A white polyurethane sponge, its preparation method and application

Abstract

The present application belongs to the technical field of polyurethane sponge, and particularly relates to a Yongbai polyurethane sponge, a preparation method and application thereof. The present application first synthesizes an isocyanate group-terminated prepolymer special for Yongbai polyurethane sponge, and then uses the synthesized isocyanate group-terminated prepolymer to prepare the Yongbai polyurethane sponge. The present application has the characteristics of a foaming speed equivalent to that of conventional polyurethane sponge and a post-curing time equivalent to that of conventional polyurethane sponge, so that the Yongbai polyurethane sponge provided by the present application has the advantage of being compatible with traditional continuous flat bubble production lines for industrial production. Meanwhile, the prepared Yongbai sponge has the advantages of not yellowing (Yongbai) after being exposed to direct sunlight for a long time (more than half a year), not yellowing for a long time (120 hours) in a double-eight-five test, good resilience and air permeability, and is very suitable for being applied to the fields of high requirements for sponge yellowing, such as manufacturing light / white bra cups, light / white bedclothes, light / white mattresses and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polyurethane sponge, and particularly relates to a Yongbai polyurethane sponge, a preparation method and application thereof. BACKGROUND

[0002] The cup, bed cover and mattress in the chest circumference and the core material in the summer cooling quilt all use polyurethane sponge material, and the traditional polyurethane sponge is prepared by foaming reaction of polyether / polyester polyol, aromatic isocyanate, foaming agent and other additives. Because a large number of benzene ring structures exist in the molecular structure, the polyurethane sponge is easy to generate quinone color groups under sunlight and high temperature and high humidity environment, so that the polyurethane sponge turns yellow. When producing light / white cups, bed covers, mattresses and summer cooling quilts, the color difference caused by yellowing of the sponge is easy to be shown through the outer covering fabric, causing appearance defects. In order to solve this problem, it is a key method to prepare a polyurethane sponge which does not yellow (Yongbai) under long-term exposure to direct sunlight and does not yellow (Yongbai) under long-term exposure to high temperature and high humidity environment. Considering the specific scene of the polyurethane sponge material applied to the cup, bed cover, mattress and summer cooling quilt core material, excellent resilience and air permeability are also necessary material properties.

[0003] Polyurethane sponge material field technicians know that the polyurethane sponge prepared by using aliphatic isocyanate (no benzene ring in the molecular structure), polyether / polyester polyol, foaming agent and other additives has the characteristics of not yellowing (Yongbai) under long-term exposure to direct sunlight; compared with the polyurethane sponge prepared by polyester polyol, the polyurethane sponge prepared by polyether polyol has better hydrolysis resistance, better hydrolysis yellowing resistance, better resilience and better air permeability. Therefore, it is possible to use aliphatic isocyanate, polyether polyol, foaming agent and other additives to prepare a sponge with the characteristics of not yellowing (Yongbai) under long-term exposure to direct sunlight, not yellowing (Yongbai) under long-term exposure to high temperature and high humidity environment, good resilience and good air permeability.

[0004] However, due to the same reason as bringing the ever-white characteristics, because of the lack of benzene ring in the molecular structure of aliphatic isocyanate, the molecular structure of the sponge is insufficient in rigidity and excessive in flexibility, and the collapse phenomenon often occurs during foaming, and normal sponge products cannot be obtained. This phenomenon is particularly evident when using polyether polyol to foam. When using polyester polyol to foam, the large number of hydrogen bonds in the molecular structure of the polyester polyol can make up for the problem of insufficient rigidity of the sponge molecular structure caused by the lack of benzene ring in the molecular structure of aliphatic isocyanate. By selecting a suitable polyester polyol, the collapse problem caused by the lack of benzene ring in the isocyanate can often be solved; but this will also bring another problem, that is, the poor resilience and air permeability of the sponge caused by the use of polyester polyol. In addition, the reactivity of aliphatic isocyanate is much lower than that of aromatic isocyanate, which makes the foaming speed and curing speed of the polyurethane sponge prepared by using aliphatic isocyanate much slower than that of the traditional sponge prepared by using aromatic isocyanate, and it cannot be compatible with the traditional continuous flat bubble production line for industrial production. Therefore, solving the problems of insufficient rigidity of the polyurethane sponge molecular structure, slow foaming speed and curing speed caused by the use of aliphatic isocyanate is the only way to prepare ever-white polyurethane sponge with excellent properties such as non-yellowing under long-term exposure to direct sunlight (ever-white), non-yellowing under long-term exposure to high temperature and high humidity environment (ever-white), good resilience and air permeability. SUMMARY

