Polyurethane foaming composition, polyurethane foam, preparation method and application thereof

Abstract

The present invention proposes a polyurethane foam composition, polyurethane foam and its preparation method and application, which belongs to the technical field of thermal insulation materials and can solve the problem that thermal conductivity cannot be further reduced and the cost is high. Wherein, the polyurethane foam composition includes the following components by weight: 100 parts of dry white material; 25-35 parts of LBA foaming agent; 1-2 parts of low boiling point foaming agent; 2-8 parts of foaming aid; 130-174 parts of black material; wherein the low boiling point foaming agent is a low boiling point alkane compound with a boiling point below 0°C; the foaming aid is nitrogen or carbon dioxide. This scheme adopts a foaming system of LBA+low boiling point foaming agent+nucleating agent, which helps to form bubble nuclei with fine pores inside the foaming agent system, and can simultaneously obtain low thermal conductivity and low density at low cost. At the same time, other physical and chemical properties have not been significantly deteriorated.

Description

Technical Field

[0001] The invention belongs to the field of thermal insulation materials, and in particular relates to a polyurethane foam composition, polyurethane foam, and a preparation method and application thereof. Background Art

[0002] Polyurethane rigid foam plastics are widely used in the refrigeration industry due to their excellent thermal insulation performance and high specific strength. As people's requirements for energy conservation become higher and higher, emission reduction regulations in various countries are becoming more and more stringent. The current mainstream high-efficiency technology is to add VIP panels (vacuum insulation panels) to the side panels or back panels of refrigerators, but VIP panels are expensive.

[0003] The industry has been researching polyurethane materials with ultra-low thermal conductivity to partially replace VIP boards to reduce costs. Thermal conductivity is an important indicator to measure the thermal conductivity of polyurethane materials, and has a direct impact on thermal insulation performance. The lower the thermal conductivity, the worse the thermal conductivity of the material and the better its thermal insulation performance. Therefore, in order to obtain excellent thermal insulation performance, the thermal conductivity of the material needs to be reduced as much as possible. The foaming agent used in polyurethane materials can effectively prevent the transfer of heat by introducing bubbles or voids, thereby affecting the thermal conductivity of the final foam. At present, the most commonly used is the pure LBA foaming system, but the cost of polyurethane materials manufactured using the pure LBA system is still relatively high. At present, the amount of LBA used has reached a bottleneck. If the amount continues to increase, the stability of the foaming process will decrease, and other physical and chemical properties will deteriorate. The thermal conductivity of polyurethane materials cannot be further reduced, but the cost will increase significantly.

[0004] Patent CN115073694A discloses a low-density ultra-low thermal conductivity rigid polyurethane foam, which uses LBA foaming agent with a low boiling point foaming agent, and adds methyl formate modifier to make the reaction more thorough and the foam density more uniform. However, the thermal conductivity of the rigid polyurethane foam provided in the patent is still between 16.7 and 17.2 mW / m·K, and the density is 28 kg / m 3 When the amount of foaming agent is increased in the system to further reduce the thermal conductivity, other physical and chemical properties will deteriorate. For example, the density will increase further, and it will be difficult to further reduce the thermal conductivity to below 16mW / m·K. This will also increase the cost, limiting the further improvement of the performance of polyurethane foam materials.

[0005] Patent CN112063004A discloses an environmentally friendly high thermal insulation polyurethane insulation layer, which discloses a scheme of using LBA as a foaming agent and MFT as a foaming aid, i.e. a nucleating agent. MFT is an isomer of perfluoroolefin, and although it can promote nucleation, obtain more dense pores, and reduce thermal conductivity, it is expensive, and the polyurethane foam prepared by this system has a high density, which is not conducive to reducing production costs. In addition, fluorine-containing foaming agents damage the ozone layer, which is not conducive to environmental protection.

