Yellowing-resistant sponge as well as preparation method and application thereof

Abstract

The invention relates to yellowing-resistant sponge as well as a preparation method and application thereof. The sponge is prepared from the following raw materials in parts by weight: 50 to 70 parts of aliphatic isocyanate, 4 to 8 parts of fluorine-containing hydroxyl silicone oil, 45 to 60 parts of polyether polyol A, 10 to 20 parts of polyether polyol B, 15 to 20 parts of hydrogenated hydroxyl-terminated polybutadiene, 5 to 8 parts of anti-yellowing chain extender, 0.5 to 2 parts of catalyst, 0.8 to 1.5 parts of foam stabilizer and 1.5 to 3 parts of water. Wherein the anti-yellowing chain extender is a composition of oxalyl dihydrazine, 3-isocyanate propyl trimethoxy silane and trimethylolpropane, and the anti-yellowing chain extender is a composition of the oxalyl dihydrazine, the 3-isocyanate propyl trimethoxy silane and the trimethylolpropane. According to the polyurethane sponge disclosed by the invention, the hydrogenated hydroxyl-terminated polybutadiene is matched with the aliphatic diisocyanate, so that double-bond oxidation is avoided, the photosensitivity of a benzene ring is eliminated, and the ageing resistance of the polyurethane sponge is doubly guaranteed. Meanwhile, by adding the anti-yellowing chain extender, the anti-yellowing performance of the sponge is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of underwear materials, and in particular to a yellowing-resistant sponge and a preparation method and application thereof. Background Art

[0002] Bras are a necessity in women's daily lives, and their materials typically include foam and textiles. Polyurethane foam is often used, which imparts many excellent properties to bras, such as good breathability, wear resistance, lightness, softness, easy cleaning, and excellent elasticity. However, polyurethane foam is prone to yellowing when exposed to ultraviolet rays from sunlight over a long period of time, and lacks antibacterial properties. Specifically, certain chemical groups in polyurethane foam, such as isocyanate groups directly attached to benzene rings, can decompose the urethane bonds under the combined effects of light, heat, and oxygen, particularly ultraviolet radiation, to form aromatic amines. The benzene nuclei on the aromatic amines undergo oxidative rearrangement to form chromophores such as quinone structures, causing the polyurethane foam product to turn yellow. This process also degrades the mechanical properties of the material, thereby reducing its service life. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a yellowing-resistant sponge and a preparation method and application thereof.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] In a first aspect, the present invention provides a yellowing-resistant sponge, comprising the following raw materials in parts by weight: 50-70 parts of aliphatic isocyanate, 4-8 parts of fluorinated hydroxy silicone oil, 45-60 parts of polyether polyol A, 10-20 parts of polyether polyol B, 15-20 parts of hydrogenated hydroxy-terminated polybutadiene, 5-8 parts of yellowing-resistant chain extender, 0.5-2 parts of catalyst, 0.8-1.5 parts of foam stabilizer and 1.5-3 parts of water; wherein the yellowing-resistant chain extender is oxalyl dihydrazide, 3-isocyanate propyltrimethoxysilane and trimethylolpropane in a mass ratio of 1: (1-1.5): (3-4).

[0006] The polyurethane sponge of the present invention can achieve the effect of yellowing resistance mainly by adding a yellowing resistance chain extender. Oxalyl dihydrazide is used as a diamine chain extender to react with isocyanate to form a urea bond (—NH—CO—NH—). The amide groups (—NH— and C=O) in its molecular structure can form a dense multiple hydrogen bond network. This hydrogen bond network can effectively quench free radicals and inhibit oxidation reactions, reducing the formation of chromophores (such as quinone structures) caused by ultraviolet rays or thermal oxidation, thereby reducing the risk of yellowing. 3-isocyanatepropyltrimethoxysilane contains isocyanate groups and silanol groups. The isocyanate groups can react with the isocyanate groups and hydroxyl groups in the polyurethane system to introduce silane chain segments into the polyurethane molecular network; the silanol groups can hydrolyze to form silanol groups, forming chemical bonds with the substrate surface, improving the adhesion of the material. At the same time, the introduction of silicon elements can enhance the flexibility and oxidation resistance of the molecular chain. The silane structure has good weather resistance and can effectively resist damage to the material by external factors such as ultraviolet rays, thereby inhibiting yellowing. The three hydroxyl groups (-OH) of trimethylolpropane react with isocyanate to form a network structure with high cross-linking density, which inhibits the oxidative degradation of the molecular chain. Its side chain methyl (-CH3) produces steric hindrance, hindering the diffusion of free radicals and the progress of oxidation reaction, which complements the rigid structure of oxalyl dihydrazide, balances the rigidity and toughness of the material, and avoids local yellowing caused by stress cracking.

