Permanent white polyurethane sponge as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of polyurethane sponge, and particularly relates to permanent white polyurethane sponge as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, synthesizing an isocyanate group-terminated prepolymer special for the permanent white polyurethane sponge, and then preparing the permanent white polyurethane sponge by utilizing the synthesized isocyanate group-terminated prepolymer. The permanent white polyurethane sponge has the characteristics that the foaming speed is equivalent to that of the conventional polyurethane sponge, and the post-curing time is equivalent to that of the conventional polyurethane sponge, so that the permanent white polyurethane sponge provided by the invention has the advantage of being compatible with a traditional continuous flat foam production line for industrial production; meanwhile, the prepared permanent white sponge has the advantages of no yellowing (permanent white) after being exposed to direct sunlight for a long time (more than half a year), no yellowing after being tested for a long time (120 hours) for double-85 tests, good rebound resilience, good air permeability and the like, and is very suitable for being applied to the fields of manufacturing light / white bra cups, light / white fitted sheets, light / white mattresses and the like with high requirements on sponge yellowing.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane sponges, and particularly relates to a permanent white polyurethane sponge, a preparation method and application thereof. Background Art

[0002] The bra cups, fitted sheets, mattresses, and summer quilt core materials are all made of polyurethane sponge. Traditional polyurethane sponge is made by the foaming reaction of polyether / polyester polyols, aromatic isocyanates, blowing agents, and other additives. Due to the large number of benzene ring structures in its molecular structure, it easily generates benzoquinone-type color-developing groups when exposed to sunlight and high temperature and high humidity environments, causing the polyurethane sponge to turn yellow. When producing light / white bra cups, fitted sheets, mattresses, and summer quilts, the color difference caused by the yellowing of the sponge can easily show through the outer covering fabric, causing appearance defects. To solve this problem, the key solution is to prepare polyurethane sponges that will not yellow (permanently white) even after long-term exposure to direct sunlight and high temperature and high humidity environments. Considering the specific scenarios in which polyurethane sponge materials are used as bra cups, fitted sheets, mattresses, and summer quilt core materials, excellent resilience and breathability are also necessary material properties.

[0003] Those skilled in the art of polyurethane sponge materials are well aware that polyurethane sponges prepared by foaming using aliphatic isocyanates (without a benzene ring in their molecular structure), polyether / polyester polyols, blowing agents, and other additives have the characteristic of not yellowing (permanently whitening) even after prolonged exposure to direct sunlight. Compared to polyurethane sponges prepared using polyester polyols, polyurethane sponges prepared using polyether polyols have better hydrolysis resistance, better resistance to hydrolysis and yellowing, and better resilience and breathability. Therefore, using aliphatic isocyanates, polyether polyols, blowing agents, and other additives to prepare sponges that do not yellow (permanently whiten) even after prolonged exposure to direct sunlight or even after prolonged exposure to high temperature and high humidity environments, and that have good resilience and breathability, may be an effective method.

[0004] However, similar to the reason for the permanent whitening property, the lack of benzene rings in the molecular structure of aliphatic isocyanates leads to insufficient rigidity and excessive flexibility when foaming polyurethane sponges. This often results in foam collapse during the foaming process, resulting in a non-perfect sponge product. This phenomenon is particularly pronounced when using polyether polyols for foaming. When using polyester polyols for foaming, the numerous hydrogen bonds in the polyester polyols' molecular structure can compensate for the lack of rigidity caused by the missing benzene rings in the aliphatic isocyanates' molecular structure. Choosing the right polyester polyol can often overcome the foam collapse issue caused by the missing benzene rings in the isocyanate. However, this also leads to a secondary problem: poor sponge resilience and air permeability. Furthermore, the reactivity of aliphatic isocyanates is significantly lower than that of aromatic isocyanates, resulting in significantly slower foaming and maturation rates when using them compared to traditional sponges made with aromatic isocyanates, making them incompatible with conventional continuous flat foam production lines for industrial production. Therefore, solving the problems of insufficient rigidity of the molecular structure of polyurethane sponge, slow foaming speed and slow aging speed caused by the use of aliphatic isocyanate is the only way to prepare permanently white polyurethane sponge with excellent properties such as no yellowing (permanent white) after long-term exposure to direct sunlight, no yellowing (permanent white) after long-term exposure to high temperature and high humidity environment, good resilience and air permeability. Summary of the Invention