[0006] Patent CN106832181A discloses a polyurethane foam material, which uses cyclopentane and isopentane as foaming agents and nitrogen or carbon dioxide as nucleating agents. Although it can significantly reduce the thermal conductivity of conventional foaming systems, the thermal conductivity is still greater than 19mW / m·K, which cannot replace VIP boards and does not meet the latest energy efficiency requirements. In addition, the premixing process of the nucleating agent and the combined polyether requires an ultra-high pressure of 12-15MPa, which has high requirements for equipment, is difficult to operate, and the mixing effect is not ideal. In addition, the long-term storage stability is low and the safety risk is high.

[0007] Based on the above analysis, it can be seen that the existing polyurethane foam system cannot take into account both low thermal conductivity and other properties at the same time, the foaming insulation effect is not ideal, and the cost is high and the environmental protection is poor, which limits the application of polyurethane foam materials in industrialization. Summary of the invention

[0008] In view of at least one shortcoming in the prior art, the present invention provides a polyurethane foam composition, a polyurethane foam, and a preparation method and application thereof, which improves the foaming system to obtain an ultra-low thermal conductivity while reducing costs.

[0009] The first aspect of the present invention provides a polyurethane foam composition, which comprises the following components in parts by weight:

[0010]

[0011] The low-boiling-point foaming agent is a low-boiling-point alkane compound with a boiling point below 0°C; and the foaming aid is nitrogen or carbon dioxide.

[0012] The polyurethane foam composition provided by the above technical solution adopts a foaming system of LBA foaming agent + low boiling point foaming agent + nucleating agent (nitrogen or carbon dioxide), eliminates the methyl formate modifier in the existing system, and adds low-cost nitrogen or carbon dioxide as an auxiliary agent. Nitrogen or carbon dioxide is used in combination with the low boiling point foaming agent to promote each other and synergistically promote the formation of small pore bubble nuclei inside the foaming system, so that the system does not need to increase the amount of foaming agent to obtain a better foaming effect and achieve an ultra-low thermal conductivity. At the same time, nitrogen or carbon dioxide is more environmentally friendly than fluorine-containing nucleating agents, and after being added, it will not have a significant effect on the effects of other components in the system, and other physical and chemical properties have not been significantly deteriorated.

[0013] In some embodiments of the first aspect, the low boiling point foaming agent is n-butane, isobutane, or a mixture of n-butane and isobutane in any proportion. The technical solution defines specific types of low boiling point foaming agents, n-butane and isobutane exist in gas form at room temperature, which helps to form bubbles during the foaming process, and promotes the formation of bubbles in the foaming system together with the foaming aid nitrogen or dioxide, which has a good foaming effect and is low in cost.

[0014] In some embodiments of the first aspect, the dry white material comprises 89-96 parts of a combined polyether, 2-4 parts of a surfactant, 1-4 parts of a catalyst and 1-3 parts of water. In this technical solution, the dry white material is prepared by mixing the above components to obtain the desired performance and stability of the final foam material.

[0015] In some embodiments of the first aspect, the black material is polymerized MDI, the viscosity of the polymerized MDI at 25° C. is 200 to 400 mPa·s, and the isocyanate content is 30 to 32%. In the technical solution, the performance of the black material is limited to form a stable polyurethane network structure and ensure the physical and chemical properties of the foaming material.

[0016] The second aspect of the present invention provides a polyurethane foam, which is prepared using the polyurethane foam composition as described in any one of the first aspects above, and the thermal conductivity of the polyurethane foam is 15.5-16.0 mW / m·K and the density is 29.0-30.0 kg / m 3 The polyurethane foam in this technical solution has a good thermal insulation effect and can replace the VIP board added to the side panel or back panel of the existing refrigerator to reduce costs; at the same time, the polyurethane foam has an ultra-low thermal conductivity and low density, which can reduce the conduction of heat and has excellent thermal insulation performance. At the same time, the foam material is light, which is conducive to reducing the weight of the refrigeration equipment.

