A macroporous polyurethane porous material, its preparation method and application

Abstract

The present invention belongs to the field of polymer material synthesis and processing technology, and specifically relates to a large-aperture polyurethane porous material and its preparation method and application. The large-aperture polyurethane porous material includes the following raw materials according to mass fractions: 35-50 parts of toluene diisocyanate, 5-15 parts of polymethylene polyphenyl polyisocyanate raw materials, 80-120 parts of polyester polyols, 2-6 parts of chain extenders, 0.5-2 parts of catalysts, 0.5-2 parts of foam stabilizers, 1-4 parts of emulsifiers, 2-6 parts of pore openers, and 3-5 parts of water. And foaming is carried out by a high-pressure foaming machine to prepare a large-aperture polyurethane porous material with a pore size of 6-9ppi.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthesis and processing of polymer materials, and particularly relates to a large-pore polyurethane porous material, a preparation method thereof and an application thereof. Background Art

[0002] Slag inclusion defects in the metal casting industry are a very important type of casting defects, accounting for more than half of the total defects. The control of slag inclusion defects mainly depends on the performance and use of castings. The more precise and harsh working condition castings have stricter restrictions on slag inclusion defects. How to reduce the slag inclusion ratio has become an important problem faced by casting production. With the continuous development of casting technology, high-temperature filtration technology has gradually become an indispensable means to reduce slag inclusion in castings. By using foam ceramic filters with different pore sizes for grading filtration, slag, dross and other non-metallic inclusions can be effectively removed. Currently, there are the following types of ceramic filters: alumina foam ceramic filter sheets with a temperature resistance of up to 1200 °C, which can be used for the filtration casting of copper-aluminum alloys; silicon carbide foam ceramic filter sheets with a temperature resistance of up to 1500 °C, which can be used for the filtration casting of molten iron; zirconia ceramic filter sheets with a temperature resistance of up to 1700 °C, which can be used for the filtration casting of molten steel.

[0003] Large-pore polyurethane porous materials are mainly used as template materials for producing large-pore ceramic filters. Since polyester-type polyurethane materials have higher bond energy and hydrogen bond interactions compared with polyether-type polyurethane materials, polyester sponges have higher tensile strength and tear strength. Therefore, polyester-type polyurethane porous materials are often selected as the template materials for ceramic filters. The polyurethane porous material is impregnated in different ceramic slurries, and then drained by a pressure roller and sintered to form a ceramic filter sheet. Currently, there are the following problems in the preparation of large-pore polyurethane porous materials: 1. The compression and rebound deformation rate of the sponge is too large. Because during the pressure roller operation after the sponge is impregnated with the ceramic slurry, the compression and rebound deformation rate of the sponge is large, and the size of the sponge after the pressure roller is unstable, resulting in a decrease in the yield of ceramic filter products; 2. It is impossible to prepare polyurethane porous materials with large pore diameters. For polyester sponges, the limit that can be achieved by the existing technology for the ppi value is above 10, that is, the number of pores per inch of the polyester sponge cannot (or is very difficult to) be less than 10; 3. The pore size distribution of the polyurethane porous material is uneven. After the polyurethane porous material is foamed, the pore size has a large difference in the three-dimensional distribution of the foam block, resulting in a very low material yield of the product.

[0004] The preparation of large-pore polyurethane porous materials has the above difficulties, and the main reasons are as follows: 1. The large-pore polyurethane porous materials are supported by a three-dimensional network skeleton structure. If the crosslinking degree of the molecular structure is insufficient during the polyurethane foaming process, the compression resilience of the network material will decrease; 2. During the foaming process of the sponge, the foaming reaction and the gel reaction proceed simultaneously, and the matching between them is crucial. The larger the pore size of the material, the lower the strength of the skeleton connectors connecting the grids as the grid gap increases during the process of forming the sponge with the ultimate pore size. After the sponge is foamed, if only a conventional foaming system is used, the gel speed will not be able to keep up with the foaming rate, resulting in insufficient skeleton strength to support the entire foam body, that is, the foam body will collapse, and thus a large-pore sponge cannot be formed; 3. Since the polyester polyol capped with a primary hydroxyl group has strong reactivity, if a strong gel catalyst or a highly reactive MDI is added during the foaming process, it is very easy to cause excessive post-curing gelation, and the sponge shrinks after curing, and a large-pore sponge cannot be formed either; 4. During the foaming process of the sponge, due to its own gravity and the influence of the side film and the bottom paper, it is very easy to cause a large difference in the pore size distribution of the material in the three-dimensional distribution of the foam block after foaming, resulting in a decrease in the material yield of qualified products.