[0005] To address the deficiencies of the prior art, the present invention provides a permanently white polyurethane sponge, its preparation method, and applications. The technical solution of the present invention addresses the problems of insufficient molecular structural rigidity, slow foaming speed, and slow maturation speed of polyurethane sponges caused by using aliphatic isocyanates and polyether polyols as raw materials. The sponge has a foaming speed and maturation time comparable to those of conventional polyurethane sponges, making it compatible with traditional continuous flat foam production lines for industrial production. Furthermore, the prepared permanently white polyurethane sponge exhibits advantages such as resistance to yellowing (permanent whitening) when exposed to direct sunlight for extended periods (greater than six months), resistance to yellowing after extended periods (120 hours) in the Double 85 test, and excellent resilience and breathability.

[0006] The technical solutions provided by the present invention are as follows:

[0007] A method for preparing a permanent white polyurethane sponge comprises the following steps:

[0008] 1) preparing component B by prepolymerization, wherein component B is a mixture of modified aliphatic isocyanates, which is obtained by reacting raw materials including aliphatic isocyanates, a first polyether polyol, and a first catalyst;

[0009] 2) mixing component A and component B and foaming them to obtain a permanent white polyurethane sponge foam, wherein component A includes a second polyether polyol, a blowing agent, a second composite catalyst, a surfactant, and a chain extender;

[0010] 3) aging the permanent white polyurethane sponge foam to obtain a permanent white polyurethane sponge.

[0011] In the above technical solution:

[0012] 1) To address the problem of insufficient rigidity of common aliphatic isocyanates due to the lack of benzene rings, a two-step foaming method is adopted: first synthesizing a prepolymer and then foaming to obtain a permanent white polyurethane sponge. The aliphatic isocyanate is prepolymerized with a high-functionality first polyether polyol with the assistance of a catalyst to obtain an isocyanate group-terminated prepolymer with sufficient molecular rigidity.

[0013] 2) To address the problem that the foaming and maturation rates of polyurethane sponges prepared using aliphatic isocyanates are much slower than those prepared using traditional aromatic isocyanates, making them incompatible with traditional continuous flat-foam production lines for industrial production, in step 2), a combination of multiple catalysts is adopted, so that the catalytic reaction in step 2) includes a front-end strong foaming stage and a rear-end heat-excited thermosensitive strong gel stage, which accelerates the overall foaming rate of step 2) and can also accelerate the maturation rate of step 3).

[0014] Based on the above technical solution:

[0015] 1) The preparation method has a foaming speed and a maturation time comparable to those of conventional polyurethane sponges, making it compatible with traditional continuous flat foam production lines for industrial production.

[0016] 2) The obtained permanent white polyurethane sponge has the advantages of not turning yellow (permanent white) when exposed to direct sunlight for a long time (more than half a year), not turning yellow for a long time (120 hours) in the double 85 test, and having good resilience and breathability.

[0017] Specifically, in step 1), the aliphatic isocyanate is selected from any one or more of IPDI, HMDI or HDI.

[0018] Specifically, in step 1), the first polyether polyol is selected from any one or more of polyether polyol GEP 628, CHE 828 or CHE628.

[0019] Specifically, in step 1), the first catalyst is selected from any one or more of polyurethane organic tin catalysts T9 and T12 or organic bismuth catalysts MC-710 and MC-810.

[0020] Specifically, in step 2), the second polyether polyol includes a polyether polyol a having a weight-average molecular weight of 3000 to 12000 g / mol, a functionality of 3 to 6, a hydroxyl value of 28 to 56 mgKOH / g, and a viscosity of 300 to 3000 mPa·s, and a high-EO polyether polyol b having a hydroxyl value of 40 to 50 mgKOH / g, a viscosity of 300 to 3000 mPa·s, and an EO content of 50% to 85%.