[0017] The third aspect of the present invention provides a method for preparing a polyurethane foam, which is prepared using the polyurethane foam composition as described in any one of the first aspects above, comprising the following steps:

[0018] Mixing dry white material, LBA foaming agent and low boiling point foaming agent according to weight proportion and adding the mixture into the first premixing tank to obtain mixed white material;

[0019] Put isocyanate into the second premixing tank and stir evenly to obtain prefabricated black material;

[0020] Putting nitrogen or carbon dioxide into a foaming agent premixing tank to obtain a prefabricated foaming agent;

[0021] The mixed white material, the prefabricated black material and the prefabricated foaming aid are mixed according to the weight ratio and then directly injected into the mold, and the polyurethane foam is obtained after curing.

[0022] The preparation method of polyurethane foam provided by the above technical scheme adopts a ternary mixing method for preparation. When in use, the mixed white material, prefabricated black material and foaming aid are mixed by a high-pressure foaming machine and then directly injected into the mold, avoiding the ultra-high pressure requirements of the equipment for pre-mixing of nitrogen or carbon dioxide, reducing the difficulty of operation and the requirements for equipment, making the mixing more sufficient, and the nucleation effect is fully exerted, which is beneficial to further reduce the thermal conductivity of the foam.

[0023] In some embodiments of the third aspect, the pressure difference between the first premixing tank and the second premixing tank is controlled to be less than 0.5 bar. In this solution, the pressure difference between the first premixing tank storing the white material and the second premixing tank storing the black material is controlled to avoid the circulation of the foaming material in the entire pipeline, the mixing of the gun head, and the decrease in the stability of the injection process due to the excessive pressure difference between the two tanks, which may cause safety risks or affect the foaming effect.

[0024] In some embodiments of the third aspect, the mixed white material and the prefabricated black material are prepared at a temperature of 15 to 25° C. and a pressure of 2 to 6 bar, respectively. In this temperature range and pressure range, the prepared mixed white material and prefabricated black material can be more uniform.

[0025] In some embodiments of the third aspect, the temperature of the mold is controlled at 40-50° C., and after curing for 180-300 seconds, polyurethane foam is formed. The appropriate foaming temperature and curing time in this technical solution can ensure that the polyurethane foam forms a stable cross-linked structure, improve the durability and heat insulation effect of the polyurethane foam, improve production efficiency and reduce costs.

[0026] The fourth aspect of the present invention provides a refrigeration device, comprising the polyurethane foam as described in any one of the second aspects above. The polyurethane foam is filled in the box of the refrigeration device, such as the side plate or the back plate, which has good heat insulation and thermal insulation effects and reduces costs. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] A first aspect of an embodiment of the present invention provides a polyurethane foam composition, comprising the following components in parts by weight:

[0029] 100 parts of dry white material, 25-35 parts of LBA foaming agent, 1-2 parts of low boiling point foaming agent, 2-8 parts of foaming aid, 130-174 parts of black material;

[0030] The low-boiling-point foaming agent is a low-boiling-point alkane compound with a boiling point below 0°C; and the foaming aid is nitrogen or carbon dioxide.

[0031] The polyurethane foam composition provided in the above embodiments adopts a foaming system of LBA foaming agent + low boiling point foaming agent + nucleating agent (nitrogen or carbon dioxide), eliminates the methyl formate modifier in the existing system, and adds low-cost nitrogen or carbon dioxide as an auxiliary agent. Nitrogen or carbon dioxide is used in combination with the low boiling point foaming agent to promote each other and synergistically promote the formation of small pore bubble nuclei inside the foaming system, so that the system does not need to increase the amount of foaming agent to obtain a better foaming effect and achieve an ultra-low thermal conductivity. At the same time, nitrogen or carbon dioxide is more environmentally friendly than fluorine-containing nucleating agents, and after being added, it will not have a significant effect on the effects of other components in the system, and other physical and chemical properties have not been significantly deteriorated.