[0005] The invention patent with the application number 201310182491.1 discloses a method for preparing a large-pore polyurethane network material by using a mixed polyol composed of polyether polyol, polymer polyether polyol and polyester polyol and foaming with toluene diisocyanate, and it is applied to the preparation of foam ceramics. However, this scheme can only prepare polyurethane network materials with a pore size above 10 ppi, and cannot prepare large-pore polyurethane porous materials with a pore size below 10 ppi. Moreover, the polyester polyol is capped with a primary hydroxyl group and the polyether polyol is capped with a secondary hydroxyl group, and the reactivity differences between them and isocyanate are relatively large. Direct foaming will cause disordered pores in the cell formation, and a polyurethane porous material with uniform pore size cannot be obtained. Summary of the Invention

[0006] To solve the deficiencies of the prior art, the present invention provides a large-pore polyurethane porous material, its preparation method and application. The present invention selects specific raw materials for synthesizing polyurethane materials, as well as the selection of blowing agents, catalysts and emulsifiers, which can be well applied to the foaming process of a high-pressure foaming machine, and solve problems such as difficult foaming and large material compression deformation rate of large-pore polyurethane porous materials. More importantly, a large-pore polyurethane porous material with uniform pore size can be prepared to meet the production material requirements of large-pore ceramic filters.

[0007] The technical solutions provided by the present invention are as follows:

[0008] A method for preparing a large-pore polyurethane porous material, comprising the following raw materials, measured by weight: 35-50 parts of toluene diisocyanate, 5-15 parts of polymethylene polyphenyl polyisocyanate raw materials, 80-120 parts of polyester polyol, 2-6 parts of chain extender, 0.5-2 parts of catalyst, 0.5-2 parts of foam stabilizer, 1-4 parts of emulsifier, 2-6 parts of pore opener, and 3-5 parts of water;

[0009] It includes the following steps:

[0010] 1) First, store the polyester polyol in a constant temperature storage tank, decompress and dehydrate it after heating, and then cool it to obtain component A;

[0011] 2) Evenly mix water, chain extender, catalyst, foam stabilizer, emulsifier and cell opener to obtain composite component B;

[0012] 3) Component A, component B, toluene diisocyanate, and polymethylene polyphenyl polyisocyanate are placed in different storage tanks in a high-pressure foaming machine, and the temperature is kept constant at 25°C. According to the raw material ratio, the raw material components are injected into the mixing head of the high-pressure foaming machine at a pressure of 20-50 bar. The mixing speed of the mixing head is 4000-6000 r / min, and the pressure of the mixing head is 1-2 bar. After the materials are mixed and reacted in the mixing head, they are injected into the foaming box and aged in an oven;

[0013] 4) The obtained blocky polyurethane foam is subjected to explosion treatment to obtain a full-skeleton open-cell foam, which is then cut to obtain a large-pore polyurethane porous material with a pore size of 6-9 ppi.

[0014] In the foaming of large-pore polyurethane porous materials, the larger the pore size of the sponge, the larger the grid gaps during its molding process, resulting in a large amount of collapse before enough gel enters the sponge after foaming, and the strength of the connector skeleton connecting the grids is insufficient, making it impossible to form a large-pore sponge.