[0021] Specifically, in step 2): the second composite catalyst is selected from any one or more of bis(dimethylaminoethyl) ether, alcoholamine, piperazine, morpholine, imidazole or nitrogen heterocyclic catalysts.

[0022] Preferably, the aliphatic isocyanate is IPDI;

[0023] Preferably, the first polyether polyol is polyether polyol GEP 628;

[0024] Preferably, the first catalyst is polyurethane organotin catalyst T9;

[0025] Preferably, the polyether polyol a is selected from any one or more of polyether polyol 5616, polyether polyol 330N, polyether polyol CHE828 or polyether polyol GEP 628;

[0026] Preferably, the polyether polyol b is selected from any one or more of polyether polyol ZS-3602, CHK 350D or CHE 5602;

[0027] Preferably, the second composite catalyst is a composite of bis(dimethylaminoethyl) ether, alcoholamine and nitrogen heterocyclic catalysts.

[0028] More preferably, in step 1), the amount of the aliphatic isocyanate added is 350 to 360 parts; the amount of the first polyether polyol added is 290 to 310 parts; the amount of the first catalyst added is 0.01 to 0.03 parts; the NCO value of the mixture of modified aliphatic isocyanates is 12% to 25%;

[0029] More preferably, in step 2), component B is added in an amount of 100 to 300 parts; polyether polyol a is added in an amount of 80 to 90 parts, and polyether polyol b is added in an amount of 10 to 20 parts; the bis(dimethylaminoethyl) ether catalyst is added in an amount of 0.1 to 0.3 parts, the alcoholamine catalyst is added in an amount of 0.8 to 1.2 parts, and the nitrogen heterocyclic catalyst is added in an amount of 1 to 2 parts.

[0030] Specifically, in step 2), the foaming agent is selected from any one or more of water, dichloromethane, or dichloroethane, preferably water. The amount of the foaming agent added is 5 to 9 parts.

[0031] Specifically, in step 2), the chain extender is a small molecule diol chain extender, preferably PEG400. The amount of the chain extender added is 1.5 to 3 parts.

[0032] Specifically, in step 2), the surfactant is a polyether-modified polysiloxane surfactant, preferably commercially available silicone oil L-580, and the amount of the surfactant added is 1 to 2 parts.

[0033] Specifically, in step 1), the reaction temperature is 70-90°C, and the reaction time is 4-6 hours. Preferably, the reaction temperature is 80°C, and the reaction time is 5 hours.

[0034] Specifically, in step 2), the foaming temperature is room temperature (preferably 20-30°C). Preferably, the foaming temperature is 25°C.

[0035] Specifically, in step 3), the mixture is allowed to stand for aging at room temperature (preferably 20-30°C) for 48-72 hours. Preferably, the aging temperature is 25°C for 48 hours.

[0036] The preparation method of the permanent white polyurethane sponge specifically comprises the following steps:

[0037] 1) Under the protection of inert gas, add aliphatic isocyanate, the first polyether polyol and the first catalyst into a reaction kettle, and heat to the reaction temperature while stirring and mixing to carry out prepolymerization;

[0038] 2) The second polyether polyol, the blowing agent, the second composite catalyst, the surfactant, and the chain extender are prepared in proportion and stirred at a speed of 600-1000 RPM (preferably 800 RPM) for 50-70 seconds (preferably 60 seconds) to obtain component A after uniform mixing; component B and component A are weighed in proportion and stirred at a speed of 1400-1600 RPM (preferably 1500 RPM) for 4-6 seconds (preferably 5 seconds) using a blender to obtain a mixture, which is then immediately poured into a mold with a built-in release film for foaming to obtain a permanent white polyurethane sponge;

[0039] 3) The permanent white polyurethane sponge foam is matured to obtain a permanent white polyurethane sponge, which is then cut as required to obtain a finished permanent white polyurethane sponge.