[0005] To solve the problems of the prior art, the present application provides an ever-white polyurethane sponge, a preparation method and application thereof. The technical solution of the present application solves the problems of insufficient rigidity of the polyurethane sponge molecular structure, slow foaming speed and curing speed caused by using aliphatic isocyanate and polyether polyol as raw materials, has the characteristics of equivalent foaming speed and equivalent curing time to conventional polyurethane sponge, and has the advantage of being compatible with the traditional continuous flat bubble production line for industrial production. At the same time, the ever-white polyurethane sponge prepared has the advantages of non-yellowing under long-term exposure to direct sunlight (ever-white), non-yellowing under double 85 test for a long time (120 hours), good resilience and air permeability.

[0006] The technical solution provided by the present application is as follows:

[0007] A preparation method of an ever-white polyurethane sponge, comprising the following steps:

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

[0009] 2) mixing component A and component B to foam, to obtain the white polyurethane sponge foam, wherein component A comprises a second polyether polyol, a foaming agent, a second compounded catalyst, a surfactant and a chain extender;

[0010] 3) curing the white polyurethane sponge foam to obtain the white polyurethane sponge.

[0011] In the above technical solution:

[0012] 1) In view of the problem of insufficient rigidity caused by the absence of benzene ring in ordinary aliphatic isocyanate, a two-step foaming idea of first synthesizing a prepolymer and then foaming to obtain the white polyurethane sponge foam is adopted. The aliphatic isocyanate is pre-polymerized with a high-functionality first polyether polyol under the assistance of a catalyst to obtain an isocyanate group-terminated prepolymer with sufficient molecular structure rigidity.

[0013] 2) In view of the problem that the foaming speed and curing speed of polyurethane sponge prepared by using aliphatic isocyanate are much slower than those of traditional sponge prepared by using aromatic isocyanate, and cannot be compatible with traditional continuous flat bubble production line for industrial production, in step 2), multiple catalysts are compounded, so that the catalytic reaction of step 2) includes a front strong foaming stage and a rear reaction heat excited heat-sensitive strong gelation stage, which accelerates the overall foaming speed of step 2) and can accelerate the curing speed of step 3).

[0014] Based on the above technical solution:

[0015] 1) The foaming speed of the preparation method is equivalent to that of conventional polyurethane sponge, and the curing time is equivalent to that of conventional polyurethane sponge, which can be compatible with traditional continuous flat bubble production line for industrial production;

[0016] 2) The obtained white polyurethane sponge has the advantages of not yellowing (white) for a long time (more than half a year) under direct sunlight, not yellowing for a long time (120 hours) in double 85 test, good resilience and air permeability, etc.

[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 organotin catalyst T9, T12 or organobismuth catalyst MC-710, MC-810.

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

[0021] Specifically, in step 2), the second complex catalyst is selected from any one or more of a bis(dimethylaminoethyl) ether type, an alcohol amine type, a piperazine type, a morpholine type, an imidazole type, or a nitrogen heterocycle type catalyst.

[0022] Preferably, the aliphatic isocyanate is IPDI.

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

[0024] Preferably, the first catalyst is a 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 CHE 828, 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 complex catalyst is a complex of a bis(dimethylaminoethyl) ether type, an alcohol amine type, and a nitrogen heterocycle type catalyst.