[0015] Since the two NCO groups in the structure of diphenylmethane diisocyanate (MDI) are far apart and there are no substituents around, the steric hindrance of the NCO groups is low, while the two NCO groups in TDI are on the same benzene ring and have methyl substituents, which have a certain steric hindrance effect. Therefore, the reaction activity of the NCO groups in MDI is relatively high, and polymethylene polyphenyl polyisocyanates can quickly form a gel reaction. At the same time, the multifunctional isocyanate in MDI can play a cross-linking branching role, quickly enhance the strength of the grid connector skeleton, and solve the problem of collapse. At the same time, more branching cross-linking in the molecular structure provides better compression rebound performance for the material. This is exactly what the present invention needs for isocyanates using an efficient high-pressure foaming process, and it is also the reason why the present invention, in addition to using toluene diisocyanate, further adds polymethylene polyphenyl polyisocyanate raw materials.

[0016] Specifically, the toluene diisocyanate is a mixture of TDI80 and TDI65, and the weight fraction ratio of TDI80 to TDI65 is 1:2 to 1:3.

[0017] Specifically, the polymethylene polyphenyl polyisocyanate raw material is crude MDI. Among them, the molar proportion of MDI is 50%, and the molar proportion of polyisocyanate with a functionality greater than 2 is 50%.

[0018] Specifically, the general formula of the cell opener is as follows:

[0019]

[0020] Wherein:

[0021] 40 ≤ x ≤ 80, 30 ≤ y ≤ 60, x / y = 0.5 to 0.8;

[0022] The number average molecular weight is 2000 - 4000 g / mol.

[0023] The above cell opener is a polyoxyethylene and polyoxypropylene block copolymer with ethylene glycol as the initiator, and the number average molecular weight is 2000 - 4000 g / mol, wherein the content of polyoxyethylene is 50 - 80%.

[0024] In the TDI / MDI combined isocyanate foaming system, due to the high reaction activity of the terminal primary hydroxyl group of the polyester polyol and the relatively high activity of the isocyanate group in MDI, the closed cell rate of the prepared polyurethane foaming material is relatively high, and the material often shrinks during the post-curing process. The polyoxyethylene and polyoxypropylene block copolymer cell opener with ethylene glycol as the initiator is a low-foaming non-ionic surfactant. In the middle and late stages of the foaming initiation stage of polyurethane, as the reaction exotherms and the system temperature rises, the growth of the cell pores gradually stabilizes. The cell opener can effectively increase the surface tension of the cell membrane, making it easier for gas to break through each cell pore, promoting the connection between the pores, and ensuring that the material does not shrink during the post-curing process.

[0025] Specifically, the polyester polyol is obtained by esterification and polycondensation of adipic acid and diethylene glycol with trimethylolpropane as the initiator, and has a functionality of 2.5 - 3 and a hydroxyl value of 55 - 65 mg KOH / g.

[0026] Specifically, the catalyst is selected from any one or a mixture of more than one of 1,4-dimethylpiperazine, N-methylmorpholine, 2,2-dimorpholinodiethyl ether, or bis(dimethylaminoethyl) ether.

[0027] Specifically, the general formula of the polycarbonate diol chain extender is as follows:

[0028]

[0029] where 3 ≤ m ≤ 5;

[0030] The monomeric alcohol corresponding to R1 is 1,5-pentanediol or 1,6-hexanediol;

[0031] The hydroxyl value is 200 - 300 mg KOH / g.

[0032] The above polycarbonate group has relatively high thermal stability and bond energy. Using a short molecular chain polycarbonate diol as a chain extender and inserting the carbonate group into the polyurethane molecular chain can improve the strength and compression resilience performance of the material.

[0033] Specifically, the foam stabilizer is selected from any one or a mixture of several of TEGOSTAB B8301, TEGOSTAB B8335, or VORASURF DC1990.

[0034] Specifically, the general formula of the emulsifier is as follows:

[0035]

[0036] where 7 ≤ n ≤ 21, and the monomer corresponding to R2 is a saturated alkyl group of decanoic acid, dodecanoic acid, or tetradecanoic acid.

