁻¹. -1 The peak at 1458 cm⁻¹ corresponds to the stretching vibration of the carbonyl group (C=O); it also coincides with the peak at 1458 cm⁻¹. -1 The absorption peak at 1101 cm⁻¹ forms a double peak, which is characteristic of carboxylic acid (-COOH); -1 This is the characteristic peak of the stretching vibration of the ether bond (COC); 723 cm⁻¹ -1 The peaks are characteristic absorption peaks for long-chain saturated alkanes with n≥4, and structural characteristic peaks for fatty acids. This demonstrates that the antioxidant system composed of hindered phenols and phosphites can inhibit the initiation and propagation of oxidation reactions, prevent the continuation of chain reactions, and effectively inhibit the 1731 cm⁻¹ oxidation state. -1 Enhancement of the carbonyl peak and breakage of the molecular chain.

[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. An aging-resistant and breathable latex polyurethane foam, characterized in that, The raw materials include ricinoleic acid modified polyol, high-activity polyether polyol with primary hydroxyl content ≥60%, polyoxypropylene polyol, composite catalyst, polyether modified organosilicon surfactant, foaming agent, antioxidant, and polyether modified diphenylmethane diisocyanate. The composite catalyst includes at least two of the following: gel catalyst, organometallic catalyst, and bistertiary amine ether catalyst; The antioxidant is mainly hindered phenolic antioxidant, supplemented by compound phosphite antioxidant.

2. The aging-resistant and breathable latex polyurethane foam according to claim 1, characterized in that, The antioxidant is selected from KH-228, KH-550 or IRGASTAB PUR 68.

3. The aging-resistant and breathable latex polyurethane foam according to claim 1, characterized in that, The ricinoleic acid-modified polyol is selected from EL10, SY750 / SY751, AC-005 / AC-006 / AC-009 or D265 / D280.

4. The aging-resistant and breathable latex polyurethane foam according to claim 1, characterized in that, The highly active polyether polyol is selected from F1623, 330N or 10LD76EK.

5. The aging-resistant and breathable latex polyurethane foam according to claim 1, characterized in that, The polyoxypropylene polyol is selected from 3156A, PPG-6000 or Pluracol 3800.

6. The aging-resistant and breathable latex polyurethane foam according to claim 1, characterized in that, The composite catalyst includes gel-type liquid catalyst A33, stannous octoate T-9, stannous caprylate, and bis(dimethylaminoethyl) ether A1.

7. The aging-resistant and breathable latex polyurethane foam according to claim 1, characterized in that, The aging-resistant and breathable latex polyurethane foam has a tensile strength ≥60kPa, and / or elongation ≥170%, and / or air permeability = 0.70 m. 3 / min.

8. The method for preparing the aging-resistant and breathable latex polyurethane foam according to any one of claims 1 to 7, characterized in that, Including the following steps: S1. The castor oil modified polyol, the highly active polyether polyol, the polyoxypropylene polyol, the composite catalyst, the polyether modified organosilicon surfactant, the foaming agent and the antioxidant are added into a reaction vessel and stirred evenly to obtain a polyol mixture; S2. Add the polyether-modified diphenylmethane diisocyanate to the polyol mixture, stir and mix at 1800~3000 rpm for 3~5 seconds to obtain the intermediate product; S3. Inject the intermediate product into a mold for maturation.

9. The preparation method according to claim 8, characterized in that, The stirring speed in step S1 is 300~400 rpm.

10. The preparation method according to claim 8, characterized in that, The maturation time required in step S3 is 24 to 72 hours.

Images