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

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

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

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

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

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

[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 standing and curing temperature is room temperature (preferably 20-30°C), and the curing time is 48-72 h. Preferably, the curing temperature is 25°C, and the curing time is 48 h.

[0036] The preparation method of the Yongbai polyurethane sponge specifically includes the following steps:

[0037] 1) Under the protection of inert gas, an aliphatic isocyanate, a first polyether polyol and a first catalyst are added to a reaction kettle, and the mixture is stirred and heated to a reaction temperature, and a prepolymer is prepared;

[0038] 2) The second polyether polyol, the foaming agent, the second compounded catalyst, the surfactant and the chain extender are proportioned and stirred at a speed of 600-1000 RPM (preferably 800 RPM) for 50-70 s (preferably 60 s) to obtain component A. Component B and component A are weighed according to the proportion, and a mixer is used to stir the mixture at a speed of 1400-1600 RPM (preferably 1500 RPM) for 4-6 s (preferably 5 s) to obtain a mixed material, which is then immediately poured into a mold with a release film to foam, thereby obtaining a Yongbai polyurethane sponge foam body;

[0039] 3) The Yongbai polyurethane sponge foam body is cured to obtain a Yongbai polyurethane sponge, which is then cut according to requirements to obtain a Yongbai polyurethane sponge finished product.

[0040] The more specific preparation method includes the following steps:

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

[0042] IPDI, polyether polyol GEP 628, T9 were added into a reaction kettle under inert gas protection, mixed and heated to 80℃ while stirring, and stirred at 80℃ for 5h; then sampling test NCO value was started, tested once every hour, until the difference between two test results was less than 3%, indicating that the modified IPDI mixture (isocyanate group end-capped prepolymer) used in the application was successfully prepared.

[0043] 2) Preparation of Yongbai polyurethane sponge foam

[0044] The raw materials in the A component were proportioned and stirred at a speed of 800 RPM for 60s, and after uniform mixing, component A was obtained. Component B and component A were weighed according to the proportion and stirred with a blender at a speed of 1500 RPM for 5s to obtain a mixture, and then the mixture was immediately poured into a mold with a built-in release film to foam to obtain Yongbai polyurethane sponge foam.

[0045] 3) Curing of Yongbai polyurethane sponge foam

[0046] After the foam obtained by foaming in step 2) was cured for 48h, the Yongbai polyurethane sponge foam was obtained, which was cut into the required shape according to the requirements to obtain the Yongbai polyurethane sponge finished product.

[0047] The application also provides the Yongbai polyurethane sponge prepared by the preparation method.

[0048] Specifically, the ball rebound of the material is 35% ~ 50%, and the air permeability is 500 ~ 1200 l / m 2 , which is comparable to the polyether polyurethane sponge prepared by conventional aromatic isocyanate, and can provide products with excellent touch and air permeability.

[0049] The application also provides the application of Yongbai polyurethane sponge, which is used to make light-colored bra cups, white bra cups, light-colored bed covers, white bed covers, light-colored mattresses or white mattresses.

[0050] Overall, the beneficial effects of the application are as follows:

[0051] Using the preparation method provided by the application, the Yongbai polyurethane sponge prepared has the characteristics of foaming speed comparable to conventional polyurethane sponge and curing time comparable to conventional polyurethane sponge, which makes it have the advantage of being compatible with traditional continuous flat foam production line for industrial production; at the same time, it has the advantages of not yellowing (Yongbai) for a long time (more than half a year) under direct sunlight, not yellowing for a long time (120 hours) in double-eight-five test, good resilience and air permeability, etc., which is very suitable for application in the field of high yellowing requirement of sponge, such as making light / white bra cups, light / white bed covers, light / white mattresses, etc. DETAILED DESCRIPTION

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

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

[0054] IPDI, the Chinese name is isophorone diisocyanate.

[0055] Polyether polyol GEP 628 can be purchased.