[0037] For example, it can be polyethylene glycol bis-saturated fatty acid ester, or polyethylene glycol bis-fatty acid ester with a polyethylene glycol polymerization degree of 7 - 21, or a saturated fatty acid being one of decanoic acid, dodecanoic acid, or tetradecanoic acid.

[0038] As a non-ionic emulsifier, polyethylene glycol bis-saturated fatty acid ester has good compatibility between the ester group structure in the molecule and the polyester-type polyurethane material. The hydrophilic EO group and the lipophilic alkyl group in its structural unit form a water-in-oil (W / O) emulsion system, which can emulsify and disperse the mixed reaction solution and thicken it at the initial stage of the foaming reaction, playing a role in improving the stability of the cell size after foaming.

[0039] The preparation method of the large-pore polyurethane porous material may specifically include the following steps:

[0040] 1) First, store the polyester polyol in a constant-temperature storage tank, heat it to 80 - 100 °C, carry out vacuum dehydration and degassing for 2 - 5 hours under a negative pressure of -0.05 to -0.09 MPa, and then cool it to 20 - 25 °C to obtain component A;

[0041] 2) Mix water, chain extender, catalyst, foam stabilizer, emulsifier, and cell opener evenly to obtain composite component B;

[0042] 3) Component A, component B, toluene diisocyanate, and polymethylene polyphenyl polyisocyanate are placed in different storage tanks in a high-pressure foaming machine, and the temperature is kept constant at 25°C. According to the raw material ratio, the raw material components are injected into the mixing head of the high-pressure foaming machine at a pressure of 20-50 bar. The mixing speed of the mixing head is 4000-6000 r / min, and the pressure of the mixing head is 1-2 bar. After the materials are mixed and reacted in the mixing head, they are injected into the foaming box and aged in an oven at 60°C for 24 hours;

[0043] 4) The obtained blocky polyurethane foam is subjected to blasting treatment to obtain a full-frame open-cell foam, and after cutting off the edge material, it is cut into required sizes to obtain a large-pore polyurethane porous material.

[0044] Since bubbles will be introduced into the raw materials during transportation and storage, especially polyester polyols with higher viscosity, the bubbles entrapped in the polyester polyols are difficult to be discharged automatically. If the polyester polyols are not pre-treated to remove bubbles, these bubbles will form tiny bubble nucleation points in the mixing head at the initial stage of foaming, which will play a role in refining the pores, making it difficult to prepare large-pore polyurethane porous materials.

[0045] The present invention also provides a large-pore polyurethane porous material prepared by the above preparation method, with a pore size of 6-9ppi, good pore size distribution uniformity, good tensile strength, elongation at break and tear strength, and a very low permanent compression deformation value.

[0046] The present invention also provides an application of the above-mentioned large-pore polyurethane porous material, and a large-pore ceramic filter is obtained by impregnating the large-pore polyurethane porous material with ceramic slurry, rolling and draining, and then sintering at high temperature.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1) The present invention uses toluene diisocyanate and polymethylene polyphenyl polyisocyanate to form a combined isocyanate, and utilizes the rapid gelation reaction and branching cross-linking effect of polymethylene polyphenyl polyisocyanate to solve the problem of easy collapse of large-pore polyurethane porous materials during foaming, while improving the compression rebound performance of the material and the dimensional stability of the large-pore polyurethane porous material during the sizing roller pressing operation in the ceramic filter production process.

[0049] 2) The present invention performs a pretreatment of heating and reducing pressure to remove bubbles on polyester polyols with high viscosity, which effectively removes bubbles entrapped in the raw materials and the original nucleation points in the foaming process, creating favorable conditions for the preparation of large-pore polyurethane porous materials.

[0050] 3) The present invention innovatively uses polycarbonate diol with short molecular chains as a chain extender. By utilizing the relatively high thermal stability and bond energy of the polycarbonate group, the strength and compression resilience performance of the material are effectively improved.