[0032] In addition, it should be noted that in the above embodiments of the present application, a low-boiling point foaming agent and a foaming aid are used in combination in the LBA foaming system. The low-boiling point foaming agent is used as a physical foaming agent, and its vapor pressure is large, which helps to reduce the density of the foam material while maintaining the strength performance unchanged. Nitrogen or carbon dioxide is used as a chemical foaming agent. Under the action of the low-boiling point foaming agent, it can be more fully dissolved in the foaming material, and promote the production of more tiny and uniform bubble nuclei inside the foaming material in the early stage of the reaction, thereby increasing the nucleation rate of the foaming process, increasing the number of pores, reducing the pore diameter, and reducing the radiation conductivity. The low-boiling point foaming agent and the foaming aid interact with each other, making the reduction in thermal conductivity more obvious and at a low cost. Therefore, the present invention develops a LBA foaming agent + low boiling point foaming agent + nucleating agent (nitrogen or carbon dioxide) foaming system, whose production cost is significantly lower than that of the pure LBA system, but the thermal conductivity is about 1mW / m·K better than that of the pure LBA system, which further reduces the lower limit of the thermal conductivity of the existing polyurethane foam. On the basis of the LBA system, a low-cost polyurethane foam with better thermal insulation effect can be obtained, thereby realizing the improvement of the thermal insulation performance of refrigeration equipment at a low cost.

[0033] In some embodiments, the low boiling point foaming agent is n-butane, isobutane, or a mixture of n-butane and isobutane in any proportion. This embodiment defines the specific types of low boiling point foaming agents. N-butane and isobutane exist in the form of gas at room temperature, which helps to form bubbles during the foaming process. Together with the foaming aid nitrogen or dioxide, they promote the formation of bubbles in the foaming system, have good foaming effect and are low in cost.

[0034] In some embodiments, the dry white material includes 89-96 parts of the combined polyether, 2-4 parts of the surfactant, 1-4 parts of the catalyst and 1-3 parts of water. In this embodiment, the dry white material is prepared by mixing the above components, wherein the content of the combined polyether can also be 90, 92, 94, 95, etc., the content of the surfactant can also be 2.5, 3, 3.5, etc., the content of the catalyst can also be 2, 3, etc., and the amount of water added can also be 1.5, 2, 3.5, etc., and those skilled in the art can reasonably select within the above range.

[0035] In some embodiments, the black material is polymerized MDI, and the viscosity of the polymerized MDI at 25°C is 200-400mPa·s, and the isocyanate content is 30-32%. In this embodiment, the black material uses polymerized MDI, and the viscosity of the polymerized MDI is limited, which can ensure the fluidity of the foaming material, improve the uniformity of mixing, and ensure the quality and performance of the final foam; limiting the isocyanate within the above range can form a stable polyurethane network structure and ensure the physical and chemical properties of the foaming material. It is understandable that the viscosity of the polymerized MDI can also be 250mPa·s, 300mPa·s, 350mPa·s, etc., and the isocyanate content can also be 30.5%, 31%, 31.5%, etc., and those skilled in the art can make reasonable choices within the above range.

[0036] A second aspect of the embodiment of the present invention provides a polyurethane foam, which is prepared using the polyurethane foam composition as described in any one of the first aspects above, and the thermal conductivity of the polyurethane foam is 15.5-16.0 mW / m·K and the density is 29.0-30.0 kg / m 3. The polyurethane foam has good thermal insulation effect and can replace the VIP board (vacuum insulation board) added to the side panel or back panel of the existing refrigerator to reduce costs; by adopting the foaming system in this application, the thermal conductivity of the polyurethane foam can be reduced to below 16.0mW / m·K, achieving ultra-low thermal conductivity. At the same time, the density is still maintained at a low level, achieving a polyurethane foam with low density and ultra-low thermal conductivity. It can be understood that the thermal conductivity of the polyurethane foam can also be any value within the above range, for example, 15.6mW / m·K, 15.7mW / m·K, 15.8mW / m·K, 15.9mW / m·K, etc., and the density can also be any value within the above range, for example, 29.2kg / m 3 , 29.5kg / m 3 、29.8kg / m 3 wait.