[0056] Organotin catalyst T9 can be purchased.

[0057] Polyether polyol 5616 can be purchased.

[0058] Polyether polyol 330N can be purchased.

[0059] Polyether polyol CHE 828 can be purchased.

[0060] Polyether polyol ZS-3602 can be purchased.

[0061] PEG400 can be purchased.

[0062] Silicone oil L-580 can be purchased.

[0063] DMEA, the Chinese name is dimethyl ethanolamine.

[0064] Catalyst A1 can be purchased.

[0065] Catalyst A33 can be purchased.

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

[0067] The measurement of NCO value can use the prior art.

[0068] Example 1

[0069] The preparation of Yongbai polyurethane sponge includes the following steps:

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

[0071] Set the NCO value to 19.43%, respectively, take 300g GEP 628, 354g IPDI, 0.02g T9; under inert gas protection, IPDI, polyether polyol GEP 628, T9 are added into the reaction kettle, mixed and heated to 80℃ under stirring, and stirred at 80℃ for 5h; then start sampling test NCO value, test once every hour, until the difference between two test results is less than 3%, which means that the modified IPDI mixture (isocyanate group end-capped prepolymer) used in the application has been successfully prepared.

[0072] 2) Preparation of Yongbai polyurethane sponge foam

[0073] Take 90g polyether polyol 5616, 10g polyether polyol ZS-3602, 1.5g PEG400, 7g water, 2g L-580, 1.1g DMEA, 0.2g A1, 1.5g DBU and stir at 800RPM for 60s, mix uniformly to obtain component A. Take 213g modified IPDI mixture prepared in step 1) as component B, and stir component B and component A with a blender at 1500RPM for 5s to obtain a mixture, then immediately pour the mixture into a mold with built-in release film to foam to obtain Yongbai polyurethane sponge foam.

[0074] 3) Curing of Yongbai polyurethane sponge foam

[0075] After the foam obtained in step 2) is placed and cured for 48h, the Yongbai polyurethane sponge foam is obtained, which is cut into the required shape as Yongbai polyurethane sponge finished product.

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is that in the preparation of Yongbai polyurethane sponge foam in step 2), the polyether polyol 5616 in component A is replaced by polyether polyol 330N, and the amount of modified IPDI mixture in component B is 201g, and the others are consistent with Example 1.

[0078] Example 3

[0079] The difference between Example 3 and Example 1 is that in the preparation of Yongbai polyurethane sponge foam in step 2), the polyether polyol 5616 in component A is replaced by polyether polyol CHE 828, and the amount of modified IPDI mixture in component B is 187g, and the others are consistent with Example 1.

[0080] Example 4

[0081] Example 4 differs from Example 1 in that in Step 2) preparation of polyurethane sponge foam body, the polyether polyol 5616 in component A is replaced by polyether polyol GEP 628, the amount of modified IPDI mixture in component B is 187 g, and the rest is consistent with Example 1.

[0082] Example 5

[0083] Example 5 differs from Example 1 in that in Step 2) the catalyst is replaced by 2.1 g of A33 and 0.7 g of T9, and the rest is consistent with Example 1.

[0084] Example 6

[0085] Example 6 differs from Example 1 in that in Step 2) the catalyst is replaced by 2 g of DBU, and the rest is consistent with Example 1.

[0086] Example 7

[0087] Example 7 differs from Example 1 in that there is no Step 1) preparation of modified IPDI mixture, component B is IPDI, and the amount added is 108 g, and the rest is consistent with Example 1.

[0088] Comparative Example 1

[0089] Comparative Example 1 differs from Example 1 in that Comparative Example 1 uses traditional aromatic isocyanate TDI as component B, the amount added is 84 g; the amount of foaming agent water added is 3 g; the catalyst is 0.8 g of A33 and 0.2 g of T9; and the rest is consistent with Example 1.

[0090] The physical properties of the sponge prepared in Examples 1-7 and Comparative Example 1 are shown in Table 1.