[0051] 4) The present invention uses a polyethylene glycol bis-saturated fatty acid ester type water-in-oil (W / O) emulsifier that has good compatibility with polyester-based polyurethane materials. At the initial stage of the foaming reaction, it emulsifies and disperses the mixed reaction liquid and thickens it, improving the stability of the cell size and solving the problem of unstable cell size in large-pore polyurethane porous materials.

[0052] 5) The present invention uses an opening agent of a polyoxyethylene and polyoxypropylene block copolymer with ethylene glycol as the initiator, effectively solving the problem of closed-cell shrinkage during the foaming process of the TDI / MDI combined isocyanate system in polyester-based polyurethane foam materials. Specific Embodiments

[0053] 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 intended to limit the scope of the present invention.

[0054] Unless otherwise specified, the test methods used in the examples are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are reagents and materials that can be obtained through commercial channels.

[0055] The specific brand raw materials used in the examples are described below. Toluene diisocyanate is WANNATE® TDI-80 and WANNATE® TDI-65 from Wanhua Chemical; polymethylene polyphenyl polyisocyanate is Lupranate M20S from BASF; polyester polyol is PF601 from Stepan (Nanjing) Chemical Co., Ltd., with a hydroxyl value of 60 mg KOH / g; foam stabilizers are TEGOSTAB B8301 and TEGOSTAB B8335 from Evonik Industries and VORASURF DC1990 from Dow Chemical; polycarbonate diol chain extender is ETERNACOLL PH-50 from Ube Industries, Ltd. of Japan, with a hydroxyl value of 224 mg KOH / g; emulsifier is PEG400DL from Hai'an Petrochemical Factory in Jiangsu Province, and its specific component is polyethylene glycol 400 dilaurate; opening agent is Pluronic PE6200 from BASF.

[0056] Examples 1-5

[0057] A preparation method of a large-pore polyurethane porous material provided in Examples 1-5 includes the following process steps:

[0058] (1)Store the polyester polyol PF601 in Examples 1 - 5 in a constant - temperature storage tank, heat it up to 90 °C, carry out vacuum dehydration and degassing for 3 hours under a negative pressure of - 0.08 MPa, and then cool it to 25 °C to obtain the pretreated polyester polyol component A;

[0059] (2)Mix the water, chain extender ETERNACOLL PH - 50, catalyst, foam stabilizer, emulsifier PEG400DL, and cell - opening agent Pluronic PE6200 in Examples 1 - 5 evenly to obtain the composite component B;

[0060] (3)Place component A and component B in Examples 1 - 5, as well as WANNATE® TDI - 80, WANNATE® TDI - 65, and Lupranate M20S in different storage tanks of a high - pressure foaming machine respectively, keep the temperature constant at 25 °C, and inject the raw material components into the mixing head of the high - pressure foaming machine through a pressure of 40 bar according to the raw material ratio. The stirring speed of the mixing head is 5000 r / min, the pressure of the mixing head is 1.5 bar. After the materials are mixed and reacted in the mixing head, they are injected into the foaming box and cured in an oven at 60 °C for 24 hours;

[0061] (4)Subject the obtained block - shaped polyurethane foam to blasting treatment to obtain a fully - skeleton open - cell foam. After cutting off the edge materials, cut it according to the required size to obtain the large - pore polyurethane porous material.

[0062] Comparative Examples 1 - 5

[0063] Comparative Example 1 uses T80 and T65 to replace Lupranate M20S on the basis of Example 1, that is, all isocyanates are T80 and T65.