[0040] A more specific preparation method comprises the following steps:

[0041] 1) Preparation of modified IPDI mixture (isocyanate group-terminated prepolymer)

[0042] Under inert gas protection, IPDI, polyether polyol GEP 628, and T9 were added to a reactor, heated to 80°C while stirring and mixing, and reacted at 80°C with stirring for 5 hours. Then, samples were taken to test the NCO value once every hour until the difference between the two test results was less than 3%, indicating that the modified IPDI mixture (isocyanate group-terminated prepolymer) used in the present invention has been successfully prepared.

[0043] 2) Preparation of Yongbai polyurethane sponge foam

[0044] The raw materials in component A were mixed in proportion and stirred at 800 RPM for 60 seconds to obtain component A. Components B and A were weighed in proportion and stirred 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 and foamed to obtain a permanent white polyurethane sponge.

[0045] 3) Curing of the Yongbai polyurethane sponge

[0046] The foam obtained by foaming in step 2) is left to stand and mature for 48 hours to obtain a fully matured permanent white polyurethane sponge foam, which is then cut into a desired shape as required to obtain a finished permanent white polyurethane sponge product.

[0047] The present invention also provides a permanent white polyurethane sponge prepared by the above preparation method.

[0048] Specifically: The material's ball rebound is 35% to 50%, and its air permeability is 500 to 1200 l / m 2 / s, which is comparable to the polyether polyurethane sponge prepared from conventional aromatic isocyanate, and can provide products with excellent touch and breathability.

[0049] The present invention also provides an application of the permanent white polyurethane sponge for making light-colored bra cups, white bra cups, light-colored fitted sheets, white fitted sheets, light-colored mattresses or white mattresses.

[0050] In general, the beneficial effects of the present invention are as follows:

[0051] The permanently white polyurethane sponge prepared by the preparation method provided by the present invention has the characteristics of a foaming speed and a maturation time comparable to those of conventional polyurethane sponges, making it compatible with traditional continuous flat-foam production lines for industrial production; at the same time, it has the advantages of not turning yellow (permanently white) when exposed to direct sunlight for a long time (more than half a year), not turning yellow for a long time (120 hours) in the double 85 test, and having good resilience and air permeability. It is very suitable for use in the production of light / white bra cups, light / white fitted sheets, light / white mattresses, and other fields that have high requirements for sponge yellowing. DETAILED DESCRIPTION

[0052] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0053] Unless otherwise specified, the test methods used in the examples are conventional methods; the materials and reagents used are commercially available reagents and materials unless otherwise specified.

[0054] IPDI, Chinese name is isophorone diisocyanate.

[0055] Polyether polyol GEP 628 is commercially available.

[0056] Organotin catalyst T9 is commercially available.

[0057] Polyether polyol 5616 is commercially available.

[0058] Polyether polyol 330N is commercially available.

[0059] Polyether polyol CHE 828 is commercially available.

[0060] Polyether polyol ZS-3602 is commercially available.

[0061] PEG 400 is commercially available.

[0062] Silicone oil L-580 is commercially available.

[0063] DMEA, Chinese name is dimethylethanolamine.

[0064] Catalyst A1 is commercially available.

[0065] Catalyst A33 is commercially available.

[0066] DBU, Chinese name 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0067] The NCO value can be measured using existing technology.

[0068] Example 1

[0069] The preparation of permanent white polyurethane sponge comprises the following steps:

[0070] 1) Preparation of modified IPDI mixture (isocyanate group-terminated prepolymer)

[0071] The NCO value was set to 19.43%, and 300 g of GEP 628, 354 g of IPDI, and 0.02 g of T9 were taken respectively. Under inert gas protection, IPDI, polyether polyol GEP 628, and T9 were added to a reactor, and the temperature was raised to 80° C. while stirring and mixing. The reaction was stirred at 80° C. for 5 hours. Then, sampling and testing of the NCO value were started, and the test was conducted once every hour until the difference between the two test results was less than 3%, indicating that the modified IPDI mixture (isocyanate group-terminated prepolymer) used in the present invention has been successfully prepared.