[0091] Table 1 Physical properties of sponge test results

[0092] Test item 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 Failed to foam normally Normal Collapse Normal Skin dry time (h) 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 sunlight exposure No yellowing No yellowing No yellowing No yellowing —— No yellowing —— Severe yellowing Yellowing performance at 85 RH / 85°C / 120 h No yellowing No yellowing No yellowing No yellowing —— No yellowing —— Severe yellowing

[0093] From the physical property test data in Table 1, it can be seen that the foaming of Example 7 using IPDI as the black material occurs with a collapse phenomenon, and a normal sponge bubble body cannot be obtained. This is because the lack of aromatic rings in the molecular structure of IPDI leads to insufficient rigidity, which cannot lock the gas generated by foaming, resulting in a collapse phenomenon. In comparison, Examples 1-4 modify IPDI by pre-polymerization to increase its rigidity by increasing its functionality. When the modified IPDI mixture (isocyanate group end-capped pre-polymer) is used as the black material for foaming, the foaming is normal, and the time to peak and the surface drying time are basically the same as those of Comparative Example 1 using traditional aromatic isocyanate as the black material for foaming. Although the falling ball rebound performance of the polyurethane sponge obtained in Examples 1 and 2 is slightly worse than that of Comparative Example 1, the air permeability, tensile strength, and elongation at break are basically the same as those of Comparative Example 1, and there is no yellowing after being exposed to sunlight for half a year, and no yellowing after 120 hours of testing according to the Shuangbawu standard, which is a truly white polyurethane sponge; whereas the polyurethane sponge obtained in Comparative Example 1 is severely yellowed.

[0094] In Example 5, the catalyst system (A33 / T9) used when traditional aromatic isocyanate is used as the black material for foaming cannot be used as the catalyst for foaming when the modified IPDI mixture (isocyanate group end-capped pre-polymer) is used as the black material, because the reaction activity of the modified IPDI mixture is much lower than that of traditional aromatic isocyanate, and the conventional catalyst cannot catalyze the reaction of the formula material. In comparison, Examples 1-4 use a variety of catalysts to build a strong foaming in the front stage and a heat-sensitive strong gel in the back stage, which accelerates the foaming speed and the curing speed, and the formula material can be normally foamed to obtain a normal sponge bubble body, and the time to peak and the surface drying time are basically the same as those of Comparative Example 1 using traditional aromatic isocyanate as the black material for foaming. Although the time to peak is also very fast when a single DBU catalyst is used for catalytic foaming in Example 6, the curing speed is very slow, and it cannot be adapted to the traditional continuous flat foaming production line for large-scale production. Examples 1-4 can be adapted to the traditional continuous flat foaming production line for large-scale production because the time to peak and the surface drying time are basically the same as those of traditional aromatic isocyanate as the black material for foaming.

[0095] From Examples 1-7 and Comparative Example 1, by taking the two-step method of first synthesizing prepolymer, foaming, pre-polymerizing aliphatic isocyanate with high functionality polyether polyol with the aid of catalyst to obtain isocyanate group terminated prepolymer with sufficient rigid molecular structure; supplemented by taking a variety of catalysts to compound to build a strong foaming front section and a heat-sensitive strong gel of the reaction heat excitation in the rear section, to speed up the foaming speed and curing speed, the prepared Yongbai polyurethane sponge has the characteristics of equivalent foaming speed and equivalent curing time of conventional polyurethane sponge, and can be compatible with traditional continuous flat bubble production line for industrial production; at the same time, the prepared Yongbai sponge has the advantages of non-yellowing (Yongbai) for a long time (more than half a year) exposed to direct sunlight, non-yellowing for a long time (120 hours) in double 85 test, good resilience and air permeability, and is very suitable for application in the field of high requirements for sponge yellowing such as making light / white bra cup, light / white bed cover, light / white mattress, etc.