[0037] A third aspect of the embodiments of the present invention provides a method for preparing a polyurethane foam, which is prepared using the polyurethane foam composition as described in any one of the first aspects above, comprising the following steps:

[0038] The dry white material, the LBA foaming agent and the low boiling point foaming agent are mixed according to the weight ratio and added into the first premixing tank to obtain a mixed white material; specifically, a ternary mixer can be used for mixing;

[0039] Put isocyanate into the second premixing tank and stir evenly to obtain prefabricated black material;

[0040] Putting nitrogen or carbon dioxide into a foaming agent premixing tank by high pressure liquefaction to obtain a prefabricated foaming agent;

[0041] The mixed white material, the prefabricated black material and the prefabricated foaming aid are mixed according to the weight ratio under the pressure of a high-pressure foaming machine and then directly injected into a mold, and the polyurethane foam is obtained after curing.

[0042] Through the preparation method provided by the above embodiment, the white material, black material and foaming aid are pre-mixed and stored in the premixing tank respectively. When in use, the three are mixed by a high-pressure foaming machine and directly injected into the mold for curing and molding to obtain polyurethane foam. In the above process, nitrogen or carbon dioxide as a foaming aid is injected independently, and nitrogen or carbon dioxide is mixed separately at the gun head of the high-pressure foaming agent, avoiding the existing method of pre-storing after mixing with white material or black material before use, thereby effectively avoiding the high requirements for equipment (3.5MPa, 10 times that of ordinary foaming) required by the ultra-high pressure of nitrogen or carbon dioxide in static mixing, and avoiding the occurrence of difficult dissolution and difficult mixing, reducing the difficulty of operation and the requirements for equipment, reducing risks, making the mixing more sufficient, and giving full play to the nucleation effect, which is conducive to further reducing the thermal conductivity of the foam.

[0043] In addition, in the above preparation method, the mold is specifically a box of a refrigeration equipment that needs to be filled with a thermal insulation layer. During the molding process of the refrigeration equipment, the mixed white material, prefabricated black material and foaming aid are directly mixed at the gun tip and injected without mixing in advance, thereby avoiding the risk of high-pressure storage.

[0044] In the above preparation method, the preparation conditions of the mixed white material and the prefabricated black material are 15-25°C and 2-6 bar, under which the white material and the black material are mixed more evenly. It is understood that the temperature can be determined within the above range according to actual conditions, for example, the temperature can also be 18°C, 20°C, 22°C, etc.; the pressure can be determined within the above range according to actual needs, for example, the pressure can also be 3 bar, 4 bar, 5 bar, etc.

[0045] In some embodiments, the pressure difference between the first premixing tank and the second premixing tank is controlled to be less than 0.5 bar. In this solution, the pressure difference between the first premixing tank storing white material and the second premixing tank storing black material is controlled to avoid the circulation of the foaming material in the entire pipeline, the mixing of the gun head and the decrease in the stability of the injection process due to the excessive pressure difference between the two tanks, which may cause safety risks or affect the foaming effect.

[0046] In some embodiments, the gun head pressure of the high-pressure foaming machine is 120-150 bar. Within this pressure range, the prefabricated mixed white material, prefabricated black material and foaming aid are directly mixed using the gun head of the high-pressure foaming machine, avoiding the ultra-high pressure requirement of the equipment for mixing before use, reducing equipment requirements, and at the same time being able to produce smaller and more uniform bubbles, thereby improving the foaming effect.

[0047] In some embodiments, the temperature of the mold is controlled at 40-50° C., and the polyurethane foam is formed after curing for 180-300 seconds. In this embodiment, the box of the refrigeration equipment is used as a mold to provide a suitable foaming temperature for the polyurethane foam material, which can complete the curing within the required time. The suitable foaming temperature and curing time can ensure that the polyurethane foam forms a stable cross-linked structure, improve the durability and heat insulation effect of the polyurethane foam, improve production efficiency and reduce costs.

[0048] A fourth aspect of an embodiment of the present invention provides a refrigeration device, comprising the polyurethane foam described in the second aspect of the present invention. The polyurethane foam is filled in a box of the refrigeration device, such as a side panel or a back panel, to have a good heat insulation and thermal insulation effect. The refrigeration device may be a refrigerator or a freezer.