[0007] To improve the low-temperature toughness, hydrolysis resistance, and dynamic mechanical properties of polyurethane sponges, flexible polyether or polyester segments are often introduced into the polyurethane molecular chain. Among them, hydroxy-terminated polybutadiene (HTPB) is widely used as a soft segment due to its excellent flexibility, low-temperature flexibility, and good hydrolysis resistance. However, ordinary HTPB molecular chains contain a large number of active unsaturated double bonds (—C═C—). These double bonds are highly susceptible to oxidation reactions under light, oxygen, or high temperature conditions, forming chromophore structures such as quinones, causing significant yellowing of the material, seriously affecting the appearance and service life of the product.

[0008] To address the core flaw of conventional HTPB, which is prone to yellowing, this application uses hydrogenated hydroxy-terminated polybutadiene. This material uses a catalytic hydrogenation process to efficiently convert unsaturated double bonds in the molecular chain into stable saturated single bonds (—C—C—), fundamentally eliminating active sites for oxidation reactions and effectively avoiding the yellowing problem caused by double bond oxidation. Furthermore, the saturated aliphatic long-chain backbone formed after hydrogenation imparts HHTPB with excellent chemical inertness, significantly reducing its sensitivity to environmental factors (such as UV light and ozone) and significantly improving its stability.

[0009] When hydrogenated hydroxy-terminated polybutadiene is embedded in the polyurethane backbone as a soft segment, it not only contributes to the required flexibility, but also forms a more stable elastomer network structure. This network structure further suppresses the degradation and yellowing process of the molecular chain. In addition, the present application uses aliphatic isocyanates that do not contain benzene rings in the selection of hard segments. The benzene rings in traditional aromatic isocyanates (such as MDI and TDI) are easily oxidized under the action of ultraviolet rays to form quinone structures, which is one of the important causes of polyurethane yellowing. The use of aliphatic isocyanates completely eliminates the risk of photosensitivity yellowing caused by benzene rings.

[0010] Therefore, the synergistic combination of hydrogenated hydroxy-terminated polybutadiene and aliphatic diisocyanate, on the one hand, avoids oxidative yellowing by eliminating the double bonds in the soft segment, and on the other hand, eliminates photooxidative yellowing by eliminating the photosensitivity of the benzene ring in the hard segment, forming a dual protection mechanism, which jointly ensures the excellent long-term aging resistance (including anti-yellowing properties) of the final polyurethane sponge.

[0011] Preferably, the mass ratio of oxalyl dihydrazide, 3-isocyanatepropyltrimethoxysilane and trimethylolpropane is 1:(1-1.5):(3-4).

[0012] Preferably, the polyether polyol A is polyoxypropylene polyoxyethylene ether; and the polyether polyol B is hexafunctional polyoxyethylene polyoxypropylene ether.

[0013] Preferably, the aliphatic isocyanate is isophorone diisocyanate, hexamethylene diisocyanate and 1,5-pentamethylene diisocyanate in a mass ratio of 1:1:(0.5-1.5).

[0014] Preferably, the catalyst is a main catalyst and a co-catalyst in a mass ratio of 1:(0.01-0.02), the main catalyst is one or two of 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine and 1,8-diazabicyclo[5.4.0]undec-7-ene; the co-catalyst is stannous octoate.

[0015] Preferably, the fluorinated hydroxy silicone oil is a hydroxyl-terminated fluorinated silicone oil.