[0072] 2) Preparation of Yongbai polyurethane sponge foam

[0073] 90 g of polyether polyol 5616, 10 g of polyether polyol ZS-3602, 1.5 g of PEG400, 7 g of water, 2 g of L-580, 1.1 g of DMEA, 0.2 g of A1, and 1.5 g of DBU were weighed and stirred at 800 RPM for 60 seconds to obtain component A. 213 g of the modified IPDI mixture prepared in step 1) was weighed as component B. Components B and A were stirred in a blender 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 and foamed to obtain a permanent white polyurethane sponge.

[0074] 3) Curing of the Yongbai polyurethane sponge

[0075] The foam obtained by foaming in step 2) is left to stand and mature for 48 hours to obtain a fully matured permanent white polyurethane sponge foam, which is then cut into a desired shape as required to obtain a finished permanent white polyurethane sponge product.

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is that in step 2) in the preparation of the permanent white polyurethane sponge foam, the polyether polyol 5616 in component A is replaced with polyether polyol 330N, and the amount of the modified IPDI mixture added in component B is 201 g. The rest is the same as in Example 1.

[0078] Example 3

[0079] The difference between Example 3 and Example 1 is that in step 2) of preparing the permanent white polyurethane sponge foam, the polyether polyol 5616 in component A is replaced with polyether polyol CHE 828, and the amount of the modified IPDI mixture added in component B is 187 g. Other steps are the same as in Example 1.

[0080] Example 4

[0081] The difference between Example 4 and Example 1 is that in step 2) of preparing the permanent white polyurethane sponge foam, the polyether polyol 5616 in component A is replaced with polyether polyol GEP 628, and the amount of the modified IPDI mixture added in component B is 187 g. The rest is the same as in Example 1.

[0082] Example 5

[0083] The difference between Example 5 and Example 1 is that in step 2), the catalyst is replaced with 2.1 g A33 and 0.7 g T9, and the rest is the same as in Example 1.

[0084] Example 6

[0085] The difference between Example 6 and Example 1 is that the catalyst in step 2) is replaced with 2 g of DBU, and the rest is the same as Example 1.

[0086] Example 7

[0087] The difference between Example 7 and Example 1 is that step 1) preparation of the modified IPDI mixture is omitted, component B is IPDI, and the added amount is 108 g. Other steps are the same as in Example 1.

[0088] Comparative Example 1

[0089] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses traditional aromatic isocyanate TDI as component B, with an addition amount of 84g; the addition amount of blowing agent water is 3g; the catalysts are 0.8g A33 and 0.2g T9; and the rest are consistent with Example 1.

[0090] The test results of the physical properties of the sponges prepared in Examples 1 to 7 and Comparative Example 1 are shown in Table 1.

[0091] Table 1 Sponge physical properties test results

[0092] Test items Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Time to top (s) 85 81 86 93 More than one day 64 More than one day 76 Foaming phenomenon normal normal normal normal Unable to foam normally normal Collapse normal Surface drying time (hours) 2 2 2 2 —— More than one day —— 2 Density (kg / m3) 38 36 42 40 —— 57 —— 34 Tensile strength (KPa) 117 126 124 135 —— 108 —— 121 Elongation at break (%) 105 92 95 86 —— 111 —— 93 Air permeability (l / m2 / s) 1200 1017 784 500 —— 368 —— 1129 Ball rebound (%) 46 50 39 35 —— 33 —— 53 Yellowing performance after half a year of exposure to sunlight No yellowing No yellowing No yellowing No yellowing —— No yellowing —— Severe yellowing Yellowing performance at 85RH / 85℃ / 120h No yellowing No yellowing No yellowing No yellowing —— No yellowing —— Severe yellowing