[0096] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of a white polyurethane sponge, characterized in that, The method comprises the following steps: 1) preparing component B by prepolymerization, the component B being a mixture of modified aliphatic isocyanate or a mixture of modified IPDI or a mixture of modified HMDI, which is obtained by reacting raw materials comprising aliphatic isocyanate or IPDI or HMDI, a first polyether polyol and a first catalyst; 2) mixing component A and component B and then foaming to obtain a white polyurethane sponge body, wherein component A comprises a second polyether polyol, a foaming agent, a second compounded catalyst, a surfactant and a chain extender, the second compounded catalyst being a compounded product of bis(dimethylaminoethyl) ether, alcohol amine and nitrogen heterocyclic catalysts, the nitrogen heterocyclic catalyst being 1,8-diazabicyclo[5.4.0]undec-7-ene DBU, the addition amount of the bis(dimethylaminoethyl) ether catalyst being 0.1-0.3 parts, the addition amount of the alcohol amine catalyst being 0.8-1.2 parts, and the addition amount of the nitrogen heterocyclic catalyst being 1-2 parts; 3) curing the white polyurethane sponge body to obtain a white polyurethane sponge; The first polyether polyol is selected from any one or more of polyether polyols GEP 628, CHE 828 or CHE 628; The second polyether polyol comprises a polyether polyol a with a weight average molecular weight of 3000-12000 g / mol, a functionality of 3-6, a hydroxyl value of 28-56 mgKOH / g and a viscosity of 300-3000 mPa·s, and a high-EO polyether polyol b with a hydroxyl value of 40-50 mgKOH / g, a viscosity of 300-3000 mPa·s and an EO content of 50%-85%.

2. The method for preparing a white polyurethane sponge according to claim 1, characterized in that: In step 1): The aliphatic isocyanate is selected from HDI; 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.

3. The method for preparing a white polyurethane sponge according to claim 2, characterized in that: 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.

4. The method for preparing a white polyurethane sponge according to claim 3, characterized in that: In step 1): The addition amount of the aliphatic isocyanate or IPDI or HMDI is 350-360 parts; the addition amount of the first polyether polyol is 290-310 parts; the addition amount of the first catalyst is 0.01-0.03 parts; the NCO value of the mixture of modified aliphatic isocyanate or modified IPDI or modified HMDI is 12%-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 80-90 parts, and the addition amount of polyether polyol b is 10-20 parts.

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

6. The preparation method of the white polyurethane sponge according to claim 1, characterized in that: 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 sponge is cured at room temperature for 48-72 h.

7. Process for the preparation of white polyurethane sponges according to any one of claims 1 to 6, characterized in that, Comprising the following steps: 1) Under the protection of inert gas, the aliphatic isocyanate or IPDI or HMDI, the first polyether polyol and the first catalyst are added into a reaction kettle, and the mixture is stirred and heated to the reaction temperature, and then the reaction is carried out; 2) The second polyether polyol, the foaming agent, the second compounded catalyst, the surfactant and the chain extender are proportionally prepared, and are stirred at a speed of 600-1000 RPM for 50-70 s, and then component A is obtained after being uniformly mixed; component B and component A are proportionally weighed, and are mixed by a blender at a speed of 1400-1600 RPM for 4-6 s to obtain a mixture, which is immediately poured into a mold with an embedded release film to foam, and a white polyurethane sponge foam body is obtained; 3) The white polyurethane sponge foam body is cured to obtain a white polyurethane sponge, which is then cut to obtain a white polyurethane sponge product.

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

9. The white polyurethane sponge according to claim 8, characterized by: The material has a ball rebound of 35%-50% and an air permeability of 500-1200 L / (m²·s).

10. Use of the white polyurethane sponge according to claim 8 or 9, characterized in that: It is used for making light-colored bra cups, white bra cups, light-colored bed covers, white bed covers, light-colored bed pads or white bed pads. It is used for making light-colored bra cups, white bra cups, light-colored bed covers, white bed covers, light-colored bed pads or white bed pads.