[0016] In a second aspect, the present invention provides a method for preparing a yellowing-resistant sponge, comprising the following steps:

[0017] Mixing aliphatic isocyanate, fluorinated hydroxy silicone oil and part of the catalyst to carry out polymerization reaction to obtain an isocyanate-terminated prepolymer A;

[0018] Mixing polyether polyol A, polyether polyol B, hydrogenated hydroxyl-terminated polybutadiene, yellowing-resistant chain extender, remaining catalyst, foam stabilizer and water to obtain material B;

[0019] The prepolymer material A and the prepolymer material B are mixed, foamed and matured in sequence to obtain a yellowing-resistant sponge.

[0020] Preferably, the polymerization reaction comprises reacting at 50-60° C. for 2-4 hours, then heating to 80-100° C. and continuing to react for 2-3 hours.

[0021] Preferably, the foaming method is high-pressure foaming, and the foaming pressure is 20-60 bar; the aging temperature is 60-100° C., and the aging time is 12-48 hours.

[0022] In a third aspect, the present invention provides a use of the yellowing-resistant sponge in the first aspect in preparing bra sponge for underwear.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The polyurethane sponge of the present invention uses hydrogenated hydroxy-terminated polybutadiene in combination with aliphatic diisocyanate, which not only avoids double bond oxidation but also eliminates the photosensitivity of the benzene ring, thereby doubly protecting the aging resistance of the polyurethane sponge. At the same time, the sponge's anti-yellowing performance is further improved by adding an anti-yellowing chain extender. The main components of the anti-yellowing chain extender are oxalyl dihydrazide, 3-isocyanate propyl trimethoxysilane, and trimethylolpropane. Oxalyl dihydrazide provides hydrogen bond crosslinking points, enhances the orderliness of the hard segment, and can jointly inhibit free radicals and oxidation reactions with 3-isocyanate propyl trimethoxysilane. The siloxane network formed by 3-isocyanate propyl trimethoxysilane can reduce the depth of ultraviolet penetration and enhance the overall network stability through chemical crosslinking. Trimethylolpropane further increases the crosslinking density and cooperates with oxalyl dihydrazide to form a rigid and flexible network structure, reducing structural degradation caused by stress concentration. The three work together to form an anti-yellowing system with both immediate protection function and long-term stability. DETAILED DESCRIPTION

[0025] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0026] The sources of the raw materials used in the following examples and comparative examples are as follows:

[0027] Polyoxypropylene polyoxyethylene ether: manufacturer is CNOOC Shell Petrochemical Co., Ltd., model number is SC56-32;

[0028] Hexafunctional polyoxyethylene polyoxypropylene ether: manufacturer: Changhua Chemical Technology Co., Ltd., model: CHE-628;

[0029] Hydrogenated hydroxy-terminated polybutadiene: manufactured by Japan Soda, model GI-2000;

[0030] 1,3,5-Tris(dimethylaminopropyl)hexahydrotriazine: CAS number is 15875-13-5;

[0031] 1,8-diazabicyclo[5.4.0]undec-7-ene: CAS number is 6674-22-2;

[0032] Hydroxyl-terminated fluorinated silicone oil: manufacturer: Great Wall Fluorinated New Material Technology Co., Ltd., model: NFS7200;

[0033] Oxalyl dihydrazide: CAS number is 996-98-5;

[0034] 3-Isocyanatepropyltrimethoxysilane: CAS number is 15396-00-6;

[0035] Trimethylolpropane: CAS number is 77-99-6;

[0036] Foam stabilizer: The manufacturer is Dow Chemical, model number is VORASURFDC5188.

[0037] Unless otherwise specified, other materials and reagents used in the examples can be obtained from commercial sources.

[0038] Example 1

[0039] A yellowing-resistant sponge comprises the following raw materials in parts by weight: 63 parts of aliphatic isocyanate, 6 parts of fluorohydroxy silicone oil, 50 parts of polyether polyol A, 14 parts of polyether polyol B, 18 parts of hydrogenated hydroxyl-terminated polybutadiene, 7 parts of an anti-yellowing chain extender, 1 part of a catalyst, 1.2 parts of a foam stabilizer, and 2 parts of water;

[0040] Wherein, the aliphatic isocyanate is isophorone diisocyanate, hexamethylene diisocyanate and 1,5-pentamethylene diisocyanate in a mass ratio of 1:1:0.8;

[0041] The fluorinated hydroxy silicone oil is a hydroxyl-terminated fluorinated silicone oil;