[0064] The preparation method of Comparative Example 1 includes the following technological steps:

[0065] (1)Store the polyester polyol PF601 in Comparative Example 1 in a constant - temperature storage tank, heat it up to 90 °C, carry out vacuum dehydration and degassing for 3 hours under a negative pressure of - 0.08 MPa, and then cool it to 25 °C to obtain the pretreated polyester polyol component A;

[0066] (2)Mix the water, chain extender ETERNACOLL PH - 50, catalyst, foam stabilizer, emulsifier PEG400DL, and cell - opening agent Pluronic PE6200 in Comparative Example 1 evenly to obtain the composite component B;

[0067] (3) Place the component A, component B, WANNATE® TDI-80, and WANNATE® TDI-65 obtained from the above steps in different storage tanks of a high-pressure foaming machine, keep the temperature constant at 25°C, and inject the raw material components into the mixing head of the high-pressure foaming machine through a pressure of 40 bar according to the raw material ratio. The stirring speed of the mixing head is 5000 r / min, the pressure of the mixing head is 1.5 bar, and the material is injected into the foaming box after mixing and reacting in the mixing head, and cured in an oven at 60°C for 24 hours.

[0068] Comparative example 2 is obtained by removing the chain extender ETERNACOLL PH-50 from Example 2.

[0069] The preparation method of Comparative Example 2 includes the following process steps:

[0070] (1) Store the polyester polyol PF601 in Comparative Example 2 in a constant-temperature storage tank, heat it to 90°C, carry out vacuum dehydration and degassing for 3 hours under a negative pressure of -0.08 MPa, and then cool it to 25°C to obtain the pretreated polyester polyol component A;

[0071] (2) Mix the water, catalyst, foam stabilizer, emulsifier PEG400DL, and cell opener Pluronic PE6200 in Comparative Example 2 evenly to obtain the composite component B;

[0072] (3) Place the component A, component B, WANNATE® TDI-80, WANNATE® TDI-65, and Lupranate M20S obtained from the above steps in different storage tanks of a high-pressure foaming machine, keep the temperature constant at 25°C, and inject the raw material components into the mixing head of the high-pressure foaming machine through a pressure of 40 bar according to the raw material ratio. The stirring speed of the mixing head is 5000 r / min, the pressure of the mixing head is 1.5 bar, and the material is injected into the foaming box after mixing and reacting in the mixing head, and cured in an oven at 60°C for 24 hours;

[0073] (4) Subject the obtained block polyurethane foam to blasting treatment to obtain a fully skeletonized open-cell foam, cut off the edge materials, and then cut it according to the required size.

[0074] Comparative example 3 is obtained by removing the emulsifier PEG400DL from Example 3.

[0075] The preparation method of Comparative Example 3 includes the following process steps:

[0076] (1) Store the polyester polyol PF601 in Examples 1-5 in a constant-temperature storage tank, heat it to 90°C, carry out vacuum dehydration and degassing for 3 hours under a negative pressure of -0.08 MPa, and then cool it to 25°C to obtain the pretreated polyester polyol component A;

[0077] (2) Mix the water, chain extender ETERNACOLL PH-50, catalyst, foam stabilizer, and cell opener Pluronic PE6200 in Examples 1-5 uniformly to obtain composite component B;

[0078] (3) Place component A and component B obtained from the above steps, as well as WANNATE® TDI-80, WANNATE® TDI-65, and Lupranate M20S, respectively, in different storage tanks of a high-pressure foaming machine, keep the temperature constant at 25°C, and inject the raw material components into the mixing head of the high-pressure foaming machine through a pressure of 40 bar according to the raw material ratio. The stirring speed of the mixing head is 5000 r / min, the pressure of the mixing head is 1.5 bar, and the materials are injected into the foaming box after mixing and reacting in the mixing head, and cured in an oven at 60°C for 24 hours;

[0079] (4) Subject the obtained block polyurethane foam to blasting treatment to obtain an open-cell foam with a full skeleton. After cutting off the edge materials, cut it according to the required size.

[0080] Comparative Example 4 is based on Example 4, removing the cell opener Pluronic PE6200.