[0049] In order to more clearly and in detail introduce the polyurethane foam composition, polyurethane foam, preparation method and application thereof provided by the embodiments of the present invention, they will be described below in conjunction with specific embodiments.

[0050] Example 1

[0051] This embodiment provides a low-cost and low-thermal conductivity polyurethane foam composition and a method for preparing polyurethane foam.

[0052] The polyurethane foaming composition comprises, by weight, 100 parts of dry white material, 30 parts of LBA foaming agent, 1 part of low boiling point foaming agent (n-butane), 5 parts of nitrogen, and 150 parts of polymerized MDI.

[0053] The preparation method of polyurethane foam is as follows:

[0054] Step 1: at a temperature of about 25°C and a pressure of 6 bar, the dry white material, LBA foaming agent and low-boiling point foaming agent in the above proportions are mixed through a ternary mixer and added into the first premixing tank to obtain a mixed white material;

[0055] Step 2: at a temperature of about 25°C and a pressure of 6 bar, isocyanate is placed in a second premixing tank and stirred evenly to obtain a prefabricated black material; the pressure difference between the first premixing tank and the second premixing tank is controlled to be less than 0.5 bar;

[0056] Step 3: Put nitrogen into the foaming agent premixing tank by high-pressure liquefaction to obtain a prefabricated foaming agent;

[0057] Step 4: Mix the mixed white material, prefabricated black material and prefabricated foaming aid according to the ratio under a mixing pressure of about 120 bar in a high-pressure foaming machine, and inject them into the refrigerator body; the temperature of the box is controlled at about 45°C, and after curing for about 250 seconds, the polyurethane foam is obtained.

[0058] Example 2

[0059] This embodiment provides a low-cost and low-thermal conductivity polyurethane foam composition and a method for preparing polyurethane foam.

[0060] The polyurethane foaming composition comprises, by weight, 100 parts of dry white material, 30 parts of LBA foaming agent, 1.5 parts of low boiling point foaming agent (isobutane), 5 parts of nitrogen, and 151 parts of polymerized MDI.

[0061] The preparation method is the same as Example 1 except for the raw materials and will not be described in detail.

[0062] Example 3

[0063] This embodiment provides a low-cost and low-thermal conductivity polyurethane foam composition and a method for preparing polyurethane foam.

[0064] The polyurethane foaming composition comprises, by weight: 100 parts of dry white material, 30 parts of LBA foaming agent, 2 parts of low boiling point foaming agent (a mixture of normal butane and isobutane in a ratio of 1:1), 5 parts of carbon dioxide, and 152 parts of polymerized MDI.

[0065] The preparation method is the same as Example 1 except for the raw materials and will not be described in detail.

[0066] Example 4

[0067] This embodiment provides a low-cost and low-thermal conductivity polyurethane foam composition and a method for preparing polyurethane foam.

[0068] The polyurethane foaming composition comprises, by weight: 100 parts of dry white material, 30 parts of LBA foaming agent, 2 parts of low boiling point foaming agent (n-butane), 2 parts of carbon dioxide, and 149 parts of polymerized MDI.

[0069] The preparation method is the same as Example 1 except for the raw materials and will not be described in detail.

[0070] Example 5

[0071] This embodiment provides a low-cost and low-thermal conductivity polyurethane foam composition and a method for preparing polyurethane foam.

[0072] The polyurethane foaming composition comprises, by weight, 100 parts of dry white material, 30 parts of LBA foaming agent, 2 parts of low boiling point foaming agent (n-butane), 8 parts of carbon dioxide and 153 parts of polymerized MDI.

[0073] The preparation method is the same as Example 1 except for the raw materials and will not be described in detail.

[0074] Comparative Example 1

[0075] This comparative example provides a polyurethane foaming composition and a method for preparing polyurethane foam.