[0042] The polyether polyol A is polyoxypropylene polyoxyethylene ether;

[0043] The polyether polyol B is a hexafunctional polyoxyethylene polyoxypropylene ether;

[0044] The anti-yellowing chain extender is oxalyl dihydrazide, 3-isocyanate propyl trimethoxysilane and trimethylolpropane in a mass ratio of 1:1.2:3.6;

[0045] The catalyst is a main catalyst and a co-catalyst in a mass ratio of 1:0.016, the main catalyst is 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine, and the co-catalyst is stannous octoate;

[0046] The method for preparing the yellowing-resistant sponge comprises the following steps:

[0047] Aliphatic isocyanate and fluorohydroxy silicone oil were added to a reactor, and a co-catalyst was added. The mixture was mixed evenly, heated to 55°C, stirred and reacted for 3 hours under nitrogen atmosphere, then heated to 90°C and continued to react for 2.5 hours, and then cooled to 55°C and kept at a constant temperature. The mixture was allowed to stand for 48 hours to degas, thereby obtaining an isocyanate-terminated prepolymer A.

[0048] Add polyether polyol A, polyether polyol B, hydrogenated hydroxyl-terminated polybutadiene, anti-yellowing chain extender, primary catalyst, foam stabilizer and water into a constant temperature stirrer at 55°C, mix at a speed of 600 r / min for 2 minutes, and let stand at a constant temperature of 55°C for 48 hours to degas, to obtain material B;

[0049] The prepolymers A and B were mixed, and the prepolymers A and B were respectively injected into the head of a high-pressure foaming machine at high pressures of 55 bar and 35 bar. The stirring speed of the head was 5500 r / min, and the head pressure was 1.5 bar. After the materials were mixed at high speed for 5 seconds in the head, they were injected into the foaming box and aged in an oven at 80°C for 24 hours to obtain the yellowing-resistant sponge.

[0050] Example 2

[0051] A yellowing-resistant sponge comprises the following raw materials in parts by weight: 50 parts of aliphatic isocyanate, 4 parts of fluorohydroxy silicone oil, 45 parts of polyether polyol A, 10 parts of polyether polyol B, 15 parts of hydrogenated hydroxyl-terminated polybutadiene, 5 parts of yellowing-resistant chain extender, 0.5 parts of catalyst, 0.8 parts of foam stabilizer, and 1.5 parts of water;

[0052] Wherein, the aliphatic isocyanate is isophorone diisocyanate, hexamethylene diisocyanate and 1,5-pentane diisocyanate in a mass ratio of 1:1:0.5;

[0053] The fluorinated hydroxy silicone oil is a hydroxyl-terminated fluorinated silicone oil;

[0054] The polyether polyol A is polyoxypropylene polyoxyethylene ether;

[0055] The polyether polyol B is a hexafunctional polyoxyethylene polyoxypropylene ether;

[0056] The anti-yellowing chain extender is oxalyl dihydrazide, 3-isocyanate propyl trimethoxysilane and trimethylolpropane in a mass ratio of 1:1:3;

[0057] The catalyst is a main catalyst and a co-catalyst in a mass ratio of 1:0.01, the main catalyst is 1,8-diazabicyclo[5.4.0]undec-7-ene, and the co-catalyst is stannous octoate;

[0058] The method for preparing the yellowing-resistant sponge comprises the following steps:

[0059] Aliphatic isocyanate and fluorinated hydroxy silicone oil were added to a reactor, and a co-catalyst was added. The mixture was mixed evenly, heated to 50°C, stirred and reacted for 4 hours under nitrogen atmosphere, then heated to 80°C and continued to react for 3 hours, and then cooled to 50°C and kept at a constant temperature. The mixture was allowed to stand for 48 hours to degas, thereby obtaining an isocyanate-terminated prepolymer A.