[0081] The preparation method of Comparative Example 4 includes the following process steps:

[0082] (1) Store the polyester polyol PF601 in Comparative Example 4 in a constant-temperature storage tank, heat it up to 90°C, and carry out vacuum dehydration and degassing for 3 hours under a negative pressure of -0.08 MPa, and then cool it to 25°C to obtain the pretreated polyester polyol component A;

[0083] (2) Mix the water, chain extender ETERNACOLL PH-50, catalyst, foam stabilizer, and emulsifier PEG400DL in Comparative Example 4 uniformly to obtain composite component B;

[0084] (3) Place component A and component B obtained from the above steps, as well as WANNATE® TDI-80, WANNATE® TDI-65, and Lupranate M20S, respectively, in different storage tanks of a high-pressure foaming machine, keep the temperature constant at 25°C, and inject the raw material components into the mixing head of the high-pressure foaming machine through a pressure of 40 bar according to the raw material ratio. The stirring speed of the mixing head is 5000 r / min, the pressure of the mixing head is 1.5 bar, and the materials are injected into the foaming box after mixing and reacting in the mixing head, and cured in an oven at 60°C for 24 hours.

[0085] Comparative Example 5 is based on Example 5, without performing temperature-raising and defoaming pretreatment on the polyester polyol, but directly foaming.

[0086] The preparation method of Comparative Example 5 includes the following process steps:

[0087] (1) Mix the water, chain extender ETERNACOLL PH-50, catalyst, foam stabilizer, and emulsifier PEG400DL in Comparative Example 5 evenly to obtain composite component A;

[0088] (2) Place the polyester polyol PF601, component A, WANNATE® TDI-80, WANNATE® TDI-65, and Lupranate M20S in different storage tanks of a high-pressure foaming machine respectively, keep the temperature constant at 25 °C, and inject the raw material components into the mixing head of the high-pressure foaming machine through a pressure of 40 bar according to the raw material ratio. The stirring speed of the mixing head is 5000 r / min, the pressure of the mixing head is 1.5 bar. After the materials are mixed and reacted in the mixing head, they are injected into the foaming box and cured in an oven at 60 °C for 24 hours;

[0089] (3) Subject the obtained block polyurethane foam to blasting treatment to obtain an open-cell foam with a full skeleton. After cutting off the edge materials, cut it according to the required size.

[0090] Table 1 shows the raw material compositions and parts of the examples and comparative examples:

[0091]

[0092] The foaming results and test results of Examples 1-5 and Comparative Examples 1-5 are shown in Table 2.

[0093] Table 2 shows the physical property test results of the examples and comparative examples

[0094]

[0095] Note: Standard deviation of pore size , where N is the total number of sampled foam cells,

[0096] d i is the pore size of any foam cell (unit: mm), d is the average sampled foam cell pore size (unit: mm), and the sampling positions of the sampled foam cells are fixed, distributed in the upper, middle, and lower levels of the foam body and different axial directions of each level.

[0097] From the test results of the above examples and comparative examples, it can be seen that the large-pore polyurethane porous materials prepared in Examples 1-5 have high strength, low compression deformation rate, good pore size distribution uniformity, and the pore sizes all reach below 10 ppi, and can be used as template materials for preparing large-pore ceramic filters; in Comparative Example 1, due to the lack of polymethylene polyphenyl polyisocyanate, it is impossible to quickly gel during the foaming process to form a skeleton structure with sufficient strength, and it collapses during the foaming and rising process, and a normal polyurethane foaming material cannot be obtained; in Comparative Example 2, since there is no polycarbonate group unit inserted into the polyurethane molecular chain, the strength and permanent compression deformation of the material are relatively large, and it cannot meet the production requirements of large-pore ceramic filters; in Comparative Example 3, due to the lack of emulsifier, after the polyurethane is foamed, the deviation of the cell size in the three-dimensional distribution of the foam body is relatively large, resulting in only part of the dimensions of the foam body meeting the requirements, and the final material yield is relatively low; in Comparative Example 4, due to the lack of the blowing agent Pluronic PE6200, the foaming process can start and reach the top normally, but due to the serious closed-cell of the cell units, the foam body shrinks during the post-curing process, and a normal polyurethane foaming material cannot be obtained either; in Comparative Example 5, since the high-viscosity polyester polyol was not heated and degassed before foaming, the bubbles entrapped in the polyester polyol played a nucleation role during foaming, refining the cell pores, resulting in the inability to prepare a large-pore polyurethane porous material with a pore size below 10 ppi.