[0076] The polyurethane foam material comprises, by weight: 100 parts of dry white material, 30 parts of LBA foaming agent, and 158 parts of polymerized MDI.

[0077] The preparation method is as follows:

[0078] Step 1: At a temperature of about 25°C and a pressure of 6 bar, mix the dry white material and LBA foaming agent in the above proportions and add them into the first premixing tank to obtain a mixed white material;

[0079] Step 2: Adding polymerized MDI into a second premixing tank at a temperature of about 25°C and a pressure of 6 bar to obtain a prefabricated black material;

[0080] Step 3: Control the temperature of the first premixing tank and the second premixing tank to about 25°C, the pressure to about 10 bar, and the pressure difference between the two tanks is less than 0.5 bar;

[0081] Step 4: Mix the prefabricated black material and the mixed white material according to the ratio under a mixing pressure of about 150 bar in a high-pressure foaming machine, and inject them into the refrigerator body; the temperature of the box is controlled at about 45°C, and after curing for about 250 seconds, the polyurethane foam is obtained.

[0082] Comparative Example 2

[0083] This comparative example provides a polyurethane foaming composition and a method for preparing polyurethane foam.

[0084] The polyurethane foam material comprises, by weight: 100 parts of dry white material, 30 parts of LBA foaming agent, 2 parts of foaming aid MFT, and 136 parts of polymerized MDI.

[0085] The preparation method is as follows:

[0086] Step 1: Under the conditions of a temperature of about 25°C and a pressure of about 6 bar, the white material and LBA foaming agent of the above proportions are mixed and added into the first premixing tank to obtain a first mixed white material;

[0087] Step 2: Under the conditions of a temperature of about 15°C and a pressure of about 10 bar, the first mixed white material and the foaming aid MFT are mixed according to a ratio and added into a second premixing tank to obtain a second mixed white material;

[0088] Step 3: Adding polymerized MDI into a third premixing tank at a temperature of about 25°C and a pressure of 6 bar to obtain a prefabricated black material;

[0089] Step 3: Control the temperature of the second premixing tank and the third premixing tank to about 25°C, the pressure to about 10 bar, and the pressure difference between the two tanks is less than 0.5 bar;

[0090] Step 4: Mix the prefabricated black material and the second mixed white material according to the ratio under the mixing pressure of 150 bar in a high-pressure foaming machine, and inject them into the refrigerator body; the temperature of the box is controlled at about 45°C, and after curing for about 250 seconds, the polyurethane foam is obtained.

[0091] Comparative Example 3

[0092] This comparative example provides a polyurethane foaming composition and a method for preparing polyurethane foam.

[0093] The polyurethane foam material comprises, by weight: 100 parts of dry white material, 8 parts of cyclopentane, 5 parts of isopentane, 8 parts of carbon dioxide and 136 parts of polymerized MDI.

[0094] The preparation method is as follows:

[0095] Step 1: Under the conditions of a temperature of about 25° C. and a pressure of about 6 bar, the white material, cyclopentane and isopentane in the above proportions are mixed through a ternary mixer and added into a first premixing tank to obtain a mixed white material;

[0096] Step 2: Under the conditions of a temperature of about 25°C and a pressure of about 6 bar, isocyanate is placed in a second premixing tank and stirred evenly to obtain a prefabricated black material; the pressure difference between the first premixing tank and the second premixing tank is controlled to be less than 0.5 bar;

[0097] Step 3: Putting nitrogen or carbon dioxide into a foaming agent premixing tank by high pressure liquefaction to obtain a prefabricated foaming agent;

[0098] Step 4: Mix the mixed white material, prefabricated black material and prefabricated foaming aid according to the ratio under the mixing pressure of 150 bar in a high-pressure foaming machine, and inject them into the refrigerator body; the temperature of the box is controlled at about 45°C, and after curing for about 250 seconds, the polyurethane foam is obtained.

[0099] Performance Testing

[0100] The above Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to performance tests, and the results are shown in Table 1.