[0060] Add polyether polyol A, polyether polyol B, hydrogenated hydroxyl-terminated polybutadiene, anti-yellowing chain extender, main catalyst, foam stabilizer and water into a constant temperature stirrer at 50°C, mix at a speed of 500 r / min for 3 minutes, and let stand at a constant temperature of 50°C for 48 hours to degas, to obtain material B;

[0061] The prepolymers A and B were mixed, and the prepolymers A and B were respectively injected into the head of a high-pressure foaming machine at high pressures of 55 bar and 35 bar. The stirring speed of the head was 5500 r / min, and the head pressure was 1.5 bar. After the materials were mixed at high speed for 5 seconds in the head, they were injected into the foaming box and aged in an oven at 60°C for 48 hours to obtain the yellowing-resistant sponge.

[0062] Example 3

[0063] A yellowing-resistant sponge comprises the following raw materials in parts by weight: 70 parts of aliphatic isocyanate, 8 parts of fluorohydroxy silicone oil, 60 parts of polyether polyol A, 20 parts of polyether polyol B, 20 parts of hydrogenated hydroxyl-terminated polybutadiene, 8 parts of an anti-yellowing chain extender, 2 parts of a catalyst, 1.5 parts of a foam stabilizer, and 3 parts of water;

[0064] Wherein, the aliphatic isocyanate is isophorone diisocyanate, hexamethylene diisocyanate and 1,5-pentamethylene diisocyanate in a mass ratio of 1:1:1.5;

[0065] The fluorinated hydroxy silicone oil is a hydroxyl-terminated fluorinated silicone oil;

[0066] The polyether polyol A is polyoxypropylene polyoxyethylene ether;

[0067] The polyether polyol B is a hexafunctional polyoxyethylene polyoxypropylene ether;

[0068] The anti-yellowing chain extender is oxalyl dihydrazide, 3-isocyanate propyl trimethoxysilane and trimethylolpropane in a mass ratio of 1:1.5:4;

[0069] The catalyst comprises a main catalyst and a co-catalyst in a mass ratio of 1:0.02, wherein the main catalyst comprises 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine and 1,8-diazabicyclo[5.4.0]undec-7-ene in a mass ratio of 1:0.6, and the co-catalyst is stannous octoate;

[0070] The method for preparing the yellowing-resistant sponge comprises the following steps:

[0071] Aliphatic isocyanate and fluorohydroxy silicone oil were added to a reactor, and a co-catalyst was added. The mixture was mixed evenly, heated to 60°C, stirred and reacted for 2 hours under nitrogen atmosphere, then heated to 100°C and continued to react for 2 hours, and then cooled to 60°C and kept at a constant temperature. The mixture was allowed to stand for 48 hours to degas, thereby obtaining an isocyanate-terminated prepolymer A.

[0072] Add polyether polyol A, polyether polyol B, hydrogenated hydroxyl-terminated polybutadiene, anti-yellowing chain extender, primary catalyst, foam stabilizer and water into a constant temperature stirrer at 60°C, mix at a speed of 700 r / min for 1 minute, and let stand at a constant temperature of 60°C for 48 hours to degas, to obtain material B;

[0073] The prepolymers A and B were mixed, and the prepolymers A and B were injected into the head of a high-pressure foaming machine at high pressures of 55 bar and 35 bar, respectively. The stirring speed of the head was 5500 r / min, and the head pressure was 1.5 bar. After the materials were mixed at high speed for 5 seconds in the head, they were injected into the foaming box and aged in an oven at 100° C. for 12 hours to obtain the yellowing-resistant sponge.

[0074] Example 4

[0075] The difference between Example 4 and Example 1 is that the total amount of the anti-yellowing chain extender added remains unchanged, and the mass ratio of oxalyl dihydrazide, 3-isocyanatepropyltrimethoxysilane and trimethylolpropane is 1:3.6:1.2.

[0076] Example 5

[0077] The difference between Example 5 and Example 1 is that the total amount of the anti-yellowing chain extender added remains unchanged, and the mass ratio of oxalyl dihydrazide, 3-isocyanatepropyltrimethoxysilane and trimethylolpropane is 3.6:1.2:1.

[0078] Comparative Example 1

[0079] The difference between Comparative Example 1 and Example 1 is that: in Comparative Example 1, hydrogenated hydroxy-terminated polybutadiene is not added, and polyether polyol A and polyether polyol B with a mass ratio of 25:7 are used to make up for the missing amount.