[0098] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a large-pore polyurethane porous material, characterized in that: The raw materials include the following in parts by mass: 35-50 parts of toluene diisocyanate, 5-15 parts of polymethylene polyphenyl polyisocyanate raw materials, 80-120 parts of polyester polyol, 2-6 parts of chain extender, 0.5-2 parts of catalyst, 0.5-2 parts of foam stabilizer, 1-4 parts of emulsifier, 2-6 parts of cell opener, and 3-5 parts of water; It includes the following steps: 1) First, the polyester polyol is stored in a constant temperature storage tank, and after heating, it is decompressed, dehydrated and de-bubbled, and then cooled to obtain component A; 2) mixing water, chain extender, catalyst, foam stabilizer, emulsifier and cell opener uniformly to obtain composite component B; 3) Component A, component B, toluene diisocyanate, and polymethylene polyphenyl polyisocyanate raw materials are placed in different storage tanks in a high-pressure foaming machine, and the temperature is kept constant at 25° C. According to the raw material ratio, the raw material components are injected into the mixing head of the high-pressure foaming machine at a pressure of 20-50 bar, the mixing speed of the mixing head is 4000-6000 r / min, and the pressure of the mixing head is 1-2 bar. After the materials are mixed and reacted in the mixing head, they are injected into the foaming box and aged in an oven; 4) subjecting the obtained blocky polyurethane foam to blasting treatment to obtain a fully skeletonized open-cell foam, which is then cut to obtain a large-pore polyurethane porous material with a pore size of 6-9 ppi; The general formula of the pore opening agent is as follows: in: 40≤x≤80, 30≤y≤60, x / y=0.5 to 0.8; The number average molecular weight is 2000-4000 g / mol; The chain extender is a polycarbonate diol with a high hydroxyl value, and its general formula is as follows: in: 3≤m≤5； The monomer alcohol corresponding to R1 is 1,5-pentanediol or 1,6-hexanediol; The hydroxyl value is 200-300 mg KOH / g; The general formula of the emulsifier is as follows: Wherein, 7≤n≤21, and the monomer corresponding to R2 is a saturated alkyl group of dodecanoic acid, dodecanoic acid or tetradecanoic acid.

2. The method for preparing a large-pore polyurethane porous material according to claim 1, characterized in that: The toluene diisocyanate is a mixture of TDI80 and TDI65, and the mass ratio of TDI80 to TDI65 is 1:2 to 1:

3.

3. The method for preparing a large-pore polyurethane porous material according to claim 1, characterized in that: The polymethylene polyphenyl polyisocyanate raw material is crude MDI, wherein the molar amount of MDI accounts for 50%, and the molar amount of polyisocyanate with a functionality greater than 2 accounts for 50%.

4. The method for preparing a macroporous polyurethane material according to claim 1, characterized in that: The polyester polyol is obtained by esterification and polycondensation of adipic acid and diethylene glycol using trimethylolpropane as an initiator, and has a functionality of 2.5-3 and a hydroxyl value of 55-65 mg KOH / g.

5. The method for preparing a large-pore polyurethane porous material according to claim 1, characterized in that: The catalyst is selected from any one or more of 1,4-dimethylpiperazine, N-methylmorpholine, N-ethylmorpholine, 2,2-dimorpholinyl diethyl ether or bis(dimethylaminoethyl) ether.

6. The method for preparing a large-pore polyurethane porous material according to claim 1, characterized in that: The foam stabilizer is selected from any one of TEGOSTAB B8301, TEGOSTAB B8335 or VORASURF DC1990 or a mixture of several thereof.

7. A large-pore polyurethane porous material prepared according to the preparation method according to any one of claims 1 to 6.

8. An application of the large-pore polyurethane porous material according to claim 7, characterized in that: The large-pore ceramic filter is obtained by impregnating the large-pore polyurethane porous material with ceramic slurry, rolling and draining it, and then sintering it at high temperature.

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