[0093] As can be seen from the physical property test data in Table 1, Example 7, when using IPDI as the black material for foaming, experienced bubble collapse, and a normal sponge foam could not be obtained. This is because the lack of aromatic rings in the IPDI molecular structure results in insufficient rigidity, which is unable to lock the gas generated by foaming, causing the gas to overflow, resulting in bubble collapse. In contrast, Examples 1 to 4 modified IPDI by means of a prepolymer to increase its rigidity by increasing its functionality. When the modified IPDI mixture (isocyanate group-terminated prepolymer) was used as the black material for foaming, foaming was normal, and the top-to-bottom time and surface-drying time were basically the same as those when the traditional aromatic isocyanate was used as the black material for foaming in Comparative Example 1. Although the ball rebound performance of the polyurethane sponges obtained in Examples 1 and 2 was slightly worse than that of Comparative Example 1, the air permeability, tensile strength, and elongation at break were basically equivalent to those of Comparative Example 1. Moreover, they did not yellow after being exposed to sunlight for half a year, and did not yellow after 120 hours of double 85 test, indicating a true permanent white polyurethane sponge; whereas the polyurethane sponge obtained in Comparative Example 1 showed severe yellowing.

[0094] In Example 5, under the premise of using a modified IPDI mixture (isocyanate group-terminated prepolymer) as the black material, the catalyst system (A33 / T9) used as the catalyst for foaming when using a traditional aromatic isocyanate as the black material foaming failed to foam normally. This is because the reactivity of the modified IPDI mixture is much lower than that of the traditional aromatic isocyanate, and the conventional catalyst cannot catalyze the reaction of the formulation. In contrast, Examples 1 to 4 use a combination of multiple catalysts to construct a concept of strong foaming in the front section and heat-activated heat-sensitive strong gel in the back section, accelerating the foaming speed and curing speed. The formulation can foam normally to obtain a normal sponge foam, and the top-up time and surface-free time are basically the same as those in Comparative Example 1 when the traditional aromatic isocyanate is used as the black material foaming. When Example 6 uses a single DBU catalyst for catalytic foaming, although the top time is also very fast, the curing speed is very slow, and it cannot be adapted to the traditional continuous flat foam production line for large-scale production. However, Examples 1 to 4 can be adapted to the traditional continuous flat foam production line for large-scale production because the top time and surface dry time are basically the same as when the traditional aromatic isocyanate is used as the black material for foaming.

[0095] As can be seen from Examples 1 to 7 and Comparative Example 1, by adopting a two-step foaming method of first synthesizing a prepolymer, and then prepolymerizing an aliphatic isocyanate and a high-functionality polyether polyol with the assistance of a catalyst, an isocyanate group-terminated prepolymer with sufficient molecular rigidity is obtained; supplemented by adopting a technical solution of constructing a strong foaming in the front stage and a heat-sensitive strong gel with thermal excitation of the back stage reaction by compounding multiple catalysts, the foaming speed and the curing speed are accelerated. The prepared permanent white polyurethane sponge has a foaming speed and a curing time comparable to those of conventional polyurethane sponges, and is compatible with traditional continuous flat foam production lines for industrial production. At the same time, the prepared permanent white sponge has the advantages of not yellowing (permanent white) when exposed to direct sunlight for a long time (more than half a year), not yellowing for a long time (120 hours) in the double 85 test, and having good resilience and breathability. It is very suitable for use in the production of light / white bra cups, light / white fitted sheets, light / white mattresses, and other fields with high requirements for sponge yellowing.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a permanent white polyurethane sponge, characterized in that: The following steps are involved: 1) preparing component B by prepolymerization, wherein component B is a mixture of modified aliphatic isocyanates, which is obtained by reacting raw materials including aliphatic isocyanates, a first polyether polyol, and a first catalyst; 2) mixing component A and component B and foaming them to obtain a permanent white polyurethane sponge foam, wherein component A includes a second polyether polyol, a blowing agent, a second composite catalyst, a surfactant, and a chain extender; 3) aging the permanent white polyurethane sponge foam to obtain a permanent white polyurethane sponge.

2. The method for preparing the permanent white polyurethane sponge according to claim 1, wherein: In step 1): The aliphatic isocyanate is selected from any one or more of IPDI, HMDI or HDI; and / or, the first polyether polyol is selected from any one or more of polyether polyol GEP 628, CHE 828 or CHE 628; And / or, the first catalyst is selected from any one or more of polyurethane organotin catalysts T9, T12 or organobismuth catalysts MC-710, MC-810; In step 2): And / or, the second polyether polyol includes a polyether polyol a having a weight-average molecular weight of 3000 to 12000 g / mol, a functionality of 3 to 6, a hydroxyl value of 28 to 56 mgKOH / g, and a viscosity of 300 to 3000 mPa·s, and a high-EO polyether polyol b having a hydroxyl value of 40 to 50 mgKOH / g, a viscosity of 300 to 3000 mPa·s, and an EO content of 50% to 85%; And / or, the second composite catalyst is selected from any one or more of bis(dimethylaminoethyl) ether, alcoholamine, piperazine, morpholine, imidazole or nitrogen heterocyclic catalysts.