[0080] Comparative Example 2

[0081] The difference between Comparative Example 2 and Example 1 is that the total amount of the anti-yellowing chain extender added remains unchanged, oxalyl dihydrazide is not added, and 3-isocyanatepropyltrimethoxysilane and trimethylolpropane with a mass ratio of 1:3 are used to make up the missing amount.

[0082] Comparative Example 3

[0083] The difference between Comparative Example 3 and Example 1 is that the total amount of the anti-yellowing chain extender added remains unchanged, 3-isocyanatepropyltrimethoxysilane is not added, and oxalyl dihydrazide and trimethylolpropane with a mass ratio of 1:3.6 are used to make up the missing amount.

[0084] Comparative Example 4

[0085] The difference between Comparative Example 4 and Example 1 is that the total amount of the anti-yellowing chain extender added remains unchanged, trimethylolpropane is not added, and oxalyl dihydrazide and 3-isocyanatepropyltrimethoxysilane with a mass ratio of 1:1.2 are used to make up the missing amount.

[0086] Performance Testing

[0087] The sponges obtained in Examples 1-5 and Comparative Examples 1-4 were subjected to mechanical tests and yellowing resistance tests, respectively. The mechanical tests included tensile strength, elongation at break, tear strength, and ball rebound rate; the yellowing resistance tests included high temperature color difference, UVA resistance, and artificial sebum stain resistance tests.

[0088] The anti-UVA test conditions are: UVA wavelength is 340nm, ultraviolet light is exposed to 70℃±3℃ for 8h, and the radiation intensity is 0.89W / m 2 , condensed at 50°C ± 3°C for 4 hours, and cycled for 96 hours. High-temperature color difference testing conditions: hot-press the sponge at 195°C for 200 seconds in a flatbed vulcanizer. The color difference before and after hot pressing is measured, simulating the bra cup shaping process. Artificial sebum stain resistance testing conditions: evenly coat the sponge with a layer of artificial sebum (commercially available model PH1878). Place the coated sponge in a 60°C oven for 24 hours, then rinse with soapy water and dry. Repeat this process seven times, and measure the color difference before and after treatment. See Table 1 for specific data.

[0089] Table 1 Performance data of each group of sponges

[0090]

[0091]

[0092] As can be seen from Table 1, combined with the data of Example 1 and Example 4-5, the oxalyl dihydrazide content in Example 4 is insufficient, the hydrogen bond network density is reduced, the free radical quenching ability is sharply reduced, and oxidation is aggravated under high temperature or ultraviolet irradiation. At the same time, the lack of rigid support of oxalyl dihydrazide leads to reduced mechanical properties, and its trimethylolpropane is insufficient, resulting in a weakened hydrophobic barrier, tight stacking of molecular chains, increased risk of light scattering, and reduced freedom of molecular chains, resulting in a decrease in the rebound rate of falling balls, so that the mechanical properties and yellowing resistance of the sponge in Example 4 are lower than those in Example 1; the oxalyl dihydrazide in Example 5 is excessive, so its mechanical properties are better than those in Example 4, but due to insufficient 3-isocyanatepropyltrimethoxysilane and trimethylolpropane, the interface bonding force is weakened, the molecular chain is loose, the deformation resistance is weak, and the rebound rate of the sponge is significantly reduced. Therefore, when the mass ratio of oxalyl dihydrazide, 3-isocyanatepropyltrimethoxysilane and trimethylolpropane is 1:(1-1.5):(3-4), the mechanical properties, resilience and yellowing resistance of the sponge are all at a relatively good level.

[0093] Combining the data from Example 1 and Comparative Example 1, it can be seen that the absence of hydrogenated hydroxyl-terminated polybutadiene leads to an overall deterioration of mechanical properties and a significant decrease in yellowing resistance. This is likely because hydrogenated hydroxyl-terminated polybutadiene primarily provides flexible segments and weather resistance. Its absence increases molecular chain rigidity, while elongation at break and rebound rate decrease. Tensile strength may temporarily increase due to excessive isocyanate cross-linking, but toughness decreases. Furthermore, the hydrogenated structure in hydrogenated hydroxyl-terminated polybutadiene inhibits double bond oxidation. Its absence makes the material susceptible to ultraviolet attack, significantly increasing the yellowing index and decreasing UVA resistance.