[0101] Table 1 Polyurethane foam performance test results

[0102]

[0103] From the foam test results in the table, the density of the polyurethane foam prepared in Example 5 of the present application was reduced to 29.3 kg / m 3 , the thermal conductivity is reduced to 15.57mw / mk; compared with the pure LBA foaming system of comparative example 1, the density of the polyurethane foam of Example 5 of the present application is reduced by 3.3kg / m 3 , the thermal conductivity decreased by 0.96mw / mk; when the thermal conductivity decreased significantly, the foaming material cost could be reduced by about 10%; compared with the LBA foaming agent plus fluorine-containing nucleating agent system of comparative example 2, the polyurethane foam of Example 5 of the present application had a density decreased by 3.0kg / m 3 , the thermal conductivity decreased by 0.38mw / mk. When the thermal conductivity decreased to a certain extent, since the price of nitrogen or carbon dioxide is much lower than that of fluorine-containing nucleating agent, the cost of foaming material can be reduced by more than 10%, and it is more environmentally friendly. Compared with the pure CP foaming agent plus gas nucleating agent system of comparative example 3, the polyurethane foam of embodiment 5 of the present application has a density decreased by 3.8kg / m 3, the thermal conductivity decreased by 3.96mw / mk, which is a huge decrease in thermal conductivity, and the cost of the foaming material decreased by more than 10%. In addition, the polyurethane foams prepared in Examples 1 to 5 of the present application have reduced costs and thermal conductivity of the foaming material, and at the same time, the deformation rate of the pressure tank, compression strength, dimensional stability and other aspects of the performance have not deteriorated significantly.

Claims

1. A polyurethane foam composition, characterized in that By weight, it includes the following components: Wherein, the low-boiling-point foaming agent is a low-boiling-point alkane compound with a boiling point lower than 0°C; and the foaming aid is nitrogen or carbon dioxide.

2. The polyurethane foam composition according to claim 1, characterized in that The low boiling point foaming agent is n-butane, isobutane or a mixture of n-butane and isobutane in any proportion.

3. The polyurethane foam composition according to claim 1, characterized in that The dry white material comprises 89-96 parts of combined polyether, 2-4 parts of surfactant, 1-4 parts of catalyst and 1-3 parts of water.

4. The polyurethane foam composition according to claim 1, characterized in that The black material is polymerized MDI, the viscosity of the polymerized MDI at 25° C. is 200-400 mPa·s, and the isocyanate content is 30-32%.

5. A polyurethane foam, characterized in that: The polyurethane foam is prepared by using the polyurethane foam composition according to any one of claims 1 to 4, wherein the thermal conductivity of the polyurethane foam is 15.5 to 16.0 mW / m·K and the density is 29.0 to 30.0 kg / m 3 .

6. A method for preparing polyurethane foam, characterized in that: The method is prepared by using the polyurethane foam composition according to any one of claims 1 to 4, comprising the following steps: The dry white material, the LBA foaming agent and the low boiling point foaming agent are mixed according to the weight ratio and added into the first premixing tank to obtain a mixed white material; Put isocyanate into the second premixing tank and stir evenly to obtain prefabricated black material; Putting nitrogen or carbon dioxide into a foaming agent premixing tank to obtain a prefabricated foaming agent; The mixed white material, the prefabricated black material and the prefabricated foaming auxiliary agent are mixed according to the weight ratio and then directly injected into a mold, and the polyurethane foam is obtained after curing.

7. The method for preparing polyurethane foam according to claim 6, characterized in that: The pressure difference between the first premixing tank and the second premixing tank is controlled to be less than 0.5 bar.

8. The method for preparing polyurethane foam according to claim 6, characterized in that: The mixed white material and the prefabricated black material are respectively prepared at a temperature of 15 to 25° C. and a pressure of 2 to 6 bar.

9. The method for preparing polyurethane foam according to claim 6, characterized in that: The temperature of the mold is controlled at 40-50° C., and the polyurethane foam is formed after curing for 180-300 seconds.

10. A refrigeration device, characterized in that: The method comprises the polyurethane foam as claimed in claim 4 or 5.

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