3. The method for preparing the permanent white polyurethane sponge according to claim 2, wherein: The aliphatic isocyanate is IPDI; The first polyether polyol is polyether polyol GEP 628; The first catalyst is polyurethane organotin catalyst T9; The polyether polyol a is selected from any one or more of polyether polyol 5616, polyether polyol 330N, polyether polyol CHE 828 or polyether polyol GEP 628; The polyether polyol b is selected from any one or more of polyether polyol ZS-3602, CHK-350D or CHE-5602; The second composite catalyst is a composite of bis(dimethylaminoethyl) ether, alcoholamine and nitrogen heterocyclic catalysts.

4. The method for preparing the permanent white polyurethane sponge according to claim 3, wherein: In step 1): The amount of the aliphatic isocyanate added is 350 to 360 parts; the amount of the first polyether polyol added is 290 to 310 parts; the amount of the first catalyst added is 0.01 to 0.03 parts; the NCO value of the mixture of modified aliphatic isocyanates is 12% to 25%; In step 2): The addition amount of component B is 100 ~ 300 parts; In component A, the addition amount of polyether polyol a is 80 to 90 parts, the addition amount of polyether polyol b is 10 to 20 parts; the addition amount of bis(dimethylaminoethyl) ether catalyst is 0.1 to 0.3 parts, the addition amount of alcoholamine catalyst is 0.8 to 1.2 parts, and the addition amount of nitrogen heterocyclic catalyst is 1 to 2 parts.

5. The method for preparing the permanent white polyurethane sponge according to claim 1, wherein In step 2): The foaming agent is selected from any one or more of water, dichloromethane or dichloroethane; the amount of the foaming agent added is 5 to 9 parts; The chain extender is a small molecule diol chain extender; the addition amount of the chain extender is 1.5 to 3 parts; The surfactant is a polyether-modified polysiloxane surfactant; the added amount of the surfactant is 1 to 2 parts.

6. The method for preparing the permanent white polyurethane sponge according to claim 1, wherein: In step 1), the reaction temperature is 70-90°C and the reaction time is 4-6 h; In step 2), the foaming temperature is room temperature; In step 3), the mixture is allowed to stand for aging at room temperature for 48 to 72 hours.

7. The method for preparing the permanent white polyurethane sponge according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) Under the protection of inert gas, add the aliphatic isocyanate, the first polyether polyol and the first catalyst into the reaction kettle, and heat to the reaction temperature while stirring and mixing to carry out the reaction; 2) The second polyether polyol, blowing agent, second composite catalyst, surfactant, and chain extender are prepared in proportion and stirred at 600-1000 RPM for 50-70 seconds to obtain component A after uniform mixing; component B and component A are weighed in proportion and stirred at 1400-1600 RPM for 4-6 seconds to obtain a mixture, which is then immediately poured into a mold with a built-in release film for foaming to obtain a permanent white polyurethane sponge; 3) The permanent white polyurethane sponge foam is matured to obtain a permanent white polyurethane sponge, which is then cut to obtain a finished permanent white polyurethane sponge.

8. A permanent white polyurethane sponge prepared according to the preparation method according to any one of claims 1 to 7.

9. The permanent white polyurethane sponge according to claim 8, characterized in that: The material's ball rebound is 35% to 50% and its air permeability is 500 to 1200 l / m 2 / s.

10. An application of the permanent white polyurethane sponge according to claim 8 or 9, characterized in that: For light-colored bra cups, white bra cups, light-colored fitted sheets, white fitted sheets, light-colored mattresses, or white mattresses.