[0094] The data of Example 1 and Comparative Examples 2-4 show that Example 1 significantly improves the mechanical properties and yellowing resistance of Comparative Examples 2-4. This may be because the absence of oxalyl dihydrazide causes the free radical capture ability to be lost, and oxidation reaction may be more likely to occur, affecting the integrity of the molecular chain, causing tensile strength and tear strength to decline. Simultaneously, oxalyl dihydrazide can also form hydrogen bonds with isocyanate groups, enhancing intermolecular forces, and its absence may cause mechanical properties to deteriorate. 3-isocyanate propyl trimethoxy silane can enhance interfacial bonding, and its absence may cause interfacial bonding to deteriorate, affecting the mechanical properties of the overall material, such as tensile strength and tear strength may decline. 3-isocyanate propyl trimethoxy silane can enhance interfacial bonding and provide a stable structure, and its absence may cause interfacial bonding to deteriorate, affecting the mechanical properties and yellowing resistance of the overall material to deteriorate. The cross-linking effect of hydroxymethylpropane has an important influence on the elasticity and strength of the sponge, and lacking it can cause the cross-linking density to decrease, affecting the decline in mechanical performance indicators, and the loose cross-linked network can also cause weather resistance and yellowing resistance to decline.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A yellowing-resistant sponge, characterized in that: The invention comprises the following raw materials in parts by weight: 50-70 parts of aliphatic isocyanate, 4-8 parts of fluorinated hydroxy silicone oil, 45-60 parts of polyether polyol A, 10-20 parts of polyether polyol B, 15-20 parts of hydrogenated hydroxy-terminated polybutadiene, 5-8 parts of anti-yellowing chain extender, 0.5-2 parts of catalyst, 0.8-1.5 parts of foam stabilizer and 1.5-3 parts of water; wherein the anti-yellowing chain extender is a combination of oxalyl dihydrazide, 3-isocyanate propyltrimethoxysilane and trimethylolpropane.

2. The anti-yellowing sponge according to claim 1, characterized in that The mass ratio of the oxalyl dihydrazide, 3-isocyanatepropyltrimethoxysilane and trimethylolpropane is 1: (1-1.5): (3-4).

3. The anti-yellowing sponge according to claim 1, characterized in that The polyether polyol A is polyoxypropylene polyoxyethylene ether; the polyether polyol B is hexafunctional polyoxyethylene polyoxypropylene ether.

4. The anti-yellowing sponge according to claim 1, characterized in that The aliphatic isocyanate is isophorone diisocyanate, hexamethylene diisocyanate and 1,5-pentamethylene diisocyanate in a mass ratio of 1:1:(0.5-1.5).

5. The anti-yellowing sponge according to claim 1, characterized in that: The catalyst comprises a main catalyst and a co-catalyst; the main catalyst is one or two of 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine and 1,8-diazabicyclo[5.4.0]undec-7-ene, and the co-catalyst is stannous octoate.

6. The anti-yellowing sponge according to claim 1, characterized in that The fluorinated hydroxy silicone oil is a hydroxyl-terminated fluorinated silicone oil.

7. The method for preparing the yellowing-resistant sponge according to any one of claims 1 to 6, characterized in that: The following steps are involved: Mixing aliphatic isocyanate, fluorinated hydroxy silicone oil and part of the catalyst to carry out polymerization reaction to obtain an isocyanate-terminated prepolymer A; Mixing polyether polyol A, polyether polyol B, hydrogenated hydroxyl-terminated polybutadiene, yellowing-resistant chain extender, remaining catalyst, foam stabilizer and water to obtain material B; The prepolymer material A and the prepolymer material B are mixed, foamed and matured in sequence to obtain a yellowing-resistant sponge.

8. The preparation method according to claim 7, characterized in that The polymerization reaction comprises reacting at 50-60° C. for 2-4 hours, then heating to 80-100° C. and continuing to react for 2-3 hours.

9. The method for preparing the yellowing-resistant sponge according to claim 7, wherein: The foaming method is high-pressure foaming, and the foaming pressure is 20-60 bar; the aging temperature is 60-100° C., and the aging time is 12-48 hours.

10. Use of the yellowing-resistant sponge according to any one of claims 1 to 6 in preparing bra sponge for underwear.

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